This process, referred to as immobilization, temporarily decreases the amount of available N.
Nitrogen used by microbes becomes temporarily fixed within microbial tissues. To maintain growth, these microbes use soil and fertilize N for their own growth, thus competing with the plant for available N. However, some residues may not contain adequate N to sustain increasing microbial populations. When crop residues are added to the soil, soil microbes utilize the residues as a food source. These deficiencies are often apparent where swaths were located the previous year. Returning large amounts of crop residues, especially cereal residues, or poorly distributing these residues can cause temporary N deficiencies and reduce crop growth and yield. High residue return may result in a temporary nitrogen (N) deficiency due to soil microbial activity. Sulphate-S can be applied pre-plant (broadcast, banded or seed row), topdressed after crop emergence or at seeding. As a result, spring applied elemental S may not supply adequate sulphate to your crop during the growing period in which it is required. The elemental form of S must be oxidized to the sulphate form before it is available to the crop. Ammonium sulphate supplies a readily available form of sulphate. Plants take up S in the sulphate form (SO4=). When soil testing information is not available and the soil is thought to be marginally deficient in S, N and S should be added in a ratio of 7:1 for canola and 10:1 for wheat. The ratio in the soil should always be lower than that required by the plant to ensure adequate N:S ratios in the plant.Ī soil and plant tissue analysis will help identify the need for additional S and the rate required. To obtain the optimal plant N:S ratios, soil N:S ratios should be between 5:1 and 10:1, depending upon the crop grown. N:S balanceĭepending on the crop and its growth stage, optimal nitrogen (N) to sulphur (N:S) ratios range between 7:1 and 15:1. Deficiencies are also noted on soils with a relatively long history of canola or alfalfa production in the rotation. Generally, S deficiencies occur on soils that are coarse textured (sandy), well drained and/or low in organic matter. In canola, the leaves may cup inwards and develop a reddish or pink colouration on the underside of the leaf. Typically, S deficient crops are spindly, later maturing and the younger leaves are pale green to yellow in colour. Critical to growth, S plays a major role in the formation of proteins, enzymes, chlorophyll and effective nodulation. It is often forgotten in the fertility program, yet most crops utilize as much S as phosphorus. Sulphur (S) is considered to be the fourth major nutrient required by plants. NH3 can be a 4R fertilizer for your farm: the Right fertilizer applied at the Right Rate and Right Time – and the Right depth. The soil clay and organic matter will very quickly trap and retain applied NH3, but you still need good soil conditions and closure behind each bander. Common sense must prevail when selecting a depth to set an NH3 applicator. For most soils, an application depth of 8-10 cm is enough to prevent loss. We don’t need to apply NH3 very deep, which is sometimes assumed. This study and others determined that nearly all NH3 is contained within a 5 cm radius from the centre of the application band.įurther work with soil cores by Les Henry and Dale Tomasiewicz confirmed that NH3 bands are contained in soil in a narrow radius in both wet and dry soils. There have been numerous studies to measure depth and movement of NH3 in Western Canada, including the research of Les Henry and Terry Hogg which measured NH3 movement behind farm applicators at rates of 35 to 150 lb N per acre. In the spring, we should be thinking about the Right placement of NH3 in the soil.Ĭonsider that NH3 must be placed in a band beneath the soil – that’s the Right place for any nitrogen fertilizer to avoid loss as a gas or leaching and to protect the nitrogen from ‘immobilization’ by bacteria as last year’s crop residue decays. For NH3 to be a good choice of crop nutrition for a farm, it needs to fit within the parameters of 4R Nutrient Stewardship agronomy – the Right fertilizer applied at the Right rate, at the Right time and at the Right place in the soil. Nutrien Ag Solutions supplies growers with NH3 from many of our locations, primarily in the northern Prairies. Many farms in Western Canada rely on anhydrous ammonia (NH3) fertilizer as the main source of nitrogen for their crops.
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