Objective  Based on the requirement of soil water and nutrient improvement of newly cultivated farmland of Loess Plateau in Yanan, Shaanxi Province, potassium carboxymethyl cellulose (CMC-K) was acted as a soil amendment.

  Method  The field experiment was conducted with 5 treatments ( CK, 0 kg hm⁻²; T1, 100 kg hm⁻²; T2, 500 kg hm⁻²; T3, 1000 kg hm⁻²; T4, 2000 kg hm⁻²) to research the changes in soil water, soil electric conductivity and soil nutrients.

  Result  CMC-K application improved soil water content 14.6%-121.7% in newly cultivated farmland, the efficacy of CMC-K application was better in early (June and July) and end-stage (October) of millet growing season than those in the middle stage (August and September). The large CMC-K application amounts (1000-2000 kg hm⁻²) could improve significantly soil electric conductivity by 37.3%-73.4% in early (June) of millet growing season, and soil electric conductivities of all treatments were decreased significantly by 19.2%-21.8% in end (October) of millet growing season. Soil electric conductivities presented decreasing trend in the millet growing season. CMC-K application had no effects on soil total nitrogen, total phosphorus, total potassium, and pH, but enhanced soil nitrate (9.6%-46.5%), available phosphorus (21.9%-207.9%), and available potassium (13.2%-95.9%). CMC-K application could increase millet yield by 6.2%-19.2%.

  Conclusion  CMC-K application can hold soil water, promote soil nutrient absorption and raise millet yield in newly cultivated farmland in Loess Plateau, which may act as a soil amendment and the recommended application rate is 100 kg hm⁻².