Aiming at the problems of low photosynthetic performance and yield decline of maize leaves caused by large amount of plastic input and extreme high temperature in traditional maize planting in oasis irrigation area, the photosynthetic physiological mechanism of maize during grain filling period under two years of plastic mulching was studied, so as to provide the theoretical basis for the construction of high grain yield technology of plastic reduction in oasis irrigation area.

In 2013, a randomized block experiment was conducted in the oasis irrigation area of the Hexi Corridor. According to the duration of plastic mulching, three treatments were formed: no-tillage with plastic re-mulching and using (NTP), no-tillage in autumn and plastic mulching in spring (RTP), and conventional tillage with annual new plastic mulching (CTP, as the control). The response of chlorophyll content, gas exchange parameters, key enzyme activities of photosynthetic physiology, relative gene expression and key protein content of maize leaves to different plastic utilization methods was explored.

Different plastic utilization methods promoted the increase and stability of maize yield by regulating the photosynthetic physiological characteristics of maize filling stage. Compared with CTP, chlorophyll a and b in NTP filling stage increased by 15.1% and 8.3% on average, respectively, indicating that NTP treatment was beneficial to maintain the chlorophyll content of maize, thus effectively delaying the degradation of chlorophyll and promoting the photosynthesis of maize. Compared with CTP treatment, the net photosynthetic rate and transpiration rate under NTP increased by 25.2% and 11.5%, 20.0% and 12.2%, respectively, in the middle and late stages of grain filling, indicating that NTP treatment was beneficial to regulate the gas exchange parameters of maize during grain filling stage and enhanced the photosynthesis of maize during grain filling stage. At the same time, NTP maintained higher photosynthetic physiological key enzyme activity, relative gene expression and key protein content during the filling stage, which provided a guarantee for the improvement of photosynthesis. Compared with CTP, the activities of PPDK, PEPC, and Rubisco in maize leaves treated with NTP increased by 18.9%, 20.0%, and 30.6% on average, respectively, the gene expression of pepc, ppdk, and rub in maize leaves increased by 22.1%, 75.8%, and 70.6%, respectively, and the protein content of D1 and D2 in photosynthetic reaction center increased by 12.6% and 13.2%, respectively. Compared with CTP treatment, the activities of PPDK, PEPC and Rubisco in maize leaves under RTP increased by 15.6%, 16.4%, and 19.2%, respectively. The expression levels of pepc, ppdk, and rub genes in maize leaves increased by 13.6%, 53.9%, and 57.7%, respectively. The content of D1 protein in photosynthetic reaction center increased by 10.1%. In addition, the grain yield of NTP was 5.2%, 6.0%, and 5.3% higher than that under CTP in 2021, 2022, and 2023, respectively. The grain yield of RTP was only 5.2% higher than that under CTP in 2022.

No-tillage with plastic re-mulching and using was an effective cultivation and management measure to maintain high photosynthetic performance, reduce plastic input, and increase maize yield in the northwest oasis irrigation areas.

In terms of the issues of yield instability and quality deterioration caused by improper water and fertilizer application, the effects of reduced irrigation combined with organic and inorganic nitrogen fertilization on the yield and quality of silage maize in arid irrigated regions of Northwest China were investigated, so as to identify optimal water and fertilizer management practices for achieving high yield and superior quality in silage maize cultivation in the irrigated areas.

From 2021 to 2022, a field experiment based on two-factor split-plot design was carried out at the Oasis Agricultural Experimental Base of Gansu Agricultural University. The main factor was two irrigation levels, respectively, including I1 conventional irrigation reduction 20% irrigation was 324 mm, and I2 conventional irrigation is 405 mm, and drip irrigation was used. The sub-factor included five different fertilization regimes: F1, 100% chemical nitrogen fertilizer; F2, 75% chemical nitrogen fertilizer+25% organic fertilizer; F3, 50% chemical nitrogen fertilizer+50% organic fertilizer; F4, 25% chemical nitrogen fertilizer+75% organic fertilizer; and F5, 100% organic fertilizer. The effects of different water and fertilizer management practices on the yield, grain quality, and stalk quality of silage maize were analyzed, and the comprehensive evaluation of the yield and quality of silage maize was performed using factor analysis.

Reducing irrigation alone led to a decrease in the yield and quality of silage maize. However, the combined application of organic-inorganic nitrogen fertilizers helped to enhance the potential for simultaneously improving both yield and quality under reduced irrigation conditions. Notably, the combination of reduced 20% irrigation with 75% chemical nitrogen fertilizer+25% organic fertilizer (I1F2) demonstrated significant advantages. The I1F2 treatment significantly increased fresh and hay yields of silage maize, with fresh and dry grass yields improving by 9.9% and 12.7% over conventional irrigation combined with 100% chemical nitrogen fertilization (the control treatment, I2F1), respectively. Meantime, the I1F2 treatment was able to maintain a relatively high grain and stover quality of silage maize. Compared with I2F1, the I1F2 treatment increased protein and fat contents of grain by 17.4% and 20.5%, and increased essential amino acids content too, with phenylalanine, valine, leucine, isoleucine, tryptophan, threonine, lysine, and methionine rose by 17.4%, 13.9%, 19.4%, 17.9%, 23.1%, 30.0%, 44.5%, and 22.0%, respectively. The I1F2 treatment increased crude protein, crude fat, and soluble sugar contents in the stover by 13.9%, 19.1%, and 15.6% over I2F1, respectively, while decreasing neutral detergent fiber content by 13.5%, thereby improving relative feed value by 14.0%. Factor analysis also revealed that the I1F2 treatment had the highest composite applicability index, which was beneficial for increasing both the yield and quality of silage maize.

The combination of 20% reduced irrigation with 75% chemical nitrogen fertilizer+25% organic nitrogen fertilizer was the optimal water and nitrogen management practice for simultaneously enhancing both the yield and quality of silage maize in the Northwest irrigation areas.

Aiming at the problems of large amount of nitrogen fertilizer input, low utilization rate and single fertilizer source in traditional spring wheat planting in the oasis irrigation area of Northwest China, the effects of multiple cropping green manure after spring wheat on photosynthetic source, growth characteristics and yield of spring wheat under the condition of reduced nitrogen application were studied, with a view to provide the technical support for the construction of a nitrogen-saving and high-yield green planting model of spring wheat in the experimental area.

The split plot experiment was carried out in the oasis irrigation area of Hexi Corridor from 2021 to 2023. The main area was set up with two planting modes: post-wheat fallow (W) and post-wheat multiple cropping of hairy leaf (W-G), and the split plot was the traditional full nitrogen application of 100% (N1, 180 kg·hm^-2), reduced nitrogen application of 15% (N2, 153 kg·hm^-2) and reduced nitrogen application of 30% (N3, 126 kg·hm^-2). The photosynthetic source, stay-green of leaves, growth characteristics and yield performance related indicators of spring wheat under different treatments were measured and calculated. The Logistic equation of dry matter accumulation, the correlation between different indicators and the compensation index were constructed. The objective was to explore the compensation effect of multiple cropping green manure on the growth and yield of nitrogen-reduced spring wheat.

Post-wheat multiple cropping of green manure could compensate for the loss of photosynthetic source, growth characteristics and yield caused by nitrogen reduction to a certain extent. Among them, the compensation effect was the best under the condition of multiple cropping green manure after spring wheat combined with 15% nitrogen reduction (W-GN2), which showed super compensation and equal compensation effect. Multiple cropping of green manure significantly increased leaf area index, leaf area duration and stay-green of leaves in spring wheat at the late reproductive stage. Compared with the traditional post-wheat fallow total nitrogen fertilization (WN1), W-GN2 increased the average leaf area index, leaf area duration and stay-green of leaves by 17.7%, 17.5% and 7.6% on the 75-90 days after seedling, respectively. W-GN2 optimized the growth characteristics of spring wheat. Compared with WN1, the average dry matter accumulation, the maximum growth rate of dry matter and crop growth rate under W-GN2 increased by 6.2%, 6.9% and 5.1%, respectively, and the net assimilation rate decreased by 6.2%. Due to the compensation of multiple cropping green manure for photosynthetic source and growth characteristics, the photosynthesis, population growth and material accumulation rate of spring wheat remained high in the late growth stage, which was conducive to the improvement of grain yield. The grain yield under W-GN2 was 14.7% higher than that under WN1, which was mainly attributed to the compensation of the spike number, 1000-grain weight and harvest index by multiple cropping green manure, and W-GN2 was 6.5%, 6.9% and 13.2% higher than that under WN1, respectively. According to the correlation analysis, it was found that W-GN2 treatment had better performance in photosynthetic source, growth characteristics and grain yield formation, and mainly promoted the formation of yield by compensating the photosynthetic source of spring wheat.

Multiple cropping of hairy vetch after spring wheat with 15% reduction of nitrogen application could be used as a perfect production technology to regulate the photosynthetic source and growth characteristics of spring wheat in the northwest oasis irrigation area to achieve nitrogen saving and yield increase.