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An early season nitrogen test to help Ontario cereal growers decide whether or not to side-dress with nitrogen fertilizer

An early season nitrogen test to help Ontario cereal growers decide whether or not to side-dress with nitrogen fertilizer

Principal Investigator: Manish Raizada

Research Institution: University of Guelph

Timeline: March 2014 to April 2018


  • Evaluate whether biosensor bacteria called GlnLux can be used by a grower to decide whether or not (or how much) to side-dress with nitrogen.
  • Determine whether results from GlnLux can be used to make a decision on nitrogen side-dressing that optimizes corn yield and maximizes the cost:benefit ratio of nitrogen application (MERN).
  • Compare the GlnLux test to other available technologies (SPAD meter, Greenseeker, standard soil N tests), so that researchers and growers can make an informed decision as to which test to use.


  • The development of an accurate and affordable GlnLux nitrogen fertilizer diagnostic will help growers know how much nitrogen fertilizer to apply during the mid-season (side-dress stage) to make better nutrient management decisions on their farm, maximizing their return on investment while reducing their environmental impact.

Scientific Summary:

Nitrogen is one of the most essential nutrients (fertilizer) for crop production. Farmers strive to apply nitrogen in the most efficient way to satisfy cropping needs while being economically efficient. As a result of uncontrollable factors such as weather, nitrogen has the ability to be lost into the environment.  Some grain farmers in Ontario apply all of their crop’s nitrogen upfront in a single pass when the plant is in its early growth stages.  In order to improve nutrient use efficiency, farmers are beginning to apply nitrogen in multiple applications throughout the plant’s growth cycle.  However, affordable diagnostic tools are needed to improve farmers’ ability to split their nitrogen fertilizer application into multiple applications. This requires an accurate pre-plant equivalent of a soil test, and a nitrogen test for mature plants to help growers add the most economically and environmentally sustainable nitrogen rates at each plant stage. Current in season diagnostic tests using direct soil nitrogen testing include SPAD or Greenseeker®, which are reported to be ineffective during the early part of the growing season.

To assist Ontario corn growers, the researchers created an alternative approach to early season nitrogen testing which measures leaf concentrations of the amino acid glutamine, an excellent indicator of plant nitrogen status. They have created a rapid test for leaf glutamine based on a biosensor bacterium called GlnLux. In this test, a grower simply uses a paper punch to remove a small disc from a crop leaf. While the test was previously optimized under controlled greenhouse conditions, this grant was intended for the investigation of its usefulness under field conditions.


With respect to nitrogen fertilizer, Canadian farmers spend $40/acre on nitrogen fertilizer, whereas in the best years, their profit is $150/acre. Farmers often add extra nitrogen fertilizer as an insurance policy for high yields, but typically add the fertilizer early in the growing season when the seedings are small and incapable of absorbing it, up to 50% to be lost to the environment into watersheds or as potent greenhouse gases. However, if farmers add too little fertilizer, their crop yields can suffer. Current soil nitrogen diagnostic testing for nitrogen may offer guidance to farmers as to how much fertilizer to add. Current soil nitrogen diagnostic testing can cost $10/sample, and farmers need to test many samples across the field and at multiple timepoints for the test to be informative – and even then, soil testing is unreliable early in the season when farmers are making fertilization decisions. Therefore, a better test for soil nitrogen was clearly needed.

Rather than sampling the soil, the researchers decided to sample leaves and let the plant act as a reporter for nitrogen availability. They engineered a microbe (a biosensor) to sense a critical metabolite produced by corn after it absorbs soil nitrogen (the amino acid glutamine, Gln) and in response emit light; for the test, a leaf punch is removed, incubated with the biosensor (called GlnLux) and light is measured. Previously they had limited data about the effectiveness of the test from indoor-grown plants but needed more greenhouse data and especially field data. Here, using extensive greenhouse trials and three years of field trials with corn, they showed that the GlnLux test is an effective alternative to soil testing, costs only $1/sample and offers value early-mid season. Most exciting, the test was able to predict final grain yield, albeit with some limitations – meaning farmers may be able to use the test to decide how much fertilizer to add to maximize grain yield while balancing the cost of the fertilizer.

The GlnLux test has been issued a U.S. patent. The GlnLux test still needs improvement, but in 5-10 years may be incorporated with other measurements (e.g., soil type, cropping history, soil moisture) into an algorithm to help farmers decide how much fertilizer to add, and when to add it, to improve their profits and minimize damage to the environment – to make agriculture more sustainable and climate change friendly.

This project also trained a future leader in agriculture for Canada who was a finalist for the Governor-General’s Academic Gold Medal for the top PhD student from University of Guelph’s Ontario Agriculture College.

External Funding Partners:

International Plant Nutrition Institute (IPNI)

Natural Sciences and Engineering Research Council of Canada’s Collaborative Research and Development program (NSERC-CRD)

Ontario Agri-Business Association (OABA)

Ontario Trillium Scholarship from the Government of Ontario

Ontario Ministry of Food, Agriculture and Rural Affairs (OMAFRA)

Project Related Publications:

Goron, T.L. and Raizada, M.N. 2017. Biosensor-mediated in situ imaging defines the availability period of assimilatory glutamine in maize seedling leaves following nitrogen fertilization. Nitrogen: 1:2.

Goron, T.L., Nederend J., Stewart, G., Deen B., and Raizada, M.N. 2017. Mid-season leaf glutamine predicts end-season maize grain yield & nitrogen content in response to nitrogen fertilization under field conditions. Agronomy:7:41.

Goron, T.L. and Raizada, M.N. 2016. Biosensor-based spatial and developmental mapping of maize leaf glutamine at vein-level resolution in response to different nitrogen rates. BMC Plant Biology:16:230.

Goron, T.L. and Raizada, M.N. 2014. Current and Future Transgenic Whole-Cell Biosensors for Plant Macro- and Micro-nutrients. Critical Reviews in Plant Sciences:33: 392-413.