Effect of amaranth residues (Amaranthus hypochondriacus L.) on weed control and yield or radish, onion and carrot

Abstract

Studies were conducted to evaluate the effect of dry residue of amaranth (Amaranthus hypochondriacus L. var. Azteca) stem on weed growth and yield of radish (Raphanus sativus L. var. Champion), onion (Allium cepa L. var. Cambray), and carrot (Daucus carota L. var. Nantes), in order to determine the inhibitory effect of amaranth. The treatments were established under field conditions: 1) aqueous extract (AE); 2) soil-incorporated residue (S-IR); 3) surface-applied residue (S-AR); 4) unaltered soil control (U-S/C); 5) soil-incorporated control (S-I/C). The soil type at the study site was loamy-sand, with bulk density 1.47 m–3, containing 2.1% organic matter. The species with the largest number of plants and highest dry weight in the three vegetables were Simsia amplexicaulis (Cav.) Pers., and a group of Gramineae grasses. Weed reduction was observed with treatments S-AR and S-IR related to the respective controls (U-S/C and S-I/C). Generally, decrease in plant number and dry weight in both treatments varied from 60% to 97% during the vegetable cycle. Radish yield decreased significantly with S-AR and S-IR; whereas that of onion and carrot increased significantly with S-AR. The results indicate that amaranth residue, incorporated or surface applied may control some weeds in radish, onion, and carrot. The surface-applied residue has potential to increase the yield of onion and carrot. However, it is necessary to find optimal residue management conditions for its application in the field to avoid reduction in yield of sensitive crops like radish, and/or when the residue is incorporated.