Quantifying nutrient recovery efficiency and loss from compost-based urban agriculture

Area of Science:

• Urban ecology
• Soil science
• Sustainable agriculture

Background:

• Compost use in urban agriculture (UA) recycles nutrients but often leads to excessive phosphorus (P) application.
• Management goals like maximizing crop yields or nutrient recycling can inadvertently cause P loss, creating ecosystem disservices.

Purpose of the Study:

• To investigate the impact of different compost types and application rates on crop yield and P loss in UA.
• To evaluate tradeoffs between nutrient recycling and potential environmental impacts in urban farming systems.

Main Methods:

• Experimental study over two years with four crops in raised beds.
• Applied municipal or manure-based compost at N-demand or P-demand rates.
• Included synthetic fertilizer and no-amendment controls, measuring crop yield and P leachate.

Main Results:

• Compost applied based on nitrogen (N) demand resulted in P overapplication due to low N:P ratios.
• Crop yields were similar across compost treatments, but P recovery decreased with higher compost rates.
• P leachate rates were double in treatments receiving compost targeted to N demand.

Conclusions:

• Targeted compost application in UA can maintain crop yields while minimizing P loss.
• Careful nutrient management is crucial for scaling up UA to avoid ecosystem disservices from nutrient pollution.
• Optimizing compost application balances nutrient recycling benefits with environmental protection.