Nitrogen Availability from Compost in High Tunnel Tomato Production.

High tunnel use for tomato cultivation is on the rise in the northeastern U.S. Use of high tunnels both extends the growing season and increases yield.  Compost is frequently used in high tunnel tomato production to supply nutrients and improve soil quality.  While various studies have looked at the use of compost to supply N in field soils, fewer studies have assessed the effectiveness of compost in high tunnels, where both temperature and soil moisture may be relatively high.  In this experiment, four finished composts from commercial producers in Maine were analyzed for nutrient content, pH, conductivity, lignin, and soluble C.  A field study with a randomized complete block design (four replications each in a separate high tunnel) was used to compare the four compost treatments with an unamended control and a control receiving inorganic N .  Composts were all added at the rate of 270 lb. of total N acre^-1, while inorganic fertilizer was added at the rate of 100 lb. N acre^-1.  Tomatoes were grown using these treatments at the Maine Agricultural and Forest Experiment Station Farm in Monmouth, ME during the summers of 2013 and 2014.  Soil nitrate (NO₃^- ), ammonium (NH₄⁺), and moisture were measured throughout the growing season, along with total marketable tomato yield and tomato N uptake at the end of the season.  Composts had significantly different properties.  In 2013 compost treatments affected early season soil NO₃^- and NH₄⁺, and total marketable yield, and composts with high levels of inorganic N produced higher total marketable yields. Relationships between compost properties and N availability were examined.