Effect of Irrigation and Nitrogen Levels on Grassy Weed Competition in Wheat and Comparative Eco-Physiology of Phalaris minor Retz. and Avena sterilis ssp. ludoviciana Dur. in Wheat

In a field experiment for two years, 1998–99 and 1999–2000, dry weight of Phalaris minor and its growth rate (PGR) was significantly higher in crown root initiation (CRI) and CRI+flowering irrigation regimes than in others. Consequently dry weight and crop growth rate (CGR) of wheat decreased significantly in these treatments. Total dry weight of grassy weeds too followed similar trend. Wheat plant growth (dry weight, CGR) was almost 10 times higher than that of P. minor. CRI+tillering+flowering+dough irrigations being at par with CRI+tillering+flowering recorded significantly higher dry weight, crop growth rate (CGR), ear-bearing tillers and grain yield of wheat than other irrigation regimes. Higher the dose of N, lower were the population, dry weight and growth rate of P. minor and as a result, wheat growth (dry weight, CGR) recorded a gradual increase upto 150 kg N/ha. The 150 kg N/ha being at par with 120 kg N/ha, reduced the population and dry weight of P. minor and total grass weed significantly in second year. Wheat plant height in plots receiving 150, 120 and 90 kg N/ha over 60 kg N/ha and number of ear-bearing tillers and grain yield in 120 and 150 kg N/ha over 90 and 60 kg N/ha were significantly higher. In another experiment, two peaks–one at initial 0–10 DAS and other at 25–30 DAS were observed in the germination of P. minor in wheat field. Wild oat, on the contrary, had maximum germination (about 49%) at the initial 0–10 DAS. There was hardly any new flush of germination of P. minor after 40 DAS. Both P. minor and wild oat, initially at 0–10 DAS, germinated from shallower depths of soil. Later too, their germination took place from shallower depths from 15 DAS. In a weedy situation, wheat recorded highest area and dry weight of flag leaf followed by wild oat and P. minor. The rate of photosynthesis recorded from detached flag leaf, however, was the highest in wild oat followed by wheat and P. minor. Wild oat had maximum length of earhead followed by wheat and P. minor, but on total number of seeds per earhead, P. minor appeared most prolific breeder and seeder, wild oat remained intermediate and wheat much inferior.