Herbicide and Nutrient Transport from an Irrigation District into the South Saskatchewan River

Abstract

Pesticides and nutrients can be transported from treated agricultural land in irrigation runoff and thus can affect the quality of receiving waters. A 3-yr study was carried out to assess possible detrimental effects on the downstream water quality of the South Saskatchewan River due to herbicide and plant nutrient inputs via drainage water from an irrigation district. Automated water samplers and flow monitors were used to intensively sample the drainage water and to monitor daily flows in two major drainage ditches, which drained approximately 40% of the flood-irrigated land within the irrigation district. Over three years, there were no detectable inputs of ethalfluralin into the river and those of trifluralin were less than 0.002% of the amount applied to flood-irrigated fields. Inputs of MCPA, bromoxynil, dicamba and mecoprop were 0.06% or less of the amounts applied, whereas that for clopyralid was 0.31%. The relatively higher input (1.4%) of 2,4-D to the river was probably due its presence in the irrigation water. Corresponding inputs of P (as total P) and N (as nitrate plus ammonia) were 2.2 and 1.9% of applied fertilizer, respectively. Due to dilution of the drainage water in the river, maximum daily herbicide (with the exception of 2,4-D) and nutrient loadings to the river would not have resulted in significant concentration increases in the river water. There was no consistent remedial effect on herbicides entering the river due to passage of the drainage water through a natural wetland. In contrast, a considerable portion of the nutrients entering the river originated from the wetland.

Spatial variation of nitrogen fixation in lakes of the northern Great Plains

“…This patterns leads to progressive declines in N supply and N : P ratios that favor stronger development of cyanobacterial populations (MacGregor et al 2001;Havens et al 2003;Tonno and Noges 2003) in more downstream lakes (Graham 1997;Patoine et al 2005), and consequently greater potential for pelagic N 2 fixation (Table 2). We expect these patterns should also occur in catchments with either naturally high P supply (e.g., geological substrates derived from Pleistocene sea beds; lowland Europe), or in managed catchments in which P additions from agriculture greatly exceed soil P storage capacity, leading to low N : P supply ratios (Cooke and Prepas 1998;Cessna et al 2001;Foy et al 2002).…”

Dynamics of clopyralid herbicide during composting in small composting experiment units

“…42) In irrigated land in Saskatchewan, Canada, clopyralid was found throughout the soil profile within 20 d of application and was detected in the first water flowing in the tile drains, 43) and as much as 0.31% of the applied clopyralid was carried in drainage water from the irrigation district and released into the South Saskatchewan River. 44) It was subsequently detected in 15 reservoirs in the Northern Great Plains of North America, and was identified as a contaminant in drinking water drawn from these reservoirs. 45) Thus, because of its high leaching potential in the environment, clopyralid is likely to be eluted during composting, although this was not reported in any of the previous studies.…”

Use of a potentiometric vital dye to determine the effect of the herbicide bromoxynil octanoate on mitochondrial bioenenergetics in Chlamydomonas reinhardtii

“…It has been available since 1963, mainly in combination with other herbicides to broaden the spectrum of weed control 13. It is also marginally water soluble and can run off into watercourses 14. Secondly, in addition to the inhibition of photosynthetic electron transport at photosystem II,15 bromoxynil also acts as an uncoupler of electron flow and proton efflux in the mitochondria 16…”