Responses of Kura Clover to Sheep Grazing and Clipping: II. Below‐Ground Morphology, Persistence, and Total Nonstructural Carbohydrates

Abstract

AbstractBelow‐ground morphology and total nonstructural carbohydrate (TNC) reserve patterns may explain the excellent persistence of kura clover (Trifolium ambiguum M. Bieb.). Our objective was to determine the effects of frequent clipping and sheep (Ovis spp.) grazing on the below‐ground morphology, TNC reserves, and persistence of kura clover. Clipping and sheep grazing experiments were initiated on a 5‐yr‐old stand of ‘Rhizo’ kura clover on a Waukegan silt loam (fine‐silty over sandy, mixed, mesic Typic Hapludoll) and conducted for 3 yr. Crowns, rhizomes, and roots comprised about 25, 45, and 30%, respectively, of the total below‐ground mass sampled to a 15‐cm depth, which averaged 6600 kg ha−1. Primary crowns decreased from 95 to 55 m−2 during 2 yr of grazing, whereas secondary crowns produced by rhizomes averaged 1340 m −2 and dominated aerial shoot production. Crown, rhizome, and root TNC concentrations ranged from 87 to 212, 85 to 248, and 114 to 239 g kg −1 DM, respectively, and followed a common pattern of TNC being lowest in June and increasing linearly to a maximum in the fall. Clipping treatments ranging from three to six cuttings per year had little impact on below‐ground morphology and TNC concentrations, probably because of residual leaf area remaining after clipping. Persistence was excellent under all defoliation treatments. We conclude that established kura clover has an extensive crown‐rhizome‐root system which confers the ability to maintain adequate TNC concentrations for persistence under a range of potential defoliation regimes.