Experiments relating to techniques for direct drilling of seeds into untilled dead turf

Abstract

A method of comparing the design and performance of direct drilling drill coulters in terms of seed response, is described. A triple disc, hoe and an experimental chisel coulter are compared at very low forward speeds using small tillage bins containing undisturbed turf blocks under a maintained moisture stress. Maximum wheat seedling emergence with the chisel coulter assembly was 77% which was significantly greater than hoe and triple disc coulters with 27% and 26% respectively. A repeat experiment confirmed these trends, and a 22·3% comparative decrease in initial soil moisture content was necessary to reduce the performance of the chisel coulter to a similar standard to that of the other two types. Soil moisture measurements, irrigation response and counts of the fate of individual seeds suggested that the nature of the cover over the seed and the moisture retention properties of the groove were the main factors affecting the ability of seeds to germinate and subsequently to emerge. In this respect, the experimental chisel coulter confined most of its ground disturbance to a sub-surface zone, leaving the dead turf mulch substantially intact. This is in contrast to the “V”-shaped grooves created by the triple disc and hoe coulters. All coulters were followed by a special bar covering harrow.