Agricultural Water Management (Oct 2023)
Partitioning of available energy in canopy and soil surface in croplands with different irrigation methods
Abstract
Available energy partitioning in the canopy and at the soil surface under the control of biophysical environment critically influences agricultural water resources management and the regional climate. Drip irrigation technology has been extensively promoted in arid regions and is gradually replacing conventional border irrigation technology, which alters the soil surface hydrothermal conditions and influences the available energy partitioning both in canopy and at the soil surface through biophysical processes. The water-saving effect of drip irrigation has been well studied previously, however, its biophysical controls of available energy partitioning in canopy and soil surface remain insufficiently understood. In this study, we made continuous comparative measurements in two maize fields with border irrigation and drip irrigation during the growing seasons in the period 2014–2018 by simultaneously using eddy covariance systems, sap flow gauges and micro-lysimeters. We found that drip irrigation increased transpiration by 10% and reduced soil evaporation by 40% during the partial canopy period, and these values decreased to 1% and 26%, respectively as the crop developed to complete canopy cover period. However, drip irrigation increased sensible heat fluxes both in canopy and soil surface by 93% and 46%, respectively during the partial canopy period, and by 10% and 231%, respectively during the complete canopy period. The soil moisture drives the discrepancy of available energy partitioning in both canopy and soil surface between two fields. Slow-release effect of the drip irrigation in replacing warm air in soil pores enhanced thermal convection in soil surface, small irrigation volume and small moisture area decreased evaporation loss, and frequent irrigation and sufficient soil moisture induced stable energy interaction between canopy and soil surface, therefore enhancing more sensible heat directed to canopy and soil surface in drip irrigated field. The results enhanced understanding of ecohydrology processes in agroecosystems and provided valuable information for agricultural water resource management.
