Soil hydrophobicity and crop evapotranspiration of two indigenous vegetables under different wastewater irrigations in southwest Nigeria

The increased demand for irrigation to boost food supply has placed emphasis on the use of wastewaters. However, the indiscriminate use of wastewaters could impair soil functions and influence other hydrologic processes. The objective of this study was to evaluate soil hydrophobicity and evapotranspiration of two indigenous vegetables under wastewater irrigation in southwest Nigeria. The study was a factorial experiment, laid out in randomized complete block design (RBCD) with three replications. The vegetable factor consisted of SM - Eggplant (Solanum macrocarpon) and CA – Lagos spinach (Celosia angentea), while the wastewaters were abattoir wastewater (AW), bathroom and laundry wastewater (BW) and cassava effluent (CE), with rainwater (RW) as control. Soil hydrophobicity was determined before the experiment and after harvest using water-droplet penetration time (WDPT) method while the crop evapotranspiration was determined using soil water balance technique. Wastewater irrigation significantly (p<0.05) influenced soil hydrophobicity, as the initially wettable soil became slightly hydrophobic, with the highest degree from CE wastewater. The evapotranspiration of both vegetables was significantly (p<0.05) affected, with none of the wastewater treatments dominating the temporal distribution of crop evapotranspiration. Continuous application of wastewater for irrigation could increase the level of water repellency, affect soil water dynamics and availability.   Key words: Soil water repellency, wastewater effluent, evapotranspiration.