Effect of planting pattern and plant density of maize (Zea mays L.) on the morphophysiological characteristics and growth indices of maize and redroot pigweed (Amaranthus retroflexus L) under competition conditions

To study the effect of integrated planting pattern and plant spacing on competition between maize and redroot pigweed a field experiment was carried out at experimental station of Agricultural College of Ilam University in 2006 growing season. Experimental treatments were arranged as split plot in randomized complete block with three replications. Main plots consisted of planting patterns (single row، rectangular twin rows and zigzag twin rows) and maize plant densities (5. 33، 6. 66، 8. 33، 9. 52، 11. 11 plant. m-2) were randomized in sub plots. Results indicated that leaf area index، total dry matter accumulation and crop growth rate (CGR) of maize increased in all planting patterns، especially zigzag twin rows planting with 11. 11 plant. m-2. However، dry matter accumulation and growth rate decreased in redroot pigweed. In fact، among different maize arrangements، twin rows planting and particularly zigzag twin rows increased grain yield and yield components، on the other hand zigzag twin rows planting arrangement increased competitive ability of maize against redroot pigweed. Zigzag twin rows planting with plant density of 11. 11 plant. m-2produced the maximum grain yield (13632 kg. ha-1)، biological yield (21642 kg. ha-1)، harvest index (63%)، and 1000 kernel weight (440g) as compared to the other treatments. Therefore، the best planting arrangement، based on the finding of this research، is zigzag twin rows planting، i. e. planting density of 11. 11 plant. m-2، because of higher grain yield and more effective weed control.