380
R. Ku´ smierek-Tomaszewska and J. ˙
Zarski
19.1 Introduction
Plant irrigation is a water supply to the soil profile in order to provide or improve the
growth, development and yielding conditions of crop plants. Irrigation is considered
to be an agrotechnical practice and is one of the very first anthropogenic modifications
of the natural environment, originating about 7500 years ago in Mesopotamia.
According to current data published by the International Commission on Irrigation and Drainage [1] and Food and Agriculture Organization of the United Nations
[2], around 300 million hectares are irrigated worldwide, which accounts for approximately 20% of the total of agricultural land. It is estimated that about 40% of the global
food supply comes from irrigated land. The spatial distribution of the irrigated area,
as an essential indicator of water management and food security, is important subject
for statistics and scientific research. Recent studies based on vegetation indices used
in remote sensing measurements [3] show that the global irrigated area is even higher
than that reported in the statistics and possibly amounts to as much as 367 million
hectares.
On the global scale, the main criterion for the advisability of using plant irrigation
is the climatic condition, in particular, the amount and distribution of atmospheric
precipitation. Therefore, irrigation is mainly applied in regularly or periodically arid
climatic zones because it is in these areas where food production would not be
possible without an additional water supply.
It seems different in Poland (in the moderate zone), where irrigation of plants is
basically a contingency procedure, applicable to supplement the periodic shortages
of atmospheric precipitation in relation to the water requirements of plants. In terms
of the average conditions, these shortages result from too low multiannual average
precipitation in relation to the water needs of plants, expressed by mean values of
evapotranspiration or optimal precipitation. It particularly applies to sandy soils with
reduced water retention capacity, situated in the central lowland part of the country. In
selected growing seasons (April–September), or some periods occurring in the middle
of them, these shortages result in temporary rainfall scarcity leading to meteorological
and agricultural droughts. In the moderate, transitional climate of Poland, these
droughts are weather phenomena and are unfavourable for agricultural production,
appearing quite often but irregularly. A great example to illustrate the climate risk
due to this hazard, in the cultivation of cereal crops and winter rape, (which dominate
in the sowings structure), is the occurrence of meteorological drought in the region
of Pomorze and Kujawy from May to June between 1981–2010 (Table 19.1). In
the analysed multi-annual period in particular cities of the region, meteorological
droughts occurred in 7–9 cases, which means a frequency of 23.3–30.0%. This is
entirely consistent with the results of research conducted by Ł˛ ab˛ edzki for central
Poland [4].
Conditions of sufficiently or excessively moisturized soils during some periods of
plant vegetation, or even throughout the whole growing season, occur in Poland with
a similar frequency to droughts. For this reason, among other things, the irrigated area
in Poland covers only about 73 thousand hectares according to official data, including
R. Ku´ smierek-Tomaszewska and J. ˙
Zarski
19.1 Introduction
Plant irrigation is a water supply to the soil profile in order to provide or improve the
growth, development and yielding conditions of crop plants. Irrigation is considered
to be an agrotechnical practice and is one of the very first anthropogenic modifications
of the natural environment, originating about 7500 years ago in Mesopotamia.
According to current data published by the International Commission on Irrigation and Drainage [1] and Food and Agriculture Organization of the United Nations
[2], around 300 million hectares are irrigated worldwide, which accounts for approximately 20% of the total of agricultural land. It is estimated that about 40% of the global
food supply comes from irrigated land. The spatial distribution of the irrigated area,
as an essential indicator of water management and food security, is important subject
for statistics and scientific research. Recent studies based on vegetation indices used
in remote sensing measurements [3] show that the global irrigated area is even higher
than that reported in the statistics and possibly amounts to as much as 367 million
hectares.
On the global scale, the main criterion for the advisability of using plant irrigation
is the climatic condition, in particular, the amount and distribution of atmospheric
precipitation. Therefore, irrigation is mainly applied in regularly or periodically arid
climatic zones because it is in these areas where food production would not be
possible without an additional water supply.
It seems different in Poland (in the moderate zone), where irrigation of plants is
basically a contingency procedure, applicable to supplement the periodic shortages
of atmospheric precipitation in relation to the water requirements of plants. In terms
of the average conditions, these shortages result from too low multiannual average
precipitation in relation to the water needs of plants, expressed by mean values of
evapotranspiration or optimal precipitation. It particularly applies to sandy soils with
reduced water retention capacity, situated in the central lowland part of the country. In
selected growing seasons (April–September), or some periods occurring in the middle
of them, these shortages result in temporary rainfall scarcity leading to meteorological
and agricultural droughts. In the moderate, transitional climate of Poland, these
droughts are weather phenomena and are unfavourable for agricultural production,
appearing quite often but irregularly. A great example to illustrate the climate risk
due to this hazard, in the cultivation of cereal crops and winter rape, (which dominate
in the sowings structure), is the occurrence of meteorological drought in the region
of Pomorze and Kujawy from May to June between 1981–2010 (Table 19.1). In
the analysed multi-annual period in particular cities of the region, meteorological
droughts occurred in 7–9 cases, which means a frequency of 23.3–30.0%. This is
entirely consistent with the results of research conducted by Ł˛ ab˛ edzki for central
Poland [4].
Conditions of sufficiently or excessively moisturized soils during some periods of
plant vegetation, or even throughout the whole growing season, occur in Poland with
a similar frequency to droughts. For this reason, among other things, the irrigated area
in Poland covers only about 73 thousand hectares according to official data, including