Abstract

At the no-tillage system, the surface liming is a good environmental practice, which aims to maintain the physical structure and stocks of carbon in the soil. However, the acidity amelioration is restricted to the surface layer and the use of the gypsum can be an alternative to improve the chemical conditions in subsurface without the soil revolving. The purpose of this experiment was to evaluate the effect of different rates of gypsum, estimated by different methods, in acid soils with application of superficial limestone since the beginning of the implementation of the no-tillage system. The experiment was conduct at a commercial cropping field located at the municipally of Muitos Capões, RS, Southern Brazil in a Red Oxisol. The experiment was conducted in randomized completely blocks design (RCBD), with six treatments and four replications. The treatments consisted of the superficial application of gypsum in the rates: 0, 3100, 6014, 7875, 9750 and 12400 kg ha^-1. At this area, soybean and corn were cultivated and have their productivity evaluated. After 4 and 16 months of the experiment, Ca, Mg and K levels were evaluated at different depths (0-5, 5-10, 10-20, 20-30 and 30-40 cm). The results showed an increase in Ca contents to the depth of 10 cm at 4 months after application and at all depths evaluated at 16 months after their application. The application of gypsum decreases the Mg contents to the depth of 20 cm and of potassium at all the depths after 16 months of their application. The effects on soil chemical properties with increasing rate of applied gypsum resulted in higher maize grain yield. So, agricultural gypsum applied in the soil with surface liming is efficient in improving soil chemical conditions in deeper layers in a no-tillage system.

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