Stream Nitrate Trends Affected by Farming Practices in the Walnut Creek Watershed

Date: 
Feb 2014

Issue

The Walnut Creek watershed in southern Story County has been the site of extensive monitoring and research since 1991. Water flow monitoring has been measured at several sites, and nitrate concentrations in water have been measured since 1991, with phosphorus monitoring since 2000. Producers in the watershed were surveyed from 1991 to 1994 to track farming practices.

Objective

Walnut Creek represents a unique opportunity to examine the effects of not only weather and changing cropping patterns on water quality, but also water quality changes linked to changes in individual field management practices. The latter will be accomplished by repeating the 1991–1994 survey of farmers.

Approach

This research will quantify the changes in nitrate concentration and load using data collected since 1991 for Walnut Creek. A survey will be conducted of current farming practices used by all farmers operating within Walnut Creek, gauging current knowledge and attitudes regarding management practices to minimize nitrate losses. Trends in water quality data over the past 22 years in regards to the weather, cropping and farm management information will be analyzed, and the effect of these variables on nitrate concentrations and loads within the creek will be quantified. Finally, the propensity of farmers in the Walnut Creek study area to adopt various nitrate-reducing practices, modeled as a function of farmer characteristics (demographics, attitudes, farm finances) and field conditions (crop cover, soil conditions, topography) will be statistically estimated.

Project Updates

June 2016

Data was obtained from six continuous monitoring stations along Walnut Creek, making it possible to calculate water flow, nitrogen and phosphorus rates at each station. USDA satellite images for the Walnut Creek watershed were obtained, and linked to farm parcels in the watershed. Farm parcel operators have been identified, and preliminary survey questions for these operators have been drafted and are under review.

March 2016

Data was obtained from six continuous monitoring stations along Walnut Creek. From this raw data, water flow, N and P rates were calculated at each monitoring station. The most recent USDA satellite images in the Walnut Creek watershed were obtained and compiled. To address issues with data privacy, changes to the proposed survey and consent letter are being made.

December 2015

Data continues to be collected from six continuous monitoring stations along Walnut Creek. Farm parcel operators and their addresses were identified. A draft survey was pre-tested with ISU staff and a select group of farmers, and some small changes were made to the survey.

September 2015

Data was collected from six continuous monitoring stations along Walnut Creek. USDA satellite images and cropping data back to 2000 in the Walnut Creek watershed has been compiled into a master database linked to farm parcels. Preliminary farm survey questions have been drafted. A literature review on nutrient reduction practices and farmer adoption has been done, and a conceptual model on farmer adoption developed.

June 2015

Water quality data has been collected from Walnut Creek since 1991, and producers in the watershed were surveyed from 1991 to 1994 to track farming practices. A new survey of farmers in the watershed is being prepared, an interview protocol for on-farm visits developed and the final land parcel ownership list compiled. GIS work identifying fields back to 1990 is complete, and crop rotation data between 1990 and 2012 is finished. Compilation is underway on crop rotation data since 2012.  

March 2015

Walnut Creek in southern Story County represents a unique opportunity to examine the effects of not only weather and changing cropping patterns on water quality, but also water quality changes linked to changes in individual field management practices. That’s because this watershed has been the site of extensive monitoring and research since 1991. Producers in the watershed were surveyed from 1991 to 1994 to track farming practices. A new survey of farmers in the watershed is being prepared, and an interview protocol for on-farm visits developed. Water quality and crop rotation data since 1990 is being compiled.

December 2014

The Walnut Creek watershed in southern Story County has been the site of extensive monitoring and research since 1991. Nitrate concentrations in water have been measured since 1991, with phosphorus monitoring since 2000. Producers in the watershed were surveyed from 1991 to 1994 to track farming practices. Walnut Creek represents a unique opportunity to examine the effects of not only weather and changing cropping patterns on water quality, but also water quality changes linked to changes in individual field management practices. The latter will be accomplished by repeating the 1991–1994 survey. A graduate student has been hired for this two-year project, and a literature review and conceptual model of farmer adoption completed. The initial survey has been drafted.