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Australian Agriculture Assessment 2001 - Nutrient management in Australian agriculture

SUMMARY

Soil fertility

• The phosphorus, sulfur and calcium status of Australia's agricultural soils have been increased from their inherently infertile state, by application of fertilisers and soil ameliorants. Areas of low to marginal phosphorus status still exist in many regions.
• Australia's topsoils are generally well endowed with potassium, calcium and magnesium, but potential deficiencies exists in some regions

Farm gate nutrient balance

• Balances for nitrogen, phosphorus, sulfur and calcium varied from neutral (inputs = exports) through to positive (inputs > exports) in many regions, suggesting that supply is now approaching near-optimal levels, and soil nutrient reserves are not being mined.
• Potassium and magnesium balances were negative (inputs < exports) in most regions, but most Australian soils have good reserves, or potassium fertilisers are being applied where there are deficiencies.
• Negative balances, signifying soil nutrient depletion, existed in major regions of Queensland (all nutrients); the Victorian Wimmera (nitrogen, phosphorus and potassium); and parts of northern New South Wales and the Riverina (phosphorus). To gain a more precise spatial understanding of these findings, further regional scale investigations would be required.
• Highly positive balances often existed in regions where dairying and horticulture co-exist, suggesting improvements in the efficiency of nutrient use are required.

Nutrient management

• Australian agriculture has moved to managing nutrients on a site-specific basis.
• Soil testing increased sharply during the 1990s.
• Nitrogen fixation by pasture and grain legumes continues to be a major supplier of nitrogen to soil—especially in southern Australia.
• Nitrogenous fertiliser use has increased 2.5 times over the last 10 years, with most going on to crops. This has boosted production, but may also increase risks of groundwater pollution on lighter soils and soil acidification.
• In cropping areas, phosphorus fertilisers are now directed to crops, with pastures relying on residual soil phosphorus.
• Regional industry case studies on nutrient use revealed the importance of identifying regions most at risk to depletion and off-site losses of nutrients.
• Adoption of conservation practices (e.g. minimum tillage, stubble retention, green cane harvesting) promote improvements to the physical, chemical and biological condition of agricultural soils.

INTRODUCTION

Most Australian soils are naturally infertile and need extra nutrients to maximise agricultural yields. During Australia's agricultural history, the level of nutrients that most limit yield potential have been progressively built up. After reaching optimum levels, annual inputs are adjusted to meet losses through soil processes (e.g. leaching or immobilisation) and through export of harvested products via the farm gate. Nutrient inputs have also increased as prospective yields have increased. This is attributable to factors such as improved varieties; rotations; fallow moisture retention; irrigation; and better weed, disease and pest control. Additions to the soil include fertilisers (supplying adequate amounts of essential plant nutrients), soil ameliorants (e.g. lime, dolomite and gypsum that chemically and physically improve the soil) and the use of legumes to increase soil nitrogen status.

The introduction of commercial soil and plant testing during the 1970s enabled nutrient management decisions to move from broad district guidelines towards site-specific management.

A knowledge of nutrient balance (i.e. whether inputs are less than or greater than exports) in regional farming systems and assessments of current nutrient status of agricultural soils is useful to help maintain and optimise productivity while remaining benign to the environment (Magdof et al. 1997, SCARM 1998).

These nutrient management decisions are especially important for higher input, intensive systems of land use.

The context for the movement and use of nutrients at a landscape scale has been outlined in the Landscape balances section. This section focuses on nutrient management on farm—specifically fertiliser use and nutrient offtakes harvested in produce. Nutrient status reported here relates to agricultural land use not native ecosystems. It should be noted that nutrient requirements vary significantly between agricultural land uses.

Water quality

Nutrients from diffuse and point sources enrich regional water bodies and coastal estuaries increase the risk of algal blooms and lower water quality. Nitrate contamination of ground waters can occur through leaching, especially on sandier soils (Dillon 1988, Anderson et al. 1998, Pakrou & Dillon 2001). This can affect the quality of domestic and stock water. These processes may pose future problems for rural communities.

Soil acidification

Nitrogenous fertiliser use has more than doubled in the past decade (ABARE 2000). Increased use of ammonium-based nitrogenous fertilisers can accelerate soil acidification (see Soil acidification section). Plants grown on severely acidic soils have stunted root systems, lowering their uptake of water (and hence yield) and increasing the amount of water moving deeper into the soil profile, or laterally down slope (e.g. Ridley et al. 2001). Acidic soils may also contribute to greater soil erosion through decreased ground cover.

Animal health

Nutritional imbalances of livestock pasture and fodder can induce disorders (e.g. hypomagnesaemia), which seriously impact on productivity.

SUMMARY OF METHODS

Soil fertility

The Audit's Australian Soil Testing Inventory was developed through acquiring and merging soil testing data sets from 12 private and public sector agencies operating commercial services for farmer clients. The data cover the years 1990 to 1999 (eastern Australia) and 1989 to 1998 (Western Australia) and were dominated by samples of surface soils (0 - 10 cm and 0 - 15 cm depths of sampling). About 640 000 samples were collated—58% of the samples originated from Western Australian services.

Assessed soil properties included: soil pH_Ca, organic carbon, extractable soil phosphorus, potassium and sulfur, and exchangeable calcium and magnesium. Soil nitrate (0 - 60 cm depth of sampling) and exchangeable calcium and magnesium could only assessed for eastern Australian soils.

The samples were neither randomly collected nor were they derived by stratified sampling. They were geo-referenced to map points—either nearest township (mostly in eastern Australia), cadastral centroids (~50% of South Australian samples), 20 km grid centres (Western Australia) and to accurate map grid coordinates (some data from the Murray Irrigation Area and Tasmania).

Summary statistics for all soil tests—including mean, minimum, maximum, median, standard deviation and rudimental skewness test—were prepared for each township location. Interpolated maps for each soil property were generated as triangular irregular networks for mean soil test values of the geo-referenced map points to provide broad spatial perspective of soil nutrient status in agricultural regions of Australia. The mapping approach assumed that map point mean values were representative of the surrounding region. This is more likely where map points are spaced closely, but more tenuous in regions where sampling points are more sparse—in these situations a threshold of approximately 1960 km² was selected as a cut-off and remaining town locations are shown as points with a standard radius of 25 km. An example of the point distribution and sample density is shown in Figure 3.1.

Decision rules for classifying and mapping soil fertility status were based largely on the Australian Soil Test Interpretation Manual (Peverill et al. 1999). The area in each nutrient class was estimated for each State, with non-agricultural areas being excluded. Reliability will depend on the spatial accuracy of the interpolated maps generated for each soil property.

Regional farm-gate nutrient balance

Spatial and temporal trends for annual 'farm-gate' nutrient balance were estimated for agricultural regions. Data for calculating nutrient balance were aggregated to statistical local areas for the years 1992/93 to 1996/97 in eastern Australia and from 1989/90 to 1996/97 for Western Australia. Nutrient balances were derived for nitrogen, phosphorus, potassium, sulfur, calcium and magnesium.

Components for farm-gate nutrient balance are:

• nutrient inputs; and
• nutrient exports in harvested farm products.

Farm gate nutrient balance for a given statistical local area is the difference between total inputs and total exports (nutrient inputs minus nutrient exports). Balance was calculated as kilograms of nutrient per hectare and mapped to illustrate spatial and temporal trends. Data sets were assembled to derive nutrient balance (Figure 3.2).

Variables on the nutrient input side were:

• nutrients purchased as fertilisers;
• soil conditioners (lime, dolomite and gypsum);
• nitrogen fixed by pastures and grain legumes; and
• nutrients associated with the net movement of fodder across statistical local area boundaries.

Regional data for nutrient from rainfall or irrigation water were unreliable and not used. Nutrient exported in farm products were calculated using the volume of harvested produce and nutrient concentrations in each commodity. Exports included the net transfer of nutrient in livestock across statistical local area boundaries.

Farm-gate nutrient balances can be positive (inputs > exports), negative (inputs < exports) or neutral (negligible difference). A neutral balance is considered a sustainable target, providing nutrient losses are minimal. No account was taken of nutrient recycling (especially important in grazing systems), soil nutrient immobilisation or off-site losses of nutrients for estimates of farm-gate nutrient balance.

Losses of nitrogen and phosphorus (expressed as kg/ha) to regional water bodies are typically small compared with those accounted for within the farm-gate balance equations, but the total loads of nutrients exported (tonnes per year) within catchments may be considerable (see Nutrient loads to Australian rivers and estuaries section). Industry case studies on partial nutrient balance confirm that appreciable nutrient losses are possible in different farming systems.

Interpretation: a consistent negative balance for a specific nutrient indicates that farming systems are progressively depleting soil nutrient reserves, but this does not always infer that these soils will respond to nutrient additions. Rather it may indicate that the soils have a good level of natural fertility, that exceeds the amount of nutrient removed annually in harvested products.

In contrast, a highly positive nutrient balance infers that nutrient efficiencies might be achieved by reducing levels of nutrient addition, that in turn may limit off-site nutrient losses.

ASSESSMENT FINDINGS

Soil testing

The use of soil testing by farmers increased markedly during the 1990s, especially in eastern Australia. Soil testing in Western Australia remained high and steady during the same period. Currently, about 106 000 samples are analysed annually, which equates to about 1 sample/1000 ha in the agricultural zone. This is a most positive signal, indicating that farmers are increasingly using soil testing as an aid for making better nutrient management decisions.

Fertiliser use (nutrient input)

Consumption of nitrogen, phosphorus and potassium fertilisers in Australia have increased in recent years—growth in nitrogen use accelerated more than two and a half times during the 1990s (ABARE 2000). Use of nitrogenous fertilisers now greatly exceeds phosphorus consumption (Figure 3.3). The reasons for this upsurge in nitrogen use is associated with:

• deterioration in legume content of some pastures (Hamblin & Kyneur 1993);
• a growing awareness and promotion that rates of organic nitrogen mineralisation in agricultural soils were not meeting nitrogen demands of intensively cropped rotations or zero tilled soils (Knopke et al. 2000, Angus 2001);
• increased plantings of nitrogen-fertilised canola crops (Angus 2001);
• improved crop rotations and recognition of the benefit break-crops (e.g. canola) provide in cereal rotations for controlling root diseases and nematodes;
• adoption of shorter-stemmed, higher yielding cereal varieties, less prone to lodging and 'haying off';
• introduction of high analysis ammonium phosphate fertilisers from the 1970s and 1980s to cropping regions of southern Australia (replacing traditional superphosphate applications) and increased use of urea in cropping regions; and
• declining protein levels in wheat (identified and widely promoted in 1989), and the introduction of premium prices for higher protein grades of wheat.

Factors affecting fertiliser decisions

Land use and climate have major influence on fertiliser use decisions confirming that:

• trends in the levels of use of fertilisers were consistently lower in more arid, low yielding environments of the cropping zone than in more reliable, higher yielding regions (see Figures 3.4 and 3.5)—decisions on fertiliser use match anticipated returns.
• adverse seasonal conditions experienced in the drought year, 1994, markedly depressed fertiliser use generally during this year and the next year—especially noticeable across dryland cropping regions (see Figures 3.4 for phosphorus).
• sugar cane and horticultural production systems used substantially higher levels of fertiliser nutrients (kg nutrient/ha) than dryland crop and pasture systems. Phosphorus use in dryland cropping areas is directed to the cropping phase. However, fertiliser use on dairy pastures (which are mostly in high rainfall areas or are irrigated) has been increasing—Fertilizer Industry Federation of Australia estimates that 48% of the total value of fertilisers applied to pastures in Australia are now applied on dairy farms.

Other sources of nutrient

Legume nitrogen fixation - a major contributor to nitrogen supply

Most southern Australian farming systems still rely substantially on nitrogen fixation by legumes to replenish soil reserves after cropping cycles and to provide quality livestock feed. Where legumes were grown, the average addition of nitrogen through atmpospheric fixation was westimated to vary from <5 to >300 kg N/ha/year, with areas >100 kg N/ha being common. In southern Australian regions nitrogen fixation contributed over 60% of the total input of nitrogen (figure 3.5).

In tropical and sub tropical regions, addition of nitrogen from legumes was mainly contributed through grain legume crops and was correspondingly lower than for southern Australia

Organic matter needs to be decomposed by soil biota to release nitrogen for use by plants. This means that in the more reliable and productive cropping regions, demand may exceed supply resultiing in a greater relianceon fersiliser.

Soil organic matter

Soil organic matter contributes to the retention and cycling of soil nutrients. Organic carbon reserves (reflecting soil organic matter content) are mainly determined by regional climatic conditions: as rainfall decreases and/or temperature increases, soil organic matter levels decrease, since these climatic factors largely determine inputs and decomposition levels. Nationally, 25% of the land had organic carbon values less than 1% and 25% had values exceeding 2% (Figure 3.6, Table 3.1).

Land management practices can modify soil reserves of organic matter: the reserves are lower in cropping zones (greater soil disturbance) than under permanent pastures and are higher in irrigated soils. Inherently very low levels exist in the drier Mallee soils of southern Australia, where conservation farming practices should continue to be promoted.

Management options for improving soil organic matter status include stubble retention, minimum tillage, green trash blanketing and applications of mill mud (sugar cane), green manuring, growing pastures and maximising water use efficiency (Uren 1991).

Table 3.1 Areas of agricultural land (km²)*in each State** assessed having specified soil organic carbon (%) ranges.

State	< 0.5%	0.5 - 0.75%	0.75 - 1.0%	1 - 1.5%	1.5 - 2%	2 - 4%	> 4%	Total area
Queensland	2	1 883	3 289	44 495	34 045	21 337	657	10 5708
New South Wales	531	12 310	32 943	122 735	64 432	54 054	4 914	281 920
Victoria	1 210	12 255	15 504	19 255	20 394	56 243	16 654	141 516
Tasmania	0	0	1	3	55	8 161	8 977	17 197
South Australia	4 102	14 773	23 599	44 139	19 693	16 481	1 371	124 157
Western Australia (sw)	922	36 351	54 738	61 079	15 764	27 858	4	196 716
Northern Territory	0	0	30	359	83	0	0	472
National	6 767	77 572	130 104	282 065	154 466	184 134	32 577	867 686

* 1 km² =100 ha
** Regional differences in soil organic matter are strongly influenced by climate as well as agricultural farming systems and practices.

Nutrient exports

The amount of nutrient exported each year in agricultural products varies with the nutrient, production levels and with concentration in harvested products. In general, the quantity of each nutrient exported annually from each statistical local area (kg/ha) was: nitrogen >> potassium > phosphorus and calcium > sulfur > magnesium (Figures 3.7, 3.8, 3.9).

Broad observations include:

• Lower nutrient exports occurred in the more arid cropping regions in most States; on the northern slopes of the Great Dividing Range (Victoria); coastal and Tableland regions of New South Wales; the Central Highlands/Southern Midlands of Tasmania; and western parts of the Burdekin basin.

Highest nutrient exports occurred usually from dryland regions of higher productivity and from irrigated areas including:

• Western Australia: western parts of the Great Southern region and parts of the Central wheat belt
• South Australia: Yorke Peninsula, Mid North and the Lower and Mid South East regions
• Victoria: Wimmera (nitrogen and potassium) and northern irrigation areas
• Tasmania: north-western coastal regions
• New South Wales: Riverina (nitrogen, phosphorus, potassium, sulfur and magnesium), South west slopes and North west Slopes and Plains
• Queensland: South eastern Queensland, often extending to the Central Highlands

High calcium exports usually occurred in dairying regions, but were low in most cropping areas, except the south western slopes of New South Wales. High potassium exports existed in regions where sugar cane was produced and high sulfur and magnesium exports were prominent in regions of south eastern Queensland.

Nutrient status and balance

Results on farm gate nutrient balance were grouped broadly into two dominant land use classes (the mixed cropping - livestock zone; and the higher rainfall or more intensive grazing zone). From this some general patterns emerged for each State (Table 3.2). Collectively, these provide both positive and negative signals for future nutrient management in Australia.

Table 3.2 Generalised State assessments of farm gate nutrient balance for two broad land uses within Australia's agricultural zone.

Nutrient	Western Australia		South Australia		Victoria		Tasmania		New South Wales		Queensland*
Grazing
Nitrogen	positive		positive		variable		neutral/	positive	positive/	neutral	negative
Phosphorus	positive/	neutral	neutral/	negative	neutral/	positive	positive		positive/	neutral	negative
Potassium	negative/	positive	negative		positive/	negative	neutral/	positive	neutral/	negative	negative
Sulfur	positive		positive/	neutral	positive/	neutral	positive		positive/	neutral	negative
Calcium	positive		positive		positive		positive		positive		negative
Magnesium	neutral		negative		neutral/	negative	neutral		neutral		negative
Cropping
Nitrogen	positive/	neutral	neutral/	negative	negative		positive		neutral/	positive	negative/	neutral
Phosphorus	neutral/	positive	neutral		negative/	neutral	positive		neutral/	negative	negative
Potassium	negative		negative		negative		neutral		negative		negative
Sulfur	positive/	neutral	neutral/	positive	neutral/	positive	positive		neutral/	positive	negative/	neutral
Calcium	positive		neutral/	positive	positive/	neutral	positive		positive/	neutral	negative/	neutral
Magnesium	negative/	neutral	negative		negative		neutral		negative/	neutral	negative/	neutral

* Atherton Tableland in Queensland had positive nitrogen, phosphorus, potassium and calcium balances.

Nitrogen

Nitrogenous fertiliser was used mainly on crops, sugar cane and in horticulture (Figure 3.10). Negligible amounts were applied to dryland pastures (Figure 3.11), but it was used on irrigated pastures, mainly for dairying and hay/silage production. Legumes contribute in a major way to soil nitrogen reserves (Figure 3.5).

The scale of use of nitrogen and level of its application in the cropping zone appears to have increased (Figure 3.10). Use depends on seasonal rainfall conditions that encourage farmers to apply nitrogen to optimise yields and protein grades in wheat (premiums have been paid for high protein wheat since 1989).

• Nitrogen balances varied from neutral to moderately positive for both grazing and cropping land use systems (Figure 3.12). Negative balances existed in Queensland, the Wimmera, Mallee and north-west regions of Victoria (where low levels of nitrogen fertiliser were used); the north-west Slopes and Plains (New South Wales); and parts of South Australia. These regions also often had low or moderate soil organic matter status (Figure 3.6).
• Positive balances existed in regions where dairying and horticulture and major forms of land use occurred.

DAIRY

Nitrogen, phosphorus and potassium balances for the Victorian Gippsland region

Prepared by J. White (Market Development Agronomist, Canpotex) and C. Gourley (Department of Natural Resources and Environment, Victoria)

Using published data and industry statistics for the Gippsland dairy region of Victoria, partial nutrient balances for nitrogen, phosphorus and potassium were estimated to be positive for a 'typical' dairy farm. This study confirmed the positive farm-gate nutrient balance findings presented for this region of Victoria. It also demonstrated that appreciable quantities of these nutrients are fed as supplementary feeds and are voided as excreta in laneways and dairy sheds.

Industry profile

• In 1998/99, milk production from the Gippsland region was 1881 million litres, (19% of national production) with a gross farm-gate value of $575 million. Ninety-two percent of milk produced in the region is used in the manufacture of value-added dairy products.
• In recent years, milk production has increased by 3.3% annually, with farm herd size and milk production per cow increasing annually by 7.9% and 2.8% respectively. Average milk production per cow is 4600 L. The average stocking rate is 2 cows/ha.
• Average annual rainfall for the region is 630 mm (but in some areas exceeds 1100 mm). Pasture composition is predominantly rye-grass and clover.
• Deteriorating quality of waterways is recognised as a regional problem, and nutrient management on dairy farms is being actively researched.

This case study calculates partial nutrient balance of nitrogen, phosphorus and potassium for a 'typical' dairy farm in the Gippsland region.

Data sources and assumptions

Nutrient inputs

• Nitrogen fixing varies widely with seasonal conditions and pasture composition. For this case study an average value of 80 kg/ha was used (Eckard et al. 2001).
• Fertiliser inputs were 20 kg N/ha and 25 kg P/ha and 30 kg K/ha (regional farm survey, Gourley et al. 1998, Gourley pers. comm.)
• Nutrients accessed in rainfall (Greenhill et al. 1983, Eckard et al. 2001)
• Annual pasture production was estimated as 12 000 kg/ha with a nutrient content of 3.0% nitrogen, 0.3% phosphorus and 3.0% potassium. Pasture utilisation of 65% was assumed.
• 500 kg of grain supplements (containing 1.9% nitrogen, 0.4% phosphorus and 0.4% potassium) and 600 kg of imported hay (containing 2.5% nitrogen, 0.3% phosphorus and 1.7% potassium) were fed annually to each cow.

Nutrient exports and losses

• Milk production was 5000 L/cow, containing 0.6% nitrogen, 0.08% phosphorus and 0.2% potassium.
• Nutrient losses through the transfer of excreta to non-productive areas (yards, laneways and around troughs) were related to the amount of time cows spent in these areas and were estimated at 10% (Hancock 1950).
• Percentage of ingested nutrients voided in dung were estimated as 20% nitrogen, 60% phosphorus and 12% potassium (Davies et al. 1962).
• Percentage of ingested nutrients voided in urine was estimated as 50% nitrogen, no phosphorus and 80% potassium (Davies et al. 1962).
• Losses through ammonia volatilisation were calculated as 15% of the nitrogen in urine and 3% of the nitrogen in dung (Evans et al. 1998).
• Leaching losses were estimated as 30 kg N/ha (Ledgard et al. 2000), no phosphorus and 10 kg K/ha (Carey & Metherell 1999).
• Run-off losses were estimated as 4 kg N/ha, 4 kg P/ha (Dairy Farms Annual Report 1998/99) and 1 kg K/ha (Hosking 1986).

Denitrification losses of nitrogen, and fixation of applied fertiliser phosphorus and potassium were not considered.

Partial nutrient balance (kg/ha)

The partial nutrient balance sheet on an annual per hectare basis is shown in Table 3.3.

• All nutrients were in positive balance.
• Import of supplementary feed represented an appreciable input of nutrients to the dairying system.
• Internal transfer losses of nitrogen and potassium are considerable. On some dairy farms, nutrients from dairy shed effluent are re-applied to pastures, which would lessen the nutrients lost in excreta transfer. However, application of effluent must be undertaken with care to avoid over-application of nutrients to a limited area of the farm.

Implications for industry

• Transfer of nutrients in excreta, or in preserved feed will impact on the distribution of nutrients within the dairy farm system.

• Quantities of nutrients moving due to fixation, leaching, run-off and atmospheric losses are difficult to estimate; and vary markedly with seasonal conditions. They can be appreciable and will impact on nutrient budgets designed for determining maintenance fertiliser requirements for dairy farms and on off-site nutrient leakages.

Table 3.3 Nitrogen, phosphorus and potassium partial balances for a typical Gippsland dairy system expressed as kg nutrient/ha on an annual basis.

Input/loss mechanism	Nitrogen (kg/ha)	Phosphorus (kg/ha)	Potassium (kg/ha)
Inputs
Fertiliser	20	25	30
Rainfall	3	<1	4
Legume nitrogen fixation	80
Supplementary feed	49	7	28
Outputs
Product (milk)	60	8	20
Excreta transfer	20	2	24
Volatilisation	23
Leaching	30	0	10
Run-off	4	4	1
Balance	15	19	7

Phosphorus

Status

Australia has a long history of phosphorus fertiliser application and the phosphorus status of most agricultural soils has been raised (Figure 3.13, Table 3.4).

• 1.4 million hectares of agricultural land (estimate only) still had very low surface soil phosphorus levels (< 10 mg/kg Colwell extractable soil phosphorus). These areas tended to be mainly in the drier regions in each State, where lower input farming is practised and were especially evident in South Australia.
• 24.6 million hectares—across all States—and making up 28% of the land assessed (estimate only), had soils of marginal phosphorus status (10 to 20 mg/kg extractable soil phosphorus).
• 3.2 million hectares had high values (> 80 mg extractable P/kg), located mainly in Queensland, New South Wales and Victoria. Intensive, irrigated agriculture, especially dairying and horticulture are often located in areas with naturally higher fertility status soils. Levels are augmented with fertiliser application.

Balance estimates

Phosphorus applications appear to be directed to the cropping phases of rotations, with many pastures relying on residual soil phosphorus reserves (Figures 3.4, 3.14). Phosphorus fertiliser use on dryland pastures is low (< 5 kg P/ha). It was higher on irrigated pastures. More phosphorus is applied in cropping regions with more reliable rainfall than in the more arid cropping regions (Figure 3.4).

The phosphorus balance was estimated to be either neutral or slightly positive over large areas of the agricultural zone (Figure 3.15).

• Moderate to highly positive balances existed in regions of Victoria and Tasmania, where dairying and horticulture are the main forms of land use. These regions also had mainly moderate to high soil phosphorus status.
• Negative balances occurred in major regions of Queensland, the Wimmera and northern slopes of the Great Dividing Range of Victoria and the Riverina and northern Slopes of New South Wales. In most of these regions, soil phosphorus status was assessed as marginal.

Table 3.4. Estimated areas of land (km²)*having specified Colwell soil phosphorus ranges (mg P/kg)

State	< 10	10 - 20	20 - 30	30 - 40	40 - 80	80 - 150	> 150	Total area
Queensland	2 358	21 768	24 070	21 230	42 326	11 481	2 485	125 718
New South Wales	1 835	61 963	89 469	58 656	65 304	9 003	2 772	289 001
Victoria	219	30 669	47 382	28 597	30 724	3 434	490	141 515
Tasmania	333	1 600	3 842	3 500	6 799	956	157	17 188
South Australia	8 035	49 427	39 154	17 740	9 016	636	137	124 148
Western Australia (sw)	1 183	80 816	94 838	14 028	5 824	4	0	196 703
Northern Territory	0	62	12	18	167	128	87	474
National	13 963	246 305	298 767	143 769	160 170	25 642	6 130	894 747

* 1 km² =100 ha

negative (inputs < exports) l neutral (inputs = exports) l positive (inputs > exports)

INTENSIVE HORTICULTURE

Nitrogen and phosphorus balances for banana plantations in northern Queensland

Prepared by P.W. Moody, Queensland Department of Natural Resources and Mines (Queensland)

Detailed study of nitrogen and phosphorus fluxes in a plant and ratoon banana crops grown in northern Queensland under irrigation showed a positive nitrogen balance (with substantial leaching and gaseous losses of applied nitrogen) and a positive phosphorus balance in the plant crop and a small negative phosphorus balance in the subsequent ratoon crop. New industry guidelines for managing nitrogen and phosphorus inputs are now being actively promoted within the industry (see also banana case study on soil acidification).

This report compares estimates of complete nutrient balance for nitrogen and phosphorus with estimates derived for partial balances (fertiliser inputs minus nutrients removed in harvested bananas)

Industry profile

• Bananas are grown on 6000 ha of the wet tropical coast of north Queensland (annual rainfall is over 3000 mm), and are supplemented during crop growth with either overhead watering systems, or under-tree mini sprinkler or trickle irrigation systems (Daniells 1995).
• With overhead irrigation, nitrogen and potassium fertilisers are side-dressed, generally at 4 - 8 week intervals. For mini-sprinklers or trickle irrigation they are applied through fertigation at intervals ranging from every irrigation (1 - 2 days during hot weather) to once a fortnight (Daniells 1995).
• Phosphorus fertilisers (superphosphates or NPK fertiliser blends) are usually broadcast at six-monthly intervals. Some growers only apply large rates of phosphorus at planting.
• A recent industry survey indicated that average annual levels of nutrient addition were: 519 kg N/ha, 68 kg P/ha and 750 kg K/ha (Daniells 1995).

Experimental details

A 0.1 ha area of contoured bananas grown on a well-drained ferrosol (clay loam) at South Johnstone in northern Queensland was instrumented to intensively monitor and quantify nitrogen and phosphorus fluxes and off-site losses under typical management practices (Moody et al. 1996).

Measurements included:

• nitrogen and phosphorus fertiliser input;
• nitrogen and phosphorus removal in harvested bunches;
• change in soil nitrogen and phosphorus reserves; and
• losses of nitrogen and phosphorus by drainage and runoff in the plant and first ratoon crop.

Fertiliser inputs comprised 238 kg N/ha and 138 kg P/ha to the plant crop and 232 kg N/ha and zero phosphorus to the ratoon crop, which are levels well below industry practice. Fertilisers were side dressed at 6 weekly intervals with irrigation supplied via overhead sprinklers. Nitrogen and phosphorus were applied as urea and triple superphosphate.

Nitrogen balance

Nitrogen balances for the plant and first ratoon crops (Figure 3.16) show:

• The contribution from soil nitrogen reserves was considerable, but about a third of the nitrogen accumulated by the crop
• large leaching losses of nitrogen under both crops
• large gaseous losses of nitrogen (volatilisation and/or denitrification) in the first ratoon crop.

Partial balance estimates indicate the system was in positive (inputs > exports) nitrogen balance (208 kg N/ha in the plant crop and 159 kg N/ha in the first ratoon). However, a considerable amount of this either existed in the crop biomass (and can therefore be recycled to subsequent crops) or was lost through leaching and gaseous losses.

Losses reported are for much lower application levels than are currently practised of (519 kg N/ha) (Daniells 1995). Losses in typical plantations are likely to be considerably higher than those measured in the experiment. A positive (partial) nitrogen balance may indicate potential off-site nitrogen losses through either leaching, runoff, volatilisation or denitrification.

Phosphorus balance

Phosphorus balances for the plant and first ratoon crops (Figure 3.17) indicate:

• an increase in soil phosphorus reserves under the plant crop (indicated as a negative value because the soil is acting as a sink for applied phosphorus) and a decrease under the first ratoon, as the crop utilised the soil phosphorus reserves (indicated as a positive value since now the soil is a phosphorus source).
• a small removal of phosphorus in harvested bananas compared to the quantity of fertiliser applied.

Partial balance estimates indicate a positive balance (inputs > exports) of 135 kg P/ha for the plant crop and a negative balance (inputs < exports) of 6 kg P/ha for the first ratoon. Calculated over both crops, the partial nutrient balance was highly positive.

Current industry practice is to apply an average of 68 kg P/ha to the plant crop and little more phosphorus to the next four ratoon crops (Daniells 1995). For this system, the overall partial balance for phosphorus would still be positive.

The complete balance at the experimental site indicated that phosphorus accumulates in the soil, with negligible losses by leaching (the soil at the experimental site was highly phosphorus sorbing) or run-off (the site was contoured).

Implications for the industry

• The industry is aware of the need to match fertiliser inputs to crop demands. Efficient nitrogen management should employ crop growth monitoring and appropriate fertigation systems. Regular soil testing to monitor soil phosphorus reserves offers the best approach for managing the positive partial balance for phosphorus.

Potassium

Status

Most agricultural soils had adequate to high natural reserves of potassium, with inland soils tending to be higher than coastal soils (Figure 3.18, Table 3.5).

• 0.9 million hectares were considered potentially deficient in potassium (< 80 mg K/kg), occurring mainly on sandier soils in all States.
• 7.7 million hectares were assessed as having marginal potassium status (80 to 120 mg K/kg).

In coastal regions of Victoria, soil potassium reserves appeared to be maintained by regular potassium fertiliser applications

negative (inputs < exports) l neutral (inputs = exports) l positive (inputs > exports)

Balance estimates

Use of potassium fertiliser has continued to increase from a low base (Figure 3.3) and is confined mainly to dairying, horticulture and sugar cane areas (Figures 3.19, 3.20).

Negligible amounts are applied to dryland crops, except in Western Australia where recent research identified potassium deficiency as a major limitation to crop and pasture yield and grain quality. In these regions of Western Australia, potassium balance changed from being negative to neutral or slightly positive as potassium was applied (Figure 3.22).

Potassium has been applied to soils of low potassium status in Queensland and Western Australia. In south-eastern Australia it was also applied to soils of moderate soil potassium status (built up by past potassium applications).

• Estimated potassium balances varied from being moderate to highly negative in regions where no potassium was applied (Figure 3.21). Adequate potassium reserves existed in surface soils in most of these regions (Figure 3.18).
• Neutral potassium balances were confined to coastal regions of New South Wales, the Burdekin basin and more arid cropping regions of New South Wales and southern Queensland (Figure 3.21).

Table 3.5 Estimated areas of land (km²)*assessed having specified extractable soil potassium ranges (mg K/kg).

State	< 40	40 - 80	80 - 120	120 - 200	200 - 400	400 - 600	> 600	Total area
Queensland	61	3 007	10 011	31 023	61 021	10 867	248	116 238
New South Wales	17	478	4 866	39 645	141 204	94 461	8 202	288 871
Victoria	0	91	2 273	32 931	60 975	32 134	13 146	141 548
Tasmania	4	207	924	5 580	9 695	994	98	17 502
South Australia	30	2 069	5 932	14 975	52 601	36 355	12 200	124 163
Western Australia (sw)	0	2 423	53 501	106 012	34 020	768	0	196 725
Northern Territory	47	381	44	0	0	0	0	472
National	159	8 654	77 551	230 166	359 516	175 579	33 894	885 519

* 1 km² = 100 ha

Sulfur

Status

Soils with potentially low sulfur status may occur in South Australia and New South Wales (Figure 3.23), but in these areas substantial sulfur reserves may exist in the subsoil following past applications in superphosphates or gypsum. A surface soil sulfur value of less than 5 mg S/kg may be indicative of sulfur deficiency. Where fertilisers of low sulfur content have replaced traditional applications of superphosphate (containing 10% sulfur) the residual value of soil sulfur should be further examined.

• Large areas of agricultural land had extractable soil sulfur values between 5 and 10 mg S/kg.
• More than 50% of the area assessed had values greater than 10 mg S/kg.
• High sulfate sulfur levels occur in the subsoil (as gypsum accretions) in many semi-arid regions (in which topsoil organic matter and sulfur levels are often low).
• Sulfur inputs also occur through irrigation water and rainfall in coastal areas. Sulfur inputs via rainfall in the inland are low.

negative (inputs < exports) l neutral (inputs = exports) l positive (inputs > exports)

Balance estimate

• Sulfur balances produced for 1995/96 (Figure 3.24) mainly varied from being neutral to moderately or highly positive. Negative balances existed in significant areas of Queensland. These differing balances probably relate to the use of superphosphates and gypsum in many regions of Australia and low use in some Queensland regions.
• Regions with neutral sulfur balance sometimes occurred on soils of low or marginal sulfur status.
• Highly positive balances were usually recorded in dairy and horticultural regions, that also had reasonably high soil sulfur status.

Calcium

Status (eastern Australia)

Agricultural surface soils in eastern Australia have good calcium reserves (Figure 3.25). Some potentially low values occurred along coastal regions of Queensland. Reserves of calcium in agricultural soils of Western Australia are unknown and need to be assessed. However, appreciable amounts of calcium may also be added in irrigation water in some areas (e.g. northern Victoria and South Australia).

Balance estimates

Calcium applied to agricultural land comes from fertilisers (e.g. single superphosphate with 10% calcium and triple superphosphate with approximately 15% calcium) and from the soil conditioners (lime with approximately 34% calcium, dolomite ~25% calcium and gypsum ~20% calcium).

• In 1995/96, calcium balances varied from being neutral through to highly positive across southern Australia (Figure 3.26). This can be linked to superphosphate and soil conditioner use.
• Negative balances existed in significant parts of south-eastern and central Queensland, but in these regions the calcium status of surface soils is adequate to high (Figure 3.25).

negative (inputs < exports) l neutral (inputs = exports) l positive (inputs > exports)

Magnesium

Status (eastern Australia)

Surface soils in agricultural regions of eastern Australia have good magnesium reserves, although levels are lower than those determined for calcium (Figure 3.27). Some potentially low values may exist along coastal regions of Queensland. Reserves of magnesium in agricultural soils of Western Australia need to be evaluated.

Balance estimates

Magnesium applied to agricultural land comes from fertilisers and dolomite (~7.2% magnesium). Fertiliser applications were mainly confined to horticultural enterprises and some dairy areas. Negligible or very low use occurred elsewhere.

• Magnesium balances were mainly either negative or neutral (Figure 3.28). Negative balances were especially noticeable in Queensland, the Riverina and south-west Slopes of New South Wales and parts of South Australia. These areas are highly productive regions, where negligible magnesium fertiliser was applied, but adequate reserves of magnesium exist in surface soils (Figure 3.27).
• Positive balances existed in dairy and horticultural regions of Victoria, Tasmania and New South Wales.

negative (inputs < exports) l neutral (inputs = exports) l positive (inputs > exports)

DRYLAND CROPPING

Nitrogen, potassium, calcium and magnesium balances for dryland cropping systems (Burnett region, Queensland)

Prepared by M.J. Bell, Department of Primary Industries (Queensland) and P.W. Moody, Department of Natural Resources and Mines (Queensland)

Markedly negative partial balances for nitrogen, potassium and magnesium were determined for two cropping rotations commonly used in the inland Burnett region of Queensland. Calcium balances were positive. The depletion of potassium and magnesium was exacerbated by the removal of peanut stubble as hay and by increased frequency of growing high-yielding grain legume crops. Soil testing was recommended to improve fertiliser decisions in this region.

Industry profile

• Dryland cropping occurs over 50 000 ha of predominantly acidic soils in the Inland Burnett region of south-eastern Queensland. The area receives approximately 750 mm rainfall annually, and various summer and winter grain and summer legume crops are grown in rotation. Crops include peanut, soybean, maize, sorghum, wheat, oats and barley.
• Fertilisers are either broadcast (lime or muriate of potash) or band applied below and to the side of the seed at planting. Nitrogen is occasionally side-dressed on grain crops later in seasons where adequate rainfall is anticipated.
• Stubble retention is widely practised, although peanut stubble is occasionally baled for hay. Conventional tillage systems (discs and tined implements) are mainly used, but reduced/zero tillage is becoming increasingly common for crops other than peanuts.

Partial balances

Partial balances are shown for the conventional and intensive rotations over 16 years for nitrogen, potassium, calcium and magnesium in Figure 3.29.

Nitrogen balances were always negative, and particularly where peanut hay was removed (which contains approximately 2% nitrogen and a high proportion of mineral nitrogen).

• The nitrogen balance was less negative in the intensive rotation than the conventional rotation, and mainly resulted from application of nitrogen to the grain crops (wheat and maize). Poor wheat yields in dry seasons resulted in high residual nitrogen.
• Potassium and magnesium balances were also always negative, with hay removal exacerbating the depletion of soil potassium and magnesium reserves. Considerably more potassium was removed from the soil than magnesium. For both nutrients, the intensive rotation resulted in a greater negative balance than the conventional rotation.
• Calcium balance was positive where no hay was removed, because calcium was applied to peanut and soybean as superphosphate or triple superphosphate. Indeed, the calcium balance is actually considerably more positive, since no allowance has been made (Figure 3.29) for applications of lime to correct soil acidification (farmers use approximately 2.5. t/ha every five years).

Effect of crop type and crop yield on partial potassium balance

Farmers generally apply rates of fertiliser sufficient for the 'average' district yield. In good yielding seasons, this may result in under-fertilisation, and a greater reliance on soil nutrient reserves. Because legumes have higher concentrations of nutrients in harvested seed/pods than grain crops, an above average legume crop will decrease soil reserves more than an above average grain crop.

Figure 3.30 indicates the impact of individual grain and legume crop yields on partial potassium balance, with the intercept (i.e. zero partial balance) indicating the yield at which fertiliser input equals harvested product removal. These intercepts are close to the average district yields of individual crops.

Over the period 1983 - 1999, soybean and peanut crops required more potassium than was applied in six out of eight crops, while maize required more potassium than was applied in all crops. However, a greater discrepancy exists between applied fertiliser potassium and potassium removed in good seasons for legumes than grain crops. If the frequency of legume crops in the rotation increased, then an increased potential exists for greater depletion of soil nutrient reserves at the current levels of fertiliser use. Implications of the nutrient balance for the region:

• Potassium and magnesium deficiencies are likely to become increasingly important limitations to productivity because soil reserves are making up the deficit between fertiliser input and crop nutrient removal.
• Increasing legume frequency in rotations is likely to exacerbate the decline in soil potassium and magnesium reserves, particularly when yields are above average.
• Better seasonal weather forecasting is required to allow fertiliser inputs to match crop yield.
• Monitoring soil nutrient reserves by regular soil sampling will allow fertiliser inputs to be adjusted to maintain soil nutrient levels.
• Where potassium balances are negative, subsoil potassium levels are likely to decline. Potassium taken up be plant roots will be transferred to the above-ground parts, and returned to the surface layers of the soil in crop residues.

RICE

A nutrient audit of the Australian rice industry

Prepared by G. Batten, Charles Sturt University, M. Unkovich, Agriculture Victoria, and D.J. Reuter and C. Kirkby, CSIRO Land & Water, with assistance from Jan Hubatka and Susan Ciavarella, Agriculture NSW

In a single year assessment of nutrient balance in the southern New South Wales rice growing region, industry data showed negative nitrogen, phosphorus and potassium balances, and positive sulfur, calcium and magnesium balances. The nitrogen, phosphorus and potassium balances became substantially more negative where rice stubbles were burnt—a standard industry practice.

Industry profile

• The Australian rice industry started in southern New South Wales in 1925 and has shown continued growth in area sown, crop yield and hence total production throughout its history.
• Yields per hectare of rice are amongst the highest in the world. Average yields for Amaroo—the variety grown in the northern Murrumbidgee Irrigation Area—have exceeded 10 t/ha in several years, with individual producer yields as high as 15 t/ha. These high yields result in significant removal of essential plant nutrients.
• Australian farmers produce over one million tonnes of paddy rice each year from about 150 000 ha of land. At present, 10 commercial rice varieties are grown.
• Rice is generally grown in a rice - winter cereal - pasture rotation, where the pasture phase provides an opportunity to increase soil nitrogen reserves through legumes (~50 kg/ha, Peoples et al. 2000). In some areas, (20 % of rice crops) five or more rice crops are grown consecutively. Heavy rice stubbles are usually burnt.
• Nitrogen is applied at levels that optimise grain yield. The largest responses to nitrogenous fertiliser are obtained when the nitrogen is applied just before the crop is planted or immediately before permanent water is applied. Currently, no reliable soil test exists to guide rice growers on how much nitrogen to apply at these times. Applications of nitrogen at the panicle initiation are also used in conjunction with a shoot analysis service.
• Where continuous rice is grown, growers now apply 20 kg P/ha. Yield decreases occur where only 10 kg P/ha is used.

Data sources

• Nutrient inputs and removals were determined for the crop grown in the 1998/1999 season, which achieved an industry average yield of 9.3 t/ha (at 14% moisture content).
• Nutrients applied as fertiliser were calculated from information supplied by rice growers who used the NIR Tissue Testing Service operated by Ricegrowers' Co-operative Limited (Blakeney et al. 1994, Batten et al. 2000). This service is used by over 40% of rice producers.
• Average concentrations of nutrients in irrigation water used for the summers of 1998 and 1999 at the Narranderra regulator and the Sturt Canal offtake were supplied by Murrumbidgee Irrigation Limited, Leeton. The average use of irrigation water was 13.3 ML/ha (data supplied by Murray and Murrumbidgee Irrigation Limited).
• Nutrients in grain and stubble were provided from published data for Australian rice crops (Marr et al. 1995, 1999). Nutrients input in seed were calculated using seeding rate data taken from RiceCheck records for the 1998 - 1999 crop (J. Lacy pers. comm.).
• Losses due to stubble burning were estimated using data summarised by Kirkby (1999).
• Losses of applied nitrogen fertiliser via denitrification and ammonia volatilisation were estimated from Australian research (Bacon & Heenan 1987, Simpson et al. 1988) as 35% of the level of nitrogen applied.

Partial nutrient balances

Balances derived from these data sets are presented in Table 3.6.

Nutrient inputs

• Inputs were mainly derived from fertilisers and nutrient contaminants in irrigation water.
• Nitrogenous fertilisers—applied at a level to optimise yield—were typically 120 kg N/ha in 1998/99.
• Significant loads of sulfur (18 kg S/ha), calcium (25 kg Ca/ha) and magnesium (15 kg Mg/ha) were derived from irrigation water, with lower loads for nitrogen and phosphorus.

Nitrogen gaseous loss estimates

• Calculated as a conservative value of 42 kg N/ha

Nutrient exports

• Quantities of nutrient exported in harvested grain varied from 93 kg N/ha to 2.2 kg Ca/ha. Large amounts of nitrogen, phosphorus, and potassium were removed in grain.
• Where rice stubbles are burnt, large quantities of potassium (97 kg K/ha), nitrogen (57 kg N/ha) and Ca (13.5 kg Ca/ha) are potentially lost. This assumes these nutrient pools are either retained but immobilised or are volatilised (e.g. nitrogen).

Nutrient balance estimates

• Estimates of partial nutrient balances depended on whether rice stubbles are burnt after harvest or retained and incorporated back into the soil.
• Where stubbles were retained, balances for calcium, sulfur and magnesium were positive, but were negative for nitrogen, phosphorus and potassium. The phosphorus status of regional soils is marginal, but the potassium status is adequate.
• Stubble burning had a major impact on nutrient balance, and especially for potassium and nitrogen. The positive balances for sulfur and calcium (under stubble retention) became less positive, the negative balances for the other nutrients became more negative.

Implications for the rice industry

• Nutrient management in the rice region of southern New South Wales needs to be re-examined to ensure long-term maintenance of soil nutrient reserves.
• With the very high yields being achieved and the practice of burning large stubble masses, large quantities of all nutrients are being exported or potentially lost, and therefore soil nutrient reserves are being depleted. This is especially so for nitrogen, phosphorus and potassium.
• Inclusion of pasture or grain legumes in rice rotations is more sustainable than continuous rice rotations.
• Efficient strategies for supplying adequate phosphorus to rice rotations are required.
• Nutrients contained in the high levels of applied irrigation water, should be part of rice farm nutrient budgets.

Table 3.6 Nutrient balances (kg/ha) for rice grown using average industry inputs of irrigation water
(13.3 ML/ha) and fertilisers to produce an average yield of 9.3 tonne grain/ha.

	Nitrogen	Phosphorus	Potassium	Sulfur	Calcium	Magnesium
Inputs
Seed	1.5	0.4	0.5	0.1	0.04	0.16
Fertiliser	120	4.6	0 3	.5	3.6	0
Irrigation water	4.6	0.7	3.9	18	24.5	15.3
Total inputs	126.1	5.7	4.3	21.6	28.1	15.5
Exports/losses
Grain	93	23.1	29.1	7.7	2.2	9.7
Stubble burning	57	2.4	97	5.4	13.5	8
Nitrogen losses	42
Balances
Stubble retained	-9	-17.4	-24.7	13.9	25.9	5.7
Stubble burnt	-66	-19.8	-121.7	8.5	12.4	-2.3

DIRECTIONS FOR NUTRIENT MANAGEMENT

Nutrient management has moved soil fertility beyond the 'build up' phase into a 'maintenance' phase over much of Australia's intensive agricultural region. Site-specific nutrient management now replaces broad district fertiliser guidelines.

Regular applications of superphosphate in the past, particularly in southern Australia, have improved the phosphorus, sulfur (and calcium) status of agricultural lands from their naturally infertile state. Nevertheless, attention now needs to focus on those regions where low or marginal soil nutrient status (e.g. soil phosphorus and potassium), and highly negative balances were broadly identified.

Nitrogen fertiliser applications to crops are now increasing (still augmented by large contributions from nitrogen fixing legumes). Continuing recent trends in nitrogenous fertiliser use must be balanced against increased risks of soil acidification and the potential loss of soil cations (in particular calcium, magnesium and potassium) leached with nitrate. Soil acidification potentially remains an insidious threat to production as Australia's acidifying farming systems and practices have been in place for many years in some regions. Soil acidification is closely linked with soil nutrient status and the management of nutrient supply and soil acidification should seek to be integrated.

Estimated farm-gate nutrient balance for nitrogen, phosphorus, sulfur, and calcium were predominantly neutral or moderately positive, suggesting that nutrient regimes are approaching near-optimal levels in many farming systems (providing nutrient losses are minimal), with the soils not being mined of their valuable nutrient reserves.

Some areas do also have highly negative balances (inputs < exports) causing nutrient depletion or highly positive (inputs > exports) nutrient balances exposing regional water bodies to potential risks of nutrient enrichment (see Nutrient loads to Australian rivers and estuaries section). The four industry-based, regional case studies had value in showing that improvements in nutrient use efficiency are still required in two key areas:

• Quantification of losses of specific nutrients by soil and crop husbandry (e.g. regional case studies on horticulture, dryland cropping and dairy); variable and often high removal of nutrients in harvested crops and stubbles (e.g. regional case study on rice); and the development of farming practices that improve nutrient use efficiency (e.g. case studies on horticulture and dryland cropping).
• The need for decision support systems on nutrient management remains a priority, so that optimal fertiliser use can be achieved. These systems should include estimates of nutrient loss—by soil fixation, gaseous loss, leaching or by overland flow in intensive farming systems (Moody et al. 1996, Nash & Murdock 1997, Fleming & Cox 1998, Ridley et al. 2001). We also need to identify areas at risk to off-farm leakage of nutrients (see Nutrient loads to Australian rivers and estuaries and Appendix 1).

In Queensland and regions such as the Wimmera and Riverina, the largely negative nutrient balances highlight the need for further regional investigation and interpretation. A negative balance, estimated consistently for these regions, indicates soil nutrient reserves are being depleted by current practices. In the longer term, such balances are not sustainable even though in the short term the soils may have adequate or high nutrient reserves. These balances will also become even more negative where substantial nutrient losses occur.

Changes in potassium balance between 1989 - 1996 in Western Australia, demonstrated the benefits that can accrue from detailed regional research and subsequent extension to farmers: again another positive outcome from the past decade.

It is also pleasing to note that the Fertilizer Industry Federation of Australia has published draft guidelines, based on the principles of ISO 14001, for individual commodity sectors to develop their own specific Nutrient Management Codes of Practice (see case study overleaf).

NUTRIENT MANAGEMENT

Advances by the Fertilizer Industry Federation of Australia

The mineral fertiliser industry in Australia is a $2 billion industry supplying over 5 million tonnes of fertiliser products to Australian farmers.

Fertilizer Industry Federation of Australia, Inc. is the industry association representing all of the manufacturers of mineral fertilisers and most importers. Fertilizer Industry Federation of Australia, Inc. members supply over 95% of the fertiliser used in Australia (excluding lime, gypsum and organic fertilisers).

Australian soil fertility manual

Fertilizer Industry Federation of Australia, Inc. commissioned market research among a range of industry stakeholders including farmers, fertiliser retailers and agents, farm advisers and consultants and found a need for better information on the proper use of fertilisers.

As a first step in filling this gap and in conjunction with CSIRO Publishing, the Fertilizer Industry Federation of Australia, Inc. published the Australian Soil Fertility Manual. The manual was released in 1999 and is being used as a basic reference for education and industry training and accreditation programs and for general use by consultants and farm managers. Over four thousand copies have been sold.

Cracking the nutrient code

The fertiliser industry has also recognised the importance of proper nutrient management at farm and catchment level to minimise losses of nutrient off farm. To assist individual industry sectors develop best management practices, the Fertilizer Industry Federation of Australia, Inc. released a draft set of guidelines—Cracking the Nutrient Code—for developing nutrient management codes of practice in May 2001. The guidelines are currently being evaluated by farmer organisations and various industry groups. Final guidelines will be published later in 2001.

The guidelines provide:

• a framework of overlying principles for nutrient management;
• describe a process for developing codes of practice; and
• provide technical information on nutrient management tools.

Input was sourced from specialists in environmental management systems, and the guidelines are developed on the basis of the principles of the International Management Systems Standard ISO 14001.

Investment in research and analytical laboratories

There has been a significant expansion in the adoption of soil testing by farmers over the past decade built on investments in expansion and upgrading of required laboratory and service delivery infrastructure.

Over the past decade Fertilizer Industry Federation of Australia, Inc. members have invested over $13.5 million in new laboratory facilities and in upgrading existing facilities.

To ensure that soil and plant analytical services are competently delivered, approximately 1800 company field staff, fertiliser agent and dealer staff have been trained by the industry in nutrient management. Approximately 600 have been accredited or judged to be competent to provide recommendations on fertiliser use based on soil and plant analysis.

REFERENCES

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