A Cropping Systems Approach To Improving Water Use
Efficiency In Semi-Arid Irrigated Production Areas
J.P. Mitchell1, C. Shennan, J.D. Rhoades, M.J. Singer,
D. Peters, T. Prichard, D. May, R.O. Miller, D. Munk, W. Graves,
and C. Thomsen1Kearney Ag. Center, 9240 S Riverbend
Ave, Parlier CA 93648
Reuse of saline subsurface drainage water for irrigation has been identified as a potential option for managing drainage volumes and sustaining crop productivity in California's San Joaquin Valley. However, soil surface structural instability, crusting and poor stand establishment may be constraints in drainage reuse systems. The objective of this field study was to evaluate the effectiveness of winter cover crop incorporation and gypsum applications, relative to conventional fallow, for improving soil physical properties, stand establishment and crop productivity in a cropping system relying on the cyclic reuse of saline drainage for irrigation. Six amendment treatments were imposed on a rotation of tomato-tomato-cotton as summer crops.
Tomato seedling emergence was improved following incorporation
of vetch in year 1 prior to saline irrigation application, but
was unaffected by amendment treatment in year 2. Following two
summer seasons in which saline drainage water was used for about
70% of the irrigation requirements, surface-applied gypsum significantly
reduced soil crust strength and improved cotton stand establishment.
Cover cropping decreased crust strength and increased soil aggregate
stability, but significantly decreased emergence rates and final
stand densities of cotton seedlings. Mechanisms accounting for
poor establishment following cover crop incorporation include
higher incidences of seed and seedling pathogen infection in plots
where cover crop residues had been incorporated into the soil,
and stubble-reinforced surface crusts that result in interconnected
slabs that impede timely seedling emergence. Yields of tomatoes
irrigated with saline water were maintained relative to nonsaline
irrigation in year 1, but were decreased by 33% in year 2. No
reductions in cotton lint occurred as a result of saline irrigation
in year 3. Soil electrical conductivity (ECe) increased from about
2 dS m1 to 6 dS m1, and soil B increased from 0.4
g g1 to 1.5 g g1 during the course of this 3-year
study despite leaching by winter rains.
Publications from this project: In prep.: Cover
crops for saline soils. J. Mitchell, W. Graves, C. Thomsen and
C. Shennan.
Cover Crop Research and Education Summaries