APPROACHES FOR IMPROVING CROP COMPETITIVENESS THROUGH THE MANIPULATION OF FERTILIZATION STRATEGIES

Weeds are often more competitive with crops at higher soil nutrient le vels. This can result in increased dependency on herbicides and tillag e to maintain adequate weed control. A number of studies have shown we eds accumulate higher concentrations of nitrogen, phosphorus, potassiu m, calcium, and magnesium than crops, thus depleting soil nutrient lev els more quickly and reducing crop yield. Understanding basic mechanis ms and timing of nutrient uptake in weeds and crops can lead to fertil ization strategies which will enhance the competitive ability of crops while reducing interference from weeds. Such strategies can include d eep band application of fertilizers to the crop row, as opposed to bro adcast applications. Banding techniques also reduce the potential for nitrate contamination of surface or groundwater. The addition of nitri fication inhibitors or increasing the proportion of nitrogen as ammoni um or urea in fertilizer mixtures can restrict growth of ammonium- or urea-sensitive weeds. The timing of fertilizer applications can take a dvantage of maximal rates of nutrient uptake into crop roots at specif ic developmental stages. In addition, nutrient use efficiency can be e nhanced by choosing appropriate crop cultivars, maintaining effective weed control practices, or altering row spacing or seeding rate to inc rease accumulation of nitrogen, phosphorus, and potassium in crops.