Growing legumes in orchard alleys as an internal nitrogen source
Granatstein, D.;J.R. Davenport;E. Kirby. 2017.
Abstract
The drive alley in modern apple (Malus X domestica Bork.) orchards often
receives enough light to grow plants other than the typical perennial grass cover. By
planting leguminous species in this area, it is possible to produce a portion of the nitrogen
needs of the orchard by mowing the vegetation and blowing it onto the tree row where it
mineralizes and releases available N over the tree roots. Four perennial legume species
[alfalfa (Medicago sativa L.), ladino white clover (Trifolium repens L.), birdsfoot trefoil
(Lotus corniculatus L.), kura clover (Trifolium ambiguum L.)] were compared with the
resident grass cover crop in a mature apple orchard. All legumes were direct-seeded into
the alley to avoid any soil disturbance and were successfully established. Legume biomass
and tissue N were monitored, along with biweekly monitoring of tree row soil nitrogen
with both soil sampling and ion exchange resins using Plant Root Simulator® probes.
Four mowings of alfalfa contained 43 kg total N/ha that was added to the tree row
during the second season (2009), with a dry matter C:N of 10.8. Economically, legume
nitrogen appears to be less expensive than other sources of organic N and may be cost
competitive with synthetic fertilizer N when prices are high.
Key Words
apple, alfalfa, clover, trefoil, direct seeding, ion exchange probes
