Radiation use efficiency and biomass partitioning of lucerne ( Medicago sativa) in a temperate climate

• Published in: European journal of agronomy Vol. 25; no. 4; pp. 319 - 327
• Main Authors: Brown, Hamish E., Moot, Derrick J., Teixeira, Edmar I.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.11.2006; Elsevier Science
• Subjects: Agronomy. Soil science and plant productions; air temperature; alfalfa; Biological and medical sciences; Biomass partitioning; climatic factors; crown; dry matter partitioning; forage crops; Fundamental and applied biological sciences. Psychology; irrigation; Lucerne; Medicago sativa; Radiation use efficiency; regrowth; roots; seasonal variation; shoots; solar radiation; temperate zones; Temperature; New Zealand; Radiation use efficiency; Temperature; Biomass partitioning; Lucerne; Medicago sativa; Partition; Biomass; Leguminosae; Dicotyledones; Angiospermae; Temperate climate; Spermatophyta; Fodder crop
• DOI: 10.1016/j.eja.2006.06.008
• ISSN: 1161-0301

This research quantifies the influence of seasonal variations in solar radiation, temperature and biomass partitioning on lucerne production in a temperate climate. Above ground biomass (shoot) production of fully irrigated ‘Kaituna’ lucerne was measured in the field over 5 years and 33 regrowth cycles in Canterbury, New Zealand. Shoot production increased linearly ( R 2 of 0.93 ± 0.07) with intercepted total radiation within each regrowth cycle but radiation use efficiency (RUE shoot, in g DM/MJ total radiation) ranged from 0.29 to 1.09 g DM/MJ. Covariate analysis showed season and temperature both influenced RUE shoot with temperature adjusted RU E shoot ( RU E shoot * ) decreasing from 1.01 g DM/MJ in September to 0.77 g DM/MJ between October and February, decreasing again to 0.47 g DM/MJ in March and April before increasing back to 0.99 g DM/MJ in May. A second fully irrigated experiment with lucerne plants grown in plastic columns under near field conditions investigated the seasonality of biomass partitioning between shoots and perennial biomass (roots and crowns). The proportion of total biomass partitioned to shoots ( P shoot) was 0.90 in September, ∼0.67 from October to February but only 0.35 in March and could be related to photoperiod. These P shoot values were closely correlated with RU E shoot * showing seasonal changes in RUE shoot were partly caused by changes in biomass partitioning. Field data for RUE shoot were divided by P shoot to estimate the RUE for total biomass production (RUE total). The RUE total increased linearly from 0.60 to 1.60 g DM/MJ as mean air temperatures increased from 6 to 18 °C. These results quantified the effects of solar radiation and mean temperature on total lucerne biomass production and its seasonal partitioning between shoots and perennial biomass. The influence of regrowth duration on this partitioning was also investigated.