Significance of herbicide order in sequential applications to target weeds in a sunn hemp living mulch

Abstract

Striking a balance between the weed control capacity of living mulches and their competition with the main crop is complex. At rates that avoid severe injury to living mulch, herbicides may reduce their vigor while simultaneously contributing towards weed control. In a two-year field study carried out in Freeville, NY, USA, we evaluated the effects of various combinations consisting of two herbicides, applied sequentially at reduced rates, on the growth of a sunn hemp living mulch and weeds (including common lambsquarters, common purslane, hairy galinsoga, and Powell amaranth). When a herbicide with primarily POST activity (Type 1) (e.g., rimsulfuron, 0.005 to 0.007 kg ai ha-1) was applied first, performance of sunn hemp (1.7 to 3.9 tons ha-1 dry biomass; 10 to 88% groundcover) was poor and weed growth (25 to 62% groundcover) was high, likely because sunn hemp, severely injured at a young growth stage, was outcompeted by weeds. A follow-up application (approximately two weeks later) of a herbicide with primarily PRE and residual activities (Type 2) (e.g., metribuzin, 0.05 to 0.15 kg ai ha-1), with a surfactant to enhance its POST activity, had little effect on established weeds. However, because sunn hemp was already 20 cm tall at weed emergence, applying a Type 2 herbicide first, did not cause severe injury to sunn hemp and reduced weed pressure, thereby also enhancing sunn hemp performance (3.8 to 6.1 tons ha-1 dry biomass; 85 to 94% groundcover). Moreover, the follow-up application of a Type 1 herbicide affected the smaller weeds more (4 to 21% groundcover) than the better-established sunn hemp. Our results demonstrate that an appropriate sequence of herbicides at reduced rates may be important to control weeds while maintaining a healthy living mulch stand.

Physiological and Biochemical Changes in Vegetable and Field Crops under Drought, Salinity and Weeds Stresses: Control Strategies and Management

“…The application of high-level herbicide often decreases the benefits of a living mulch; however, low-level led to allowing extreme mulch-crop competition. Recent experimentation has focused on the application of herbicides and living mulch to control weeds [237]. Boselli et al [238] examined eight rye varieties as cover crops, focusing on their biomass production and allelochemical activities; significant differences in the suppression potential of these varieties showed depending on some allelochemicals.…”

The Potential of Three Summer Legume Cover Crops to Suppress Weeds and Provide Ecosystem Services—A Review

“…Bundit et al [38] reported remarkable suppression of grass weeds, broadleaf weeds, and sedges, resulting in a 95% reduction in total weed biomass when a seeding rate of 67 kg seed ha −1 was selected. Bhaskar et al [39] selected seeding rates of 65 and 90 kg seed ha −1 that reduced weed biomass by 73 and 92%, respectively, in their two-year field trials, in which common lambsquarters (Chenopodium album L.), common purslane (Portulaca oleracea L.), hairy galinsoga (Galinsoga quadriradiata Ruiz & Pav., 1798), Powell's amaranth (Amaranthus powellii S.Watson), and shepherd's purse [Capsella bursa-pastoris (L.) Medik.] were the dominant weeds.…”

Integrated management of living mulches for weed control: A review

“…Some recent work has focused on combining these two strategies. In the study of tomato grown with a sunnhemp living mulch (Bhaskar et al 2020) and a concurrent study of sunnhemp in monoculture (Bhaskar et al 2021), two herbicides were applied sequentially at reduced rates. Applying a herbicide with soil residual activity followed by a herbicide with greater postemergence activity helped balance living mulch performance, weed control, and (in Bhaskar et al 2020) tomato yield.…”

“…Acknowledgments. We dedicate this review to the late Dr. Nathan Hartwig (1937-2021, a true pioneer in the study of living mulches. This research received no specific grant from any funding agency, commercial or not-for-profit sectors.…”