Methodological
assumptios in land suitability classifications.
Land suitability is the fitness of a given type of land for a
defined use. The land may be considered in its present condition or
after improvements. The process of land suitability classification
is the appraisal and grouping of specific areas of land in terms of
their suitability for defined uses.
In
the structure of this classification four categories of decreasinig
generalization are recognized:
- Land
Suitability Orders: reflecting kinds of suitability.
- Land
Suitability Classes: reflectirg degrees of suitability within
Orders.
- Land
Suitabílity Subclasses: reflecting kinds of limitation, or main
kinds of improvement measures required, within Classes.
- Land
Suitability Units: reflecting minor differences in required
management within Subclasses.
Land
Suitabilitbility
Orders:
Order "S" : Suitable
Land on which sustained use of the kind under corsideration is
expected to yield benefits which justify the imputs, without
unacceptable risk of damage to land resources.
Order "N" : Not SuItable
Land which has qualities that appear to preclude sustained use of
the kind under consideration.
Land Suitability
Classes.
The classes are numbered consecutively, by arabic numbers, in
sequence of decreasing degrees of suitability within the
Order.Within tre Order Suitable the number of classes is not
specified. There might be only two; fíve should probably be the most
ever used.If three Classes are recognized as can often be
recommended, the following names and definitions may be appropriate:
- Class Sl :
Highly Suitable:
- Class S2 :
Moderately Suitable:
- Class S3 :
Marginally Suitable:
Within the Order Not Suitable, there are normally two Classes:
- Class N1
:Currently Not Suitable
- Class N2
:Permanently Not Suitable
In
the past years, the Institute of Pedology in Perugia (Italy) studied
a great number of natural truffle-bed soils of Tuber magnatum Pico
from hilly areas of the Central Italy and Tuber melanosporum Vitt.
from Central Apennines (Italy).
The
standard methodology has been applied but, in addition to the
examination of the truffle-bed ground, also the nearby soil was
studied to know the initial soil conditions too.
Here it is the
Land Suitability Table to white truffle (T. magnatum) growing in
Umbria (Central Itay).
Tuber magnatum
Pico, land suitability classes
| |
DATA |
S1 |
S2 |
N |
| 1 |
m. of altitude |
< 500 |
500-800 |
>800 |
| 2 |
exposure |
all the
same |
all the
same |
all the same |
| 3 |
slope |
0-40% |
40-60% |
>60% |
| 4 |
skeleton |
<10% |
10-25% |
>25% |
| 5 |
texture |
sand
30-65%
silt 20-40%
clay 15-30% |
sand
10-80%
silt 5-70%
clay 10-40% |
all the
others |
| 6 |
pH |
7.9-8.2 |
7.5-7.8 |
>7.5 |
| 7 |
limestone |
>5% |
trace-5% |
absent |
| 8 |
organic matter |
1-3% |
0.5-1%
3-5% |
<0.5%
>5% |
|