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Using two different technologies to measure sidedress nitrogen application rate in corn

Research Scholar

Lucas Paschoal, Department of Horticulture and Crop Science (Brazil)
Peter Thomison, Faculty Mentor
Alexander Lindsey, Co-Researcher


Lucas Paschoal was an undergraduate student in Agronomy at Sao Paulo State University (UNESP) – College of Agricultural Sciences (FCA) – Botucatu, Sao Paulo State, Brazil. Currently a Visiting Scholar at The Ohio State University (OSU) - Department of Horticulture and Crop Science doing an internship evaluating the performance of drought-tolerant corn hybrids and participating in the Stepping-up Soybean: Production, Profits, and Quality, advised by Professor Peter Thomison and Assistant Professor Professor Laura Lindsey.

What is the issue or problem addressed in your research?

Corn (Zea mays L.) is a very important crop for the world with uses ranging from animal feed to the high-tech manufacturing industry. Supplemental fertilizers are commonly applied to corn fields to meet the crop's demand, but can result in negative environmental and economic effects if incorrectly applied. Different technologies exist to measure leaf chlorophyll content (ex. SPAD meter, GreenIndex+ app), but comparisons of these instruments has not been conducted.

What methodology did you use in your research?

The objectives of this study were: (i) to evaluate the relationship between chlorophyll content and nitrogen level in two corn hybrids; and (ii) compare two existing technologies for measuring chlorophyll content. A field experiment was conducted in 2013 at the Western Agricultural Research Station (WARS) in South Charleston, OH and at the Northwestern Agricultural Research Station (NWARS) in Hoytville, OH. One drought-tolerant hybrid and one susceptible hybrid from Pioneer were planted in early May at common plant densitites (77,000 plants ha-1 at NWARS and 89,000 plants ha-1 at WARS). At the V4 stage, five N rates (0, 50, 100, 150, and 200 kg N ha-1) applied at sidedress (V4). The technologies were evaluated at the R3 stage on 4 plants plot-1.

What are the purpose/rationale and implications of your research?

Preliminary results indicate that both instruments (SPAD and GreenIndex+ App) showed that the amount of chlorophyll increases proportionally with the increase in nitrogen rate, but the increase is non-linear. However, a positive linear relationship was observed between the measurements from SPAD and the GreenIndex+ App. These results may indicate the GreenIndex+ App and SPAD meter will both accurately measure the applied N rate in corn at R3.