We have been looking at your soil test and what those numbers mean to your farm. We need to take a break from reading the soil test to discuss a soil testing program for your farm.
Soil testing is the foundation to a good fertility program. Without a soil test, your nutrient program is simply a guess, where you may be under or over applying nutrients that are required by the crop.
Soil testing should be done at least every three years, more often for high value crops.
Proper soil testing techniques is important to ensure accurate test results. This includes:
• a sample that accurately represents the field
• handled and packaged properly
• has the correct information on your local agricultural laboratory forms
EQUIPMENT – clean plastic pail (don’t use metal pails as they can contaminate the sample), soil probe, shovel or trowel, permanent marking pen, sample boxes or bags and Laboratory submission forms.
METHODS – there are two sampling methods. This can be done by the farmer or there are companies (Agromart and Cavendish for example) that offer soil sampling and Field GPS mapping services.
COMPOSITE – this method is used most often. Several subsamples are taken throughout the field and mixed for one representative sample.
GRID – the field is divided into a grid and
samples are taken at each grid point with its location recorded by GPS. These samples are kept separate. This type of sampling can show variations across the field and is helpful for diagnosing crop problems. The data can also be coordinated with a tractor mounted GPS system for variable rate lime and fertilizer applications.
WHEN YOU SHOULD SAMPLE? Sample the same time of year, usually spring or fall. Soil test levels change during the season therefore samples need to be taken at the same time of the year so that samples can be compared over time. Do not sample when the fields are wet as it increases drying time at the lab and can cause mould growth in the samples.
WHERE YOU SHOULD SAMPLE? Good soil sampling technique is critical for accurate results.
• Take a number of subsamples throughout the field (10-20 subsamples depending on the field size). Mix in a clean plastic pail and take one representative mixed sample.
• Walk in a W, S or zigzag pattern when taking samples.
• Sample crops to below the plow layer, about 6 “(15 cm) or in permanent sod or no till, 2-3” (5-8 cm).
• Do not include grass, debris or rocks.
• Don’t sample field entrances, edges, depressions, hill tops, old burn sites or where animals tend to group.
• Soil sample areas that you had poor crop growth separately so it can be compared with a sample from a good area.
• Ensure the sample box or bag is clearly labeled with your name, field identification and address.
• Send to your local agricultural lab along with their submission forms.
Remember that the soil analysis from the lab is only as good as the sample that you took. Poor sampling techniques will not provide accurate results and may be a waste of your time and money!
Next article we’ll continue to take a break from reading soil tests and look at what makes a good manure test.
Any questions on this article or other fertility issue? Contact Lise LeBlanc at (902) 792-2636 or lise.leblanc@ns.sympatico.ca.
