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Traditionally, malting barley has been grown in Western Australia on paddocks with low fertility but the development of high yielding varieties and a greater emphasis on grain quality means that more attention must now be paid to nutrition.
To grow a successful barley crop, all of the essential nutrients must be available to the crop. In Western Australia, particular attention needs to be paid to nitrogen, potassium, phosphorus, manganese, copper and zinc.
- Farmnote 41/2001: Nutrition in Barley [Expired][PDF 22KB]
Nitrogen is needed for early tiller development of barley and to set up the crop for a high yield potential. Nitrogen is also an essential part of proteins, and largely determines the protein concentration in the grain.
The nitrogen required to grow a successful barley crop must be supplied from the soil or as fertiliser. Nitrogen can only be taken up by plants when it is in an inorganic form (ammonium or nitrate).
In the soil, over 90% of the nitrogen is in an organic form, which is not available to the plant until it is mineralized to inorganic forms. Organic matter varies in its nitrogen content and ease of mineralisation, and this can range from a readily mineralisable recent crop or pasture residue to older, more stable organic matter which is mineralised slowly.
Mineralisation is stimulated by cultivation and continues throughout the growing season, providing a continuous supply of nitrogen, which may or may not satisfy the crop's requirement.
Nitrogen deficiency symptoms are initially seen on older leaves, which turn pale green and the leaf tip a pale yellow. The yellow discolouration progresses down the leaf towards the base, eventually turning a pale brown. The youngest leaves usually remain green.
The amount of nitrogen that a malting barley crop needs to maximize yield and quality will depend on the seasonal conditions, soil type and rotational history of the paddock, as well as the potential yield of the crop.
More nitrogen fertiliser will be required for crops grown in high rainfall years where the yield potential is greater. Unfortunately, a dry finish to the season will limit yield and the additional nitrogen may go into the grain and result in high protein.
Waterlogging events may limit the plants response to nitrogen and its yield.
- Soil Type
Heavy soils, such as loams and clays, naturally have more nitrogen than sandier soils and are less prone to losses from leaching. In fact, heavy soils may be less suitable for growing malting barley as excessive nitrogen from soil and plant residues may increase the grain protein to above 13 per cent, making it unsuitable for the malting grade.
- Rotational History
Sowing into a paddock with a long history of pasture or crop legumes may produce a high yielding barley crop but with high grain protein. This is because the soil nitrogen is available from plant residues throughout the entire growing season. Avoid sowing into soils that have greater than three per cent organic carbon levels.
- Yield Potential
Between 40 and 54 kg of mineral nitrogen is generally needed in the soil for each tonne of barley grain produced.
As the potential yield increases, extra nitrogen will have to be supplied by the soil or extra fertiliser.
High yielding varieties, such as Gairdner and Baudin require more nitrogen to reach their potential and optimum protein level.
Most responses to nitrogenous fertiliser in Western Australia are the result of an increased number of heads per plant and to a lesser extent, grains per head. The response is largely caused by increased tillering, which is determined during early development. Therefore a good supply of nitrogen is needed early in crop growth. To increase yield without increasing protein, apply the nitrogen fertiliser at sowing, separated from the seed, or up to six weeks after sowing. If urea is drilled close to the seed, it can become toxic and reduce plant emergence.
Profitable responses can often be obtained up to 10 weeks after sowing. However, late applications are more likely to result in increased grain protein and screenings to the detriment of malting quality. High yielding, low protein varieties like Gairdner and Baudin may benefit from a split application at 4 weeks and up to 8 weeks after seeding.
Generally, however, the later the application, the lower the yield response and the greater the risk of not getting a payable response. Responses to later applications are generally a result of better survival of tillers which increases the photosynthetic area and green leaf duration.
To discuss crop nutrition and fertiliser application, contact your local fertiliser representative or agronomist or phone Crop Line on 1800 068 107
The Department of Agriculture and TopCrop West offer a number of tools that help with decisions on rates of fertiliser application.
- Right Nitrogen Slide Rule
- Nitrogen Calculator
- Select Your Nitrogen
- Lime and Nutrient Calculator
'Select Your Nitrogen (SYN)' is an excel based spreadsheet which combines the information presented in the 'Right Nitrogen Slide Rule' and the 'Nitrogen Calculator'. Both those tools are slide rule based decision support tools which allow for quick estimates of likely nitrogen requirements. SYN is much more informative. SYN is a decision support tool for quantifying nitrogen availability and crop response. SYN is a weekly time step, simulation model designed to give the user a quantitative feel for how different components of the farming system impact on available nitrogen, grain yield and grain quality (e.g. protein in barley), as well as the dollar returns. The main purpose of SYN is not to recommend a fertiliser rate; rather it is to show the consequences of any possible nitrogen management strategy in any cropping situation.
Contact your District Office for more information on the SYN decision support tool or Dr Bill Bowden, Department of Agriculture and Food, Centre for Cropping Systems, Northam on (08) 9690 2000 or by email: email@example.com.
- Farmnote 28/1995 (Reviewed 1999): Nitrogen fertiliser rates for cereals [Expired]
Phosphorus is essential for the rapid early development of barley roots and seedlings. It is vital for seed formation and a deficiency can reduce both head and grain numbers, which are established early in the development of the crop.
Phosphorus deficiency symptoms usually only occur if the deficiency is severe. The old leaves develop a purple edge, which is more prevalent towards the tip of the leaf. Over time, the purple discolouration extends down the leaf edge and the leaf turns a dark yellow then brown colour.
Soils in south-western Australia were acutely phosphorus deficient when they were newly cleared and regular applications of phosphatic fertiliser were necessary for profitable production. Eventually fertiliser applications built up the soil phosphate levels to the extent that phosphorus deficiency is no longer a major limitation for production on many of our soils.
On most soils in Western Australia, only enough phosphatic fertiliser now needs to be applied to maintain soil phosphorus levels for profitable production.
As a general rule of thumb, apply about 4 kg/ha of P for every tonne of barley yield targeted. Allow extra P on soils that are prone to chemically locking the applied phosphorus, eg. highly calcareous and ironstone soil types.
Phosphate is needed during early growth, so phosphatic fertilisers are drilled with the seed during sowing. An economic response is unlikely if the application is delayed for more than 10 days after sowing.
Regular soil testing is recommended to check and monitor soil phosphorus levels.
- Farmnote 31/96: Choosing phosphate fertilisers for cereals [PDF 48KB]
Until recently sulphur deficiency was rarely diagnosed in barley in Western Australia because of the widespread use of single superphosphate containing 10 to 11 per cent sulphur. However, new cropping trends have caused cases of sulphur deficiency to appear in some cereal crops.
Sulphur deficient plants that are low in nitrogen have pale younger leaves and their growth is retarded and their maturity delayed. Where nitrogen has been applied, the sulphur symptoms appear more severe. The entire plant becomes a lemon yellow colour and the stems become red. The symptoms of nitrogen deficiency are different from sulphur deficiency in that it is the older leaves that are affected first with nitrogen deficiency.
Deficiencies of sulphur are most likely to occur on the deeper sandy soils at the wetter margins of the wheatbelt, in situations where triple super or DAP have been used for several years.
Deficiencies most often occur in the wetter years and they progressively become more severe with successive years when applying fertilisers with a low sulphur content.
Tissue tests can act as a rough guide to diagnosing a sulphur deficiency. Sulphur at 0.2 per cent in younger leaf tissue is the critical level used for many crops, but often the nitrogen to sulphur ratio (N/S) is also a valuable guide. A ratio of greater than 19:1 often indicates a sulphur deficiency.
Applying a sulphur-containing phosphatic fertiliser at a rate that supplies 5 to 10 kg of sulphur per hectare can avoid a sulphur deficiency. These sulphur-containing fertilisers need to be used in rotation with DAP or triple super in a fertiliser strategy.
Potassium is an important nutrient for barley and is required by the plant in similar amounts as for nitrogen. Deficiencies can lead to poor root growth, restricted leaf development, fewer grains per head and smaller grain size affecting both yield and quality. Potassium is an essential nutrient for grain filling and a deficiency can increase the level of screenings and can reduce the tolerance of plants to environmental stresses, such as drought, frost and waterlogging as well as pests and diseases.
Potassium deficient barley is more prone to foliar leaf diseases reducing grain yields. Marginal and deficient concentrations of potassium in plants increases plant susceptibility to foliar leaf diseases by influencing biochemical processes and tissue structure. Potassium deficient plants have higher concentrations of sugars and amino acids, source of energy for many pathogens, compared to plants with adequate potassium. Potassium adequate plants also have stronger cuticles and thicker outer epidermal walls that make it more difficult for conidia to penetrate into the cell. Therefore, potassium functions within the plant have an important role in determining the improved resistance of potassium adequate plants to diseases.
The application of potassium fertiliser has been shown by DAFWA researchers Ross Brennan and Kith Jayasena to significantly reduce the percent leaf area diseased for spot -type net blotch and powdery mildew of barley in barley grown in marginal soil potassium conditions (<50 mg/kg in top 10 cm). The percent leaf area diseased by powdery mildew was also affected by the source of the potassium fertiliser used. The chloride source (KCl) had a greater effect on reducing percent leaf area diseased at low potassium applications (<20 kg K/ha) levels than the sulphate source (K2SO4). As such the chloride source was more effective when powdery mildew is the main disease. For spot type net blotch, there was no difference in effectiveness of the potassium source on reducing disease infection significantly reduced the percent leaf area diseased at the lower amounts (10 and 20 kg K/ha) of K fertiliser applied. Potassium fertiliser had no effect on the percent leaf area diseased by leaf rust in barley. (See: Farmnote 216 Potassium deficient barley is more susceptible to powdery mildew disease)
Crop requirements for potassium change during the growing season. Potassium uptake is low when plants are small and peaks during late vegetative and flowering stages.
Potassium is very mobile in plants. In deficient plants the potassium is redistributed to the new growth so deficiency symptoms first appear in the older leaves.
Potassium is typically seen as a yellowing and browning of the oldest leaves progressing down the margins of the leaf to give an arrow effect. Plants may be stunted or appear drought stressed.
The occurrence of potassium deficiency in crops is determined by soil type, rainfall and cropping practices.
Potassium deficiency is more common on lighter textured soils where there is less clay and organic matter to retain the potassium in the root zone. In sandy soils, the potassium concentration is usually highest in the surface layer. On sand plain soils with a medium to high yield potential, economic responses are likely if the soil test is less than 50 ppm potassium.
On duplex soils, profitable responses have been measured where soil tests were up to 45 ppm. However, surveys of duplex soils have indicated that potassium levels can vary at depth and potassium levels measured in the 0 to 10 cm layer may not accurately indicate the level of potassium at depth.
Rainfall affects a crop's requirement for potassium and the extent of losses from leaching. Where crop production is limited by rainfall, its demand for potassium will be low and a deficiency is unlikely. Sandy soils in high rainfall areas will be the most vulnerable to the leaching of potassium.
As the yield of the crop increases, so does its demand for potassium. The removal of stubble residues and hay also takes away large amounts of potassium from the farming system.
For barley, potassium fertiliser is required when soil test potassium levels are below 50 mg/kg in the top 10 cm.
In medium and high rainfall areas, delay the application of a potassium fertiliser until four weeks after germination when the plants have developed a sufficient root system to take it up. Do not drill with the seed as it will reduce establishment.
In low rainfall areas where the risk of leaching is low, the economic benefit from applying potassium will depend on the expected yield.
Where potassium deficiency is diagnosed within the barley crop, applying 40 to 80 kg/ha of muriate of potash may give an economic yield increase when applied early enough.
A potassium decision support tool (KASM) is now available for use by advisers, consultants and agronomists. Using the power of comparison of situations, the spreadsheet model can address most of the potassium related questions now being asked by Western Australian barley growers. Factors such as time of application, level of application, soil profile distributions, constraints to rooting depth and season can be assessed in terms of short and long term crop responses. KASM is more an educational tool rather than a recipe method of delivering management recommendations for potassium.
Contact Dr Bill Bowden for more information on the 'KASM' potassium decision support tool at the Department of Agriculture and Food, Centre for Cropping Systems, Northam on (08) 9690 2000 or by email: firstname.lastname@example.org.
Page updated: March 2007
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