Effects of mixing controlled-release and normal urea on yield, nitrogen absorption and utilization in waxy maize

Objectives Extension of slow or controlled-release fertilizer make its simplified application possible in maize production in China. We studied the suitable blending ratios of controlled-release urea with normal urea in waxy maize production.

Methods Field experiments were conducted in 2019 and 2020, using the waxy maize cultivar Lianhuanuo 2 as the test material. Under total N input of 225 kg/hm², five ratios of normal urea: controlled-release urea were set up as 1∶0 (N1), 0∶1 (N2), 1∶2 (N3), 1∶1 (N4), and 2∶1 (N5), taking no N application (N0) as the control. The maize grain yield, dry matter accumulation, translocation and distribution, and N use efficiency were investigated.

Results The mixture of controlled-release and normal urea affected waxy maize yield, N absorption and utilization (P<0.05) . The controlled-release urea treatments recorded a higher yield and income increase than the single application of normal urea. N3 had the highest yield (30%) and income (2835 yuan/hm²) increase. The yield and income of N4 and N5 were higher than that of N1, but lower than that of N3. The mixture of controlled-release and normal urea increased post-silking dry matter and N accumulation (P<0.05), but N3 recorded higher values followed by N2 and N4 (P<0.05). However, the income of N5 and N1 did not differ. The mixture of controlled-release and normal urea had an effect on the rate and quantity of plant N translocation (P<0.05). N2, N3, and N4 recorded similar rates and quantities of N translocation, which were higher than N1 and N5. The average harvest index and grain N content at maturity with the controlled-release treatment were higher than N1 (P<0.05). N3 had the highest harvest index (0.45) and grain N content (57.5%), followed by N2. Compared with N1, mixing controlled-release and normal urea improved N partial factor productivity (NPFP), N agronomic efficiency (NAE), and N recovery efficiency (NRE) of waxy maize, with N3 having the highest increase, followed by N2 and N4, while those of N5 and N1 did not differ. Compared with N2, N3 increased NPFP by 2.6 kg/kg, NAE by 2.6 kg/kg, and NRE by 6.6 percentage points.

Conclusions Based on the yield, nitrogen absorption and utilization in two years, mixing controlled-release and normal urea (1∶2) at 225 kg/hm² can improve grain yield and N use efficiency and profit synchronous in waxy maize production in Jiangsu Province.