Table of Contents
Agricultural, industrial, municipal, and yard wastes can be valuable to farmers provided they are properly managed. Waste analysis is an important key to proper management. By determining the amount of nutrients and potentially harmful elements in the waste, and by determining the prodluct's liming characteristics, growers and other potential users of these materials can make informed decisions about their application. From both an economic and an environmental standpoint, this information benefits all North Carolinians.
This fact sheet will clarify the importance of waste analysis and describe the procedures for taking reliable samples and submitting them to the Waste Advisory Section at the Agronomic Division of the North Carolina Department of Agriculture (NCDA).
Waste products must be used or disposed of
with environmentally sound management practices in order to prevent damage
to our natural resources. Farms' food-processing plants, textile manufacturers,
pharmaceutical companies, wood and paper producers, and municipalities
all generate a variety of waste products--the disposal of which must be
managed somewhat differently depending upon the source and the intended
use. Most waste must undergo some form of processing before it can be
As landfill space becomes increasingly limited,
waste producers are being forced to seek alternative disposal sites or
potential recycling opportunities. Land application is one of the safest
and most common alternatives provided that best management
Composting can reduce volume, improve uniformity, and sometimes alter the nutrient availability of waste products. Because of this, samples from the final material that will be applied must be analyzed.
Nutrient concentrations vary in most organic
Waste users who fail to test each waste material are faced with a number of questions they simply cannot answer. Are they supplying plants with adequate nutrients? Are they building up excess nutrients that may ultimately move to streams or groundwater? Are they changing the soil pH to levels that will not support plant production? Are they applying heavy metals at levels that may be toxic to plants and permanently alter soil productivity?
Because environmental damage and losses in plant yield and quality often happen before visible plant symptoms, growers and other users should always have their wastes analyzed by a competent laboratory and their application rates determined by a knowledgeable agronomist.
The Waste Advisory Section of the NCDA Agronomic
Division analyzes wastes, interprets analytical results, and provides
management recommendations for citizens of North Carolina. The fee is
$4.00 per sample. Private laboratories also offer some of these services
A good analytical service should always determine
the concentrations of essential plant nutrients, including
Proper sampling is the key to reliable waste
analysis. Although laboratory procedures are extremely accurate, they
have little value if the samples fail to represent the waste product.
The importance of careful sampling becomes clear when one recognizes that
laboratory determinations are made on a portion of the sample submitted
that is as little as
Waste samples submitted to a laboratory should
represent the average composition of the material that will be applied
to the field. Reliable samples typically consist of material collected
from a number of locations. Precise sampling methods vary according to
Ideally, growers should not base application rates on laboratory test results from previous years because nutrient concentrations can change significantly, particularly when the waste has been exposed to the environment. For example, nutrient levels in an anaerobic lagoon can be influenced by rainfall. Stockpiled litter or other wastes may also change significantly if left unprotected. Municipal and industrial wastes also vary as production demands alter inputs and processing.
Liquid waste samples submitted for analysis should meet the following requirements.
Ideally, some liquid wastes should be sampled
after they are thoroughly mixed. Because this is sometimes impractical,
samples can also be taken in accordance with the suggestions
Lagoon Liquid: Premixing the surface
liquid in the lagoon is not needed, provided it is the only component
that is being pumped. Growers with
Samples should be collected using a plastic
container similar to the one shown in
One quart of mixed material should be sent to the laboratory. Galvanized containers should never be used for collection, mixing, or storage due to the risk of contamination from metals like zinc in the container.
Liquid Slurry: Waste materials applied
as a slurry from a pit or storage basin should be mixed prior to sampling.
Waste should be collected from approximately eight areas around the pit
or basin and mixed thoroughly in a plastic container.
For analysis, the laboratory requires
Solid waste samples should represent the
average moisture content of
A one-quart sample is required for analysis.
Samples should be taken from approximately eight different areas in the
waste, placed in a plastic container, and thoroughly mixed. Approximately
one quart of the mixed sample should be placed in a plastic bag, sealed,
and shipped directly to the laboratory. Samples stored for more than
Poultry In-House Manure Sampling: Nutrient concentration varies widely in poultry litter both from house to house and within each house. If waste is to be applied by house, each one should be sampled separately.
Waste samples should be collected from
Poultry Below-House Manure Sampling: In a high-rise system, manure is deposited below the poultry house. If the system is properly managed, the manure should be fairly uniform in moisture and appearance.
Approximately eight samples should be collected
throughout the storage area. If manure in certain areas differs in appearance,
take samples proportionate to the size and number of these areas. For
Stockpiled Litter: Ideally, stockpiled waste should be stored under cover on an impervious surface. The weathered exterior of uncovered waste may not accurately represent the majority of the material. Rainfall generally moves water-soluble nutrients down into the pile. If an unprotected stockpile is used over an extended period, it should be sampled before each application.
Stockpiled waste should be sampled at a depth
of at least
Surface-Scraped Waste: Surface-scraped and piled materials should be treated like stockpiled waste. Follow the same procedures for taking samples. Ideally, surface-scraped materials should be protected from the weather unless they are used immediately.
Composted Waste: Ideally, composted
waste should be stored under cover on an impervious surface. Although
nutrients are somewhat stabilized in these materials, some nutrients can
leach out during rains. When composted waste is left unprotected, samples
should be submitted to the laboratory each time the material is applied.
Sampling procedures the same as those described for
Samples submitted to the NCDA Agronomic Division
will be analyzed and the sender will receive a report that lists the concentration
of each plant nutrient and several potentially harmful elements. Specific
concentrations of nutrients and other elements are reported on a dry-weight
basis for solid wastes; results for liquid wastes are reported on a
The most useful information is nutrients
available for the first crop. These levels are predicted on an as-is or
wet basis. Nutrient availability is predicted by estimating the nutrient
release rate from the waste and a nutrient loss for a specific
Nutrients listed in the report as "availab]e for the first crop" should be used in determining the actual application rate to meet a specific plant nutrient requirement. For the availability prediction to be reliable, growers must have properly identified the type of waste and the application method on the information sheet submitted to the laboratory.
For waste materials suspected of containing
liming materials, such as stack dust or lime-stabilized waste, a calcium-carbonate
Growers who use waste materials as fertilizer
or a source of lime should maintain records of the analytical results,
application rates, and soil tests for each application site. Growers are
also advised to take plant samples to evaluate their nutrient management
program, identify corrective actions for current crops, and plan improvements
Owners of waste application sites may also wish to sample surface and groundwater supplies once a year to confirm that nutrient-management programs are not adversely affecting the environment. Where waste products have been applied regularly for a number of years, growers should also monitor the buildup of metals that can affect long-term soil productivity, particularly zinc and copper. For municipal and industrial waste sites, nickel, cadmium, lead, and sodium should also be monitored.