The second year of the “3-4-5 Gallon Production Maximization (GPM) Project” was a year of further confirmation that pouring more water on a corn crop is not the best business decision for irrigated corn producers in the North Plains Groundwater Conservation District (NPGCD). A highlight of the program was one cooperator who produced a 200-plus bushel per acre (bpa) corn crop with only 2.5 gallons per minute (gpm) of irrigation available for the season. This demonstration topped both his 4 and 5 gpm plots by 12-18 bpa.
“This cooperator applied a management strategy including planting dates, seeding rates, and hybrid selection, in addition to soil health benefits from historical crop residue, that was specifically intended to increase yield potential at his lower irrigation capacity,” said Leon New, Project Lead for the “3-4-5 GPM Project”. While project coordinators recommend certain practices, many of the variables are at the discretion of the individual cooperating producers. Consequently, results vary from one demonstration site to another. However, even the varying practices and results provide valuable insight into best practices for maximizing the net return from the grower’s groundwater, based on his or her specific production and management goals.
The overview of the 2016 “3-4-5 GPM Project” shows that, with adequate rainfall, it is possible to grow 200+ bushel corn crops with limited irrigation. With rainfall ranging from 6.41 to 13.86 inches, all but one of the 3 gpm demonstrations were within +/- 5-percent of a 200 bpa yield. In fact, only 3 out of 10 of the 3 gpm plots fell below 200 bpa, with one site reaching 216 on only 13.57 inches of irrigation and a total of 22.35 inches of irrigation and rainfall. Soil moisture totals were not available at the time of this writing. One of the 3 gpm fields that did not reach 200 bpa experienced significant hail damage and other mitigating circumstances that negatively impacted yield.
The three year “3-4-5 GPM Project” builds on the district’s award winning “200-12 Project” that ended in 2014. Participants in the “3-4-5 GPM Project” are using variable rate irrigation (VRI) to simulate 3, 4, and 5 gallons per minute, per acre irrigation conditions in side-by-side, production-scale demonstrations. The “3-4-5 GPM Project” uses a comprehensive resource management approach including irrigation scheduling and management technologies, maximized delivery systems, conservation tillage practices, hybrid technology, and pest and nutrient management to optimize conditions for water savings and maximum yield.
“We learned from the various levels of irrigation used during the ‘200-12 Project’ that we were normally over-irrigating with 5 gpm, and the yields at 3 and 4 were not that much less,” said New. “The idea is that irrigators can strategically use less water, improve their irrigation efficiency and maintain profitable yields.” Producers with higher irrigation capacity can reduce the amount of irrigation applied through nozzle package adjustments or by use of VRI speed control.
Year two of this three-year project saw an even greater level of management through a variety of planting dates, seeding rates, hybrid selections and irrigation application methods, all aimed at increasing yield potential at lower irrigation capacities. Planting dates ranged from April 25th to June 12th with most of the fields planted in the last week of May 2016. One of the highest yielding demonstrations was the corn planted the earliest. The 3 gpm field yielded 231 bpa with only 14 inches of irrigation; however, this plot benefitted from the highest rainfall total of any in the project with almost 14 inches of in-season rain. This cooperator utilized an early-late planting combination with 3-4 weeks between plantings and an irrigation capacity of 3.14 gpm per acre on 180 acres of corn. He learned the technique during the “200-12 Project”.
Seeding rates ranged from 26-38,000 seeds per acre, but yields did not increase proportionately without the application of a disproportionate volume of irrigation water for the highest seeding rates. The resulting increase in input costs from seed, irrigation, fertilizer and harvest will reduce any increase in revenue and cause a reduction in overall efficiency.
Hybrid selection strategies ranged from using high yielding, drought tolerant varieties, to focusing on high ear-flex varieties. Varieties with enhanced ear-flex can grow larger ears, and therefore, increase yields if additional water is available. On the other hand, many of the higher yield, drought tolerant varieties tend to have more of a fixed ear size. Ear-flex allows the grower to reduce seeding rates, and therefore, the water requirement, while allowing the opportunity to take advantage of any additional rainfall.
Year two also marked the first year of the side-by-side comparison between subsurface drip irrigation (SDI) and Low Energy Precision Application (LEPA) center pivot irrigation. LEPA applies the irrigation water in a bubble or similar pattern no more than 18 inches above the soil using drop hoses. It is reported to reach application efficiency levels of 95 percent. SDI uses drip lines buried in the ground delivering water directly to the crop root zone. This demonstration was located at the North Plains Water Conservation Center (WCC). The WCC provides the opportunity to compare the two high- efficiency systems side-by-side. In the 2016 side-by-side comparison, the LEPA system out-performed the SDI by an average of about 8 bushels per acre. “In only the first year of the comparison and operation of the SDI system at the WCC, these numbers are not conclusive,” said New. “More data is necessary, but this is valuable information for beginning to understand these systems better in terms of water efficiency, yield performance and cost feasibility.” These demonstrations are made possible by the district’s corporate partner, Crop Production Services in cooperation with WCC farm operator and demonstration cooperator, Stan Spain.
Finally, the district continued demonstrations initiated in 2015 to compare Precision Mobile Drip Irrigation (PMDI) to LEPA. PMDI involves drip hoses being pulled around the field by the center pivot system and applying the irrigation directly to the soil. While there were some technical problems with the PMDI comparison in 2015 that negatively impacted results, in 2016 the PMDI out-performed LEPA by an average of 10 bpa. More data is still needed to develop any definitive conclusions, but this year’s PMDI results are promising.
Overall, New says the increased efficiency that is possible by reducing the amount of water used to grow corn creates options and opportunities for growers. “On one hand, by managing production cost through irrigation, seeding rates, hybrids, and fertility, in combination with strategic crop residue and soil practices, growers may put more money in the bank, while leaving water in the ground and some profit on the table for later,” said New. “On the other hand, a grower with adequate capacity may seize the opportunity to operate more efficiently, but over more acres, putting more money in the bank now.” New summarized by saying this demonstration project presents district growers, and all who see these results, with the question, “Where, how and when will I use my water?”
The “3-4-5 GPM Project” is in the second year of a planned three-year initiative. The final report for 2016 should be available later this year at www.northplainsgcd.org.