The Application of the Cluster Analysis in Recognizing Weather Patterns Conducive to Large and Small Crops of Mid-late Onion Cultivars (Allium cepa L.) in Poland
AbstractThis study uses 40 years valuable of data (1966-2005) obtained by the Polish Research Centre for Cultivar Testing and the Polish Institute of Meteorology and Water Management to recognize weather conditions conducive to large and small crops of onion (Allium cepa L.), more specifically-its mid-late cultivars cultivated in Poland. We found three clusters of agrometeorological conditions, determining different sizes of onion crops. Cluster no. 1 included observations which were characterized by large onion crops (45.9 t ha-1 for the total crop and 44.7 t ha-1 for the commercial crop) and cluster no. 3 was characterized by a small crop (respectively 26.2 and 24.8 t ha-1). Large crops were favored by the following weather patterns: during sowing-end of emergence, above-average sunshine duration (8.1 h) and above-average air temperature (13.0oC); in end of emergence-beginning of leaf bending-average sunshine duration (7.4 h), average soil temperature (18.7oC) and air temperature (16.8oC) and above-average rainfall, described by the coefficient of rainfall (2.8 mm); in beginning of leaf bending-harvest-soil temperature (17.3oC) and air temperature (16.0oC) lower than a long-term average. Temperatures of soil and air that are higher than a long-term average, especially in the period sowing-end of emergence, with a parallel stable level of rainfall, may cause a reduction in onion crops in Poland.
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