Chemical and physical fertility indicators of a weakly-structured Ultisol after liming and mulching

Abstract

In the humid tropic, chemical and physical soil properties that decrease soil's nutrient availability and increase oxygen deficiency are important as restrictions to crop growth. The objective of this study was to evaluate the relations between plant growth and chemical and physical fertility indicators of an Ultisol developed from sediments of the Itapecuru Formation in Central-Northern state of Maranhão, Brazil. An experiment was established with randomized block design, four replicates, and six treatments: 6.0 Mg ha-1 mulch with or without liming; 3.0 Mg ha-1 mulch with or without liming; bare soil with or without liming. Determinations in the plants included leaf area index, net assimilation rate, and the yield parameters: mean number and weight of ears, 100-kernel weight, harvest index, and total grain yield. Soil determinations consisted of bulk density variations on the surface and at 20 cm, effective porosity evolution after intentional flooding, and alterations in chemical indicators such as cation exchange capacity, bases saturation, organic carbon, and macronutrient contents. Mulching and liming were equivalent with regard to their influence on leaf area yield, but mulching was more important for corn productivity because of its greater effect on net photosynthesis.