Abstract: The persistent scarcity of water resources and suboptimal nutrient utilization rates are predominant challenges in agricultural production, both in China and globally. The modified cellulose and biochar have good functions of retaining water and fertilizer in soil. Authors employed these substances as soil amendments, investigating their individual and combined effects on the soil's physicochemical properties, nutrient content, moisture, and the germination of upland rice. The experiment was conducted in an artificial climate greenhouse, using upland rice as the test crop. A pot experiment was established with a control group CK (no modified cellulose or biochar), three types of modified cellulose (CMC-NH₄, CMC-Na and CMC-K) each at a 0.05% mass fraction (labelled A1, B1 and C1), a 0.10% mass fraction (labelled A2, B2 and C2), and 0.50% biochar (D1), combinations of three modified celluloses at 0.05% and 0.10% mass fractions were used with 0.50% biochar (labeled A1D1, B1D1, C1D1, A2D1, B2D1 and C2D1) across 14 treatments. These treatments on soil's physicochemical properties (pH, compactness, surface crust thickness), nutrients (ammonium nitrogen, nitrate nitrogen, available phosphorus, available potassium), water loss, and upland rice germination (plant height, above-ground biomass) were analyzed. The results showed that: relative to CK, the A1 and A2 treatments reduced soil pH by 0.20 and 0.17 unit, respectively, whereas the B1, B2, C2 and D1 treatments increased it by 0.32, 0.43, 0.20 and 0.42 unit, respectively. CMC-NH₄ and CMC-K combined with biochar showed a tendency to increase soil pH, in contrast to CMC-Na combined with biochar, which had no significant impact. Compared with CK, the A1, A2, B1 and B2 treatments notably enhanced soil compactness by 13.69%, 22.90%, 99.66% and 113.58%, respectively. Each modified cellulose type, when applied singly, variably increased soil clumping and surface crust formation. The A1D1, A2D1, B1D1 and B2D1 treatments moderately reduced soil compactness (8.88%, 11.78%, 14.95% and 14.24%), and when combined with biochar, also diminished the surface crust thickness of the soil (52.55%, 60.59%, 29.94%, 38.65%, 43.54% and 45.20%). Notably, the A2 and A2D1 treatments increased soil ammonium nitrogen by 275.84% and 48.99%, respectively, while the C1, C2, C1D1 and C2D1 treatments significantly reduced it (51.01%, 53.02%, 41.61% and 45.64%). The application of modified cellulose and biochar, either singly or in combination, enhanced the soil content of nitrate nitrogen, available phosphorus, and available potassium (ranging from 9.01% to 95.72%). The combined application proved more beneficial for increasing soil nutrients. Only the A2D1, B1D1 and B2D1 treatments significantly lessened cumulative soil water loss (8.86%, 6.33% and 6.33%), with no notable differences in the other treatments. The A1, B1, C1 and BC treatments considerably augmented the biomass of upland rice, achieving increases of 203.88%, 133.49%, 111.16% and 18.93%, respectively. Among the high-dose modified cellulose treatments, only C2 significantly raised the aboveground biomass of upland rice by 71.84%. The combined treatments A1D1, A2D1, B1D1, B2D1, C1D1 and C2D1 notably enhanced the aboveground biomass of upland rice (225.24%, 147.57%, 143.20%, 138.83%, 125.73% and 119.90%). Overall, the synergistic application of 0.05% modified cellulose with 0.50% biochar markedly improves soil structure, boosts nutrient content, and enhances the aboveground biomass of upland rice. This combination is a promising approach for soil amelioration in arid regions.

Key words: Modified celluloser, Biochar, Soil?nutrient, Soil water retention, Biomass