The Effects of Plant Litter and Inorganic Fertilizer on Crop-Weed Interactions in a Temperate, Rich-Soil Site

Abstract

ABSTRACT Litter (mulch) may have potential for sustaining low-technology agriculture in at least two capacities: as a nutrient source and as weed control. This experiment discriminates between these two possible effects at a temperate site in Michigan, U.S.A. The design consisted of four factors—corn (Zea mays L.), weeds, grass-alfalfa straw mulch, and N-P-K fertilizer—each at two levels, present and absent. Measured were corn height and yield (fresh weight of cobs); weed emergence and yield (above-ground biomass); and soil levels of K, Mg, and Ca. Mulch increased corn yields evidently by suppressing weeds rather than by adding nutrients. Its effect on yield did not depend on fertilizer level. Fertilizer increased corn growth and yield; it increased weed biomass only in the absence of corn. Both mulch and fertilizer increased corn yield differentially more with weeds present than absent, mulch by suppressing weed emergence, fertilizer by benefiting corn more than weeds. Consequently, the combination of fertilizer and mulch provided excellent weed control. Generalizations about if and how much mulch might work to sustain agriculture cannot readily be inferred since timing of mulch application did not permit full decomposition and initial soil fertility was relatively high. Where more time for mulch decomposition is allowed or where soil fertility is lower, a nutrient-supplying effect of organic mulch should be more apparent.