Rhizotron study on soil moisture and plant population effect on root competition of cotton and mungbean with Trianthema portulacastrum and Echinochloa crus-galli

摘要

The effects of soil moisture and plant population on root competition between crop and weed was studied in rhizotron tubes at three levels of irrigation [0.3, 0.6 and 0.9, based on ID/CPE (irrigation depth and cumulative pan evaporation) ratioj. Threeplant population ratios of 3:0, 2:1 and 1:2 for crop and weed species for cotton or mungbean (in separate experiments) with Trianthema porlulacastrum and Echinochloa crus-galli, were compared after 50 days for root competition. Root and shoot length, and shoot weight of cotton was unaffected by moisture levels, but root weight increased by 127% with increase in ID/CPE ratio from 0.3 to 0.9. Moisture level or competition with cotton had no effect on root or shoot length of T. portulacastrum. One plant of T. porlulacastrum (1:2 ratio) significantly reduced cotton root/shoot length and dry weight, whereas T. portulacastrum root and shoot weight increased by 174 and 252% respectively. Root competition was more severe with E. crus-galli compared to T. portulacastrum as one plant of E. crus-galli (with 2 of cotton) was potent enough to reduce cotton root length and root weight by 33 and 59%, respectively. Shoot and root length of E. crus-galli had no effect of moisture level. Competition with cotton (1:2ratio) reduced shoot and root length of E. crus-galli, but its shoot and root weight increased by 177 and 165%, respectively. Increase in moisture level from 0.3 to 0.9 (ID/CPE) had no significant effect on root or shoot length of mungbean or T. portulacastrum, but significantly increased their root and shoot weight. Decreasing plant population of mungbean from 3 to 1 significantly reduced its root/shoot length and dry weights, whereas root and shoot weight of T. portulacastrum increased by 234 and 218%, respectively. Root length and root weight of mungbean increased with increase in moisture level, but decreased significantly in competition with E. crus-galli.