Long-term effects of lime and phosphogypsum application on tropical no-till soybean–oat–sorghum rotation and soil chemical properties

Abstract

Abstract Root growth, nutrition and crop yield can be affected by soil chemical modifications caused by superficial limestone and phosphogypsum application in a no-till system. Using this approach, this study was conducted in southeastern Brazil, continuing an experiment that has been on-going since 2002 with the objective of evaluating the residual effects of the surface application of lime and phosphogypsum on the soil chemical characteristics and the root growth, nutrition and yield of soybean, black oat and sorghum in a dry winter region cultivated in 2008/2009 and 2009/2010. The experimental design was a randomized block with 4 replications. The treatments were applied in November 2004 and were as follows: original conditions, limestone application (2000 kg ha −1 ), phosphogypsum application (2100 kg ha −1 ), and limestone (2000 kg ha −1 ) + phosphogypsum (2100 kg ha −1 ) application. Superficial liming with or without phosphogypsum reduced the surface and subsurface soil acidity 5 years after application in the no-till system. The movement of Ca 2+ and Mg 2+ from the surface layer into the subsoil over time was evident. The phosphogypsum application associated with liming increased the Ca 2+ levels throughout the soil profile. Liming maintained high levels of Mg 2+ throughout the soil profile with or without phosphogypsum application. The organic matter content increased with liming with or without phosphogypsum, indicating that in the long term, these practices can increase the C accumulation. Phosphogypsum application had a residual effect on the SO 4 -S levels, and high sulphate concentrations were observed in the subsoil after 5 years. Superficial liming improved crop nutrition and, when associated with phosphogypsum, increased Ca absorption by soybean and sorghum, as reflected in the increased yields of these crops.