Integration of Cultural and Chemical Methods for Purple nutsedge (Cyperus rotundus L.) Management.

Abstract

Cyperus rotundus is a pernicious, perennial and a difficult to control weed. The weed presents a serious constraint to crop production under spate irrigation particularly at Elsemeyh Agricultural Scheme (EAS) in Western Sudan where disc harrowing supplemented by hand weeding is the standard method of weed control. The EAS (21 thousand feddan) constitutes 33% of Khor Abu Habil Project. The present study was made to develop an integrated management strategy for C. rotundus in cotton. The investigation, comprising field and supplementary laboratory and screen house experiments was undertaken at the College of Agricultural Studies Sudan University of Science and Technology and EAS results revealed that C. rotundus tuber population density was highest (49.33%), intermediate (29.72%) and lowest (20.95%) at 0-10 cm, 10-20 cm and 20-30 cm soil depth, respectively. C. rotundus tubers progressively lose moisture, sprouting capacity and viability when exposed to heat. Tubers exhumed from 0-10 cm depth showed 0.89, 0.94 and 5.56% loss in moisture content, 88.78, 88.78 and 100% loss in sprouting capacity and 7.75, 56.25 and 100% loss in viability following exposure at 70 °C for 1, 2 and 4 h, respectively. Tubers exhumed from deeper soil depths lost moisture contents less rapidly. However, sprouting capacity and viability were completely lost within 1-4 h of exposure. Tubers placed on the soil surface for 16 days displayed 19.97% loss in moisture content and complete loss in sprouting capacity. Deep blading, and disc ploughing, in April, resulted in excellent (>80%) suppression of C. rotundus at cotton planting time in July. However, regeneration occurred 2 and 3 weeks later. Among all treatments disc ploughing in April supplemented by a tank mix of glyphosate and pendimethalin at cotton planting effected the IV best weed control and achieved over 50% more seed cotton yield than the 10 years average of the scheme. Data availed by this study clearly showed that no single method sustained, spatially and temporally, consistent weed control and profitable cotton yield in the EAS and that the conventional tillage practices need to be supplemented by herbicides. Furthermore, the results suggest that improvement of cultural practices, particularly those which lead to rapid crop canopy closure, together with improvement of herbicides application technology are imperative. Moreover, introduction of glyphosate resistant cotton, suitable for growing under Sudan conditions, could be a significant part of the solution.