Effects of Fertilizer Placement on Weeds in Weed Harrowed Spring Barley

Abstract A series of six field experiments on spring barley were conducted to test the effect of fertilizer placement compared with broadcast application on weeds and crop yield. The experiments were carried out in 1993, 1994 and 1995, on two soil types, with three levels of fertilizing and without use of pesticides. Fertilizer placement reduced weed biomass by 55% and weed density by 10% and increased grain yield by 28%, on average. The strong effects on weeds were presumably due to a positive interaction between crop competition and weed control by weed harrowing. The biomass of almost all frequent weed species was reduced by fertilizer placement. The effect of fertilizer placement on weed density was weaker than on biomass. Fertilizer placement increased grain yield more on coarse sand than on sandy loam. All the effects were more pronounced in 1993 than in 1994 and 1995, most likely owing to dry weather in the spring of 1993.