Leaching requirement for salinity control III. Barley,cowpea, and celery

Leaching requirement, the smallest steady-state leaching fraction which prevents any loss in crop yield, was determined for barley, cowpea, and celery in field plots at the U.S. Salinity Laboratory. Six replicated leaching-fraction treatments were irrigated many times each day with small quantities of water having an electrical conductivity of 2.3 dS/m. The crops were grown in succession between January 1979 and September 1981.The leaching requirement (L_r) was 0.10 for barley grain and 0.13 for barley forage. For cowpea seed, L_r was 0.16; 0.17 for cowpea forage. L_r for celery was 0.14. These experimentally determined values for barley and cowpea seed are higher by about 0.05 than those predicted by a leaching-requirement model based on an exponential crop water-uptake pattern. The experimental values for celery and cowpea forage are lower than predicted values by 0.06. These differences are not considered significant, however, when considered in terms of the small differences in water applications (about 25 mm) to cause these changes in L_r. Evapotranspiration during each crop's growing season coincident with L_r was 410, 630, and 460 mm for barley, cowpea, and celery, respectively.