Abstract:Root zone fertilization is an important measure for efficient fertilization. To determine the optimal location of root zone fertilization, it is necessary to understand the law of nutrient transfer in the soil after fertilization. The effects of soil water content and incubation time on nitrogen, phosphorus, and potassium migration of point-applied compound fertilizer which composed of urea, ammonium polyphosphate and potassium chloride were studied with laboratory incubation experiment. The results showed that with the increase of soil water content from 300 g/kg to 420 g/kg, the migration distances of nutrients increased significantly. After incubated for 15 d in soils of Jiangyan and Guangde, the migration distance of ammonium nitrogen, available phosphorus, and available potassium increased from 9–11 cm, 4 cm and 9–10 cm to 12–14 cm, 5–6 cm and 11 cm, respectively. With the increase of soil water content, the distance of N and P migration increased by about one third on average. With the increase of incubation time from 15 d to 30 d, there was no significant change in the migration distance of available phosphorus, but the migration distance of available potassium increased significantly. The migration distance of ammonium nitrogen increased significantly in Guangde paddy soil with weak nitrification, while it increased slightly in Jiangyan paddy soil with strong nitrification. The nitrification of ammonium nitrogen under fertilizer hole-application was not only affected by soil water content, pH and time but also strongly inhibited by high concentration nutrients of ferti-sphere. High concentration nutrients delayed the transformation of ammonium to nitrate, which was an important mechanism account for the efficient nitrogen supply under root zone fertilization technology. In a whole, the nutrient migration distance is as follows: nitrate nitrogen > ammonium nitrogen > available potassium> available phosphorus. Nitrogen migration is easily affected by nitrification, while the available phosphorus migration is greatly affected by soil water content. The migration patterns of available potassium and ammonium nitrogen are similar, both of which increase gradually with the increased time and soil water content.