Impacts of soil‐borne disease on plant yield and farm profit in dairying soils

Abstract Introduction Globally, soil‐borne plant pathogens are a significant contributor to yield loss in agricultural systems, including pasture production. The extent of soil biological constraints high‐value dairy systems was assessed across three major dairying regions New Zealand. Materials and Methods Regional measures disease pressure were obtained by comparing white clover, perennial ryegrass plantain growth 30 farm soils with (non‐pasteurised) or without (microwave pasteurised) their normal complement microbial nematode pathogens. Results Pasteurising from the Waikato region led average increases clover (35%) (19%) shoot dry matter. Individual site yields increased up 74% for 38% ryegrass. For Canterbury Southland, there no increase pasteurisation on regional basis, but either at individual sites. Across all regions, negative linear relationships between (% change) proxy organic matter quality (anaerobically mineralizable nitrogen:total nitrogen ratio found both ryegrass, accounting 34% variation growth. A positive relationship Heterodera cyst abundance, 33% 17% change, respectively. most prevalent putative fungal oomycete isolated roots stem bases seedlings Fusarium oxysporum , culmorum various Pythium species. Conclusion Our results suggest that root Zeland farms damaging where economic modelling estimated cost 211 kg MS ha −1 year milk production $909 profitability. Given scale these costs, targeted management borne could present an economically viable approach improving resilience multi‐plant multi‐pathogen ecosystems.