The aim of the study was to compare the water requirements and the precipitation deficiencies during cultivation of asparagus in the period from June to August in the regions of Bydgoszcz and Wroclaw. The water needs were calculated using the plant coefficient. The reference evapotranspiration was measured by Grabarczyk’s method (1976). The coefficients kc, determined for the Polish conditions by Rolbiecki (2013), were used to estimate the water requirements considered as the crop evapotranspiration. In the studied period (from June to August, 1996-2015), higher water requirements of asparagus were noted in the Wroclaw region (366.1 mm) than in the Bydgoszcz region (288.5 mm). The monthly water needs in June, July and August were 69.8 mm, 128.8 mm and 167.5 mm, respectively, in the Wroclaw region, and 55.5 mm, 98.5 mm and 134.5 mm, respectively, in the Bydgoszcz region. In July, the tendency to increase the water requirements in both observed regions was noted. The monthly crop evapotranspiration in July rose in each decade by 12.3 mm in the Bydgoszcz region and by 21.2 mm in the Wroclaw region. In the 20-year study, the rainfall deficit in June and July during 11-13 years was noted. In August, the precipitation deficiencies were observed during 16 years in the Bydgoszcz region and during 19 years in the Wroclaw region. A higher rainfall deficit during the 20-year period under study was reported in the Wroclaw region (128.5 mm) than in the Bydgoszcz region (87.0 mm). In August, the highest monthly precipitation deficiencies of 100.3 mm (Wroclaw region) and 70.3 mm (Bydgoszcz region) were noted.
Wyniki badań lizymetrycznych wykonywanych w warunkach wilgotności gleby zbliżonej do polowej pojemności wodnej dowodzą, że na kształtowanie się ewapotranspiracji maksymalnej łąki nawożonej NPK w ilości 270, 540, 660 kg·ha-¹, pastwiska (660 kg NPK·ha-¹) i systematycznie ciętej runi (270 kg NPK·ha-¹) w sezonach wegetacyjnych, pokosach, odrostach i dekadach, wyrażone wartością dekadowych współczynników roślinnych kc obliczonych na podstawie wzoru Penmana w modyfikacji francuskiej wpływ ma maksymalny plon aktualny qmax. Podane w pracy zależności kc(qmax) dla badanych użytków zielonych mogą być wykorzystane do oceny dekadowych wartości współczynników kc w pokosach i odrostach na podstawie zmierzonego, obliczonego lub szacowanego maksymalnego plonu aktualnego w podanych przedziałach wartości qmax. Zależności te są niezbędne do obliczeń dekadowych wartości ewapotranspiracji maksymalnej użytków zielonych na podstawie wzoru Penmana w modyfikacji francuskiej oraz dekadowych wartości ewapotranspiracji rzeczywistej na podstawie ciśnienia ssącego gleby F i ewapotranspiracji maksymalnej.
EN
Results of lysimetric studies carried out in soil moisture conditions close to the field water capacity proved that the influence of the over-ground grass mass on the formation of the maximum evapotranspiration of meadows fertilized at a level of 270, 540, 660 kg NPK·ha-¹ pasture (660 kg NPK·ha-¹) and the greenness growth (270 kg NPK·ha-¹) in the periods of vegetative seasons, swathes, outgrowths and decades, expressed as decade values of plant coefficients kc, calculated further to Penman's equation as modified in France which varied in relation to the size of the actual maximum yield qmax. The relations given in the present study kc(qmax) for meadows, pasture and greenness growth can be used for the evaluation of decade values of kccoefficients in swathes and outgrowths on the basis of measured, calculated or assessed maximum actual yield in the intervals of the qmax values given. The above relations are indispensable for the calculations of decade values of the maximum evapotranspiration levels of grasslands further to Penman's equation as modified in France on the basis of soil suction pressure F and maximum evapotranspiration.
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