Yields and Bioactive Substances of Selected European Asparagus Cultivars Grown for Green Spear Production as Influenced by of Post-Harvest Drip Irrigation on Sandy Soil in Central Poland

The objective of this study was to verify the response of 10 European asparagus cultivars grown for green spear production using post-harvest drip irrigation. Irrigation, used to compensate for periodic deficiencies in precipitation, allows for high and good quality crops for many species, and also keeps soil in good condition. The field experiment was carried out in 2006–2008 on a very light sandy soil in central Poland. Irrigation treatments were applied using the tensiometer indications. Water needs of asparagus were calculated on the base of reference evapotranspiration and crop coefficients. The following evaluations were made: height, diameter and number of summer stalks, as well marketable yield, weight and number of green spears. Drip irrigation applied for two years in the post-harvest period, had a positive effect on all studied traits, both summer stalks and green spears in 2007–2008. A significant increase in the height, number and diameter of summer stalks, as well as an increase in the marketable yield, weight and number of green spears was observed for most of the cultivars. Both factors, the irrigation used and the asparagus cultivars significantly modified the antioxidant content in asparagus spears. The Rapsody cultivar accumulated significantly more, and the Grolim cultivar significantly less, total polyphenols in asparagus spears at unirrigated plots. An inverse relationship was obtained in the Grolim cultivar with respect to the content of vitamin C, which accumulated the most of it under the irrigation conditions. The Ramada cultivar from irrigated plots contained significantly the highest amount of total carotenoids. In turn, the Cipres and Grolim cultivars from irrigated plots were characterized by the highest antioxidant activity.