Comparison of asparagus (Asparagus officinalis L.) cultivars and the effect of covering beds

Five hybrid cultivars ('Boonlim', 'Cipres', 'Dariana', 'Franklim' in 'Steline') of white asparagus were tested on 4 locations in Slovenia (Celje, Logarovci, Nova Gorica and Novo mesto). The plantations were 7 years old when some of the raised beds were covered with black PE mulch and the yield was compared to the yield of uncovered beds. The planting space was 2.2 m between rows and 0.33 m between crowns in the row. Each cultivar had 2 covered and 2 uncovered repetitions with 15 plants (11 m2). The yield and number of spears were measured. For 6 days, white spears were divided into 4 groups based on their thickness (4-8 mm; 8-12 mm; 12-16 mm; over 16 mm), counted and weighed in order to determine the proportion and quality of marketable yield. 'Steline' (3.44 t/ha) had the lowest average yield and 'Boonlim' (6.78 t/ha), which was the best performing cultivar in Logarovci and Nova Gorica, the best. In Novo mesto there were no significant differences among cultivars and in Celje, earlier cultivars 'Franklim', 'Cipres' and 'Dariana' performed better. 'Franklim' had more spears on average but  the weight of the spears was best with 'Boonlim' (46.24 g) and worst with 'Steline' (32.03 g). The mulch influenced the yield, which was 5.27 t/ha on uncovered beds and 6.25 t/ha on covered ones. It also influenced the average weight of spears, which increased from 38.15 g to 40.88 g. The mulch did not increase either the number of spears or their thickness.