Abstract
An experiment was conducted in the experimental farm of Bidhan Chandra KrishiViswavidyalaya, Nadia, West Bengal to study the radiation pattern and its balance over green gram (Vignaradiata var. Samrat). The BREB method was used to determine the sensible heat flux and latent energy. The net radiation was measured through net radiometer and the ground heat flux was measured using Fourier's law. Both the diurnal and seasonal variation of net radiation were studied. Similarly, the energy balance components were studied regularly for different crop growth stages as well as on diurnal basis. It is observed that the net radiation varies from 6.32 Wm-2 to 606.43 Wm-2. The latent heat flux constitutes more than 50% of the net radiation for all growth stages as depicted by energy balance partitioning. The sensible heat flux is partitioned into 10% to 20% of total net radiation throughout the growth stages of green gram, which is the lowest in magnitude among all three energy fluxes. The relationship between Bowen ratio and Vapour pressure deficit (VPD), Bowen ratio and Canopy air temperature difference (CATD) was studied. It was found that Bowen ratio is negatively correlated with VPD but positively correlated with CATD. This study enables to monitor ET pattern through latent heat flux and microclimatic characteristics through sensible and ground heat flux.
Highlights
IntroductionTotal energy available over a crop surface and its partitioning into different components, viz., sensible heat (H), latent heat (LE) and soil heat fluxes (G) determine the crop production
During morning hour (8:00 hours) the Rn ranges from 75.85 Wm2 to 227.56 Wm-2, whereas during afternoon hours (16:00 hours) the value varied from 12.64 Wm-2 to 151.71 Wm-2 for various growth stages of the crop
It was found that maximum negative magnitude of Canopy air temperature difference (CATD) coincided with the low value of Bowen ratio (Fig. 6), which might be due to cooling of leaf surface by transpiration that affects latent heat (LE) and Bowen ratio
Summary
Total energy available over a crop surface and its partitioning into different components, viz., sensible heat (H), latent heat (LE) and soil heat fluxes (G) determine the crop production. Bowen ratio energy balance (BREB) is a micrometeorological method that combines the Bowen ratio with energy balance equation of earth surface (Tanner, 1960) and assumes that under neutral stability conditions, the coefficients of heat transfer and water vapour are equal This method has been used to estimate energy (both sensible and latent heat parts) and mass (ET) fluxes to quantify water use of crop (Cargnel et al, 1996), determine crop coefficients (Malek and Bingham, 1993), evaluate crop water use models (Todd et al, 2000). Considering the importance of radiation and its balance, the present research work has been carried out to partition the radiation balance components over crop surface taking green gram as test crop
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