Hanna Instruments hi 38050 User Manual
5
Note: Legumes (soybean, pea, clover, alfalfa, etc.) are able to take atmospheric nitrogen by a
symbiotic association with Rhizobium bacteria.
A very important source of nitrogen available for plants is the decomposition (miner-
alization and nitrification) of organic matter, the so called "turnover". However only
part of the organic matter decomposes during the crop growth season. The decomposi-
tion rate depends strongly on the local climate, the physical structure and microbiological
activities in the soil, thus it varies from year to year. Other important sources of
nitrogen are fertilization and irrigation when nitrogen compounds are present in the
irrigation water. Even rain and snow can contribute, dissolving the nitrate, nitrite and
ammonia normally present in the atmosphere and carrying them to the soil.
Available nitrate-nitrogen can be lost from the soil in several ways. The most
significant ones are leaching, which occurs during heavy rainfall or where excessive
irrigation is used. Another is assimilation by crops. It is estimated that in natural soils
(woods, forests) about 80% of the absorbed nitrogen is replenished when trees shed
their leaves. In case of crops, the assimilated nitrogen is lost from soil during
harvesting.
alization and nitrification) of organic matter, the so called "turnover". However only
part of the organic matter decomposes during the crop growth season. The decomposi-
tion rate depends strongly on the local climate, the physical structure and microbiological
activities in the soil, thus it varies from year to year. Other important sources of
nitrogen are fertilization and irrigation when nitrogen compounds are present in the
irrigation water. Even rain and snow can contribute, dissolving the nitrate, nitrite and
ammonia normally present in the atmosphere and carrying them to the soil.
Available nitrate-nitrogen can be lost from the soil in several ways. The most
significant ones are leaching, which occurs during heavy rainfall or where excessive
irrigation is used. Another is assimilation by crops. It is estimated that in natural soils
(woods, forests) about 80% of the absorbed nitrogen is replenished when trees shed
their leaves. In case of crops, the assimilated nitrogen is lost from soil during
harvesting.
Testing the soil during the crop cycle is a useful tool for next cultivation, 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 in understanding the causes
of an abnormal growth.
The Hanna nitrate-nitrogen test can be performed the whole year round, but testing is
particularly recommended during Spring and Late-spring, when rainfall and tempera-
ture-related bursts of microbiological activity often have great influence on the
availability of nitrate-nitrogen.
plan fertilization and to know the residues of fertilizers in relation to the crop, tillage
and climate. An analysis can highlight shortages and help in understanding the causes
of an abnormal growth.
The Hanna nitrate-nitrogen test can be performed the whole year round, but testing is
particularly recommended during Spring and Late-spring, when rainfall and tempera-
ture-related bursts of microbiological activity often have great influence on the
availability of nitrate-nitrogen.
1) Soil Sample Extraction
– Within a large homogeneous area, take 1 or 2 samples per 1000 m
2
(0.25 acre).
– Even for smaller areas, 2 samples are recommended (the more samples, the better
the end-results, because the end sample is more representative).
– For a small garden or plot, 1 sample is sufficient.
2) Avoid extracting samples from soil presenting obvious anomalies and from border
areas (near ditches and roads).
3) Sample quantity:
Take the same quantity of soil for each sample. For example, use bags with similar
dimensions (1 bag per sample).
dimensions (1 bag per sample).
4) Depth of extraction:
Sample the top 30 cm (12”) of soil.
5) Mix all the samples together to obtain a homogeneous mixture of soil, discarding
stones and vegetable residues.
WHY AND WHEN TO
TEST FOR NITROGEN
TEST FOR NITROGEN
HOW TO COLLECT
SOIL SAMPLES
SOIL SAMPLES
8
CHEMICAL REACTION
Nitrate is reduced to nitrite in the presence of Cadmium. The nitrite thus produced
reacts with the reagent to yield an orange compound. The amount of color developed
is proportional to the concentration of nitrate present in the aqueous sample.
reacts with the reagent to yield an orange compound. The amount of color developed
is proportional to the concentration of nitrate present in the aqueous sample.
SPECIFICATIONS
Range
IW: 0-50 mg/L (ppm) as N-NO
3
-
Soil: 0-60 mg/L (ppm) as N-NO
3
-
Smallest Increment
IW: 1 mg/L (ppm) N-NO
3
-
Soil: 2 mg/L (ppm) N-NO
3
-
Analysis Method
Colorimetric
Sample Size
5 mL (IW)
10 g of soil (Soil)
10 g of soil (Soil)
Number of Tests
100 (IW), 100 (Soil)
Case Dimensions
235x175x115 mm (9.2x6.9x4.5")
235x175x115 mm (9.2x6.9x4.5")
235x175x115 mm (9.2x6.9x4.5")
Shipping Weight
1026 g (36.2 oz.)
Note: IW is Irrigation Water
CONVERSION
FACTORS
FACTORS
WARNING
1 kg
2.205 lb.
1 ha
2.471 acre
1 kg/ha
0.891 lb./acre
1 ppm (soil)
1 mg/kg
1 ppm (irrigation water)
1 mg/L
1 ppm N
4.43 ppm NO
3
This test gives accurate results for most soil types, nevertheless, some local circum-
stances can cause erroneous readings. Therefore use this test always with caution.
Whereas an insufficient dose of nutrients decreases the potential crop production, an
excess can have a detrimental effect on the physiology of the plants and the crop
quality. In addition, too much fertilization is unnecessarily costly as well as harmful to
the environment. Hence, only after a technical and economical evaluation, it is
possible to choose the proper quantity of fertilizer to be added.
stances can cause erroneous readings. Therefore use this test always with caution.
Whereas an insufficient dose of nutrients decreases the potential crop production, an
excess can have a detrimental effect on the physiology of the plants and the crop
quality. In addition, too much fertilization is unnecessarily costly as well as harmful to
the environment. Hence, only after a technical and economical evaluation, it is
possible to choose the proper quantity of fertilizer to be added.