Copyright is owned by the Author of the thesis. Permission is given for
a copy to be downloaded by an individual for the purpose of research and
private study only. The thesis may not be reproduced elsewhere without
the permission of the Author.
OF PHOSPHORUS IN SOILS
A thesi s presented in part ial fulfilment of the requirements f o r the degree of Do c t o r of Philosophy in Soil Science
at Masscy University
Alexander Marinns Dick Rennes 19 78
i
ABSTRACT
Low and stab le concent rat ions of phosphorus (P) fo rms and sediment were ob tained in s t ream flow from two small , adj acen t , s crub -covered , and minimal ly-disturbed cat chments near Palmerston North , New Zealand .
In c ontras t , higher and i r regular concent rations and loadings were ob t a ined follmving land c learing , P fertilizer appl i cation , and the es t ab lishment of grazed pas t ure . The need for intensive s tream
s amp l ing , as wel l as comp l e te hydrograph data i� order to ob tain re liab le info rmation on s tream loadings , is emphasised .
High and fluctuat ing concent rat ions of P forms and sediment were ob tained fo llm.;ring the change in land us e . A high proport ion o f the P and s ediment loss ·occurred in the s torm runof f component of s t ream flow . The e s t imated losses o f fer t ilizer P in s t ream flow ( approximately 1%
o f that added) were very small from an agronomic s tandpoint but they rep res ent large p ropo r t ional increases in the loadings of P forms in s t ream flow .
The high amounts of wa t e r-extrac t able P present in the soils of the cat chment (field soils) , immediately follov1ing the aerial app lication o f fert i l izer P , declined rapidly to lower , more s tab le values . This pa t tern o f de c l ine for field soils was repl icated using small pots es tablished in the field (po t soils) and containing fer tilized soil representative o f the cat chments . Close correlations were ob tained b e tween wa ter-extrac tab le P in th e upper lcm of field and pot soils , and mean dissolved ino rganic P (DIP) conc�ttrat ions in the s urface runoff componen t of s tream flow in closely·-follm.;ring storms . The possibil i ty of predicting DIP losses in
surface r uno ff from soils us ing a water-ext raction technique is thus indicated .
The decrease with t ime in th e amounts of water-extractab le P ob served a f ter superpho sphate addi tion to field and pot soils was
rep roduced in the l ab oratory . This relat ionship validated the use o f lab o ratory s tudies to examine the rate and extent o f int e raction o f fer t ilizer P occurring in fiel d soils and t o predict the potential movement of fertilizer P from s oils to watzrs .
The decline in water-extrac tab le P clos ely paral leled the decreas e in p lan t uptake of P with time following fertilizer ? addition to two cons trast ing soils . This sugges ted that water extract ion may be a
useful soil-tes t ing p rocedure for predic ting P availab i l ity to plants , as wel l as the movement of P in surface runo ff from soils .
The rate of decline in water-extractab le P in a g iven soil was proportional to bo th the amoun t of P added and the amount init ially ext rac tab le immedia tely fol lowing P addi tion . Th is sugge s t s tha t the rate and exten t of P sorpt ic� in a soil is directly re lated to soil solut ion P concen t ration. Di f fprences were obtained , howeve r , between three contras ting soils in th e relative rate and extent of P sorpt ion .
A kinetic model based on the Langmuir equation was developed to s imulate the decline in wa ter-ext rac tab i li ty of P added to three soils . Three popula tions of sites were assumed and the approp riate sorp tion maxima and b inding energy cons tants were derived from sorp tion isotherm studies . The model provi ded a satis factory predic tion o f the fate of different amounts of fer t ilizer P. I t i s probable that the further deve lopment of this mo del would provide a useful bas i s for predicting the fate of P added to soils an d the potential movement of added P in surface -runo ff wa ters .
ACKNm-lLEDGEMENTS
I would like to express my gratitude to a numb er o f people without . whos e help and support this thes is would never have eventuated . In
,par ticular I would l ike to thank:
My s upervisor , Professor Kei th Syers , to whom I am deeply indeb ted for his b o uyant enthusiasm , encouragement , and friendship . Further to
iii
this , his rigorous s t andards of scientific tho roughness and presentat ion , whi l e somet imes try ing , have b een highly rewarding .
Mr. Russell Til lman , to whom I am part icularly grat eful for h�_s friendship , patience , and continual assis tance during the planning , execution and presentat ion of this study .
Other members o f the Department o f Soil Science s taff , both teaching and technical , and my colleagues who provided assis tance and good humour .
Julie , for her patience over the long duration of the st udy and her foreb earance of difficult ies .
Dianne , for producing firs t-class typesc r ipt .
The Univers ity Grants Co�ni t t ee for a pos t-graduat e scholarship for three years .
The Facul ty o f Agricultural and Hor t i cul tural Science , Massey University , for a Massey pos t-graduate s cholarship .
The Waikato Val ley Autho rity for time and encouragement to complete thi s thes is .
TABLE OF CONTENTS
ABSTRACT . • • . •
ACKNO��EDGEMENTS TABLE OF CONTENTS LIST OF FIGURES LIST OF TAB LES •
CHAPTER 1
REVI EW OF LITERATURE
1 . 1 Impor tance of Phosphorus Forms and Concentrations in Surface Waters
1.2 Fac tors Influencing Phosphorus Enrichment of
Surface Waters . . . . . . . . . . . . . . . 1 . 2 . 1 Nat ural or background phosphorus concentra tions 1 . 2 . 2 Urb an land use .
1 . 2 . 3 Rural land us e . . . . . . 1 . 2 . 3 . 1 Forestry
1 . 2 . 3 . 2 L ives tock farming 1 . 2 . 3 . 3 Cropping . . . . . .
1 . 2 . 3 . 4 Fertilizer . . . . . . . . . 1 . 2 . 4 Re lative impo rtance o f fac tors influencing the
phosphorus enrichment o f waters . . . . 1 . 3 Movement o f Phosphorus from S o il s -to Surface l.Jaters
1 . 3 . 1 So urces o f water and phosphorus 1 . 3 . 1 . 1 S urface runo f f
1 . 3 . 1. 2 S ubsurface runo f f
1 . 3 . 2 Poten t ial in fluence o f changes in land use on phosphorus movement to wat er .
1 . 4 Forms and Reactions of Phosphorus in Soils . 1 . 4 . 1 Organic phospho rus in soils
Page
.:. i iii iv ix xvi
1
1
. 4
4 7 8 8 . . . . 10
11
1 3
16 17 1 7 19 20
. . . . 2 1 2 3 . . . . 2 3
1 . 4 . 2 Inorgan ic phosphorus in soils • . • • • • 1 . 4 . 2 . 1
1 . 4 . 2 . 2 Primary inorgani c phosphorus • . Secondary inorganic phosphorus
1 . 5 Modelling the Reactions and Reac t ion Rates o f Phospho rus
V
Page
2 5 25 26
Added to Soils and the Movement o f Phospho rus from Soil s . . 2 9
1 . 6
1 . 5 . 1
1 . 5 . 2 1 . 5 . 3
React:i.ons • • • • • • •
1 . 5 . 1 . 1 Iso therm resolution o f data 1 . 5 . 1 . 2 Reaction mechanisms
Reac t ion rates
Predic t ion o f phosphorus movement from soils and ca t chmen ts to water . . General Conclus ions and Research Needs
CHAPTER 2
29 2 9 3 1 35
4 1 44
GENERAL MATERIALS &�D METHODOLOGY . 4 7
2 . 1
2 . 2 2 . 3
2 . 4 2 . 5
Des cription o f the Cat chmen ts 2 . 1 . 1
2 . 1 . 2
Topography , geo logy , and soils Vege t a t ion and land clearing Moni toring Equipment .
Sample Co lle c t ion . • 2 . 3 . 1
2 . 3 . 2
Water samples Soil s amp les Analytical P ro cedures Data Processing
CHAPTER 3
MOVElfr:NT OF WATER, SEDIMENT, AND PHOSPHORUS FORMS FROM 'fWO SMALL, ADJACENT CATCHMENTS UNDER CHANGING LAND USE
3 . 1 Introduc t ion . . . . 3 . 2 Materials and Me thods
47 47 50 5 2 5 6 56 5 6 5 7 5 7
5 9 5 9 6 1
3 . 3
3 . 4
Res ul t s and Discuss i on • .
3 . 3 . 1 3 . 3 . 2 3 . 3 . 3
Flow-concen t ration relat ionships •
Sources o f water , s ed iment , and phosphorus forms . Impac t o f l and clearing and changing land us e on sediment and phospho rus movement
3 . 3 . 3 . 1 Movement of sediment and particulat e phospho rus . . • • • • • • • •
3 . 3 . 3 . 2 Movement of dissolved inorganic and
Page
64
64 FJO
74 74
organic phosphorus • • • • • • • • • • • 85 3 . 3 . 4 Influence o f phosphorus fertilizer on the
movement o f phosphorus forms from the cat chments • 9 5
General Discuss ion . • • . • • 106
CHAPTER 4
FATE OF APPLIED PHOSPHORUS AD:9ED TO SOILS AND
MOVEMENT IN RUNOFF WATER 4 . 1
4.2
4 . 3
Introduc t ion • . .
�fute rials and Me thods 4 . 2 . 1
4 . 2 . 2
'•. 2 . 3
Preliminary inve st igat ion De tailed inve st i�a t1on Supplementary s tudy
Re sul ts and Discuss ion . . •
4 . 3 . 1 Changes in water-extrac tab le pho s phorus in s oil from fer t i lized and control field sites within
1 1 2 1 1 2
. 1 1 3 1 14 1 17 1 19 120
the catchments . • . . . : • • . • • • 1 20 4 . 3 . 2 Char.ges in water-extrac tab le phospho rus in soil
from fertilized and contro l pot s in the field 4 . 3 . 2 . 1
4 . 3 . 2 . 2
4. 3 . 2 . 3
Trea tment di fferences and phospho rus movemen t from the upper lcm • • . • RelaU.onships b e t'fieen water-ext rac tab le pho sphorus data obtained for soils from fertilized field s i tes and pots
Regenerat ion of the >vater-ext ractab le phosphorus pool in soils . . • • . • •
1 30
130
134
136
' 4 . 4
4 . 3 . 3 Relationships b etween mean dissolved ino rganic phosphorus concentrations in surface runo f f and water-extrac t able phsophorus values ob tained for s o i l s from fer tilized field s ites and pots .
General Discus s ion . • .
CHAPTER 5
THE RATE AND EXTENT OF PHOSPHORUS REACTIONS IN SOILS .
5 . 1 5 . 2
5 . 3
Introduc tion .
Mat erials and Me thods 5 . 2 . 1
5 . 2 . 2 5 . 2.3
5 . 2 . 4
5 . 2 . 5 5 . 2 . 6
Comparison of extraction techniques to est imate lab ila phospho rus in soils
Soils used in sub s equent laboratory s tudies Prel.iminary labora tory s tudies of the
decl ine in wa ter-extrdc t ab le phospho rus fo l lowing phosphorus add i t i on to one soil Laboratory and glasshous e studies of the decline in wa te r-e·�:tractable and plant
availab le pho spho rus in contrasting soils fol lmling phos pho rus addi tion
Comparisons between solid and l iquid additions of phosphorus to so ils . . . . . . . . . • • . Detailed s tudies o f the decline in
wate r-extractab le pho sphbrus in soils
Results and Discussion . . . • • 5 . 3. 1
5 . 3 . 2
Comparison of extract ion techniques De cl ine in water-ext rac tab le phospho rus fo llowing phosphorus addition to one soil
Page
1 4 3 150
159 159 16 1
16 1 1 6 1
162
164
165
166
1 7 1 1 7 1
1 7 1 vii
5 . 3 . 3
5 . 3 . 4
5 . 3 . 5
Decline in water-ext rac t ab le and p lant ava i lab le phospho rus i n cont ras t ing soils following phosphorus addit ion . • .
5 . 3 . 3 . 1
5 . 3 . 3 . 2
Characteri st ics o f the. decline in water-extrac tab le phosphorus in soils of contras ting
phosphorus so rp t ion properties Dec line in water-extractab lility o f phosphorus in soil and the availability o f phosphorus to plants . . . . . . . . . . . . Infl uence o f solid or dissolved phosphorus addition to soil on the decline in water
ext rac tab le pho spho rus
Det ailed s t udies of the decline in water
extr actab le pho spho rus in soils and an approach to modelling soil phosphorus rea c t ions .
5 . 4 General Discussion . • . • • • • • • • •
SUMMARY ru�D CONCLUSIONS BI BLIOGRAPHY
APPENDICES . .
Page
1 7 5
1 7 5
1 79
188
19 2 207
216 2 19 2 38
FIGURE 2.1
2 . 2
LIST OF FIGURES
Map o f the North Is land o f New Zealand showing the general location of the study area in the inset • . • • • • Map o f the s tudy area ( f rom inset on Fig . 2 . 1 ) showiP.g location o f ca tchments ( circle) , local drainage networks , and indicating topography 2 . 3 Vertical aerial photography o f the two
catchments before ( A) and af ter (B)
2 . 4
2 . 5
2 . 6
3 . 1 3 . 2
3 . 3
clearing
Vertical aerial pho to graph of the two catchment s showing cleared slopes and deb ris deposition fol lowing clearing • • Ground p hotograph in the 2 2-ha catchment after c l earing showing soil surface disturb ance s, steepness o f s lopes , and deb ris in s t ream channel . . . • • H-S flume and S tevens F- type flow
reco rder opera t ing on th e s tream draining the 6 -ha catchment . . . . . . • • • • . Componen ts o f a stream hydrograph
Varia tion in f:�w and concentrat ions o f PP and sediment in s torm discharge from
the 2 2-ha catchment during the s torm
event o f 24-2 5 / 6 / 19 74 before land clearing Variation in flow and concentra t ions o f PP and s ediment in storm discharge from the 2 2-ha ca tchment during the s torm event o f 26/5/ 19 7 5 after land cl earing . 3 . 4 Variation in mean concentrations o f
sedimen t and PP in the s torm dis charge of succ es sive s torm even ts throughout 19 74 , 1 9 7 5 and 19 76 for the 2 2-ha
3 . 5
catchment . .
Variat ions in mean concentrat ions of sediment and PP in s torm discharge of successive s torm events throughout 19 74 and 1 9 75 for the 6-ha cat chment . . • •
ix
Page
4 8
4 9
5 1
5 3
54
55 63
65
67
6 8
FIGURE 3 . 6
3 . 7
3 . 8
3 . 9
Variation in flow and concentrations of DIP and DOP in s torm discharge f rom the 2 2-ha cat chment during the s torm event o f 24-25 / 6 / 1 9 74 before land clearing Variation in flow and concen trat ions of DIP and DOP in s to rm dis charge frcm the 2 2-ha catchmen t during the s torm event of 26 / 5 / 19 75 after land clearing Variation in mean concentrations of DIP and DOP in the storm dis charge of successive storm events throughout 19 74 , 1 9 7 5 , and 19 76 for the 22-ha catchment . . . . . . . . . . Variation in mean concen t rations o f DIP and DOP in the storm dis charge of succe s s ive s torm even ts throughout
1 9 74 and 19 75 for the 6-ha catchment . 3 . 1 0 Influence o f fertil izer P applicat ion
on the varia tion in mean concent rations o f DIP (A) and PP (B) in the s torm discharge o f succes sive s torm events from two a dj acent ca tchment s , both of which we re fertil ized in 19 75 but only one of which was fertilized in 19 76 . • 3 . 1 1 Re gression b e tween mean concen trations
of DIP in s torm flow from the 22-ha and 6-ha cat chments in 1 9 75 (both catchments fer tilized) and in 19 76
(6-ha catchment only fertilized) . 3 . 1 2 Regression b e tween mean PP and s ediment
concentra t ions in s torm flow from the 6-ha catchment (A) and the 2 2-ha
4 . 1
4 . 2
catchmen t (B) in 19 76 fol lowing fer tilizer addition to the 6-ha catchment only • • · Plan of the t �o catchemnt� showing the loca tion o f 6 sites for soil sampling in
1 9 75 (A, B, C , D , E , and F) and the three transect l ines for placement of po ts to estima te the mean superphosphate application rates in the catchment s . • . • • • Transverse s ection o f the th ree t ransect l ines shown in Fig. 4 . 1 showing the lo ca tion o f pots p l aced in the ca tchmen ts to estima te the applica t ion rate o f s uperphosphate . .
Page
6 9
7 1
8 7
8 8
9 7
9 9
1 05
l 1 5
1 16
FIGURE 4 . 3
4 . 4
4 . 5
4 . 6
4 . 7
4 . 8
4 . 9
Decline in water-extrac tab le P in soils with time following ferti l izer P addit ion
at three fer t i l i zed s ites and f rom three control s ites in 19 75 . . . . • •
Decl ine in wat e r-extrac tab le P in soils with t ime fo llmv-ing ferti l izer P
addition at three fertilized s it �s and f rom three cont rol s i tes in the 6 -ha catchment only in 1976 . . .
Decline in wa ter-extrac tab le P in soils with time fo l lowing fertil izer P
addit ion at three fertilized sites in the 6 -ha ca t chment only in 1 9 76 and three fertilized s ites in both catchments in 19 7 5 • • • • • • • • • • • • • •
Relative wa ter-ext ractab il ity of P , expressed as a p roportion of the init ial extrac tion val ue , with time fo llowing fertilizer P addition at three fertil ized s i tes in the 6 -ha catchment only in 19 76 and th ree fe rtil ized sites in both
cat chments in 1 9 7 5 . . • . • • • .
Decline in wa ter-extrac tab le P with time , following fert i l izer P addition , in soil f rom field pots . • . • . . .
Relative water-extractab i l ity of P , expressed as a p roport ion of the initial extract ion value , with time following fert ilizer P addition to soil in f ield
pots . . . . . . . . . . . . . . . . . . Field pots invo lving "divided" soil
treatments showing condit ion at t ime o f fertilizer placement an d after 40 days in the field . . . . . . • . . • 4 . 10 Decline in wa te r-extractab le P with
t ime , fol lowing fer tilizer P addit ion , in soil from fertilized s i tes in the f ield and po ts in the field . . . . . • 4 . 1 1 Regress ion between wa ter-extractab le
P in soil from fertilized field s i tes ( B) and from surface 2-cm po t treatment (A) . All data for the 6-ha cat chment in 1 9 76 .
xi Page
124
1 2 6
1 2 7
129
1 3 1
1 3 3
1 35
1 3 7
1 38
FIGURE 4 . 1 2
4 . 1 3
4 . 1 4
4 . 1 5
Regress ion be tween water-extractab le P in soil f rom fer t i l i zed field sites ( B) and f rom mixed pot t reatment (A) •
All data for the 6 -ha cat chment in 19 76 Regres s ion between DIP concentrat ions in the leachates f rom 20 pots (mixed treatmen t after 7 months in the f ield) ob tained by succes s ive l each ings
Relat ionship between mean DIP
concentra t ions in the surface runo ff component of s t o rm flow from the two cat chments and >lat er-ext ractab le P in soil from fertilized field sites in 19 7 5 • • • • • • • • • • • • • • • • • Regress ion b e tween mean DIP
conc en trat ions in the sur face runo ff componen t of selec t ed storm flow and wa ter-extrac tab le P in soil f rom fert ilized field s i tes in 1 9 75 . 4 . 1 6 Relationship be tween mean DIP
concentrations in the surface runo ff components of st.orm flmv f rom th·e 6-ha cat chmen t an d wa ter-extractab le P in soil f rom fert ilized field s i tes in the 6 -ha catchment in 19 76
4 . 1 7 Regression be tween mean DIP
concentrat ions in the sur face runoff component of s torm f l ow f rom the 6-ha catchment and water-extractable P in so il from fert ili zed field s ites in the 6-ha catchmen t in 19 76
4 . 18 Re gress ion between mean DIP
concentra tions in the surface runo f f component o f s torm flow and water
extrac tab le P in soil from fertilized field sites in th e 6-ha catchmen t, comb ining 19 75 and 1 9 76 data . . . . 4 . 1 9 Regression between mean DIP
concentrations in the surface runo ff component of storm flov7 f rom the 6-ha cat chmen t in 1 9 76 and water
extrac tab le P in s o il from surface 2-cm pot treatments . . . . . . 4 . 20 Regression be tween mean DIP
concent rations in the surface runo ff component of s torm f low f rom the 6-ha cat chment in 1 9 76 and v.rater-·
extractable P in s oil from the mixed pot t reatmen ts . . . . . •
Page
1 39
1 4 2
144
146
14 7
148
149
152
1 5 3
FIGURE 5 . 1
5 . 2
5 . 3
Regression b e tween water-extrac tab le P values ob tained in two sequential water extractions ( each of 1 hour duration at a soil : solution ratio of 1:40) (B) and in one water e xtrac tion ( 1 7 hours duration and at a soil : so lution ratio
o f 1 : 400) (A) • • • • • • • • • • • • • • • • • • • Decline in water-ext rac tab l e P ( two
1 -hour extractions at a soil : solut ion ratio o f 1 : 40) with time f rom soil incub ated in pots following fer til izer P addition . • . . • . • • . • • • Re lative water extrac tab ility of P , expressed as a propo rtion o f the initial extrac tion value , with t ime fol lowing P addition at three rates 5 . 4 Decline in water-extractab le P in
catchmen t field soils and in incubation pots of the same soil fo llowing fertilizer P addition . . . . . . . • . •
5 . 5 Dec line in water-extrac tab le P from Pahiatua and Egmont soils with t ime following incubation and fe rtiliz er P addition . . . . • . • • •
5 .6 Decline in wa ter-extractab le P from Pahiatua soil with time fol lowing incubation and fer!:ili.z er P addition 5 . 7
5 . 8
5 . 9
5 . 10
5 . 1 1
Decline in water-ex�ractab le P with t ime fol lowing fertilizer P addition and incubation of Egmont soil . . . . Decline in recovery o f P f rom Pahiatua s oil with t ime fol lowing s uperphosphate
addition and incub ation . . . . . · • . . . . . Regression b etween plant up take of P
f rom Pahiatua soil following superphosphate addition and incub a t ion , and amo unts of extractab le P . . . . . . . . . • . • Decline in recovery of P from Egmont soil with t ime fo l lowing supe rphosphate addition and incubation . . • . • . • . Regres s ion between p lant uptake o f P f rom Egmont so il samples following superpho sphate addition and incuba tion , and amo unt s of extrac tab le P . . . • •
xiii Page
1 7 2
1 7 3
1 74
1 7 7
1 78
180
18 1
1 8 3
. 184
185
186
FIGURE 5 . 1 2 Regression between p lant up take o f P from Pahiatua and E gmont soils f o llm.ring superphosphate addition and incuba tion ,
and extra c t ab le P . • • • • • • . • . • • • . • • • • 1 8 7 5 . 1 3 Decline in recovery of P f rom Pahiatua
soil with t ime following ro ck phosphate
addition and incubation . . . • • . • • • • • . . . . 1 89 5 . 1 4 Decline in recovery of P f rom Egmont
soil with t ime following rock phosphate
addition and incubation • • • • • . • • • • 1 9 0 5 . 1 5 Decline in water-ext rac tab le P f rom
Pahia tua soil with t ime following _1 fertilizer P addition at 75 � g P g
in sol id and liquid forms . . . . . • • • • • • • • • 19 3 5 . 1 6 Decline in water-ext rac tab le P f rom
Pahia tua soil fo l lowing fertil izer P
addition and incubation . . • . . . • • • • • . • . . 194 5 . 1 7 Decline in wa ter-extrac tab le P with
time f rom Pahiatua soil following fertilizer P addition and incubat ion
5 . 1 8
5 . 1 9
5 . 20
at three rates o f addition
Decline in water-ext ractable P with time from Dannevirke soil following fer tilizer
P addition and incub ation at two rates of addition . . . . . . • . . • . . De cline in water-ext ractable P with time from Egmont soil fo l lowing fertil izer P addition and incubation . . . . . . . • • Decline in relative water ext rac tability of P , expressed as a proportion of the ext raction value ob tained a f ter 40 hours , with time fo llowing fer tilizer P
addition and incub ation . .
5 . 2 1 Schematic representation o f th e p roposed reac t ion mechanisms invo lved in P
• . . . . . 195
. . . . . • 19 6
• • • • • • 1.9 7
• . • • . . 199
sorp tion and desorption . . . . . . • . • • . • • . . 205 5 . 2 2 Predicted (---) and measured (---) decline
in the amo unts o f \vater-ext rac tab le P in Pahiatua (a) , Dannevirke (b), an d Egmont (c) soils with t ime a f ter fer tilizer
P addit ion . . . . . • • • • • • • • . . . . • 206
FIGURE 5 .2 3 Predicted ( ---) and measured (---) decline in the amounts of water-extrac tab le P in Pahiatua soil -.;.lith t ime after fertilizer
5 . 24
P addition at ra tes o f 150 � g P g- 1 (a) and 7 5 � g P g-1 (b) . • . . . . • . • • • • Predic ted (---) and measured ( ---) decline in the amounts of water-extrac tab le P in Dannevirke soil with t ime a f t er fertilizer P addition at rates of 150 � g P g- 1 (a) and 75 � g P g- 1 (b ) . . . . • . • . . •
?. 2 5 Predicted ( ---) and actual ( ---) decline in the amounts of water-extrac tab le P in Egmont soil with time after fertilizer P addition at rates of 150 � g P g- 1 (a) and 75 � g P g- 1 (b ) • . •
XV
Page
208
209
2 10
LIST OF TABLES
TABLE 3 . 1 Flow from the 22-ha and 6-ha cat chments for the years 1 9 74 , 1 9 75 , and 1 9 76 , showing total annual
Page
outputs of four fo rms of flow . . • • • • • 7 2 3 . 2 Dis charge o f water , sediment , particulate P (PP) ,
and total P ( TP) , from the two catchments in annual s t ream flow b efore land clearing ( 19 74) and following
cl earing and fertilizer applicat ion ( 1975 and 1 9 76 ) 7 7 3 . 3 Discharge o f water , sediment , particulate P (PP)
and total P (TP) from the two catchments in annual st ream flow within storm events be fore land cl earing
( 1 9 74) and fol lowing clearing and fer tilizer
applica t ion ( 1 9 75 and 19 76) .. .. . . . . . • • . • 80 3 . 4 Discharge of wa te r , sediment , par ticulate P (PP)
and total P (TP ) from the two catchments in annual storm flow b e fore land clearing ( 1 9 74 ) and following
clearing and fertilizer applica t ion ( 1 975 and 1 9 7 6) 82 3 . 5 Discharge o f water , sediment , par t iculate P (PP) ,
and total P ( TP) from the two catchments in annual subsurface f low before land clea ring (19 74), and following clearing and fertilizer applica tion
( 1 9 75 and 1 9 7 6 ) . . . . . • • • . . • • • • • • . 84 3 . 6 Disch arge of wa ter , dissolved ino rganic P (DIP ) ,
disso lved o rganic P (DOP) , and to tal P (TP)
from th e two catchments in annual s t ream flow b e fore land clearin g ( 1 9 74) and following c learing and
fer tilizer app lication ( 1 9 75 and 1976) . • . • • . 9 0 3 . 7 Discharge o f water, dis solved inorganic P (DIP ) ,
dis so lve d organic P (DOP ) , and total P (TP) from the t-vm catchments in annual s t ream f low v7ithin s torm even ts before land clearing ( 1 97 4 ) and fol lowing
clearing and fertilizer applica t ion ( 1 975 and 19 76) • 9 2 3 . 8 Discharge o f water , dissolved inorganic P (DIP) ,
dissolved o rganic P (DOP) , and total P (TP) from the two cat chments in annual st orm flow b efore land clearing ( 1 9 7 4 ) and fol lowing c learing and
fertilizer application ( 19 75 and 1 9 7 6 ) • • . . • 9 4 3 . 9 Discharge o f water , dissolved inorganic P (DIP) ,
dis so lved organic P ( DOP) , and to tal P (TF) f rom the t�>lo cat chments in annual sub surface flmv before land clearing ( 1 974) and following clearing and
fertilizer app lication ( 1 9 75 and 19 7 6) . . • . . • 96
TABLE 3 . 10 Mean concentra tions o f particulate P (PP) and sediment , and amounts o f PP associated with sediment in annual storm flow from the 2 2-ha and 6-ha catchments in 19 74 (before c learing) and in 19 75 and 19 76 ( following
xvii
Page
clearing and fert ilizer application) • . • 102 3 . 1 1 Losses o f P forms and sediment from fertilized
( 6 -ha) and unfer tilized ( 2 2-ha) catchments in 1 9 76 showing los ses per hec tare , proportions of P forms lost , and mean concentrations in
annual s t o rm discharge . . . • • • • • • • . . • • • 1 0 3 4 . 1 Application rate o f fertilizer P at the soil
s urface ob tained from samp ling con tainers s urrounding six potential soil-sampling sites
in the preliminary inves t iga t ion of 19 75 • . • 1 2 1 4 . 2 Amounts o f wa ter-ext rac tab le P in soils from
s ites A , C and F ( Fig . 4 . 1 ) and control si tes on 24 / 3/ 19 75 (before fert ilizer app lication) and at various times after fertili zer �vas applied on 5 / 4 / 19 75 . . • • • . • •
4 . 3 Regress ion ana lyses between amounts of water
extrac tab le P in soils and mean DIP
concentrat ions in the s urface runo ff component of stream flow for the two catchments during
5 . 1 5 . 2
5 . 3
5 . 4
the two years of s tudy • • • • . • Background data for three soils used in laboratory s tudies • • . . . • .
Correlat ion coef ficients b e tween p lan t uptake of P after 50 days growth in Pahia tua and Egmont soils fertili zed with superphosphate
and rock phosphate, and amo unts of wa ter-ext rac table P and Olsen-extrac tab le P • . • . • . • • • . • Amounts o f total "na tive" P, determined us ing
3 2p , and the amounts of P present in each region , calculated from solution P concen trat ions at equilibrium wi th no P addition and the Langmuir equat ion for each region • • • • • . Sorp tion constants desc rib ing the three ( I , II, and Ill) regions of P sorpt ion for th ree soils ; K and b are the equilibr ium cons tant of reaction and the sorption maximum , respec tively , for a par ticular region . • . • • • . . • . . • • • . •
1 2 3
15 1 1 6 3
1 9 1
200
20 1
