The effect of low and high fertility treatments on soil quality, yields, pest incidence and labor requirements of a post-transitional organic market garden system

In a two-year study, eight vegetable crops were grown as part of a certified organic four-year crop rotation. High input plots received off-farm composted cow manure and cover crops, and low input plots were managed with the use of cover crops only. High input plots produced higher yields than low input plots in all crops, except peas, which yielded higher in low input plots. Soil organic matter levels were significantly higher in the high input than the low input plots and increased from 2003 to 2004 in both treatments. Available soil phosphorus levels in the high input plots were excessive, while potassium levels were excessive in both treatments. The addition of manure-based composts can increase yields in a post-transitional organic market garden system. However, farmers should balance the costs of either production or purchase of compost against the benefits in yield, increased soil fertility, and possible negative effects associated with excess nutrients.