Abstract:

As a prosperous fertilizer in crop production, release-controlled urea (CU) promotes the yield of maize (Zea mays L.) and nitrogen use efficiency with less environmental pollution than normal fertilizers. However, the interaction effects of CU and soil water content on the growth and development of maize have been rarely reported. In this study, the maize cultivar Zhengdan 958 was used to compare the differences of root activity, root and shoot growth, and yield between treatments with normal urea and CU under two water soil moisture conditions. The experiments were carried out in pools (10 m in length, 60 cm in width, and 1.2 m in depth) under a mobile water-proof shelter in 2006–2007. The normal urea was applied with basal (100% applied before sowing, NU) and split (40% applied before sowing and 60% applied at pretasselling stage, NS) dressing methods, whereas, the CU was totally applied before sowing. No urea applied was taken as the control. The results showed that the shoot dry weight and leaf area index of CU treatments were higher after anthesis and lower before anthesis than those of NU and NS treatments. As a result, the grain yield of CU treatment was significantly higher than those of NU and NS treatments, and the biomass of CU treatment was significantly higher (P < 0.05) than those of NU treatment and control. Under the condition of soil moisture at 50% of field capacity (W1), the grain yield of CU treatment was higher than those of NU and NS treatments by 27.3% and 12.1%, respectively. Under the condition of soil moisture at 75% of field capacity (W2), the grain yield of CU treatment was higher than those of NU and NS treatments by 17.4% and 8.1%, respectively. In the same urea treatment, the average values of grain yield and biomass were higher by 20.6% and 17.0% under W2 than those under W1, respectively. Root weight, root activity, and root/shoot ratio were lower before anthesis in CU treatment than in NU and NS treatments, but higher after anthesis in CU treatment than in NU treatment. The results suggest that the CU could have a remarkable early-decrease-and-late-increase effect on maize growth, and its coupling effect with soil moisture was higher than that of normal urea. The positive coupling effect of CU might be caused by the higher root activity and root/shoot ratio after anthesis, which could increase the accumulation and transportation of dry matters in the aboveground organs.

Key words: Field water capacity, Normal urea, Controlled release urea, Maize, Root/shoot ratio, Yield