In arid regions, supplemental irrigation and fertilization are the major driving factors for sustaining crop production. With the increasing water scarcity, rising fertilizer costs, and growing environmental concerns, identifying appropriate irrigation and nitrogen (N) amounts for simultaneously improving resource use efficiency and yield benefits is essential for sustainable crop production in arid regions. A two-year field study was conducted in the arid region of Northwest China to evaluate the effects of reduced irrigation and N treatments, including W80F75 (600 mm irrigation and 225 kg N ha−1), W80F50 (600 mm irrigation and 150 kg N ha−1), W60F75 (450 mm irrigation and 225 kg N ha−1), and W60F50 (450 mm irrigation and 150 kg N ha−1) on resource use efficiency, forage yield (DM), forage nutritive values, grain yield, and economic benefit of spring wheat in comparison with the farmers' management practice (W100F100, 750 mm irrigation and 300 kg N ha−1). Results indicated that moderately reduced irrigation and N (W80F75) significantly improved the forage nutritive quality, evident by high crude protein yield, relative feed value, digestible dry matter, dry matter intake, total digestible nutrients, and net energy for lactation. No significant difference in DM yield was observed between W100F100 and W80F75 treatments during both years. However, the grain yield for W80F75 treatment was 12.9 % greater than that of W100F100 in 2015. In addition, W80F75 treatment increased the resource use efficiency, net returns, and cost-befit ratios by reducing the input amounts while maintaining comparable yields to that of W100F100. However, the W80F50, W60F75, and W60F50 treatments significantly decreased the DM, grain yield, nutritive values, resource efficiency and economic benefits of spring wheat compared to W80F75. Therefore, the application of 600 mm irrigation and 225 kg N ha−1 to spring wheat is an appropriate management practice for reducing inputs while achieving high resource use efficiency, forage quality and economic benefits without compromising the yield of spring wheat in the arid region of Northwest China.
High external nitrogen (N) inputs can maximize maize yield but can cause a subsequent reduction in N use efficiency (NUE). Thus, it is necessary to identify the minimum effective N fertilizer input that does not affect maize grain yield (GY) and to investigate the photosynthetic and root system consequences of this optimal dose. We conducted a 4-year field experiment from 2014 to 2017 with four N application rates: 300 (N 300 ), 225 (N 225 ), 150 (N 150 ), and 0 Kg ha −1 (N 0 ) in the Northwest of China. GY was assessed by measuring the photosynthetic capacity and root system (root volume, surface area, length density and distribution). Grain yield decreased by −3%, 7.7%, and 21.9% when the N application rates decreased by 25%, 50%, and 100% from 300 Kg ha −1 . We found that yield reduction driven by N reduction was primarily due to decreased radiation use efficiency (RUE) and WUE instead of intercepted photosynthetically active radiation and evapotranspiration. In the N 225 treatment, GY, WUE, and RUE were not significantly reduced, or in some cases, were greater than those of the N 300 treatment. This pattern was also observed with relevant photosynthetic and root attributes (i.e., high net photosynthetic rate, stomatal conductance, and root weight, as well as deep root distribution). Our results suggest that application of N at 225 Kg ha −1 can increased yield by improving the RUE, WUE, and NUE in semi-arid regions.
Melatonin is an important biologically active hormone that plays a vital role in plant growth and development. In particular, it has been investigated for its roles in abiotic stress management. The current experiment was carried out to investigate the protective role of melatonin in photosynthetic traits and the antioxidant defense system of maize seedling under drought stress. Maize seedlings were subjected to drought stress (40-45% FC) after two weeks of seedling emergence, followed by a foliar spray (0, 25, 50, 75 and 100 µM) and soil drench of melatonin (0, 25, 50, 75 and 100 µM). Our results indicated that drought stress negatively affected maize seedling and decreased plant growth and development, biomass accumulation, reduced chlorophyll, and carotenoid content, and significantly declined photosynthetic rate and stomatal conductance. On the other hand, reactive oxygen species, soluble protein, and proline content increased under drought stress. However, the application of exogenous melatonin reduced the reactive oxygen species burst and enhanced the photosynthetic activity by protecting from damages through activation of various antioxidant enzymes under drought stress. Foliar application of 100 µM and soil drench of 50 µM melatonin was the most effective treatment concentrations under drought stress. Our current findings hereby confirmed the mitigating potential of melatonin application for drought stress by maintaining plant growth, improving the photosynthetic characteristics and activities of antioxidants enzymes.
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