A recent Canadian demonstration project measuring whether variable-rate (VR) fertilizer application techniques can be adapted to manure application showed producers were impressed with the concept, but found current manure application technology fell short of the challenge.

The potential agronomic/economic benefit would be increased yields in more productive areas of the field by applying more nutrients to these areas and, therefore, decreasing the environmental risk of nutrient leaching to bodies of water.

Optimizing Application Rates

The Manitoba Rural Adaptation Council (MRAC), the Manitoba Pork Council and producer participants funded the $54,750 study, which was carried out by Agra-Gold Consulting and Farmer’s Edge Precision Consulting.

Thirteen producers provided about two sections of land, a sampling base which represented a cross-section of cropping conditions in the Canadian province.

In the study, manure was applied using the drag hose application method. Application rates were varied based on global position satellite field maps indicating different nutrient requirements for different parts of the fields. Satellite imagery identified zones using different light bands to create a vegetative index of better growing parts of the field. The zones were then individually soil tested to determine the reasons for the variability across zones and establish the optimal nutrient application rate.

Project leader Scott Dick with Agra-Gold Consulting, Ltd. says an increasing number of producers are adopting VR application with commercial fertilizer to tailor application rates to the varying nutrient requirements on different sections of a field. That technique can produce better nutrient utilization by the crop, higher yields, lower costs and reduced environmental risk of excess nutrients contaminating water supplies.

While adapting variable-rate techniques to manure application would seem to have good potential, there still needs to be some refinement in the application of the technology, he says.

“Producers accepted the methodology used in creating the different management zones, but they weren’t ready to embrace this precision approach yet,” Dick reports.

He found that there are three reasons for that conclusion:

  • “The commercial drag hose equipment used to apply manure just couldn’t accurately and efficiently vary application rates to match specific nutrient needs,” he notes.
  • Equipment operators were limited in adjusting application rates to speeding up or slowing down the tractor speed. “On a half-mile run, that could mean between one and three speed adjustments – not a major problem – but enough to affect accuracy,” Dick says. Plus, without an “on-the-go” sensor to determine soil nutrient levels, planners had to rely on previous soil analyses to set application rates. “The only way to accurately measure nutrient levels was to send a sample to the lab after application,” he says.
  • Finally, unlike commercial fertilizer applications, where nitrogen (N) and phosphorus (P) can be applied independently to correct soil shortages, the nitrogen and phosphorus content in hog manure is fixed. So individual N and P application rates can’t be adjusted on the go.

Precision has Potential

Even though the study indicates variable rate manure application isn’t commercially feasible at the present time, information gathered outlines ways producers can use precision farming techniques to increase yields and reduce environmental risks.

For instance, producers can begin by applying a base rate of manure using conventional techniques, then follow up with a variable-rate application of commercial starter fertilizer at seeding time. That scenario allows them time to get accurate manure and soil analyses results back from the lab to provide an accurate match of nutrient applications with crop requirements.

More Information

A complete report on the Manitoba project, “Applying Manure to Defined Management Zones Using Precision Farming Techniques,” is available on the Manitoba Livestock Manure Management Initiative (MLMMI) Web site at www.manure.mb.ca under completed projects.

For more information on the Manure Initiative or its projects, please visit www.manure.mb.ca or contact Brandy Street, executive director, by phone at (204) 945-2122 or by e-mail at Brandy.Street@gov.mb.ca.

Manure Initiative research funds are provided by the governments of Canada and Manitoba through Growing Forward, a Federal-Provincial-Territorial Initiative. Base funding for the Manure Initiative’s research program is provided by the Manitoba Pork Council.

Scott Dick has offices in Niverville, Manitoba and can be reached at Scott1@mts.net.