Effects of Biochar on Irrigation Management and Water Use Efficiency for Three Different Crops in a Desert Sandy Soil

This paper aimed at investigating if the application of biochar (BC) to desert sand (DS) from the United Arab Emirates (UAE), characterized by a very poor soil-water retention (SWR) and by a very low value of the maximum water available for crops (AW(max)), could positively affect soil water balance, by reducing the irrigation needs (V-IRR) and improving the irrigation water use efficiency (IWUE) and the water use efficiency (WUE). The analysis was performed for three crops, i.e., wheat (Triticum aestivum), sorghum (Sorghum vulgare) and tomato (Lycopersicon esculentum).BCwas applied to theDSat different fractions,f(BC)(f(BC)= 0, 0.091, 0.23 and 0.33). Drip irrigation was adopted as a highly efficient water saving method, which is particularly relevant in arid, water-scarce countries. Soil water balance and irrigation scheduling were simulated by application of the AQUACROP model, using as input theSWRmeasured without and withBCaddition. The effect ofBCwas investigated under either a no-water stress (NWS) condition for the crops or deficit irrigation (DI). The results showed that the application ofBCmade it possible to reduce the predictedV(IRR)and to increase theIWUEunder theNWSscenario, especially for wheat and sorghum, with less evident benefits for tomato. When a deficit irrigation (DI) was considered, even at the lowest consideredf(BC)(0.091),BCcounterbalanced the lowerV(IRR)provided underDI, thus mitigating the yield reduction due to water stress, and improved theWUE. The influence ofBCwas more pronounced in wheat and tomato than in sorghum. The results evidenced that the application ofBCcould be a potential strategy for saving irrigation water and/or reducing the effects of drought stress in desert sand. This means that biochar could be used a management option to promote local production and reduce the dependency on food import, not only in the UAE, but also in other countries with extremely arid climatic conditions and large extensions of sandy soils similar to the consideredDS.