Abstract
The aim of this study was to determine the interactions between direct drilling opener design specifications and seed groove micro-environments responsible for seed/seedling performance in a wet soil. Three openers the winged, hoe and triple disc were used. In the presence of earthworms and crop residue, the winged opener which created inverted T-shaped groove, together with hoe opener (U-shaped groove) resulted in greater number of seedling emergence, oxygen diffusion rates and earthworm activity than V-shaped groove created by the triple disc opener. ln the absence of earthworms the openers and crop residue had no positive effect on micro-environments around the grooves. A compacted zone adversely affected the seedling performance and earthworm activity around the groove profiles.
INTRODUCTION
Several authors (Baker, 1976; Cholidhry and Baker, 1980) have defined the requirements of serlds and seedlings drilled direct into dry, untilled soils. Direct drilling machinery technology has now been devel-oped in New Zealand and Australia which is able to meet these requirements. Interna-tionally direct drilling is primarily used in dry soils, and early research work on direct drilling was also undertaken on dry soils.
Not much research work has been undertaken in wet soils. Ellis et at (1975) and Lynch et at (1980) highlighted the problem of ratty acid production from de-caying plant residues and the resulting
seedling mortality in the cold saturated soils of the United Kingdom. They reported that applications of substances which neutralised acetic acid and separation of the seed and plant residue, overcame the problem, but they did not identify differences amongst opener designs in terms of their ability to separate the seed from the plant residues.
This paper summarises the results of a series of experiments in which the micro-environmental requirements of barley seed (Horde= vuigarae) drilled direct into a Tokomaru silt loam soil which subsequently became very wet. Attempts to define design criteria for the openers of seed drills were made and the management practices to overcome the problems associated with Wet soils and crop residues are discussed.
