My Field has High Soil Test P. Now what?

1
My Field has High Soil Test P. Now what?

• John A. Lory, Ph.D.
• Division of Plant Sciences
• Commercial Agriculture Program
• University of Missouri

2
P Assessment Scale Field
Nutrient Management Scale Farm
3
Water Quality Scale Watershed
4
P Assessment Scale Field
Nutrient Management Scale Farm
Water Quality Scale Watershed
5
(No Transcript)
6
Lake 3 MU Dairy Farm Lake 6 acres Watershed
77 acres Mean soil test P 94 lbs/a
197 ppb P
7
Missouri Reservoirs
Missouri reservoirs
Water Clarity as measured by Secchi depth (m)
Lake 3
Jones and Knowlton 1993
8
Lake 1 MU Dairy Farm Lake 15 acres Watershed
135 acres Mean soil test P 69 lbs/a
223 ppb P
9
Lake 2 MU Dairy Farm Lake 2.4
acres Watershed 22 acres Mean soil test P 91
lbs/a
Lake 2 68 ppb P
10
Understanding Edge of field P losses
11
Effect of soil test P on runoff P in forage
systems (small plot runoff)
Creldon Soil
Dissolved Reactive P in runoff (ppb)
Bray-1 Soil Test P (lbs/acre)
12
What are my options?
223 ppb P
13
What are my options? Improve timing of application
223 ppb P
14
Improve timing of surface application
200 lbs./acre phosphate applied 3/22/00 to forages
Water Soluble P in Runoff (ppm)
Days After Treatment
Mt. Vernon, MO
15
Effect of recently applied P on runoff P in
forage systems
DAP
Poultry Litter
Dissolved Reactive P (mg kg-1)
Days after application
16
Soil moisture at Mt. Vernon, MO 2003
Saturated soil
Volumetric Water Content ()
2 inches
4 inches
Precipitation (in)
Aug.
Oct.
Nov.
Dec.
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Sep.
17
Soil moisture at Mt. Vernon, MO 2004
Saturated soil
Volumetric Water Content ()
2 inches
4 inches
Precipitation (in)
Aug.
Oct.
Nov.
Dec.
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Sep.
18
Nitrogen for Tall Fescue Hay
Forage yield
Herd feed requirement
April
August
October
June
19
Litter is an excellent fertilizer for fall fescue
growth
20
What are my options? Lower P index on fields
223 ppb P
21
The importance of erosion
22
(No Transcript)
23
What are my options? Lower P balance watershed
Export more manure
Import less manure and fertilizer
223 ppb P
24
What are my options? Lower P balance watershed
Should I raise STP on this field?
223 ppb P
25
Raise soil test P 10 units with manure

• Low testing field 5 ppm to 15 ppm
• Very high testing field 50 to 60 ppm
• Very high testing field 500 to 510 ppm

Is there a water quality benefit from choosing
one field over another?
26
Raise soil test P 10 units with manure

• Low testing field 5 ppm to 15 ppm
• Improved yield and forage quality
• Reduced erosion
• Lower runoff volume
• Very high testing field 50 to 60 ppm
• Very high testing field 500 to 510 ppm

27
What are my options? Follow the rules.
No application on frozen or saturated soils
No application on gt10 slope
Adhere to setback requirements
223 ppb P
28
What are my options

• Improve timing of applications
• Lower field P index
• Import less and export more P
• Follow the rules

29
Some philosophy

• It is a lot easier to avoid a problem then to fix
  a problem.
• The P index is best used as a educational tool,
  not a justification for more manure applications

30
(No Transcript)
31
(No Transcript)