Adopting pre-sidedress nitrogen testing to minimize nitrate application in sweet corn and pumpkins

View the project final report

Commodities

• Vegetables: sweet corn

Practices

• Crop Production: nutrient cycling, application rate management, tissue analysis
• Education and Training: demonstration, extension, farmer to farmer, on-farm/ranch research, participatory research
• Production Systems: general crop production
• Soil Management: organic matter, soil analysis, nutrient mineralization

Pre-sidedress nitrogen testing (PSNT) has the potential to significantly reduce the amount of nitrogen fertilizer applied to vegetable crops in Maine. Such reductions could minimize the environmental risks of excess nitrogen runoff and leaching into ground and surface waters, while reducing inputs into crop production, thus improving profitability. However, PSNT technology for vegetable crops is relatively new and its adoption has been minimal, at best. Vegetable farmers have had limited exposure to this technology, and there is no testimonial support for it among them. Vegetables are high value crops, with markets that demand consistent high quality, so growers are reluctant to adopt new practices that may appear to put quality or quantity at risk. We propose to test and demonstrate the benefits of pre-sidedress nitrogen testing on sweet corn and pumpkins, two important, high-nitrogen input crops in Maine. Twelve “early-adopter” farms will test the adaptability of PSNT in comparison to traditional nitrogen management, and use the information and experience to consul fellow vegetable growers. Their experience will also be used to promote PSNT through grower newsletters and meetings. Having a respected group of farmers working with Cooperative Extension to transfer PSNT technology to farmers will significantly increase the adoption of this technique, and reduce future nitrogen inputs for vegetable crop production in Maine.

Pre-sidedress nitrogen testing (PSNT) has been available for silage corn for several years and, more recently, procedures have been developed for certain vegetable crops, including sweet corn and pumpkin. These soil tests are used at critical points during the growing season to determine if nitrogen levels in the soil are adequate for optimum plant growth through the harvest stage. If the test shows adequate soil nitrogen, then no sidedress need be applied, potentially saving excessive nitrogen loading, energy and labor costs. Nitrogen applications can be reduced by 25% to 50% through the use of PSNT in place of conventional application rates and timing. This has the potential to reduce applications of nitrogen in Maine by as much as 1,000,000 pounds.

Despite the availability of these tests, adoption of this technology by vegetable growers has been very low in Maine. Technology transfer regarding PSNT’s has been aimed primarily at silage corn growers. Vegetable growers have not had adequate access to this technology, and feel a high level of risk trying it on their fields because of the higher value of their crops and the need to maintain very high quality for their markets. Additionally, most farmers feel the window for optimum timing of sidedressing is very small, and that waiting more than two days for test results during this time could significantly reduce the quality of their crop.

Bringing pre-sidedress nitrogen testing to Maine growers through demonstrations of the technique at a series of “early adopter” farms throughout the state could substantially increase the use of this method among Maine vegetable growers. The University of Maine Cooperative Extension presently offers a sweet corn integrated pest management (IPM) program to growers across the state, monitoring over twenty farms and sharing insect population data with over 200 farmers in northern New England to assure that pesticide use is kept to the minimum necessary to produce a high quality crop. This program has been credited with bringing nearly 100% of Maine sweet corn growers to adopt IPM practices on their farms. A similar approach for pre-sidedress nitrogen testing could be very effective in increasing its adoption. The Maine Vegetable & Small Fruit Growers Association represents more than half of the active commercial retail vegetable growers in the state, and its Board of Directors has actively sought to develop and cooperate in a program designed to test PSNTs on a statewide scale.