Rotylenchulus reniformis POPULATION CONDITIONED BY SOYBEAN PRODUCTION SYSTEMS AND SOIL ATTRIBUTES

A study was conducted to understand the role of different soybean production systems and soil chemical and physical attributes on phytonematode population density in a physical model of production systems. In an area of 28 hectares, the following production systems were established 26 years ago: a) conventional system (CS) - succession of soybeans in summer and oats in winter, and continuous soil preparation with disc harrow; b) no-till system (NTS) - with rotation of summer crops (soybeans and corn) and winter crops (wheat, oats, and fodder radish); c) integrated crop-livestock system (ICLS) - conducted in no-till system and using Urochloa brizantha (cultivar Piatã) pasture, in crop-livestock rotation every two years; d) permanent pasture system (PP) - U. brizantha (cultivar Piatã) with beef cattle. Twenty six years after the systems were installed, soil samples were taken for nematological analysis and analysis of the soil's chemical and physical attributes. The results showed an almost absolute prevalence of the reniform nematode (Rotylenchulus reniformis, Rr) in the area. The PP system had the lowest population (average of 2 Rr/200cc), followed by the ICLS systems (average of 12 to 25 Rr/200cc). The highest population densities were observed in the CS system (1068 Rr/200cc) and the NTS system when soybeans were grown in the last two years before sampling (1361 Rr/200cc). The highest population densities of R. reniformis were associated with higher soil density in the arable layer, higher K and P levels in the soil, and lower organic matter contents.