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Cover Crops and Compost Influence Soil Enzymes during Six Years of Tillage‐Intensive, Organic Vegetable Production
Author(s) -
Brennan Eric B.,
Acosta-Martinez Veronica
Publication year - 2019
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2017.12.0412
Subject(s) - cover crop , compost , agronomy , tillage , cropping system , soil organic matter , crop , environmental science , biology , soil water , soil science
Core Ideas There were large differences in soil enzyme activities within organic systems. Compost and annual cover crops increased activities of most soil enzymes. Activities of most soil enzymes were correlated with microbial biomass. Cover crop type did not influence soil enzyme activities. The results show the soil health benefits of frequent cover crops in vegetable systemsSoil enzymes are considered sensitive indicators of soil health but are not well understood in tillage‐intensive vegetable systems. The activities of soil enzymes involved in nutrient cycling (β‐glucosidase, β‐glucosaminidase, alkaline phosphatase, dehydrogenase, aspartase, and L‐asparaginase) were evaluated during 6 yr of commercial‐scale production in five organic vegetable systems in Salinas, CA. The systems differed in yard‐waste compost inputs (none or 15.2 Mg ha –1 yr –1 ), winter cover crop frequency (annually or every fourth year), and cover crop type (legume‐rye, mustard, or rye). Large differences in cumulative organic matter input (7.4 to 136.8 Mg ha –1 ) from compost and cover crop shoots affected soil enzyme activities. With exception of aspartase, all enzyme activities were on average lowest without compost, intermediate with compost and infrequent cover cropping, and highest with compost and annual cover cropping. After 6 yr of vegetable production there was a positive relationship between microbial biomass and activities of all enzymes except aspartase. Despite lower inputs of cover crop shoot biomass from mustard compared with rye and the legume‐rye, and differences in shoots residue quality, cover crop type had relatively little influence on enzyme activities. We conclude that soil enzyme activities were influenced primarily by annual cover cropping. These results and other attributes of soil health in this long‐term study illustrate the importance of frequent cover cropping in tillage‐intensive vegetable production. This raises questions about the sustainability of organic and conventional vegetable systems if cover crops are seldom used, and highlights the need for innovative strategies to increase cover cropping.