Effects of no-tillage on weed occurrence.
The effects of no-tillage on the occurrence of weeds (Digitaria sanguinalis, Setaria faberi, Eleusine indica, Alopecurus aequalis, Echinochloa crus-galli, Cardamine hirsuta, Lapsana apogonoides, Stellaria alsine, Cyperus rotundus, Artemisia lavandulaefolia, Paspalum distichum, Imperata cylindrica and Alternanthera philoxeroides) was studied in plots sown with cotton, rape, soyabeans, groundnuts or radishes in Hunan, China. The seed number of annual weeds in the 10-20 cm layer following 7 successive years of no-tillage decreased by 80.3% (with a seed germination rate of 0.6%) compared with that in conventional tillage controls (with a seed germination rate of 24.1%). In the no-tillage plots, 90% of weed seeds were distributed in the 0-3 cm layer and resulted in 90-100% occurrence in the 1st year, whereas seeds were fairly evenly distributed in the 0-20 cm layer and resulted in 70-90% occurrence in the control plots. Perennial weeds had an emergence rate of 20 and 0% from the 10 and 15 cm deep layers, resp., following no-tillage, whereas those in conventional tillage plots had an emergence rate of 100% from 10 cm and 55% from 20 cm. Weed seed dispersion rate was also lower in no-tillage compared to conventional tillage.