Effect of planting patterns and herbicides application on weed population, grain yield and water use efficiency in maize (Zea mays L. cv. KSC 704)

This experiment was conducted for 2005 and 2006 cropping seasons to evaluate the effects of planting patterns and herbicides application on weeds population and grain yield of maize as well as on enhancement of water use efficiency at Dezful and Karaj, I. R. Iran. The experimental design was strip block arrangements in a randomized complete block design with three replications. Planting patterns were assigned to vertical plots at four levels including: planting of one and two rows of maize on beds and one and two rows of maize in furrows. Application of herbicides was assigned to horizontal plots at six levels including; pre-emergence application of a mixture of atrazine + alachlor at (0.8 + 2) kg ai.ha-1 and also at 25% reduced rates, pre-plant application of EPTC at 4 kg ai.ha-1 and also at 25% reduced rate, weedy and weed free controls. Average total weed density reduced in Dezful by application of atrazine + alachlor by 63% as comparing to the weedy control. However, in Karaj by application of atrazine + alachlor and EPTC total weed density reduced by 65 and 56%, respectively, when comparing to the weedy control,. In 2005, application of a mixture of atrazine + alachlor at (0.8 + 2) kg ai.ha-1 in planting pattern of two rows of maize on beds reduced dry weight of weeds by 71.7%. However, in 2006, application of the same herbicide treatments in planting pattern of two rows of maize on beds and in furrows reduced dry weight of weeds by 92%. In both Dezful and Karaj, weed free controls, in planting pattern of two rows of maize on beds, with 13.34 t.ha-1and 12.91 t.ha-1 had the highest and application of EPTC at 3 kg ai.ha-1 and weedy controls both in planting pattern of one row of maize in furrows with 6.99 t.ha-1 and 4.38 t.ha-1 had the lowest grain yield, respectively. On average, in Dezful and Karaj, application of herbicides in furrow planting method as compared to the bed planting method, had 88 and 80% higher water use efficiency, respectively. In conclusion, for increasing grain yield and weed control in maize (cv. KSC 704), planting of maize as two rows on beds/ in furrows and pre-emergence application of a mixture of atrazine + alachlor at (0.6 + 1.5) kg ai.ha-1 could be recommended.