پديد آورندگان :
آبروان، پيام دانشگاه گيلان - دانشكده علوم كشاورزي - گروه زراعت و اصلاح نباتات، رشت، ايران , سلطاني، افشين دانشگاه علوم كشاورزي و منابع طبيعي گرگان - گروه زراعت، گرگان، ايران , مجيديان، مجيد دانشگاه گيلان - دانشكده علوم كشاورزي - گروه زراعت و اصلاح نباتات، رشت، ايران , محسن آبادي، غلامرضا دانشگاه گيلان - دانشكده علوم كشاورزي - گروه زراعت و اصلاح نباتات، رشت، ايران
چكيده لاتين :
Introduction: Oilseed rape (Brassica napus) is one of the most important oil plants. While a major portion of
vegetable oil is needed from outside suppliers, oilseed rape, because of its high yield, can play a critical role in
increasing oil and meal production to meet domestic demands. Golestan Province, especially the eastern part, is
one of the most important oilseed rape production areas in Iran. The yield of oilseed rape in this region often
averages less than 2 t ha-1. The estimation of yield gap and the determination of the responsible factors are a good
approach to improve farmers’ average yield. The present study aims to use the Comparison of Performance
Analysis (CPA) method to estimate oilseed rape yield gap in eastern Golestan and to quantify the contribution of
each factor to this yield gap in order to reduce yield limitations and improve farmers’ yield.
Materials and methods: To identify the limitations of production management, this study was carried out in the
2013-14 and 2014-15 growing seasons. The study was executed in Gonbad, Kalaleh and Galikash, the main oilseed
rape production areas in eastern Golestan. In the two years studied, 332 farms were evaluated. The study focused
on factors of management methods; soil factors were not considered. All data collected on farm management were
analyzed for each city and then for the entire surveyed region with stepwise regression and the CPA method
(Torabi,et al., 2011; Nekahi, et al., 2014). Thus, yield gap was obtained as the difference between potential yield
and the actual average yield of local farmers (Van Ittersum and Cassman, 2013).
Results and discussion: Whilst actual yield was 1,081 in Gonab, 1,456 in Kalaleh and 1,728 kg ha-1 in Galikash,
the results showed the attainable yield could have been 3,032, 3,516 and 4,032 kg ha-1 in these areas. Thus, the
yield gap was 1,951, 2,060 and 2,304 kg ha-1 . The actual yield in the eastern part of the province was estimated at
1,417 kg ha-1, whereas attainable yield could have been 4,800 kg ha-1, resulting in a yield gap of 3382 kg ha-1. The
application of nitrogenous fertilizer was one of the main reasons for yield gap in all the surveyed regions. It reduced
yield by 25% in this part of the province. Sulfur fertilizer caused 16 percent of the yield gap. Weeds were the other
reason. The lack of weeding was responsible for 16% of the yield gap and the failure to apply Lontrel for the
management of weeds for 12%. Disease outbreak was another cause. The application of fungicides offsets 16% of
the yield limitation. Seed rate, 6%, and sowing date, 4%, also contributed to the gap. Cultivar and seed treatment
were each responsible for less than 2%.
Conclusion: Weed management, disease, seeding rate, sowing date, cultivar, and seed treatment, were the main
causes of yield gap. Therefore with better management and optimal use of nitrogen and sulfur applications, oilseed
rape yield can be increased by as high as 3,382 kg ha-1
