Plant Productions

Yield gap analysis of rice in Shoaybiyeh, Khuzestan: yield-reducing factors have the greatest contribution to grain yield reduction

Ghazban Anafjeh; Elham Elahifard; Abolfazl Derakhshan; Ahmad Zare

Volume 47, Issue 3 , November 2024, , Pages 425-440

https://doi.org/10.22055/ppd.2024.46453.2153

Abstract

Introduction One of the main issues of crop production in Iran and many countries of the world is the difference between the farmers’ yields (actual yield) and the achievable ... Read More Introduction One of the main issues of crop production in Iran and many countries of the world is the difference between the farmers’ yields (actual yield) and the achievable yields (potential yield). This distance and yield difference is named the yield gap. Therefore, research was conducted with the aim of determining the rice yield gap in Shoaybiyeh region of Khuzestan province. Materials and Methods This research was conducted in 2020 growing season as a survey in 100 rice fields in Shoaybiyeh region of Shushtar county. Comparative performance analysis method was used to determine rice grain yield gap. The modeling of grain production in rice fields was done by examining the relationship between all the investigated variables with the grain yield observed in the fields using progressive stepwise regression method. The production model obtained with this method was able to justify 89% of the grain yield changes of the studied rice fields with the studied variables. Results and Discussion The results showed that there was a gap of about 1495 kg ha-1 between the average yield of farmers (5044.47 kg ha-1) and the achievable yields in the region (6902.61 kg ha-1). From this value of the expected yield gap in the region, the contribution of factors such as the age of the farmer, the intensity of the weed infestation in the fields, the presence of weed in the fields, the use of adjuvants during the spraying operation, the intensity of the infestation of the field with the striped rice stemborer, and the intensity of the infestation of the fields with the blast disease were equivalent to 3.29, 62.29, 2.53, 6.99, 20.22 and 4.68%, respectively. The analysis of rice yield gap showed that the weed infestation of the fields alone accounted for about 62.3% of the yield reduction compared to the achievable yields. In all the studied fields, the weeds of purple nutsedge, junglerice, broadleaf cattail, and johnsongrass were observed and recorded. Due to the lack of diversity in the fields, the model was not able to distinguish the amount of yield loss caused by these weeds. Intensity of weed contamination of rice fields was also observed in only 6% of the fields, and in the remaining 94%, moderate to very high contamination was observed. Some used herbicides such as bensulfuron-methyl and tribenuron-methyl showed a significant negative relationship with grain yields observed in rice fields. Therefore, it seems that farmers should reconsider the use of these herbicides in rice fields. Also, the delay in sowing and laxuary consumption of nitrogenous fertilizers was closely related to the severity of weed infestation and yield reduction. Investigating the relationship between the yields obtained in rice fields and the date of herbicide spraying (31 to 77 days after planting), a significant negative relationship was clearly observed; That is, with the delay in the spraying time and the consequent increase in the competitive ability of weeds, which may be associated with the decrease in the effectiveness of herbicides, yield have decreased linearly. Conclusion In general, among the variables that had a significant impact on the observed yields in the region, except for the age variable of the farmer, all of them were related to yield-reducing factors, including pests, diseases, and weeds. Based on the results, the yield reducing factors, explained about 90% of the yield gap observed in the region.

Investigating the rapeseed yield gap in Dehloran

Marzieh Absalan; Esfandiar Fateh; َAmir Aynehband; Abolfazl Derakhshan

Volume 46, Issue 3 , December 2023, , Pages 455-472

https://doi.org/10.22055/ppd.2024.43006.2082

Abstract

IntroductionAs suitable agricultural land for increasing crop production is decreasing, while the expansion of agricultural land is associated with irreparable damage to the environmen, ... Read More IntroductionAs suitable agricultural land for increasing crop production is decreasing, while the expansion of agricultural land is associated with irreparable damage to the environmen, intensifying sustainability in existing agricultural land is the only way to increase production to meet the increasing demand for food resources. Therefore, investigating the biophysical limitations on yield and estimating yield gaps in the cultivated lands, as well as reducing this gap, is one of the ways to increase the yield per unit area. After soybean, rapeseed is the world's second produced oilseed. Ilam province is one of the most important oilseeds producer regions of the country, including rapeseed, and about 80% of the rapeseed crop of this province is produced in the border city of Dehloran, and this city is one of the pioneer cities and the main pole of rapeseed production in the province. Therefore, according to the importance of rapeseed in Deholran city, this study was conducted with the aim of determining the limiting factors of rapeseed production in Dehloran. Materials and MethodsIn the present study, all the management operations were performed from seedbed preparation to harvesting in 51 farms were recorded through field studies during the years 2021 to 2022. In this study, the yield gap was estimated by the method of yield comparison analysis and borderline analysis, and to determine the yield model, the relationship between quantitative and qualitative variables was measured and yield was evaluated by step-by-step regression method. Results and DiscussionDetermining the limiting factors on rapeseed production in the studied area showed that there was a gap between the actual yield of farmers and the yield predicted by the model of about 833.54 kgha-1, which was the contribution of the variables of potash fertilizer consumption, sulfur consumption, and the number of irrigations. The consumption of micronutrients from this yield interval was equal to 102.99, 118.56, 442.20 and 169.79 kgha-1, which is equivalent to 12.36, 14.22, 53.05 and 37, respectively. 20% of the total yield gap was observed. Gap analysis of rapeseed yield showed that the number of irrigations alone accounts for 53% of yield reduction compared to attainable yields.ConclusionAs, there is a need to irrigate the field in the very early planting date in October, it seems that with better management of rapeseed for this planting date in the region, the occurrence of drought stress can be reduced to the plant and to some extent fill the gap in the existing yield. In addition, 57% of the yield gaps in the region were related to the use of potash, sulfur and micronutrient fertilizers, which can be easily removed this limitations in the fields.

Construction of Critical Nitrogen Dilution Curve Based on Stem Dry Matter in Rapeseed

SeyedAtaollah Siadat; Abolfazl Derakhshan

Volume 45, Issue 1 , May 2022, , Pages 143-156

https://doi.org/10.22055/ppd.2020.31971.1854

Abstract

IntroductionThere are mathematical equations to distinguish nitrogen (N) status based on the concept of critical nitrogen (Nc), the lowest N concentration required to achieve maximum ... Read More IntroductionThere are mathematical equations to distinguish nitrogen (N) status based on the concept of critical nitrogen (Nc), the lowest N concentration required to achieve maximum growth. The Nc demonstrates the ideal N status in crops. Whenever crop N concentration is greater than the Nc, at that time N is in surplus, but if it is less, then N is inadequate. The contribution of the stem dry matter (SDM) toward total crop dry matter is significantly higher than that of other tissues, therefore, it is the most determinant factor for N dilution of the whole plant. The objectives of this research were to construct a Nc dilution curve based on SDM and to evaluate the plausibility of this curve for assessment of the N nutrition status of spring rapeseed. Materials and MethodsA field experiment was conducted with seven levels of N fertilizer application (0, 50, 100, 150, 200, 250 and 300 kg N ha-1) in which the amount of the SDM and stem N concentration (SNC) of two spring rapeseed cultivars (Hyola 401 and Dalgan) were measured during the growing season. The approach proposed by Justes et al. (1994) was used to construct the SDM basis Nc dilution curve. The N nutrition index (NNI) on each sampling date was calculated by dividing actual SNC by stem Nc concentration. The accumulated N deficit (Nand) in rapeseed stems for each sampling date was determined by subtracting the N accumulation in stems under the Nc condition from actual N accumulation in stems under different N fertilizer application rates. Results and DiscussionOverall, both SDM and SNC showed an increasing and decreasing trend with increasing crop age, respectively, regardless of fertilizer treatment. The Nc dilution curve of both cultivars during the growing season was described by the equation Nc = 5.71SDM-0.29. Both NNI and Nand criteria were able to diagnosis the N deficiency or excess in the spring rapeseed cultivars studied. At all of the crop growth stages, there was a significant positive correlation between the difference value of the N application rate (∆N) and the difference value of NNI (∆NNI). For both cultivars studied, however, the positive correlation between ΔN and differences in Nand among N fertilizer treatments (ΔNand) was not significant at early growth stages. In any case, for accurate management of N fertilizer during the growing season, it is sufficient to determine only one of the two NNI or Nand criteria per day from planting to silique formation, and then the N fertilizer required for maximum growth is calculated based on the equations presented to describe the relationships between ΔN and ΔNNI or between ΔN and ΔNand. The most important application of the Nc dilution curve is to determine the N requirement of crops during the growing season under variable field conditions. These curves can be used as ideal and economically efficient tools for accurate management of fertilizer in the field, which is very important from the aspect of environmental protection and human health. Both NNI and Nand were well able to distinguish the N status of spring rapeseed. ConclusionThe present Nc dilution curve based on SDM provides an insight into N nutrition status in spring rapeseed crop and can serve as a novel tool to improve N fertilization management in spring rapeseed.

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Author = Abolfazl Derakhshan

Yield gap analysis of rice in Shoaybiyeh, Khuzestan: yield-reducing factors have the greatest contribution to grain yield reduction

Abstract

Investigating the rapeseed yield gap in Dehloran

Abstract

Construction of Critical Nitrogen Dilution Curve Based on Stem Dry Matter in Rapeseed

Abstract