Estimation of Soil N Availability for Tomato Production in High Tunnel vs. Open Field under Organic and Conventional Management

View the project final report

• 2014 annual report

Commodities

• Vegetables: tomatoes

Practices

• Crop Production: organic fertilizers
• Education and Training: extension, workshop
• Production Systems: organic agriculture
• Soil Management: nutrient mineralization, organic matter, soil analysis, soil quality/health
• Sustainable Communities: sustainability measures

There are many challenges to predict the soil available nitrogen (N) for vegetable growers in a timely manner. Soil testing and yield are used routinely to guide agricultural applications of N. Under or over fertilization is apt to occur in any given growing season. Insufficient application of N can have serious economic consequences for the growers, whereas excessive fertilization increases the risk of environmental pollution. This is especially true for sustainable farmers using organic sources of nitrogen such as cover crops or compost. The objective of this study is to estimate the soil N availability for tomato production in high tunnel vs. field under organic and conventional system using the Illinois Soil Nitrogen Test (ISNT). The ISNT estimates the potentially mineralizable fraction of soil organic N, specifically it measures the amino sugar N. We also plan to explore the relationship between N mineralization from incubation as potentially mineralized nitrogen (PMN) and the ISNT. The results will be compared with the tomato yields under different fertility levels in a replicated field experiment that was conducted from 2007-2010. This approach has a major advantage over the other testing techniques and has value for improving N-fertilizer efficiency. We will develop fertility recommendations based on the results. If adopted, this would increase the profitability of tomato production and reduce the adverse environmental effects of excessive N and phosphorus P fertilization, especially for sustainable specialty crop producers using organic soil fertility amendments.

For the intermediate term, one of the greatest challenges organic and other growers using organic amendments face, especially during the beginning of organic management, is providing adequate fertility to meet crop need. Having more knowledge about N availability during the growing season will help growers estimate the amount ofN supplement required in the season. This would help to minimize the use of off-farm inputs and increase profitability by reducing the cost of additional fertilizer supplements, which in turn will reduce the amount of nitrate in
ground water, reduce the phosphorous loading to fresh water systems and decrease the cost of
production.
In the short term, this project will provide us with new information on N availability for tomato production in high tunnel vs. open field under organic vs. conventional systems based on the ISNT test compared to PMN incubation. The project results will be published in extension bulletins and in peer reviewed journals.