On-farm precision ag research update: In-season site-specific side-dress nitrogen rate recommendations for corn

By: Yuxin Miao, Associate Director of Precision Agriculture Center

Key points

• We use high spatial and temporal resolution PlanetScope satellite remote sensing images to monitor corn growth and make site-specific side-dress nitrogen (N) recommendations.
  
• Preliminary on-farm trial results from 2019 and 2020 indicate that this technology can significantly increase N use efficiency while producing similar corn yield compared with growers’ current practices.
  
• More on-farm trials are being conducted in 2021 to further evaluate this in-season, site-specific N management technology.

Why do precision nitrogen management research?

Precision nitrogen management (PNM) aims to match N fertilizer supply with crop N demand in both space and time. It has great potential to improve corn N use efficiency, increase growers’ profitability and protect the environment while maximizing crop yield. However, the current adoption rate of PNM is still very low in Minnesota, and most growers apply the majority of N fertilizer before planting. This may be due to the high cost and complexity of current PNM technologies, lack of technical support, and the weaknesses and limitations of some of the available PNM technologies, among other factors.

Supported by the Agricultural Fertilizer Research & Education Council (AFREC) and the USDA Natural Resource Conservation Service (NRCS), the University of Minnesota’s Precision Agriculture Center (PAC) is developing and evaluating cutting-edge PNM strategies and technologies for corn to facilitate the adoption of PNM in Minnesota.

What we did

We have been developing distinct levels of PNM strategies and technologies for corn, including site-specific calibration strip-based PNM, crop growth model-based PNM, remote sensing-based PNM, management zone-based PNM, machine-learning and remote sensing-based PNM, and more.

A recent major advance in this field is the development of remote sensing and calibration strip-based PNM technology for corn. This technology uses strips of different preplant N application rates and high spatial and temporal resolution PlanetScope satellite remote sensing to determine site-specific side-dress N application rates for around the V8 growth stage, as illustrated in the image below (Credit: Cadan Cummings).

This PNM technology is innovative and practical in several ways:

• It is based on site-, year-, and hybrid-specific calibration information, so it is more reliable.
  
• It uses PlanetScope remote sensing images with global coverage at around three meters resolution and daily revisit time, so it is more practical than proximal sensor-based strategies for wider applications.
  
• It is compatible with other satellite and unmanned aerial vehicle (UAV) remote sensing platforms.
  
• It can be implemented on any farmer’s field directly without the need for previous data accumulation.
  
• Farmers don’t need to purchase new equipment, such as new sensors, as long as they have or have access to variable rate applicators.

What we found

Based on three on-farm experiments conducted in 2019 and 2020, we found that the in-season site-specific N recommendation approach reduced N application rates and increased N use efficiency (partial factor productivity (PFP), corn produced per kg N). Yield impact varied from slightly higher, similar or slightly lower as compared with the farmer’s N rate (FNR) applied before planting, depending on different field and weather conditions. The strategies to apply 0% or 35% of total FNR as preplant N and then adjust side-dress N application using this technology performed better than the strategy to apply 70% FNR as preplant N and then adjust side-dress N rates using this technology.

What’s next?

We are conducting on-farm trials in 2021 to systematically evaluate the new PNM technology in comparison with farmers’ current practices, split application (35% FNR as preplant and 65% as side-dress fertilizer), and commercially available crop model-based N rate recommendations. We are also evaluating machine-learning and remote sensing-based PNM and management zone-based PNM.

We will conduct 60 on-farm trials across Minnesota and Indiana to further evaluate this technology in 2021-2023 in terms of corn yield, N use efficiency, N losses and profitability. A decision-tool will be developed and an on-farm Precision Ag. Trial Network will be established to facilitate the adoption of this technology by crop consultants and corn growers. Corn growers interested in conducting on-farm trials to evaluate this technology should read this blog post.

Acknowledgements

We appreciate the funding for this study from Agricultural Fertilizer Research and Education Council (AFREC) and USDA Natural Resource Conservation Service (NRCS) Conservation Innovation Grant. Cadan Cummings was the graduate student working on this project in 2019-2020.

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Support for Minnesota Crop News nutrient management blog posts is provided in part by the Agricultural Fertilizer Research & Education Council (AFREC).