Performance of polymer-coated urea in transplanted rice: effect of mixing ratio and water input on nitrogen use efficiency |
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Authors: | Mukund D Patil Bhabani S Das Eran Barak Pratap B S Bhadoria Amir Polak |
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Institution: | (1) Agricultural and Food Engineering Department, Indian Institute of Technology, Kharagpur, West Bengal, 721302, India;(2) Haifa Chemicals Ltd, P.O. Box 10809, Haifa Bay, 26120, Israel; |
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Abstract: | Polymer-coated urea (PCU) is an important alternative to uncoated urea for improving nitrogen (N) use efficiency (NUE). Only
a few studies discuss their utility for lowland rice systems. A 2-year field study was conducted to examine if nitrogen loading
is reduced in lowland rice ecosystem by using mixture of PCU and uncoated urea without sacrificing yield. Five treatments
involving two mixtures of PCU with 50 and 70% coated urea each at 70 and 50% of recommended dose (80 kg N ha−1) and one with uncoated urea at 100% recommended dose were laid out in a completely randomized design. Selected plant growth
parameters and plant available N contents (NH4–N plus NO3–N) in soil solution and ponded water were measured over a period of 65 days after transplanting. Results showed no significant
difference for vegetative and yield parameters among different treatments suggesting that treatments receiving lower doses
of nitrogen exhibited higher NUE. Analysis of partial factor of productivity (PFP) for N suggested that the total N dose may
be reduced by 50% using mixtures of coated and uncoated urea. Similarly, statistically similar PFP values for treatments receiving
the same amount of total N for both years and for both total N dose suggested that the proportion of coated urea may also
be reduced to as low as 50% without sacrificing yield. Correlation analysis on nitrogen contents in ponded water and soil
solutions and the analysis of water productivity and PFP showed that soil water regime could also significantly influence
the nitrogen status in soil even when PCU are applied. In turn, both the water regime and N contents in soil ultimately influences
grain yield. Although the constant release of N from coated fertilizer ensures adequate N supply for plant uptake, it may
not completely avoid N deficit condition especially during heavy rainfall. Analysis of the developed production function suggested
that 55–65% polymer coating and about 100 cm total water input may be ideal for achieving maximum yield. The production function
was developed for PCU treatments using data observed in treatments receiving 70% recommended N dose. The range of water input
in these treatments was 86.5–174.0 cm. |
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