Slow-release fertilizer (SRF) improves Kimchi cabbage (KC) productivity in the Highlands of Gangwon Province in South Korea; however, optimum rates for the region are not established. This study investigated the optimum and most economical rate of SRF that maximizes KC yield, nutrient uptake and nitrogen use efficiency (NUE) and enhances soil quality in two experiments at the Highland Agriculture Research Institute. Post-harvest soil N (mg kg⁻¹), P₂O₅ (mg kg⁻¹), K, Ca and Mg (cmol_c kg⁻¹), pH (1:5), electrical conductivity (EC; dSm⁻¹) and organic matter (OM; g kg⁻¹) were measured to assess soil quality. Added net returns (ANR) of treatments were evaluated. Recommended N rate (238 kg ha⁻¹) for KC production was the basis for treatment applications. Treatments included no fertilizer control (‘nf’), full N recommendation SRF (SF1), ½ N recommendation SRF (SF0.5), double N recommendation SRF (SF2) and full N recommendation conventional fast fertilizer (FF). Results showed that SF0.5, SF1 and SF2 influenced the highest KC marketable yield in both experiments (66–74 and 42–66 Mg ha⁻¹, respectively). SRF rates between 0.5 and 1 times the N recommendation produced the highest possible linear increases in marketable yield; and the most economical, with ANR > KRW 83 million ha⁻¹ in the first experiment and > KRW 22 million ha⁻¹ in the second. Crop N, P, K, Ca and Mg uptakes were highest among the three SRF rates in both experiments. SF0.5 influenced the highest (91%) NUE in the first experiment; however, it left 8 mg kg⁻¹ N by the end of this experiment compared to the start-up 27.2 mg kg⁻¹ N. Thus, nutrient mining occurred. Soil N increased between 23 and 135 mg kg⁻¹ by SF 1 and 2 in both experiments. Soil EC spiked to 0.6 dSm⁻¹ from the initial level of 0.2 dSm⁻¹ by SF2 in the first experiment. Soil pH, P₂O₅, K, Ca and Mg levels post-harvest were comparable among treatments in both experiments. SF0.5, 1 and 2 increased soil OM by 7–16% above pre-experimental levels in the second experiment. In conclusion, SRF rates between 0.5 and 1 for KC produced the maximum corresponding KC yield and were the most economical. SRF rates ≤ 0.5 pose risks of nutrient mining, which could jeopardise native soil fertility. SF1 and 2 improved some soil quality indices (N and OM). However, SF2 potentiates risks of soil salinity and large P losses, and it is less economical. Therefore, for holistic sustainability of the cropping system, the optimum SRF rate should lie between 0.5 and 1 N recommendation.

Large annual soil losses in the highlands of Gangwon necessitates growing appropriate crops and applying effective soil conservation measures to sustain agricultural productivity in the region. This study evaluates the effect of strip-tilled soybean / cover crop rotation on soil loss in the 2021, 2022 and 2023 growing seasons in 2, 7 and 15% slope lysimeters at the Highland Agriculture Research Institute in Gangwon. Cover crops were a 5:1 mixture of rye and hairy vetch planted during the fallow period, after soybean harvest. Cover crop biomass and soybean residue were left on the soil surface throughout the study. Soil losses under soybean and cover crop cultivation, and bare land were quantified. Cover management factor (C-factor) estimations of soybean and cover crops were made. Results showed that strip-tilled soybean reduced total soil loss by 19 to 109 times that of bare land in all the three slope lysimeters during the soybean growing periods. C-factors for the cultivation periods of strip-tilled soybean in all growing seasons were lower (0.0006 to 0.12) than the 12-year average C-factor (0.19) of conventionally tilled soybean. The reduction in c-factors could be attributed to the ability of soybean crops, strip tillage and soil surface cover to enhance soil conservation as slope gradients increase in the Highlands. Compared to bare land, cover crops also reduced total soil loss by 2 to 61 times in all the three slope lysimeters, during the cover crop growing periods. Applying strip tillage, rotating soybean with cover crops in the fallow period and maintaining soil surface cover in soybean cropping systems is an effective way of reducing soil loss and promoting agricultural productivity in the highlands of Gangwon.