Identification of areas to sample
Although compartments can be sampled individually, foliage analysis results will be more useful if they are derived from a sampling programme designed to examine a particular problem. Sampling might for example be aimed to assess or monitor the nutritional status of a certain age class of Sitka spruce on a particular soil type.
Having identified the problem and the crop to be sampled:
- It should then be subdivided into areas of good and poor growth
- Foliar samples should be taken from both these areas as relative nutrient values assist in the interpretation of the results of analysis
- Each good and poor sample should comprise of a set of 5 current years’ shoots for conifers and should be accompanied by a SiteRecordForm(PDF-84K).
Timing of sampling
Samples may be collected at any time of day from the first week in October to the end of the second week in November.
Deciduous conifers and broadleaves should be sampled in late July and August after shoot growth is complete and before needles or leaves begin to change colour.
It is desirable to avoid sampling after periods of prolonged rain because nutrients, particularly potassium, may leach from the needles or leaves. However, this may not always be possible and collection of samples will depend on local weather conditions and previous experience.
Selection of trees to sample
Five typical dominant and co-dominant trees should be sampled to form a composite set of 5 shoots (one sample) within each category.
Age of foliage
Only shoots of the current year should be taken, needles or leaves should not be stripped off the shoot. Exceptions to this are large leaved species i.e. horse chestnut, sycamore. For more details see broad-leaved amenity trees.
Position and size of sample required
Position of sample shoot
Conifers: Shoots should be taken from the first whorl below the leader, excluding any Lammas growth. One shoot is taken per tree.
Broadleaved trees: Undamaged, fully expanded leaves should be collected from the outside of the crown.
Size of sample dispatched in bag for analysis
A sample consisting of five current year’s shoots from conifers is sufficient for analysis, irrespective of the growth rate of the trees sampled. Where shoots are too long to fit in the polythene bag they should be carefully cut in two. Enough leaves to cover an A4 sheet of paper, excluding the petioles.
For more information see broad-leaved amenity trees
Note that:
- Shoots or leaves must be fully exposed to sunlight as shading affects the nutrient content.
- Leaves should be collected from a minimum of 5 trees.
However, where the total number of trees available is small, less sample (than quoted above) can be accepted.
Please contact us if there are any doubts.
