Active-optical reflectance sensors (AORS) use light reflectance characteristics from a crop canopy as an indicator of the plant’s N health. However, studies have shown AORS algorithms used in conjunction with measured reflectance characteristics for corn (Zea mays L.) N fertilizer rate recommendations are not consistently accurate. Our objective was to determine if soil and weather information could be utilized with an AORS algorithm developed at the University of Missouri (ALGMU) to improve in-season (~V9 corn development stage) N fertilizer recommendations. Nitrogen response trials were conducted across eight states over three growing seasons, totaling 49 sites with soils ranging in productivity. Nitrogen fertilizer rates according to the ALGMU were compared to economic optimal nitrogen rate (EONR). Without soil and weather information included, the root mean square error (RMSE) of the difference between ALGMU and EONR (MUDIFF) was 81 and 74 kg N ha–1 for treatments receiving 0 and 45 kg N ha–1 applied at planting, respectively. When ALGMU was adjusted using weather (sea-sonal precipitation and distribution prior to sidedress) and soil clay content, the RMSE was reduced by 24 to 26 kg N ha–1. Without adjustment, 20 and 29% of sites were within 34 kg N ha–1 of EONR with 0 and 45 kg N ha–1 at planting, respectively. But with adjustment for soil and weather data, 45 and 51% of sites were within 34 kg N ha–1 of EONR. These results show that weather and soil information could be used to improve ALGMU N recommendation performance.
Bibliographical noteFunding Information:
This project was funded and made possible by DuPont Pioneer. We thank producer cooperators for allowing us access to their farms. The authors would also like to thank all supporting scientists and field technicians involved in the collection and analysis of this dataset (Matt Yost, Kristen Veum, and Matt Volkmann [MO]; Dan Barker [IA]; Lakesh Sharma, Amitava Chatterjee, and Norm Cattanach [ND]; Todd Andraski [WI]; Tim Hart [DuPont Pioneer]; Jason Niekamp and Joshua Vonk [IL]; Glen Slater [NE]; Andrew Scobbie, Thor Sellie, Nicholas Severson, Darby Martin, and Erik Joerres [MN]), and the cooperating farmers and research farm personnel.
© 2018 by the American Society of Agronomy.