Organic Heirloom Tomato Response to Surface-applied High Poultry Compost Level

Poultry compost application to cropland is known as an inexpensive way to provide nutrients such as nitrogen to plants. However, environmental factors such as rainfalls may decrease the availability of nutrients to crops while increasing their runoff to water bodies.  A  field study was conducted in 2014 to evaluate  the response of two organic heirloom tomato cultivars, Debarao Plum and Brandywine Red on soils  that were surface amended with the following four treatments of high compost levels and vesicular arbuscular mycorrhiza (VAM); control, VAM at 5 g/m² , compost at 3.375 tons /acre  and  VAM plus compost. Plants from the poultry compost treatment generally had highest leaf chlorophyll content, shoot height, and number of branches in the vegetative and reproductive phases. During the first seven weeks after transplanting, plants experienced excessive rainfall of 19.4 cm; thereafter, all plants exhibited purple leaf coloration and leaf chlorosis. Although tests of soils and leaves showed no phosphorus deficiency, nitrogen deficiency was reported. The harvested tomatoes and the plant biomass from high compost treatments were significantly higher in yield and biomass than those from the treatments without compost. These results imply that a more efficient method of application than surface application should be investigated to optimize the usage of poultry compost fertilizer in order to decrease its wastages or runoff under excessive rainfalls conditions. The purple leaf disorder raises the alert for investigating this situation in future studies and finding ways to assess and address it.