pamphlets
m
Soil Sampling Guidelines
Sampling Procedure
- A Beater soil sampler (See Figure 1) with a clean packet attached should be used to take the sampled. Do not use a spade, screw-in type auger, or any other implement.
- Take 30 - 40 cores from the land or plot being tested (Figures 1 and 2); the more the better.
- The cores should be taken in a zig-zag pattern across the land (Figure 3). In the case of row crops, is sampling is carried out before ploughing, samples must be taken in the inter-row, well away from the fertilizer band.
- Control the sampling depth (150 mm for most crops) accurately by inserting the sampler fully.
- Mix the cores thoroughly in the packet and fill the standard soil sample carton with soil. The cartons have a capacity of about 400 mL.
- Do not attempt to dry soils in an oven, as heat can alter the soil test results. Soils may be sent to the laboratory in a moist state.
- Fill in the green Soil Testing Submission Form accurately.
- Payment should accompany the samples.
Area to Sample
The area sampled should ideally represent only one soil type, and should in the past have been subjected to the same fertilization, liming and cropping management.
Cores for a single sample should not be taken from more than one land or plot. Edges of fields as well as unusual areas within the field, such as fertilizer or lime spills or ash dumps, should be avoided when sampling.
Patches in the land where plant growth is poor often reflect localized soil fertility problems. In order to identify the problem, it is important to take separate samples from the weak areas while the crop is on the land; once the crop is removed, identification of these areas is usually impossible.
Figure 3. Zig-zag sampling patterns for fields of different shapes
Depth of Sampling
Row crops 0 - 150 mm Vegetables 0 - 150 mm Establishment of pastures 0 - 150 mm Maintenance of established pastures 0 - 100 mm Since, in certain parts of KwaZulu-Natal, subsoil acidity is a serious problem for growing deep-rooted crops such as maize, it is sometimes recommended and necessary to take sub-soil samples. To do this, a long screw-in type auger is used, with samples taken at 150 mm increments to a dept of 900 mm. Samples from a number of auger holes are combined to form composite samples for each of the successive depth increments.
Time and Frequency of Sampling
For crops and vegetables, samples should ideally be taken after the previous crop has been removed and the land ploughed, but it is often necessary to sample before harvest (taking care to avoid fertilizer bands).
Established pastures can be sampled at any time of the year. An obviously important consideration is the time required for the ordering and transport of fertilizers and lime, and the incorporation of these products.
Where major soil fertility problems are being corrected, it is recommended that the soil be tested each year. However, once the required nutrient status has been achieved, soil testing every 2 to 3 years is usually adequate.
Figure 1. Thrusting the soil auger into the soil.
Figure 2. Forcing the subsample (core) form the sampling bit into the plastic bag.
______________________________
Soil Fertility and Analytical Services
KwaZulu-Natal Department of Agriculture
Private Bag X9059
Pietermaritzburg
3200Contacts:
Ruby Punwassi or Zandra Smeda
Telephone: (033) 3559 455/450
Facsimile: (033) 3559 454
