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in Central Poland are approximately equal to 100–300 mm in an average year. The
irrigation water requirement gained exceptionally high rate during very dry periods
since rapid moisture content decline is to be observed, and water resources become
limited at the same time.
Summing up, the values of mean water demand of highly productive crop species
under climatic conditions of Central Poland are as follows:
– 300–400 mm for crops of short growing period (by the end of July) and small
water demand, e.g. cereals, early potatoes
– 400–500 mm for crops of longer growth (by the end of September) and moderate
water demands, e.g. root crops
– 500–600 mm for crops of long growing season (until the end of September) and
high water demands, e.g. fodder crops, vegetables.
With regard to soil moisture retention in the form of readily available soil water
equal to 50–100 mm in light and medium textured soils as well as mean precipitation
equal to 300 mm, the crop water deficits, pointing at net irrigation water requirements,
can be found (Table 5.2).
Table 5.2 Net irrigation
water requirements N in a
growing period in Central
Poland
Crop
Growing period
N (mm)
Rye
April–July
0–50
Winter wheat
April–July
50–100
Oat
April–July
0–50
Early potatoes
April–July
50–100
Late potatoes
April–September
100–150
Grass
April–September
160–210
Yellow lupine
April–July
100–150
Vetch
April–July
200–250
Sugar beet
April–September
150–200
Fodder beet
April–September
200–250
Carrot
May–September
190–240
Maize
April–September
100–150
Alfalfa
April–September
80–130
Early vegetables
May–July
50–200
Late vegetables
May–September
200–300
Berry crops
Varied
170–250
Orchards
Varied
200–400
Permanent grassland
April–September
150–200