Evaluation of Rapeseed Growth and Yield under Nitrogen Fertilizer in Rotation with Corn and Chickpea

Over the past decades, the economic benefit has prompted farmers to grow rapeseed. Consequently, the global rapeseed production increased considerably, and today the crop is grown in shorter rotations than ever before. Rapeseed crops usually yield more if grown after other species than when grown after rapeseed. Crop rotation is a succession of crops grown on the same land. Pulses in crop rotations can improve the productivity of subsequent crops due to increased soil available N and other agronomic benefits. Also, Legume plants can promote C storage by enhancing the formation and stabilization of soil aggregates that protect soil organic C from mineralization. In order to evaluation of rapeseed growth and yield under nitrogen fertilizer and pre-cropping with corn and chickpea crops, an experiment was conducted.

A factorial experiment was designed based on randomized complete blocks with three replications and implemented on a sandy clay soil during 2012-13 and 2013-14 growing seasons, at the Agricultural Research Station, Faculty of Agriculture, University of Bu-Ali Sina, Hamedan, Iran. The first factor consisted of chickpea and corn (forage) and the second factor was urea fertilizer levels of 0, 40, 80, 120, 160 and 200 kg/ha. Harvest operation was done in July 2013 and 2014. Random samples 2 m2 areas were harvested by cutting the stems near ground level to determine the crop grain and straw yield. Evaluated traits include plant height, grain yield components, biological and grain yield, harvest index, chlorophyll index and percentage of grain protein and oil. SAS procedures and programs were used for the analysis of variance (ANOVA) calculations.

The results showed that all of the evaluated properties of rapeseed affected by pre-cropping and nitrogen fertilizer treatments. But, none of the rapeseed traits do not affect by pre-cropping × nitrogen fertilizer. The highest biological yield and grain yield and protein percentage were observed in chickpea pre-cropping treatment (about 924 and 263 g m-2 and 22.29%, respectively). Chickpea pre-cropping treatment increased rapeseed biological yield and grain yield and protein percentage about 14, 13 and 15 percent in comparison to corn pre-cropping treatment. Pay attention to the improved physicochemical conditions of the soil after cropping legumes such as chickpea, it is normal to improve the growth and yield characteristics of the next crop (in this study, rapeseed). Among the nitrogen fertilizer levels, the lowest rapeseed biological yield and grain yield and protein percentage (about 567 and 125 g m-2 and 19.05%, respectively) were achieved at 0 kg ha-1 N fertilizer consumption. Also, the highest rapeseed biological yield and grain yield and protein percentage (about 1311 and 342 g m-2 and 21.06%, respectively) were observed at 200 kg ha-1 N fertilizer consumption, but it had no significant difference with 160 kg/ha treatment. One of the most well-known effects of nitrogen fertilizers increased the properties of crop growth. In this study, rapeseed growth and yield characteristics such as plant height, chlorophyll index, grain yield components, biological and grain yield, harvest index, and percentage of grain protein and oil increased due to urea application.

It seems that in rapeseed farming, legumes pre-cropping such as chickpea pre-cropping is a good solution to reduce the use of nitrogen fertilizers and to contribute to environmental health. Also, attention to optimum fertilizer levels and non-overuse of fertilizers will contribute to agricultural sustainability.