Coupling the interactive effects of solar radiation, temperature and nitrogen on performance of transplanted rice

Abstract

AbstractField experiment to assess the impact of radiation, temperature and foliar N application on rice was conducted. The treatments comprised of four sunlight levels, [control, 50% intensity during start to maximum tillering (R15–45), maximum tillering to booting (R46–75) and panicle emergence to maturity (R76–105) corresponding to 15–45, 46–75 and 76–105 days after transplanting] and 5 levels of foliar nitrogen [control, spray of 3% urea solution in water before (NB), midway (NM), afterwards (NA) and midway + afterwards (NMA) reduction in sunlight]. Results showed that leaf chlorophyll had an inverse relationship with radiation intensity. The R46–75 significantly reduced effective tillers (13.1–16.4%), R46–75 and R76–105 reduced grains/panicle (7.15–12.5%) as compared to control. NB produced significantly higher effective tillers (21.9–24.7%) and grains/panicle (12.2–12.9%) as compared to control. The reduction in sunlight and application of foliar nitrogen increased the minimum cooking time and decreased elongation ratio. Averaged over locations, R15–45, R46–75 and R76–105 decreased the yield significantly as compared to control by 9.29–11.3, 14.4–16.3 and 8.17–10.6%, respectively. The NB significantly increased grain yield as compared to control by 10.3% (Ludhiana) and 9.45% (Hoshiarpur). A decrease in maximum temperature (Tmax) by 2.85–5.70% (1–2°C) of 35.1°C, at 1416 μmol/m2/s of photosynthetically active radiation (PAR) increased rice productivity by 10.6–21.0%, while a similar decrease in PAR by 2.85–5.70% at a Tmax of 35.1°C, decreased the productivity by 2.05–4.10%. So, decrease in Tmax due to cloudy weather might have a positive influence while negative impact of deficit radiation may be mitigated by foliar application of 3% urea prior to/during the cloudy weather.