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Interpretive Summaries:
Soybean fertilization and soil fertility management under crop rotations of southern Maranhao, 1998
Soybean yield in southern Maranhao depends on how long the soil has been under cultivation and amount of rainfall received. In addition, both macronutrient and micronutrient levels in the region are inherently low. In the first few years after land clearing, 1.2 to 1.5 t/ha yields are common because of the failure to account for nutrient uptake by harvested crops. However, farmers performing corrective fertilization commonly harvest yields of 2.4 t/ha even in the first crop year following land clearing. Objectives of this project were to study soybean response to boron (B), Cu, Mn, Zn, and gypsum in soils of the region with various levels of base cation saturation. The researcher also wishes to quantify the effectiveness of fertilizers in correcting micronutrient deficiencies in these soils. Base saturation was varied in the study to determine its effect on micronutrient availability for plants. Preliminary results show no variation in soybean yield in soils with base cation saturation ranging from 30 to 80 percent. Application of fertilizers containing Cu and Zn increased yield, but soybean showed better responses to Zn application in soil with higher base saturation. Corrective fertilization management increases soybean yields and, thus, the opportunity for increased consumption of both P and K. BRAZIL-26B
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