Effect of Optimal Water Management for Sustainable and Profitable Crop Production and Improvement of Water Quality in Red River Valley

View the project final report

• 2012 annual report
• 2013 annual report
• 2014 annual report

Commodities

• Agronomic: corn, soybeans, sugarbeets

Practices

• Crop Production: irrigation, nutrient cycling
• Education and Training: decision support system, demonstration, display, extension, farmer to farmer, focus group, mentoring, networking, on-farm/ranch research, participatory research, workshop
• Farm Business Management: whole farm planning, value added
• Pest Management: chemical control, field monitoring/scouting, weather monitoring
• Soil Management: soil chemistry, soil physics, soil quality/health
• Sustainable Communities: local and regional food systems, urban/rural integration, employment opportunities, sustainability measures

This research and education project evaluated the crop yield, water quality and water balance for four different fields, undrained (UD), subsurface drained with free outlet (FD), subsurface drainage with controlled drainage structure (CD), and CD plus subirrigation (SI). From 2012 to 2014, the crop yields showed some promising improvement with the dual CD and SI system setup despite the extreme wet and drought conditions during the experimental period. Water quality monitoring showed that the CD retained the drainage outflow and improved the water quality comparing to the FD when most rainfall occurred in spring and early summer. However, when rainfall occurred in summer and early fall of 2014, the effect of CD on water quantity and quality control was not significant better than that in the FD field. The economic analysis showed that with only $45 input per acre per year, the dual CD and SI would be paid back in few years because at least 10% yield increase between CD and SI for all three years, and 25% yield increase for SI in two of the three years have obtained. The water balance for the four fields also showed that with only 1.79 inches of water supply for 13 days in July and August, the SI field had minimal deficiency between inflow and outflow, and created an optimal soil water regime for the crop. Enormous educational opportunities were also provided for university students, staff, and faculties, land owners, governmental personals by the research team, collaborators, and most importantly, the participating landowners.

Introduction:

In the last decade, following a wet weather pattern in the Red River Valley of the North (RRV) of eastern North Dakota and northwestern Minnesota, subsurface drainage has become the most effective way to combat excess soil water in farm fields. Subsurface drainage (often called tile drainage) uses perforated conduits to remove excess water from the soil in a field. This results in improved field trafficability in the spring and fall, increased crop yields, and reduced prevented planting acres. These benefits have accelerated subsurface drainage installation in the last 17 years in the RRV.

It is well known that subsurface drainage water can contain high nitrate-nitrogen (NO₃-N) during certain periods of the growing season. The elevated NO₃-N in the tile discharge water can contaminate surface water systems. Leaching of NO₃-N also implies a loss of N fertilizer from farm fields. Many subsurface drainage systems in the RRV either have a gravity outlet or use a lift station. These are uncontrolled or free drainage (FD) systems. Using control structures or weirs to hold the subsurface water in the drained field can minimize the amount of water removed from the field in late spring and reduce the loss of NO₃-N. This practice is called controlled drainage (CD). Additionally, with a reliable source, water can be added to the field through subirrigation (SI) during high crop water demand periods such as in July and August. The dual CD-SI system is expected to allow for a higher crop production and increase the farmer’s net income if proper water management practices are applied.

When using CD, the amount of water leaving the field is reduced which results in less NO₃-N leaving the field. In the RRV the major surface-water quality problems are high phosphorus (PO₄-P) and sedimentation. When water in the drainage ditch is used as the SI water source, PO₄-P and solid particles are filtered out to stay either in the soil, or outside the field. With proper CD and SI practices, it is possible to achieve an optimal soil water status in the farmer’s field and obtain an economic benefit.

Under normal weather conditions, FD, CD, and SI could all be practiced on the same field at different times of the season while the crops in undrained fields (UD) may suffer from waterlogging stress. However, every growing season is different and there may be times when crops may not need SI water if the soil has sufficient moisture. On the other hand when extremely dry conditions occur the UD field may provide a better subsurface moisture condition for the crop in spring and the SI system could provide additional water to crops during the growing season to combat drought stress. The dual CD and SI system has been shown to increase crop yields in both dry and wet years and can potentially reduce the impact to surface water quality.

For this project, our objectives were to (1) optimize water management through a CD and SI system on a farmer’s production field; (2) compare yield differences between UD, FD, CD, and CD+SI fields; (3) monitor water quality (e.g. NO₃-N, PO₄-P, turbidity, salinity, etc.) and quantity for fields with different water management practices; and (4) estimate the total annual water balance in the UD, FD, CD, and CD+SI fields.