Partitioning of Cotton Field Evapotranspiration under Mulched Drip Irrigation Based on a Dual Crop Coefficient Model

Abstract

Estimation of field crop evapotranspiration (ET c ) and its partitioning into evaporation and transpiration, are of great importance in hydrological modeling and agricultural water management. In this study, we used a dual crop coefficient model SIMDualKc to estimate the actual crop evapotranspiration (ET c act ) and the basal crop coefficients over a cotton field in Northwestern China. A two-year field experiment was implemented in the cotton field under mulched drip irrigation. The simulated ET c act is consistent with observed ET c act as derived based on the eddy covariance system in the field. Basal crop coefficients of cotton for the initial, mid-season, and end-season are 0.20, 0.90, and 0.50, respectively. The transpiration components of ET c act are 96% (77%) and 94% (74%) in 2012 and 2013 with (without) plastic mulch, respectively. The impact of plastic mulch cover on soil evaporation is significant during drip irrigation ranging from crop development stage to mid-season stage. The extent of the impact depends on the variation of soil moisture, available energy of the soil surface, and the growth of the cotton leaves. Our results show that the SIMDualKc is capable of providing accurate estimation of ET c act for cotton field under mulched drip irrigation, and could be used as a valuable tool to establish irrigation schedule for cotton fields in arid regions as Northwestern China.

Comparison of the Vegetation Effect on ET Partitioning Based on Eddy Covariance Method at Five Different Sites of Northern China

“…At the Xinier site, mulch drip irrigation is applied, which delivers water precisely to the root zone of crops and consequently soil water is low in the inter-film zone, resulting in a high fraction of transpiration and low soil evaporation. This result is similar to the finding of Tian et al [57]. At the Daman site, flood irrigation is conducted and, as a result, there is no obvious difference in soil water under root zone and inter-film zone.…”

Irrigation-Induced Changes in Evapotranspiration Demand of Awati Irrigation District, Northwest China: Weakening the Effects of Water Saving?

“…As an effective and economic method to increase water use efficiency, drip irrigation under plastic mulch has been extensively adopted by local cotton farmers [15,41]. The water requirement of cotton with drip irrigation under plastic mulch is considerably less than that of traditional cotton [41,42].…”

Estimating Evapotranspiration and Its Components in Cotton Fields under Deficit Irrigation Conditions

“…Data on actual evapotranspiration (ET c act ) may be derived from a range of measurement systems [10][11], including lysimeters [12][13], eddy covariance [6][7]11], the Bowen ratio [14][15][16], water budget analysis [7,11], sap flow analysis [17], satellite-based remote sensing [18], and model simulations [19]. Of these systems, the FAO-56 dual crop coefficient approach is considered the most accurate for estimating daily ET c , as it separately calculates soil evaporation and crop transpiration [20][21][22].…”

“…The dual crop coefficient approach allows for accurate estimation of the water-saving potential of a water management strategy from the ratios of evaporation to reference evapotranspiration (E/ET o ), and transpiration to reference evapotranspiration (T/ET o ). Additionally, the dual crop coefficient approach allows for more accurate planning of irrigation scheduling, especially under partial crop cover or drip irrigation conditions [20][21][22]. Another advantage of the dual crop coefficient approach is that it more precisely simulates the effects of mulching on soil evaporation.…”