关键词: 秸秆还田, 施氮量, 光合特性, 叶绿素荧光, 产量

Abstract: We examined the effects of straw returning and nitrogen application rates on the photosynthetic and fluorescence characteristics in flag leaves and grain yield of wheat (Luohan 22) in drylands, with an experiment following split-plot design. The main plot treatments were straw returning, namely S₀(no straw returning) and S₁(total straw returning with the amount of 9000 kg·hm^-2). The subplot treatments were five nitrogen application rates of 0, 120, 180, 240, and 300 kg·hm^-2, represented by N₀, N₁, N₂, N₃, and N₄ respectively. We measured the photosynthetic and chlorophyll fluorescence parameters in flag leaves at 0, 7, 14, 21, and 28 days after flowering, as well as the final yield and yield components. The results showed that net photosynthetic rate, transpiration rate, stomatal conductance, and photochemical quenching of all treatments showed a decreasing trend with growth period progressing. The maximum photochemical quantum yield and electron transport rate first increased and then decreased with the growth process, peaking at 7 and 14 days after flowering, respectively. The non-photochemical quenching coefficient showed an increasing trend as the growth period progressing. At each nitrogen application level, net photosynthetic rate, transpiration rate, stomatal conductance, photochemical quenching, maximum photochemical quantum yield, and electron transport rate at each measurement period were all higher in S₁ than in S₀. Under the same straw returning treatment, these parameters first increased and then decreased with increasing nitrogen application rate, with the highest value in N₃. Compared with S₀N₃, the indicators of S₁N₃ increased by 4.3%, 6.1%, 2.6%, 5.9%, 3.9% and 11.0%, respectively. The non-photochemical quenching coefficient was higher in S₀ than in S₁ at the same nitrogen application rate. Under the same straw returning conditions, it first decreased and then increased with increasing nitrogen application rates, with the highest value in N₀. The non-photochemical quenching coefficient in S₁N₃ was 4.1% lower than that in S₀N₃. The effective panicle numbers, grains per panicle, 1000-grain weight, and yield of wheat were all higher in S₁ than in S₀ under the same nitrogen application rate. Under the same straw returning treatment, these parameters first increased and then decreased with increasing nitrogen application rates. Among all the treatments, S₁N₃ gained the highest spike numbers, grains per panicle, 1000-grain weight, and yield, which was 2.1%, 2.7%, 3.9%, and 5.2% higher than that under S₀N₃, respectively. Similarly, the economic benefit and cost-benefit ratio reached their highest in S₁N₃, at 12629 yuan·hm^-2 and 198.1% respectively, both being 8.0% higher than S₀N₃. Therefore, straw returning combined with nitrogen application rate at 240 kg·hm^-2 is a suitable cultivation practice for dryland wheat in the western Henan Province and regions with the same conditions.

Key words: straw returning, nitrogen application rate, photosynthetic characteristics, chlorophyll fluorescence, yield