Seeding depth effects on the performance of wheat and lupin seedlings under no-tillage : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science (Agricultural Machinery) at Massey University

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Massey University
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The effects of seeding depth on the emergence and performance of many crops under a wide range of cultivated soil types and conditions have been well researched. The same effects under a no-tillage system are not nearly so well covered in the literature and the validity of extrapolation of results between different tillage systems has been shown to be dubious at best. A field experiment was undertaken to compare the performance, in terms of various emergence parameters, of wheat (Triticum aestivum cv. Otane) and lupin (Lupinus angustifolius) sown at target depths of 20, 30, 50 and 70 mm into an untilled seedbed. A secondary aim was to assess the yield performance of wheat. The final factor involved was to assess the effect of the addition of disc scrapers to Cross Slot™ openers with respect to accuracy of seed placement. Emergence parameters assessed included total emergence, rates of emergence and time taken to attain both 5% and 95% emergence (of those seedlings that emerged). Results showed that lupin tended to be planted deeper than wheat at any given opener depth setting and that the addition of scrapers had little, if any, effect either on the sowing depth achieved or on the variability of seed placement, by the opener, around the mean. Scrapers appeared to have very little consequential effect on any of the performance parameters measured, under the conditions of this experiment. The emergence parameters showed a reasonable linear response to increasing seeding depth, especially so in the case of lupin. The variability of total wheat emergence, in particular, at different depths was high compared with lupin. Lupin demonstrated a much higher degree of sensitivity than wheat for almost all emergence parameters. The exception to this was for rates of emergence where relative changes with depth were similar for both species. Fertile tiller numbers decreased with increasing depth at all four depths for wheat. However a high degree of variability in the yield data meant that yield was reduced only at the deepest (70mm) seeding depth. Regression analysis of day-of-emergence as a function of seeding depth of a large number of individual seeds indicated that seeding depth accounted directly for approximately half of the factors affecting day-of-emergence of both wheat and lupin seedlings. These results can be used as a basis for specifying design parameters for seed-drills with respect to the accuracy of depth control mechanisms.
Tillage, Technological innovations, Research