Effect of plant number and urea fertilizer on agronomic characteristics of corn hybrids and dry matter accumulation in pigweed (Amaranthus retroflexus L.)

In order to investigate the effect of density and urea fertilizer on agronomic characteristics of corn hybrids and dry matter accumulation in pigweed.

The Experimental during two cropping years, a factorial split plot was used as a randomized complete block design with four replications. The main factors included corn cultivars (Single Cross hybrids of 370 and 704) and sub factors included different levels of corn densities (60000, 70000, 80000 and 90000 plant/ha) and different levels of nitrogen fertilizer including 200, 300, 400 and 500 Kg.ha-1.

The results showed that effect of density on all traits was significant, but the effect of cultivar on chlorophyll and nitrogen effect on number of ear per square meters were not significant. Corn cultivar of 704 had significantly higher number of grain per spike, 1000-grain weight and grain yield compared to cultivar 370 but the number of spikes per square meters was significantly lower than that of cultivar 370 and there was no significant difference in chlorophyll index between the two cultivars. The highest grain yield was obtained at densities of 80000 plants pet hectare and application of 400 kg N per hectare. The lowest weed biomass was obtained at density of 90,000 plant/ha and application of 200 kg N per hectare. However, cultivar 704 significantly decreased pigweed biomass compared to cultivar 370.

Based on the results, it is recommended that farmers in Miandab region use 80,000 plant/ha and 400 kg nitrogen per hectare for optimum yield.