- Vegetables: broccoli, tomatoes
- Crop Production: cover crops
- Education and Training: decision support system, extension, on-farm/ranch research, participatory research
- Soil Management: nutrient mineralization
Organic/sustainable vegetable farmers use a wide variety of nitrogen (N) fertilizers ranging from commercial products (made from animal and seed meals) to manures and composts. These organic N sources must undergo mineralization and nitrification through microbial processes to become plant available inorganic N, a process that will vary based on the fertilizer and local weather conditions. Thus, a tool that can estimate mineralized N will help organic farmers address better N management, aid in synchronizing plant available N release with plant uptake, reduce farmer costs and environmental degradation, and lead to increased sustainability in these systems. This project took a systems approach to determine N mineralization under laboratory and field conditions to create a web-based N calculator. A long-term incubation (100 days) determined net N mineralized from 49 different commercial fertilizers, poultry litters, and composts. Net N mineralized ranged from 21 to 87%, 8 to 37%, and 1 to 4% of the total N applied for the commercial fertilizers, poultry litters, and those composts that mineralized, respectively. A second long-term incubation study determined the effect of soil texture in four different soils common to the Southeast on N mineralization from organic materials. While high clay content decreased N mineralization from feather meal, such effect was not observed with a pelleted fertilizer product. Low pH decreased mineralization rates for both products. Field studies were conducted both at the University of Georgia Research Farm and at four participating farms to determine N mineralization from nine different fertilizers. These results culminated into a web-based nitrogen calculator which can help farmers predict and estimate N mineralization based on material selection, application rates, and environmental factors to meet plant demand. Results from this project were shared through presentations and publications to farmers, Extension, and the scientific community.
Overall objective: To determine N release from a wide range of organic materials and create an on-line tool to accurately model plant available nitrogen from the application of organic materials based on the material and local weather conditions. Educational goals include increasing awareness and knowledge about N availability from organic materials and fertilizers for small to mid-scale sustainable vegetable farmers, Extension agents, and the public. This work will address the need for more precise management of these materials, decreasing costs and labor for farmers while also decreasing the potential for environmental degradation due to the introduction of excess N into the surrounding ecosystems.
Objective 1. a) Determine potentially mineralizable N and rates of N mineralization for 49 organic materials (manures, composts, other organic fertilizers), and b) determine the effect of soil texture on N mineralization rates of organic materials.
Objective 2. Calibrate NIRS/VNIRS to estimate mineralizable N and rates of N mineralization for 49 organic materials.
Objective 3. Develop a web-based PAN calculator that allows producers to calculate PAN over the growing season as a function of local weather and soil conditions.
Objective 4. Collect PAN data from plots at the UGA farm and at cooperating farms, and use the data to calibrate and validate the PAN calculator.
Objective 5. Disseminate the N mineralization data, availability of the NIRS/VNIRS analysis for organic materials, and web-based PAN calculator to the public, farmers, and extension agents.