Using Unoccupied Aerial Vehicles for Application of Fertilizers to Cranberry Bogs in Massachusetts

Progress report for LNE22-458R

Project Type: Research Only
Funds awarded in 2022: $69,724.00
Projected End Date: 03/31/2025
Grant Recipient: USDA-ARS
Region: Northeast
State: Massachusetts
Project Leader:
Brian Wick
Cape Cod Cranberry Growers Association
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Project Information


About a third of the US cranberry supply is produced on 5000 ha of farmland in southeastern Massachusetts, where the cranberry industry is an undeniable part of the economy, landscape, and cultural heritage. For cranberry farming to be a profitable enterprise, growers must balance the demands of crop production with environmental sustainability, uncertainties of a changing climate with regulatory pressures restricting water use, and a surplus of fruit with increasing production costs. To remain viable, Massachusetts cranberry growers are eager for new tools that increase effciency while reducing environmental impacts of cranberry production. However, a paucity of information exist on the efficiency and uniformity of  fertilizer additions to cranberry farms.  Currently, three methods are used to apply fertilizers to cranberry agriculture: aerial applications by human-piloted helicopters, ground applications by ground-rigs, and ground applications by backpack-type broadcast spreaders. Further, the use of unoccupied aerial vehicles (UAVs) is increasingly being incorporated into precision agriculture management activities, and which has the potential to improve precision and uniformity of fertilizer applications compared to helicopters. In the proposed research, we will conduct a 2-yr study to answer the following questions: 1) What are the optimal settings for UAV-based granular fertilizer application on cranberry farms, and 2) How does fertilizer application via UAV compare to backpack spreaders, ground rigs, and helicopters in terms of application uniformity, cost, and time? We will purchase a state-of-art multirotor UAV capable of applying granular fertilizers with a payload capacity of 29 lb, and carry out several field campaigns to compare the uniformity and efficiency of fertilizers applications with UAVs, helicopters, ground-rigs, and backpack spreaders. Growers in southeastern Massachusetts will benefit from technological advancements the enhance the sustainable production of cranberries. 

Project Objective:

We will carry out a proof-of-concept study to demonstrate the use of UAVs for application of fertilizers to cranberry bogs. Specifically, we will (1) determine the optimal altitude, flight speed, and spreader settings for UAV-based fertilizer applications, and (2) evaluate the efficiency and uniformity of fertilizers applied by helicopters, ground rigs, backpack-type broadcast spreaders, and UAVs. Use of UAVs for fertilizer applications has not been tested on cranberry bogs, yet growers are eager for alternatives to current practices that generally lack precision. Use of UAVs represents an opportunity to conserve resources, enhance water quality, and increase agricultural productivity in Massachusetts.


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Materials and methods:


Work on this study began in the growing season of 2022. In July, we carried out a pilot study to test a sampling strategy for measuring the spatial variability of granular fertilizer applied to commercial cranberry beds. We developed a 12-m hexagonal grid sampling strategy to reduce spatial bias in sampling and allow for roughly 50 – 100 samples for a typical cranberry bed in southern Massachusetts. This methodology was tested during a helicopter-based application, as well as a hand-crank application at two different cranberry beds, using plastic buckets to collect granules. The results of the pilot study showed this sampling strategy can be used effectively to compare differences between application methods, as well as identify spatial patterns across the entire study beds. This methodology represents a significant improvement and expansion of our initially proposed sampling design, increasing our analysis to the scale of entire cranberry beds, while reducing spatial bias in measurements.

Agronomic technicians at the University of Massachusetts Cranberry Station and a local cranberry grower participated in the 2022 pilot study to test the field fertilizer sampling strategy. We have also reached out to a local grower who may be applying fertilizer via UAV in the 2023 growing season and they have expressed interest in participating in the study.

The sampling strategy established in 2022 will be used to measure the spatial variability of application rates on cranberry beds fertilized via UAV, helicopter and hand-crank during the 2023 growing season. Unlike the pilot study, we will use shallow trays equipped with internal baffles to prevent granules bouncing out during collecting. The trays are used in the industry to calibrate disc spreaders used to apply fertilizer granules and may improve any bias introduced to sampling based on the height of the bucket mouths relative to the cranberry bed surface, particularly for hand-crank applications.

We are in the process of procuring a UAV and obtaining the necessary licenses/permits needed to carry out fertilizer applications in this study and plan to conduct the first flights in the spring of 2023.


In 2023 we purchased 120 0.5-m x 0.5-m disc spreader calibration trays to sample granular fertilizer applied to study beds. These trays were used instead of buckets during all 2023 sampling events and a 14-m hex grid sampling design was used, with an 8-m buffer around each study bed. Sampling was carried out at three beds during hand-crank application and three beds during helicopter applications. Prior to all sampling events, multispectral image data were collected using automated unoccupied aerial vehicle (UAV) surveys with a MicaSense RedEdge MX camera and aboveground plant biomass was harvested from a subset of sampling locations within each grid and analyzed for chlorophyll content, carbon and nitrogen content, and stable isotopes of carbon and nitrogen. Fertilizer samples were collected from each tray within hours of applications. Follow-up UAV flights and plant sampling at the same subset of points at each site were carried post-application, prior to any subsequent applications, to determine if there was any spatial variation in plant response to that of fertilizer being applied.

A fertilizer application UAV was successfully purchased to carry out applications during the 2024 growing season. Fertilizer UAV training is tentatively scheduled for late spring/early summer, with application occurring in July.

We presented the an updated to this research to over 150 people in the local cranberry industry at the annual winter growers meeting held by the University of Massachusetts Cranberry Station in January of 2024.

Participation Summary
3 Farmers participating in research

Education & Outreach Activities and Participation Summary

Educational activities:

1 Webinars / talks / presentations

Participation Summary:

125 Farmers participated
25 Number of agricultural educator or service providers reached through education and outreach activities
Outreach description:

We presented the results of the pilot study findings to over 150 people in local cranberry industry/research community at the annual winter growers meeting held by the University of Massachusetts Cranberry Station in January of 2023.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.