INTRODUCTION
We live in an era of increasing concern over the conservation and
management of our renewable and non-renewable resources. We seldom
think of soil in these terms, and yet improper development or natural
erosion can devastate a landscape that nature took centuries to create.
Similarly, the mineral elements in the soil that nourish growing plants can
be depleted through repeated cycles of cultivation and harvest, resulting in
an exhausted soil incapable of supporting healthy plant growth.
The Garden Guide Manual is concerned with the three major mineral
elements which plants absorb in large quantities during growth - nitrogen,
phosphorus and potassium (potash). Soil pH is also considered in detail
because the pH value directly affects the availability of a soil’s mineral
nutrients to the growing plant. Soil texture and organic matter content are
briefly discussed and the manual outlines the proper technique for
collection and preparation of soil samples.
3
SOIL TEXTURE
Through the process of weathering, mineral rocks are broken down over
long periods of time into fine particles of sand, silt, and clay. The presence
of these particles in varying proportions determines a soil’s texture. A
predominance of sand gives the soil a gritty feel when rolled between the
fingers. A soil with a high silt content has a silky feel much like talcum
powder. When moistened, clay is sticky and plastic in texture. A loamy soil
is an equal blend of these three fractions. Garden soils of intermediate
texture - the sandy loams, loams, and silt loams - are easiest to cultivate.
ORGANIC MATTER
Organic matter is composed of partially decayed and partially synthesized
plant and animal residues present in the soil. The decomposition of
organic matter releases mineral nutrients, particularly nitrogen, into the soil
in available forms for plant use. Organic matter also improves tilth and
water holding capacity. The garden hobbyist can improve the organic
content of his soil through the application of compost.
4
SOIL SAMPLING
Representative soil sampling is the first step in successful soil fertility
management. Accurate interpretation of soil test results largely depends
on the care and organization applied to the sampling process.
Get to know your garden. Supplement soil tests with careful observation of
the effects of shade, moisture, temperature, weeds, insects, and other
conditions influencing plant development.
Establish sampling areas. Different plants prefer different soil conditions.
Your garden may contain several soil types. Divide your garden into
distinct sampling areas, so that test results may be interpreted in terms of
the soil type and the plants to be grown in a specific area.
Take composite samples. Within a particular sampling area, collect and
thoroughly mix at least five random samples. The resulting composite
sample insures that test results will be representative of the entire sampling
area. Do not mix samples from separate sampling areas.
Sample the root zone. Collect samples directly where plants are to be
grown and to a depth compatible with root development. The root zone is
where the transfer of nutrients from soil to plant occurs. Samples should be
taken 2-3 inches below the soil surface for garden crops.
Make sure samples are free of foreign objects. Scrape away ground cover
before sampling. Avoid contamination with fertilizers and sprays. Minimize
contact with hands. Use a clean trowel, spoon, knife or soil sampling tube
to collect samples. A sampling tube permits inspection of core samples
and accurate measurement of sampling depth. Collect the composite
sample for a given area in a clean plastic bag, paper cup, or other
suitable container. Label the container to identify the sampling area.
Keep a soil-plant diary. Periodic testing and accurate recordkeeping
provide the only means of correlating test results, fertilizer applications,
and plant growth. Record the specific areas from which soil samples were
taken. Use the form at the back of the manual or devise your own.
SOIL PREPARATION
1. Spread out the composite sample on a clean sheet of paper or plastic.
2. Allow the soil to dry several hours or overnight. Do not bake the
samples to accelerate drying.
3. Remove foreign matter such as leaves, twigs and stones.
4. Gently crush soil to remove lumps.
5. Sift the sample through a screen or flour sifter to give a uniform sample.
5
Loading...