Challenges in nutrition of high-performance soybean plants

Soybean cultivation is the flagship when we talk about Brazilian agribusiness. This culture originates, through the oils extracted from the grains, several products, from the food industry to the manufacture of cosmetics and paints, in addition to also supplying the agricultural market itself with seeds with high productive potential.

Soybean harvest data over the last 5 years has changed a lot. The three largest soybean-producing Brazilian states are Mato Grosso (MT), Paraná (PR) and Rio Grande do Sul (RS), which together represent more than 57% of total soybean production in the country. For these states, average production went from 22,3 million tons in the 2016/17 harvest to 27 million tons in the 2022/23 harvest, an increase of 21% in the survey carried out. Allied to these numbers is the productivity (kg/ha) achieved – in MT and PR productivity increased by 14,3% and 1,4% within the last 5 years, respectively. This represents an average gain of 5 bags/ha from 2017 to 2023.

Among many factors related to technology in the world of agribusiness, new soybean cultivars have been developed in order to achieve higher production ceilings, greater weight of a thousand seeds, high vigor and germination, among other components to achieve champion harvest results. However, achieving surprising results with these cultivars requires that the environment in which they are growing provides all the necessary resources to express this potential. At this point, we can align factors such as agricultural operations, phytosanitary management, climate indices and, most importantly, soil fertility suitable for development.

The crop fertilization recommendation is directly related to the potential response to one or more nutrients and, consequently, is a function of their availability in the soil. In areas with low nutrient availability, in addition to practices related to improving the chemical profile of the soil, doses of fertilizers should be applied that result in a gradual increase in the availability of nutrients in the soil (corrective fertilization). As fertility is built, the criterion for recommending fertilization becomes its maintenance and, for this, it is essential to know the nutritional demand of the crop in terms of grain export potential, a technique called nutrient balance.

In research on fertility management aimed at high soybean productivity, five factors stand out as the main factors for obtaining results above 70 bags/ha: (i) physical impediment of the soil up to 40 cm; (ii) availability of calcium (Ca) and magnesium (Mg) at depth; (iii) potassium (K), boron and copper contents at levels considered medium to high; (iv) adequate phytosanitary management; and (v) planting density appropriate to the cultivar and production system. Note that among the five main factors, three of them refer to soil quality.

Correcting soil acidity with the application of lime every 2 to 3 years also brings calcium (Ca) and magnesium (Mg) into the soil for plant absorption. When applying calcitic limestone, the Ca input into the system is greater than in dolomitic limestone; The choice of limestone will depend on the concentrations of these two elements. For the application of limestone, aiming at a high-performance soybean production system, application is recommended with the objective of reaching 70% base saturation.

It is worth mentioning that in cases where the application exceeds 4 thousand kg/ha, splitting the dose is interesting to avoid chemical imbalance in the soil solution due to “superliming”. Furthermore, products such as agricultural gypsum can help balance the Ca/Mg ratio, with a 4:1 ratio being desirable, depending on the soil texture, in cases where the soil pH is above 5,5 and the sulfur (S) content does not exceed 6,0 mg/dm in the layer from 0 to 20 cm.

Soil potassium (K) content for high-yield soybean cultivation cannot be below 0,35 cmolc/dm. In this case, soybeans cannot be cultivated without corrective and maintenance fertilization, and must be applied in the soybean-winter crop succession, for productivity above 5 thousand kg/ha, 150 to 200 kg of K2O/ha, plus maintenance fertilization. of 80 kg of K2O/ha/year. In the case of a foliar diagnosis, in the leaves of the upper third during the flowering period, for high soybean productivity, it is associated with K levels above 17,1 g/kg.

For high-performance soybean nutrition, it is worth highlighting the importance of maintaining adequate levels of boron (B), copper (Cu) and manganese (Mn). These elements are part of several plant development mechanisms and, mainly, of soybeans. The ideal values ​​in the 0 to 20 cm soil layer are in the range of 0,4; 1,1 and 1,2 mg/dm for B, Cu and Mn, respectively. It is always worth remembering that the most important source of soil micronutrients is via soil organic matter. Maintaining cultivation under a soil conservation system, respecting the premises of direct planting (permanent soil coverage, not disturbing the soil and crop rotation), guarantees the increase/maintenance of organic matter and carbon accumulation in the soil.

As for nitrogen (N), work carried out by the Embrapa team reveals that there are no benefits from adding mineral N, even in high-productivity crops. However, due to the ease in obtaining fertilizer formulas with N, they can be used, as long as it does not exceed a dose of 20 kg/ha of N so as not to increase production costs and not inhibit the activity of N-fixing bacteria. , Bradyrhizobium japonicum, which drastically reduce the formation of nodules with high doses of mineral N.

For high productivity of soybean cultivars and the entire production system, soil fertility is key to achieving these objectives. Carry out soil analysis annually to monitor soil characteristics and always seek quality professional guidance to assist in decision making.

By Keli CS Guera, CGM Agricultural Monitoring

Article published in issue 291 of Cultivar Grandes Culturas Magazine