Long-Term Effects of Compost Amendments and Brassica Green Manures in Potato Cropping Systems on Soil and Crop Health and Productivity

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Abstract
Beneficial soil and crop management practices, such as longer rotations, cover crops and green manures, organic amendments, and reduced tillage, may improve soil and crop health and productivity when incorporated into cropping systems. Long-term trials are needed to assess the full impacts and effects of these systems. In field trials originally established in 2004, three different 3-yr potato cropping systems focused on management goals of soil conservation (SC), soil improvement (SI), and disease suppression (DS) were evaluated and compared to a standard 2-yr rotation (SQ) and a nonrotation control (PP). After 12–15 years and results compiled over a four-year period (2015–2018), the SI system (with history of compost amendments) increased total and marketable tuber yields relative to all other systems, with yields averaging 26 to 36% higher than the standard SQ system and 36 to 59% greater than PP. SI also improved soil properties such as organic matter and soil water content, nutritional characteristics, and microbial activity compared to the other systems. The SI system continued to provide these improvements several years after compost amendments ended, indicating the long-term benefits. The DS system, which included a disease-suppressive green manure rotation crop and fall cover crops, also improved yield (by 16–20%), had higher organic matter content (by 12%), and increased microbial activity (by 22%) relative to SQ, as well as reducing the soilborne tuber diseases black scurf and common scab by 10–30%. The nonrotation PP system resulted in the notable degradation of soil properties and yield over time. These results demonstrate that soil health management practices can be effectively incorporated into viable potato cropping systems to improve soil properties and crop health, and may enhance long-term sustainability.

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