Assessing critical period of weed competition in direct seeded rice (Oryza sativa L.)

In the present era, direct-seeding is a viable alternative of traditional transplanting of rice for farmers due to water and labour shortage. It has the potential to ensure water and labour saving along with higher productivity of water. Study was performed to assess the critical period of weed-crop competition i.e. time period during which weeds cause maximum reduction of yield in dry direct-seeded basmati rice during two consecutive summer seasons of the years 2015 and 2016. This experiment consisted of 6 weed competition periods [0, 2, 3, 4, and 5 weeks after crop emergence (WAE)] and 6 weed-free periods (0, 2, 3, 4, and 5 WAE) by mixed weed flora. The experiment was executed in randomized complete block design having four replications. With the increasing duration of the weed-crop competition, the productive tillers, grains per panicle, and 1000-grain weight were decreased gradually. A whole season competition with mixed weed flora reduced rice grain yield up to 90% and increased N, P, and K uptake by weeds up to 28, 5, and 28 kg ha 1, respectively. In dry direct-sown rice, the critical time of weed removal as estimated by the three-parameter logistic model was 1.4-6.3 WAE and 2.8-4.8 WAE to save 10 and 20% grain yield, respectively. Hence it is concluded that dry direct-seeded rice crop should be kept weed free during this time period of crop growing season.