Irrigation Practices for Water Conservation
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.
During the course of this project, various technologies known to reduce the amount of irrigation water applied to a soybean crop and subsequently improve irrigation water use efficiency (IWUE) were integrated into a set of studies in Mississippi and Arkansas in 2013-2015. The details of this research and results from it are presented in CFTM 2017. A summary of those activities and results follow.
• Research was conducted on paired fields in Arkansas and Mississippi. Within each set of paired fields, one was randomly assigned for conventional (CONV) furrow irrigation and the other was assigned for irrigation using water management (IWM) practices of computerized hole selection (CHM) using PHAUCET, surge flow irrigation (SURGE), and irrigation scheduling with soil moisture sensors.
• Each set of paired fields had the same soil texture, and variety, planting date, and all other management practices were identical within each set of fields. Furrow irrigation was applied to both CONV and IWM fields using lay-flat, thin-walled polyethylene tubing.
• Irrigation water was applied to IWM fields when the average soil water potential in the 0-24 in. soil depth was between -85 and -100 centibars. Irrigation on IWM fields was terminated when soybeans reached stage R6.5.
• Economic analysis was conducted for both CONV and IWM fields using the Miss. State Budget Generator. Well/lifting depths of 18, 140, 200, and 400 ft. were used to estimate costs dependent on those depths. Diesel cost of $2.83/gal. and soybean price of $11.11 were held constant across the 3 years.
• Amount of irrigation water applied, soybean seed yield, IWUE, and net return above irrigation costs were calculated each year.
• 85% of the irrigators applied more water using CONV than was applied to the IWM fields. 21% less irrigation water was applied to the IWM fields vs. the CONV fields. The allowed water withdrawal was not exceeded in Miss. IWM fields, while 10% of the CONV fields exceeded permitted withdrawals.
• Soybean seed yield was the same–69 bu/acre–in both CONV and IWM fields.
• Integrating the three water saving technologies into the IWM fields increased IWUE by 36% vs. CONV.
• Estimated net returns above irrigation costs for CONV and IWM were nearly identical at all irrigation water-lifting depths used in the study.
• The additional costs associated with the equipment needed to use IWM technologies in this study were offset by reduced irrigation water applied and lower total irrigation costs.
• These results indicate that 1) adoption of IWM technologies for furrow irrigation of soybeans in the Midsouth will have no adverse effect on either soybean seed yield or irrigation costs, 2) IWM technologies can be adopted by Midsouth soybean producers without adversely affecting on-farm profitability while concurrently reducing the demand for water from the declining MRVAA, and 3) adopting these IWM technologies for soybean irrigation will reduce the probability that producers will exceed the permitted withdrawals established by the Miss. Dept. of Env. Quality.
• Finally, at the farm level, improved irrigation efficiency provided by these IWM technologies 1) will reduce the period of time for a well to be obligated to a particular field, thus improving on-farm irrigation capacity, and 2) will have regional implications if adopted on a region-wide basis to reduce or stop the overdraft from the MRVAA.