Volume 6, Issue 1 (1-2004)
Abstract
Field experiment was conducted at the agricultural experiment station of Shiraz Uni-versity at Kushkak in 1996 to quantify the competitive ability of pinto beans (Phaselus vulgaris L. var. Daneshjou) with a naturally occurring population of weeds. An attempt was made to increase the competitive ability of the plants by altering row and plant spac-ings. An uncontrolled population of weeds reduced pinto bean yields by 75%. The ability of plants to reduce weed dry weight was further enhanced in medium and narrow rows compared to wide rows. Row and plant spacing combinations which maximized leaf area index when grown under weedy conditions also had significantly less weed dry weight. However, row and plant spacings did not reduce weed density. A significant negative cor-relation was observed between weed dry weight with leaf area index and final yield of pinto bean. For each kg ha-1 increase in weed dry weight, the corresponding pinto bean yield loss averaged 260 g ha-1. Season-long weed competition significantly reduced total number of pods per plant, number of seed per plant, and 100-seed weight.
H. Filizadeh, A. Rezazadeh, Z. Younessi,
Volume 9, Issue 2 (4-2007)
Abstract
Crop rotation is one of the essential practices in sustainable agricultural systems, be-cause of its effects on soil fertility and other benefits including a reduction in weed compe-tition. A field experiment was conducted at Chaparsar Rice Research Station, Tonekabon, Iran, from 2002 to 2003 to assess the influence of crop rotation, time of planting, and till-age depth on rice (Oryza sativa L.) yield and density and the biomass of three important paddy weeds. Treatments included the crop rotations of continuous rice and rice-soybean-rice, in combinations with planting times and no tillage, minimum tillage, and chisel plow-ing. Crop rotation had a significant effect on the growth of barnyardgrass (Echinochloa crus-galli), arrowhead (Sagittaria sagittifolia), and water plantain (Alisma plantago-aquatica) weeds. Continuous rice planting produced the highest density of barnyardgrass, arrowhead, and water plantain weeds, compared with a rice–soybean-rice rotation. Weed biomass and weed densities were lower in the rice-soybean-rice rotation than in continu-ous rice. There were a 62.5 and 80% reductions in the weed density and weed biomass re-spectively, in the rice-soybean-rice rotation compared with continuous rice planting. Fewer barnyardgrass, arrowhead and water plantain growth were observed in no-tillage treatments than in minimum tillage and chisel. Therefore, rice yield in rotation treat-ments increased by 17 and 21% in 2002 and 2003, respectively, compared to continuous rice planting.
