Stanisław Rolbiecki*, Roman Rolbiecki*, Barbara Jagosz**, Wiesław Ptach***, Piotr Stachowski****, Maciej Kazula*****
*University of Science and Technology, Bydgoszcz, Poland; **University of Agriculture in Krakow, Poland; ***Warsaw University of Life Sciences, Poland; ****Poznan University of Life Sciences, Poland; *****University of Minnesota, USA
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Asparagus (Asparagus officinalis L.), due to their deep and well-developed root system, are relatively resistant to the water deficits in the soil. On the other hand, asparagus plants grown on the light soil positively respond to the irriga-tion treatments. The aim of the present study was the determination of water needs of asparagus plants in the different agro-climatic regions of Poland. The calculations of asparagus water requirements, considered as the crop evapotranspi-ration, based on the precipitation measurements collected during the thirty-year period from 1981 to 2010. The estima-tions were achieved for the months, including July and August, critical in terms of the amount of water available to the plants. The calculation of asparagus water needs using the plant coefficients was performed. The plant coefficients for asparagus cultivated in the Polish field conditions were determined by Rolbiecki. Published by him calculations based on the long-term observations of the irrigated asparagus crop. The reference evapotranspiration was calculated according to Grabarczyk’s method. The Grabarczyk’s formula was chosen because it allowed estimating the reference evapotranspira-tion in a simplified way, i.e. based only on the precipitation measurements. The rainfall deficit was considered using the Ostromęcki’s method. The precipitation deficit in the period from July 1 to August 31 was calculated as the difference between the water needs of asparagus, expressed as the crop evapotranspiration for a considered month and the total precipitation in this month. The water needs of asparagus plants were determined for five agro-climatic regions of Poland with the representative meteorological stations located in Olsztyn, Bydgoszcz, Warszawa, Wroclaw and Krakow. The highest variability of asparagus water requirements was calculated in the central-north-west (C-N-W) region of the Po-land. The variation coefficient in July and August was 7.7% and 7.6%, respectively. In contrast, the lowest variability of asparagus water needs were find in the south-west (S-W) and south-east (S-E) region of Poland. The highest water needs of asparagus plants, on average 228 mm, in the period from July to August were noted in the C-N-W and central-east (C-E) region of Poland. The highest rainfall deficit, calculated for medium dry years, average dry years and very dry years, was 91 mm and 89 mm, 157 mm and 166 mm, and 209 mm and 245 mm, respectively, in the C-N-W and C-E region, re-spectively. Generally, higher precipitation deficiencies were noted in August than in July.

Asparagus officinalis L., crop evapotranspiration, rainfall deficiencies, reference evapotranspiration, water requirements

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