Seasonal Moisture and Nitrogen Availability in Organic Potato Production as Affected by Organic Amendments

Dr. Derek Lynch, Dr. Bernie Zebarth, Claude Berthélémé, and Susan MacKinnon

Currently there is an increased demand for organically produced potatoes that are suitable for processing markets. As production expands to meet this demand, intensity and nutrient use in organic potato production will likely be affected. There is also an increasing availability of commercial soil amendments that are acceptable to organic certifiers (e.g. pelletized dehydrated manures and bulk composts), and these may differ in their affect on moisture and nitrogen availability to the potato crop. For example, compost applications may benefit yields directly, through increased soil moisture retention, or indirectly, by influencing soil N processes. However, various composts or manures applied prior to planting may differ significantly in their ability to supply nitrogen through the critical period of high crop N demand following hilling.

To keep pace with these developments there will be a need for research quantifying the effects of various soil amendments on soil moisture and nitrogen availability throughout the growing season. This will allow organic producers and advisors to develop organic potato production systems that make the most efficient use of applied nutrients.

The effects of various organic amendments on the availability of soil moisture and nitrogen throughout the growing season is the focus of a 3-year study by researchers at the Organic Agriculture Centre of Canada, Agriculture and Agri-Food Canada, the New Brunswick Department of Agriculture, Fisheries and Aquaculture, and the Prince Edward Island Department of Agriculture and Forestry. The study will evaluate the effects of five soil amendment treatments:

• Control: 0 kg N applied per hectare;
• Treatment 2: Hog manure/sawdust compost applied at 300 kg total N/ha;
• Treatment 3: Hog manure/sawdust compost applied at 600 kg total N/ha;
• Treatment 4: Pelletized chicken manure (Nutriwave 4-1-2) applied at 300 kg total N/ha; and
• Treatment 5: Pelletized chicken manure (Nutriwave 4-1-2) applied at 600 kg total N/ha.

The five amendments will be tested on the varieties Shepody and Kildare (the provisional name of McCains unregistered variety) at the following locations:

• Brookside, NS (OACC/NSAC site); and
• Kentdale Farms, Winslow, PEI.

In addition, a variation on these treatments will also be evaluated at three other farms:

• P. Kummer (Port Elgin, NB);
• K. Davidge, (Keswick Ridge, NB); and
• R. Loo (Kensington, PEI).

Repeated sampling of soil moisture, soil mineral N, and crop tissue N will be used to characterize the dynamics of soil moisture and N availability for the different amendment treatments. The research will also assess the effects of the different amendments on tuber yield and quality, including tuber nitrate levels, and on the potential for nitrate losses from the soil.

Researchers:

Dr. Derek Lynch (Contact)
Research Professor
Organic Agriculture Centre of Canada
P.O. Box 550
Truro, NS B2N 5E3
Contact: E-mail dlynch@nsac.ca
Tel: 902-893-7791

Dr. Bernie Zebarth, Research Scientist, AAFC Potato Research Centre, Fredericton, NB

Claude Berthélémé, Organic Specialist, NB Department of Agriculture and Fisheries

Susan MacKinnon, Organic Specialist, PEI Department of Agriculture and Forestry

Funding partners:

This research was made possible by the financial support of the PEI Dept. of Agriculture and Forestry and the NB Dept. of Agriculture, Fisheries and Aquaculture. The assistance of Envirem Technologies Inc. of Fredericton, NB and Agrior Inc., St. Patrice de Beaurivage, QC is also acknowledged.