Allelophatic Effect of Wheat (Triticum aestivum L.) Extract and Residuals on Germination, Growth and Seed Production of Redroot Pigweed (Amaranthus Retroflexus)

One of the sustainable agriculture management components is the allelopathic potential of crops in weed and soil seed bank control. Because of prevalence and importance redroot pigweed in most fields, a factorial experiment with three replicates was conducted to evaluate the effect of wheat extract and residual of different parts in growth stages and different level of wheat on pigweed in field and greenhouse of Agricultural Faculty of Islamic Azad Uniersity, Tabriz branch during 2008-2009. The examined factors were extract and residual of different parts of wheat in 5 levels (residual as 0, 50, 100, 150 and 200 g.m-2 or extract as 1:20, 1:15, 1:10 and 1:5) and residual of different growth stages of wheat in three levels including vegetative, inflorescence and seed filling. Results showed that leaf extract in vegetative and inflorescence stages had the most reduction effect on seedling length, germination percent and root/shoot ratio. Field and greenhouse results indicate that the effect of extract and residual of different parts of wheat decreased significantly plant height, leaf area, root, leaf, stem and shoot dry weight, 1000 kernel weight and seed yield of pigweed. Increasing wheat residuals in soil decreased all characters of pigweed. Decreasing in leaf area, leaf and stem dry weight, 1000 kernel weight and seed yield of pigweed by adding 50 g.m-2 were 25.31, 22.25, 51.13 and 28.03% respectively, comparing with control. Increasing wheat residuals to 200 g per m2 increased these reductions to 53.08, 39.27, 89.68 and 67.38%, respectively. So, stem dry weight and seed yield of pigweed were the most susceptible attributes of pigweed. Seed bank of pigweed decreased from 7 to 68%. as a result of wheat residuals. Residuals of wheat leaf in inflorescence stage had the highest reduction effect on most attributes and especially on soil seed bank. Therefore the wheat allelopathic potential can reduced pigweed population in fields, herbicides over application and environment pollution.