Soybean productivity and response to different agricultural practices in cerrrado soils with different textures / Produtividade de soja e resposta a técnicas de cultivo em solos de cerrado com diferentes texturas

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

In recent years, agriculture has been marked by the advance of soybean production on coarser soils from the cerrado region, considered improper for this activity. This fact gives rise to several questions regarding the sustainability and the technical, economical and environmental viability of soybean production. Additionally, different responses to the applied techniques and in the nutrient and organic matter dynamics are expected in soils and plants. The objectives of this work were to evaluate soybean yield and the agricultural practices adopted for soils with different textural classes; to evaluate the relationship between soils particle size distribution and the nutrient levels and contents in the soil-plant system; to study the relationship between soil chemical characteristics, particle size distribution and use history and compare the liming and fertilization practices currently adopted by soybean farmers and technical consultants with the theoretical recommendations for soils of different textural classes. Three large data bases with information regarding soybean plants and soils with different textures were used (clay content varying of 30 to 840 g kg-1). Graphs and regression equations were used to obtain different relationships with soil texture: crop yield, nutrient level and content in the plants, soil chemical properties, liming and fertilization. In some cases, the effects were separated by textural class: sand, loam, clay and very clayey. Some relationships involved the description of land use history. Farm owners and technical consultants were interviewed in order to compare the agricultural practices currently adopted with the theoretical recommendations. Soybean yields showed an increase trend with increasing clay content. This was true for soils from the sand and clay textural classes whereas for the loam and very clayey soils the yields decreased with increasing clay content. The nutrient levels had varying relationships with soil particle size distribution and soybean yield. The levels and content of P and S in the plants increased with clay content to 426 and 227 and g kg-1, respectively, with posterior decrease. Potassium, Ca and Mg had a significant, positive relationship with clay content and soybean yield, evidencing limitation mainly of K+ and Ca2+ for the soybean cropped on coarser soils. Micronutrients did not limit soybean yields, except for B. In general, soil chemical properties (pH, P, K+, Ca2+, Mg2+, H+Al and organic matter) tend to present higher values with increasing clay content and land use period (years 1, 3 and 5). For sandy soils, no reduction in the initial organic matter content was verified after soybean cultivation. The relationship of soils cation exchange capacity and organic matter level with the clay content followed the potential model, evidencing larger increases for lower clay contents. It was verified that the lime doses which are currently used by farmers to neutralize soil Al3+ and supply Ca2+ and Mg2+ to soybean plants in sandy soils surpass 6 t ha-1, which is higher than the recommended doses. Therefore, liming needs a more adequate management in order to avoid future problems, such as the general alkalinization of the soil profile. The recommended doses of P and K decrease with increasing clay content and are negatively related to productivity. This can be explained by the fact that areas with sandy soils are more recent while the more clayey soils have built a higher nutrient status due to their longer use history. In this work, P and K recommendations depended on soybean productivity. The interviews with land owners revealed some discrepancies between the field practices and the theoretical recommendation, mainly in relation to liming and P and K fertilization. For example, higher doses of lime and P in sandy soils. It is possible to conclude that soybean productivity is independent of soil particle size distribution; climatic conditions and adequate agricultural practices are the determinant factors. Therefore, sandy soils present equivalent productive potential to that observed for clayey soils.

ASSUNTO(S)

plantas e solo fertilizers plants and soils liming nutrição soja correção de solos ciencia do solo adubos e fertlizantes soybean nutrition

ACESSO AO ARTIGO

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