Understanding crop-weed-fertilizer-water interactions and their implications for weed management in agricultural systems

Crops and weeds share the same aboveground/aerial (sunlight, space, atmospheric gases, etc.) and underground/soil (water and nutrients) resources. Competition is a predictable response of organisms living in communities, and is a struggle between two organisms for a limited resource that is essential for their growth. Crop-weed competition causes an alteration in the utilization of various resources and also affects complex interactions between plants and environmental factors. Water, nutrients, light, and space are the major factors for which organisms compete. Light and space are the main aboveground resources, and the effects of competition for these resources can be visually observed. This article focusses on crop-weed interactions for underground resources - nutrients and water. Weeds, being more aggressive, adaptive and persistent than crops, pose a serious threat to crop production as they have the ability to survive under adverse conditions and extract more water and nutrients from the soil; thereby, reducing crop yields. Fertilizer application and inherent soil fertility have a definite influence on weed diversity, emergence, growth, dormancy, persistence, and crop-weed competition. Weed suppression with balanced fertilization through increased competition for light has been regarded as one of the most important determinants of the yield advantage of a crop, and the effect on yield depends upon the interaction of crop and weed flora. The elimination of weeds from crops is the most efficient and practical means of reducing transpiration and thus saving water for crop use. Additional fertilizer and water amounts cannot compensate fully for yield losses due to weed competition, but appropriate fertilizer and water management could be used as an important tool in integrated weed management systems, which may prove helpful for achieving higher net returns.