EuroChem continues the series of spring webinars
How to increase the profitability of agricultural production with the help of mineral nutrition? Nitrogen fertilization is one of the most important agricultural practices necessary for the formation of high yields of high-quality grain. The instructions for their use on winter wheat crops were compiled by EuroChem experts.
Work for productivity and quality
Nitrogen top dressing is the application of fertilizers during the growing season of crops, aimed at increasing the yield and quality of agricultural products. It is carried out to supplement and improve the impact of fertilizers applied to the soil in the main (pre-sowing) period. This agricultural method in the scheme of plant nutrition can be divided into three types: foliar, root and fertigation top dressing.
When root feeding, fertilizers are applied with the expectation that the active substance will be absorbed by the root of the plant. The advantage of this approach is obvious: we can give a sufficiently large number of d.v. per hectare. But there is also a significant disadvantage: root dressing significantly reduces its effectiveness in extreme environmental conditions. In this case, foliar feeding comes to the fore, which allows you to adjust the mineral nutrition and satisfy part of the plant’s need for nutrients.
There are four factors of winter wheat productivity that ultimately determine the final yield: the number of productive stems per hectare, the number of spikelets per spike, the number of grains per spike, and the weight of a thousand grains.
The first top dressing is aimed at stimulating tillering. During this period, the formation of productive stems occurs, and by the middle of tillering, the plants should be fully provided with nitrogen.
The number of spikelets in an ear is laid at the end of tillering. During this period, a second nitrogen fertilization is carried out.
The formation of the number of grains in the spikelet occurs during the growth of the second internode. How effective nitrogen supplements are in the 32nd phase, there is no scientific data. But some farms use this agricultural technique to increase the number of grains in the spikelet.
Mineral nutrition does not affect the fourth factor of productivity – thousand grain weight, but experts recommend foliar nitrogen fertilization during the heading phase to improve the quality of the crop.
The first rule is that nitrogen fertilization should be carried out if the farm plans a yield of more than 30 centners per hectare.
Secondly, it is important to take into account the optimal phases of plant development. Varieties of winter wheat in different phases of the growing season respond differently to nitrogen fertilization. For “bushy” varieties, the first top dressing is priority, for “spike” varieties (with one large ear and several secondary shoots) – the second. But this does not mean at all that the first top dressing is not required for the “spike” ones. The decision must be made depending on the state of the plants when they leave the winter. If it is good, then with a high number of productive stems, there is no need to feed.
The third rule is that top dressing is carried out under optimal weather conditions and sufficient moisture supply.
It is not necessary to carry out nitrogen fertilizing under the following conditions:
- poor development of plants + lack of moisture;
- good tillering;
- high nitrogen content in the soil;
- possible return of severe cold.
When programming yields, limiting factors must be identified. For the southern regions, this is, first of all, a lack of moisture. The transpiration coefficient of winter wheat, depending on the variety, varies from 340 to 690. But at the same time, it can increase significantly if the plant does not receive the optimal amount of balanced basic nutrients: nitrogen, phosphorus and potassium. And vice versa, decrease to the minimum values if the plant is provided with them in sufficient volume.
Should I crush nitrogen fertilizers? There is no consensus on this issue. Some agronomists are confident in the effectiveness of fractional application, while skeptics deny it. In fact, both are right, since the efficiency of fractional application directly depends on climatic conditions. With a large amount of precipitation, fractional top dressing contributes to a significant increase in yield and grain quality. In conditions of poor moisture supply, such an agricultural method will be ineffective.
What to contribute and how much?
The top 5 nitrogen fertilizers in the Russian Federation include: carbamide, ammonium nitrate, KAS-32, nitrogen-limestone fertilizer (NAI) and ammonium sulfate.
When choosing a product for nitrogen fertilization, it is necessary to take into account in what form and in what quantity the product contains nitrogen. This is due to the fact that the absorption of nitrogen by plants directly depends on the ambient temperature. Thus, at t <+10 °C, the ammonium form of nitrogen is predominantly absorbed. At t +5/+8…+15 °C, the nitrate form of nitrogen is absorbed. At t >+15 °C, the amide form is absorbed. In addition, soil acidity is taken into account (with high acidity, the use of AIM is preferable), as well as the sulfur content in the soil (nitrogen sulfate is recommended in case of deficiency).
Ammonium nitrate – 33.4% nitrogen in nitrate and ammonium forms in equal proportions. Excellent for spring top dressing of winter cereals and as a main fertilizer for sunflowers, corn, spring cereals, etc.
In granulated ammonium nitrate (ammonium nitrate fertilizer, ANU), the nitrogen content is slightly lower (33.5%), but it has a number of advantages. Granules are prilled, have increased strength. Wider grip when spreading (+40% to ammonium nitrate). Ideal for early spring application.
AIM – 27% nitrogen in nitrate and ammonium forms in equal proportions + 12% calcium. It is an alloy of ammonium nitrate and limestone. The product is physiologically neutral, pH = 7.0. Suitable for mixing with phosphate and potash fertilizers. It has the same spreading width as ANU, due to which fewer passes of equipment and less costs are required.
The advantage of UAN-32 – 32% nitrogen is contained in three forms: nitrate and ammonium 8% each, amide – 16%. It is a highly effective fertilizer for all types of crops and soil types. It is used as the main fertilizer and as top dressing.
KAS‑32, enriched with sulfur – UAN+S. It contains sulfur in the form of sulfate (3.6%) and has a synergistic effect: not only gives an increase in yield by 5-10%, but also directly affects product quality, increasing the gluten content, oil content and protein content in cereals, soybeans, sunflower.
Urea contains the highest percentage of nitrogen in the amide form – 46%. Excellent for all crops, both for the main application and for top dressing. Ideal as a foliar application from heading to milky ripeness.
nitrogen sulfate – 21% nitrogen in ammonium form + 24% sulfur. Fertilizer is recommended for early spring application.
In spring, ammonium nitrate or ammonium nitrate fertilizer (ANU) is used for a quick start. In arid regions, CAS-32 is recommended. On acidic soils – nitrogen-limestone fertilizer (UAI) and KAS-32. With a lack of sulfur – ammonium sulfate + ammonium nitrate / UAN + S, urea with sulfur. For long-term storage, granular products are suitable – ANU and AIM.
The application dose directly depends on many factors, including application methods, forms and types of fertilizers, and the removal of nutrients. It is very important to take into account the availability of soil nitrogen.
The balance method for determining the application dose takes into account most factors and is concluded in the formula:
DOSE \u003d PM × V – P × C.
Planned yield (YP) is multiplied by the removal of nutrients by crop products (V), and the supply of nutrients in the soil (P) is multiplied by the coefficient of nutrient uptake from the soil (K). The second result is subtracted from the first result of the multiplication. This is the recommended dose of fertilizer application.
In any case, the selection of the product and its dosage for nitrogen fertilization should be carried out on the basis of an agrochemical analysis of the soil. In addition, it is important to take into account the condition of crops, the characteristics of the variety, and especially the reserve of productive moisture in a meter-long soil layer. If moisture availability allows, then to obtain higher yields, the dose of nitrogen can be increased.
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