MSU Extension Fruit & Nuts

Livestock manure applied in bearing orchards that is not properly composted may contain harmful pathogens that pose a risk of food-borne illness. Fruit can become contaminated with manure in many ways: from containers placed on manured ground, by picker’s hands from ladder rungs, by windblown dust from manure application or storage, from dropped fruit and other means.

Growers are advised to check with their buyers to determine if livestock manure can be used in bearing orchards and still meet the buyer’s specifications. Some buyers require certified food safety farm audits that do not allow manure applications. Buyers that accept the USDA Good Agricultural Practices (GAP) farm audit, specify raw or un-composted manure should be incorporated into the soil and not applied within 120 days of harvest.

When livestock manure application is allowed by the buyer and the grower wishes to use manure, fall application immediately after harvest and before the ground freezes is suggested. Orchard applications should be made when soils are still warm, not saturated with water and with an actively growing orchard cover crop.

Orchards that are located on sandy soils are discouraged from receiving fall manure application due to the risk of nitrate leaching to the groundwater. Orchards located on sloped sites (greater than 6% slope) must be managed to prevent the runoff of manure to ditches and other bodies of water. Vegetated buffers and a minimum 150 feet setback from surface waters are most effective.

Fruit growers who decide to use livestock manure on bearing orchards should follow additional management practices (listed below) to prevent the loss of manure to both surface and groundwater.

It may be wise to restrict manure applications to non-bearing orchards or new areas to be planted to an orchard. Take special precautions to prevent manure loss to nearby bearing orchards.

Summary tips:

• Determine if fruit buyer or market will allow manure applications.
• Analyze manures to determine accurate nutrient levels and application rates.
• Do not exceed nutrient application rates recommended by MSU.
• Avoid manure applications where soil P levels are high (greater than 75 ppm P Bray P1 test).
• Prevent manure losses to surface and ground water.

Bearing fruit orchards

Nutrients used in fruit tree and crop production can come from manufactured fertilizers and/or naturally occurring sources such as livestock manures and legume crops. All nutrients, whether synthetic or naturally occurring, can be lost from the orchard system by natural processes such as runoff to surface water, or leaching to groundwater. Managers must minimize nutrient losses to maximize economic production and to protect water resources from contamination.

Livestock manures vary considerably in their nutrient content, depending on their source and handling. The nutrient content of manure needs to be known to calculate appropriate application rates. Nutrient concentrations commonly found in manures are provided in Extension Bulletin E- 852, Fertilizing Fruit Crops ($2.00 - available from the MSU Extension Bookstore), but specific manures should be analyzed to determine accurate nutrient levels and application rates.

Request manure nutrient content from your supplier, or have the manure analyzed by a reliable laboratory prior to application. A listing of manure testing laboratory is available at: http://web2.canr.msu.edu/manure/labsites.cfm

Caution: Fresh manure or manures that are not composted are high in nutrients and can injure tree roots if applied at excessive rates.

Nitrogen (N)

Although optimum N rates for bearing orchards vary considerably from site to site, use rates of 50 pounds N per acres for in the tree row applications and 100 pounds N (broadcast) of N as an initial guide. Be conservative with N rates until you are familiar with the planting. It is much easier to apply additional N than to manage excessive vigor caused by too high rates. Excessive vigor is particularly damaging in new, high-density apple plantings.

Under Michigan conditions, spring and fall applications have been equally effective. Spring applications are suggested on sandy soils because fall applications may result in nitrogen leaching and potential groundwater contamination.

Spring application of manure should be made more than 120 days before harvest, and when soils are warm, not saturated with water and preferably with an actively growing orchard cover crop.

Manure contains ammonium N and organic N. Generally, all of the ammonium N and 25 to 50 percent of the organic N is available to plants during the year of application. Manure analysis reports usually include total N, available N, P205 and K2O.

Manure must be applied so that rates of available N do not exceed those recommended by Michigan State University, to be in conformance with Michigan Right-to-Farm guidelines. In orchards with high testing phosphorus levels (where soils contain greater than 75 ppm P Bray P1 test), manure rates should not supply more P than is typically removed by the crop (about 50 lbs P205 per acre for a bearing orchard).

Manure should not be applied in orchards where soil P levels are very high (greater than 150 ppm P Bray P1 test), to be in conformance with Right to Farm guidelines.

Table 1. Manure application rates to provide a total of 50 pounds of N per acre.

Three factors that have the greatest effect on N requirements are soil type, orchard floor management and pruning. Orchards on fertile loam soils may require N at only half the recommended rates, whereas those on very sandy soils may require 50 percent more N. Sites previously used for alfalfa may contain high soil N levels and require much less fertilizer. Heavily sodded orchards may require 20 to 50 percent more N than clean cultivated plantings. Similarly, orchards heavily infested with weeds may require higher rates.

Heavy pruning stimulates vegetative growth and can reduce or replace N requirements. Heavily pruned trees should be fertilized lightly if at all.

Phosphorus (P)

Do not apply phosphorus (P) containing materials (manure or commercial fertilizer) unless soil or tissue tests indicate a need exists. Phosphorus is best applied at the time of orchard establishment by incorporating P into the orchard soil. Always prevent soil erosion to bodies of water, as water and wind erosion are the primary transport mechanism for P. Phosphorus enriched waters result in excessive algal growth, decreased water quality and harm to aquatic life.

If soil or tissue test indicate a need for P, apply 200 to 400 lb of P2O5/acre. Because P moves very slowly in soil, these rates will sustain most fruit crops for many years.

If the Bray P1 soil test level for P reaches 75 ppm, manure applications should be managed at an horticultural rate where manure P added does not exceed the P removed by the harvested crop (50 lbs of P2O5/A for a bearing orchard). If the Bray P1 soil test reaches 150 ppm or higher, manure applications should be discontinued until nutrient harvest by the orchard reduces P test levels to less than 150 ppm. To protect surface water quality against discharges of P, adequate soil and water conservation practices should be used to control runoff, erosion and leaching to drain tiles from fields where manure is applied.

Potassium (K)

Potassium (K) does not pose a threat to surface or groundwater resources. Apply K when soil or tissue analyses indicate a deficiency exists. Applications of 150 to 300 lb K2O/acre will correct most deficiencies. Stone fruit plantings on light, sandy soils may require these rates as a maintenance program every 3 to 5 years.

Michigan Right-to-Farm Guidelines for manure applications in the orchard

When followed by producers, the Michigan Right to Farm generally accepted agricultural and management practices (GAAMPs) help protect the waters of the state from the release of pollutants in quantities or concentrations that violate established water quality standards. Conformance with GAAMPs provides farmers with protection from nuisance lawsuits.

In addition to the management practices recommended previously in this article, other GAAMPs for manure application in the orchard include:

• Manures should be uniformly applied to soils.
• The amount of manure applied should be known, so manure nutrients can be effectively managed.
• Manures should not be applied within 150 feet of surface water.
• If manure is temporarily stacked in the field/orchard:
• Keep stockpiles at least 150 feet away from surface waters
• Keep stockpiles at least 150 feet away from non-farm homes
• Spread manure as soon as orchard and weather conditions allow
• Application of manure to frozen or snow-covered soils should be avoided.
• Keep records of manure analysis, soil tests and rates of application.

For more information on the Right to Farm GAAMPS, go to: http://michigan.gov/mda