WSARE 2000 Farmer/Rancher Grants-FW00-032

TITLE: Organic soil amendment release rates for fertility in apples

Do you know when the best time to fertilize your fruit trees is? Steven Ela, a transitional organic tree fruit grower in Delta County, Colorado, is determined to find out. Although much of the apple acreage in Delta County is organic or transitional organic, growers who want to use organic fertilizer on their orchards run into difficulty because little is known about the release rates of organic fertilizer in fruit systems. Therefore, growers have a difficult time knowing when to apply their manure for optimum impact. With the help of a Western SARE Farmer/Rancher Grant, Ela will conduct an experiment to determine the best time to apply organic fertilizers to apple trees.

Fruit grower Steven Ela is conducting an experiment to determine the best time to apply organic fertilizers to apple trees

Ela, along with two other Delta County growers and two technical advisors, has created an experiment that will study when nutrients become available from applied manures and how long they remain available. The experiment will be conducted on two sites: a transitional organic Gala orchard and a certified organic Gala orchard. Using these two sites will allow for comparison between how nutrients react in a system that has been organic for several years and one that is converting to organic.

Each site will have five different manure treatments. Information about nutrient release will be gathered primarily from soil samples taken for complete nutrient analysis before the application of manure, during the middle of the five-month period, and at the end of the five-month period, and from ammonium and nitrate samples taken biweekly over the five- month period. Leaf samples will also be taken for nutrient analysis. The purpose of these samples is to see what nutrients are being released from the fertilizers and when.

The project team hopes that knowledge of nutrient release rates in organic fertilizers will enable fruit growers to maximize fertilizer impact on tree vigor and tree quality, minimize losses such as leaching, and save money.