INTERNATIONAL JOURNAL OF AGRICULTURE & BIOLOGY 1560–8530/2005/07–5–712–718 http://www.ijab.org Increasing the Efficiency of Sorghum Water Extract (Sorgaab) by Mixing with Lower Doses of Isoproturon to Control Weeds in Wheat MUHAMMAD JAMIL, ZAHID ATA† AND ABDUL KHALIQ† National Agricultural Research Center, Islamabad–Pakistan †Department of Agronomy, University of Agriculture, Faisalabad– 38040, Pakistan 1 Corresponding author’s e-mail: jamil_narc@yahoo.com ABSTRACT The proposed field study to enhance the efficiency of conc. sorgaab (Sorghum bicolor water extracts) by mixing it with lower doses of isoproturon to control weeds in wheat was carried out during two years. Concentrated sorgaab was combined with reduced rates of isoproturon i.e.150, 300, 450, 600 and 1000 g a. i. ha -1 . Two sorgaab sprays each at 30 and 30 + 40 days after sowing (DAS) and a weedy check was also included. One foliar spray of conc. sorgaab @ 12 L ha -1 combined with isoproturon @ 600 g a. i. ha -1 appeared best treatment combinations with maximum reduction of total weed density (89-97%) and dry weight (91-99%) and this decrease was statistically equal to the standard dose of isoproturon @ 1000 g a. i. ha -1 . Sorgaab along with isoproturon reduced total weed density and biomass due to both allelopathic and herbicidal activities. Maximum increase in grain yield was obtained in plots treated with conc. sorgaab @ 12 L ha -1 and isoproturon @ 600 g a. i. ha -1 combination at 30 DAS. The yield influencing parameters as plant height, spike length, number of productive tillers m -2 , spikelets per spike and grains per spike were also significantly influenced by all the treatments and conc. sorgaab @ 12 L ha -1 and isoproturon @ 600 g a. i. ha -1 combination at 30 DAS performed better. Moreover T 11 i.e. one spray of conc. sorgaab @ 12 L ha -1 with isoproturon @ 600 g a. i. ha -1 appeared the best treatment among sorgaab and isoproturon combination with higher net benefits and MRR% during both years. Key Words: Wheat; Weed control; Sorghum water extract; Isoproturon INTRODUCTION Sorgaab (Sorghum Water extract) used as foliar spray has been found to inhibit the dry weight of several weeds as Avena fatua, Phalaris minor, Chenopodium album, Rumex dentatus, Anagallis arvensis, Cyperus rotundus, Convolvulus arvensis, Senibera didyma and certain other weeds (Ahmad et al., 1991; Cheema, 1999; Cheema et al., 2000; 2002; 2003c). The suppression of weeds by sorgaab generally ranged between 28-48% (Cheema et al., 2002), which is insufficient control. For minimizing the damage caused by weeds and to bring it to the economic threshold level, the weeds must be controlled up to 80% or more depending upon the nature of the weeds and the extent of infestation (Jalis & Shah, 1984). Isoproturon is widely used in Pakistan for weed control in wheat crop. Continuous use of one herbicide, might favour development of resistant biotypes or the herbicide may loose its effectiveness. Therefore, it is always required to develop new strategies for getting efficient weed control. One aspect is combination or mixing of different herbicides, another possibility is to combine herbicides with natural phytotoxins (Einhelling & Leather, 1988). This might provide environmentally safer and economically viable combinations. Some of the recent studies (Cheema et al., 2003a, e) indicated that combination of sorgaab @ 12 L ha -1 with lower dose of herbicide as Atrazine @ 150 g a. i. ha -1 was as effective as the full dose of the respective herbicide @ 300 g a. i. ha -1 for controlling weeds. The present study was contemplated to explore possible reduction of isoproturon dose in combination with sorgaab, an allelopathic water extract for getting weed control up to 80-95% or similar to full dose of herbicides. MATERIALS AND METHODS The field trials to improve the efficiency of sorgaab (Sorghum bicolor water extracts) by combining with lower doses of isoproturon, was carried out at the Agronomic Research Area, University of Agriculture, Faisalabad for two years. The experiment was laid out in randomized complete block design (RCBD) with three replications in 7m x 2m plot size. Sorghum (Sorghum bicolor L.) was harvested at maturity, dried for a few days, chopped with electric fodder cutter into 2cm pieces and stored under shade. This chopped material was soaked in distilled water for 24 hours at room temperature (21 o C) in a ratio of 1:10 (W/V) and were filtered with the help of sieve (10 & 60 mesh) according to procedure devised by Cheema et al. (1998). The extract was boiled at 100 o C to concentrate up to 20 times for easy handling and application. The