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LEACHING AND SURFACE RUNOFF LOSSES OF SULPHUR .A.ND
POTASSIUM FROM A TOKOHARU SOIL
A thesis present ed i n partia l fulfilment
of the requir -2m e.nts for the De gree of
Master of Pnilosophy in So il Science a t
Massey University
Christine M. SmHh
197 9.
n - ii
ABSTRACT
Sulphur and potass:it:m surface ar.. d subsurface drainage water losses from grazed pastures on a yellow-grey earth soil , the Tokomaru silt loam, -..:ere investigated j_n field e,:periments . Runoff losses from undrained c.r..
This fielJ stucly i llu s trates that S0 4 -S is readily lea ched in the Tokorr.n:.: ,; f:: ilt loam . Losses i n tile drairn1 ge w;:i t e rs occurred from all. dcpU1s abov'°'! the mole dtains (i.e. 45 cm depth) d uring indivi d ual iJ.:::,;; c,:cnt:s . On avcra;·;;c 7 . 5 kg dissolved S01,-S ha- 1 r,;as lost L ~om the two non-irrigat ed past ures fertilised in spr i ng . An a dditional 6.7 kg
"0., 4 - · ,C:, •na ·- l 1,:as uiscn.axgel:.l • ' ..l 1.n• t i ' 1 e d ra1.nag(?. . waters £ rorn two irribat ec l 1 pastures f er t i lised in spring (j .e. tota! 14 . 2 kg S04 -S h a - ).
Evidenc.:e :i..ndicated t hat S0 4 -S may have bypassed the drains in w;.iter SE~e ping b ey<.Hl ~· ~ appll.ed i 11 c.1.u t u1nn but net leacl1ed in tile d~2inage ~vat ers, ,,a s i:ecr,ver('. (in r.c;} at ion to annual pasture S requirements) will have occurred from pastures irrjg3tcd the precedir,g sunm1cr and/or f ertilised in autumn. Sulphm:· .r crt:ilisation in autumn and winter i s not recommended. Under the c: onaitions lil~cly to prcv2.il at this time an appreciable fraction of th·~ il.pplied S ma:• be lost in drainage wa ters. Resulls of this study indicate that leaching is not an i mpo rtant Kloss process in the Tokom.aru s ilt lonm. Dissolved K l eaching losses fro:n p;istures fertilised in spring or autumn averaged 4.66 and 4 . 05 kg Vr, ha -1 re~pec: t :i.ve• 1 y. Pc t assium surface runoff losses are generally of no consequence. In 1976 only 1.1 kg K ha- 1 was lost from an undrained pasture 1 f ert:i.lised (50 kg K ha- ) in spring, whilst 0.3 kg K ha- 1 was disc.h:: rg~d -from the aGsociatcd drained plot. A minimal fraction (3%) 1 of the K applied in autumn (50 kg K ha- ) to an undrained plot was lost in surf&cc runoff. Less than 1% of thcr-t applied was discharg<::d from the associated dr~ined plot. Throughout 1977, on aver age, 1.35 kg K ha- 1 WdS discharged f:rum uc:drainecl plots fertilised (57 kg K ha- 1 ) in S?l'.:i.ng. A(l. additionel 3 . 7 5 kg K ha -i was lost from pastures fertilised (55 kg K l,a - 1 ) i r1 autumn. R~infall K ad:litions ro~asured ever a five l!lonth interval jn l 977 iv 1 were low (total 1.4 kg K ha- ). However, because of the trend for K concentrations to vary on a seasonal basis it was concluded that K received in rainfall throughout 1977 was likely to largely offset total drainage water losses from undrained and drained pastures. The results indicate that K deficiencies in pasture on K retentive yellow-grey earth soils are not attributable to drainage water losses. Regression analyses showed that S0 4 -S concentrations in leachate, but not S0 4 -S loadings , were significantly related to water soluble soil S0 4 -S levels (0-40 cm), determined at frequent intervals during the drainage season, if the quantity of water percolating through the soil is measured, No relationship was found between measured water soluble or annnonium acetate extractable soil K levels and leachate K concentrations or loadings . ACKNOWLEDGEMENTS I wish to express my thanks to Dr P.E.H. Gregg, Department of Soil Science, Massey University, who suggested this study and gave helpful advice, criticism and encouragement during all stages of the proj ect. Thanks are a lso extended to Mr R. Tillma n of the Soil Science Department, Massey University, for help and advice, and to J . Macintosh for his assis tance with the field work. My s i ster, Julie ' s assist ance with the f i gur es , and my mother ' s support throughout, are much appreciated . Finally, my sincere thanks to Mrs E. Hart s tone who so ably typed the manuscript . TABLE OF CONTENT S Page ABSTRACT ACKNOWLI:DG[h"CNTS TABLE OF CONTENTS LIST OF PLATES LIST OF FIGURES LIST OF TABLES CHAPTER I INTRODUCT ION 1 CHAPTER II REVIEW OF LITERATURE 3 II. 1 SULPHUl~ REVIEW 3 II. 1 . 1 THE SULPHUR CYCLE IN GRA Z[D PASTURES 3 II.l . 1. 1 Soil Sulphur 3 II. 1. 1.1 . 1 The readily plant avallabl e soil so~-s pool 3 11. 1.1.1 . 2 Organic soil sulphur 5 II.1. 1.2 The plant sulphur pool 6 I!.1. 1. 3 The ani~al sulphur pool 6 II. 1. 2 SULPHUP- LOSSES FRO:~ THE C'YCLE 7 ., II.1 . 2.l Sulphur dra inage water l osses I II.1. 2. 1.1 Sulplrur l eaching l osses in laboratory and glasshouse studies 7 n .1. 2 . 1. 2 Sulphur l eacr~ing l osses l yslmet er studies li 11.l .2.1,3 Sulphur drainage wa t er losses in field studies 14 II.1.2.1.4 Conclusions 17 lI.1. 7. . 2 Sulphur immobili sat i011 los ses 17 II.1. 2 .3 Sulphur volatilisation losses 18 II.1.2,4 Sulphur l osses as~ociated with grazing animals 1. 8 II. 1.2.5 Conclusions 19 II. 1. 3 SULPHUR ADDITIONS TO THE CYCLE 19 II. 1. 3 . 1 Atmcsphe.ric S ?..d I I .1. 3.3 Sulphur additions from weathering of miner al s 21 I I.1.3 , q Fertiliser sulphur addi t i ons 21 II.1.3.5 Conclus i ons 22 II.1.4 GENERAL CONCLUS I ONS 22 IL 2 POTASS I UM REVIEW 23 II. 2. 1 THE POTASSIUM CYCLE I N GRAZED PASTURES 23 II. 2. 1.1 Soil po t assium 23 II. 2.1.1 . 1 The readi l y plant avail - abl e soil potassium 23 II. 2. 1. 2 The pl ant potassium pool 24 II. 2. 1. 3 The animal potassium pool 25 II. 2, 2 POTASSIUM LOSSES FROM THE K CYCLE 25 II. 2. 2.1 Po t assium drainage water l osses 25 II. 2. 2 .1 . 1 Potassi um leaching losses i n l aboratory a nd gl asshouse studies 26 II. 2 . 2.1 . 2 Potassium leaching losses in lysimeter s tudies 28 I I . 2. 2. 1.3 Potassium drainage water l osses in field studies 28 II . 2. 2.1.4 Conclusions 30 I I . 2. 2. 2 Futassium l osses associated with gr azing animals 30 I I . 2. 2. 3 Conclusions 31 11. 2 . 3 POT/\.SSIUM ADDITIONS TO THEY.. CYCLE 31 II. 2. 3.1 Non-·exchangeable K addition 31 II.2.3 . 2 Potassium r ainfall additj or.s 33 II.2. 3. 3 Fertiliser potassium additions 33 II. 2 . 3. 4 Conclusions 33 II.2.4 GENERAL CONCLUSIONS 33 CHAPTER III METl-IODS fJW MATERIALS I II. 1 SOIL PROPERTIES 34 I II. 2 FIELD TECH...~IQUES USED FOR I~'VESTIGA'fING S0 4-S AND K SURFAC E RUNOFF LOSSES 35 III. 2.1 FIELD METHODS (1976) 35 III. 2. 2 FIELD METHODS (1977) 36 III. 3 FIELD TECJINlQUES USED FOR INVESTIGATING S04-S AND K LEACHING LOSSES 38 III . 4 SOIL SAMPLING 43 CHAPTZR III (continued) Page I II.5 RAINFALL M~ASUREMENT AND SAfWLING FOR S AND K LEVELS 43 III. 6 LABORATORY PROCEDURES 43 CHAPTER IV RESULTS AND DISCUSSION 46 IV.1 SULPHUR 46 IV.1.1. SULPHUR SURFACE RUNOFF LOSSES 46 IV.1.1.1 Surface runoff (1976) 46 IV.1.1.2 Surface r unoff (1977) 47 IV.1.1.3 A comparison between runoff losses in 1976 and 1977 51 IV.1.2 SULPHUR LEACHING LOSSES 53 I V.1. 2.1 Dissolved S04-S tile drainage wa t er -losses 53 IV.1.2.2 Prediction of S04-S tile drainage water losses 61 I V.1. 2.3 Fertiliser S recovery in the soil 64 IV. 1. 3 RAINFJ\LL S1...1LPJlUR ADDITION 67 IV.1.4 GENERAL DISCUSSION 67 IV. 2 POTASSlUN 71 IV . 2. 1 POTl\.SS IIDl St;RF/,CE RUNOFF LOSSES 71 lV . 2. 1 .1 Surface runoff (1976) 71 IV. 2.1. 2 Surface runoff (1977) 72 IV.2.1 . 3 A comparison between runo[f los s es in 1976 and 197 7 76 IV. 2. 2 POTASSIIB.f LEACHING LOSSES 78 IV. 2.2.1 Dissolved K tile drainage water losses 78 IV . 2.2 .2 Prediction of K tile drainage v?ater l osses 80 IV.2.2.3 Fertiliser K r ecovery in the soil 86 IV . 2.3 RAINFALL K ADDITIONS 86 IV. 2.4 GENERAL DISCUSSION 87 CHAPTER V CONCLUSIONS 90 CHAPTER VI SUt-fM.J\R y 92 APPEND I CES 96 BIBL IOGPJ\l>J-;'l 100 LIST OF PLATES Plates Page I View of the subsurface drainage plots 39 II Apparatus used manually to sample and obtain 'representative' samples of, the percolate 39 LIST OF FIGURES Figure Page 1 Mean dissolved S0 4 -S concentrations in surface runoff from undrained and drained plots in each flow event (1976) 48 2 Mean dissolved S0 4 -S concentrations in surface · runoff from unf ertilised and fertilised plots in each flow event (1977) 50 3 Cumulative S0 4 -S surface runoff l osses from unfertilised and fertilised plots in 1977 52 4 Mean dissolved S04 -S concentr ations in leachate discharged from paired unfertilised and fertilised plots in each tile drainage event in 1977 a ) Plots 3 and 1 57 b) Plots 2 and 4 58 c) Plots 7 and 8 59 d) Plots 6 and 8 60 5 Relationship between water soluble soil so~-s (0-40 cm) levels and S0 4 -S concentrations in the leachate 63 6 The average quantity of water soluble soil S04-S (0-60 cm) present in plots 2, 3, 6 and 7 in excess of that present in plots l, 4 , 5 and 8 at each sampling prior to and after fertilisatjon, ~nd rainfall received between sampling intervals 65 7 Mean dissolved K concentrations in surface runoff from undrained and drained plots in each flow event (1976) 73 8 Mean dissolved K concentrations in surface runoff from unfertilised and fertilised plots in each flow event (1977) 75 9 Cumula tive K surface runoff losses from unfertilised and fertili sed plots in 1977 77 10 Mean dissolved K concentrations in leachate discharged from paired unfertilised and fertilised plots in each tile dra inage event in 1977 a) Plots 1 and 2 81 b) Plots 3 and 4 82 c) Plots 5 and 6 83 d) Plots 7 and 8 84 LIST OF TABLES Table Page I Sulph~r leaching losses in laboratory and glasshouse studies 9 II Sulphur leaching losses in lysimet e r studies 12 III Mean values for 3- 4 years of S0 4-S in precipi tation (excluding dust) for a transect of the South Island (hlalker and Gregg (1976) based on Ilorn' s unpublished data) 20 IV Potassium leaching losses in l aboratory and glasshouse studies 27 V Site descriptions of the surface r unoff plot s used in 19 76 (plots 1-4 inclusive) and 1977 (plots 5-8 inclusive) and fertiliser Sand K treatments 37 VI Soluble sulphar~-sulphur and potassium tile draiP.:ige water losses on May 25-26 and June 17, dEtcrmined from frequently , manually obtained samples of the diEcharge water and from a r epresentative sanple !;2 VII Wat er soluble and P0 4-extractablc soil S04 - S l evels in the Tokomaru s ilt loam prior to f c ..·tj lisation 45 VIII Dissolved sulphate- sulphur surface runoff losses in 1977 , the quantity of water discharged from both undrained and drained plots and mean S04-S concentrations in the runoff 46 IX Dissolved S04-S surface runoff losses in 1977, the quantity of water discharged from the adjacent paired plots and mean S0 4-S concentrations in the runoff 49 X The fertiliser (1976) and fertiliser and excretal S (1977) loss pattern in the initial 840 m3 ha- 1 of runoff waters discharged in 1976 and 1977 53 XI Dissolved S04-S lost in tile discharge water from each of the eight plots during 1977, the quantity of water discharged from each plot and mean S04··S concPntrations in the leachate 55 XII Actual and adjus ted mean S0 4-S tile drainage water losses from unfertilised and f ertilised plots during the interval J uly 1 to Sept ember 21 , 1977 54 XIII Mean dissolved S0 4-S tile drainage water leaching losses from non-irrigated and irrigated plots in 1977, and mean water yields 56 Table Page XIV Relationship between mean dissolved S04-S concentration in tile drainage wat er and water soluble soil S0 4 -S levels at different depths expressed as correlation coefficients 62 xv The average quantity of water soluble S0 4 -S present in plots 2, 3, 6 , 7 (0-60 cm) in excess of that present in plots 1, 4, 5, 8 (0-60 cm) pr~or to and after fertilisation 64 XVI Measured fertiliser S leaching l oss from the upper 20 cm of soil in 1977 66 XVII Mean water soluble S0 4 -S contents of the upper 20 cm of soil in the replicate plots in autumn before the tile drainage season commenced, and spring after the tile drainage season had concluded 67 XVIII Rain received S, concentrations in the rain and total rainfall addition o•,er the interval May i2 to October 30, 1977 68 XIX Dissolved K surface runoff losses in 197 6 and mean K concentrations in the runof f 71 xx Dissolved potassium surface runoff losses i n 1977 , losses prior to and after fertilisation of two of the four plots, and water yields XXI The fertiliser (1Q76) and fertiliser excretal K (1977) loss patlern jn the initial 840 m3 ha- 1 of runoff watei discharged in 197 6 and 1977 78 XXII Dissolved K lost in tile discharge waters f rom each of the eight plots during 1977 and mean}~ concentrations in the leachate 79 XXIII Actual and ' adjusted' mean K tile drainage water losses from unfertilised and fertilised plots during the interval July 1 to September 21, 1977 79 XXIV Mean dissolved K tile drainage water leaching losses from non-irrigated and irrigated plots in· 1977 , mean water yields, a nd mean K concentrations in the leachate 80 XXV Rain rece ived, K concentra tions in the r a:i n and the total K received during the interval May 12 to October 30, 1977 87 CHAPTER I INTRODUCTION · In grazed pastures, nutrient ions move continuously £:com the soil to the plant and back into the soil, either directly in plaut residues or indirectly via the grazing animal . Nutrient ions exist i n a varie ty of soil, plant and animal pools within this cycle. Addit ions to and l osses from t he cycle occur.by a variety of processes. Within this cycle, the size of a particular plant available soil nutrient pool a t any one time (assumfng the other nutrient l evel s are adequate) , controls and may limit plant growt h and hence ani mal produc tion. Fact.ors which influence the size of the plant available pool, aside from the xate of p!ant nutrient uptake, include: (i) the r ate at which the r.utrient ion is recycled into the plant available soil pool , and (ii) the balance betw~en non- cy~lic additions to and l osses from the plant available soil nutrient pool. If the r elative i mportance of thosP. factors affecting the pool s i ze can be defined, the principal factors r esponsible for inducing pasture nutt""ien t deficiencies can be determined and reasoned improve ments rnade in management practices. The most widespr ead nutrient deficiency in New Zeal a nd pastures is .phosphate-phosphorus. The P-cycle in grazed pas tures, and the i mportance of various loss mechanisms in inducing P deficiencies have, however , been studied in some detail . Pasture production is al so frequently limited by sulphur and potassium deficiencies. Sulphur dcficienciE:s eenerally follow a cessation in S fertiliser applications, but deficiencies do also occur in areas receiving regular S applications at rates sufficient to meet pasture requir.e ments. In some instances, the S cycl e turnover rate may limit productivity. Net S immob iH.sation may also account for the 2 occurrence of S defic i encies. Frequently , however, pasture S deficiencies in New Zealand have been attributed to significant plant available soil S0~-S losses in surface and, in part icular subsurface drainage waters. At the time this s tudy was cow.menced, S drainage water losses in New Zealand had not been measur ed in the field. In New Zealand pasture potassium deficiencies arc endemic on certain soils , In other a r eas, K deficieucies have arisen following the correction of other nutrient deficiencies and subsequent increases in the general level of producLivity, · Ti.e K cycl e turnover rate is unlikely to limit productivity as K, exi sting only in ionic. combina tion, may move rapidly through the cycl e . Potassi um losses from the cycling pool mus t exceed additions to the cycle. Potassium l osses associated with grazing animals ma~ be important , Controversy exists , r egarding the importance of K dr ainage water l osses i n promoting K de ficiencies . Drainage water K losses have not been i nvestigated in the f ield in New Zealand, The principal aim of this study was to measure plant available sulphate- sulphur and potassium surface and subsurface dr~inage wa ter losses, from a New Zealand soil in the field.