Biology and management of Phalaris minor in wheat under a rice/wheat system

Germination of Phalaris minor declined with the increase in duration of imbibition in water from 30 min to 72 h at temperatures above 22 degreesC. Germination was reduced down to 10 cm and 2 cm soil depth by wheat straw burning in puddled and non-puddled soil, respectively, with maximum reduction near the soil surface. The dormancy of P . minor seed was not more than 60 days under field conditions. In puddled soil, 38-60% of the viable seeds of P. minor remained concentrated in the upper 5-cm layer. Germination decreased with an increase in soil depth. In total, 15% of seeds stored in the laboratory emerged from 10-cm depth, whereas seeds did not germinate below 4.2-cm depth under field conditions. Depth of emergence of P . minor was shallower in zero tillage compared with the conventional method of wheat sowing. The seeds retrieved from rice soils kept under continuous submergence for 60 days exhibited 26% and 57% loss of germination over semi-submergence and semi-wet conditions respectively. There was 100% loss of germination in 10-month-old seeds retrieved from the soil under rice-growing conditions. Plant density of P. minor was lower in zero tillage than with the conventional method of wheat sowing. Cross-ploughing in the upper 2-5 cm of soil (shallow tillage) and drill-sowing of wheat 1 week after shallow tillage reduced germination of P. minor by 44% and 37% and increased grain yield by 21% and 47% over zero-tillage and conventional methods respectively.