ATTRA Question of the Week

J.C.
Washington

Answer: I am pleased to provide you with information on sampling and testing of agricultural soils for nutrient content.

Farmers test their soils based on their management practices and objectives. Some farmers who grow commodity crops such as wheat, potatoes, or corn, or forages such as alfalfa or grass hay, will test every one to three years. The criteria that determine when a soil should be tested are as various as the types of farms and farmers in America, but in general farmers will test for the following reasons:

• to obtain a baseline of information on nutrient profile of a soil,
• to chart the changes in soil nutrient status, organic matter, and pH due to management inputs, and
• to determine the fertilizer requirement for a particular crop.

Many land grant universities and private labs offer fee-based testing services. For most farmers, the local cooperative Extension agent is the contact for obtaining materials, education, and resources for correct sampling and fertility recommendations. Some Extension agents will even send the samples to the lab, receive them back, and make appropriate fertilizer recommendations on site.

Each state has a cooperative Extension service with agents in most counties. The USDA maintains an online database of local cooperative Extension offices on its website at http://www.csrees.usda.gov/Extension/index.html. You will also find the phone number for your cooperative Extension office in the county government section of your telephone directory.

There are also private labs available. The ATTRA website has a list of labs, which can be accessed at http://www.attra.org/attra-pub/soil-lab.html. The private labs will often offer information on sampling technique and fertility management as well.