Improving Sustainable Production of Maize on Upland Soils of the Democratic People's Republic of Korea

Maize production in the Democratic People's Republic of Korea is limited by soil infertility. Trials were established at two cooperative farms to quantify the yield response of maize to fertilizer and to vetch green manure. Crop land is precious so the vetch had to be integrated either by a short growth period prior to the crop in spring, or risking an autumn sowing for growth over winter. Maize grain yield was linearly related to the amount of vetch incorporated before maize at an annualized rate of 77–121 kg grain per fresh weight ton of vetch manure. The N fertilizer substitution value was about 60 kg N ha−1 as urea. This response may be increased by adopting more cold-tolerant vetch (or alternative legumes), and safeguarding vetch from villager's livestock.