Seasonal factors can affect phosphorus leaching

decrease font size  Resize text   increase font size       Printer-friendly version of this article Printer-friendly version of this article

Editor's note: A special thanks to Dr. Monica Ozores-Hampton for coordinating The Immokalee Report.

Phosphorus (P) is required for the successful commercial production of vegetables and melons in Florida. However, a surplus of P can result in leaching into the groundwater, affecting surface water and adversely impacting water bodies.

Although considered less mobile than nitrogen, P leaching does occur in Florida due to its sandy soils. Best Management Practices—BMPs—have been developed to reduce the environmental losses of nutrients including P.

But limited information exists on the main factors that control P losses to Florida groundwaters.

A BMP study was conducted over six seasons at the Southwest Florida Research and Education Center, UF/IFAS research farm, in Immokalee, Fla. The study’s dataset included a wide range of crop-soil-water-management factors for tomato and watermelon production systems.

Two irrigation methods were used—seepage and sub-surface drip—with varying fertilizer-P rates of 0 to 75 pounds per acre.

During the study, plant available P—measured as Mechlich-1 extractable soil P or M1P—varied from 15 to 145 parts per million, groundwater concentrations of total P (GWP) ranged from 0.53 to 1.27 ppm, and daily rainfall reached a maximum of 8 inches with Hurricane Wilma. Data were analyzed by season and year.

Watch fertilizers more closely during wet fall

The analyses showed that M1P is a good indicator of GWP for the fall growing season as well as on an annual basis. Fertilizer P was also important as it directly affects the M1P in the soil. Water table depth was important for dry spring seasons.

Statistical analyses of the data resulted in the following equations for predicting seasonal and annual GWP.

These models estimate GWP (µg/l) above the spodic horizon for spring, fall and annual periods. Seasonal totals are required for rainfall (cm) and fertilizer-P (kilograms/hectare), while seasonal averages are required for WaterTable (cm) and Mehlich-1P (ppm).

These equations are valid for similar production systems and environments, and illustrate that M1P and fertilizer-P are the two most important factors that govern subsurface P losses for vegetable production in shallow water table regions of Florida.

The fall and annual equations do not include water-related factors and is likely due to large amounts of rainfall received during the start of each fall season. 

This study shows that greater focus on fertilizer (versus water) management is required during the wet fall season. For dry spring season, greater focus is required for irrigation management as water table and rainfall became dominant factors.

The models presented here require readily available data already used by vegetable growers to manage their farms. Rainfall and water table depths are used to manage irrigation and drainage and M1P measurements help determine fertilizer P rates.

These models are unique but simple and can be used as management tools by growers. Although the models represent a comprehensive long-term data, they may not necessarily work for all farms.

The relationships are for dual-cropping systems with plastic-mulched beds and shallow water table conditions. Once similar data are available for different farms, a generic equation may be derived for its use as a screening tool by the growers to manage P losses from their farms. 

Sanjay Shukla is an associate professor of agricultural and biological engineering at the Southwest Florida Research and Education Center. He can be reached at sshukla@ufl.edu. Gregory Hendricks is a senior engineer and research coordinator at the SWFREC.


Prev 1 2 Next All



Buyers Guide

Doyle Equipment Manufacturing Co.
Doyle Equipment Manufacturing prides themselves as being “The King of the Rotary’s” with their Direct Drive Rotary Blend Systems. With numerous setup possibilities and sizes, ranging from a  more...
A.J. Sackett Sons & Company
Sackett Blend Towers feature the H.I.M, High Intensity Mixer, the next generation of blending and coating technology which supports Precision Fertilizer Blending®. Its unique design allows  more...
R&R Manufacturing Inc.
The R&R Minuteman Blend System is the original proven performer. Fast, precise blending with a compact foot print. Significantly lower horsepower requirement. Low inload height with large  more...
Junge Control Inc.
Junge Control Inc. creates state-of-the-art product blending and measuring solutions that allow you to totally maximize operating efficiency with amazing accuracy and repeatability, superior  more...
Yargus Manufacturing
The flagship blending system for the Layco product line is the fully automated Layco DW System™. The advanced technology of the Layco DW (Declining Weight) system results in a blending  more...
Yargus Manufacturing
The LAYCOTE™ Automated Coating System provides a new level of coating accuracy for a stand-alone coating system or for coating (impregnating) in an automated blending system. The unique  more...
John Deere
The DN345 Drawn Dry Spreader can carry more than 12 tons of fertilizer and 17.5 tons of lime. Designed to operate at field speeds up to 20 MPH with full loads and the G4 spreader uniformly  more...
Force Unlimited
The Pro-Force is a multi-purpose spreader with a wider apron and steeper sides. Our Pro-Force has the most aggressive 30” spinner on the market, and is capable of spreading higher rates of  more...
BBI Spreaders
MagnaSpread 2 & MagnaSpread 3 — With BBI’s patented multi-bin technology, these spreaders operate multiple hoppers guided by independent, variable-rate technology. These models are built on  more...


Comments (0) Leave a comment 

Name
e-Mail (required)
Location

Comment:

characters left


Portable Conveyors

Convey-all portable conveyors are designed to handle your crops gently and efficiently. We offer an extensive line of high capacity ... Read More

View all Products in this segment

View All Buyers Guides

Feedback Form
Feedback Form