Response of Hard Red Winter Wheat to Seed Density and Seeding Rate in No-Till

Abstract

Defining the optimum seeding rate for wheat (Triticum aestivum L.) is complex because this crop has the capacity to create and abort tillers in response to environmental conditions Several soil physical characteristics affecting germination and emergence are altered with the change from conventional tillage (CT) to no-till (NT), and these may influence final stand. The objective of this study was to determine whether either seed density or seeding rate influenced the performance of hard red winter wheat (HRWW) in a rainfed wheat-fallow rotation under NT. Experiments were conducted during four growing seasons on a Keith silt loam soil (fine silty, mixed. mesic Aridic Argiustoll) in northwestern Kansas. The experimental design was a randomized complete block with four replications. Experimental variables were seed density and seeding rate in a complete factorial arrangement with four levels of seed density and three of seeding rate for a total of 12 treatments. Seed weights ranging from 27 to 35 g/1000 kernels (58-63 Ib/bu) were obtained from bin-run, foundation-grade, 'Newton' seed selectively processed in multiple runs over a gravity table. This process separates seed on the basis of seed density (mass per unit volume), which is then converted into thousand-kernel and test weights. Hence, these units of measure were used in this report. Seeding rates were 450 000, 600 000, and 750 000 viable seeds/acre. Seeding was done with a shop-fabricated drill that allowed seed placement as deep as necessary to reach moisture, while maintaining a constant covering depth of 1.5 in. Heavier seed produced greater numbers of seedlings per unit area and a higher emergence percentage than light seed, but seed density had little effect on the final number of spikes per unit area, ratio of spikes per plant, or kernels per head. Increasing seeding rate resulted in more seedlings and spikes per unit area but decreasing numbers of kernels per head. Overall, responses were compensating, so that grain yield was unaffected by either seed density or seeding rate. Although test weight, protein concentration, and thousand-kernel weight were influenced positively by seeding rate and seed quality, the responses were small and probably of little practical value. Results suggest that the HRWW plant can adapt as effectively under NT as has been reported for CT. Because future emergence conditions are unknown, large heavy seed still should be preferred over small light seed, particularly if seed costs are the same or the latter has been in storage for more than one season.