Manipular La Orientación De Cultivos En Hileras Para Suprimir Las Malezas y Aumentar La Producción Agrícola

Weed Science 2010 58:174–178

Manipulating Crop Row Orientation to Suppress Weeds and Increase Crop Yield
Catherine P. D. Borger, Abul Hashem, and Shahab Pathan*
Crop rows oriented at a right angle to sunlight direction (i.e., east–west within the winter cropping system in Western Australia) may suppress weed growth through greater shading of weeds in the interrow spaces. This wasinvestigated in the districts of Merredin and Beverley, Western Australian (latitudes of 31u and 32uS) from 2002 to 2005 (four trials). Winter grain crops (wheat, barley, canola, lupines, and field peas) were sown in an east–west or north–south orientation. Within wheat and barley crops oriented east–west, weed biomass (averaged throughout all trials) was reduced by 51 and 37%, and grain yield increased by24 and 26% (compared with crops oriented north–south). This reduction in weed biomass and increase in crop yield likely resulted from the increased light (photosynthetically active radiation) interception by crops oriented east–west (i.e., light interception by the crop canopy as opposed to the weed canopy was 28 and 18% greater in wheat and barley crops oriented east–west, compared withnorth–south crops). There was no consistent effect of crop row orientation in the canola, field pea, and lupine crops. It appears that manipulation of crop row orientation in wheat and barley is a useful weed-control technique that has few negative effects on the farming system (i.e., does not cost anything to implement and is more environmentally friendly than chemical weed control). Nomenclature: Barley,Hordeum vulgare L.; canola, Brassica napus L.; field pea, Pisum sativum L.; lupine, Lupinus angustifolius L.; wheat, Triticum aestivum L. Key words: Light interception, row orientation, row spacing, weed biomass, grain yield, annual ryegrass, wild radish.

Light availability is an important factor in regulating the competitive relationship between crops and weeds because light influences thegrowth and development of neighboring plants (Ballare and Casal 2000; Ballare et al. 1990; Ghersa et al. 1994; Holt 1995; Rousseaux et al. 1996). During early growth stages, there is interference between crop and weed plants because of reflected light. The reflection of far-red photons by the stem of one plant lowers the red to far red photon ratio of light experienced by the stems of neighboringplants. This modifies the light environment in the plant stem tissue, which results in an increased stem elongation rate. As plants age, the crop canopy closes, and mutual shading further increases the competition for photosynthetic light. Shaded leaves lower in the canopy have access to low levels of photosynthetically active radiation and a low-red to far-red photon ratio. Light also influencesflowering and fruit set. Therefore, light is a significant determinant of crop productivity. Crops can be manipulated to increase shading of weeds by the crop canopy, to suppress weed growth, and to maximize crop yield. One possible way to reduce light interception by weeds and to increase light interception by the crop canopy is to manipulate the crop row spacing and orientation (Holt 1995). Reducingthe space between crop rows or orientating crop rows at a near right angle to the sunlight direction increases the shading of weeds between the rows. The growth of poison ryegrass (Lolium temulentum L.), littleseed canarygrass (Phalaris minor Retz.), wild oat (Avena fatua L.), and common vetch (Vicia sativa L.) in wheat (‘308’) crops and black nightshade (Solanum nigrum L.) in vineyards (Vitisvinifera L.) were influenced by crop row spacing and orientation (Angiras and Sharma 1996; Sharma and Angiras 1996a,b; Shrestha and Fidelibus 2005). Furthermore, in the absence of weeds, orientation affected crop yield or soil
DOI: 10.1614/WS-09-094.1 * First author: Department of Agriculture and Food Western Australia, Dryland Research Institute, P.O. Box 432, Merredin, WA, Australia 6415;...