Soybean macronutrient availability and yield as affected by tillage system

ABSTRACT. The effect of tillage system (NT-no tillage; CT-conventional tillage; MT-minimum tillage; and NT/scarification, every three years) on soybean nutrient availability and yield was evaluated on Oxisol after 12 years of cultivation. Soil samples were collected at depths of 0.00-0.05, 0.05-0.10, and 0.10-0.20 m and were analyzed for P, K, Ca, Mg, carbon (C), organic matter (OM), pH value, potential CEC, base saturation (BS%), and number of semiquinone organic radicals. The macronutrient concentration in the leaves and amount accumulated in the plants at the blooming stage were determined, as well as the yield of the two soybean crops. The soil pH value, BS% and K, Ca, and Mg concentrations were not influenced by the tillage system. The soil P and OM in the surface layer, however, were inversely proportional to the intensity of soil preparation. The P content in the soil surface layer under NT was twice as high as that of soil under CT. The P content in the soybean leaves under NT was also higher compared to that in the plants under CT and MT. The number of semiquinone radicals was low in the soil surface layer under NT, indicating a small degree of humification. However, soybean yield was not affected by the tillage system.