Soil & Tillage Research, 12 (1988) 163-175 163 Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

Effect of Seeding Method on Alfalfa and Red Clover Establ i shment and Growth, Soil Phys ica l Condit ion and Nematode Populat ions

H.T. KUNELIUS, M.R. CARTER, J, KIMPINSKI and J.B. SANDERSON

Research Station, Agriculture Canada, P.O. Box I210, Charlottetown, Prince Edward Island, C1M 7M8 (Canada)

(Accepted for publication 22 January 1988)

ABSTRACT

Kunelius, H.T., Carter, M.R., Kimpinski, J. and Sanderson, J.B., 1988. Effect of seeding method on alfalfa and red clover establishment and growth, soil physical condition and nematode pop- ulations. Soil Tillage Res., 12:163 175.

Direct-seeding systems have the potential for fast renovation of grass-legume swards in the cool, humid climate of Atlantic Canada. Renovation of grass-dominant swards by direct-seeding alfalfa (Medicago sativa L. ) or red clover (Trifolium pratense L.) was compared with seeding in a cultivated seed bed (conventional system ) on sandy loam Podzolic soils. Seedling establishment, sward productivity, herbage quality, soil conditions and populations of plant parasitic nematodes were determined. In the seeding year, the total yields and legume densities for direct-seeded and conventionally-established swards were similar, but direct seeding resulted in greater alfalfa and red clover yield components. Dry-matter yields of renovated swards were as much as 54% lower than those of the existing control sward. In post-seeding years, swards renovated by direct-seeding alfhlfa or red clover outyielded conventionally-established swards by an average of 11%. Total nitrogen concentration of herbage in renovated swards was higher than that for the control sward. The in vitro digestibility of dry matter did not vary significantly among the methods of establish- ment in the seeding and first post-seeding years. Soil resistance values, within the 0 35-cm soil depth, indicated that the various methods of establishment had not adversely affected the soil condition. There was a trend with conventional establishment toward higher soil populations of Heterodera trifalii (Goffart) and Pratylenchus spp. than with direct seeding.

INTRODUCTION

In r e g i o n s w i t h u n f a v o r a b l e c o n d i t i o n s for p l a n t s u r v i v a l , p e r i o d i c r e s e e d i n g

o f l o n g - t e r m g r a s s - l e g u m e s w a r d s is n e c e s s a r y to m a i n t a i n t h e s o w n spec ie s .

S u c h r e n o v a t i o n u s u a l l y i n v o l v e s m o l d b o a r d p l o w i n g , s e c o n d a r y c u l t i v a t i o n a n d s e e d i n g i m p r o v e d c u l t i v a r s o f a d a p t e d spec ie s . F a s t , o n e - p a s s m e t h o d s o f

p a s t u r e r e n o v a t i o n , s u c h as d i r e c t s e e d i n g , h a v e b e e n d e v e l o p e d for r e j u v e n -

0167-1987/88/$03.50 © 1988 Elsevier Scienoe Publishers B.V.

164

ating existing swards. Several biological and cultural factors influence the es- tablishment of direct-seeded forage species as outlined by Naylor et al. ( 1983 ).

The establishment of grasses and legumes by direct and conventional seed- ing has been compared previously (Mueller-Warrant and Koch, 1980; Koch et al., 1983) but without consideration of the resultant soil conditions. Further- more, the impact of minimum or no-till systems on plant nematodes has not been studied extensively (Minton, 1986). In the present study, therefore the establishment of alfalfa (Medicago sativa L.) and red clover (Trifolium pra- tense L. ) in cultivated seed beds was compared with direct seeding, while tim- othy (Phleum pratense L.) was established only in a cultivated seed bed. Seedling establishment, sward productivity and herbage quality, soil physical condition and nematode populations were determined.

MATERIALS AND M E T H O D S

Field experiments

Field experiments were conducted on a Charlottetown fine sandy loam (Site 1 ) and a Culloden sandy loam (Site 2) both of which are Orthic Humo Ferric Podzols. Differences in soil physical properties, pH and organic carbon, be- tween sites, are given in Table I. Adequate amounts of P, K and B were broad- cast as specified by soil testing. In Site 1, the sward was dominantly t imothy (> 90% dry weight, hand separated) while in Site 2 the sward consisted of t imothy (67%), quackgrass (Elymus repens (L.) Gould) (18%) and broadleaf weeds (Taraxacum spp., Rumex spp.). At each site, two 3-year experiments

TABLE I

Soil characterist ics in Sites 1 and 2

Soil property Charlot te town fine sandy Culloden sandy loam, loam, Site 1 j Site 2 ~

0 16 16-30 cm 0-16 16-30 cm

Clay < 2 llm, % 12 11 6 4 Silt 2 50/~m 31 31 22 28 Fine sand 50 250 pm 41 41 25 21 Sand 250-1000 llm 16 17 47 47

Bulk density Mg m :~ 1.28 1.35 1.36 1.39 Total soil porosity % 51.5 49.0 48.7 47.5 pH H_,O (1 :1) 6.3 5.9 6.1 6.1 Organic carbon % 1.5 1.4 1.4 0.9

'The two soil depths correspond to the Ap and Bf horizons, respectively.

165

were established, Series I in 1981 and Series II in 1982. The plot size was 2.5 × 5.0 m with four replications. A John Deere 1500 PowrTill renovator was used to seed alfalfa and red clover directly into 3-cm wide cultivated slots, spaced 20 cm apart. The opener assembly of this renovator consists of a power-driven cutting blade, followed by a hoe opener for seed placement and a wheel for firming soil in the slot. The conventional method of establishment in culti- vated seed beds involved rototilling to a depth of 15 cm in early September and again before the spring seeding in early May with an Oyjord small-plot seeder. The row spacing for alfalfa or red clover, sown in alternate rows with t imothy plus ryegrass, was 10 cm. For both methods, the depth of seeding was 0.5 cm. Treatments applied were:

(A) control, existing sward fertilized with 75 kg N h a - 1 as NH4NO:~ in early May and again after Cut 1;

(B) conventional establishment of t imothy cv. 'Bounty' at 8 kg h a - 1 and Westerwolds ryegrass (Lolium multiflorum Lam. ) cv. 'Aubade' at 5 kg ha-1;

(C) direct seeding of alfalfa cv. 'Saranac' at 11 kg ha 1 in swards sprayed with paraquat at 0.56 1 ha-1 in 200 1 ha-1 of water 3 days before seeding to suppress the existing sward;

(D) conventional establishment of alfalfa at 11 kg ha-1, t imothy at 6 kg h a - 1 and Westerwolds ryegrass at 5 kg h a - 1;

(E) direct seeding of red clover cv. 'Prosper I' as for (C); (F) conventional establishment of red clover, t imothy and ryegrass as for

(D). Only the legumes were direct seeded in t rea tments (C) and (E) because the

resident grasses recovered after direct seeding. Timothy and Westerwolds rye- grass were sown with conventionally-established legumes (Treatments (D) and (F)) to replace the grass component in swards.

Alfalfa and red clover seedlings were counted in five randomly-selected 0.5- m sections of row in each plot for the seeding and first post-seeding years. Yields were determined by cutting a 1.25-m strip in the centre of each plot two or three times a season at the early flowering stage of alfalfa. Dry matter con- tent was determined from 500-g subsamples. The botanical composition was determined by hand separating 250-g subsamples into sown legume, grasses and other species and drying at 80 ° C fbr 24 h. Separate herbage samples were dried and ground to pass through a l -mm screen for measuring total nitrogen, by the Kjeldahl method, and in vitro disappearance of dry matter (IVDDM) by two-stage rumen inoculum-pepsin digestion.

Soil conditions

The soil physical condition was characterized in the second post-seeding year at Site 1 of Series II. Soil resistance to penetrat ion was measured down to the 35-cm depth of the soil profile, at intervals of 3.5 cm, using a recording

166

penetrometer fitted with a stainless steel 12.9 mm diameter, 30 ° cone (Carter and Kunelius, 1986). Four penetrat ions per plot were made when the soil mois- ture content (26.4 _+ 2.0, w /w) over the 0-30-cm depth was near field capacity. Previous studies have shown that penetrometer resistance measurements are useful for screening soil strength within the root zone and estimating relative differences in soil compaction (Carter and White, 1986; Carter, 1987).

Nematodes

Nematodes were determined in September of the second post-seeding year at Site i of Series II. Soil samples for nematode determinations were composite of 8 cores per plot, taken to a depth of 15 cm with a 25-mm-diameter soil probe. Each sample was mixed thoroughly and passed through a 2-mm screen to re- move roots and other debris. A 50-g subsample of soil was placed in a modified Baermann pan (Townshend, 1963), and up to 10 g of fresh roots from each sample were set in a mist chamber (Hooper, 1970) at 20-25°C. After 7 days, nematodes were identified and counted with a stereomicroscope at 60 × . Soil and root samples were dried for 48 h at 100 °C and nematode counts were ex- pressed as numbers per kg of dry soil and per g of dry root. Nematode data were transformed to logarithms for statistical analysis (Proctor and Marks, 1974; Kimpinski et al., 1984).

Statistical analysis

The experiment was repeated in two series (years) at two sites. For the com- bined analysis over the series, sites were considered fixed effects and series random effects. The resultant analysis of variance was primarily concerned with the factorial effects of sites and t reatments (Table I).

The t reatments were part i t ioned into five orthogonal contrasts (Table I). The first contrast, control vs. t imothy compared the existing control sward (A) with the sown timothy-ryegrass sward (B). The second contrast compared the mean of control (A) and t imoty (B) with the mean of swards of alfalfa (C, D ) and red clover (E, F). The remaining three contrasts involved the factorial combinations between legume species sown and methods of establishment. The contrasts were species, methods of establishment and the interaction between legume species and methods of establishment.

RESULTS

Dry-matter production

In the year of seeding, the average total dry-matter yields for the methods of seeding were 60 and 46% of the control sward for Sites I and 2, respectively

167

(Fig. 1 ). There was no significant difference in total dry-matter yield between the conventional method and direct seeding of legumes (Table II) although direct seeding resulted in higher alfalfa and red clover yield components.

In the first post-seeding year the control sward outyielded timothy by an average of 18%, grasses outyielded legumes by 11% and direct seeding out- yielded the conventional method of establishment by 13% (Table II, Fig. 1 ). The significant sitesX (grasses vs. legumes) interaction was owing to lower yields for legumes (alfalfa and red clover) than grasses (control and timothy) in Site 2 but not in Site 1. Alfalfa and red clover components of total yields in Site 1 exceeded 8 t ha- 1 and there were only small differences among the four treatments (C, D, E, F). In Site 2, the alfalfa and red clover components for direct drilling (C, E ) were 3.4 and 5.6 t ha- 1, and for the conventional method (D, F) 2.5 and 3.7 t ha -1, respectively.

In the second post-seeding year, grasses and legumes had similar total dry- matter yields in Site 1 but in Site 2 grasses outyielded the legumes (Table II, Fig. 1 ). The significant site X (alfalfa vs. red clover) interaction was the result: of higher total yields of alfalfa (C, D) than red clover (E, F) in Site 1 but not in Site 2. The method of establishment had little influence on alfalfa (9.3 t ha -1 ) or red clover (6.2 t ha -1 ) component yields in Site 1. Alfalfa (C) and red clover (E) components in Site 2 were greater for direct seeding than for conventional establishment (D, F) with grass component compensating for lower legume yields.

Legume density

The method of establishment had no significant (P> 0.05, data not tabu- lated) effect on the density of legume seedlings in the seeding year ( 177 m 2). However, in the first post-seeding year mean density at Site 2 was 187 m -2 for the direct seeded legumes as compared to 82 m -~ for the conventional estab- lishment. Winterkill was more severe with the conventional establishment re- ducing the persistence of legumes in Site 2 only.

Total nitrogen of herbage

In the seeding and post-seeding years, swards with alfalfa and red clover (C, D, E, F) had greater total N concentrations than control and timothy (A, B) (Tables II, III ). The significant sites X (grasses vs. legumes) interactions were owing to greater differences in total N of grasses vs. legumes in Site 1 than Site 2 in the seeding year. In the first post-seeding year, this response was reversed. In the post-seeding years alfalfa had slightly greater total N concentrations than red clover. Direct seeding resulted in greater total N than conventional establishment of alfalfa and red clover.

168 10-

SEEDING YEAR [ ] OTHER Q GRASS

8- • LEGUME 1" SEM

14 s S EEDING YE 12

/ I I I I I

i - n SEEDIN

SITE 1 SITE 2

Fig. 1. Total dry matter and component yields in the seeding and post-seeding years. The methods of establishment are: (A) control, (B) conventionally-established timothy, (C) direct-seeded al- falfa, (D) conventionally-established alfalfa, (E) direct-seeded red ch)ver, (F) conventionally- established red clover. Standard errors of the mean for total yield (n = 8) are 0.40, 0.47 and 0.32 t ha r for the seeding, and first and second post-seeding years, respectively.

TA

BL

E I

I

Mea

n s

qu

ares

of

anal

ysi

s o

f v

aria

nce

ii)

r to

tal

dry

-mat

ter

yiel

ds, t

ota

l n

itro

gen

co

nce

ntr

atio

n,

and

in

vit

ro d

iges

tib

ilit

y o

f d

ry m

atte

r ( I

VI)

DM

)

So

urc

e o

f v

aria

tio

n

Deg

rees

of

To

tal

dry

mat

ter

yie

lds

( ×

10 :

~)

To

tal

N c

on

cen

trat

ion

IV

DD

M

free

do

m

See

din

g

1st

po

st-

2n

d p

ost

- S

eed

ing

1s

t 2

nd

S

eed

ing

1s

t p

ost

- 2

nd

y

ear

seed

se

ed y

ear

yea

r p

ost

- p

ost

- y

ear

seed

yea

r p

ost

- y

ear

seed

se

ed

seed

y

ear

yea

r y

ear

Ser

ies

(yea

rs)

1 <

0.1

14

.6

116.

4 7.

1 29

9.1

280.

7 25

066

1005

54

2257

S

ites

1

64.3

21

0.8

376.

9 86

.2

140.

3 37

4.5

2688

5 19

295

9466

R

esid

ual

(a)

1

2.1

13.6

45

.4

8.5

17.6

80

.8

7558

51

1 19

471

Tre

atm

ents

5

65.0

**

12.4

"*

8.5*

* 22

0.4*

* 14

6.4"

* 11

2.7"

* 99

9*

1735

" 13

583*

* C

on

tro

l (A

) vs

. ti

mo

thy

(B

) 1

26.3

**

21.0

"*

0.2

58.6

37

.1"*

0.

2 99

0 26

87*

1008

G

rass

es (

A,

B)

vs.

leg

um

es (

C,

D,

E,

F)

1 26

7.8*

* 9.

6*

27.1

"*

452.

2**

633.

4**

492.

8**

3052

**

4477

**

4364

8**

Alf

alfa

(C

, D

) vs

. re

d cl

over

(E

, F

) 1

29.9

**

3.0

6.3*

* 18

.4

26.2

* 39

.1"

38

13

03

19

701*

* D

irec

t (C

, E

) vs

. c(

mv

enti

on

al (

D,

F)

seed

ing

1

1.2

24.9

**

5.3*

40

4.5*

* 35

.2**

31

.3"

869

180

3128

"*

Leg

um

es ×

met

ho

ds

of

esta

bli

shm

ent

1 <

0.1

3.

6 3.

4*

168.

5*

0.3

0.1

47

30

431

Sit

es×

tre

atm

en

ts

5 1.

5 10

.3"*

9.

2**

54.5

67

.2**

20

.2*

661

655

1629

"*

Co

ntr

ol

vs.

tim

oth

y

1 0.

1 5.

7 <

0.1

20

.4

0.8

1.6

173

176

43

Gra

sses

vs.

leg

um

es

1 6.

1"

31.4

"*

37.7

**

187.

3"

259.

6**

58.1

"*

942

528

1 A

lt'a

lfa

vs.

red

clo

ver

1

0.1

4.9

6.1"

* 18

.5

40.8

**

25.6

16

68"

205

2557

**

Dir

ect

vs.

con

ven

tio

nal

se

edin

g

1 <

0.t

7.

2*

1.9

10.6

34

.5*

11.9

19

2 53

0 50

34**

L

egu

mes

X m

eth

od

s o

f es

tab

lish

men

t 1

0.9

2.4

0.5

35.8

0

3.6

331

28

51 l

[~es

idua

l (b

) T

0 1.

3 1.

8 0.

8 '2

7.'2

4.

9 7.

7 36

9 56

0 26

3

......

Sig

nif

ican

t at

th

e il.

05 a

nd

(L

!)l l

evel

s, r

esp

ecti

vel

y.

170

TABLE lI1

Tolal nitrogen concentration I g kg ~} of harvested herbage for various m e t h o d s o f establishment in two sites averaged over experiments started in 1981 and 1982

Method . t Seeded ~l)ecies Seeding year 1st post-seed year 2nd post-seed year establishment

Site l Site2 Mean Site l Si te2 Mean Site1 Site2 Mean

IA) CnntmI (Existing sward) 25.1 20.9 23.0 22.4 24.3 23.4 22.2 20.0 21.1 (B) Conventional Timothy 29.4 22.0 25.7 19.9 22.5 21.2 21.6 20.3 21.0 {C} Direct seeding Alfalfa 31.9 33.2 32.6 31.6 26.8 29.2 29.8 24.8 27.3 lI)) C¢mventional Alfalta 25.9 22.6 24.3 31.5 23.7 27.6 29.8 22.2 26.0 IF] } Direct seeding Red clover 30.1 30.6 30.4 28.6 26.9 27.8 27.5 24.1 25.8 (F) C(mventional Red clover 27.7 29.5 28.6 28.7 24.1 26.4 26.4 22.3 24.3 Standard errors of the mean: Method of establishment (n = 16 ) 1.30 0.55 0.69 Sites × methods ~t' establishment I r~ = 8 i 1.84 0.78 0.98

TABLE IV

In vitro digestibility of dry matter (g kg ~ ) of harvested herbage for various m e t h o d s o f establishment in t w o

sites averaged over experiments started in 1981 and 1982

Met hod ~1' Seeded species Seeding year 1st post-seed year 2nd post-seed year establishment

S i t e l S i t e 2 Mean S i t e l Si te2 Mean S i t e l Si te2 Mean

(A} Control (Existing sward) 703 674 689 708 739 723 724 741 733 (B) C~mventim~al Timothy 688 668 678 685 725 705 733 755 744 IC) Direct seeding Altalfa 690 663 677 682 711 696 661 671 666 ID) Conventional Alfialta 682 653 667 673 716 694 657 713 685 {El Direct seeding Red clover 701 645 673 702 711 707 709 704 706 IF/ C.nventional Red clover 688 648 668 693 711 702 705 725 715 Standard errors of the mean: Method ~fl' establishment I n = 16 ) 4.8 5.9 4.1 Sit es × met hods of establishment ( r7 = 8 ) 6.8 8.4 5.7

In vitro digestibility of dr), matter

Although there were some significant orthogonal contrasts for IVDDM the differences owing to the treatments were generally small (Tables II, IV). The IVDDM of grasses was higher than that of legumes in the 3 years. The IVDDM in the second post-seeding year was slightly higher for red clover than alfalfa and conventional establishment resulted in higher IVDDM than direct seed- ing. The IVDDM of alfalfa in Site 1 was considerably lower than that of red clover but in Site 2, differences between the legumes were small which resulted in significant s i te× (alfalfa vs. red clover) interaction. The significant

171

CONE RESISTANCE (KPa)

0 0 500 1000 1500 2000 T ~ t F

SEM H

10 H *

20 M H O

I--t *

• TIMOTHY 30 O RED CLOVER I I

• ALFALFA

I--I

Fig. 2. Variation of cone resistance with soil depth under t imothy, alfalfa and red clover swards at Site 1 in the second post-seeding year. Cone resistance under t imothy represents an average of the control and conventional seeding (A, B ); and an average of the direct seeding and conventional es tabl ishment for alfalfa (C, D ) and red clover (E. F ). Asterisk indicates significance at ( P < 0.05 ) for species.

TABLE V

Effects of methods of es tabl i shment on nematode populations in red clover and t imothy

Method of Host Tylenchorhynchus Heterodera Prab'lenchus spp. es tabl ishment plants spp. ( S tunt ) No. tri[olii ( Root-lesion )

kg ' of soil (Clover cyst) No. No. kg ~ No. g kg ' of soil of soil of root"

Control T imothy 800 :/80 1060 4590 Direct seeding Red clover 430 1470 ;5200 11161)

T imothy 300 1640 2940 7510 ConventionaP' Red clover 240 7570 8160 7910

T imothy 4950 Orthogonal contrasts ( [ ' < 0.05) NS C. C1, C~ N.S.

"Stunt and clover-cyst nematodes were not detected in most of the root samples. ~'Root counts for Pratylenchus spp. in al ternate rows of red clover and t imothy in each plot were analyzed separately. Soil counts were analyzed as one t reatment . "Orthogonal contrasts: C~ = control vs. methods of establ ishment . C:~ = conventional vs. direct seeding.

172

si te× (direct vs. conventional seeding) interaction was mainly due to high IVDDM for conventional establishment in Site 2.

Soil conditions

The cone-resistance profiles, measured in the second post-seeding year when the soil was near field-capacity moisture content, were generally similar be- tween the conventional and direct seeding, except over the 7-14-cm soil depth where direct seeding resulted in slightly (<300 kPa), but significantly (P < 0.05) higher soil strength relative to conventional seeding. The main dif- t'erences in cone-resistance values were found between the forage species (Fig. 2 ). This was associated with a slightly lower soil-moisture content, at the 10- 20-cm soil depth, under alfalfa (26.7%, w/w) compared to the t imothy (29.2%, w/w ). Under all establishment methods, a relatively high soil strength ( > 1800 kPa) was evident at the 35-cm soil depth.

Nematodes

The numbers of stunt nematodes ( Tylenchorhynchus spp. ) in soil were quite low in all plots, and there were no significant differences in population size among the t reatments (Table V). In contrast, the soil populations of juvenile clover cyst nematodes (Heterodera trifolii) were greatest in the conventional tillage plots. There were no significant differences in the populations of root- lesion nematodes (Pratylenchus spp.) in roots between the direct seeding and conventional establishment. The soil populations of root-lesion nematodes were significantly higher in the seeded plots than the control, and were larger for the conventional method than direct seeding.

DISCUSSION

Rejuvenation of' pastures and hayfields is often necessary to maintain ade- quate density of productive species in swards. In this study, direct seeding of alfalfa and red clover resulted in dry-matter yields and herbage quality similar to or higher than those for the conventional method of establishment. This agreed with a previous study on the establishment of Italian ryegrass under similar conditions (Kunelius et al., 1986). Direct seeding also resulted in higher alfalfa and red clover component yields than the conventional method in the year of seeding. There was no indication that unsown (other) species were more prevalent in direct-seeded than conventionally-established swards.

In the post-seeding years, direct seeding resulted in similar or slightly higher dry-matter yields than the conventional method of establishment. These re- sults are in general agreement with those by Bartholomew et al. ( 1981 ), Koch et al. (1983) and Mueller-Warrant and Koch (1980) who found only small

differences between the methods of establishment. Winterkill due to heaving was more severe for conventionally-established than direct-seeded legumes at Site 2 which lowered the dry-matter yields. This may have implications in selecting appropriate sward renovation methods. Koch et al. ( 1983 ) also found that direct-seeded red clover was less prone to heaving than clover established conventionally.

Dry-matter yields in the seeding year were as much as 54% lower in the renovated swards than in the existing control sward. There was, however, an increase in total N concentration of harvested herbage which would improve the nutritional quality of swards renovated with alfalfa or red clover. The dif- ferences in IVDDM, although significant between grasses and swards reno- vated with legumes, were small and probably would not be of significance in practical feeding programs. Dry-matter production in the post-seeding years for direct and conventional seeding in Site i with higher clay content was sim- ilar to that of the N-fertilized control (150 kg N ha 1 yea r - t ) , a rate similar to one established in a previous study (Kunelius and Campbell, 1984). The fact that nitrogen-fertilized grasses in Site 2 outyielded the swards renovated with alfalfa or red clover suggests that available management options for sward improvement warrant examination before proceeding with sward renovation. Seeding t imothy with ryegrass in a cultivated seed bed did not increase yields over the control. Considering potentially large reductions in herbage availa- bility, any renovation work needs to be carefully considered for potential gains particularly in sites with productive existing swards (Kunelius et al., 1982). When renovation is undertaken it is essential to choose adapted cultivars for the specific environment and anticipated use and to follow appropriate man- agement practices.

Cone-resistance profiles allowed a rapid screening of the soil condition within the root zone, and determined the depth to the compacted subsoil (Carter and White, 1986). Soil-resistance values, within the 0-:35-cm soil depth, indicated that the various establishment procedures had not adversely affected the soil condition. Based on relationships between soil s t r en~h and soil porosity, es- tablished for similar soils (Carter, 1987), the macroporosity of the 0 25-cm soil depth would range from 8 to 26% (v/v) . Generally the results agree with an earlier study (Carter and Kunelius, 1986) which indicated that direct drill- ing into existing swards provided an adequate surface mulch to reduce soil compressibility and excessive soil compaction.

The data on plant-parasitic nematodes suggest that there were small differ- ences in nematode populations between direct seeding and conventional til- lage. The lower soil populations of root-lesion nematodes under direct seeding agrees with previous observations by Fortnum and Karlen ( 1985 ). In contrast, Thomas (1978) found that numbers of root-lesion nematodes were higher in maize (Zea rnays L.) roots and soil in no-till plots. As plant parasitic nema- todes can have a significant effect on host species ( Mercer and Campbell, 1986 )

174

t h e b i o l o g y o f p l a n t n e m a t o d e s u n d e r d i f f e r e n t so i l c u l t i v a t i o n a n d m a n a g e - m e n t s y s t e m s w a r r a n t s f u r t h e r s t u d i e s .

I t is c o n c l u d e d t h a t t h e y i e l d s a n d h e r b a g e q u a l i t y we re n o t m u c h i n f l u e n c e d

b y t h e m e t h o d o f e s t a b l i s h m e n t . S u b s t a n t i a l y i e l d lo s ses we re r e c o r d e d in t h e

f i r s t y e a r o w i n g to s w a r d r e n o v a t i o n in c o m p a r i s o n w i t h e x i s t i n g c o n t r o l s w a r d .

So i l c o n d i t i o n was n o t a d v e r s e l y i n f l u e n c e d b y d i r e c t s e e d i n g , b u t n e m a t o d e

p o p u l a t i o n m a y i n c r e a s e w i t h c o n v e n t i o n a l e s t a b l i s h m e n t .

ACKNOWLEDGEMENTS

T h i s p a p e r is C o n t r i b u t i o n No. 645 o f C h a r l o t t e t o w n R e s e a r c h S t a t i o n . A d -

vice b y Dr . K .B . M c R a e on t h e s t a t i s t i c a l p r o c e d u r e s is g r a t e f u l l y a c k n o w l e d g e d .

REFERENCES

Bartholomew, P.W., Easson, D.L. and Chesnutt, D.M.B., 1981. A comparison of methods of es- tablishing perennial and Italian ryegrasses. Grass Forage Sci., 36: 75-80.

Carter, M.R., 1987. Physical properties of some Prince Edward Island soils in relation to their tillage requirement and suitability for direct drilling. Can. J. Soil Sci., 67: 473-487.

Carter, M.R. and Kunelius, H.T., 1986. Comparison of tillage and direct drilling for Italian rye- grass on the properties of a fine sandy loam soil. Can. J. Soil Sci., 66: 197-207.

Carter, M.R. and White, R.P., 1986. Determination of variability in soil physical properties and microbial biomass under continuous direct-planted corn. Can. J. Soil Sci., 66: 747-750.

Fortnum, B.A. and Karlen, D.L., 1985. Effect of tillage system and irrigation on population den- sities of plant nematodes in field corn. J. Nematol., 17:25 28.

Hooper, D.J., 1970. Extraction of nematodes from plant material. In: J.F. Southey (Editor), Lab- oratory Methods for Work with Plant and Soil Nematodes. Tech. Bull., No. 2, M.A.F.F., H.M.S.O. London, U.K., pp. 34-38.

Kimpinski, J., Kunelius, H.T. and Willis, C.B., 1984. Plant parasitic nematodes in temperate h~rage grass and legume species in Prince Edward Island. Can. J. Plant Path., 6: 160-164.

Koch, D.W., Mueller-Warrant, G.W. and Mitchell, J.R., 1983. Sod-seeding of forages. I. Alterna- tive to conventional establishment. Bull. 525, Agric. Exp. Station, Univ. of New Hampshire, Durham, New Hampshire, U.S.A., pp. 1 29.

Kunelius, H.T. and Campbell, A.J., 1984. Performance of sod-seeded temperate legumes in grass dominant swards. Can. J. Plant Sci., 64: 643-650.

Kunelius, H.T., Harris, W., Henderson, J.D. and Baker, C.J., 1982. Comparison of tillage methods on red clover and ryegrass establishment and production under grazing in the establishment year. N.Z.J. Agric. Res., 10: 253-263.

Kunelius, H.T., Carter, M.R. and McRae, K.B., 1986. Effect of Italian ryegrass establishment methods on yield, herbage quality and soil compaction. Proc. XV Internatl. Grassland Cong., Kyoto. Japan, pp. 605-607.

Mercer, C.F. and Campbell, B.D., 1986. Early invasion of overdrilled red clover seedlings by ne- matodes. N.Z.J. Agric. Res., 29:495 499.

Minton, N.A., 1986. Impact of conservation tillage on nematode populations. J. Nematol., 18: 135 140.

Mueller-Warrant, G.W. and Koch, D.W., 1980. Establishment of alfalfa by conventional and min- imum-tillage seeding techniques in a quackgrass-dominant sward. Agron. J., 72: 884-889.

175

Naylor, R.E.L., Marshall, A.H. and Matthews, S., 1983. Seed establishment in directly drilled sowings. Herb. Abstr., 53: 73-91.

Procter, J.R. and Marks, C.F., 1974. The determination of normalizing transformations for he- matode count data from soil samples and of efficient sampling schemes. Nematologica. 20: 395-406.

Thomas, S.H., 1978. Population densities of nematodes under seven tillage regimes. J. Nematol., 10: 24-27.

Townshend, J.L., 1963. A modification and evaluation of the apparatus for the Oostenbrink direct cottonwool filter extraction method. Nematologica, 9: 106-110.