Furrow Diking for Improved Irrigation Efficiency
During the past several years, the MSPB funded the RISER project (click here for project final report) that was conducted under the leadership of Dr. Jason Krutz, now the Director of the Miss. Water Resources Research Institute. This project investigated various technologies or best management practices (BMP’s) that potentially can be used to increase irrigation efficiency and thus minimize or stop the decline in the water level of the Mississippi River Valley Alluvial Aquifer (MRVAA), which is the primary water source for Delta-wide crop irrigation.
One technology that was investigated in this project is furrow diking (FD), which is a soil and water conservation practice that uses small earthen dams to create basins within the length of furrows between ridged rows of a crop. The distance between the dams or dikes can vary based on soil type and the anticipated amount of water received from rainfall and/or irrigation. The purpose of furrow diking is to hold water within the furrow for an extended period to reduce runoff and allow for increased infiltration into the soil. The intent is to increase storage of plant available water in the soil. The practice can be applied to both dryland and irrigated fields.
In a published article by Bryant et al. (CFTM Apr. 2019), results from two years (2011-2012) of studies that investigated FD in dryland (nonirrigated) and furrow-irrigated soybeans are presented. A summary of those results follow.
• The study site was a Dundee silt loam with 0-2% slope. This soil series is prone to surface crusting.
• Treatments consisted of FD and no furrow diking (ND). Furrow diking was completed in the spring each year.
• A MG IV soybean variety was planted on 15 April 2011 and 10 April 2012.
• In the irrigated study, irrigation was applied when a 2-inch soil water deficit occurred. Irrigation rates were 75 and 100% evapotranspiration for FD and ND, respectively. Irrigation water volume was measured at each application.
• Application of FD vs. ND had no effect on soybean seed yield in either the nonirrigated (37.6 vs.38.6 bu/acre) or irrigated (54.6 vs. 56.4 bu/acre) studies.
• Less irrigation water was applied to the FD treatment (11.5 acre-inches) vs. the ND treatment (15.5 acre-inches) in the irrigated study to achieve a similar yield of 54.6 vs. 56.4 bu/acre.
• In the irrigated study, FD increased irrigation water use efficiency (IWUE) by 28% vs. the irrigated ND treatment.
• Total revenue and net returns above FD costs were not different between the FD and ND treatments in either the irrigated or nonirrigated studies. Thus, these results indicate that costs associated with the purchase and operation of the FD equipment are offset by savings due to reduced irrigation application.
• The results from this research indicate that 1) 25% less water can be applied to FD systems without compromising seed yield, and 2) FD improves IWUE, in this case 28%, with no adverse effect on soybean seed yield or net returns above FD costs.
• The authors concluded that FD should be a recommended BMP to improve furrow irrigation efficiency in the Delta to reduce water withdrawal from the MRVAA.
Caveat: This study applied FD’s to a crusting, non-shrinking soil. On a shrinking clay soil such as Sharkey clay (prominent in the Delta), FD’s will understandably be less likely to remain in place when the cracks in the soil will cause the dikes to collapse. Thus, this practice may not be as applicable on these shrinking clay soils if dikes have to be reconstructed during the growing season.
Composed by Larry G. Heatherly, Mar. 2020, larryheatherly@bellsouth.net