Integrated approach to nitrogen fertilization for profitable organic potato production and a balanced phosphorus budget

Description

Organic potato farming accounts for only 0.3% of the total potato growing area in Québec (CARTV 2012). Recent consultations with a number of producers and extension agents revealed the lack of an established, effective nitrogen fertilization program that ensures a balanced phosphorus budget. Since potatoes have high nitrogen requirements, using manure to meet this need leads to phosphorus saturation of the soil and its use is necessarily limited on phosphorus-rich soils. The problem is particularly severe with potatoes because fresh manure cannot be used because of the risk of potato scab while composting reduces effective nitrogen content and concentrates the phosphorus. Pelleted chicken manure offers an alternative because it is high in effective nitrogen, but it is costly and also high in phosphorus. So there is a great need to test green manure as a main source of nitrogen. An added benefit is that green manure helps maintain soil quality and control weeds. Testing and validating a nitrogen fertilization program will support the transition to and expansion of organic farming in line with MAPAQ’s strategy in that regard.

Objective(s)

• Develop a fertilization program including green manure and animal manure that delivers the nitrogen that potatoes require and ensures a balanced phosphorus budget without increasing disease or weed incidence
• Determine:
  • The amount of nitrogen and phosphorus inputs from green manure and pelleted chicken manure
  • Nitrogen and phosphorus dynamics in the soil
  • Total nitrogen uptake and yields
  • Tuber quality, disease incidence, and weed populations
  • Soil quality at the end of the rotation
• Compare revenues and costs