Design and Development of a High-Speed Dibber Drill for Improved Crop Establishment

Abstract

Field sowing is cheaper than transplanting, but the emergence is often erratic. One practical solution to this problem may be to achieve better control of the soil physical environment in the seed zone by an appropriate drilling technique. For example, the use of dibbers to place the seeds in intimate contact with the soil will help ensure optimal use of available soil moisture. Also, by covering each seed with a small quantity of material other than soil, the emerging seedlings may be protected against adverse changes in soil conditions. This hypothesis was first tested with a low-speed fixed spacing drill. When used to sow crisp lettuce this drill gave significant improvements in emergence compared with a conventional coulter drill. These improvements were greatest in the absence of irrigation when an average 77% of the dibbed seeds, covered with a mixture of peak and vermiculite, emerged compared with 36% for the coulter drill. These results led to the development of the second drill described in this paper, which offers both high-speed operation, up to 2 m/s, and variable spacing of successive seeds within the row. Despite achieving improvements in emergence in crisp lettuce, comparable with those recorded with the low-speed drill, initial experiments with a brassica showed that the coulter drill performed very much better (80% emergence compared with 57% for the dibber drill). Later experiments, following modification to the drill to reduce the consolidation of the soil around the seeds, eliminated the depression in emergence. However, further work is required to realize improvements in emergence of brassica comparable with those recorded with lettuce and other crops.