Research of sowing by disc coulters in straw soil

Abstract

With the spread of stubble sowing, when it is performed into unploughed or minimally tilled stubble, 8–10 l/ha of fuel is consumed to overcome seeder resistance forces. The major part of the resistance force is made of seeder coulters. The resistance force depends on soil hardness, sowing depth, the amount of straw on the soil surface, number of discs in a coulter and the angle of their positioning in regard to the moving direction. It was established that in dry season the straw left on the soil surface reduced soil hardness in sowing depth from 1400 kPa to 600–700 kPa. In humid loamy soil (humidity 25–27 %) soil hardness depended little on soil tillage and it was 400–700 kPa in sowing depth. Horizontal resistance force of a disc coulter depends both on the amount of straw on the soil surface and its fineness. If coulter positioning angle in regard to the moving direction is increasing from 0o to 10o, resistance force is increasing as well 1.3–1.7 times. The influence of this angle is less if straw is finer. When the soil is covered with 600 g/m2 of straw chopped to the average length of 6 cm, coulter pull increases 1.3 times, if positioning angle in regard to the moving direction is 5o. Vertical resistance force of a disc coulter is 1.3–1.9 times higher than the horizontal one and it reduces the total seeder resistance force. In sowing it is important to give plants the optimum area. However, even distribution of seeds in the soil in stubble sowing technologies is hampered by technological requirements, e.g., distancing straw from seeds, minimal loosening of field surface, etc. When sowing with disc coulters the coefficient of efficient use of field area depend both on coulter parameters (diameter, attack and spread angles) and the permissible divergence of sowing depth. The experimental trials performed while sowing wheat Zentos showed that with a decrease of the coefficient of efficient use of field area yield decreases as well.