Estimating Productivity of Forage Corn and Sorghum Under Various Irrigation Regimes.

Forages used to support western dairy systems have a very large water footprint. In California, for example, forages utilize over 20% of the state’s agricultural water.  Water use has been scrutinized given the long-term limitation of western water supplies, and periodic and extreme droughts. Corn silage is a major component of this forage system, but the water use for corn silage is substantial.  Forage systems which can adjust to lower seasonal supplies are needed.  An experiment was implemented in 2014 to examine water use efficiency and annual forage crop production under various water deficits.  This experiment compared corn and sorghum as well as 4 cultivars of each species and their interactions with irrigation practices.  Water was applied through a pivot irrigation system that was configured to deliver either 100%, 80%, 60% and 40% of full Evapotranspiration (ET) demand.  Soils are a clay loam, located in western Fresno County, a region entirely dependent upon irrigation during summer. Irrigation treatments were applied in concentric circles through nozzle configuration. The experimental design was a modified Randomized Complete Block Design with a split plot restriction with cultivar as a subplot, and unequal replication per block, 6 replications total. To account for any possible variability in irrigation uniformity along the pivot we blocked the irrigation treatments into three blocks, from top to bottom of the pivot. Within each of three blocks each irrigation treatment was repeated once.  Regression analysis was used to determine response to irrigation treatments, and interactions between variety, species, and irrigation practices.  The objective is not only to produce a maximum yield silage system with full water supplies, but to develop systems which produce acceptable yield and quality under water deficits.  Data on yield response to irrigation treatment, and interactions between variety and irrigation treatment will be presented.