Effects of urea types and irrigation on crop uptake, soil residual, and loss of nitrogen in maize fieldon the North China Plain.

Water and nitrogen managements are both very important to increase crop yield. An experiment was carried out in split plot design to study the effects of urea types (normal urea and coated urea) and irrigation on soil and fertilizer nitrogen use in maize (Zea mays L.) field in 2006 and 2007. Irrigation was used as main plot, and urea types were used as split-plot. Two irrigation levels, no irrigation in the whole growth duration and 85 mm irrigation at the blister stage, were designed. There were five nitrogen treatments, which were no nitrogen used as control (NO), normal urea 75 kg N/ha (Ni), normal urea 150 kg N/ha (N2), coated urea 75 kg N/ha (Cl) and coated urea 150 kg N/ha (C2). The results showed that, at the same level of irrigation and nitrogen, the soil nitrogen contents of the treatments with coated urea (CU) applied were higher in 0 similar to 40 cm soil layers, but lower in deeper soil layers, than those with normal urea (NU) applied. Irrigation increased the nitrate losing, but the nitrate loss of CU was lower than those of NU. Using CU with irrigation could increase the nitrogen uptake by maize, and more nitrogen was transfered to grain. At the same nitrogen level, CU had higher N recovery efficiency but lower soil N dependent rate than NU. When applied with CU, the nitrogen release rate was lower and the nitrogen was quickly absorbed by maize, which reduced the risk of nitrogen loss and increased the use efficiency of soil and fertilizer nitrogen. These results suggest that coated urea combined with deficit irrigation should be applied for high yield and nitrogen use efficiency of maize on the North China Plain.