Controlled release urea improved the nitrogen use efficiency, yield and quality of potato (Solanum tuberosum L.) on silt loamy soil

Numerous studies on the traits of controlled release urea in agronomic production and the environmental protection were conducted in various crops system. However, understanding the effect of controlled release urea on potato production and nitrogen use efficiency was currently limited. In the present study, the effect of newly developed controlled release urea (CRU) including polymer coated urea (PCU) and polymer coating of sulfur-coated urea (PSCU) on the N use efficiency, tuber yield and quality of potato (Solanum tuberosum L.) that was grown on silt loamy soil were investigated in a field experiment over 2 yr at different sites. The application rate of polymer-coated urea (PCU) and urea was 150 kg N ha(-1), and polymer sulfur-coated urea (PSCU) was applied at 150 kg N ha(-1) and 225 kg N ha(-1). The N release rates from CRU synchronized the N requirement of potatoes at different stages. The CRU treatments significantly increased total tuber yields by 8.77-19.88% in 2012 and 14.36-26.46% in 2013 in comparison with the urea treatment during the same year. The marketable tuber yield percentage was pro-nouncedly promoted by the application of PCU and PSCU in both years. N fertilization significantly enhanced the vitamin C, soluble protein and starch content. The significant difference of vitamin C concentration in tuber was only observed in 2013 between PCU and PSCU treatments. The application of PCU and PSCU markedly improved the N agronomic efficiency and apparent N use efficiency, but obviously decreased the N physiological efficiency relative to urea treatment in 2012 and 2013. Furthermore, enhancing dose of PSCU did augment total tuber yield and did not increase the marketable yield percentage, but decreased the apparent N use efficiency compared with PSCU treatment. Consequently, moderate amounts (150 kg N ha(-1)) of PSCU and PCU are recommended to replace urea for gaining greater yields of potato and nutrient use efficiency. (C) 2015 Elsevier B.V. All rights reserved.