Simulation of nitrogen balance in rice as influenced by irrigation, nitrogen and climate change scenario
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Date
2017
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Punjab Agricultural University, Ludhiana
Abstract
Yield potential of rice depends on climatic factors including rainfall, solar radiation
and temperature as well as irrigation regime, cultivar and fertilizer nitrogen level. The
excessive fertilizer N is being applied by farmers in the quest for higher yields ignoring
economic water and N productivities, and environmental pollution. Whole fertilizer N not
utilized by rice plants, some portions of N fertilizer are easily lost through various processes,
such as NH3 volatilization, leaching and uptake. With prime importance to quantify the
nitrogen balance components in rice, field studies were conducted at two different locations at
research farms of Department of Soil Science, Punjab Agricultural University, Ludhiana,
Punjab, on sandy loam soils during kharif 2016. In the field study, effect of irrigation regimes
(irrigation based on two days drainage period, and based on soil water suction (16 kPa)) and
nitrogen levels (0, 60, 120 and 180 kg N ha-1) on growth, yield of rice and nitrogen uptake
were evaluated. To assess the N balance components, DNDC (Denitrification-Decomposition)
model was evaluated and simulations for yield and N balance components were made for past
30 years (1986-2016) and future 30 years (2021-2050) on different soil series of Ludhiana
district of Punjab. Averaged over irrigation regimes, rice yield increased significantly with
increasing nitrogen levels. Highest rice grain yield was recorded with application of 180 kg N
ha-1 (52.9-59.6 q ha-1), which was significantly higher than control, 60 and 120 kg N ha-1 at
location 1 but at par with application of 120 kg N ha-1 at location 2. N uptake was also found
higher (46.3-56.4 kg ha-1) in the treatments with 180 kg N ha-1. However, treatments with 60
kg N ha-1 gave higher nitrogen use efficiency in terms of agronomic (20-25 kg kg-1) and
recovery (54.8-59%) efficiency. Simulated rice yield, N uptake and volatilization would
decrease with lower nitrogen levels, coarseness in soil texture and future time slices but
leaching losses would increase with higher nitrogen levels, coarseness in soil texture and
future time slices. However, percent reduction in yield would be more in end part of mid
century (2041-2050). Percent yield reduction would be low at higher nitrogen levels (150-180
kg N ha-1) and in fine textured soils (silt loam). The study suggests that higher N levels could
be good option to compensate yield reduction in future however higher nitrogen levels would
lead to higher N leaching and volatilization.