Effects of Seedbed and Wheat Density on Weed Control, Growth and Yield of Wheat

IntroductionWheat (Triticum aestivum L.) is the prominent cereal food grain and major staple food in Iran. However, weed infestation is a major bottleneck to higher wheat productivity, and accounts for more than 48% loss of potential wheat yield. Weeds are omnipresent pests that compete with crops for water, nutrients, space, and light; host pests and diseases; and release allelochemicals into the rhizosphere. The magnitude of weed-related losses, however, depends on the type and density of a particular weed species, its time of emergence, and the duration of interference. Yield losses are most severe when resources are limited and weeds and crops emerge simultaneously. Crop yields decrease with increasing weed competition. A strong relationship exists between the duration of competition and the competition pressure exerted on the crop, which reduces yield. Stale seedbeds are a long-established practice that can be used with supplemental herbicides in conventional systems or without them in organic systems. The aim of the study was assessing the effect of various seedbed and wheat density on weed control, and growth and yield of wheat.Materials and Methods The experiment was conducted in a split plot arrangement based on randomized complete block design with three replications. The seedbed (false, stale and conventional seedbed) were assigned to main plots and wheat density (150, 200 and 250 kg seed ha-1) were randomized in subplot. The spacing between the planting rows was 20 cm. The required fertilizers were applied based on the results of soil analysis and by phosphate di-ammonium (150 kg ha-1) and urea (250 kg ha-1). Also, other planting operations such as irrigation were applied uniformly to all treatments. Weed control was not carried out in growth stages.Results and Discussion The results showed that dry weight and density of weed, plant height, number of tiller, 1000-seed weight, grain yield and seed protein contents were affected by interaction of seedbed and plant density. Simple effect of seedbed and plant density had a significant effect on number of spike and lodging percentage of wheat. Using false and stale seedbeds led to reducing weed density and dry weight, and increasing number of tiller, number of spike, biological and grain yield and protein contents rather than conventional planting conditions, significantly. Increasing plant density had a positive effect on weed control. It seems that increasing wheat density increased the competitiveness of plant species by decreasing access to enough light and nutrients, and led to eliminating the weeds. The highest grain yield (6.95 t ha-1) was assigned to stale seedbed and density of 150 kg seed ha-1. Grain yield in densities of 150 and 250 kg seed ha-1 was higher than density of 250 kg seed ha-1. Conclusions In general, application of false and stale seedbeds with planting 150-200 kg seed ha-1 is recommended.