The Effect of Farming Systems and Wheat Residues Managements on yield and yield components in Brassica Napus in Roumeshagen and chardavol locations in southwest of Iran.

Common tillage practices are known to accelerate soil erosion and reduce the carbon and organic contents of soils, leading to the destruction of the soil structure. Nowadays, soil erosion is considered to be a major challenge to agricultural production. Maintaining adequate quantities of crop residues in the soils is an effective way to overcome the decline in soil quality (Kazemi & Zakeri, 2006). Research conducted in different canola producing regions of the world indicates that the effect of various tillage systems on seedbed preparation for canola has been different, depending on soil type and climate condition. So that some studies recommend the direct seeding using minimum tillage and the others recommend deep soil plowing by moldboard for increasing canola yield.(Reshad Sadeghi et al., 2006). This research was aimed to investigate the effects of different farming systems and wheat residue management on yield and yield components in autumn canola.
Materials and Methods
A strip plot design was adopted in a randomized complete block layout with three replications in 2015 and 2016 cropping seasons in two locations (Sarableh, and Roumeshgan) in the southern west of Iran. The first experimental factor consisted of three farming systems: low input (one-time disk plowing + 25% of the crop nutrient requirement as chemical fertilizer + two times weed manual control), medium input (one-time moldboard plowing, one-time disk plowing 50% of the crop nutrient requirement as chemical fertilizer+ once weed manual control+ one-time weed control by herbicide) and high input (two times moldboard plowing +two times disk plowing + 100% of the cop nutrient requirement as chemical fertilizer+ two times weed control by herbicide). The second experimental factor was wheat residues management at four levels of 0 as control, 2, 4 and 6 tons/h. The first and second factors were considered as vertical and horizontal factors.
Result and Discussion
The results showed that the highest leaf area indices were obtained with high input farming system under 2 and 4 t/ha of wheat residues in Sarableh and Roumeshgan,regions, respectively. The highest and lowest accumulation of dry matters were obtained in high input farming system under 4 t/ha of wheat residues and, low input farming system under 6 t/h of wheat residues at both locations, respectively.
The interaction effect of farming systems and wheat residues was significant on number of silique per plant and grain yield. This results showed that in low-input management conditions, by adding each level of wheat residue to soil, seed yield decreased, while in medium and inward systems, adding two and Four tons of plant remains showed a positive effect on the growth characteristics and yield of rapeseed. The results showed that the application of wheat residues due to its high carbon content may increase the soil microbial activity and in such condition, nitrogen stored in microorganisms bodies and then is absorbed by plant, especially in the early stages where plant is faced with nitrogen deficiency (Turmel et al., 2015). Autumn plants, including canola, in the absence of nitrogen, cannot complete rosette growth in the early stages of growth, and hence they will be less developed during the growing season. Therefore, in low-input systems, application of high levels of wheat residues resulted in the reduced biological and grain yield in canola as a result of nitrogen organification.