SWRT Enhancement of Water Use Efficiency and Economics of Irrigated Low Water Holding Capacity Sandy Soils.

Although supplemental irrigation, additional fertilization and manure applications do increase plant production on most sandy soils, farming sandy soils is not sustainable due to elevated leaching losses of nutrients, pathogens, veterinary pharmaceuticals and farm animal hormones to groundwater supplies. Expanding agroecosystems into sustainable plant biomass production systems for biofuels requires substantial increases in current agricultural lands by at least 70 million additional acres to achieve national goals for biomass-based ethanol production by 2025. Expansion of agricultural landscapes will undoubtedly include irrigated coarse textured marginal soils. Combining the natural hydropedological mechanisms for water retention with barrier-mediated water conservation technologies we will outline how the ‘leaky syndrome’ nature of sandy soils can be permanently ameliorated. Current knowledge-based mechanisms which trap and retain larger quantities of soil water in plant root zones for prolonged periods increase and sustain cellulose biomass production by 3 to 5-fold with concomitant water savings of 60 to 80% without leaching losses. The installation of contoured engineered polyethylene membranes will double the water holding capacities of most sandy soils enabling the production of 3 to 5 times more plant biomass which significantly increase soil C accumulations every 4-5 years. These new plant and soil technologies must be developed and proven before plant biomass production systems can sustainably produce more than the staggering projections of a billion metric tons of cellulose annually. Newly altered agricultural landscapes require substantial research and creativity before this nation can produce 107 billion gallons of ethanol needed to replace 75% of the annual consumption of 142 billion gallons of gasoline by 2050. These and other critical questions must be answered before sustainable biomass production systems can be expanded across large landscapes of sandy soils in the USA.