Evaluation of wheat (Triticum aestivum L.) yield gap in Golestan province of Iran using comparative performance analysis method

In this study, all information about management practices in wheat crop were recorded and measured (including 250 variables) from 684 irrigated and rainfed wheat fields during two growing seasons of 2013-2014 and 2014-2015 in Golestan province, Iran. Wheat production in Golestan province can be divided into three production systems including low- yielding rainfed, high- yielding rainfed and irrigated wheat. This study covered 216 fields in low-yielding rainfed, 119 fields in high- yielding rainfed and 349 fields in irrigated wheat and evaluated using comparative performance analysis (CPA). In each system one production model was identified and according to this model, potential yields of wheat were estimated. The results showed that while the average yield of farmers were 1966, 3985 and 3936 kg kg.ha-1, they could harvest up to 5025, 7954 and 8029 kg.ha-1 in low-yield rainfed, high- yielding rainfed and irrigated farms, respectively, hence there were yield gaps of 60, 50 and 51%, respectively. The most important factors found for these yield gaps in low- yielding rainfed system included: use of no-till planter (32%), seedbed prepartation (17%), foliar fertilization (15%), chisel (15%), herbicide (13%) and nitrogen fertilizer (9%). The most important factors for yield gaps in high- yielding rainfed system included: legume rotation (26%), field size (21%), nitrogen fertilizer (15%), potassium fertilizer (12%), manure fertilizer (11%), subsoiler (10%) and fungicide (5%). However, the most important factors for yield gaps in irrigated wheat system included: irrigation (27%), nitrogen fertilizer (25%), sowing date (20%), use of N8720 cultivar (10%), subsoiler (9%) and using of furrower (8%). It was concluded that with proper management of field and considering the listed yield gaps factors in each system, it would possible to obtain higher yield levels comparing with current yield levels that farners harvest. The amount of yield increased will be about 3000 kg.ha-1 in low- yielding rainfed wheat system and about 4000 kg.ha-1 in high- yielding rainfed wheat and irrigated wheat systems in comparison with current yield levels.