Controlled drainage in the Nile River delta of Egypt:a promising approach for decreasing drainage off-site effects and enhancing yield and water use efficiency of wheat

North Africa is one of the most regions impacted by water shortage.The implementation of controlled drainage(CD)in the northern Nile River delta of Egypt is one strategy to decrease irrigation,thus alleviating the negative impact of water shortage.This study investigated the impacts of CD at different levels on drainage outflow,water table level,nitrate loss,grain yield,and water use efficiency(WUE)of various wheat cultivars.Two levels of CD,i.e.,0.4 m below the soil surface(CD-0.4)and 0.8 m below the soil surface(CD-0.8),were compared with subsurface free drainage(SFD)at 1.2 m below the soil surface(SFD-1.2).Under each drainage treatment,four wheat cultivars were grown for two growing seasons(November 2018–April 2019 and November 2019–April 2020).Compared with SFD-1.2,CD-0.4 and CD-0.8 decreased irrigation water by 42.0%and 19.9%,drainage outflow by 40.3%and 27.3%,and nitrate loss by 35.3%and 20.8%,respectively.Under CD treatments,plants absorbed a significant portion of their evapotranspiration from shallow groundwater(22.0%and 8.0%for CD-0.4 and CD-0.8,respectively).All wheat cultivars positively responded to CD treatments,and the highest grain yield and straw yield were obtained under CD-0.4 treatment.Using the initial soil salinity as a reference,the soil salinity under CD-0.4 treatment increased two-fold by the end of the second growing season without negative impacts on wheat yield.Modifying the drainage system by raising the outlet elevation and considering shallow groundwater contribution to crop evapotranspiration promoted water-saving and WUE.Different responses could be obtained based on the different plant tolerance to salinity and water stress,crop characteristics,and growth stage.Site-specific soil salinity management practices will be required to avoid soil salinization due to the adoption of long-term shallow groundwater in Egypt and other similar agroecosystems.

Predicted and measured soil retention curve parameters in Lombardy region north of Italy

Water retention characteristics are fundamental input parameters in any modeling study on water flow and solute transport.These properties are difficult to measure and for that reason,we usually need to use direct and indirect methods to determine them.An extensive comparison between measured and estimated results is needed to determine their applicability for a range of different soils.However this study attempts to make a contribution specifically in this connection.These properties were determined in two representative sites located in Landriano field,in Lombardy region,northern Italy.In the laboratory we used the pressure plate apparatus and the tensiometric box.Field soil water retention was determined including measurements of soil water content with SENTEK probes and matric potential with tensiometers.The soil waer retention curves(SWRC)were also settled on with some recently developed pedo-transfert functions(PTFs).Field retention curves were compared against those obtained from PTFs estimations and laboratory measurements.The comparison showed that laboratory measurements were the most accurate.They had the highest ranking for the validation indices(RMSE ranging between 2.4%and 7.7%and bias between 0.1%and 6.4%).The second best technique was the PTF Rosetta(Schaap et al.2001).They perform only slightly poorer than the laboratory measurements(RMSE ranging between 2.7%and 10%and bias between 0.3%and 7.7%).The lowest prediction accuracy is observed for the Rawls and Brakensiek(1985)PTF(RMSE ranging between 6.3%and 17%and bias between 5%and 10%)which is in contradiction with previous finding(Calzolari et al.,2001),showing that this function is well representing the retention characteristics of the area.Due to time and cost investments of laboratory and field measurements,we conclude that the Rosetta PTF developed by Schaap et al.(2001)appears to be the best to predict the soil moisture retention curve from easily available soil properties in the Lombardy area and further field investigations would be useful to support this finding.