Cumulative effect of leaf compost on yield and size distribution in onions

For three years, a one inch layer of leaf compost was applied to plots on a sandy terrace soil in Windsor, Connecticut and fertilized with 1300 Ib 10-10-10/A (N-P2O5- K2O). Yields of four cultivars of onions (Allium cepa L.) (3 Spanish, 1 storage) from these plots were compared to yields from unamended control plots fertilized at the same rate. Year to year variability in yields was significantly lower in compost-amended plots. Yields from the unamended control plots (52% variation) fluctuated more than the compost-amended plots (3% variation) in response to variable rainfall from year to year. After three years of compost additions, yields from the compost-amended plots of the three Spanish onion cultivars were significantly greater than yields of these cultivars grown in unamended plots. The greater yields were due to both increased bulb weight and greater percent harvested. In two of three years, the compost-amended plots produced a greater percentage of colossal and jumbo sized onions in all cultivars. Repeated compost additions also reduced the incidence of soft rot disease, especially in susceptible cultivars in years with higher than average precipitation.