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ARS Home » Midwest Area » Ames, Iowa » National Laboratory for Agriculture and The Environment » Agroecosystems Management Research » Research » Publications at this Location » Publication #315222
Title: Water quality in organic systems

Author
item CAMBARDELLA, CYNTHIA
item DELATE, KATHLEEN - IOWA STATE UNIVERSITY
item JAYNES, DAN

Submitted to: Sustainable Agriculture Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/17/2015
Publication Date: 6/20/2015
Citation: Cambardella, C.A., Delate, K., Jaynes, D.B. 2015. Water quality in organic systems. Sustainable Agriculture Research. 4(3):60-69.

Interpretive Summary: Nitrate-N contamination of surface waters is a major water quality concern in the upper Midwest USA. Environmental impacts associated with agricultural production have encouraged producers to investigate alternative management practices, including organic farming methods. This study quantifies growing season tile drainage water nitrate-N losses for conventional and organic grain cropping systems from 2012-2014 at the fully-instrumented, tile-drained USDA-ARS Organic Water Quality (OWQ) research site near Boone, IA. We found that tile water nitrate-N loss for the entire 3-year period from a conventionally managed corn-soybean system (79.2 kgN/ha) was nearly twice as much as from an organically managed corn-soybean-oat/alfalfa-alfalfa system (39.9 kgN/ha). These results demonstrate that organic farming practices, such as the application of composted animal manure and the use of forage legumes and green manures within extended cropping rotations, can improve water quality in Midwestern tile-drained landscapes. This information will be useful to scientists seeking to understand the effects of organic management on agroecosystems, and to farmers who are contemplating transitioning to organic production.

Technical Abstract: Non-point source contamination is a major water quality concern in the upper Midwestern USA, where plant nutrients, especially NO3-N, are susceptible to leaching due to extensive subsurface draining of the highly productive, but poorly drained, soils found in this region. Environmental impacts associated with conventional production have encouraged producers to investigate organic methods. The USDA-ARS Organic Water Quality (OWQ) experiment, established in 2011, compares organic (C-S-O/A-A) and conventional (C-S) crop rotations and an organic pasture (bromegrass, fescue, alfalfa, white clover) system. Thirty fully-instrumented, tile-drained plots (30.5m x 30.5 m) laid out in a randomized block design with 5 field replications, isolate tile drainage from each plot and permit comparison of treatment effects on tile flow and tile nutrient concentrations. Objectives for this study were to quantify growing season tile drainage flow, tile water nitrate-N concentrations, and tile water nitrate-N loads for conventional and organic grain cropping systems from 2012-2014. Temporal patterns of tile water flux were similar for all cropping systems for all years, except for the pasture system in 2012 and tile water N concentrations were highest in the conventional C-S system except for the early Spring 2012. Tile water N loading loss for the entire 3-year period from the conventional C-S system (79.2 kgN ha-1) was nearly twice as much as the N loss from the organic C-S-O/A-A system (39.9 kgN ha-1); the pasture system (16.5 kgN ha-1) lost the least amount of N over the 3 years. Results of this study suggest that organic farming practices, such as the application of composted animal manure and the use of forage legumes and green manures within extended cropping rotations, can improve water quality in Midwestern tile-drained landscapes.