Effect Of Rapeseed Residue Remaining On The Soil Surface On Non-Chemical Invasive Plants Management In Subsequent Crop Rotations
Changes in the weed seed-bank due to crop production practices are an important determinant of subsequent weed problems. Bio-herbicides can play a major role in non-chemical controlling strategies of invasive plants in fields. Rapeseed (Brassica napus) is cultivated as a spring crop in Iran and redroot pigweed (Amaranthus retroflexus L.) grows along with different field crops, and is a main factor in yield loss of summer crops.In order to study allelopatic effect of rapeseed residue on germination and growth of redroot pigweed an experiment was conducted in laboratory and greenhouse. Studied factors were water extract of above-ground, root and total parts of rapeseed (included distilled water as control) harvested at three growth stages included early stem elongation, blooming and ripening. Results indicated that when the weed seeds were irrigated with aqueous extract of above-ground, root and total parts of rapeseed, its germination rate with reducing value of 15%, 34% and 22% ranged from 4 germination per day to 3.4, 2.6 and 3.1, respectively, as compared with control. Rapeseed harvesting at blooming and ripening stages could reduce germination rate and seedling dry weightof pigweed up to 39% and 21%, respectively, in comparison with control. Pigweed seedling vigor index was 6.5% lower than control, when seeds treated with root extract harvested at ripening stage. It is concluded that remaining of rapeseed residue on the soil as a bioherbicide may decrease herbicide use and negative effect of pigweed in summer plants. These kinds of studies clearly show guidelines for biotechnologists in synthesis of natural herbicides.
Keywords- Bio-Herbicide, Biotechnology, Rapeseed Residue, Redroot Pigweed.