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Interpretation of Organic Matter Levels in New Jersey Soils

COVID-19 UPDATE (7/15/20)

Rutgers Soil Testing Lab staff are at work, providing fee-for-service analysis of soil samples and generating reports/recommendations for all clients. Appropriate safety procedures and precautions are being followed to assure and protect the health of staff, including social distancing and use of personal protective equipment, sterilizing work surfaces and incoming packages, etc.

However, the Soil Testing Laboratory will remain closed to everyone other than staff until further notice; the building that houses the STL is not open to the public. Therefore all samples must be delivered by US Postal Service, UPS, FedEx, etc.

Because many county offices of Rutgers Cooperative Extension are also closed to the public, soil test kits may not be available for purchase locally. Use this alternative: How to get your soil tested, and find the appropriate Soil Sampling Instructions and Soil Test Questionnaire; headings describe different land use and "crop" scenarios. Read and follow the instructions; download and fill out the questionnaire; then send soil sample and questionnaire with payment to the lab.

Soil test reports are generated from the analytical data and include soil amendment recommendations; the reports are usually sent by email, with a copy sent also to the local County Cooperative Extension office for further consultation, if needed.

Organic Matter Soil Texture
% Loamy Sand Sandy Loam Loam Silt Loam
Less than 0.5% Very Low Very Low Very Low Very Low
0.5 to 1.0% Low Very Low Very Low Very Low
1.0 to 1.5% Medium Low Very Low Very Low
1.5 to 2.0% High Medium Low Low
2.0 to 2.5% Very High High Medium Low
2.5 to 3.0% Very High Very High Medium Medium
3.0 to 3.5% Very High Very High High Medium
3.5 to 4.0% Very High Very High High Medium
4.0 to 5.0% Very High Very High Very High High
More than 5% Very High Very High Very High Very High

Notes

Soil textures finer than those listed (clay loams and clays) can be evaluated using the "silt loam" column.

Organic matter values are expressed as percentage by weight basis. The value accounts for soil humus and easily oxidized organic fractions of the soil but may not include unreactive fractions.

Although organic matter would include anything organically-derived, samples are sieved to remove gravel (>2mm), which may also remove particulate organic matter as well, including sticks and roots.

Organic matter content is a dynamic soil property, strongly influenced by management and affected by environmental conditions as microorganisms continue to decompose the organic matter and release nutrients.

While organic matter is a valuable soil component for chemical, physical, and biological reasons, amending soils to organic matter content greater than 10% is not recommended for general use as plant growth media.