Lab and Field Nitrate Testing of Feed Crops

The objective of this project is development of simple, enzyme-based nitrate test kits for on-site feed and crop analysis. Many plant species accumulate nitrate, especially in times of stress such as drought. Nitrate levels can be high enough to pose a toxicity risk to livestock: consumption of excess nitrate can suppress rate of growth, low birth weight or stillbirths, reduced milk production, and even death especially in ruminants. Silage from high-nitrate crops can give off dangerous amounts of highly toxic NOx gases as they ferment. Farmers and crop consultants need a reliable and easy way to determine whether and when to harvest hays, grasses, and maize for feed. The Phase I project was designed to determine whether our nitrate test method and kits can become useful tools for agricultural extension personnel, food and feed chemists, crop consultants, researchers, farmers, and others. The proof-of-concept stage demonstrated that nitrate determinations based on enzymatic nitrate reduction by corn seedling nitrate reductase (NaR) can yield reliable data on nitrate content for feed and crop plants. Our results, and those of our collaboration partners, have demonstrated the feasibility of the method. The major objectives of the entire Phase I/Phase II project are: 1. To show that NaR-based nitrate analysis provides quantitative, reliable data in the lab using standard extraction techniques. 2. To develop a simplified test kit, similar in format to our Consumer NTK, that farmers and others can use on site. 3. To develop and validate quick and facile sample preparation techniques that provide extracts ready for analysis in the simplified test kits. 4. To validate that the method can provide data of sufficient reliability for making harvest and safety decisions on-site, in the field. An additional objective in Phase II will be the evaluation of recombinant NaR forms under development at NECi for use in these test kits. The advantage of recombinant NaR is the potential for lowering enzyme cost. Less expensive enzyme means we can use more NaR per assay, making the assay faster. Time is always a concern, for farmers, consultants and researchers alike. There is real need for improved methods for nitrate determination in the field. A dominant field nitrate assay used today is based on a color reaction of a diphenylamine/sulfuric acid mixture placed in a cavity bored into the corn stalk. This method lacks accuracy, and exposes the user to concentrated sulfuric acid. We believe the test kits under development in this project will provide data of stronger reliability, with dramatically reduced usage of hazardous materials for improved worker safety. A Field nitrate test kit capable of providing reliable nitrate information on-site will save time and money for farmers and consultants at harvest. A fast, safe and reliable nitrate test kit can help improve feed safety for livestock. As a collateral benefit, fast and simple test kits may be used for on-site soil testing, as an aid in avoiding application of excess nitrogenous fertilizers. Such kits may become useful tools for development of nutrient management plans.