Effect of Compost Application Rates on High Tunnel Tomato Yield

Compost application has become a cornerstone of soil health and soil improvement practices on many farms in the Northeast, particularly in high tunnels.  However, the lack of researched-based information on compost application rates has led to excessive applications of compost and resultant accumulations of phosphorus and salts in the soil.  High compost rates have broad ranging effects on soil health and quality and may have significant impact on irrigation needs. For example, insufficient irrigation may lead to salt accumulation in the root zone of compost-amended soils. The objectives of this experiment were: 1) to investigate possible interactions between irrigation frequency and compost application rates; 2) develop baseline data for recommendations regarding compost application within high tunnels.

The study  employed two irrigation treatments:: one designed to mimic “typical” grower practices( 2-3 irrigation events per week lasting between 1 and 2 hours), and a  second treatment to provide the equivalent of 1 acre inch of water to the crop split into 2 irrigation events per day.  Five compost application rates: control (0 compost + N-P-K), 10, 20, 55, 90 yd³/acre were randomly assigned within each irrigation main plot. ‘Big Beef’ tomato seedlings were transplanted at 15” spacing.  The plants were trellised and pruned to a single stem. Yield (number and weight of fruit graded as first, second and cull) was measured from the center four plants of each plot. At the end of the growing season, stem fresh and dry weights were recorded for each plant.  

 No differences fruit yield were detected between irrigation treatments. Possibly due to the frequent high rainfall events which occurred through the summer.  Fruit number was significantly lower in the 10 yd³/acre compost treatment compared to the 20, 50 and control treatments. No significant differences were seen among the 20, 50, 90 yd³ or control treatments. However, fruit number and weight were lower in the 90 yd³ treatment compared to the 20 or 50 yd³ treatments, suggesting an over-application of compost. These data indicate that compost application rates greater than 20 yd³/acre have no additional beneficial effect on yield. This experiment will be repeated during the 2014 growing season.