Irrigation water quality options for corn on saline, organic soils

Summary

Corn production on the organic soils of the Sacramento-San Joaquin Delta of California was affected by the salinity of the irrigation water and the adequacy of salt leaching. Full production was achieved on soils that were saline the previous year, provided the electrical conductivity of the irrigation water (EC_i) applied by sprinkling was less than about 2 dS/m and leaching was adequate from either winter rainfall or irrigation to reduce soil salinity (ECM_SW) below the salt tolerance threshold for corn (3.7 dS/m). For subirrigation, an EC_i up to 1.5 dS/m did not decrease yield if leaching had reduced ECM_SW below the threshold. If leaching was not adequate, even nonsaline water did not permit full production. In agreement with previous results obtained in a greenhouse, surface irrigation with water of an electrical conductivity of up to 6 dS/m after mid-season (end of July) did not reduce yield below that of treatments where the salinity of the irrigation water was not increased at mid-season. Results also reconfirm the salt tolerance relationship established in the previous three years of the field trial. The earlier conclusion that the irrigation method (sprinkler or subirrigation) does not influence the salt tolerance relationship was also confirmed.