Following the implementation of China’s “Zero-Growth Action Plan on Fertilizers” in 2015, research has predominantly focused on replacing synthetic fertilizers with organic amendments to address over-fertilization concerns. However, insufficient attention has been given to the sustainable supply capacity of soil residual nutrients accumulated from previous over-fertilization. To investigate the transformation dynamics and supply capacity of residual nutrients during crop production, a six-year field experiment was conducted in the dryland wheat growing region of China’s Loess Plateau. Five treatments were established: farmer’s fertilization (FF), regulated fertilization (RF), regulated fertilization without N (RF-N), regulated fertilization without P (RF-P), and regulated fertilization without K (RF-K). The study examined wheat yield formation, variations and stability of soil N, P, and K fractions, and their correlations with yield. Results indicated that wheat yield sensitivity to nutrient deficiency followed the sequence N>P>K. During the six-year period, the average yield under RF-N decreased by 22.0% compared to RF, showing statistical significance (P<0.05). Mineral N, light fraction organic N (LFON), and heavy fraction organic N (HFON) in RF-N showed progressive decline relative to RF and initial 2018 levels. Dissolved organic N (DON) and easily oxidizable organic N (EON) in RF-N initially decreased but subsequently increased due to N fraction transformations. Under RF-P, H2O-P, NaHCO3-P, and NaOH-P levels decreased by 40.0, 51.5, and 10.3% respectively (P<0.05) compared to the RF treatment, while HCl-P, residual P, and total P (TP) remained stable. The absence of K application (RF-K) reduced water-soluble K (WSK) by 10.9% (P<0.05), whereas exchangeable K (EK), non-exchangeable K (NEK), mineral K (MK), and total K (TK) showed no significant changes compared to the RF treatment. These findings demonstrated that the soil nitrogen pool exhibits lower stability compared to phosphorus and potassium pools during continuous residual nutrient supply. Notably, NO3-N and LFON significantly influenced spike number and kernels per spike, driving yield formation. This research advances our understanding of sustained residual nutrient supply capacity in soil and provides theoretical foundations for optimizing fertilization strategies in dryland agroecosystems.
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The irrigation system for spring maize production in the eastern Loess Plateau is unclear. In view of this, the effects of straw return and post-silking irrigation on grain yield and use efficiency of water and nitrogen of spring maize were studied in order to explore effective management measures to achieve sustainable and efficient utilization of water and nitrogen in spring maize in the region, so as to provide a theoretical basis for the high yield, high resource efficiency, and environmentally friendly agricultural sustainable development of spring maize in the region.
Based on a 7-year long-term positioning experiment (2014-2020), a field experiment was carried out from 2021 to 2022. A split design was applied for the treatments, the main factors included straw returning (R) and no straw returning (U), and sub-factors included five post-silking irrigation gradients (I0, I50, I100, I150, and I200 mm). The correlation between dry matter accumulation at post-silking and evapotranspiration of spring maize was analyzed, and the effects of different treatments on grain yield, economic benefits and use efficiency of water and nitrogen were studied.
The grain yield, economic benefit and use efficiency of water and nitrogen of spring maize were significantly improved by straw returning and irrigating at post-silking. Compared with conventional tillage, the grain yield, the economic benefit and the water use efficiency of straw returning treatment increased by 15.1%-43.5%, 15.9%-49.1%, and 16.8%-36.9%, respectively. The N recovery use efficiency, N agricultural efficiency, and N partial productivity of spring maize were significantly improved by 15.8%-62.0%, 26.5%-126.0%, and 15.1%-43.6%, respectively. The relationship between dry matter accumulation and evapotranspiration at post-silking was a quadratic function. Compared with conventional tillage, the straw returning treatment showed a stronger water productivity at post-silking. Though the yield response factor, the straw returning treatment had stronger water buffering capacity under water stress. Under the condition of straw returning, the grain yield and water and nitrogen use efficiency of the treatment with irrigation rate at post-silking were the highest under I150 treatment. In addition, the straw returning and irrigating at post-silking significantly promoted root growth of spring maize, but excessive irrigating (I200 treatment) inhibited root growth.
To sum up, in the spring maize production system in the eastern valley plain of the Loess Plateau, straw returning with the irrigating rate of 150 mm at post-silking could be used as a management measure for the efficient and sustainable use of water and nitrogen of spring maize.
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