Organic amendments combined with moderate nitrogen rate significantly enhance soil fertility and crop productivity

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Nitrogen fertilizers and organic amendment inputs are essential for sustaining crop productivity and optimizing agricultural resources use. However, there is still limited information regarding the impacts of organic amendments on soil health and crop productivity under different long-term nitrogen application levels. This study aimed to assess the impacts of various organic amendments on yield, resource use efficiency, and soil nutrients under different long-term nitrogen application rates. A split-plot design experiment was conducted during 2021–2024, featuring three nitrogen levels (120, 240 and 360 kg ha −1 ) in the main plots and four organic amendments (straw (S), chicken manure (M), mushroom residue (MR), and biochar (B)) in the subplots. The results showed that increased nitrogen rates significantly reduced the mean weight diameter (MWD) of soil aggregates ( P<0.05 ). MWD values in treatments with M, MR, and B application increased by 18.26 %, 27.01 % and 37.78 %, respectively, compared to that in S treatment. Among all treatments, the soil fertility index (SFI) in N240-MR treatment was the highest. The average values over three years of experimental data showed that MR application significantly increased SFI by 18.08 % compared to S treatment (N240). Yield and water use efficiency (WUE) were highest at N240 treatment, whereas the partial factor productivity of nitrogen (PFPN) showed a decreasing trend as nitrogen input levels increased. Meanwhile, the application of M, MR and B increased wheat yield by 3.90 %, 4.56 % and 7.23 %, WUE by 1.88 %, 1.99 % and 4.17 % and PFPN by 4.69 %, 3.36 % and 10.16 %, respectively, compared to S application treatment. The comprehensive assessment results indicated that 240 kg N ha −1 with MR or B application was the best mode of fertilizer application + organic amendment addition. These findings provide a scientific basis for optimizing fertilization strategies in semi-arid regions, contributing to both enhanced resource use efficiency and sustainable wheat production.