Nick Andrews
Senior Instructor I, Small Farms Extension Agent

Metro Area Small Farms Extension Agent serving Multnomah, Washington and Clackamas Counties, specializing in Horticulture with a focus on vegetable production and organic methods.  

North Willamette Research and Extension Center
Department of Horticulture
(503) 678-1264


  • Organic Fertilizer Calculator
  • Cover Crop Calculator and Adaptive Cover Cropping Systems
  • Agricultural Composting
  • Growing Farms: Beginning Farmer Training Program
  • North Willamette Horticulture Society Organic Session

Cover Crop Calculator and Adaptive Cover Cropping Systems

Nitrogen contributions from cover crops are highly variable. The scientific basis for making estimating plant available nitrogen (PAN) is well established, but currently there is no research-based tool readily available to growers. We are expanding the Organic Fertilizer Calculator to cover crops. With funding from Western Region Sustainable Agriculture Research and Education (WSARE), we have determined the most efficient and accurate method for estimating cover crop total N. Additional funding from a USDA Special Grant supports laboratory studies for the development of a mineralization model for cover crops. The revised mineralization model is being validated with on-farm cover crop trials in commercial vegetable rotations. We expect to launch the cover crop calculator in early 2010 at Based on experience with the Organic Fertilizer Calculator, we estimate first year savings for Oregon growers to exceed $125,000. Increased utilization of cover crops will also improve soil and water quality.

A new WSARE grant will fund on-farm studies into the medium term (1-3 years) impacts of cover cropping on soil structure and nitrogen mineralization in commercial vegetable rotations. Treatments include common vetch alone, common vetch and cereal rye, common vetch and phacelia, and weedy fallow. Treatments will be in the same locations for the duration of the trials.

Agricultural Composting

In 2009, Andrews and Sullivan installed the first agricultural compost research and education facility in Oregon with funding from the Agricultural Research Foundation. The facility is housed at the North Willamette Research & Extension Center in Aurora. The purpose of the facility is to conduct research into the development of custom compost recipes for specific crops and to conduct agricultural composting workshops.

With funding from the USDA Integrated Organic Program, Sullivan and Costello are researching the production of custom compost for blueberries. The goal is to develop compost with high fertility, low pH and low salt content. The custom compost will be tested against commercially available composts in blueberry growth studies.

The Department of Environmental Quality is implementing new rules for composting facilities in 2009. Andrews served on the Rule Making Work Group from 2004-2009. The new rules will increase regulations for many agricultural composters, but will improve their access to non-agricultural feedstock. A new agricultural composting workshop is under development and is planned for early 2010. Andrews is seeking funding from SARE and is collaborating with the Clackamas Soil and Water Conservation Service. Workshop resources will be made available at




Outreach and Extension

The Organic Fertilizer Calculator was released in 2007. It is an online Excel spreadsheet that helps farmers plan organic fertilizer programs. The Calculator incorporates a nitrogen mineralization model developed by Dan Sullivan, OSU Soil Scientist. Users enter the guaranteed analysis of their fertilizers, their fertilizer recommendation and the cost of their fertilizers. First year plant-available nitrogen (PAN) is estimated by the mineralization model. Cost comparisons for available nitrogen and other nutrients are generated and growers can enter various application rates to determine the most cost effective fertilizer program that meets soil and crop nutrient requirements. As of January 2009 the Calculator has been downloaded more than 3,000 times and has over 800 registered users. Economic impacts are estimated to exceed $600,000 per year based on the registration survey. Improved nutrient management also improves soil fertility and water quality.