High Level Spray Irrigation of Manure in Ontario

A summary of manure spills data from 1988 to 1998 shows that:

• 40% of the spills are spray irrigation related

• 16% are related to insufficient manure storage

• 11% tanker related

• 14% equipment failure

• 8% transportation related

When details of these spills are examined, most are the result of mismanagement. Most of these spills could have been avoided had certain BMPs been implemented. It is also interesting to note the high number of manure spills (approximately 60%) that entered a stream via underground field tile versus overland runoff.

As a result of this data, the sub-committee has decided to make a recommendation to the WQWG regarding the practice of high level spray irrigation of liquid manure. The following paper outlines the problem, options and recommendation for a course of action as preferred by the members of the P3 sub-committee.

CONCERN

Contamination of the province’s rural watercourses has been well documented over the past 15 years. Although there is ongoing debate as to the specific sources of contaminants such as bacteria, nutrient loadings from agricultural sources are usually tied to either soil erosion, faulty septic systems or the by-products of livestock operations. These sources are all a concern and have been addressed through various education programs and BMP promotional initiatives.

All of these ‘diffuse sources’ (point and non - point) have an impact on stream health, however a manure spill has an immediate impact. The impact is sudden, and often catastrophic for local aquatic life and habitat. The implications for water users downstream can also be significant. Clean up is often difficult.

Although some manure spills are accidental, most can be avoided with better nutrient management planning, improved training and education, and a sound spills contingency plan.

PROBLEM

The data indicates that spray irrigation of liquid manure results in 2 to 3 times more manure spills than the next closest cause. Use of the technology may also be associated with a number of other issues. They include:

• uneven application

• lack of equipment supervision

• timing

• nutrient utilization

• wind drift and soiling

• odour

• negative visual impact

Uneven Application

The ability to apply liquid manure onto cropland at an even rate is not easy. Recent studies have shown that spreading techniques apply manure at rates that vary from 2000 gal/acre to 20,000 gal/acre within the same field. Researchers and industry are working together to develop better equipment to solve this problem. High level irrigation guns can apply manure evenly if they are used under proper conditions. However, rates are easily affected by wind deflecting the stream of manure to one side of the application pattern area. When this happens, the soil is not always capable of absorbing the increased amount of manure. Overland runoff or leaching through soil macropores may carry the manure from the field to an eventual outlet. A ‘Nutrient Management Plan’ will be difficult to follow if the rate of manure is unevenly applied to the field.

Supervision

The man-power to operate high level irrigation equipment is at issue. The records from the Spills Action Centre and conversations with Ministry of the Environment abatement officers, indicate that spills associated with the technology could have been avoided if the operation had been supervised more closely. Too often the equipment is left unsupervised once it is set up and operating. If equipment malfunctions, the problem is often not discovered in time to prevent a spill of manure. Burst pipelines, stuck nozzles or improper spray pattern are examples of manure spills associated with the technology, that in many cases could have been prevented or minimized with proper supervision.

Timing

Spring application of manure should wait until the soil is dry enough to accept the manure without damage being done to the soil from compaction. A perceived advantage of high level irrigation as a method of manure application is that you are not running over the field with equipment at a time when the soil is easily compacted. The irrigation gun minimizes risk of compaction. The equipment is therefore often used earlier in the season before the soil is dry. Macro pores are usually running and may provide a direct pathway to carry excess manure to underground field tile. The risk of overland runoff is also higher because the ability of the soil to absorb the manure is often lower. If the equipment were used at a time when soil were drier and when the crop could best utilize the nutrients, these problems would be greatly reduced.

Nutrient

Loss Loss of nutrients through macro pore movement and volatilization is an issue farmers should be concerned about. Statistics are not available to quantify the amount of nitrogen loss from manure applied with different methods, however, spray irrigation likely contributes to a significant amount of the total. Keeping the nutrients on the field where they can be utilized by the crop will save money.

Wind Drift

Atmospheric conditions must be right in order to control liquid manure once it has left the nozzle of the irrigation gun. Winds create a large problem for operators of high level irrigation systems. Manure through the gun often does not stay confined to field or property boundaries. Winds can effectively carry liquid manure mist a long distance. The soiling of neighbouring properties or passing vehicles is also a nuisance.

Odour

Odour has become a huge issue in general. Although odour from manure application is a fact of life, high level irrigation guns can worsen the situation. Odour from manure sprayed high into the air appears to travel much farther than odour from manure applied at low levels or directly onto or into the soil surface.

Visual

A final issue that has been raised though the committee, is the negative visual impact of the high level application of liquid manure. With the current pollution issues from agriculture industry so high in profile, we do not need to intensify the situation by encouraging the use of high level application. It is highly visible, and does not look like a normal farming practice to the unknowing person. It looks bad.

The combination of these issues has created a negative image of the use of high level irrigation as a method to apply liquid manure. It is important to note that the technology is used to apply other substances such as bio-solids, vegetable wash water and irrigation water. The committee is not addressing these other uses for the technology at this time.