[Effects of Organic Compost on Organic Carbon Storage and Maize Yield in Irrigated Silt Soil]

The effects of organic compost on soil nutrient characteristics， organic carbon sequestration mechanisms， and crop yield enhancement in irrigation-silted soils of the Yellow River irrigation district in Ningxia remain insufficiently understood. To enhance soil carbon pools， increase nutrient retention capacity， and improve monoculture maize productivity in organic agriculture， a fixed site experiment of four years was conducted with compost application gradients of 0 （M0）， 4 500 （M1）， 9 000 （M2）， 13 500 （M3）， 18 000 （M4）， and 22 500 （M5） t·（hm²·a）^-1. The study investigated the impacts on soil physicochemical properties， organic carbon storage， and maize yield. The results showed that organic compost application significantly increased the content of water-stable aggregates （0.25-2 mm and >2 mm）， enhancing aggregate stability as measured by mean weight diameter （MWD）. The M5 treatment increased MWD by 40.02% compared to that in M0 after four years， with dose-dependent improvements. M5 significantly increased available phosphorus （8.41%） and potassium （9.65%） compared to that in M0. Control plots （M0） exhibited progressive nutrient depletion， with organic carbon storage decreasing by 2.4 t·hm^-2 from 2020 to 2024， while M5 increased storage by 1.35 t·hm^-2. By 2024， the yield under the M5 treatment increased by 140.17% compared to that under the M0 treatment. The entropy weight method， redundancy analysis （RDA）， variation partitioning analysis， and structural equation modeling （SEM） revealed that compost application enhanced >2 mm macroaggregate formation， thereby increasing organic carbon storage and subsequently maize yield. Moreover， the study found a highly significant positive linear relationship between changes in cumulative organic carbon input， organic carbon storage， and yield， indicating that the carbon sequestration efficiency of irrigation silty soil over four years was 12.14%. An increase of organic carbon storage by 1 t·hm^-2 led to a maize yield increase of 637.92 kg·hm^-2. Based on this， the study suggests that to enhance soil organic matter by 5%-20% within four years， 7.55-36.04 t·hm^-2 of exogenous dry matter compost input would be required annually， and to increase yield by 5%-20%， 6.18-30.59 t·hm^-2 of exogenous dry matter compost would be needed annually. This study provides scientific evidence for sustainable utilization of livestock waste， soil carbon sequestration， and green agricultural development in arid irrigation regions.