Floating Aquatic Vegetation Impact on Farm Phosphorus Load:

FINAL REPORT DRAFT

Samira Daroub Timothy Lang

Jennifer Cooper Anne Sexton

Everglades Research and Education Center

BMP Training April 26, 2018

Table of Contents

• Chapter 1: Introduction

• Chapter 2: Discharge water summary of control and treatment farm phosphorus

and environmental parameters

• Chapter 3: Ambient water summary of control and treatment farm phosphorus

and environmental parameters

• Chapter 4: Paired-farm comparison of pre- and post-FAV controlled phosphorus

loads and other factors influencing phosphorus loads

• Chapter 5: Comparison of sediment phosphorus between control and treatment

farms during the treatment period

• Chapter 6: Seasonal impacts from suppressing floating aquatic vegetation on

canal water properties

Chapter 1: Introduction

• Everglades Agricultural

Area background

• Review of literature and

research justification

– Phosphorus Co-

precipitation with Calcium

Carbonate

– Phosphorus Storage in

Sediments

Objectives

1) Evaluate FAV management practices in the EAA farm canals for impact on

a) farm drainage water phosphorus (P) load

b) P speciation of farm drainage water

c) canal sediment properties

2) Use research results to develop a BMP for managing FAV in farm canals that further lowers farm P loads.

3) The goal is to provide growers an additional tool in their efforts to reduce off-farm P loading in the Everglades Agricultural Area.

Chapter 1: Introduction

• Methods

• Analyses

– 2-yr calibration and 4-yr treatment periods:

• Farm pairs 2501/0401, 1813/6117, and 3102/3103

– 3-yr calibration and 3-yr treatment periods:

• Farm pair 4701/4702

– Treatment accomplished through vigilant monitoring and spot spraying FAV

• Statistics and report structure

– Paired watershed design with repeated measures

– Boxplots, Correlations, Multiple Linear Regressions

– Compare calibration to treatment period and determine difference causes

Chapter 1: Introduction

Major Hypothesis

-Suppression of FAV will reduce off-farm P loads

-Suppression of FAV will increase production of denser Ca-

P precipitates

Chapter 1: Introduction

Table 6 - 1. Experimental farms identifying numbers, treatment-control designation, and size.

FarmID

(T/C)

0401

(T)

2501

(C)

6117

(T)

1813

(C)

3103

(T)

3102

(C)

4702

(T)

4701

(C)

Farm Pair 1 2 3 4

Size (acres) 908 824 781 594 609 1387 640 630

Dominant

Crop Sugarcane Sugarcane Sugarcane Sugarcane Sugarcane Sugarcane Sugarcane Sugarcane

Number of

Pumps 2 2 1 1 1 3 1 1

SFWMD

Receiving

Canal

West Palm

Beach Canal

West Palm

Beach Canal

West Palm

Beach Canal

West Palm

Beach Canal Ocean Canal Ocean Canal

Hillsboro

Canal

Hillsboro

Canal

T = treatment; C = control; SFWMD = South Florida Water Management District

Chapter 1: Introduction

S-5A Sub-basin

Farm 0401: 908 acres- cane w/corn

Farm 2501: 824 acres- cane w/corn → sod

Farm 1813: 594 acres- cane w/corn

Farm 6117: 784 acres- cane w/corn

S-6 Sub-basin

Farm 3102: 1387 acres- cane w/veg/corn/rice

Farm 3103: 609 acres- cane w/veg/corn/rice

Farm 4701: 630 acres- cane w/rice

Farm 4702: 640 acres- cane w/rice

Chapter 4: Paired-farm comparison of pre- and post-FAV

controlled phosphorus loads and other factors influencing

phosphorus loads

Chapter 4 objectives:

objectives:

– Identify which independent variables affect UAL, UAD, and

FWTP and the strength of the effect

– Forecast the degree of change a single independent

variable will have on UAL, UAD and FWTP

– Determine if multiple linear regression equations may be

used to predict future UAL, UAD and FWTP if independent

variables are known

Farm Paired Design: Methods

Chapter 4: Paired-Farm Comparison: Farm Pair 4 FAV

Chapter 4: Paired-Farm Comparison: Farm Pair 4

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Chapter 4: Paired-Farm Comparison: Farm Pair 4

Chapter 4: Paired-Farm Comparison

Summary:

– Drainage is often the dominant variable for UAL rather than

FWTP – drainage volume is very important

– Reduction of UAL in two of the treatment farms were driven by

lower discharge volumes in the treatment period, there was no

change in the third pair, and the last farm pair (4701-4702) was

driven by reduction of FWTP

Final Conclusions

General Conclusions – Experimental Design

Conclusions: 1. Flaws in the experimental design, namely the lack of FAV cover control in

control farms and restrictions on seeding FAV in treatment farms, resulted in farm canal designations being unrepresentative of FAV effects on water properties.

2. In the future, the experimental design needs to be restructured so that control farms have no FAV cover and treatment farms are seeded to full coverage to analyze overall impacts of FAV suppression.

Conclusions – Objective 1

Objective 1: Evaluate two floating aquatic vegetation (FAV)

management practices in the Everglades Agricultural Area (EAA)

farm canals for impact on farm drainage water P load, along with

other factors that affect P loads

– Suppression of FAV below a threshold of 25% was not found to

be beneficial for reduction of farm drainage water P loads

because the FAV threshold was set too high

– Drainage is often the dominant variable for UAL rather than

FWTP – drainage volume is very important

Conclusions – Objective 2

Objective 2: Evaluate the effect of two FAV management practices

on P speciation of farm drainage water and on farm canal

sediment physical and chemical properties

– Suppression of FAV in treatment farms below a threshold of 25%

was found to lower sediment total P concentrations and increase

sediment bulk density

– Treatment farms experienced less deposition of lightweight

detrital material from aquatic plants that are easily transportable

during pumping events

– Increased sediment density may be due to the formation of

dense P containing Ca-P precipitates at higher pH levels found

in FAV-free canal water

Conclusions – Objective 3

Objective 3: Use the information from the research for the

development of a best management practice (BMP) for managing

FAV to produce denser

– Final conclusions are that suppression of FAV can be an effective tool

for reducing discharge total P at the farm scale

– Additional statistical analyses (BACI, PCA, storm impacts, seasonal

impacts) should be conducted to better understand the various factors

that affect P load discharge with and without FAV coverages

Potential New BMP Research

• Create updated BMP manual for growers

• Need to do more statistical analyses: – Storm impacts, Seasonal impacts

– BACI (before and after comparisons)

– PCA (principal component analysis) with all parameters

• Impact of sediment removal – Clean sediments from all farms

– Monitor discharge sediments after cleaning and long term

• Continue with drainage and ambient water sampling

• Other ideas from our Advisory Committee

Questions/Comments/Suggestions?