The Effect of Seeding Rates and Nitrogen fertilizer on Yield and Yield Components of Wheat Cultivars in Corn residue (No Tillage)

Lots of studies have been conducted for increasing the wheat yield per unit area through sustainable agriculture, which is included low tillage and no tillage farming systems. Furthermore, nitrogen is the important element which is used to increase crop yield. On the other hand, if all the required conditions especially cultivar and fertilizer are at optimum level, but density is not appropriate, the maximum yield per unit area will not be achieved. Therefore, this study was conducted to evaluate the effect of seeding rates and nitrogen fertilizer on yield and yield components of wheat cultivars in corn residue. An split factorial experiment in a randomized complete block design with four replications and three factors including cultivar at 2 levels, (Chamran (V1) and Behrang (V2)), seed density at 5 levels (50 (D1), 100 (D2), 150 (D3), 200 (D4), 250 (D5) kg ha-1) and nitrogen fertilizers from urea source at 6 levels (0 (N1), 50 (N2), 100 (N3), 150 (N4), 200 (N5), 250 (N6)) carried out in fall of 2011 – 2012 at Agricultural Farm located south of Dezful. The results indicated that with increasing plant density, the number of spike and biological yield increased, however the number of grain in each spike and thousand seed weight decreased. Moreover, increasing nitrogen application resulted in increasing the number of spike, the number of grain in each cluster, thousand seed weight, biological yield and grain yield. seed consumption over than 100 (kg ha-1) decreased grain yield. In addition, applied nitrogen to 150 (kg ha-1) significantly increased grain yield. The effects of plant density on grain yield illustrated that the highest grain yield was obtained using 100 kg seeds per hectare. Furthermore, there were not any significant differences among 150, 200 and 250 kg seeds per hectare and they were at a lower level of grain yield. In addition, Chamran cultivar, with 413.70 (kg ha-1) average grain yield, was higher in comparison to Behrang cultivar and also the best grain yield was obtained in 100 kg ha-1 of seed density with the average of 5 ton ha-1. In the present experiment, increasing seed rate to 100 kg per hectare, increased grain yield. Grain yield had decreasing trend in higher plant density, probably due to high competition, adverse growing conditions and leaf area index reduction. According to the results of this study, increasing nitrogen to optimal values, which is depending on the climatic conditions in each region, increases grain yield. However higher application of nitrogen fertilizer, will not increase the yield proportionally. Nitrogen application with increasing the number of mature leaves causes increasing the ratio of photosynthesis to respiration, and finally it increases assimilate materials and yield. When nitrogen is higher than optimum level, shoots will over grow, the number of leaves which are in shade will be increased. Furthermore, photosynthesis to respiration ratio will decrease and most of the assimilates will be used by leaves in shadow, thus, the lower assimilates transferred to grain. In general, plant density and nitrogen fertilizer can be used as important factors to increase wheat yield. According to the results of this study, Chamran cultivar had higher grain yield compared with Behrang cultivar. The highest grain yield was obtained in 100 kg per hectare seed density with 250 kg of nitrogen fertilizer per hectare. Since there were no significant differences between 150 and 250 kg of nitrogen fertilizer per hectare, 100 kg seed per hectare and 150 kg nitrogen per hectare can be introduced as the most appropriate treatment to increase the grain yield in this experiment. In this study it was observed that by reducing application of seeds and fertilizer, the grain yield per hectare was not reduced. Therefore, it seems that to produce enough grain yield of wheat, as the main crop in Iran, increasing the consumption of seed and fertilizer per hectare is not necessary. Higher application of fertilizer may increase the costs and environmental risks.