The area cultivated with wheat (Triticum aestivum) has increased in the southern region of the country, becoming a viable alternative in grain production in many properties. In the pre-sowing management of wheat, it is necessary to observe the technical instructions, which provide important information on the care and management of fertilization in the crop. Proper fertilization is essential to obtain satisfactory products in the harvest. Several forms of agricultural fertilizers are available on the market, especially nitrogenous ones, which are commonly used in grasses.
Nitrogen
The management and conservation of the soil before planting wheat can reduce the need for nitrogen fertilizers, also providing a lower production cost. The use of green manures is an old practice, but it has been gaining ground in Brazil. It consists of the use of plants that provide greater fixation of atmospheric nitrogen —legumes such as vetches (Vicia sativa) are commonly used. It is a strategy similar to cover crops, however, its purpose is to provide the release of this nitrogen more quickly to the soil, making it available for the crop in succession.
Nitrogen (N) has a direct influence on the yield of grasses, because it is one of the nutrients most exported by plants and acts in several metabolic processes, mainly the biosynthesis of protein and chlorophyll. In wheat, nitrogen is the nutrient most demanded, and the adequate supply of the need for nitrogen fertilizers is a very safe management practice in relation to the economic return.
Most effective doses
The doses of nitrogen used in the pre-planting of wheat may vary according to the previous crop, due to the carbon/nitrogen (C/N) ratio. Grasses that have a high C/N ratio have the slowest rate of decomposition compared to legumes. Because of this, the release of nitrogen by the decomposition of organic residues directly influences the dosage of fertilizers for succeeding crops.
Based on what has been mentioned, studies point out that wheat requires around 60 kg to 120 kg of N/ha and should be applied between 15 and 20 N/ha at sowing and the rest in cover, between the elongation and tillering stages. In general, the dose in nitrogen fertilization varies depending on the organic matter content, the previous crop, the region and the expected yield (Antunes, 2017).
N management in wheat is carried out at sowing and also with split applications of nitrogen fertilizer during the phenological cycle of the wheat crop. Research has shown that N use efficiency ranges between 12 and 21 kilograms of grain for each kilogram of N added, however, this will only be possible if the physical, chemical and biological characteristics of the soil are adequate (Antunes, 2017).
Fertilization and productivity expectation
Fertilization determines several components of crop yield, reflecting on increased productivity. With regard to the amount of fertilizers and correctives to be applied to the soil, this is an important factor when thinking about the cost of the crop, since fertilizers have a greater participation in wheat production costs, representing approximately 25 % of investment in farming.
In pre-planting fertilization, it is common to apply mineral phosphate fertilizers in granulated or powdered form, according to the analysis of the soil in the area. It is also necessary to take into account nutrient extraction by crops and maintenance fertilization. Soil chemical analyzes for fertility diagnosis should preferably be carried out every two years.
precision agriculture
Carrying out soil analysis and improving the management of available resources in the agricultural production system, through technological solutions, allows improving the sustainability of wheat production. We can cite as tools the use of cover crops as sources of nitrogen and the variable rate distribution of fertilizers and seeds. These technologies within the production system allow fertilization to be fully carried out in the pre-planting period, meeting existing demands and ensuring greater yield and productivity expectations during the harvest.
