Context for re-evaluating agricultural source phosphorus loadings to the Great Lakes

Abstract

Joosse, P. J. and Baker, D. B. 2011. Context for re-evaluating agricultural source phosphorus loadings to the Great Lakes. Can. J. Soil Sci. 91: 317–327. Over the past decade, scientists have been discussing the re-emergence of harmful algal blooms and excessive growth of Cladophora in some areas of the Great Lakes. An observation that has emerged from these discussions is that management of non-point or diffuse sources of phosphorus will be more important in the future in order to address symptoms of eutrophication in the nearshore. This paper provides context for this renewed focus on managing non-point source tributary loads and is based primarily on materials and discussions from the Great Lakes P Forum. There are changes that have occurred in the lakes and tributaries in the past 15 yr that indicate a greater need to focus on non-point sources, whether urban or rural. Changes have also occurred in land management to reduce non-point P losses from agriculture. While these changes have reduced sediment and particulate P loading in some Ohio tributaries, the more bioavailable, dissolved P forms have increased. As there is incomplete knowledge about the mechanisms that are influencing algal growth, it could be a challenge to demonstrate, in the near term, improvements in water quality with further P reductions from agriculture alone. Regardless, there appears to be a desire for improved accountability and transparency for agricultural non-point source P management.

Phosphorus fertilization, soil stratification, and potential water quality impacts

“…However, in recent years P losses from agricultural fields in the Western Lake Erie Basin (WLEB) have been identified as a primary contributor to resurgent harmful and nuisance algal blooms (HNABs) in Lake Erie (Chaffin et al 2011). While there has not been any significant change in TP loading since the mid-1990s, there has been an increase in soluble P (SP) loading during this period (Joose and Baker 2011). This period coincides with "peak" adoption of no-till in this watershed.…”

“…2011). While there has not been any significant change in TP loading since the mid-1990s, there has been an increase in soluble P (SP) loading during this period (Joose and Baker 2011). This period coincides with "peak" adoption of no-till in this watershed.…”

Combining precision conservation technologies into a flexible framework to facilitate agricultural watershed planning

“…T he need to reduce nutrient loads from agricultural watersheds poses a daunting challenge, considering the continental scale of water quality problems in the Gulf of Mexico (Turner et al 2008), Great Lakes (Joose and Baker 2010), and Chesapeake Bay (Russell et al 2008). Strategies to address nutrient reduction have suggested that a mix of practices will be required across multiple landscape positions to achieve water quality goals (Iowa Nutrient Reduction Strategy Science Team 2012).…”

Determining the number of measurements required to estimate crop residue cover by different methods

“…There is concern, however, that the extent of conservation tillage has peaked and that there is now more tillage and bare soil exposed over winter than in the past (A. Hayes, Ontario Ministry of Agriculture, Food and Rural Affairs [OMAFRA] personal communication; Statistics Canada 2016). Such practices are of even greater importance in southwestern Ontario, an area where agricultural practices, including tillage practices, have an effect on Great Lakes water quality (Joosse and Baker 2011;Molder et al 2015). The amount of crop residue left in the field after harvest is important for soil and water storage (Daughtry and Hunt Jr. 2008), erosion control (Kumar and Goh 1999;Mailapalli et al 2013;Enciso et al 2014), and assessment and modeling of soil carbon (C) sequestration (Aguilar et al 2012a).…”