Forage irrigation, drainage system first of its kind in Atlantic Canada

By DAN WOOLLEY

Nova Scotia Agricultural College’s engineering department is pioneering a unique, low-energy, combined irrigation and drainage system for forages and pastures. Engineering professor Dr. Peter Havard is working with a team of researchers and the NS Cattle Producers Association to develop less costly, more environmentally friendly ways to grow forages.

What makes the NSAC project unique is the combination of the irrigation and drainage systems in the same 4-inch sub-surface pipe. The project also uses pumps (smaller than conventional irrigation pumps) that have to build pressure for aerial sprinklers. Being a sub-surface system it also applies water more directly to the roots of forages.

The energy and water savings will be measured and the research jointly funded by Agriculture and Agri-Food Canada (AAFC) and the NS Department of Agriculture.

The research team—Drs. Havard, Alan Fredeen, Ali Madani, Blakrishnan Prithiviraj of the NSAC and Dr. Yousef Papadopoulos and John Duynisveld of AAFC—want to encourage livestock farmers to grow more forages and decrease their reliance on grain.

NSAC engineering technician Chris Nelson says the wiring, plumbing and trenching has been completed and tests are underway to fine-tune the system. The project’s objective will be to look at the best ways to recycle drainage water and nutrients to use water and energy more efficiently, he explains.

Other aims will be to store water during dry periods while maintaining and improving forage yields.
Nelson says using gravity to funnel drainage water from lateral drains laid along the contour lines of the pasture will ease the power load on the system’s pumps.

Any leachate from the field that ends up in the systems storage reservoir will be returned ultimately as nutrients in water from the reservoir pumped back in the irrigation pipes to roots of the forages, he notes. A small hut in the centre of the research pasture receives the water flowing from the drains in the field. It has low power pumps that then distribute the water to the storage reservoir. Nelson says control structures along the drains between the pump hut and the reservoir (and the field) contain adjustable gates to regulate the water level in the system so water will flow back into the perforated lateral lines to irrigate the pasture.

Summer student Joshua Dillman says the hut’s instruments will measure the amount of water flowing in the drain to the reservoir as well as computer monitoring and controlling the volume of the flow. The hut can both irrigate the pasture and fill the pond simultaneously.

Summer student Dave Sampson says it will have sensors to report water table depth, storage pond water depth, soil moisture content and eventually a weather station.

He says they hope to install a solar panel-powered wireless sensor network to eliminate cables in the field.
Summer student Yang Lin says data from the field to measure water table height will be collected by two GPS sites, four tensiometers and three small wells of perforated PVC pipe. The tensiometers will report whether the water is coming by gravity from the drains or up from the soil. The GPS will operate with various probes for computer mapping soil moisture content. Lin also says the drainage/irrigation system has three pumps, two sump pumps in the reservoir and a jet pump in the hut. The flow rate from the hut to the four trials plots in the pasture is about 34 liters per minute.

Dr. Havard says the four plots will meet the different research needs of several NSAC academic disciplines. "We are trying to get by with the water we collect in the spring."

Once the system begins operating in the pasture, he hopes it will extend the forage growing season by a month. The pasture cannot presently be grazed because its forages stop growing in late summer.
Researchers will test alfalfa, red clover, timothy and Kentucky bluegrass to see how well they grow with irrigation. They will also be able to mange both the site’s nutrients and test the water leaving from each plot. Scientists will also be able to study the weight gain and other health parameters of animals grazed on the pasture.

Havard says they will monitor the site for the next five years until the research pasture stabilizes following the drainage system’s installation, the plowing and re-seeding of the field.