There is no better time to start thinking about your next cropping season than right after you finish your current harvest. The yield maps and memories of the season are still fresh in your mind, and you may want to do a little investigating to determine why some areas of your farm did better or below average. One of the best tools you can use at this point in the year is soil sampling.
Whether you hire it done or DIY (and there are many resources to help you do this), soil tests can give great insight into what’s going on below the surface. The first step is to determine if you want whole-field tests or 1- to 2.5-acre grid samples. Whole-field tests can give you a basic understanding of what your farms nutrient levels are. They can be a cost-effective tool and their accuracy can be improved by sampling uniform areas and smaller fields. Grid sampling takes this a step further and can provide more insight by revealing soil nutrient variations across the farm. If you have the means to do so, you can then write prescriptions for variable-rate nutrient application – potentially saving money and raising yield.
If you take your own samples, first decide on the area to sample. For whole fields, keep the area under 40 acres and as uniform as possible. There are phone/tablet apps available if you want to do your own grid sampling. Most surface soil samples are collected to a depth of 8”. You may also pull a deeper sample if you are interested in testing for residual nitrate. Pull at least 10-15 cores across the field to make up the approximate 1 pint of soil needed by the testing lab. Mix your cores thoroughly and follow the shipping procedures specified by the lab analyzing your soil.
Many labs will provide nutrient recommendations based on the information provided when the sample is submitted. Your local state university can also be a good source of information on nutrient requirements for multiple crops. Two of the most important numbers on your soil test results are the CEC (cation exchange capacity) and pH, which can affect the availability of many other nutrients. CEC is a function of the soil physical property which measures its ability to hold certain nutrients, and is not easily changed. Most soils are slightly acidic (pH less than 6.0) to neutral (pH 6.0-7.0). You can raise soil pH by adding lime. If your soil is basic (pH above 7.0), it is a little more difficult to bring down, and growing high pH tolerant crops is a good management option. The other important items on your soil test are the N-P-K numbers, which are the three macronutrients most important for plant growth.
There you have it. With an afternoon or two, a soil probe, and a plastic bucket, you can start to gain a better understanding of what is happening under your feet on your farms. If you have any questions regarding soil sampling or any other agronomic questions, reach out to your local dealer, Sales Agronomist or District Sales Manager.
