Allow the tube to stand for at least 5 minutes. The clearer the extract becomes the
better. However, some cloudiness will not affect the accuracy of the test.
CHEMICAL COMPOSITION ....................................................................................... 5
Test procedure.................................................................................................. 14
Health & Safety ............................................................................................... 15
• Nitrogen (NO3) test
Use the pipette to transfer 2.5 ml of the clear general soil extract to a clean test
tube. [Pay attention not to transfer any soil. To avoid agitation of the soil, squeeze
the bulb of the pipette before inserting it into the soil extract solution.] Add the
content of one packet of HI3896-N reagent. Replace the cap and shake vigorously
for 30 seconds to dissolve the reagent. Allow the tube to stand for 30 seconds.
Match the pink color with the NO3 color-card, and note the NO3.
• Phosphorus (P2O5) test
Use the pipette to transfer 2.5 ml of the clear general soil extract to a clean test
tube. [Pay attention not to transfer any soil. To avoid agitation of the soil, squeeze
the bulb of the pipette before inserting it into the soil extract solution.] Add the
content of one packet of HI3896-P reagent. Replace the cap and shake vigorously
for 30 seconds to dissolve the reagent. Match the blue color with the P2O5 colorcard, and note the P2O5.
• Potassium (K2O) test
Use the pipette to add 0.5 ml of the clear general soil extract to a clean reaction
tube. [Pay attention not to transfer any soil. To avoid agitation of the soil, squeeze
the bulb of the pipette before inserting it into the soil extract solution.] Fill the tube
to the lower graduation mark (2.5 ml) with the HI3896 Extraction solution. Add
the content of one packet of HI3896-K reagent. Replace the cap and shake
vigorously for 30 seconds to dissolve the reagent. A blue color develops. Read the
TURBIDITY formed on the K2O reading-card as explained in the “Test Procedure”,
and note the K2O.
Note:Note:
Note: prolonged exposure to light may damage the colors of the comparing cards and
Note:Note:
cause them to shift or fade. Please store them out of light when not in use.
Health
& Safety
Contents
2
The chemicals contained in this test kit may be hazardous if improperly handled. Read carefully Health & Safety
Data Sheets before performing the tests. Keep your kit out of reach of children. Store it indoors in a clean, dry location.
Keep away from food, drink and animal feed. Always wash your hands thoroughly after making your tests.
Health and safety data sheets are available on line: www.hannainst.com
240 ml of HI 3896 Extraction solution; 100 ml of HI 3896 pH indicator reagent; 75 powder packets (25 each for N,
P and K); 3 pipettes (1 ml); 5 test tubes; 1 tube-stand; 1 spoon; 1 brush; 4 color cards; 1 graduated card; 1
handbook.
15
Test Procedure
4) Depth of extraction:
General: dig and discard the 5 cm (2") of topsoil
For lawns: take the sample at a depth of 5 to 15 cm (from 2" to 6").
For other plants (flowers, vegetables, shrubs): from 20 to 40 cm of depth (8" to 16")
For trees: Samples from 20 to 60 cm of depth (8" to 24'’).
5) Mix all the samples together to obtain a homogeneous mixture of soil.
6) From this mixture, take the quantity of dried soil that you need for the analysis,
discarding stones and vegetable residues.
1) Reading the color-card
– The pH, phosphorus (P2O5), and nitrogen (NO3) tests are colorimetric tests. During
the test a color is developed which corresponds with the fertility of the soil for e.g.
P2O5. To read the fertility, the color developed has to be compared with a colorcard.
To match the color, hold the tube with the test solution approximately 2 cm away
from the color-card. Stand with the light source behind the card and read: Trace,
Low, Medium or High. If the color of the test tube falls between two standard
colors, e.g. between Medium and High Report the test result as Medium-High.
Eight different readings are possible, Trace, Trace-Low, Low, Low-Medium, Medium,
Medium-High, High, and very-High.
– The potassium (K2O) test is a turbidimetric test. If potassium is present, turbidity
is formed. A blue color will also develop to help reading the test result.
To read the test result, hold the tube against the reading-card over the reading
area. Stand with the light source behind your back. Start at Trace, looking through
the tube, and go to Low, Medium or High until you just can see the white line in
the middle of the reading area. Report the reading only in Trace, Low, Medium or
High.
SOIL AND PLANT LIFE
Fig. 1. Fig. 1.
Fig. 1. Stratography of a
Fig. 1. Fig. 1.
natural soil (left) and of a
cultivated soil (right)
(L.Giardini)
Soil is very important for the plants. It is not merely a support system, but a complex world
from which the roots obtain water and other required elements. In addition, soil is
inhabited by small animals, insects, microorganisms (e.g. fungi and bacteria) which all
influence the plant life in one way or another.
One can talk about a soil evolution, that is, change in its characteristics based upon
climate, presence of animals and plants as well as man’s action. Therefore, a natural soil,
in which evolution is slow, is very different from a cultivated one.
Soil is composed of solids (minerals and organic matters), liquids (water and dissolved
substances), gases (mostly oxygen and carbon dioxide) and contains living organisms. All
these elements provide its physical and chemical properties.
Managing the soil properly is necessary in order to preserve its fertility, obtain better yield
and respect the environment. Testing the soil on the other hand is a must in order to
manage it properly.
14
2) Performing the tests
– pH test
Fill a reaction tube up to the lower graduation mark (2.5 ml) with the HI 3896 pH
indicator reagent (use the graduated card for the measure). Use the small spoon to
add six measures of soil sample. Replace the cap and shake gently for one minute.
Allow the tube to stand for 5 minutes (use the tube-stand). Match the color with
the pH color-card, and note the pH value.
– Nitrogen (N), Phosphorus (P), Potassium (K)
• General Extraction procedure [for the P, N, and K tests]
Fill a reaction tube to the third graduation mark (7.5 ml) with the HI3896
Extraction solution. Use the small spoon to add the following: nine measures of soil
sample, in case of field soil testing; six measures of soil sample, in case of garden
soil testing.
Replace the cap and shake gently for one minute.
3
PHYSICAL STRUCTURE
Tab. 1. Particles
classification according to
“International Society of
Soil Science” (ISSS)
Fig. 2. Types of soil in
relation to the texture
The physical structure of the soil depends on the dimension of the particles of its make up
(Tab. 1). In addition, the particles also differ based on their shape and volumic mass (mass
per unit of volume)
DIAMETER OF THE PARTICLES (mm)CLASSIFICATION
> 2stony texture
2 - 0.2coarse sand
0.2 - 0.02fine sand
0.02 - 0.002silt
< 0.002clay
Soil is divided into many classes of texture, according to the percentage of the basic
particles (clay, sand and silt). If, for example, we have a soil with 37% clay, 38% sand
and 25% silt, the soil is classified as “clay loam” (Fig. 2).
Tab. 7.
CROPSOIL CONTENTADVISED DOSES (kg/ha)
NP2O
Applevery low150120230
low13090150
medium11070120
medium-high905090
high804060
very high702040
Grapevery low15090230
low12070180
medium10060150
medium-high9040120
high803090
very high702060
Peachvery low200120230
low16090150
medium14070120
medium-high1205090
high1004060
very high802040
Pearvery low150120230
low13090150
medium11070120
medium-high905090
high804060
very high702040
5
K2O
(data ESAV)
SOIL ANALYSIS
The soil analysis is very useful, in order to plan fertilization and to know the residues of
fertilizers in relation to the crop, tillage and climate. An analysis can highlight shortages
and help the understanding of the causes of an abnormal growth.
Testing the soil during the crop cycle and comparing the results with the plant growth can
be an useful experiment for the next cultivation.
Sampling
1) Extracting Soil Sample
– With a large field, take 1 or 2 samples per 1000 m2 (0.25 acre) of homogeneous
areas.
– Even for smaller areas, 2 samples are recommended (the more the samples, the
better the end-results, because the sample is more representative)
– For a small garden or plot, 1 sample is sufficient
Among different types of soil, the loam soil is considered as being suitable for crop
growth. However, other types of soil, with a rational management, can also provide
positive results.
The soil texture is the cause of important aspects such as porosity, tenacity, adhesivity
2) Avoid extracting samples from soil presenting obvious anomalies
3) Sample quantity:
Take the same quantity of soil for each sample. For example, use bags with similar
dimensions (1 bag per sample)
and plasticity.
4
13
Tab. 7.
CROPSOIL CONTENTADVISED DOSES (kg/ha)
NP2O
Asparagusvery low160120180
low120100150
medium10070130
medium-high9050110
high804090
very high702080
Barleyvery low140130170
low11090120
medium907080
medium-high805060
high704050
very high603040
Corn silagevery low340200230
low300150150
medium280120120
medium-high2609090
high2406060
very high2204046
Maizevery low300200230
low270150150
medium240120120
medium-high2309090
high2106060
very high2004040
Soybeanvery low0150220
low0130170
medium0100130
medium-high080100
high06080
very high04060
Sugar beetvery low160150230
low120130180
medium100100150
medium-high9080120
high806090
very high704060
Tomatovery low150250250
low130180200
medium110150150
medium-high90120120
high809090
very high706060
Wheatvery low180150170
low160100120
medium1508080
medium-high1406060
high1305050
very high1204040
5
K2O
CHEMICAL
COMPOSITION
pH
Fig. 3. Types of soil
according to the pH value
Porosity is important for the exchange of gases and liquids. Micro-porosity (porous < 2 10 µm) permits water to be retained while macro-porosity (porous > 10 µm) contributes to a fast circulation of air and water.
Plants therefore are in need of a correct relationship between micro and macro porosity.
Clay soils have a greater micro-porosity than sandy soils and hence hold more water and
remain wet for a longer period.
Because of the greater tenacity and adhesivity of clay soils, they are called heavy while
sandy soils are referred to as light.
Organic matter, caused by animal and vegetable residues, is another important constituent
of the solid part of the soil. Organic matter has a positive effect on the soil fertility by
adding nutrients, stabilizing the pH reaction and permitting a good retainment of water.
Organic matter is also important for the activity of microorganisms and, in general,
contributes towards prevention of soil erosion.
The colloidal portion, composed of micro-particles (1-100 µm), is important for holding
nutrients. Since most of these particles have a negative charge, the colloidal portion has a
particularly large capacity to retain cations (NH
+
, K+, Na+, Ca++, Mg++, etc.). The CEC
4
(Cation Exchange Capacity) is higher in soils rich with clay and organic matter than in
sandy soils.
The chemical composition of soil includes pH and chemical elements. Their analysis is
necessary for better management of fertilization, tillage and in order to choose the most
suitable plants for best results.
By using the HANNA Soiltest, it is possible to measure pH and the most important
elements for plant growth, that is, nitrogen (N), phosphorus (P) and potassium (K).
pH is the measure of the hydrogen ion concentration [H+]. A soil can be acid, neutral or
alkaline, according to its pH value.
Fig. 3 shows the relationship between the scale of pH and kind of soil. The pH range from
5.5 to 7.5 include the most of plants; but some species prefer acid or alkaline soils.
Nevertheless, every plant need a particular range of pH, in which can better express its
potentiality of growth.
pH strongly influences the availability of nutrients and the presence of microorganisms
and plants in the soil.
12
5
Fig. 4. Solubility of the
elements according to
varying pH values
For example, fungi prefer acidic conditions whereas most bacteria, especially those putting nutrients at the plants’ disposition, have a preference for moderately acidic or slightly
alkaline soils. In fact, in strongly acidic conditions, nitrogen fixing and the mineralization
of vegetable residual is reduced.
Plants absorb the nutrients dissolved in the soil water and the nutrient solubility depends
largely on the pH value. Hence, the availability of elements is different at different pH
levels (Fig. 4).
Each plant needs elements in different quantities and this is the reason why each plant
requires a particular range of pH to optimize its growth.
For example, iron, copper and manganese are not soluble in an alkaline environment. This
means that plants needing these elements should theoretically be in an acidic type of soil.
Nitrogen, phosphorus, potassium and sulfur, on the other hand, are readily available in a
pH range close to neutrality.
The relationship between dosages of fertilizer elements and their presence in the soil is
shown in Tab. 7. As above, the quantities reported are only indicative. Chemical
analysis can be used as a basis for the evaluation, however other factors connected with
the production also need to be considered.
Tab. 7. Relation between
dosages of fertilizer
Furthermore, abnormal pH values, increase the concentration of toxic elements for plants.
For example, in acid conditions, there can be an excess of aluminum ions in such quantities
elements and their presence
in the soil
that the plant can not tolerate. Negative effects on chemical and physical structure are
also present when pH values are too far from neutral conditions (break up of aggregates,
a less permeable and more compact soil).
6
CROPSOIL CONTENTADVISED DOSES (kg/ha)
NP2O
Alfalfavery low0150230
low0130150
medium0100120
medium-high08090
high06060
very high04040
5
K2O
11
Tab.5. Composition of
manure
Top dressing
Tab.6. Experimental
average quantity of
elements absorbed based on
crop yield
It is important to note that whereas an insufficient dose of nutrients decreases the potential
crop production, an excess can have a negative effect on the physiology of the plants and
the crop quality. In addition, too much fertilization can be unnecessarily costly as well as
being harmful to the environment.
Before sowing or transferring plants, use a slow-acting fertilizer to enrich the soil for long
term. This is particularly important for Nitrogen which unlike Phosphorus and Potassium
tends to become less present over time. Compound fertilizers which contain nitrogen
(preferred in ammonium form), phosphorus and potassium can also be used.
Adding organic substances (such as manure and compost) help to increase the soil fertility
(Tab. 5).
ELEMENTQUANTITY (%)
N0.4-0.6
P2O
5
0.2-0.3
K2O0.6-0.8
CaO0.5-0.6
MgO0.15-0.25
SO
3
0.1-0.2
If possible, add the fertilizer more than once. In case of lack of Nitrogen, use fertilizers
containing Nitrate due to their faster absorption by the plants. It is important to add the
necessary elements at particular phases in the plant’s life cycle (for example, before
sprouting or wheat raising).
Do not give nitrate to crops such as lettuce (in which the product is the vegetable part) at
the end of the plant cycle, in order to avoid their accumulation in the leaves (nitrate is
carcinogenic).
Tab. 6 below shows average quantity of element absorbed by the principal crops based on
their yield (note that the relationship between absorption and fertilization is not exact).
Management of the
Soil in Relation with
the pH Value
Tab.2. Quantity (q/ha) of
pure compound necessary to
increase 1 unit of pH
Tab.3. Quantities provide
the same result as 100 Kg
of gypsum
Once the pH value is known, it is advisable to choose crops that are indicated for this range
(e.g. in an acid soil, cultivate rice, potato, strawberry).
Add fertilizers that at the same time do not increase acidity (for example urea, calcium
nitrate, ammonium nitrate and superphosphate) or lower alkalinity (e.g. ammonium
sulfate).
It is recommended that a cost evaluation is made prior to commencement of the modification of the soil pH. Corrective substances can be added in order to modify the soil pH,
however, the effects are generally slow and not persistent. For example, by adding lime,
the effects in clay soil can last for as long as 10 years, but only 2-3 years in a sandy soil.
For an acid soil, we can use substances such as lime, dolomitic, limestone and marl,
according to the nature of the soil (Tab. 2).
SOIL AMELIORANTSCLAY SOILSILTY SOILSANDY SOIL
CaO30-5020-3010-20
Ca(OH)
2
CaMg(CO3)
Ca CO
3
2
39-6626-3913-26
49-8233-4916-33
54-9036-5418-36
High pH levels can depend on different elements, hence, there are different methods
for its correction.
– Soils rich with limestone:
Add organic matter (this is due to the fact that non-organic ameliorants such as
sulfur and sulfuric acid might not make economic sense due to the large quantities
needed).
– Alkaline-saline soils:
Alkalinity is due to the presence of salts (in particular a high concentration of
sodium can be harmful).
Irrigation washes away salts hence an appropriate use of irrigation can provide positive
results (drop-irrigation being the most recommended).
If alkalinity is caused by sodium, it is recommended to add substances such as gypsum
(calcium sulfate), sulfur or other sulfuric compounds (Tab. 3). Also in this case, a cost
evaluation is necessary.
The three elements that are most needed by plants are nitrogen (N), phosphorus (P) and
potassium (K). This is the reason why they are called macronutrients and should be given
to the plants. Other elements, the so-called microelements are generally present in
sufficient quantities in the soil and the plants need them in smaller doses.
Nitrogen is an indispensable element for the plant’s life and is a key factor in fertilization.
It is present in proteins, vitamins, hormones, chlorophyll, etc. Nitrogen allows the development of the vegetative activity of the plant, in particular, causes a lengthening of trunks
and sprouts and increases the production of foliage and fruits (even though the quality
depends by other elements). An excess of Nitrogen weakens the plants’ structure creating
an unbalanced relationship between the green parts and the wooden parts. In addition, the
plant becomes less resistant to diseases.
The nitrogen adsorbed by the plants derives from the mineralization of organic matter and
the application of fertilizers, but legumes (soybean, pea, clover, alfalfa, etc.) are able to
take nitrogen by a symbiotic association with Rhizobium bacteria.
The fact that nitrate (the nitrogen chemical compound that the plants absorb mostly) is not
durable in the soil and the large amount required for crop production, make it necessary to
add this element, avoiding excesses.
Phosphorus is an important element in the composition of DNA and RNA, the regulators
of the energetic exchange (ATP, ADP), as well as the reserve substances in seeds and bulbs.
It contributes to the formation of buds, roots and blooming as well as lignification. A lack
of phosphorus results in: stifling of plant, slow growth, a reduction of production, smaller
fruits and a lower expansion of the roots.
Most of the Phosphorus present in the soil is not available for plants and its release in the
soil solution from which it is taken, is very slow.
Therefore, in order to avoid an impoverishment of the soil, and to give to the plants the
appropriate quantity, a rational fertilization is needed.
Even if potassium is not a constituent of important compounds, it plays a remarkable role
in many physiological activities like the control of the cellular turgor and the accumulation
of carbohydrates. In addition, it increases the size of fruits, their flavor as well as yielding
a positive effect on the color and fragrance of flowers. Potassium also makes plants more
resistant to diseases.
Generally speaking, potassium is normally retained by the soil and the losses are caused
by plant absorption or erosion. In sandy soils however the level may be inadequate.
The quantity of substances to add to the soil, depends not only on the chemical state of the
soil but also on factors such as local climate, the physical structure, previous and present
cultivation, microbiological activities etc. Hence, only after a technical and economical
evaluation, it is possible choose the proper quantity of fertilizer to add.
8
9
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