---

To study the effects of plant density and nitrogen rates on the ability of canola (Regent  Cobra; an inbred variety) to compete with weeds, an experiment was conducted as a factorial complete block design with four replications. The treatments included four levels of plant density at 150, 190, 230, and 270 plants m-2, and four levels of nitrogen (N) fertil-izer at 0, 46, 92, and 138 kg ha–1. Results indicated that different levels of plant density and N fertilizer had significant effects on the canola’s leaf area index (LAI) and dry mat-ter accumulation, as well as on the weed’s dry matter at three stages of plant growth (ro-sette, stem elongation, and 50% flowering). The addition of N fertilizer resulted in in-creasing plant LAI and decreasing weed dry matter. Densities of 150 and 270 plants m-2, along with 138 kg ha–1 nitrogen showed the highest LAI at the rosette and stem elongation stages. The LAI at different plant growth stages was an important factor in enhancing ca-nola’s competitiveness with weeds. There were significant differences between different plant density and N fertilizer levels for traits such as plant height, pod bearing stem length, biomass and seed yield. An increase in plant density significantly decreased the pod bearing stem length and total pod numbers per plant (i.e. pod numbers in main branches and sub-branches), but increased plant height. The highest seed yield was ob-tained with 190 plants m-2 along with 138 kg N ha–1. This study revealed that optimum plant density as well as N fertilizer may increase the competitive ability of canola against weeds.

---

This experiment was performed to determine the appropriate dose of Cyhalofop-butyl (CB) for controlling grass weeds in transplanted rice. CB at four doses, including 50, 100, 150, and 200 g ai/ha was investigated and compared with current herbicides in rice at recommended doses. The results showed that CB 100, 150, and 200 g ai/ha significantly reduced the density and dry matter of Echinochloa crusgalli (L.) P. Beauv. and Paspalum distichum L. over the weedy check; the minimum control efficacy of CB at these doses was 73.3 and 88.3% for E. crusgalli density and dry matter reduction, respectively, and for P. distichum, it was 80% for density and dry matter reduction. Applying CB at all doses (50- 200 g/ha) showed no crop injury symptoms on rice plants. The highest grain yield was obtained by hand weeding, CB 150 g ai/ha, and Tiobencarb treatments, with 5180, 5106, and 5051 Kg/ha, respectively. CB 200 g ai/ha was on par with CB 150 g ai/ha, and there was no significant variation between CB 100 and 200 g ai/ha in rice grain production. Finally, it was found that the application of CB 100 g ai/ha is an efficient grass weed control practice for improving the rice yield.

 

---

A field study was conducted to determine the integration of split N fertilization and herbicide application on weed management and wheat (Triticum aestivum L.) yield in Shiraz, Iran, in 2005/2006 and 2006/2007 growing seasons. The experimental design was split plot with four replications. Main factors consisted of N timing and splitting, and sub plots included iodosulfuron–methyl–sodium plus mesosulfuron–methyl–sodium, solfosulfuron and two weedy and weed free controls. Compared with the weedy check, iodosulfuron–methyl–sodium plus mesosulfuron–methyl–sodium and solfosulfuron reduced weed biomass by 66% in 2005/06 and 55% in 2006/07, 37% in 2005/06 and 45% in 2006/07, respectively. In all herbicide treatments applied in both years, the highest (353.6 kg h-1 in 2005/06 and 224.1 kg h-1 in 2006/07) and the lowest (65.6 kg h-1 in 2005/06, and 24.0 kg h-1 in 2006/07) weed biomass were obtained from the full N (304 kg urea ha-1) application at tillering stage and zero N application at sowing and stem elongation stages T1N0, T2N1, T3N0 and no N fertilization at sowing, tillering and stem elongation stages T1N0, T2N0 and T3N0. Nitrogen use efficiency of the crop increased when N was split. Consequently, wheat LAI and grain yield increased. However, in the presence of weeds, both LAI and grain yield increases were lower. The results of the present study showed that integration of N and herbicide treatments caused even a higher increase in wheat LAI and grain yield, but resulted in a higher reduction in weed biomass when compared with either treatment alone. N splitting of T1N½, T2N½ and T3N0 increased wheat grain yield (61% in 2005/06 and 75% in 2006/07), biological yield (76% in 2005/06, 94% in 2006/07), and LAI (62% in 2005/06 and 2006/07). In conclusion, weed control was essential for efficient use of N fertilizer by the crop. Therefore, in order to increase wheat grain yield, integration of split N and herbicide is recommended for the region. The results of this study showed that N splitting treatments of T1N½, T2N½, T3N0 and iodosulfuron–methyl–sodium plus mesosulfuron–methyl–sodium had the best efficiency in terms of weed control in wheat.

---

South Africa is considered as a water scarce country and water shortage is a major constrains that often limits growth, yield, and quality of Swiss chard. A field experiment was conducted on Swiss chard (Beta vulgaris L.) in loamy soil to evaluate Water Use Efficiency (WUE), weed control, yield, and quality response to organic and inorganic mulch application during the winter/spring season (June to September). Treatments included bare-soil (control), grass/hay, and newspaper, white-maize-meal bag, white plastic and black plastic mulches. Black plastic, newspaper, and grass/hay mulches suppressed weeds significantly, which were encouraged under bare-soil, white plastic, and maize-meal bag mulch conditions. There was an increase in the number of leaves and leaf fresh mass with white plastic mulch, while bare-soil reduced plant dry mass and leaf area significantly. Leaf area was improved with white plastic, black plastic and maize-meal bag mulches. White plastic and grass/hay mulch improved WUE significantly, and exceled above other treatments at 259.9 and 242.0 kg ha^-1 mm^-1, respectively, followed by black plastic mulch at 207 kg ha^-1 mm^-1. Water use efficiency declined in the newspaper, maize-meal, and bare-soil treatments at 179, 130 and 74.7 kg ha^-1 mm^-1 WUE, respectively. Thus, the study reveals that the use of mulch under drip irrigation has an explicit role in increasing water productivity of Swiss chard.