Short-term effects of liming on chemical attributes of tropical sandy soil and soybean (Glycine max L.) yield

Lime application is the most appropriate technique to raise soil pH, decrease Al3+ toxicity and increase Ca2+ and Mg2+ contents in acidic tropical and subtropical moist soils. The objective of this research is to evaluate changes in chemical attributes and soybean yield in sandy soil after lime incorporation. The soil was classified as a typical Quartzipsamments cultivated with (Brachiaria decumbens Stapf) pasture, and its degradation state was classified as strong. The experimental design was a randomized block with six replicates and four lime doses (0, 2, 4 and 8 Mg ha-1). The soil in the area was prepared with one plowing and two harrowings, followed by lime application and two more harrowings to incorporate the lime up to 0.2 m depth. The dependent variables analyzed were soybean yield; numbers of pods filled, pods not filled, and total pods and soil pH in water, CaCl2 and KCl. All parameters were measured at depth of 0.0-0.1, 0.1-0.2 and 0.2-0.3 m. The increase of soil pH by the different lime rates were observed just in 0.0-0.1 and 0.1-0.2 m layers. After 6 months no changes in soil pH were observed in subsoil (0.2-0.3 m). With lower H+ and Al3+ activity and higher basic cation availability, soybean yield was also changed. The maximum soybean yield of 2,929 kg ha-1 was observed with 4.6 Mg ha-1 lime application, although pod number per plant remained constant, independent of limestone dose.