The Koivisto estate, owned by Sami Suoja, is situated in the Sastamala municipality in SW Finland. The farm has about 200 hectares arable land, of which about 170 hectares is cultivated every year. The prime crop is oat, besides which Sami grows some barley, wheat, rape and small amounts of caraway and hay. “The soil types here vary a lot; the most challenging are silty clay and peat. About 40 hectares are peaty soils”, Sami estimates.

Controlled drainage

Sami is a qualified controlled drainage technician with 20 years’ firm experience from his homestead, where he applies controlled drainage techniques. “In principle, the method is simple and it is easy to learn, even for a beginner”, Sami encourages. In controlled drainage the water is dammed into a covered ditch network and the moisture of the field can be monitored to optimal growth conditions. Using the dam wells the water table is raised in spring during the sowing period and lowered in autumn before the harvest, as the crop no more needs any extra moisture. This method works fine on cultivated fields with peat soil.  The peat has rather efficient water holding capacities and stays moist with this method. Also, this prevents the subsidence of the peat, which otherwise would be harmful. Typically, as the peat field is flat, one dam well is sufficient for several field hectares”, Sami explains. At the Koivisto estate almost all peat soil fields are on controlled drainage areas.

Benefits and challenges with the method

On the Koivisto estate, controlled drainage has been a profitable investment. “Although you do not benefit from the system every year, its effect on the harvest level has been positive in the long run. The state environment protection subsidy also offers a small financial stimulation to assemble the system”, Sami tells. Besides, the controlled drainage retains nutrients and carbon in the soil, which is positive for the watershed protection. Sami also has a profound professional interest in the controlled drainage context, and a wish to constantly improve his work with various methods.

“The most serious drawback with the controlled drainage is the extra work with regulating the water levels, although it actually is rather easy”, Sami ponders, ”if the dam well is out on the field, it may hamper working there a bit”. The controlled drainage network needs little maintenance.

In the future Sami would like to see how the below ground automatic Watergate protection valves work on peat soil. “The valve dams less water than the traditional regulating dam, but the farmer doesn’t have to worry about its controls. On certain sites, it might prove extra useful, but will it endure the rust load from the peat?”, Sami wonders.