Soil Sampling & Testing Service
From Agricultural Testing
Soil testing provides an index for the nutrient availability in soil and is a critical step in nutrient management planning. It has become an important tool for assessing soil fertility and arriving at proper fertilizer recommendations. It is also a valuable management aid for studying soil changes resulting from cropping practices and for diagnosing specific cropping problems.
However, soil sampling techniques, timing of sampling and type of analysis need to be considered for accurate results. The effective utilization of soil testing results depends on the proper and representative sampling of the soil. Proper soil sampling will provide accurate soil test results and reliable nutrient recommendations.
Answers to special questions concerning soil sampling are offered here but further information and guidance must be obtained from your fertilizer dealer or crop consultant.
When to sample depends on whether you are from a temperate or tropical zone. In temperate and polar regions generally four seasons are recognized: spring, summer, autumn, and winter. The winter season determines your decision as to when to sample. Some advices are as follows:
- Cultivated fields for spring seeding should be sampled after October.
- Fields for fall-seeded crops should be sampled one month before seeding
- Forage fields for seed, pasture or hay may be sampled after September 1.
Frozen and water-logged soils should not be sampled because of the difficulty in obtaining a representative sample.
In some tropical and subtropical regions it is more common to note of the rainy (wet, or monsoon) season versus the dry season. In Nicaragua , for instance, the dry season is called Summer (October to May) and the rainy season is called Winter (April to November) even though it is located in the northern hemisphere.
In other tropical areas, for example Thailand , a three-way division into hot, rainy and cool season is used. There are special seasons loosely defined in some parts of the world. These are defined based upon important events such as a hurricane season, tornado season or a wildfire season. Take the risk but one primary suggestion is water-logged soils should not be sampled for it would not be representative.
Soil variability is a major concern when deciding how to collect a representative soil sample. Soil samples submitted for analysis should be representative of the field or portion of a field.
- How the soil is handled after sampling is just as important as collecting the soil sample.
- Remove half a kilogram and air dry to stop nitrate build-up. To air dry- spread a thin layer of soil on a clean piece of paper, plastic sheets or clean, shallow containers (plastic, aluminum, etc.) in a clean room at room temperature. Do not dry with artificial heat.
- Moist samples are accepted by laboratories, but they must be delivered to the laboratory the same day as they are collected.
- Samples can also be stored in a refrigerator for a couple of days or frozen if sample delivery is delayed.
- Contact us regarding packing and shipping instructions.
- Pack your dry, refrigerated or frozen samples separately in appropriate containers that could maintain the physical state of the samples.
- Label each sample with your name, address, postal code, field and depth from
- which the sample was taken.