AGRONOMIC MODIFICATIONS OF A DRYLAND WINTER-WHEAT ENVIRONMENT RESULTING FROM GRAPHITE-NITROGEN APPLICATION TO SNOWPACK

Graphite, in an aqueous nitrogen (N) suspension of urea ammonium nitra te (UAN), was applied to snow covering dryland winter wheat in either February or March to determine impacts on wheat yield, soil temperatur e, available soil moisture, and N movement in soil. Field experiments were established on soils with slopes of 1-2% in both the Pocatello Va lley and Soda Springs areas of southern Idaho. Snow depths ranged from 40-65 cm at treatment application. Soil water content was determined with a neutron probe. Thermocouples were used to measure soil temperat ure in each plot following snowmelt from control plots. Soil water dif ferences were observed between the graphite treatment and the control to a soil depth of 90 cm in the spring. Soil temperature fluctuation f ollowing snowmelt was greater where graphite influenced snow melt. The re was a tendency for higher initial soil temperatures (above 0-degree s-C) with the graphite treatments compared with the control. These hig her temperatures were observed for over 20 days and to a depth of 20 c m. Increased wheat yields were observed with graphite-N applications o ver snow compared with similar fall or spring N application treatments . These higher yields were likely the result of increased soil tempera ture and soil water content as a function of controlled (pulsed) snow- melting with graphite.