عنوان مقاله [English]
Background and objectives: One of the main problems in crop production in Iran is the difference between actual yield and attainable yield which is called yield gap. Thus, identifying yield constraints and yield gap are important. Estimation the amount of yield gap and determination of it’s causes requires using proper methods. Boundary line analysis is a statistical method that can quantify the response of yield to an environmental or management factors in a situation in which other parameters are variable. Indeed, this method is able to determine the response of yield to a desired factor while other factors are appropriate and done to determine factors and variables influencing the yield reduction.
Materials and methods: The objective of this study was to evaluate the gap yield of cotton cultivation during 2014 and 2015 in the villages of Aq-Qala and Ali Abad Katul cities,in the Golestan province. The statistical community was cotton farmers of the two Regions. One hundred farmers were selected randomly. Management factors consisted of nitrogen and phosphorus (P2O5) used as a base fertilizer, seed rate, density, irrigation frequency, the planting and harvest dates. By drawing distribution of the yield data against different variables management, has been chosen the highest yield of any inputs or management at different levels.
Results: The results showed there is a 1425 kg.ha-1 difference (gap) between actual yield (average farmers' yield) and attainable yield (maximum farmers' yield). The results showed that 80 percent of farms studied in terms of planting date, 70 percen in nitrogen, 64 percent in phosphorus, 63 percent in seeding, 71 percent in density, watering 74 percent and 16 percent of harvest dates were outside the optimal. The results show that while the average yield of farmers is 2657 kg.ha-1, they can achieve up to 4082 kg.ha-1 by improving their agricultural management. For this purpose, the following should be considered: (1) using at least 65 kg of N fertilizer per hectare, (2) using at least 40 kg of P2O5 per hectare as a base fertilizer (3) at least four irrigations (4) two times weeding (5) plant density of 7 to 8 plant in per m2 (6) planting date the late of April and (7) harvest date the early of October and (8) seed rate 50 Kg.ha-1.
Conclusion: The yield gap of the study area farms was about 35 percent and with improving some of the management practices can increase cotton yield. Boundary line analysis in yield gap studies could clearly show the responses of yield to management factors and by using these responses can be define the best management to achieve the highest yield.