A Quick Primer on Soils - Part A

Soil is a critical part of any field or orchard production system. It is the basis of your crop's growth. Soils can be highly variable in Ontario thanks to how our soils were formed and what we have done to them since. There are a number of tools at your disposal that can help in assessing your soil or in diagnosing soil based problems. Part A of this Primer discusses soil sampling, soil texture and soil pH. Part B looks at soil structure and some related soil problems in greater detail.

Soil Sampling

Soil sampling prior to tree establishment is crucial to ensuring that soil pH and nutrient levels are at the optimum levels. Before the trees are planted it is much easier to get fertilizer evenly mixed in the soil profile. The type and depth of soil sampling will be determined by the purpose or use of the sample. Regardless, the basic sampling method remains the same:

• Use a stainless steel soil probe or auger for collecting the sample.
  
• Use a clean plastic pail to contain the sample.
  
• Use a zig zag pattern across the field to ensure the sample reflects the whole field.
  
• Take one composite sample for every 25 acres or less.
  
• If sampling problem areas, ensure that the sample represents the problem area and take a sample from the "good" or better area too.
  
• Ensure that the sample is well mixed
  
• Sample to 6 in (15 cm) for most soil samples for basic fertility, pH, etc. This is the depth that Ontario recommendations are calibrated for.

Soil pH

Soil pH is the measurement of the hydrogen ion activity or concentration in the soil solution. This has an impact on the availability of most nutrients. It can cause the concentration of some elements to rise to toxic levels e.g. aluminum. It also affects the activity of soil organisms that build soil structure, cycle organic matter or fix nitrogen in legumes nodules. Soil pH also has a dramatic effect on the performance and breakdown of some pesticides e.g. Pursuit.

Soil pH can be measured with a standard lab test using an electrode and a saturated paste. There are also a number of hand held meters available. They range greatly in cost and accuracy. Generally any meter that is directly inserted into the soil is not adequate (think of the variation that we get with soil moisture over the season -the hydrogen ions are held in the soil moisture, so pH is very difficult to measure in a dry soil). Usually a reasonably accurate meter costs in the range of $100 to $250. The meters can do dual purpose, many growers also use them to check the pH on spray water.

Soil Texture

Soil particles come in three main sizes; sand, silt and clay. Within these, especially the sand, there are further breaks in particle size. There is a lab test called a particle size analysis that will give a complete breakdown of soil texture. The test is available from many Ontario labs. The information can be used to calculate the water holding capacity of a soil for irrigation scheduling. Soil texture in most fields is highly variable. It can be assessed quickly by hand with a little practice. (If you want a copy of the hand texturing key email me at anne.verhallen@ontario.ca)

If you are looking for soil sample tubes, soil augers or soil pH meters, here are a few suppliers:

Halltech Environmental Inc
129 Watson Road.
Guelph, Ontario N1L 1E4
1-519-766-4568

Spectrum Technologies Inc.
23839 W. Andrew Road
Plainfield, Illinois 60544
1-800-248-8873

Gemplers
100 Countryside Drive, P.O. Box 270
Belleville, Wisconsin 53508
1-800-382-8473

Labon Inc.
1350 rue Newton
Boucherville, Quebec J4B 5H2
450-641-1050 or 1-800-565-1050

Related Links:

• Halltech Environmental Inc
• Spectrum Technologies Inc.
• Gemplers
• Labon Inc.

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