Soil Physical Attributes Affecting Cotton Productivity and Nematode Population in Mato Grosso State, Brazil.

Cotton is an important cash crop to Brazil, which is the fifth world cotton producer with an annual lint yield of about one million tons in 0.6 million hectares planted. Most of the cotton is cultivated in the savannah-like cerrado in an intensive and high-input production system. The State of Mato Grosso is the largest cotton producing State, where at present 70% of Brazilian cotton is grown after the harvest of soybean. The use of state-of-art technologies in soil management, pest control, mechanization and high yielding varieties contributed to the highest world rain fed cotton productivity, reaching up to two tons of lint per hectare. However, despite the increasing use of cotton technology that leads to high production costs, productivity has reaching a plateau at the last years. Therefore, understanding key factors affecting cotton yield is important to adjust or propose new approach in cotton production technologies. The objective of this study was to evaluate the effect of the soil physical attributes on cotton productivity and nematode population density. Clay, silt and sand contents, bulk density, water content, total porosity, penetration resistance and electrical conductivity were determined in 1,779 commercial production planting fields in the cerrado of Mato Grosso. The main nematodes species evaluated were the root-knot nematode (Meloidogyne incognita), the reniform nematode (Rotylenchulus reniformis) and the lesion nematode (Pratylenchus brachyurus) at about 120 days after planting. Cotton productivity decreased as sand content increased and soil penetration resistance (PR) affected negatively the productivity as well. Higher population of M. incognita was found in sandy soils whereas R. reniformis was associated with clayed soils. M. incognita was found in 24% of the studied sites and reached the higher population in soil and root samples. In general, both cotton yield and nematode populations were highly influenced by the soil physical properties.