Total nonstructural carbohydrates (TNC) stored in roots are thought to
be an important energy source for growth following herbage removal in
many forage legumes. This study was conducted to determine if root TN
C levels fluctuate during harvest and regrowth cycles of annual lesped
eza (Kummerowia spp.). Annual lespedeza management treatments consiste
d of harvesting at a 6- or 12-cm stubble height at the end of July and
a nonharvested control. Seeding-year 'Nitro' alfalfa (Medicago sativa
L.) and 'Norcen' birdsfoot trefoil (Lotus corniculatus L.) were inclu
ded for comparison. Alfalfa was harvested four times at early bloom an
d birdsfoot trefoil three times at early bloom. Alfalfa exhibited a cy
clic pattern of TNC utilization and storage in response to herbage rem
oval and regrowth, respectively. Seedling alfalfa accumulated >150 g k
g(-1) TNC in the roots by 10 June, and >450 g kg(-1) by first harvest.
Seedling birdsfoot trefoil maintained <70 g kg(-1) TNC in the roots t
hrough mid-September and did not exhibit as much TNC cycling as did al
falfa. Annual lespedeza averaged approximate to 20 g kg(-1) TNC in the
roots prior to harvest and maintained <40 g kg(-1) throughout the gro
wing season. Harvesting annual lespedeza at 6 cm decreased root TNC le
vels for approximate to 5 wk compared with harvesting at 12 cm and the
nonharvested controls; however, the total amount of reduction was sma
ll. Root TNC Levels decreased by 6.1 g kg(-1) with cutting at 6 cm. As
annual lespedeza maintains relatively small amounts of root TNC, leav
ing residual leaf area at harvest may be important for regrowth.