Clério Hickmann

Adubação, produtividade e rentabilidade da rotação entre soja e milho em solo com fertilidade construída

The objective of this work was to evaluate the effects of fertilization on P and K levels in soil with improved fertility, and to identify N, P, and K doses needed to provide the greatest profitability in a rotation between soybean and corn in these soils. The experiment was carried out for three harvest seasons, in a farm with high technological investment, in a clayey Oxisol from Cerrado with high fertility. A randomized complete block design was used, in a split-plot arrangement with three replicates. Treatments consisted of 0, 50, 100, and 150% of the recommended rates of NPK on sowing (plots), and of KCl (soybean) and N (corn) at topdressing. Even after three harvests, P (Mehlich-1) contents remained unchanged in the soil without fertilization. Moreover, soybean yield did not decrease in the absence of fertilization. However, corn was more sensible to the reduction of fertilization, with the maximum economic return obtained with 312 kg ha ‑1 of the 10-32-10 fertilizer formulation, and of 263 kg ha ‑1 urea at topdressing. Soils with improved fertility demand adjustments of fertilization management for the efficient use of fertilizers in crops with high technological investment.

Resposta da soja à adubação com zinco em solo com teores acima do nível crítico

O objetivo deste trabalho foi avaliar a resposta da soja a estrategias de adubacao com zinco, em Latossolo com disponibilidade inicial do micronutriente acima do nivel critico. O experimento consistiu em 16 tratamentos com diferentes combinacoes de fontes, doses e formas de aplicacao de Zn. Foram avaliados a produtividade da soja e os teores de Zn no solo, nas folhas e nos graos. A fertilizacao com Zn aumentou a produtividade da soja, mesmo em solo com teor do micronutriente acima do nivel critico. A resposta a adubacao varia de acordo com as estrategias de aplicacao de zinco. Ha indicios de que o nivel critico de Zn no solo deve ser revisto.

Profitability and efficiency of fertilization in a corn/soybean/corn system in a Latosol with improved fertility.

Currently, there are some doubts regarding fertilization dimensioning that aims at a high grain yield in soils with improved fertility in a crop rotation system. Thus, the objective of this study was to evaluate the yield and profitability resulting from different combinations of NPK fertilization and the efficiency of these nutrients in sequential crops of corn/soybean/corn, in a Latosol with improved fertility, in a farm located in the region of Campo das Vertentes, Minas Gerais State, Brazil. Four doses of sowing fertilization and topdressing were compared, corresponding to approximate proportions of 25, 50, 100 and 150 % of the doses usually applied by farmers. Nutrients sources varied according to the inputs used in the farm for each crop. In a soil with improved fertility, corn is more responsive to fertilization than soybean, with higher grain yield gains associated with N and K supply, while P is less limiting. The most profitable nutrients combination for this system involves increasing the amounts of N and K and reducing the amount of P in relation to the standard fertilization employed on the farm, providing a 14.3 % higher profit and higher average nutrient use efficiency.

Soybean Yield Responses to Micronutrient Fertilizers

The availability of commercial products containing micronutrients for the management of crops has increased in recent years, but there are experimental results showing great variability in response to their application. A literature review was made in 28 scientific articles about the answers in the soybean yield in Brazilian agriculture due to the application of fertilizer containing micronutrients. Then, the aim of this chapter is to approach the efficiency of sources, doses, application methods, time, and yield results achieved in recent years by Brazilian research with the application of micronutrients in soybean. Adequate doses and sources of micronutrient increase Brazilian soybean yield, especially in that soil with low micronutrient content. High yields can be obtained in soils that have micronutrient levels considered adequate or high without their application. To right choice of micronutrients fertilizers, the farmer must know about solubility and other characteristics, including easiness to handling and applying and price. In general, the application method does not result in differences in soybean productivity. Thus, when applying micronutrients in the soil, topdressing or seed furrow, and leaf, and seed treatment, the most important aspects seem to be the time and dose to provide the nutrients in adequate amounts the plant requires.