An active sensor algorithm for corn nitrogen recommendations based on a chlorophyll meter algorithm

Fernando Solari, John F. Shanahan, Richard B. Ferguson, Viacheslav I. Adamchuk

Research output: Contribution to journalArticlepeer-review

48 Scopus citations


In previous research we found active canopy sensor reflectance assessments of corn (Zea mays L.) N status have potential for directing in-season N applications, but emphasized an algorithm was needed to translate sensor readings into appropriate N application (Napp) rates. The objectives of this work were to: (i) develop an active canopy sensor algorithm based on a SPAD chlorophyll meter algorithm and (ii) validate the active canopy sensor algorithm using data collected from a companion study. We derived the sensor algorithm using a linear relationship between sensor sufficiency index (SIsensor) and SISPAD values established in the previous research and a published SPAD algorithm employing a quadratic equation to calculate Napp as a function of SISPAD. The resulting equation: Napp=317 v0.97 SIsensor represents the function for translating SIsensor to Napp. To validate the algorithm, SIsensor values collected from small plots receiving varying N amounts were converted into Napp using the algorithm. Then Napp was converted into crop N balance (Nbalance) estimates, where Nbalance = applied N-Napp. Negative Nbalance values indicate N deficiency while positive values indicate excess N. The Nbalance values were compared with relative yields and a quadratic-plateau model fit to the data set for both growth stages (V11 and V15), producing an R2 of 0.66. Relative yields plateaued at an Nbalance near zero (-11 kg N ha-1), indicating the algorithm provided reasonable estimates of Napp for maximizing yields. The equation provides a basis for the use of active crop canopy sensors for in-season N management of irrigated corn.

Original languageEnglish (US)
Pages (from-to)1090-1098
Number of pages9
JournalAgronomy Journal
Issue number4
StatePublished - Jul 2010

ASJC Scopus subject areas

  • Agronomy and Crop Science


Dive into the research topics of 'An active sensor algorithm for corn nitrogen recommendations based on a chlorophyll meter algorithm'. Together they form a unique fingerprint.

Cite this