D.1.0

INTRODUCTION

Samples of wild blueberry leaves and soils are both used in determining what, if any, adjustments need to be done in a fertility program for wild blueberries. These are generally submitted to a government laboratory, though some private firms are equipped to do this. Growers should enquire if the firms have experience with analysis of wild blueberry samples.

While many growers expect a laboratory to be able to give recommendations based on a soil sample, by far the best measure of the nutrient status of wild blueberry plants comes from an analysis of the leaf tissues. For wild blueberries, soil sampling is most useful for measuring pH (the acidity of soil) and organic matter. Presenting a laboratory with both soil and leaf tissues will generally give the best results.

LEAF SAMPLING

Leaf sampling is increasingly practiced on a number of crops. It is a good indicator of plant nutrition because it allows us to know exactly what amount of nutrients the plant has absorbed. This way we can assess the value of the fertilizer program that is being used or determine whether the leaf tissues are deficient in certain elements. When we look at the results of a tissue leaf analysis, we compare the status of the sample to a set of standards that have been established for the crop.

When to sample wild blueberry leaves

In wild blueberry leaf samples, standards have been established for the one year in the two-year growing cycle when the nutrient levels are most stable. This occurs at the stage of tip die back in the sprout year. This is when the newly emerged stems stop elongating, and the growing tip turns brown (Figure 1). In the province of New Brunswick, this will tend to occur sometime over the last two weeks of July, but timing will depend on when the fields were pruned, the season's weather and the latitude. Compared to other crops, this may represent an awkward time to sample, since it is a full year before the harvest. However, it is the only method available to date. Efforts are being made to develop crop year standards, as well.

How to sample wild blueberry leaf tissues

Sample the field when 90% of the plants have reached tip die back. Fields should be divided into sampling areas. Low spots, trouble spots, and areas with obvious differences in soil type should be treated as separate sampling areas. When sampling, be sure to select stems AT RANDOM, walking in a zigzag fashion. Cut a total of 15 to 20 stems in every ten acre (four-hectare) block at ground level, since all the leaves will be included in the sample. Avoid sampling areas of severe disease or insect defoliation. Samples should be collected in plastic bags or the bags provided by the NBDARD, and kept cool until they are brought to the laboratory. Do not store the stems in paper bags, since they contain Boron. This is an important plant nutrient, and its presence in the bag can lead to false readings of Boron content in the leaf tissues. It is preferable to send the samples early in the week, so that they do not deteriorate by travelling in the postal system too long.

SOIL SAMPLING

The analyses of soil samples helps us to understand the nature of the soil when we give recommendations. It is especially useful for soil features like pH (the acidity, or sourness of the soil), organic matter, and a few of the elements as well. An ideal soil pH for wild blueberries is 4.6 to 5.2, and lime is sometimes recommended if the pH is lower (more acid) than this. Please refer to the other fact sheets in this series (Series D) for more information on wild blueberry nutrition, fertilizer use and liming.

When to sample soils

Soil samples can be taken at any time of the year, but it is most useful if they are taken at the same time as the tissue samples.

How to sample soils

One of the most important steps in a soil testing program is the collection of a sample that represents the area to be fertilized. Divide the field in areas as uniformly as possible in soil type, slope, etc. Within each area of the field, take soil samples at different locations in a zigzag pattern (Figure 2). These will be mixed into one sample representing the area. The number of sub-samples to make up the composite sample is determined by the size of the field. (Table 1).

Table 1: Suggested number of subsamples needed for a representative composite sample based on field size
Field size (hectare/acre)	Suggested number of sub-samples
Less than 2 ha. (5 ac.) 2-4 ha. (5-10 ac.) 4-10 ha. (10-25 ac.) 10-20 ha. (25-50 ac.) More than 20 ha (50 ac.)	15 18 20 25 30
Adapted from Mahler and McDole 1989

Sampling equipment and methods

Different tools such as a soil sampling tool, shovel or spade can be used for sampling. If a shovel or spade is used, dig a V shaped hole. Take a 2.5 cm. (1 inch) slice down one side of the hole to the desired depth (Figure 3). For wild blueberry fields, the sample should only be taken to a depth of 12.5 cm (5 inches), and should not include the plant debris on the soil surface. If a soil sampling tube is used, insert the tube perpendicular to the soil to the desired depth. Use a plastic bucket or other container to mix the composite sample. To avoid contamination of the sample, do not mix the sample with your hands. Ensure that all equipment is clean and especially free of fertilizers. Avoid using a galvanized bucket or a rusty shovel or spade, as these can contaminate the sample. Avoid sampling close to roads and ditches where manure, limestone or fertilizer has been piled and also avoid wet spots in the field. Do not sample when the soil is wet as this makes mixing difficult and creates problems for laboratory analysis.

Label samples clearly, with your name and address, and use a code that corresponds to the associated leaf tissues. The code should refer to the field which it represents, and if this code is maintained over several years it may be useful in measuring improvements or deterioration in the health of the plants or the fertility of the soils.

Attached to this fact sheet you will find a wild blueberry soil and leaf tissue sample information sheet. Filling this out will lead to far better recommendations. More copies of this information sheet, and bags for soil and tissue sampling can be obtained from any regional office of the NBDARD or from the Agriculture Laboratory in Fredericton.

References: Smagula, J. and DeGomez, T. 1987. Leaf and Soil Sampling Procedures. University of Maine, Wild Blueberry Factsheet No. 222 Land Resources Branch, NBDARD. 1994. Soil Sampling. ISBN 1-55137-274-6

Figure 1. The appropriate stage for sampling wild blueberry leaves ("tip dieback").

Prepared by Gunther Reissner, Technician; John Argall, P. Ag., Blueberry Specialist, and Gaetan Chiasson, P. Ag., Horticultural Specialist, N.B. Agriculture & Rural Development.

Winter 1996