Effect of Rice Residue Management on Growth and Quantitative and Qualitative Yield of Rapeseed (Brassica napus) Cultivars

One of the problems of agriculture in arid and semi-arid regions is low soil organic matter. Plant residues are a natural and important renewable source of plant nutrients that can be used together with other inputs to improve soil health and improve production. The method of preserving crop residues on the surface and cultivating directly inside the residues with minimal soil disturbance can be an alternative method for burning the residues, especially in summer cultivation. Therefore, in the present study, the effect of different rice residue managements on the growth and quantitative and qualitative yield of rapeseed cultivars was studied.

The experiment was performed as split plot layout based on a randomized complete block design with three replications. The main factor included the management of rice residues at four levels, including 1- According to conventional cultivation,2- Cultivation in plowed land with rice residues, 3- Cultivation in rice residues with 20 cm height, 4- Cultivation in rice residues with 40 cm height and the secondary factor of three rapeseed cultivars included 401, 4815 and okapi cultivars. In conventional cultivation (control), after harvesting the rice, the field was set on fire and after exposing the ground, plowing, disc and plotting of the land were done and planting according to the custom of the region in a row with distant 20 cm was planted. In the management of cultivation in plowed land with rice residues, after harvesting rice, plowing, disc and plot cultivation were done and planting was done in a row according to the custom of the region in a row with distances between planting lines of 20 cm. In the management of cultivation in rice residues with a height of 20 and 40 cm, rice harvesting from a height of 20 and 40 cm above the ground is done manually and then scattering rapeseed seeds similar to seed density in the custom method cultivation and then with the help of chisel plow rapeseed seeds it was mixed with the soil completely superficially at a depth of about 0.5-1 cm.

The results of analysis of variance showed that the effect of rice residue management on plant height, number of branches per plant, number of pods per plant, number of grains per pod, 1000- grain weight, grain yield, oil percentage and grain protein percentage was significant. The effect of cultivar types on number of pods per plant and grain yield was significant but not significant for other traits. Interaction of rice residue management and cultivar type was significant on plant height, number of branches per plant, number of pods per plant, number of grains per pod and yield. The maximum grain yield in the cultivation of plowed land with rice residues in cultivar 4815 by 2449.48 kg/ha and the minimum grain yield in the cultivation of rice residues with a height of 40 cm in cultivar 401 by 1187.41 kg/ha was observed. The maximum oil percentage and grain protein percentage in the cultivation of plowed land with rice residues by 21.62 and 48.16 were observed, respectively and regard to other residue managements were not significant.

In general, the results showed that the rapeseed cultivation in plowed bed along with rice residues is effective in improving most of the growth and yield traits of rapeseed. In addition, cultivar 4815 is more suitable than cultivar 401 and okapi in terms of cultivation in plowed land with rice residues and this cultivar can be recommended for farmers and region.