Department of Pesticide Regulation

Environmental Monitoring and Pest Management Branch

1020 N Street, Room 161

Sacramento, CA 95814-5624

Protocol for Sampling Phase One Grape Management Practices

Preliminary Experiment #1

Study #144

March 1996

I. INTRODUCTION

The Department of Pesticide Regulation (DPR) is conducting an educational and outreach program to mitigate off-site movement of the preemergent herbicides simazine and diuron from grape vineyards in Fresno and Tulare Counties. As part of this program, the University of California Cooperative Extension (UCCE) is conducting field studies in cooperation with DPR to test different management practices for their ability to reduce the downward movement of herbicides in coarse soils while maintaining acceptable crop health and weed pest control. DPR will perform sampling of soil in this study to assess the movement of simazine after irrigation water application.

II. OBJECTIVES

A. Furrow Irrigation

The objective in the furrow irrigation experiment is to evaluate and provide observational data on simazine movement under selected treatments.

B. Drip Irrigation

The objective in the drip irrigation experiment is to compare the relative effect of selected treatments on downward movement of simazine through the soil profile under drip irrigation conditions.

III. PERSONNEL

This study will be conducted by the Environmental Hazards Assessment Program (EHAP) under the general direction of Don Weaver, Senior Environmental Research Scientist. Key personnel are listed below:

Project Leader: Frank Spurlock

Field Coordinator: Cindy Garretson

Senior Staff Scientist: John Troiano

Laboratory Liason: Nancy Miller

Experimental Design/Data Analysis: Terri Barry

Authorship of the final report should include, but not be limited to, Frank Spurlock, Cindy Garretson, Terri Barry, and John Troiano. Questions concerning this monitoring program should be directed to Peter Stoddard at (916) 324-4078, facsimile (916) 324-4088.

IV. STUDY DESIGN

For these preliminary studies, a selected number of the total experimental treatments planned by UCCE will be sampled for movement of the herbicide simazine.

A. Furrow Irrigation.

In the flood irrigation experiment, seven treatment plots (shown on plot map 1) will be sampled by DPR. The treatments on these plots are listed below.

Treatment 1. 2 lb simazine ai/ac + 2 lb diuron ai/ac

Treatment 2. 1 lb simazine ai/ac + 1 lb diuron ai/ac + surfactant

Treatment 4. 1 lb simazine ai/ac + 1 lb diuron ai/ac + no surfactant

Treatment 6. Roundup 0.5 ai/ac as needed

The plots to be sampled are those closest to the upstream, or headwater area of the furrow irrigation experiment shown in plot map one. Treatment number six is a control to allow measurement of carryover residue concentrations from previous applications.

There will be one sampling event for the furrow irrigation experiment. The plots marked on plot map one for treatments 1, 2, and 4 will be sampled by soil coring after the first irrigation event. Two composite cores (5 foot cores in 6" increments) for treatments 1, 2 and 4 will be taken at the approximate locations shown in the plot map. Each composite core will be obtained from compositing two individual soil cores. A single composite core (from two individual cores) will be taken from each of the control treatment plots (number 6).

The total number of soil samples to be analyzed from the furrow experiment will be 120 (a. Plots for treatments 1, 2 and 4: 5 plots x 2 composite cores per plot x 10 discrete samples per core = 100; plots for control treatment 6: 2 plots x 1 composite core per plot x 10 samples per core = 20; 100 + 20 = 120).

B. Drip Irrigation.

Three selected treatments (Treatments 3, 4 and 5 on plot map 2) by three replicates will sampled by soil coring in the drip irrigation experiment.

Treatment 3. Variable rate application: 1 lb ai/ac simazine + 1 lb ai/ac diuron

on vinerow and 2 lb ai/ac simazine + 2 lb ai/ac diuron to canopy edge;

16" x 30" fabric under emitters;

Treatment 4. Variable rate application as above; no fabric

Treatment 5. 2 lb ai/ac simazine + 2 lb ai/ac diuron applied from canopy

edge to canopy edge over berm

Each treatment plot in each block will be sampled by taking single cores (0-5 feet in 6" increments) to yield 3 treatments x 3 blocks x 1 five foot composite core x 10 samples per core = 90 soil samples. These soil cores will be taken after the first drip irrigation event. Two cores (0-5 feet in 6" increments) will also be taken for background samples outside the study area. The total number of soil samples taken in the drip irrigation experiment will be 90 + 20 = 110.

The total number of soil samples collected will be 120 (furrow) + 110 (drip) = 230 samples. The soil samples will be handled as provided in the following EHAP SOPS:

Collecting of Soil Cores with Bucket Augers

Transport and Storage of Soil Samples

V. CHEMICAL ANALYSIS / QUALITY CONTROL

Samples will be analyzed for simazine by California Food and Agriculture Analytical Chemistry Laboratory in Sacramento using the ELISA immuno-assay method; the detection limit is 15 ug kg soil-1. The soil ELISA QA/QC procedures will consist of a matrix blank plus two matrix spikes to be included with each extraction set. Results from the matrix spikes will be evaluated to determine if they fall within predetermined control limits.

Two cores from the furrow irrigation control plots and two cores randomly selected from the drip irrigation plots will be analyzed at DPR facilities in Fresno for particle size analysis and organic carbon.

VI. DATA ANALYSIS

Each core will be evaluated for total simazine recovered and depth of leaching by treatment. An additional comparison of recovery and/or depth of leaching with late season residual efficacy may also be possible.