Tuber yield and leaf mineral composition of Jerusalem artichoke (Helianthus tuberosus L.) grown under different cropping practices

Abstract

Jerusalem artichoke is commonly grown for its edible tubers, livestock feed and as an ornamental. The possibility of growing Jerusalem artichoke for energetic purposes has aroused scientific interest in this species. Despite several studies that have already been done in the last few decades, many aspects of the cropping practice are still relatively unknown. During the growing seasons of 2004-2006 field trials were carried out in NE Portugal. In the experimental period different cropping conditions were imposed, regarding planting density, N fertilization and propagation method. The crop was irrigated in 2004 and 2005 and grown in rain-fed conditions in 2006. The planting densities were 7 plants/square m in 2004, 2, 3 and 4 plants/square m in 2005 and 2 and 4 plants/square m in 2006. Botanical-seed was used in 2005 and seedtubers in all the three years. In 2005, 0 and 100 kg N/ha was combined in a factorial design with the planting densities. The maximum tuber dry matter yield was 18.4 Mg/ha (65.6 Mg/ha, fresh weight basis) and it was recorded in 2005 in the plots where 100 kg N/ha, 2 plants/square m and seed-tubers were combined. The best planting density was 2 plants/square m in irrigated (2005) and rain-fed (2006) conditions. Nitrogen significantly increased tuber yield in 2005 only when seed-tubers were used. Averaged across N fertilization rates and planting densities mean tuber dry matter yields were 12.8 and 6.9 Mg/ha for seed-tuber and botanical-seed, respectively. Leaf mineral composition was little affected by cropping practices. The "Bragança" clone showed high tuber yield potential, although the mean weight of the individual tubers was low which could make mechanization of the harvest difficult. The poor results achieved with botanicalseed argue against its use as an alternative to the seed-tubers.