Effect of herbicides and submergence period on red sprangletop [Leptochloa chinensis (L.) nees] in transplanted Rice

A field experiment was conducted to evaluate the effect of herbicides and submergence period on the growth behaviour of emerging weed Red Sprangletop [Leptochloa chinensis (L.) Nees] in transplanted rice on a loamy sand soil during kharif 2003 and 2004 at Punjab Agricultural University, Ludhiana in a split plot design with three submergence periods (one, two and three week after transplanting of rice) in the main plots and four herbicides (butachlor 1.5 kg, anilofos 0.375 kg, pretilachlor 0.75 kg and pyrazosulfuron 0.015 kg ha⁻¹) along with an unweeded control in the sub plots. The two and three week submergence, though statistically at par, were significantly better than one-week submergence in registering better control of Leptochloa chinensis by reducing its emergence, plant height, LAI and dry matter accumulation leading to higher grain yield of rice. The submergence of two and three week registered 46.7 and 48.1 per cent increase in grain yield of rice over the one week submergence, respectively. All the herbicides were statistically at par but were significantly better than the unweeded control in respect of growth parameters of L. chinensis and grain yield of rice. The growth of L. chinensis was not adversely affected by herbicides under one week submergence.