Nutrient and Pesticide Loads in Subsurface Drainage from Organic and Conventional Cropping Practices

1998 Annual Report for LNC98-137

Project Type: Research and Education
Funds awarded in 1998: $104,777.00
Projected End Date: 12/31/2000
Region: North Central
State: Illinois
Project Coordinator:
Gregory McIsaac
Dept of Natural and Environmental Resources, University of Illinois

Nutrient and Pesticide Loads in Subsurface Drainage from Organic and Conventional Cropping Practices

Summary

The primary objective of this project is to quantify and compare the concentrations and loads of nitrogen (nitrate, ammonium and organic N), phosphorus (dissolved phosphate and total P) and herbicides (atrazine, alachlor and metolachlor) in subsurface (tile) drain effluent from certified organic and conventional corn-soybean cropping practices used in central Illinois. Soils, climate and management influence chemical concentrations in drainage water.

Our research design is to monitor subsurface drainage from four pairs of fields in different locations in the state. Each pair will have similar soils and be subject to similar climate but one field will be managed organically and the other conventionally. A difference in water quality between the two fields in a pair may represent an effect of the different management practices or random variation in soil properties or measurement error. If differences in water quality variables are consistently positive or negative across multiple pairs of fields, this would provide evidence of a water quality effect of organic farming practices across the locations tested.

In the first year of this project we have installed flow monitoring and sampling equipment at three pairs of organic and conventional fields. A fourth pair of fields is being monitored with funding from Illinois Department of Agriculture and Illinois Council of Food and Agricultural Research. Monitoring efforts started in 1996 with funding from other agencies suggest that nitrate and chloride concentrations in drainage from organically managed fields are usually less than concentrations in water draining from the conventionally managed fields. Differences in nitrate concentration have been greatest when the organically managed fields are in a forage/green manure crop, at which time concentrations in drainage water from organically managed fields average approximately 2 mg N/L while concentrations in drainage from conventionally managed fields range from 10 to 20 mg N/L.

Nitrate concentrations in drainage water from the organically managed fields increased when the green manure crops were incorporated into the soil and row crops are grown. In most instances these concentrations have been less than the concentrations in the drainage water from conventionally managed fields, but in 1999 there was a significant exception to this tendency in one field. Nitrate concentrations in one of the continuously monitored organically managed fields increased from 2 mg N/L when a green manure crop was grown, to 20 mg N/L, which exceeded the nitrate concentration in the drainage water from the neighboring conventionally managed field (13 mg N/L). This field appears to have a longer period of green manure production than other fields studied.

The current project will quantify the load of nitrate and other chemicals from the different management practices, which will be useful for assessing and comparing environmental impacts of organic and conventional production practices. Monitoring should be conducted over several years to quantify influences of climate on chemical transport to tile drains.

For more information:
Greg McIsaac
University of Illinois
Department of Natural Resources and Environmental Sciences
W-503 Turner Hall
1102 S. Goodwin Ave.
Urbana, IL 61801
217-333-9411
217-244-3219 (fax)
gmcisaac@uiuc.edu

Collaborators:

Gregory McIsaac

U of IL
IL 61801
Michael Rahe

IL Dept. of Ag
IL 62794