Land application of organic waste material is a desirable disposal alternative. Not only are costs usually lower relative to other disposal methods but the waste material is beneficial for the soil and crop production. Organic materials contain nutrients needed for crop growth and also to improve soil tilth, increase water holding capacity, lessen wind and water erosion, improve aeration, and promote soil biological activity. Application of organic waste materials to land must, however, take into account both crop needs and the potential for environmental degradation. Whether land disposal of organic waste is viewed as a nutrient resource or as a waste disposal option, certain principles needed to be followed for optimum nutrient utilization and minimum environmental impact.
Nutrients in Organic Matter - Crop Growth Considerations
Most organic materials contain significant quantities of plant nutrients, especially phosphorus (P), nitrogen (N) and potassium (K), and should be managed as a mixed fertilizer to satisfy crop nutrient needs. Nutrients should not be applied in quantities that exceed the amount needed for optimum plant nutrition.
Because many Ohio soils have relatively high P fertility levels, efficient management of organic matter P is of primary concern. P readily accumulates in soils if applied in quantities greater than those removed by crops. Crops grown in soils with very high phosphorus levels may actually produce lower yields due to nutrient imbalances.
Phosphorus applied to fields can move into bodies of water during erosion and runoff events, and is largely responsible for the accelerated eutrophication of many bodies of water in Ohio. Concentrations of algal-available phosphorus (the phosphorus responsible for eutrophication) increase as soil test phosphorus levels increase, meaning that as soil concentrations of phosphorus rise, the potential increases for soils to degrade the environment through runoff and erosion. Slowing the eutrophication of Ohio's surface waters involves reducing the amount of phosphorus delivered to these waters.
Agronomic crops grown in Ohio rarely respond to applications of additional phosphorus when soil test levels exceed 30 ppm (60 lb/acre) of phosphorus. There is no agronomic justification for raising soil test phosphorus levels above those that provide adequate nutrition to the crop. Increasing soil test phosphorus levels at the soil surface increases the pollutant potential of the land.
High levels of organic materials applied to soil may increase salts in soil, impair seed germination and reduce plant stands. Most organic materials also contain much more potassium than magnesium or calcium. Long term application of this material to soils may raise the ratio of potassium to magnesium and calcium sufficiently to retard crop growth. To adjust the ratio, additional magnesium and/or calcium may have to be added as dolomitic or calcitic limestone. When organic materials are regularly applied to cropland the soil should be tested regularly to monitor nutrient levels. If a mineral imbalance is suspected, plant tissue analysis should be made to determine the extent of the problem.
Applications of organic materials should not provide more available nitrogen (N) than is needed by the succeeding crop. The determination of total available nitrogen should include credits for any contributions of the present or preceding crop, any nitrogen fertilizer added, and available nitrogen provided by previous waste applications.
Method of waste application to the soil can affect the amount of nutrients available for crop uptake. Availability of N in organic waste depends both on the method of application and days to incorporation into the soil. Organic materials should be incorporated into the soil as soon as possible since most N losses occur within 24 hours of application. Injecting, chiseling, or knifing liquid materials into the soil minimizes odors and nutrient losses. Phosphorus and potassium contained in organic waste is generally readily available in the soil unless removed by surface runoff or soil erosion.
When planning for land application of organic wastes, sufficient land area to accommodate the nutrient supply must be considered. A conservative approach in determining the amount of land required is to base application rate on the nutrient removal of the harvested crop. This approach will prevent nutrient buildup in the soil beyond suggested agronomic production levels. For information on determining required land area for waste application based on crop nutrient removal, refer to "Land Required for Manure Application Based on Crop Removal" in OSU Extension Bulletin 604 (Ohio Livestock Manure and Wastewater Management Guide).
Organic material should be tested prior to application since nutrient composition of organic waste is affected by collection, storage and the waste handling system. Soils receiving organic materials should also be tested for available nutrients before application. Nutrients supplied from commercial fertilizer and/or manure sources must also be considered in calculating the appropriate application rate. Table 1 provides recommended maximum organic material application rates for different soil test levels and site conditions. A computer program available from Ohio State University Extension can also assist in selecting appropriate application rates. ECP 102, Crop Nutrient Management, is available from your local county Extension office.
Nutrients in Organic Matter - Environmental Considerations
Site characteristics, application methods and management, cropping system, and erosion/runoff abatement practices all affect the quantity of waste that can be safely applied to a given site. Since most of the nutrients contained in waste materials are water soluble, the potential for these nutrients to cause surface water pollution is directly related to the level of water runoff from the application site. Waste organic matter particles are also subject to movement in surface water runoff and can contribute directly to pollution of surface water supplies.
Water and nutrient runoff potential are affected by numerous factors, some of which are fixed by the nature and location of the field and others that can be altered through management. Runoff potential must be determined on a site-by-site basis.
Proximity of surface water to application site. Streams or bodies of surface water located near waste application sites are more likely to receive waste derived nutrients. The extent and management of buffering areas such as other fields, pasture, wooded area, etc. between the source of nutrients and the water supply can greatly attenuate the movement of nutrients to the water supply.
Slope steepness and complexity. Runoff is more likely from fields sloping steeply and evenly toward a water source than fields with a gentle or no slope. Fields with areas of depression between the site of application and the water source have a lower potential for nutrient runoff.
Soil and weather conditions. Organic materials should not be applied to wet, sloping, or frozen soils if normally anticipated rainfall would cause overland water flow from the point of applications. Liquid organic sources should not be applied at rates that exceed the volume needed to bring the soil to field moisture capacity. Check soil moisture before applying liquid wastes and adjust application rates to avoid runoff. Estimate soil moisture based on soil feel and appearance. Refer to EX 704, Land Application of Manure and Waste Water - Part I. Available moisture capacity for different soils can be found in the Ohio Irrigation Guide available from the state Soil Conservation Service or the Department of Agricultural Engineering, The Ohio State University.
Soil type and surface condition. Soils with low infiltration rates and/or soils with limited water-holding capacity are more likely to promote water runoff than soil types that absorb and retain large quantities of water. A rough or covered soil surface also reduces runoff compared with soil surfaces that are smooth or have very little residue cover.
Subsurface drainage. Subsurface drainage systems can reduce the water runoff and allow the nutrients contained in the waste to be absorbed into the soil profile.
Waste application method. Surface spreading and subsurface injection are the most common land-application methods. Injection or incorporation by primary tillage promptly following application will reduce the potential for direct runoff as well as reduce odors and volatile N loss.
Application equipment calibration. It is important that equipment for applying waste be properly calibrated and be able to uniformly apply waste material. For more information on spreader (manure) calibration, refer to EX 707, Land Application of Waste...Spreading and Injection, available from your local county Extension office.
When organic materials are applied in excess of the amount that can be effectively utilized based on crop nutrient needs, special guidelines should be considered. For instance, in many situations, relatively deep incorporation of the organic matter and control of erosion and surface water runoff at the application site can greatly reduce environmental impacts.
If organic materials must be applied to soils with Bray P1 levels greater than 30 ppm (60 lb/acre) of phosphorus in the top 8 inches, the following recommendations should be considered:
No additional phosphorus fertilizer should be used.
Crops should be monitored for nutrient deficiencies using plant tissue analysis. Increasing soil test phosphorus and potassium levels above recommended levels increases the probability of yield reducing nutrient imbalances.
Organic materials should be applied in quantities such that the long-term phosphorus level at the soil surface does not increase appreciably. This can be accomplished by:
a) Apply no more nitrogen or phosphorus (whichever is lower) than will be removed by the next crop (one season) if surface-applied or incorporated to a shallow depth (within the tillage depth).
b) Incorporate waste below the depth of tillage, generally deeper than 8 inches, using rates great enough to satisfy nitrogen requirements for a succeeding grass crop. Producers should be aware that this system may promote development of a soil zone with abnormally high nutrient concentrations. If this zone is brought to the surface by subsequent tillage, potential for P runoff is increased. Fields under such management should be sampled deep enough to include the zone of incorporation. On soils with high nutrient levels, application of organic materials should be skipped for one or more seasons to allow depletion of accumulated nutrients.
Soil and water conservation practices should be implemented to control erosion and minimize runoff.
Application of organic material that contains P is not recommended for crop production where the Bray P1 level in the top 8 inches of soil exceeds 300 pounds of phosphorus per acre.
If deep application and incorporation of organic material are required to insure low runoff and more than 250 pounds of fertilizer P2O5 per acre are required for crop production, soil at the depth of application should not be brought to the surface for three years unless low runoff conditions can be maintained. Moldboard plow depth should be set to two-thirds the depth of incorporation during this three year period, and non-inversion tillage tools such as chisel plows should be set no deeper than the depth of application. Deep incorporation of less than 250 pounds of P2O5 per acre may be conventionally tilled the following year.
Dead leaves and Chipped Wood-
a) Apply to soils in the fall. Adjust C:N ratio to approximately 30:1 by adding additional N (1/3 of additional N should be added in fall and mixed with leaves; 2/3 of additional N should be added in the spring preplant with normal N program).
b) Till leaves and/or chipped wood into soil in the fall.
c) Due to possible higher organic matter-herbicide interactions post emergence herbicide program preferred. If post emergence herbicide program is not practical then adjust herbicide rates for higher organic levels in the spring, when required, similar to high residue no-till crop production.
d) Use the same N and P loading rates and cultural programs as outlined in General Recommendations and Table 1.
Green Grass Clippings or Other Green Plant Materials-
(a) Apply and till into soil at least 6 weeks prior to crop establishment.
(b) Adjust C:N ratio if necessary.
(c) Due to possible higher organic matter-herbicide interactions post emergence herbicide program preferred. If post emergence herbicide program is not practical, then adjust herbicide rates for higher organic levels in the spring, when required, similar to high residue no-till crop production.
(d) Use the same N and P loading rates and cultural programs as outlined in General Recommendations and Table 1.
Composted Yard Waste-
(a) Adjust C:N ratio to approximately 30:1 by adding additional N (1/3 of additional N should be added in fall and mixed with leaves; 2/3 of additional N should be added in the spring preplant with normal N program).
(b) Due to possible higher organic matter-herbicide interactions post emergence herbicide program preferred. If post emergence herbicide program is not practical, then adjust herbicide rates for higher organic levels in the spring, when required, similar to high residue no-till crop production.
(c) Use same N and P loading rates and cultural programs as outlined in General Recommendations and Table 1.
Sewage Sludge and Sludge Products-
(a) Use the same N and P loading rates and cultural programs as outlined in General Recommendations and Table 1.
(b) Use the metal loading rates specified by Ohio EPA (Ohio Sludge Management Manual).
(c) See OSU Extension Bulletin 598 (Land Application of Sewage Sludge) for additional handling and application recommendations.
Organic Amendments for Minespoil Reclamation-
(a) Reclamation of badly degraded land, particularly abandoned acidic coal mine spoil, requires greater additions of soil amendments for vegetation establishment than would be used for agronomic crops. Revegetation of these spoils requires topsoil or an organic amendment like manure, sewage sludge, sludge compost, papermill sludge, yard waste compost, municipal solid waste or other organic products. Often the organic amendments will need to be supplemented with lime and fertilizer nutrients. Organic wastes are usually applied at one-time rates between 50 and 300 tons/acre. These rates must not exceed the metal loading limits specified by Ohio EPA (Ohio Sludge Management Guide). These rates may exceed N and P needs or consumptions by the established crop; therefore a management plan which would minimize the loss from the application site is recommended. There would be a low probability of organic materials with a C:N ratio of greater than a 20:1 releasing surplus N which could leak into surface and subsurface waters. The probability of the mineralization of excessive N is high for organic materials with a low C:N ratio (less than 15:1). Application rates of organic wastes for revegetation are permitted by the Ohio Department of Natural Resources. Reclaimed land will be subsequently treated as agricultural land for purposes of establishing annual N rates and allowable P rates.
Organic Amendments for Previously Reclaimed Minespoil Soils -
(a) Use same N and P loading rates and cultural programs as outlined in General Recommendations and Table 1.
(b) If macropore flow of nutrients and/or organic substances is likely, then conservation plan to prevent loss of nutrients and/or organic substances is recommended.
(c) For sewage sludge use metal loading rates specified by Ohio EPA (Ohio Sludge Management Manual)
(d) For sewage sludge see OSU Extension Bulletin 598 (Land Application of Sewage Sludge) for additional handling and application recommendations.
Animal Manures and Milk House Waste-
(a) See OSU Extension Bulletin 604 (Ohio Livestock Manure and Waste Water Management Guide).
Other Organic Materials-
(a) Based on chemical analysis use the same N and P loading rates and cultural programs as outlined in General Recommendations and Table 1.
(b) If heavy metals are present then use metal loading rates specified by Ohio EPA (Ohio Sludge Management Manual).
(c) If physical characteristics are undesirable or other contaminants are present, additional limitations may be recommended.
Table 1. Recommended Maximum Application Rates for Organic Materials at Different Soil Test Levels1
| Bray P1 Level | Surface Applied on High Runoff Potential Sites2 | Incorporated or Low Runoff Potential Sites3 |
| 0-60 lb P/ac | N needs of non-legume crops
N removal rate of legume crops |
N needs of non-legume crops
N removal rate of legume crops |
| 60-250 lb P/ac4 | N needs or P removal rate
for non-legume crops,
whichever is less
N needs or P removal rate for legume crops, whichever is less |
N needs of non-legume crops
N removal rate for legume crops |
| 250-300 lb P/ac4 | Application for crop production purposes not recommended. | N needs or P removal rate for
non-legume crops, whichever is
less
N or P removal rate for legume crops, whichever is less |
| > 300 lb P/ac4 | Application for crop production purposes not recommended | Application for crop production purposes is not recommended. If application is necessary, apply no more organic material than supplies N or P removal for the next crop, whichever is less. A site plan which controls erosion and runoff is recommended. |
1Applications of organic materials, at rates above these recommendations may require approval and/or permits by appropriate government agencies.
2Surface Application is any application at a depth which would be disturbed by tillage within the next three years. High runoff potential refers to sites where surface movements of manure and/or phosphorus are likely to occur from the field of application.
3Incorporation is any application at a depth which would NOT be disturbed by tillage within the next three years. Low runoff potential refers to sites where surface movement of organic compounds and/or phosphorus from the field of application is not likely to occur under normal weather conditions.
4Yearly plant tissue and soil analysis recommended.
Prepared by:
BMP Team:
Dr. Jay Johnson, Extension Agronomist
Dr. Mark Loux, Extension Agronomist
George Ropp, Agricultural Consultant
James Adams, Agricultural Consultant
All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.
Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
TDD No. 800-589-8292 (Ohio only) or 614-292-1868