Sub-Surface Water Retention Technology (SWRT) Membranes for Crop Improvement on Coarse-Textured Soils.

Irrigation water sources are facing declines and greater competition by municipal, industrial and commercial interests. Droughts, limited water supplies, soil erosion, shortages of agricultural lands for sustainable production of food and cellulosic biomass combined with increasing nitrogen fertilizer costs require the commercialization of a new long term soil technology that provides conservation of soil water and nutrients with a focus on marginal soils. Recent developments in the new soil water retention technology (SWRT) incorporate multiple environmental safeguards designed to increase plant available water contents and provide multiple ecosystem services. SWRT water impermeable membranes double VWC in the root zone for longer periods of time in a manner that reduces plant drought and are designed to prevent soil flooding during excessive rainfall. Greater quantities of uniformly distributed plant-available water and nutrients promote aboveground plant growth by reducing photoassimilate losses by plant roots experiencing high turnover and regrowth rates during frequent brief and longer droughts followed by rainfall. During the 2012 severe drought weather in Michigan, strategically installed soil water retention membranes combined with prescription applications of supplemental irrigation increased maize grain production 75% (from 9.8 to 17.1 MT/ha) and total plant biomass production 93% (from 18.1 to 35.0 MT/ha) when maize rows were planted at 38 cm row spacing and 15 cm in-row spacing. SWRT membranes also increased vegetable crops by 38 to 43%. In 2013, irrigated maize growing on SWRT membranes produced 238% more grain than non-irrigated controls without water retention membranes. Crop production increases have been linked to doubling shoot to root ratios, greater harvest index, more available nutrients and water and higher IWUE. Current research focus is quantifying improved rates of soil C sequestration and nutrient leaching into groundwater. Life cycle analyses of 27 production components associated with SWRT membrane installations and maize production demonstrate that returns on investment costs for membrane installation can be fully recovered in 4 to 5 years for maize and less that two years by horticultural crops. The United States Department of Agriculture (USDA) estimates 162 million hectares of highly permeable USA soils can be converted into sustainable agricultural production landscapes and FAO estimates 3.7 billion hectares globally. We believe SWRT coupled with SDI can reduce irrigation costs while continuing to increase crop yields.