Nutritional imbalance in soy

Since the 2009/10 harvest, soybean crops have been showing symptoms such as wrinkling of the leaf blade, thickening of veins, blackening of leaves, flower and pod abortion, poor grain formation and oversprouting. Among the hypotheses to explain this anomaly is the probable deficiency of potassium.

The recommendation for fertilizing soybean crops is related to the improvement of the soil profile, so that the use of correctives and fertilizers results in the correction of chemical attributes, which allows for an increase gradual supply of nutrients to the soil, as well as maintaining balance nutritional.

The nutritional requirement for nitrogen, phosphorus and potassium presents extraction around 80 kg N; 16 kg P2O5, 38 kg K2O per ton of grain. Because nitrogen is supplied completely Through symbiotic fixation, potassium ends up becoming the most required nutrient by culture during its cycle. The form and time of application and the amount of potassium supplied to the crop becomes extremely important for its good development and production.

Since the 2009/10 harvest, some cases have been observed in soybean crops in which the crop manifests symptoms such as wrinkling of the leaf blade, thickening of veins, blackening of leaves, abortion of flowers and pods, poor grain formation, oversprouting and opening of pods, causing of still unknown origin, being called “Anomaly”.

From the studies carried out so far, on properties in the region, it was found that this “Anomaly” has a positive correlation with disability potassium (K), also leading to symptoms of late blight on the edges of older leaves and compromised grain filling, mainly in the pods in the upper third of the plant, a typical symptom of deficiency of this nutrient.

Figure 1 presents the results of K content in the soil and leaf, from samples collected on two properties in the Chapadões region, collected in the center of reboleiras that showed symptoms and around the reboleiras, in plants considered normal.

Tables 1 and 2 present the results of soil analyzes inside and outside the spots on Property 1 and Property 2, in the region of Chapadões.

The true causal agent of these symptoms is still unknown. “Anomaly” present in soybean cultivation. However, there is a positive correlation with potassium deficiency. Its occurrence presents variability genotypic.

It is worth highlighting the importance of supplying a source of potassium for culture at levels that provide adequate levels of potassium in the soil (Soil clayey (> 30% clay)  K > 100 mg dm-3), (Sandy soil ( 30 mg dm-60) to obtain a good development of the soybean crop and consequently productivity above the desired levels.

Soy (box)

Due to its importance in agribusiness, in area and geographic dispersion, soybean cultivation occupies a prominent position among other cultures. Brazil has the largest area cultivated under conditions tropical and subtropical. Culture is subject to different variability of soil depending on the source material and climatic conditions, which in turn lead to a greater or lesser degree of weathering throughout their formation. That requires different management care to ensure the supply of all nutrients necessary for the development of culture.

Article published in issue 226 of Cultivar Grandes Culturas, March, 2018.