Submitted to: Journal of Soil and Water Conservation Society
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/19/2011
Publication Date: 2/1/2012
Citation: Krutz, L.J., Locke, M.A., Steinriede Jr, R.W., Reddy, K.N., Libous Bailey, L.M., Burke, I. 2012. Water, sediment, and metolachlor transport between wide- and narrow row cotton production systems. Journal of Soil and Water Conservation Society. 67:1-8. Interpretive Summary: Changing the way we plant cotton in the Mid-South could improve the regions surface water quality. We evaluated sediment and herbicide loss from 4- to 6-leaf cotton planted in narrow and wide rows. Planting cotton on flat beds with rows spaced 15-inches apart reduced sediment loss by at least 38% relative to cotton planted on raised beds spaced 38-inches apart. Moreover, planting cotton on narrow rows reduced herbicide loss relative to wide-row systems if runoff and factors affecting pesticide movement were similar between row spacings. Converting from wide-to narrow-row cotton, therefore, could positively impact Mid-South water quality.
Technical Abstract: Planting cotton [Gossypium hirsutum (L.)] in narrow rather than wide rows could reduce erosion and off-site agrochemical transport, but this hypothesis needs to be evaluated under Mid-South cropping conditions. Field studies were conducted near Stoneville, MS on a Dundee silty clay loam from 2006 through 2007 to evaluate water, sediment and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide] loss in narrow (38-cm) and wide-row (102 cm) cotton. One day after a post-emergence metolachlor application over 4- to 6-leaf cotton, 60 mm h-1 of simulated rainfall was applied until 25 min of runoff was generated per plot. Depending on year, planting cotton in narrow rather than wide rows either had no effect or reduced cumulative runoff by 25%. Sediment loss, however, was at least 38% lower from narrow- than wide-row cotton, regardless of year. Cumulative metolachlor loss was 27% higher in narrow- relative to wide-row cotton in 2006, but the trend reversed in 2007. Results indicate that nearly flat seedbeds in narrow-row systems reduce sediment loss relative to wide-row cotton planted on slightly raised beds, regardless of canopy coverage. Moreover, planting cotton on narrow rather than wide rows can reduce the offsite transport of post-emergence, non-polar pesticide applied at or prior to the 6-leaf stage if cumulative runoff is reduced in the former, and factors governing mixing-zone pesticide concentrations are similar between systems, that is, canopy coverage, pesticide mass intercepted by the canopy, pesticide washoff and time-to-runoff. Consequently, converting from wide- to narrow-row cotton could positively impact Mid-South water quality.