Higher demand for organically grown foods has farmers seeking new methods to increase crop yields and reduce weeds without the use of chemicals. One very practical solution uses a readily available resource and requires no additional costs or time-consuming weeding and cultivating. It is, simply, maximizing the light of the sun.
The March-April issue of the journal Weed Science reports the results of four trials of crop orientation conducted from 2002 to 2005 in Western Australia. Researchers compared the effects of orienting rows of crops north to south or east to west to allow the crops to increase their exposure to sunlight while decreasing access to light for weeds.
Crops compete with weeds for light. Situating the crop rows at a near right angle to the sunlight direction can influence the light interception. Crops can create a canopy over weed plants, giving the weeds more shade than sun, suppressing weed growth and maximizing crop yield.
Grain crops of wheat, barley, canola, field peas, and lupine were sown in both north-to-south and east-to-west orientations in the Australian experiment. Wheat and barley crops experienced significant yield increases when placed east to west rather than north to south—a 24% increase for wheat and a 26% increase for barley. Weed biomass was reduced by 51% and 37%, respectively, for these two crops.
The remaining three crops, canola, field peas, and lupine, did not show a consistently significant difference between the two orientations. The authors theorize that because these are broadleaf crops and have a wider canopy structure than the cereal crops, the row orientation provides less advantage.
Location determines which direction crops should be planted for the best utilization of sunlight. The Western Australian Wheat Belt ranges from 28 degrees to 33 degrees south in latitude with a winter and spring growing season, making east-west crop orientation the most advantageous. Near the equator, north-south orientation would yield the best results, while latitudes up to 55 degrees would benefit from north-south crops in the summer and east-west crops the rest of the year. At latitudes above 65 degrees, east-west orientation would offer the best light absorption throughout the year.
Full text of the article, “Manipulating Crop Row Orientation to Suppress Weeds and Increase Crop Yield,” Weed Science, Volume 58, Issue 2, March-April 2010, is available at http://www2.allenpress.com/pdf/WEES_58.2_174-178.pdf.