Abstract: BackgroundThe hilly regions of the Loess Plateau are critical for grain production in China, but newly reclaimed croplands from the "Gully Regulation and Land Reclamation" project face prominent challenges such as loose soil texture, poor water and fertilizer retention capacity, and high risks of nutrient leaching and soil erosion, which severely limit crop productivity. Existing soil amendments (polyacrylamide, humic acid, biochar) have drawbacks like environmental toxicity, unstable field effects, or high costs. Potassium carboxymethyl cellulose (CMC-K), a modified cellulose derivative, exhibits unique advantages including water absorption, nutrient retention, and potassium supply without causing soil salinization, making it a potential alternative for soil improvement. However, its effects on newly reclaimed croplands in the Loess Plateau remain insufficiently explored. MethodsA field experiment was conducted in newly reclaimed croplands in Nangou Village, Ansai District, Yan'an City (Shaanxi Province), a typical hilly-gully area of the Loess Plateau. Six CMC-K application rates were set: 0 (CK), 100 (T1), 500 (T2), 1000 (T3), 2000 (T4), and 3000 (T5) kg/hm², with three replicates per treatment (18 plots total, each 30 m²). Basic fertilizers (urea, diammonium phosphate) and organic fertilizer were applied during land preparation, with two topdressings of urea during the growing season. Maize (cultivar: Dafeng 26) was sown in May 2024 and harvested in October 2024. Soil water content, temperature, and electrical conductivity were measured at the jointing, tasseling, flowering, and harvest stages using a TDR350. Soil nutrients (total potassium, available potassium, nitrate nitrogen, etc.) and pH were determined via the five-point sampling method at harvest. Maize plant height, SPAD value (chlorophyll content), and grain yield were also measured. Data were analyzed using one-way ANOVA (SPSS 21.0), and correlation analysis was performed for key indicators.ResultsCMC-K application showed significant effects on soil properties and maize growth with distinct growth stage-specificity. At the jointing and tasseling stages, T4 and T5 significantly increased soil water content by 7.74%-9.02% and 23.79%-25.90%, respectively, while no significant differences were observed at the flowering and harvest stages. All treatments increased soil temperature by 0.21-0.51 ℃ at the jointing stage but decreased it by 2.61-4.11 ℃ at the tasseling stage. Except for the harvest stage, soil electrical conductivity tended to increase in all treatments, with T4 and T5 showing the most remarkable increments (33.33%-80.77%). Compared with CK, all treatments except T1 significantly enhanced soil total potassium (36.61%-65.19%), available potassium (42.66%-333.57%), and nitrate nitrogen (12.68%-25.60%), with the highest available potassium content reaching 620 mg/kg in T5. Additionally, CMC-K improved maize SPAD value (8.50%-12.11%) and grain yield (6.62%-38.15%), with T5 achieving the highest yield (6895.1 kg/hm²). Correlation analysis revealed significant positive correlations between CMC-K application rate and soil water content, nutrient levels, maize plant height, and yield.ConclusionCMC-K effectively improves soil water-holding capacity, optimizes nutrient availability, and regulates soil hydrothermal conditions in newly reclaimed croplands, thereby promoting maize growth and increasing yield. Its application avoids environmental risks associated with traditional amendments and integrates both soil amendment and nutrient supply functions. Considering soil improvement effects, yield benefits, and economic costs, the recommended CMC-K application rate is 2000 kg/hm² for newly reclaimed croplands in Yan'an. Future studies should focus on long-term positioning experiments and explore the underlying mechanisms involving soil physical structure (aggregate stability, bulk density) and microbial communities to provide more comprehensive theoretical support for its widespread application in the Loess Plateau.