Phosphorus and Phosphorus Management

1
Phosphorus and Phosphorus Management
2
Outline

• Introduction
• P Sources
• P Transport
• Environmental Concerns
• P Management
• Summary

3
Outline

• Introduction
• P-Crop Need
• P Forms
• P Cycle

• Reactions in Soil
• (fate of P)
• P Buffer Capacity

• P Sources
• P Transport
• Environmental Concerns
• P Management
• Summary

4
IntroductionP-Crop Need

• Plants need P for growth
• ATP
• DNA
• RNA

• P deficiency
• stunted and spindly
• purplish foliage (older leaves)

5
IntroductionP-Crop Need
Goal of soil testing determine crop need -
Examples of agronomic soil P tests Bray P1,
Mehlich III, Olsen
6
IntroductionP-Crop Need
7
IntroductionP Forms
AS RELATED TO CROPS, SOILS, AND FERTILIZERS

• Inorganic P
• Fertilizers, soluble P
• PO43-, HPO42-, H2PO4-
• Immediately available

• Organic P
• Manure, plant/leaf residues
• Inositol phosphates, nucleic acids, phospholipids
• Slowly available (needs to be mineralized to
  inorganic form)

8
IntroductionP Forms
AS RELATED TO CROPS, SOILS, AND FERTILIZERS

• Soil Test P
• estimates plant available P
• usually Bray P1 (in WI)
• expressed in ppm P (elemental P, not P2O5)

• Phosphate P2O5 (oxide)
• fertilizer recommendations and product analysis
  given in oxide form
• conversion factors
• 1 lb P 2.29 lb P2O5
• 1 lb P2O5 0.44 lb P

9
IntroductionP Forms
AS RELATED TO WATER QUALITY

• Particulate P (PP)
• definition P bound to eroded sediment or organic
  matter
• also called sediment-P
• Soluble P (SP)
• definition P dissolved in runoff (working
  definition P that passes through a 0.45 micron
  filter)
• also called dissolved P (DP), dissolved reactive
  P (DRP), and ortho-P
• Total P (TP)
• definition total amount of P, both PP and SP, in
  soil or runoff

10
IntroductionP Forms
AS RELATED TO WATER QUALITY

• P Concentration
• definition amount of P per volume
• expressed as mg P/L or ppm
• P Load
• definition total amount of P delivered
• expressed as mg P/ha (lb P/acre)

11
IntroductionP Cycle
12
(No Transcript)
13
IntroductionP Reactions in Soil

• Mineralization and Immobilization (organic P)

Immobilization
Fe3, Al3, Ca2
microbes
Organic P forms
H2PO4-
Fe, Al, Ca phosphates
microbes
insoluble fixed P
soluble phosphate
Mineralization
14
IntroductionP Reactions in Soil

• Adsorption and Desorption
• Clays, Fe and Al oxides, organic matter
• Precipitation/Dissolution
• Acid soils Fe, Al, Mn compounds dominate
• Alkaline soils Ca compounds dominate

What happens when fertilizer or manure P is added
to soil?
P is quickly and strongly bound to soil particles.
(inorganic P)
15
IntroductionBuffer Capacity

• P buffer capacity (indication of the rate of
  change of STP with additions or removals)
• Ave 18 lbs P2O5/acre to change STP by 1ppm
• (Leikam, 1992)
• Time is needed to raise OR lower STP

16
Outline

• Introduction
• P Sources
• Soil
• Plants
• Fertilizers

• Manures
• Livestock Feed
• Municipal Waste

• P Transport
• Environmental Concerns
• P Management
• Summary

17
P SourcesSoil

• P occurs naturally in soil (but usually in very
  low concentrations)

18
P SourcesPlants

• Vegetation can contribute P to runoff
• plants release P when tissue is ruptured due to
  freezing, thawing, and drying

19
P SourcesFertilizers

• Added to soil to increase fertility for crop
  production
• Common examples N-P2O4-K2O
• Monoammonium phosphate NH4H2PO4 11-48-0
• Diammonium phosphate (NH4)2HPO4 18-46-0
• Triple superphosphate Ca(H2PO4)2 0-46-0
• Easily soluble to runoff water
• (if rain comes shortly after application)

20
P SourcesManure

• Manure contains nutrients for plant growth,
  including P
• Manure applications improve physical properties
  of soil
• Manure applications can lead to buildup of soil P

21
P SourcesManure
Note Manure supplies approximately equal amounts
of N and P.
22
P SourcesLivestock Feed

• Farm animals need adequate protein, energy, and
  nutrition
• Dietary rations often contain excess nutrients,
  particularly P

23
P SourcesIndustrial and Municipal Waste

• Water discharged from wastewater treatment
  facilities
• Storm water runoff
• Biosolids

www.milorganite.com
24
Outline

• Introduction
• P Sources
• P Transport
• Runoff and Erosion

• P Leaching

• Environmental Concerns
• P Management
• Summary

25
P TransportRunoff and Erosion

• Runoff
• movement of water across the lands surface

• Erosion
• movement of soil particles by water

Runoff and erosion are SURFACE WATER quality
problems.
26
P TransportLeaching

• Leaching
• infiltration of water through soil to
  groundwater
• (low on most Wisconsin soils)

P leaching is a GROUNDWATER quality problem
27
P TransportLeaching
Nutrient and Pest Management Program
28
Outline

• Introduction
• P Sources
• P Transport
• Environmental Concerns
• Eutrophication
• Soil Test P

• Point/NonPoint Pollution
• Urban/Agricultural

• P Management
• Summary

29
Environmental ConcernsEutrophication

• Too little P land degradation
• Too much P eutrophication

What happens when a stream or lake receives more
P than it is used to receiving?
30
Environmental ConcernsEutrophication

• P moves from soil to stream
• P stimulates algae growth
• Too much algae blocks sun, uses oxygen
• Fish can die, stream health declines
• Odor, limits recreational uses, lowers drinking
  water quality

31
Environmental ConcernsSoil Test P
Accumulation of P as a result of inputs exceeding
removals
32
Environmental ConcernsSoil Test P
As soil test P increases, the amount of P
dissolved in runoff also increases.
Natural runoff from April through July on corn
plots at Arlington.
33
Environmental Concerns Soil Test P

• N-based nutrient management strategy

lbs/acre
N needs met, but as a result, twice as much P as
needed was applied.
160
320
120
60
45
34
Environmental Concerns Soil Test P

• P-based nutrient management strategy

lbs/acre
P needs met, but will need supplemental N AND
more acres to apply manure.
160
160
80
60
45
35
Environmental ConcernsPoint/Nonpoint Pollution

• Point source pollution Identifiable pollution
  discharge sources.
• Nonpoint source pollution Diffuse,
  hard-to-identify pollution sources transported by
  runoff and erosion from a widespread land area.

36
Environmental ConcernsUrban/Agricultural

• Urban sources of P
• lawns leaves, soil, fertilizer, animal
  droppings, plants
• wastewater
• biosolids
• Agricultural sources of P
• manure
• fertilizer
• crop tissue
• soil

37
Outline

• Introduction
• P Sources
• P Transport
• Environmental Concerns
• P Management
• Approaches to Improve P Balance
• Management to Reduce P Losses
• Summary

38
P Management - Improve P Balance
NPM Program
39
P Management - Improve P Balance

• Follow Soil Test Recommendations
• At optimum STP,
• recommended nutrients anticipated crop removal
• Soil test every 3-4 years

40
P Management - Improve P Balance

• Credit Nutrient Sources
• Credit manure P BEFORE determining supplemental
  fertilizer application rates
• Manure can supply crop nutrients as effectively
  as commercial fertilizers
• Need nutrient content and application rate
• Lab analysis or book value Calibrate!

41
P Management - Improve P Balance

• Use Starter Judiciously
• Recommendation for corn band apply starter
  fertilizer if needed (10 lb N, 20 lb P2O5, 20 lb
  K2O)
• On soils in the excessively high range for P,
  avoid starter applications in excess of 10-20-20

42
P Management - Improve P Balance
43
P Management - Improve P Balance
Manage Dietary P Goal avoid overfeeding P FOLLOW
DIETARY P GUIDELINES

• Dairy
• know P content of dietary supplements
• NRC recommends between 0.32 and 0.38P, depending
  on milk production
• Swine/Poultry
• improve efficiency
• consider feeding HAP corn
• consider adding phytase enzyme to feed

44
P Management - Improve P Balance

• Manage Dietary P

Phosphorus level in the manure is directly
related to the level of P intake.
P in diet
Source Powell et al, 2001
45
P Management - Improve P Balance

• Manage Dietary P

Dairy manure applied at 25 ton/a
Source Ebeling et al, 2002
46
P Management - Improve P Balance

• Manage Dietary P

One year after manure application, the cumulative
runoff dissolved P losses were significantly
higher from the plots with high P diet manure
compared to the low P diet manure and control.
Source Ebeling et al, 2002
47
P Management - Improve P Balance

• Increase land base
• Ensure all cropland receives manure sometime
  during the rotation
• Apply manure to rented land
• Obtain manure application rights from neighboring
  grain farmers

48
P Management - Reduce P Loss

• In order for P to reach surface water
• need both a SOURCE of P and MOVEMENT of P

49
P Management - Reduce P Loss

• Identify low risk sites
• Source and transport site specific
• P Index http//wpindex.soils.wisc.edu
• SNAP-Plus www.snapplus.net

50
P Management - Reduce P Loss

• Identify low risk sites
• Total Risk Index (PI)
• Soluble P Particulate P Acute P total P
  delivery ratio
• Needed for PI calculations
• -management, cropping rotations, tillage,
  fertilizer and manure applications, soil test P,
  slope, distance to surface water, etc.

51
Field Crop ID Orangecorn Greenalfalfa Yellowoa
ts(alf. Seed)
PI Values Redgt4 Orange3-3.9 Blue2-2.9 Violet1
-1.9
UW Platteville Farm 2004 Rotation
52
P Management - Reduce P Loss

• Consider seasonal limitations to manure
  applications

• Weather predictions
• Time of year

53
P Management - Reduce P Loss
Incorporate P fertilizer

• Incorporation of broadcast fertilizer with
  tillage
• OR
• Subsurface band placement

54
P Management - Reduce P Loss

• Incorporate manure??
• Runoff Dissolved P Losses

Spring Runoff
Runoff Dissolved P mg/L
Source Bundy and Andraski, 2001
55
P Management - Reduce P Loss

• Incorporate manure??
• Total P Losses

Spring Runoff
Total P load g/ha
Source Bundy and Andraski, 2001
56
P Management - Reduce P Loss
How does manure affect runoff P losses?
Surface Applied (not incorporated) -acts as a
mulch -provides surface residue cover -decreases
erosion -increases soluble P losses (especially
on no-till or alfalfa in the winter)
Incorporated -increases erosion -decreases
soluble P losses
Manure applications reduce runoff volumes and
soil loss
57
P Management - Reduce P Loss

• Use soil conservation practices
• Examples
• Changes in land management practices
• (cover crops, diverse rotations, conservation
  tillage, contour farming)
• Installation of structural devices
• (buffer strips, diversions, grade stabilization
  structures, grassed waterways, and terraces
• most widely adopted and easily accomplished

58
P Management - Reduce P Loss
Use soil conservation practices

• Reduces amount of runoff
• Reduces eroded sediment

59
Summary

• Soil Testing ensures adequate supplies of
  nutrients for crop production
• P Sources soil, plants, fertilizers, manures,
  livestock feed, industrial and municipal wastes
• P Transport occurs through runoff, erosion and
  leaching (usually insignificant in WI)

60
Summary

• Eutrophication of surface water is the main
  phosphorus pollution issue

IMPROVE P BALANCE -Follow soil test
recommendations -Credit manure P -Use starter
only if needed -Reduce P in diet -Increase land
base for spreading
REDUCE P LOSS -Use PI to determine low risk areas
for manure application -Watch the weather
forecast -Incorporate P fertilizer -Use soil
conservation practices
61
Take Home Message

• Keep P in the field!
• -for crop use
• -out of surface water