Growth, yield, and mineral content of butterhead lettuce (lactuca sativa var. Capitata) grown in nft
2004
Conversa, G. | Santamaria, P. | Gonnella, M.
To improve greenhouse lettuce yield and quality and avoid enviromental pollution it is necessary to optimize plant nutrition. Plants uptake nutrients at different ratios during the growing period. Therefore, total N, K+, Mg2+, and Ca2+ accumulation and NO3-, NH4+ K+, Mg2+, and Ca2+ uptake were evaluated during greenhouse growth of two cultivars of butterhead lettuce (‘Mindoro’ and ‘Tibet’) in a discontinous closed loop NFT sstem. Growth rate and water consumption were also measured. In the last 20 days of the growing cycle, lettuce plants produced 70% of the shoot dry weight and 60% of the leaf area obtained in the enitre growing period. From 30 DAT to harvest, the shoot dry matter content decreased from 7.0 to 5.1 g•100 g-1 fw in 'Mindoro', and from 7.0 to 6.0 g•100 g-1 fw in 'Tibet'. From 30 to 50 DAT, both cultivars had increasing content of leaf total N up to 4.3 and 4.6 g•100 g-1 dw in 'Mindoro' and 'Tibet', respectively, when RGR was still high. Thereafter, and up to harvest the total N concentration decreased more markedly in ‘Mindoro’ (14%) than in 'Tibet' (6%) while simultaneous dry biomass production was peaking. Similar variations with time were found for K+, Ca2+, and Mg2+ leaf contents. 'Mindoro' had higher N use efficiency (NUE) than 'Tibet'. Leaf NO3 content was moderate (1,622 mg•kg-1 fw) and 80% of total N was in reduced form. During the whole growing cycle, 5.5 L/plant of water was used with a water use efficiency (WUE) of 12.4 dw g•L-1.
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