Soil breaking mechanisms increase the efficiency of phosphorus, potassium and water use in soybean under dry season in a paddy field in southern Brazil

Abstract

In the last 20 years there has been a significant expansion of soybean cultivation in the southern Brazil, reaching almost 2 million ha. A significant amount of this area (~500 thousand ha) has been cultivated in lowlands in rotation with rice. This rotation allows for the reduction of weeds and higher nitrogen availability. However, as rice cultivation is by flooding causes numerous physical changes in the soil that impose limitations on development of rainfed crops. In addition to these limitations, soils in the subtropical regions of southern Brazil have low levels of phosphorus and potassium. The aim of this study was to assess the response of the soybean to different soil-breaking mechanisms and doses of phosphorus and potassium in the Southern Brazil. The treatments consisted of using a subsoiler, scarifier and harrow under doses of phosphorus and potassium in the 2020/21 and 2021/22 crop seasons. In the second crop season under water restriction conditions, the scarifier and the subsoiler increased the soybean grain yield by 46% and 28%, respectively. In the same crop season, on average for the scarifier and subsoiler, an increase in the efficiency of phosphorus use (+ 62%), potassium (+ 20%) and water use (+ 47%) was observed in relation to harrow management. With adequate distribution and volume of rainfall, the breaking mechanism did not influence grain yield in soybean. The response of the soybean in terms of grain yield to phosphorus was higher than that of potassium in Entisol in the average of the two crop seasons. Thus, the use of breaking mechanisms is an important strategy for the adequate development of soybean in rotation with irrigated rice in lowlands.