soil chemistry and leaching losses of nutrients from semi-natural grassland and arable soils on...

15
Biological Conservation 57 (199 l) 257-271 Soil Chemistry and Leaching Losses of Nutrients from Semi-natural Grassland and Arable Soils on Three Contrasting Parent Materials R. H. Marrs, M. W. Gough & M. Griffiths Ecological Processes Section, NERC, Institute of Terrestrial Ecology, Monks Wood Experimental Station, Abbots Ripton, Huntingdon PEI7 2LS, UK (Received 22 September 1990; revised version received 5 December 1990; accepted 20 December 1990) A BS TRA C T Soil chemistry and rates of nutrient loss through leaching were studied in soils taken from fields under both arable cultivation and semi-natural grassland on three contrasting parent materials--clay, sand and chalk. Soil chemical properties were assessed at three depths. Levels of available phosphorus and potassium in arable soils were much higher than those in semi-natural grassland, and would prevent the establishment and subsequent maintenance of semi-natural vegetation. In contrast, rates of mineralizable nitrogen were much greater on grassland soils. In general, element concentrations declined with depth, but there were exceptions. Leaching rates were studied using intact lysimeter cores, and the arable soils were either leJ? fallow or sown with Lolium perenne. Nitrogen loss was increased by fallowing compared to soils under grass (sown arable and semi- natural grassland) where losses of nitrogen were <5% of the total Phosphorus leaching was low in all treatments (<1% of total) with the greatest loss on fallowed arable sand)' soils (1.3gPm-2). Leaching is, therefore, a relatively minor pathway for nutrient loss on fertile soils, and future studies on the mechanisms of nutrient depletion should concentrate on soil-plant nutrient cycling processes. INTRODUCTION In general, semi-natural grasslands and heathlands with a high conservation interest tend to be found on infertile soils (Harper, 1971; Rorison, 1971; 257 Biol. Conserv. 0006-3207/91/$03"50 © 1991 Elsevier Science Publishers Ltd, England. Printed in Great Britain

Upload: rh-marrs

Post on 21-Oct-2016

212 views

Category:

Documents


0 download

TRANSCRIPT

Page 1: Soil chemistry and leaching losses of nutrients from semi-natural grassland and arable soils on three contrasting parent materials

Biological Conservation 57 (199 l) 257-271

Soil Chemistry and Leaching Losses of Nutrients from Semi-natural Grassland and Arable Soils on Three

Contrasting Parent Materials

R. H. Marrs, M. W. G o u g h & M. Griffiths

Ecological Processes Section, NERC, Institute of Terrestrial Ecology, Monks Wood Experimental Station, Abbots Ripton, Huntingdon PEI7 2LS, UK

(Received 22 September 1990; revised version received 5 December 1990; accepted 20 December 1990)

A BS TRA C T

Soil chemistry and rates of nutrient loss through leaching were studied in soils taken from fields under both arable cultivation and semi-natural grassland on three contrasting parent materials--clay, sand and chalk. Soil chemical properties were assessed at three depths. Levels of available phosphorus and potassium in arable soils were much higher than those in semi-natural grassland, and would prevent the establishment and subsequent maintenance of semi-natural vegetation. In contrast, rates o f mineralizable nitrogen were much greater on grassland soils. In general, element concentrations declined with depth, but there were exceptions.

Leaching rates were studied using intact lysimeter cores, and the arable soils were either leJ? fallow or sown with Lolium perenne. Nitrogen loss was increased by fallowing compared to soils under grass (sown arable and semi- natural grassland) where losses of nitrogen were <5% of the total Phosphorus leaching was low in all treatments ( < 1 % of total) with the greatest loss on fallowed arable sand)' soils ( 1 . 3 g P m - 2 ) . Leaching is, therefore, a relatively minor pathway for nutrient loss on fertile soils, and future studies on the mechanisms of nutrient depletion should concentrate on soil-plant nutrient cycling processes.

INTRODUCTION

In general, semi-natural grasslands and heathlands with a high conservation interest tend to be found on infertile soils (Harper, 1971; Rorison, 1971;

257 Biol. Conserv. 0006-3207/91/$03"50 © 1991 Elsevier Science Publishers Ltd, England. Printed in Great Britain

Page 2: Soil chemistry and leaching losses of nutrients from semi-natural grassland and arable soils on three contrasting parent materials

258 R. H. Marrs, M. W. Gough, M. Griffiths

Green, 1972, 1980; Grime, 1979, 1987; Bakker, 1989), and good conservation management involves, at the very least, preventing any increase in the nutrient supply. Moreover, where nutrients are added to semi-natural grassland, there is usually a reduction in species diversity (Williams, 1978; Marrs & Gough, 1989; Marts, 1990; Mountford, 1990). In the last five years there have been increasing attempts to try and recreate floristically rich communities on abandoned agricultural land either under 'Set-aside' schemes (MAFF, 1988), or more positively under the 'Countryside Premium' scheme (Countryside Commission, 1989). Both schemes have arisen to help reduce agricultural surpluses by taking land out of productive use. There is, therefore, a possible conflict between the apparent difficulties in maintaining communities under conditions of high fertility and the desire to establish these communities on soils which may have high residual fertility.

Several studies have shown that it is the high availability of phosphorus found in arable soils which is likely to cause problems for the maintenance of semi-natural grassland communities. Often extractable phosphorus values are at least three to four times those of semi-natural grasslands on similar parent materials (Gough & Marrs, 1990a), al though exchangeable potassium may also be involved to a lesser degree. The amount of residual extractable phosphorus declines during succession, but rates of decline vary widely. It can take from between four and twelve years (Odum et al., 1984; Pakeman, 1986; Gough & Marrs, 1990b) to > 70 years (Johnston & Poulton, 1977) for the initial residual phosphorus to decline to levels typical of semi- natural grassland, depending on the amount remaining in the soil and the management applied. We have, however, very little information on the mechanisms controlling the loss of nutrients, although Odum et al. (1984) ascribed measured losses to leaching.

In an attempt to investigate whether leaching was a major loss pathway we have (1) measured soil chemical properties in soils from arable land and under semi-natural grassland on three types of contrasting parent material, and (2) measured leaching losses from these soils using an experimental lysimeter approach. In the lysimeter study, arable soils were either sown to grass or kept as bare fallow so that the effect of developing vegetation could be compared. Bare fallow has been suggested as one way of accelerating nutrient losses (Marrs & Gough, 1989; Marrs, 1990).

METHODS

Sites and field sampling

In May 1989, two sampling areas were chosen on each of three types of parent material--clay, chalk and sand. At each sampling area two sites were

Page 3: Soil chemistry and leaching losses of nutrients from semi-natural grassland and arable soils on three contrasting parent materials

Nutrient loss in grassland/arable soils 259

selected as follows (see Table 1 for details): (1) a site with a semi-natural grassland vegetation of high conservation interest, and (2) a field under intensive arable cultivation, which had recently been sown and given heavy dressings of fertilizer. At each site randomly chosen points were sampled (three in the semi-natural grassland and six in the arable field), and at each point soil samples were collected for chemical analysis and a lysimeter core was taken for experimental study.

Soil sampling

At each sampling point three replicate soil samples (6 cm diameter x 20 cm deep) were collected from three depths (0-20 cm, 20~,0 cm, 40-60 cm). The replicate samples from each depth were pooled, air-dried, sieved to pass a 2-mm mesh, thoroughly mixed and weighed. Soil pH, loss-on-ignition,

T A B L E 1 Brief Details of the Sites used in this Investigation

Parent Vegetation Grid Soil O'pe Vegetation/crop material histo 0' r¢[~,rence

Clay Grass TL 446328 Calcareous gley in the Semi-natural meadow-- Hanslope association 26 species described (Thomasson, 1969) (Gough & Marrs, 1990b)

Arable TL 439334 Calcareous gley in the Intensive arable Hanslope association oats sown March 1989 (Thomasson, 1969)

Chalk Grass TL 349402 Calcareous silty Semi-natural chalk soils in the Upton 1 grassland (see Grubb association (Avery, & Key, 1975) 1980)

Arable TL 585650 Calcareous silty Intensive arable- - soils in the mustard sown May 1989 Wantage 2 association (Avery, 1980)

Sand Grass SK 644743 Well-drained sandy Heath vegetat ion-- soils in the Cuckney 1 mainly Deschampsia association (Avery, flexuosa (see Gough 1980) & Marrs, 1990a)

Arable SK 646749 Well-drained sandy Intensive arable--rape soils in the Cuckney 1 association (Avery, 1980)

Page 4: Soil chemistry and leaching losses of nutrients from semi-natural grassland and arable soils on three contrasting parent materials

260 R. H. Marrs, M. W. Gough, M. Griffiths

extractable nitrogen and phosphorus (sodium bicarbonate extractant), mineralizable nitrogen (14-day incubation at 30°C) and exchangeable potassium, calcium and magnesium were measured using the methods outlined by Allen et al. (1974). Results for the chemical analyses were expressed on an oven-dry weight basis both as a concentration (~g g- x) and as amounts on an area basis (g m - 2). As the conclusions from both datasets were similar the concentration data are detailed here to enable comparisons with other studies.

M o v e b le c r o s s m e m b e r l o w e r e d ff w h e n m e x l m u n ~ z ~

T w o s e t s o f / / ~/;hWr a n c h o r s / /

~L~. ~'~Hydreullc Jack used \\--to push c o r e

r o u n d

P l a s t i c l y s i m e t e r c o r e \ \ f i t t e d w i t h c u t t i n g r i n g a n d l id

(a)

Silicone rubber s e a l w i t h s u p p o r t i n g \

b r a c k e t s

B o a r d s u p p o r t e d on c o n c r e t e b l ~ k s f i t t e d w i t h f i l t e l t u n n e l s

P l a s t i c l y s i m e t e r c o r e

Gravel

~ _ ~ Filled w i t h w a s h e d g r a v e l on s t a i n l e s s s t e e l m e s h

- - H o s e t o c o l l e c t i o n b o t t l e

Fig. 1.

(bl

Diagrammatic representation of (a) the equipment used to collect the lysimeter cores, and (b) the lysimeter trench and leachate collection system.

Page 5: Soil chemistry and leaching losses of nutrients from semi-natural grassland and arable soils on three contrasting parent materials

Nutrient loss in grassland/arable soils 261

Lysimeter collection and experiment

Plastic tubes (0.24 m diameter × 0.5 m deep), fitted with a steel cutting collar and a metal lid, were pushed into the ground at each sampling point using a portable jacking apparatus (Fig. l(a)). At the grassland sites the vegetation- soil was collected intact, but in the arable fields the crop plants were removed. The tubes were then dug out, stored at 4°C until they were fitted into a lysimeter trench at Monks Wood Experimental Station (Fig. l(b)), where irrigation could be controlled and leachates collected. Half of the lysimeters from the arable fields were randomly chosen to remain 'fallow' with all establishing plants being removed at weekly intervals, whilst the remainder were sown with L o l i u m p e r e n n e (varieties=40% Arno; 30% Manhattan; 30% Ranger) at a seed rate of 44 g m-z. The 27 lysimeters were then allocated to positions in the lysimeter trench in a completely randomized experimental design, with

3 parent materials (chalk, clay, grass) x 3 treatments (grass, arable + grass, arable + fallow) x 3 replicates.

The experiment started on 26 June 1989 (designated day 0). Initially water was supplied only by rainfall. However, the 1989 summer had a particularly low rainfall and supplementary rainfall was supplied at a rate of 0"5 litre week - 1. This amount is equivalent to the ten-year weekly average rainfall at Monks Wood of 44ram week-1. On 27 November the entire lysimeter trench was enclosed by a polythene garden tunnel, and irrigation was increased to 1-0 litre week-x. Leachates were collected at weekly intervals from 3 July 1989 until 25 May 1990. There was no evidence of any flush of nutrients in the early part of the experiment brought about by collecting the cores. Leachates were analysed for the two most important elements influencing soil fertility, phosphorus and nitrogen, using chemical procedures outlined in Allen et al. (1974).

RESULTS

Element concentrations in surface soils (Table 2)

The pH of all arable soils was greater than pH 6-8, and the pH of the chalk and clay grassland soils were in a similar range. The grassland on the sand had a lower pH (pH = 4"3). Loss-on-ignition was lowest on the sand (<4%), intermediate on the clays (5-7%), and showed the greatest difference between the grassland and arable soils on the chalk (grass= 18%vs arable = 5%).

Page 6: Soil chemistry and leaching losses of nutrients from semi-natural grassland and arable soils on three contrasting parent materials

262 R. H. Marrs, M. W, Gough, M. Griffiths

T A B L E 2 Chemical Propert ies of the Surface Layer (0-20 cm depth) of Soils under Arable Cul t iva t ion

and Semi-natura l Grass l and on Three Cont ras t ing Parent Mater ia ls

Soil parameter Chalk Clay Sand

Grass Arabh" Grass Arable Grass Arable

pH 7.3+0.06 7-5+0-05 7"3_+0"09 7.6+0"07 4-3+_0.11 6.9_+0-05 LOI (%) 17.7+0.6 4.7_+0-1l 7"8+_0-2 5.2+0"1 3.5±0.5 2.7_+0.02 Extractable 33_+9 36_+3 23_+4 27_+7 14__+2 18-+2

N (#gg- 1) Mineralizable 139+53 - 9 + 9 68_+ 11 - - 4 + 3 23__+3 --9+-2

N(#gg l l4days 1) Extractable 16.3+-0.7 42.6_+ 1.5 8-2+- 1-9 62.0+-24.3 22.0__+2.5 88.5-+4.2

P (l~g g-1) Exchangeable 87+_37 191 ! 15 407+- 14 996+-236 20-+ 1 81 + 6

K (#gg- 1) Exchangeable 14.5+-0-7 10-3 +- 0-5 12-9+_0-3 10-5+-0,4 0-3_+0-01 2-6+-0-2

Ca (mgg-1) Exchangeable 182+-7 88_+3 136+-2 141_+12 20+-0.4 81+-6

M g (~g g- 1)

Mean values (ngra+ ~ = 3; n,ra~ = 6) _+ standard errors are presented,

Extractable nitrogen showed no differences between arable and grassland soils on any soil type, although chalk had highest levels, clay was intermediate and sand was lowest. This general rank order with respect to substrates was also found for mineralizable nitrogen on grassland but not on arable soils where mineralization rates were negative, indicating a net immobilization of inorganic nitrogen by microbial activity.

Extractable phosphorus was lower in all grassland soils than correspond- ing arable soils. On the chalk and clay the concentration in grassland soils was between 10 and 20/~g P g-1, the range suggested as suitable for the maintenance of semi-natural grasslands (Gough & Marrs, 1990a), but the concentration of the acid sandy grassland was marginally greater than this target range at 23 ~g P g- t . The arable soils on both chalk and sand had extractable phosphorus concentrations between three and four times the grassland soils, whereas on chalk the concentration was almost eight times grassland values.

Exchangeable potassium showed similar results to those of phosphorus with greater concentrations being found on the arable soils. Clay soils had highest concentrations of potassium, chalk soils were intermediate and sands had the lowest. Clay and chalk arable soils had approximately twice the amounts of potassium as grassland but on sands the difference was four times.

Page 7: Soil chemistry and leaching losses of nutrients from semi-natural grassland and arable soils on three contrasting parent materials

Nutrient loss in grassland/arable soils 263

Depth distribution of nutrients

The amount of nitrogen mineralized was greater in the grassland soils, with most of the activity concentrated in the surface layer. Rates were either negligible below 0-20 cm depth, or at least one-third of surface values (Fig. 2). Arable soils had negative rates throughout the entire profile (Fig. 2). The distribution of extractable phosphorus and exchangeable potassium in the

ARABLE GRASS

Chalk

0 - 2 0

2 0 - 4 0

4 0 - 6 0

/

Soil depth(cm)

0 - 2 0

2 0 - 4 0

4 0 - 6 0

Clay

0 - 2 0

2 0 - 4 0

4 0 - 6 0

- 2 5 0

Sand

50 100 150 - 2 5 50 100 150

Minera l ized N (pg g-i 14d-J)

Fig. 2. Depth distribution of mineralizable nitrogen on soils under arable cultivation and semi-natural grassland on three contrasting parent materials; mean values (ng .. . . = 3 ;

n.r.b~e = 6) + standard errors are presented.

Page 8: Soil chemistry and leaching losses of nutrients from semi-natural grassland and arable soils on three contrasting parent materials

264 R. H. Marts, M. W. Gough, M. Griffiths

0 - 2 0

2 0 - 4 0

4 0 - 6 0

ARABLE

Chalk

,+,

GRASS

Soil dept h(cm)

0 - 2 0

2 0 - 4 0

4 0 - 6 0

Clay

0 - 2 0

2 0 - 4 0

4 0 - 6 0

Sand

t ,t

40 80 0 40 80

Extractable P (lug g ' )

Fig. 3. Dep th dis t r ibut ion of extractable phosphorus on soils under arable cul t ivat ion and semi-natural grassland on three cont ras t ing parent materials; mean values (ng .... = 3;

na,abl~ = 6) + s tandard errors are presented.

arable soils showed marked differences between elements and parent materials. There was a significant reduction in the amount of extractable phosphorus with depth on the clay; this was less apparent on the sand, and absent on the chalk (Fig. 3). Indeed, the greatest amount of extractable phosphorus was found in the deepest layer of the chalk (Fig. 3). Extractable potassium was relatively low on the arable soils of chalk and sand, but on the clay soils there were (1) greater amounts throughout the profile, and (2) a pronounced decline in amounts of potassium with depth (Fig. 4).

Page 9: Soil chemistry and leaching losses of nutrients from semi-natural grassland and arable soils on three contrasting parent materials

Nutrient loss in grassland/arable soils 265

m

0-20

20-40

40-60 "

ARABLE

Chalk

GRASS

Soil depth(cm)

0-20

20-40

40-60

Clay

Sand

0 -20~

20-40~

40-60~_ 0 500 1000

Exchangeab le K (~g ~l)

500 1000

Fig. 4. Depth distribution of exchangeable potassium on soils under arable cultivation and semi-natural grassland on three contrasting parent materials; mean values (ng .... = 3 ;

rlarable = 6) + standard errors are presented.

Lysimeter experiments--loss of nitrogen and phosphorus (Table 3)

The loss of nitrogen and phosphorus was measured over eleven months covering the winter period when leaching losses should be at a maximum because of low plant uptake. This appeared to be the case because losses of both phosphorus and nitrogen reached an asymptote in February and March at approximately 250 days (Fig. 5).

The data for nitrogen and phosphorus loss gave contrasting results. Nitrogen showed significant differences (p < 0"05) between treatments and

Page 10: Soil chemistry and leaching losses of nutrients from semi-natural grassland and arable soils on three contrasting parent materials

266 R. H. Marrs, M. W. Gough, M. Griffiths

T A B L E 3 Loss of Nitrogen and Phosphorus from Lysimeters Collected from Three Contrast ing Parent Materials under both Arable Cultivation and Semi-

natural Grassland

(a)

Parent Treatment material history

Amount otelement leached

g in - 2 % Ol" total amount in lysimeter

N P N P

Chalk Arable fallow Arable grass Grass

Clay Arable fallow Arable grass Grass

Sand Arable fallow Arable grass Grass

LSD (p < 0"05)

51 0"2 16 0"1 7 0.2 2 0"l 9 0'3 2 06

15 0"l 5 0-1 11 0"4 4 0"6 8 0'5 2 0-1

38 1"3 33 0"9 3 0-1 3 0.1 7 0-2 0.1 0"6

19 0-9 . . . .

(b)

Parent Treatment Total amount o[ N material and P in lysimeters

(gm 21

N P

Chalk Arable 323_+10 181_+10 Grass 532± 108 53_+ 10

Clay Arable 303 ± 21 70 _ 2 Grass 444_+5 51 _+ 13

Sand Arable 114_+3 142_+18 Grass 836_+56 31_+1

In (a) losses are expressed as g m 2 and as a % of total element content of the lysimeter core, and in (b) total amount of element in lysimeter (g m 2).

Page 11: Soil chemistry and leaching losses of nutrients from semi-natural grassland and arable soils on three contrasting parent materials

Nutrient loss in grassland/arable soils 2 6 7

Fig. 5.

90-

80

70

60

50

40

30

20

10

Amount leached (g m -2)

J

0 40 8'0 120 160 200 240 280 320 360

Days

(a)

:t 0 4 0 8 0 120 160 2 0 0 2 4 0 2 8 0 3 2 0 3 6 0

Days

(b) Leaching loss of(a) nitrogen and (b) phosphorus throughout the experiment for one

represcntative treatment (sand with arable + fallow).

an interaction with parent materials. Nitrogen loss was greater by almost an order of magnitude on the fallowed arable soils compared to either the grassland soils or the arable + grass on the chalk and sand, but not on the clay. In absolute amounts, nitrogen loss was < = l l g N m -2 on the grassland and arable + grass soils. If fallowing was used then losses varied from 15 to 51 g N m-2 depending on parent material.

Phosphorus, on the other hand, showed no significant difference between parent materials or treatments and losses were low ( < = 0-5 g P m 2) in all treatments except the arable + fallow on sand, where losses were 1"3 g m - 2

Expressed as a percentage of the total amounts of nutrients in the lysimeters, nitrogen losses were < 5% for all treatments where grass was present and the clay fallow, but 16% on fallowed chalk and 33% on fallowed sand. Phosphorus loss was < 1% for all treatments.

Page 12: Soil chemistry and leaching losses of nutrients from semi-natural grassland and arable soils on three contrasting parent materials

268 R. H. Marrs, M. W. Gough, M. Griffiths

DISCUSSION

The soil chemical data confirmed that the soils under semi-natural grasslands had much greater supplies of nitrogen from mineralization, lower exchangeable potassium and much lower extractable phosphorus levels than adjacent arable soils. There were few differences in levels of mineralizable nitrogen and extractable phosphorus between the three contrasting parent materials but exchangeable potassium increased in the order sand < chalk < clay. The main problem element for the creation of semi-natural grassland communities on arable soils, at least in the short term, is phosphorus, with potassium perhaps contributing a minor effect. The phosphorus supply in all grassland soils was low, and was at or below the target level suggested by Gough and Marrs (1990a) for successful establishment and maintenance of semi-natural grassland. The nitrogen supply will have a minimal effect in the early stages, but may increase later if legumes invade and are encouraged by the elevated phosphorus supplies (Bradshaw et al., 1978). These conclusions confirm our earlier findings where successional sequences were compared on the same three parent materials (Gough & Marts, 1990a).

In general, there was a marked decline in nutrient concentration with depth, with the only exception being on chalk arable soils, where high concentrations were found in all three depths sampled. The results for these deep arable soils on chalk were surprising in view of the high adsorption capacity of calcareous soils (Rizand et al., 1989). These high values were, however, not brought about by analytical errors, because identical results were obtained in duplicate analyses by different analysts. There are two important conclusions to be drawn from this depth study. First, at the sand and clay sites surface availability of phosphorus may be reduced rapidly if some of the topsoil is stripped or the surface layer is incorporated in lower horizons (Marrs, 1985, 1990; Marrs & Gough, 1989). Second, the results for the chalk sites highlight the difficulties of defining general rules about soil chemistry. Topsoil removal or deep ploughing would have had no instantaneous effect on extractable soil phosphorus level at this site. It is, of course, likely that the high levels of extractable phosphorus found at depth on chalk reflect recent fertilization, and that these levels would in time decline naturally by adsorption and chelation. Clearly, more information is needed on (1) the chemical properties of soils under semi-natural ecosystems, (2) the variability between different soil types, and (3) the effects of conservation management treatments on soil chemistry before general conservation management prescriptions can be drawn up.

The leaching losses in the lysimeter experiments showed that once

Page 13: Soil chemistry and leaching losses of nutrients from semi-natural grassland and arable soils on three contrasting parent materials

Nutrient loss in grassland/arable soils 269

grassland had established on the arable soils, the losses of both nitrogen and phosphorus were similar to those on the semi-natural grasslands. These systems became very 'nutrient-tight'. This would be expected as they are essentially 'aggrading systems' (sensu Bormann & Likens, 1978) with an accumulation not only in the developing plants and roots of the grassland vegetation, but also in soil organic matter (Jenkinson, 1988). However, where vegetation development was prevented in the fallow treatments, losses of nitrogen were greatly enhanced, and phosphorus remained more or less the same. Nitrogen loss under continuous fallow is well-known (Marrs & Gough, 1989), with perhaps the best-known example found in the long-term experiments at Rothamsted (Jenkinson, 1988). Here, there was a reduction in soil organic matter in 20 years from a starting capital of 3 to 1"5% under continuous bare fallow, to 1.9% under a three-course arable rotation, and to 2% under a six-course rotat ion--5 arable + one ley.

Thus, leaching appears not to be a major pathway for nutrient loss after abandoning fertile arable soils. Odum et al. (1984), in a study of old field successions in the USA, showed that extractable phosphorus declined over an 11-year period, and they implied this loss was through leaching. However, these authors admitted that they used the term 'leaching' to include all other loss pathways about which they had no information. As a reduction in soil extractable phosphorus appears to be a feature of many successions on abandoned arable soils (Odum et al., 1984; Pakeman, 1986; Gough & Marrs, 1990a,b) and if phosphorus was not lost directly from the system, the reduction in the available pool must be accounted for by a change in turnover within the ecosystem. We might predict that the increase in organic matter would result in parallel increases in the organic forms of most nutrients, microbial biomass and nutrients, and changes in mineralization (Jenkinson & Powlson, 1976; Brookes et al., 1982, 1985). Moreover, for phosphorus the rates at which adsorption and chelation occur will have important consequences for the amounts in plant-available forms (Brad- shaw, 1983; Chapman et al., 1989; Rizand et al., 1989). Further studies of nutrient turnover and storage in a range of successional sequences on different parent materials are clearly required.

A C K N O W L E D G E M ENTS

We are grateful to Lyn Merrick, W. Dimsdale, P. Gough, J. Clarke and the National Trust for permission to sample soils and take lysimeter cores from their land. This work was funded by the Natural Environment Research Council's Special Topic Programme: Agriculture and the Environment.

Page 14: Soil chemistry and leaching losses of nutrients from semi-natural grassland and arable soils on three contrasting parent materials

270 R. H. Marrs, M. W. Gough, M. Griffiths

R E F E R E N C E S

Allen, S. E., Grimshaw, H. M., Parkinson, J. A. B. & Quarmby, C. (1974). Chemical Analysis of Ecological Materials. Blackwell Scientific Publications, Oxford.

Avery, B. W. (1980). Soil classification for England and Wales (higher categories). Soil Surv. Tech. Monogr., No 17.

Bakker, J. P. (1989). Nature Management by Grazing and Cutting. Kluwer, Dordrecht.

Bradshaw, A. D. (1983). The reconstruction of ecosystems. J. Appl. Ecol., 20, 1-18. Bradshaw, A. D., Humphries, R. N., Johnson, M. S. & Roberts, R. D. (1978). The

restoration of vegetation on derelict land produced by industrial activity. In The Breakdown and Restoration of Ecosystems, ed. M. W. Holdgate & M. J. Woodman. Plenum Press, New York, pp. 249 74.

Bormann, F. H. & Likens, G. E. (1978). Pattern and Process in a Forested Ecosystem. Springer Verlag, Berlin.

Brookes, P. C., Landman, A., Pruden, G. & Jenkinson, D. S. (1985). Chloroform fumigation and release of soil nitrogen: a rapid direct extraction method to measure microbial biomass nitrogen in soil. Soil Biol. & Biochem., 17, 837 42.

Brookes, P. C., Powlson, D. S. & Jenkinson, D. S. (1982). Measurement of microbial phosphorus in soil. Soil Biol. & Biochem., 14, 319-29.

Chapman, S. B., Rose, R. J. & Basanta, M. (11989). Phosphorus adsorption by soils from heathlands in southern England in relation to successional change. J. Appl. Ecol., 26, 673 80.

Countryside Commission (1989). The Countryside Premium .for Set Aside Land. Countryside Commission, Cambridge.

Gough, M. W. & Marts, R. H. (1990a). A comparison of soil fertility between semi- natural and agricultural plant communities: implications for the creation of floristically-rich grassland on abandoned agricultural land. Biol. Conserv., 51, 83-96.

Gough, M. W. & Marrs, R. H. (1990b). Trends in soil chemistry and floristics associated with the establishment of a low-input meadow system on an arable clay soil in Essex, England. Biol. Conserv., 52, 135-46.

Green, B. H. (1972). The relevance of seral eutrophication and plant competition to the management of successional communities. Biol. Conserv., 4, 378 84.

Green, B. H. (1980). Management of extensive amenity areas by mowing. In Ameni O, Grasslands: an Ecological Per.sT~ective, ed. I. H. Rorison & R. Hunt. Wiley, Chichester, pp. 151 61.

Grime, J. P. (1979). Plant Strategies and Vegetation Processes. John Wiley, Chichester.

Grime, J. P. (1987). Dominant and subordinate components of plant communities: implications for succession, stability and diversity. In: Colonization, Succession and Stability, ed. A. J. Gray, M. J. Crawley & P. J. Edwards. Blackwell Scientific Publications, Oxford, pp. 413 28.

Grubb, P. J. & Key, B. A. (1975). Clearance of scrub and re-establishment of chalk grassland on the Devil's Dyke. Nat. Cambs, 18, 18 22.

Harper, J. L. (1971). Grazing, fertilizers and pesticides in the management of grasslands. In The Scient(fic Management o/'Animal and Plant CommunitiesJbr Conservation, ed. E. Duffey & A. S. Watt. Blackwell Scientific Publications, Oxford, pp. 15-32.

Page 15: Soil chemistry and leaching losses of nutrients from semi-natural grassland and arable soils on three contrasting parent materials

Nutrient loss in grassland~arable soils 271

Jenkinson, D. S. (1988). Soil organic matter and its dynamics. In Russell's Soil Conditions and Plant Growth, 1 lth edn, ed. A. Wild. Longmans, Harlow, pp. 564-607.

Jenkinson, D. S. & Powlson, D. S. (1976). Effect of biocidal treatments on soil, V. A method for measuring microbial biomass. Soil Biol. & Biochem., 8, 209-13.

Johnston, A. E. & Poulton, P. R. (1977). Yields of the Exhaustion Land and changes in NPK content of the soils due to cropping and manuring. Rep. Rothamsted Exp. Stn 1976, Part 2, 53-86.

MAFF (1988). Set Aside. MAFF, London. Marrs, R. H. (1985). Techniques for reducing soil fertility for nature conservation

purposes: a review in relation to research at Roper's Heath Suffolk, England. Biol. Conserv., 34, 307-32.

Marrs, R. H. (1990). Soil fertility and conservation: review. NERC contract report to Nature Conservancy Council. Institute of Terrestrial Ecology, Huntingdon.

Marrs, R. H. & Gough, M. W. (1989). Soil fertility--a potential problem for habitat restoration. In Biological Habitat Restoration, ed. G. P. Buckley. Bellhaven Press, London, pp. 2944.

Mountford, O. M. (1990). The effects of nitrogen on species diversity and agricultural production on the Somerset Moors: species change in relation to fertiliser levels. Report to IGAP. Institute of Terrestrial Ecology, Huntingdon.

Odum, E. P., Pinder, J. E. & Christiansen, T. A. (1984). Nutrient losses from sandy soils during old field succession. Amer. Midl. Nat., I l l , 148-54.

Pakeman, R. J. (1986). The effects of grass growth on the fertility ofex-scrub soil. BA (Honours) dissertation. University of Cambridge.

Rizand, A., Marrs, R. H., Gough, M. W. & Wells, T. C. E. (1989). Long-term effects of various conservation management treatments on selected properties of chalk grassland soils. Biol. Conserv., 49, 105-12.

Rorison, I. H. (1971). The use of nutrients in the control of the floristic composition of grassland. In The Scientific Management of Animal and Plant Communities Jbr Conser~'ation,ed. E. Duffey & A. S. Watt. Blackwell Scientific Publications, Oxford, pp. 65 78.

Thomasson, A. J. (1969). Soils of the Saffron Walden district. Soil Surv. Spec. Surly., No 2.

Williams, E. D. (1978). Botanical Composition ~['the Park Grass Plots at Rothamsted. Rothamsted Experimental Station, Harpenden.