In irrigated agriculture, the amount and the timing of irrigation play a crucial role in obtaining a sustainable higher yield with minimum adverse effects on the environment. Insufficient irrigation on critical growth stages results in lesser crop yield than the genetic potentiality of a given variety; and excess irrigation leads to higher pumping cost, quick depletion of water resources, leaching of nutrients, and environmental pollution. Soybean is the second largest irrigated crop in ND, however, there is a lack of information on the optimum amount and timing of irrigation of this crop for western ND. In this project, irrigation treatments (amount x timing i.e. growth stage) will be applied using an automated linear system capable of variable rate application. The amount of water to be applied, as per treatments, will be determined based on available soil moisture, precipitation forecasts, current rainfall, soil infiltration rate, and crop growth stages. The research results will be communicated to clienteles through presentations at field days, workshops, and publications. The outcomes of this study will help soybean producers of ND, especially that of western ND, to determine irrigation schedules that enhance yield, water productivity, and soil health; thus, an increased sustainable high farm profit.

The main objective of this project is to determine the optimum amount and timing of irrigation for enhanced soybean yield, quality, and water productivity.
The secondary objectives are to assess the effect of irrigation treatments
- on soil health manifested by changes in soil physical and chemical properties, and
- on the manifestation of soybean diseases including but not limited to white mold.

i. A technical report on the outcomes of the project.
ii. An executive summary of the project.

Update:

View uploaded report

Research Conducted

Soybean variety ND 17009GT was seeded on May 27, 2022. The seeding rate was 195,000 PLS/ac with Row to Row distance of 30”. There were 12 irrigation treatments: I = Full irrigation; Wv = Deficit irrigation during vegetative [(VE – V(n)] stage; Wf = Deficit irrigation during flowering [R1-R2] stage; Wp= Deficit irrigation during pod development [R3-R4] stage; Ws = Deficit irrigation during seed filling [R5-R6] stage; Wm = Deficit irrigation during maturity [R7-R8] stage; Wvf = Deficit Irrigation during vegetative + flowering stages; Wvp = Deficit irrigation during vegetative + pod development stages; Wvs = Deficit irrigation during vegetative + seed filling stages; Wvm = Deficit irrigation during vegetative + maturity stages; Wsm = Deficit irrigation during seed filling + maturity stages; and R = rainfed.

Why the research is important to ND soybean farmers

The insights obtained from this research regarding appropriate irrigation amounts and timing will assist soybean producers in western North Dakota in applying the precise amount of water at the right moment. The ultimate advantages will include improved yield, quality, water productivity, and soil health, as well as reduced leaching, environmental pollution, and disease occurrence, leading to increased profitability for farms.

Final findings of the research

The NDVI and NDRE data from the aerial images showed that the senescence occurred at a higher pace in plots with treatment R, WP, and Wvp compared to others. The grain number per plant was lower for R (45) Wvf (48) compared to others that had 63 to 77 grains per plant. The soybean grains under treatments Wp and Wvp had the highest amount of protein (42.2%) followed by treatment R (40.3%). Other treatments had 37.9-39.8% of grain protein. The treatment Wsm produced the highest grain yield, which was statistically on par with treatments Wm, Wvm, Ws, Wvs, I, and Wv. A marked decline in soybean yield occurred under treatments wf, Wvf, Wp, Wvp, and R (Figure 1).

Benefits/Recommendations to North Dakota soybean farmers and industry

The findings of this study indicate a potential for conserving irrigation water while maintaining soybean grain yield, provided that the escaping of irrigation does not occur at the flowering and pod development stages. The North Dakota soybean farmers and industry can benefit from these findings by reducing irrigation management costs and mitigating environmental pollution, all while sustaining soybean yield and ensuring a prosperous future. To confirm and validate these results, we plan to replicate this study in FY 2023-24.

According to USDA FSA Crop Acreage Data of 2020, there were about 276,982 acres of irrigated cropland in North Dakota, and soybean was the second largest irrigated crop (63,686 acres) preceded by com (87,124 acres) and followed by beans (27,366 acres) (USDA-FSA, 2020). According to USDA's 2013 Farm and Ranch Irrigation Survey (USDA-ERS, 2020), about 82 percent of irrigated farms in North Dakota are using "condition of a crop by observation" followed by 56 percent using the "feel of the soil" as means of deciding when to apply water. These practices cannot be considered scientific as they are not based on quantified soil available water at different crop development stages and their relationship with growth and yield. One of the reasons for these practices is the lack of information on appropriate timing and amount of irrigation for a given crop, including soybean. Information on the appropriate amount and timing of irrigation from this research will help western ND soy producers to apply the judicial amount of irrigation at the proper time. The ultimate benefits will be an enhanced yield, quality, water productivity, and soil health, and decreased leaching, environmental pollution, disease incidence; thus, a higher farm profit.