Effect of soil tillage on soybean yelds, cropped on erva-mate interrows

Abstract

Use of annual cropping between rows of erva-mate (Ilex paraguariensis St. Hil.) is an agroforestry system very popular in southern Brazil, and the main work and income for small and medium farmers. The intensity of soil work, tilling it to seed annual crops, raise some doubts about some damage it can cause to erva-mate root system. It is also not so clear the effect of growing some grass or legume species during the winter as soil cover crops. The objectives of this work were: to test the influence of soil working intensity using different soil tillage systems on cropping soybean and to evaluate soil physical and chemical changes. On a clayey red latosol that has been under use for a long period with wheat/soybean succession, in Embrapa Negócios Tecnológicos, in Ponta Grossa disctrict, Paraná state, rows of erva-mate were planted 6 m apart from each other, to allow growing annual crops on the interrow. It was tested seven different species as soil cover crops during the winter in rotation to soybean seeded on five different soil tillage systems: rototilling, animal track plowing, conventional system, subsoiling and no tillage. Soil was sampled at the beginning of the experiment and five years after, both at the maximum soybean flowering. Due to the great occurrence of weeds, problems to apply herbicides and limitations of its use on erva-mate plantation, the greater the intensity of tillage work the higher was soybean yield. Soybean was the most productive on soil tilled with rototiller and with animal pulled plow. On no tillage system, soybean was the most productive following winter grass species used as soil cover crop; this fact enhances the importance of weed control on this area. Important correlation was found among Ca+Mg and Al+H contents and bulk density and total porosity values in soil surface with average soybean yield.