Soybean RESPONSE to LIME and Micronutrients Application IN Argentinean Molisols.

Soybean crop production in Argentina has been significantly increased in the last years; this increase was consequence of better management practices which included phosphorous fertilization and, occasionally, sulfur fertilization. Commonly used rates, however, are not sufficient to balance nutrients export in grain. This situation is particularly negative for meso (Ca and Mg) and micronutrient (Co, Mo, Fe, Zn, Cu, and B) because they are not normally applied by farmers. The objective of this study was to determine the effect of meso and micronutrient fertilization during three growing seasons on no-till soybean. The experiments were factorial combinations of lime (with and without) and micronutrients fertilization (Co, Mo, Fe, Zn, and Cu). At all growing seasons, soil pH (water 1:2.5) and soil concentration of Ca and Mg were measured at 0-20 cm depth. Lime requirement was calculated as 80% of base saturation in the cation exchange capacity. The rate of lime applied (Ca 24%, Mg 9.2%) was 6.2 Tn ha^-1 in 2006-07, 5.3 Tn ha^-1 in 2007/08, and 4.6 Tn ha^-1 in 2009-10 growing seasons. Lime application significantly increased soil pH and Ca and Mg concentration in soil in 2007-08 and 2009-10 growing seasons. As an average of these two growing seasons, the relative increments (%) due to lime application were 7.4, 18.8, and 38.4 for pH, Ca and Mg, respectively. In 2006-07 grain yield was not affected by lime application or micronutrient fertilization, whereas in 2007-08 and 2009-10 lime applications significantly increased grain yield (P≤0.05) and micronutrient application increased grain yield ((P≤0.05) only in the 2009-10 growing season. The average lime response of the two responsive seasons was 260 kg ha-1, whereas the micronutrient response in 2009-10 was 270 kg ha^-1. These results show that pH and non-conventional nutrients would limit soybean grain yield in intensively cultivated soils.