NUTRIENT ACCUMULATION BY WEEDS AND THEIR ASSOCIATED VEGETABLE CROPS

A field study showed that weeds are better nutrient accumulators than tomato and bean crops. Percentages of N, P, K, and Mg in shoots of most weed species were higher than in crop plants. Weeds associated with bean accumulated more P in roots than did crop plants, and weeds of tomato field contained higher percentages of P and K than the crop. All weed species showed lower concentration of Ca in shoots and roots than did crop plants. Weeds varied substantially in their shoot and root percentages of mineral elements and differences in nutrient percentages between shoots and roots of weeds were greater than with crop plants. Malva sylvestris, Chenopodium murale, Portulaca oleracea and Rumex obtusifolius are nutrient accumulator weeds. Tomato appeared to be better than bean in competition with weeds.