Development and testing of practical control action indicators for weed management in broadcast-seeded wetland rice.
1994
Paller E.C. | Angela J.C. | Magsino G.L.
In the 1992 trial where the predominant weed species were Cyperus difformis, Leptochloa chinensis (L.) Nees and Fibristylis littoralis Gaud., relative crop density (RCD), tiller number (TN), leaf number (LN), and relative crop fresh weight (RCFW) were highly and positively correlated with rice grain at 15, 30, and 45 DAS. Relative weed height (RWH) was negatively correlated with rice grain yield at 15 and 30 DAS. In 1993, where the predominant weed species were C. diformis, F. littoralis and Sphenoclea zeylanica Gaertn., RCD was significantly and positively correlated with rice grain yield at 15 and 30 DAS, highly and positively correlated with the same at 45 DAS. RWH was significantly and negatively correlated with rice grain yield at 15 DAS; RWH and relative weed cover (RWC) were negatively and highly correlated with the same at 30 and 45 DAS. TN and LN positively and significantly correlated with grain yield at 15 DAS but highly and positively correlated with the same at 45 DAS. Plots that were managed with the aid of weed control action indicators developed in 1992 required only one handweeding for the whole season but the resulting grain yields were comparable with those that were handweeded two to five times. The use of control action indicators reduced labor requirement for weed control from 58 to 80 percent compared with handweeding three times. The use of combination of RWH and RCD as indicator for supplementary control action in rice applied with pre and post-seeding treatments of butachlor required one additional handweeding at 30 DAS, but gave grain yields significantly higher than those treated with butachlor alone; grain yield increase ranged from 38 to 52 percent.
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