EFFECTS OF SOIL TEXTURE, NET EVAPOTRANSPIRATION AND OTHER FACTORS ON IRRIGATION REQUIREMENTS OF ORCHARDS AS DETERMINED BY A SCHEDULING PROCEDURE

Publisher Website
Google Scholar
Abstract
Minimum annual irrigation-water requirements were determined in 17 mature orchards over a 4-year period, by gradually reducing the application rates until the desired minimum soil-moisture contents were achieved. Variations in weather were taken care of by use of a scheduling procedure. The criteria used for determination of minimum requirements allowed for some wilting of the cover crops, but not of the trees. The soils ranged from a sand to a fine silt loam, with accompanying wide ranges in water-holding capacity, depth of water needed at each irrigation, and safe irrigation interval in the heat of the summer. Highly significant correlations were obtained between the annual irrigation requirement on the one hand and soil texture and net evapotranspiration on the other hand. By multiple regression it was found that these two factors, together with number of days of irrigating, accounted for 91 to 94% of the variation in annual irrigation applications. It is concluded that the coarser-textured the soil, the greater was the annual irrigation requirement.