AUTHOR=Norgaard Amy E. , Lewis DeLisa , Borden Kira A. , Krzic Maja , Carrillo Juli , Smukler Sean M. 

TITLE=Trade-offs in organic nutrient management strategies across mixed vegetable farms in Southwest British Columbia

JOURNAL=Frontiers in Sustainable Food Systems

VOLUME=6

YEAR=2022

URL=https://www.frontiersin.org/journals/sustainable-food-systems/articles/10.3389/fsufs.2022.706271

DOI=10.3389/fsufs.2022.706271

ISSN=2571-581X

ABSTRACT=<p>Balancing economic and environmental objectives can present trade-offs for organic farmers maximizing crop yields while maintaining core principles of ecology and health. A primary challenge for achieving this balance is nitrogen (N) and phosphorus (P) management. Meeting crop N requirements with compost can build soil carbon (C) and soil health but often over-applies P and increases soil P and associated environmental risks. Alternatively, high-N organic fertilizers can provide N without surplus P but can be expensive and lack C inputs that composts supply. We evaluated these potential trade-offs in 2-year field trials on 20 mixed vegetable farms across three regions of Southwest British Columbia, Canada, capturing a range of climatic-edaphic conditions and organic amendments. Three nutrient management strategies were evaluated: <italic>High Compost</italic>: compost applied to meet crop N removal, <italic>Low Compost</italic> + <italic>N</italic>: compost applied to meet crop P removal plus an organic fertilizer to meet crop N removal, and <italic>Typical</italic>: varying combinations of composts and/or organic fertilizers (“typical” nutrient application on the farm). Nutrient strategies were evaluated in terms of yield, input costs, and soil properties [permanganate oxidizable C (labile C responsive to soil management), and post-season available N and P]. Soil P was 21% higher with <italic>High Compost</italic> than <italic>Low Compost</italic> + <italic>N</italic>. In one region characterized by inexpensive but nutrient-rich composts and soils high in P, input costs were lowest with <italic>Typical</italic>, but in the second year, <italic>High Compost</italic> outperformed <italic>Typical</italic> in crop yield. Principal component analysis showed a divergence in post-season <inline-formula><mml:math id="M1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mtext>NO</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow><mml:mrow><mml:mo>-</mml:mo></mml:mrow></mml:msubsup></mml:math></inline-formula> between nutrient strategies in relation to compost and soil properties: <italic>High Compost</italic> using high-N composts increased post-season <inline-formula><mml:math id="M2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mtext>NO</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow><mml:mrow><mml:mo>-</mml:mo></mml:mrow></mml:msubsup></mml:math></inline-formula> (0–30 cm), whereas relative yields in <italic>High Compost</italic> tended to be higher on farms with lower soil C and lower C:N composts, while yields with <italic>Typical</italic> were higher under opposite conditions but associated with higher post-season <inline-formula><mml:math id="M3" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mtext>NO</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow><mml:mrow><mml:mo>-</mml:mo></mml:mrow></mml:msubsup></mml:math></inline-formula>. Combining input types (e.g., <italic>Low Compost</italic> + <italic>N</italic>) can meet environmental objectives in reducing surplus soil P without short-term yield or cost trade-offs compared to <italic>High Compost</italic>. However, maintaining soil C needs to be investigated to achieve effective ecological nutrient management in organic vegetable production with improved nutrient balances.</p>