Submitted to: Peanut Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/7/2005
Publication Date: 8/15/2006
Citation: Rowland, D., R.B. Sorensen, K.S. Balkcom, and M.C. Lamb. 2005. Estimating stem water flow in peanut (Arachis hypogaea) under different irrigation methods. Peanut Sci. 32:81-90. Interpretive Summary: Water is becoming an ever more precious resource to farmers because of the dwindling supplies and the increasing costs associated with irrigation. This has forced farmers to become much more efficient at applying irrigation in order to be cost effective and competitive in the marketplace. One way to increase efficiency in production is to use alternative irrigation methods such as subsurface drip irrigation. Even though subsurface drip irrigation is supposed to be more efficient than overhead irrigation, very little has been done to compare plant water use between the two systems. We conducted a study comparing subsurface drip irrigation, overhead irrigation, and dryland production in order to determine: 1) daily peanut water flow differences among irrigation treatments, 2) if soil and other plant characters mirror plant water use, 3) overall plant growth differences among irrigation methods, and 4) water-use efficiency differences among irrigation methods. We found that there were large differences in daily plant water use among irrigation methods, with subsurface drip irrigated peanuts using more water than the other treatments. In addition, several environmental characteristics including soil moisture, soil temperature, and canopy surface temperature correctly predicted plant water flow. We also found that subsurface drip plants were overall larger in size with more leaves and stems, however this larger size did not translate into greater yields which indicated that subsurface drip plants had low water-use efficiency. However, we feel this may be due to the actual management scheme used to apply water in the subsurface drip irrigation.
Technical Abstract: The picture of water availability across most of the U.S. peanut producing areas is bleak and becoming worse every year. Years of drought and increasing urban drains on water resources are forcing producers to make do with diminishing irrigation stores. Increasing water-use efficiency is a major goal of most peanut producers in the southeastern U.S., and alternative irrigation methods, such as subsurface drip irrigation, are production methods aimed at achieving this goal. Although subsurface drip is purported to be more water-use efficient than overhead irrigation due to its decreased soil evaporation, quantifiable data determining the actual differences in plant water use among irrigation methods is lacking. We conducted a study comparing subsurface drip irrigation, overhead irrigation, and dryland treatments in peanut with the following objectives: 1) determine if daily peanut water flow differed among irrigation treatments, 2) determine what environmental parameters were most closely correlated with peanut water flow; 3) if differences in water use existed among irrigation treatments, measure the effect on biomass partitioning, growth, and yield; and 4) determine how seasonal water-use efficiency was affected by irrigation treatment. We found significant differences in daily water use patterns, average daily water use, and accumulated daily water use among irrigation methods, with subsurface drip irrigated peanuts using more water than the other treatments. In addition, several environmental parameters including soil moisture, soil temperature, and canopy surface temperature were significantly correlated with plant sap flow. The significant differences in water use were due primarily to differences in plant size with subsurface drip plants having more leaf mass, longer internodes, and overall larger canopies than either the overhead irrigated or dryland plants. Even though drip plants had much greater aboveground biomass than the other treatments, this growth did not translate into greater yields, indicating subsurface drip plants had low water-use efficiency. While our carbon isotope discrimination results did not definitively show this, the calculated values of harvest index based on average pod yield and measured water use did illustrate subsurface plants used water less efficiently. However, we feel this may be due to differences in actual management of water application between subsurface drip and overhead irrigation rather than to an inherent characteristic of drip irrigation.