Potential Efficiency of Grassy or Shrub Willow Buffer Strips against Nutrient Runoff from Soybean and Corn Fields in Southern Quebec, Canada

Abstract

Riparian buffer strips (RBS) are encouraged to control agricultural diffuse pollution. In Quebec Province, Canada, a policy promotes 3-m-wide RBS. Abiding farmers minimally maintain herbaceous vegetation, but nutrient retention efficiency could be improved with woody biomass. This work aimed to assess if fast-growing willows (Salix miyabeana Seemen 'SX64') could reduce nutrient loads to a stream, in addition to yielding biomass. Triplicate treatments of two Salix stem densities and a herbaceous control plot were monitored from 2011 to 2013 in a randomized block design on agricultural fields of the St. Lawrence Lowlands with sandy loam (Saint-Roch-de-l'Achigan [SR]) and organicrich (Boisbriand [BB]) soils. Runoff, interstitial water, and water from the saturated zone were sampled 16 (SR) and 14 (BB) times to quantify nutrient buffering (NO 3 − , NH 4 + , P, and K). Sampling campaigns followed (i) snowmelt or ³15-mm natural precipitation events after (ii) fertilization and (iii) glyphosatebased herbicide applications. Concentration reduction before and after the RBS was highest for nitrates (77-81% in runoff at BB, 92-98% at 35-to 70-cm depth at SR) just after fertilization, when edge-of-field concentrations peaked. Total P removal was observed in runoff after fertilization at SR, and K removal was punctually witnessed at BB. Riparian buffer strips were inefficient for NH 4 and dissolved P removal, and RBS effluents exceeded aquatic life protection standards. Salix plantations, irrespective of stem density, were not more efficient than herbaceous RBS. This shows that without fertilizer input reductions, narrow RBS are insufficient to protect streams from excess nutrients in corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] crops.

Current Insights into the Effectiveness of Riparian Management, Attainment of Multiple Benefits, and Potential Technical Enhancements

“…Several studies explored implications of more active management of the buffer space for diffuse pollution functioning. Hénault‐Ethier et al (2019) found that there was no significant difference in the buffering capacity (for N, P, or K) between 3‐m‐wide riparian zones planted with willow ( Salix spp., regardless of density) and riparian zones with naturally regenerated herbaceous cover. Season strongly affected the buffering ability of the riparian buffer zones, with the highest efficiency occurring when water entering the zone had the highest nutrient concentrations (immediately after sowing and fertilizer application).…”

“…Other studies in the collection offer data or discussion on the nutrient offtakes associated with the timber yields. Zak et al (2019) described that, for the IBZ design planted with willow, the standing biomass yields per hectare (after ∼2 yr growth) was 17 to 40 t dry matter, with 8 to 19 t C, 201 to 458 kg N, and 30 to 70 kg P. Hénault‐Ethier et al (2019) assessed whether the inclusion of fast‐growing willow in riparian buffer zones could improve the nutrient retention of the zone. They cited other work that indicated that willow wood harvested after 3 yr from riparian zones allowed for permanent annual export of 116 to 447 kg N ha −1 , 62 to 239 kg K ha −1 , and 23 to 86 kg P ha −1 .…”

“…Wider benefits of promoting aquatic habitat conditions and resilience and climate services should also be recognized and incentivized. Studies here have addressed biomass benefits from buffers as persuasion for greater riparian buffer space (Dal Ferro et al, 2019; Hénault‐Ethier et al, 2019; Zak et al, 2019). This collection offers messages regarding the handling of wood fuels to maximize economic returns and the integration of green manure as a small supplement within traditional fertilizer regimes on fields, but again, these topics need a consolidated evidence base going forward.…”

The carbon stable isotope compositions of glyphosate and aminomethylphosphonic acid (AMPA): Improved analytical sensitivity and first application to environmental water matrices

“…(ii) The second degradation pathway leads to the formation of sarcosine (C 3 H 7 NO 2 ) and inorganic phosphate, through C–P bond cleavage 31–33 . The massive usage of glyphosate in agricultural and non‐agricultural practices has led to the ubiquitous presence of AMPA in the environment 34–38 . However, studies have demonstrated that in industrial and urban areas, AMPA can also be generated by the degradation of both phosphonates and glyphosate present in wastewater 39–41 .…”

Invertebrate and Plant Community Diversity of an Illinois Corn–Soybean Field with Integrated Shrub Willow Bioenergy Buffers

“…Furthermore, a given bioenergy crop production system may not be initially designed with biodiversity support in mind but instead may be designed to enhance biomass production, soil health, or other ecosystem services, such as nutrient loss reduction. For example, willows have commonly been used for phytoremediation, such as vegetative filters and buffers to remove nutrients from wastewater and leachate from agricultural systems [19][20][21][22]. Most of the previous literature on willows and biodiversity, particularly invertebrates, were plantation studies, with the majority of them conducted outside of the U.S. [17].…”