Lettuce Yield-Irrigation Water Quality and Quantity Relationships in a Gypsiferous Desert Soil
1987
Russo, David
Evaluation of the possibility of utilizing marginal soils and saline waters for agricultural production is essential for the development of arid zones. The effect of irrigation water quality (salinity) and quantity on the yield of lettuce (Lactuca saliva var. ‘Iceberg’) was studied in a gypsiferous desert soil (Typic Torrifluvent). Irrigation water volume (Q) ranging from 0.37 to 1.3, 0.6 to 1.6, and 0.7 to 2.4 times the Class A pan evaporation (Eₒ) for the irrigation water salinities of Cᵢw = 1.7, 3.1, and 4.7 dS/m, respectively, were applied via trickle irrigation. Root zone soil water pressure potential and salinity were monitored and lettuce yield was measured. Seasonal average soil water content (θ) was affected by irrigation water volume but not by quality (salinity) whereas seasonal average soil water salinity (EC) and lettuce yield (Y) were affected by both quality and quantity of the irrigation water. For the different ranges of Q associated with the different irrigation waters, θ was increased by 30, 44, and 94%, EC was decreased by 20, 21, and 18%, and Y was increased by 120, 71, and 55% for Cᵢw = 1.7, 3.1, and 4.7 dS/m, respectively. Curvelinear salt tolerance functions were found to be dependent on the volume of irrigation water, approaching a piecewise linear function when relatively large volumes of irrigation water (Q/Eₒ > 1) were applied. The increase in irrigation volume compensated only in part for the adverse effect of the irrigation water salinity. Maximum yields obtained using the more saline waters are 6.5 and 20.7% smaller for Cᵢw = 3.1 and 4.7 dS/m, respectively, relative to yield obtained using Cᵢw =1.7 dS/m.
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