Gypsum is added to irrigation water to increase soil intake rates in some areas of California. More than a third of a ton of this compound is already present in each acre foot of irrigation water as it is delivered to farms in the Imperial Valley. Tests were conducted at the Imperial Valley Field Station to determine whether the addition of other soil amendments would increase the soil intake rates. These tests were conducted with three compounds commonly used by growers in the area as soil amendments: calcium polysulfide, ammonium polysulfide, and sulfuric acid. Water treated with these compounds was compared with untreated water in a randomized block design. Only ammonium polysulfide produced a significant increase in soil intake rates.

This study was a cooperative evaluation supported in part by Project 2382.