Impact of residue management and subsurface drainage on non-point source pollution in the Arroyo Colorado

This study focused on evaluating the impact of residue management (RM) and subsurface tile drainage (SD) on non-point source pollution (NPS) from surface irrigated farms in the Arroyo Colorado (AC) watershed. The objective was to compare the impact of RM and SD on water quality information [Total suspended solids (TSS), nitrates and nitrites (NO₃+NO₂), orthophosphates (ortho-PO₄) , total phosphorus (P), and total Kjeldahl nitrogen (TKN)] of irrigation runoff in six agricultural fields for two irrigation events each year during the 2009 and 2010 growing seasons. The sites that were selected for this study used best management practices (BMPs) such as conservation crop rotation, irrigation land leveling, poly-pipe use, irrigation water management, pest and nutrient management. Results illustrate that furrow irrigated fields using poly-pipe and employing RM as a BMP can lead to decreased TSS and ortho-PO₄ constituents in surface water runoff, thus, lowering the potential for contamination in the AC watershed. There is still more opportunity to conserve water and reduce nutrient loadings considering that approximately 30% of the applied water was lost to runoff in some farms. Finally, results demonstrate that irrigators can play a significant role in the prevention of soluble N compounds from running off-site and into the AC watershed by monitoring irrigation application, as total runoff amounts from fields decreased in 2010 after the field managers were educated about the amount of water applied and running off the field during 2009.