پژوهشهای زراعی ایران (Dec 2021)
Response of Dryland Winter Bread Wheat (Triticum aestivum L.) Genotypes to Nitrogen Application under Supplemental Irrigation
Abstract
IntroductionWheat is the most important staple food crop in the world as well as in Iran. About 63% of the wheat cultivation areas and 40% of its production is under dryland conditions in Iran. Water and nitrogen are the two most important limiting factors for wheat production in dryland conditions. However, the role of water is about 2.3 to 3.9 times the nitrogen because the water deficiency limits the absorption of the nutrients especially nitrogen. Nitrogen deficiency is very critical than the other nutrients for plant growth in the arid and semi-arid region. Therefore, applying supplemental irrigation (wherever it is possible) at the critical crop growth stages along with nitrogen fertilizer will increase wheat production by increasing the greenness and photosynthetic activity of the plant. In this regard, the cereal department of Dryland Agricultural Research Institute (DARI) has introduced different new wheat cultivars for supplementary irrigation conditions in the last decade. Hence, evaluating the response of bread wheat genotypes to different rates of nitrogen under supplementary conditions, determining the relationship between nitrogen requirement and water status of varieties as well as the relationship between these factors with yield components and effective traits to improve the quantity and quality of the crop, are the key factors for wheat production in dryland areas.Materials and MethodsA field experiment was conducted to evaluate the response of dryland wheat (Triticum aestivum L.) genotypes to different rates and timing of nitrogen application under supplemental irrigation in 2018-2020 cropping seasons at DARI, Maragheh, Iran. The experimental design was a randomized complete block with three replicates based on split-split-split plot arrangement consisting of two irrigation treatments (50 mm in planting time and 50 mm in planting time + 30 mm at booting stage) in the main plot; nitrogen application time (fall application and split 2/3 in planting time + 1/3 in booting stage) in the sub-plot; four nitrogen rates (0, 40, 80 and 120 kg.ha−1) in the sub-sub-plot and three genotypes (Takab, Hoor and Griset-16 (sup-96-18) in the sub-sub-sub plots. The soil samples were collected from 0-25 cm depth before the sowing and were determined soil texture (loam to silty clay), pH, EC, Organic carbon, P (Olsen method), K (Sodium bicarbonate method), micronutrients (Fe, Mn, Zn, and Cu) by DTPA method. Because all these elements were more than critical levels (P: 10 mg.kg-1; K: 250 mg.kg-1; Fe: 5 mg.kg-1; Mn: 11 mg.kg-1; Zn: mg.kg-1 and Cu: 1.4 mg.kg-1) in the soil, only nitrogen rates were used in the experiment (Feiziasl et al., 2004; Feiziasl et al., 2009). The data was collected for biological and grain yield, yield components, plant height, spike length, nitrogen use efficiency (NUE), water use efficiency (WUE), and seed quality (Seed protein, Number of Zeleny Grain hardness, Grain starch). The GenStat14 software was used to combined analysis of variance and mean comparison of traits by Duncan's Multiple Range Test. The CurveExpert 2.6.3 software was used to fit equations, Excel to draw charts and Xlstat2016 software to do principal component analysis.Results and DiscussionThe first year of the experiment produced a significantly higher yield (P≤0.05) due to higher precipitations. Two stages of supplementary irrigation significantly increased biological yield, grain yield, and straw yield by 2975, 895, and 2069 kg ha-1, respectively. Although fall and split application of nitrogen had no significant effect on yield and yield components, fall application increased grain yield, NUE, and WUE by 195 kg.ha-1, 1.97 kg.kg-1, and 0.5 kg.ha-1.mm-1, respectively. Nitrogen application increased grain yield components for which the number of spikes per square meter was increased more than the two others. The nitrogen requirement of dryland wheat was determined 70 kg.ha-1 under single irrigation at planting time by fertilizer placement method while it was determined 90 kg.ha-1 for two stages supplementary irrigation for which 2/3 of it was applied at fall (planting time) and 1/3 at booting stage with supplementary irrigation.Conclusion Although the interactions of irrigation, nitrogen rates, application times, and genotypes factors on grain yield were not significant, supplemental irrigation and nitrogen application could increase the yield production of dryland wheat genotypes.
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