Plant competition is a well known and thoroughly examined area of plant ecology but most studies have been based on describing the effects of competition, and only few have been working with the mechanisms involved in, or the application of plant competition in agriculture and plant production.
Recent studies have shown that competition between weed and crop is controllable and applicable as weed control in grain crops. Experiments have shown that the herbicide application can be reduced as much as 50-100 % by a change in the sowing pattern and an increase in crop density. Other positive side effects from this method could be decrease in use of fossil fuels and CO2 emission as well as less driving in the field and thereby a smaller risk of soil compaction.
Often, but not always, larger plants have an over-proportional advantage in competition with smaller plants. Germinating crop plants are larger than weed seedlings and have a natural competitive advantage. However, this advantage is not utilised in recent cropping systems. The advantage can be increased by i.e. increasing the crop density and by changing the sowing pattern from rows to a two dimensional, uniform pattern.
Previously studies have shown belowground competition to be size-symmetric but these results are based on homogenous soil conditions. One hypothesis is that high nutrient patches belowground may shift the competition to asymmetric. However it is not yet proven how large an effect the belowground competition has. If belowground competition is, or can be, size-asymmetric, it might be possible to increase the degree of asymmetry and thereby help the crop to suppress weeds by changing the cropping system for instance by fertilising to optimise the competition between crop and weed.
The knowledge obtained will (hopefully) be helpful in the understanding of the mechanisms involved in crop-weed competition, and useful in the development of the next generation of biological weed control in grain crops.