Study on energy and water balance of pepper field in arid areas

Abstract

The middle Heihe River Basin (MHRB) in arid areas in China faces the challenge of sustainability, but frequent over-irrigation deteriorated the situation. The water balance and energy budget have not been widely used for the quantifying evaluation of over-irrigation. Although some studies have measured the energy budget and water balance in cropland, the energy and water balance in pepper fields is still unclear. An experiment was conducted using an eddy covariance system, SmartView fluke and other measurements in MHRB. The leaf area index (LAI) for pepper increased in the first two months, then decreased thereafter. After Aug. 4, the daily evapotranspiration (ET) decreased during the maturation stage. The soil moisture was higher than the field capacity frequently, indicating that over-irrigation had occurred. Soil water content was relatively high at 100 cm depth, causing high percolation. The water inputs were 1.5 times ET, and the deep percolations accounted for 74% of the total irrigation inputs. Irrigation water could be conserved 301 mm, in case that percolation was avoided. Therefore, the irrigation amount (per time and total) should be reduced to achieve high water use efficiency (WUE). The latent heat flux (LE) consumed 80% of the net radiation (Rn). In July, the LE/Rn was the highest among all months, whereas H/Rn was the lowest due to the highest value of LAI in July. The net radiation had a significant positive linear correlation with the latent heat flux because of the high water supply. Our study showed that there was considerable room for water conservation in MHRB. Keywords: Sensible heat flux; Soil water content; Evapotranspiration; Latent heat flux; Leaf area index