production of lotus corniculatus l. under grazing in a dryland farming...
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Production of Lotus corniculatus L.under grazing in a dryland farmingenvironmentC. A. Ramírez‐Restrepo a c , P. D. Kemp b , T. N. Barry a & N.
López‐Villalobos a
a Institute of Veterinary Animal and Biomedical Science , MasseyUniversity , Palmerston North, New Zealandb Institute of Natural Resources , Massey University , PalmerstonNorth, New Zealand E-mail:c Rumen, Nutrition and Welfare Group , AgResearch Limited,Grasslands Research Centre , Tennent Drive, Private Bag 11008,Palmerston North, New Zealand E-mail:Published online: 17 Mar 2010.
To cite this article: C. A. Ramírez‐Restrepo , P. D. Kemp , T. N. Barry & N. López‐Villalobos (2006)Production of Lotus corniculatus L. under grazing in a dryland farming environment, New ZealandJournal of Agricultural Research, 49:1, 89-100, DOI: 10.1080/00288233.2006.9513698
To link to this article: http://dx.doi.org/10.1080/00288233.2006.9513698
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New Zealand Journal of Agricultural Research, 2006, Vol. 49: 8 9 - 1 0 00028-8233 /06 /4901-0089 © The Royal Society of N e w Zealand 2006
89
Production of Lotus corniculatus L. under grazing in a drylandfarming environment
C. A. RAMÍREZ-RESTREPO1*P. D. KEMP2†
T. N. BARRY1
N. LÓPEZ-VILLALOBOS1
1Institute of VeterinaryAnimal and Biomedical ScienceMassey UniversityPalmerston North, New Zealand
Institute of Natural ResourcesMassey UniversityPalmerston North, New Zealand
*Present address: Rumen, Nutrition and WelfareGroup, AgResearch Limited, Grasslands ResearchCentre, Tennent Drive, Private Bag 11008,Palmerston North, New [email protected]†Author for [email protected]
Abstract A 3-year experiment (from November2000 to October 2003) was conducted at MasseyUniversity's Riverside Farm, in the Wairarapa on theEast Coast of the lower North Island, New Zealand.The study compared, under grazing conditions, theseasonal and annual herbage accumulation rate, andthe seasonal dynamics of ungrazed net herbage ac-cumulation rate of Lotus corniculatus L. (birdsfoottrefoil; cv. 'Grasslands Goldie') relative to perennialryegrass (Lolium perenne)/white clover (Trifoliumrepens) dominant pasture. Prediction equations toestimate standing dry matter (DM) in L. cornicula-tus and pasture from the rising plate meter (RPM)and sward surface height using the sward stick (SS)were also generated. Lotus corniculatus and pasturegrowing in a moderate fertility and low pH soil (pH5.35) accumulated similar total herbage masses
A04056; Online publication date 9 March 2006Received 26 May 2004; accepted 17 November 2005
(24.3 versus 24.1 t DM ha–1) over the 3 years, withthe DM production being greater for L. corniculatusthan for pasture during 2000/01, particularly duringsummer/autumn drought conditions. The net herb-age accumulation rates from ungrazed areas of L.corniculatus and pasture were similar. Pasture andL. corniculatus ungrazed net herbage accumulationrate was at maximum at a herbage mass of 9.9 t DMha–1 (60.23 ± 16.94 kg DM ha–1 day–1) and 5.8 t DMha–1 (15.69 ± 13.25 kg DM ha–1 day–1), respectively,during the spring/summer period. The ungrazed netherbage accumulation rate was lowest, possiblydue to severe moisture deficits, during the summerseason. Monthly and seasonal variation in the cali-bration regressions fitted to estimate herbage mass ofL. corniculatus non-destructively suggested a com-bination of destructive and non-destructive methodsare needed to assess herbage mass. It was concludedthat Lotus corniculatus L. (birdsfoot trefoil; cv.'Grasslands Goldie') has the potential to increasethe performance of a sheep farming system basedon perennial ryegrass/white clover pasture owingto its ability to grow in acidic soils, its tolerance ofregular low summer/autumn rainfall, its seasonal-ity of feed supply, its high feeding value and itsmoderate and beneficial concentration of condensedtannins (CT).
Keywords Lotus corniculatus L.; perennial rye-grass/white clover pasture; herbage mass; swardsurface height; dryland farming systems
INTRODUCTION
Efficient pastoral farming systems maintain or im-prove pasture production, crop growth and animalperformance within the constraints of the socio-eco-nomic and biophysical environments. Nevertheless,biological sustainability and performance of temper-ate areas, which experience regular drought, andglobal warming variability that potentially affectsseasonal and annual productivity and persistenceof pasture legumes, will depend on the use of some
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alternative legume forages that boost opportunitiesfor improved land use and animal production.
Successful dryland farming systems in the Northand South Islands of New Zealand over the last 50years have focused on the introduction of ryegrassand white clover varieties (Brown & Green 2003).However, pastoral farming systems in the drylandregions have not been able to cope with animaldemands, especially during summer/autumn con-ditions, due to the depression in production andpersistence of white clover (Trifolium repens) whenused as the predominant forage legume within aperennial pasture system (Brock et al. 2003; Brown& Green 2003). This has resulted in an oscillationin feed quality and dry matter (DM) production, andconsiderable animal production variability.
The use of tap-rooted perennial legume speciessuch as Lotus corniculatus L. (birdsfoot trefoil; cv.'Grasslands Goldie'), relative to perennial ryegrass(Loliumperenne)/white clover pasture, has been sug-gested as a way to improve the current year-roundsheep productivity in dryland farming environments(Ramírez-Restrepo et al. 2002,2004,2005a,b). Theadvantages of L. corniculatus for summer/autumn-dry areas in New Zealand have been summarised byBarry et al. (2003) as being useful seasonality of feedsupply, high feeding value, moderate concentrationof condensed tannins (CT) and their protein bindingaction, ability to grow in low fertility soils and tol-erance of soil acidity, impeded drainage (Heinrichs1970; Douglas & Foote 1993) and summer droughtconditions (Ramírez-Restrepo et al. 2005a). How-ever, to date there has been a lack of research thatcompares, under grazing conditions, the patterns ofnet herbage accumulation and seasonal dynamicsof ungrazed net herbage accumulation rate of L.corniculatus relative to perennial ryegrass/whiteclover pasture in a dryland farming system in NewZealand. Practical guidelines to estimate averagefarm L. corniculatus cover by the use of rising platemeter units (RPM) and the sward stick (SS; swardsurface height, cm) are not available.
The first objective of this study was to deter-mine the seasonal and annual grazed net herbageaccumulation rates of Lotus corniculatus relativeto perennial ryegrass/white clover dominant pastureover 3 consecutive years in a dryland, commercialenvironment using a systems approach, where plantproduction and effects upon animal productivity(Ramírez-Restrepo 2004) were measured simultane-ously. The second objective was to assess the season-al dynamics of ungrazed net herbage accumulationrate of L. corniculatus and perennial ryegrass/white
clover pasture. The third objective was to developequations to estimate L. corniculatus herbage massby the use of the rising plate meter and the swardstick.
MATERIALS AND METHODS
Location and experimental siteThe evaluation was carried out at Massey Univer-sity's Riverside Farm located c. 15 km north ofMasterton, in the Wairarapa (grid reference; 307374NZMS 260T26) on the East Coast in the lowerNorth Island of New Zealand (lat. 40°50 40 S, long.175°73 00 E) from October 2000 to October 2003.Riverside Farm has a mean rainfall of 1230 mm(recorded at Riverside from 1989 to 2002) with sum-mer/autumn periods (December-April) historicallycharacterised by low rainfall rates, high evapotran-spiration and soil moisture deficits (Salinger 2003).However, it is likely that drought conditions thatprevailed before in 4 years out of a 5-year study onthe East Coast dryland farming systems (Radcliffe1975) will intensify as climate warming continuesowing to westerly circulation (Salinger 2003).
The site was located on an aggradational terracesystem characterised by a Kohinui soil series (Pol-lok et al. 1994). The soil was a medium-texturedstony, free draining soil, 40-50 cm deep (Pollok etal. 1994). Soil tests were conducted before estab-lishment by collecting 20 plugs (20 mm diameter ×100 mm length) across the diagonal of the paddock.Soil analyses were: pH 5.35, Olsen phosphate (P)31.8 µg P/g, sulphate (SO4) 9.9 µg/g, exchange-able potassium (K) 0.40 me/100 g, and soil cationexchange capacity (CEC) 0.83 me/100 g. Furthertests indicated that soil fertility was adequate formaximum growth of L. corniculatus.
Establishment and grazing managementNine hectares of Lotus corniculatus (birdsfoot tre-foil; cv. 'Grasslands Goldie') were established as amonoculture in March 2000 into cultivated ground.Sowing rate was 20 kg ha–1 of coated and inoculatedseed, sown 10 mm deep in rows 150 mm apart witha cone-type plot seeder equipped with a double disc.During the first spring, the legume was sprayedwith herbicide (haloxyfop 300 g a.i. ha–1) to removeinvading grasses. Broad-leaved weeds were control-led during the second winter using 375 g a.i. ha–1
paraquat plus 225 g a.i. ha–1 diquat and 700 g a.i. ha–1
metribuzin. During the establishment phase, nitrogen
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(N), P, K, and sulphur (S) fertiliser were applied at53,35,35 and 28 kg ha–1 respectively. In September2000 and 2003, the crop received 18 kg N ha–1 and37 kg Nha–1 as urea, respectively.
An area of adjoining perennial ryegrass/whiteclover pasture c. 12 years old on similar soil wasused as the control. Under the management plan ofthe farm, this paddock was fertilised with 70 kg Nha–1 and 80 kg Nha–1, as urea, during August 2000and 2003, respectively. In 2001, sulphur superphos-phate (8% P, 19% S) fertiliser was applied at 180 kgha–1.
Both forages were separated throughout the ex-perimental programme into the major botanicalcomponents. The dominant ryegrass content of thepasture sward accounted for 67,68, and 63% of theDM during spring, spring/summer and summer/au-tumn periods, compared with 64,72, and 70% of L.corniculatus in the lotus sward, respectively. In bothswards white clover contribution was estimated as11,12, and 6%, while dead matter and other speciesaccounted for the remainder of the difference in bo-tanical composition. There was no true replicationof forage type (i.e., L. corniculatus or pasture) dueto the systems approach used in this study.
Areas of L. corniculatus and pasture were rota-tionally grazed with sheep at 7-day intervals usingfront and back electric fences. There was no grazingof L. corniculatus during winter and early spring(i.e., May-August) to protect the semi-dormant L.corniculatus, but the perennial ryegrass/white clo-ver pasture was grazed by commercial sheep flocksduring this time. Pre-grazing herbage mass in springperiods was c. 3600 kg DM ha–1 and the post-graz-ing herbage mass was 2100 kg DM ha–1 (Ramírez-Restrepo et al. 2004). In the spring/summer period,the pre- and post-grazing masses were 2900 kg DMha–1 and 2000 kg DM ha–1 (Ramírez-Restrepo et al.2005b). Grazing target for summer/autumn periodswas set at 2700 and 1250 kg DM ha–1 at the start ofgrazing and for residual forage cover, respectively(Ramírez-Restrepo et al. 2005a). The average feedallowance was 7.3 kg green DM ewe–1 day–1 (i.e.,green DM = total DM - dead DM) in lactation,7.0 kg green DM lamb–1 day–1 for finishing systemand 2.2 kg green DM ewe–1 day–1 during the matingperiod.
There were between seven and eight grazingsper year on the L. corniculatus and the perennialryegrass/white clover dominant pasture. Experimen-tal areas of both forages were grazed by sheep ofmixed classes and cattle when there was feed surplusto sheep experimental requirements from spring
to summer/autumn, over the 3 consecutive years.Perennial ryegrass/white clover dominant pasturepaddocks were also mechanically topped duringsummer to remove reproductive stem material andto stimulate vegetative growth.
Plant measurementsThe grazed net herbage accumulation rate (kg DMha–1 day–1) for both L. corniculatus and perennialryegrass/white clover based pasture was measuredat monthly intervals over 36 months using two meth-ods simultaneously. Firstly, eight random quadrats(0.18 m2) were selected, marked and cut to groundlevel using a portable electric shearing hand-piecein a specific area to be grazed c. 30 days later. Ina similar nearby area (i.e., botanical composition,plant density and herbage mass), another set ofeight random quadrats was selected, marked andprotected with wire mesh exclosure cages measuring1.4 × 0.9 m, to be sampled 30 days later to give anestimate of growth over a fixed period. Secondly,the residue after grazing was cut to ground levelfrom eight quadrats and post-grazing herbage massestimated. After 30 days' regrowth, herbage masswas again sampled from eight different exclosurecages. This measurement gave a second measure ofnet herbage accumulation rate and was also done atmonthly intervals. The initial dates of sampling werestaggered so that growth was studied in successiveoverlapping periods of 30 days (Davies 1993).
Ungrazed net herbage accumulation rate (kg DMha–1 day–1) was measured every 2 weeks throughoutfour experimental seasons. Evaluation 1 was con-ducted from 21 October 2000 to 12 January 2001(83 days). Evaluation 2 commenced on 16 February2001 and finished on 27 April 2001 (70 days). Evalu-ation 3 began on 5 February 2002 and finished on15 April 2002 (69 days). Evaluation 4 was between7 October 2002 and 10 February 2003 (126 days).
At the start of each evaluation, six large wiremesh exclusion cages (2 × 0.5 m) were placed per-manently on both L. corniculatus and pasture. Forall evaluations, quadrats (0.18 m2) were positionedin rows within each cage. Harvests for Evaluation1 to Evaluation 3 were cut to ground level. Plantsamples during the fourth evaluation were harvestedfrom initially pre-trimmed areas of L. corniculatus(50 mm sward surface height) and pasture (30 mmsward surface height). Both forages were harvestedto a similar standard sward surface height at eachsampling to ensure optimum plant regrowth. Thus,the estimated profile of ungrazed net herbage ac-cumulation rate was constructed throughout the
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seasons by dividing the difference in net accumulat-ed herbage mass between samplings by the numberof days of the regrowth period. All plant material waswashed to remove soil and faeces, dried overnight(16 h) in a forced-air oven (Contherm; Thermotec2000; Petone, New Zealand) at 80°C and weighedindividually.
Prediction equations to estimate herbage mass(kg DM ha–1) for each type of forage were calculatedfrom a group of 6520 quadrat (0.18 m2) cuts mademainly by one researcher in different transects, whichallowed pre- and post-grazing assessment of herb-age masses over a 3-year experimental programme(Ramírez-Restrepo 2004). There were 3281 harvest-ed quadrats of L. corniculatus and 3239 of pasture.Each quadrat was always measured in the centre ofits undisturbed sward with both the SS and the RPMbefore the sward was cut to ground level. Herbageheight was measured to the highest free-standingpart of the plant to the measuring device includingstems, leaves, inflorescences or seed pods.
After the determination of DM harvested, herbagemass (y) per unit of RPM (units, x) or sward surfaceheight of SS (cm, x) were calculated monthly as theslope component (b) of a linear equation (y = bx)from a simple linear regression with no intercept forboth L. corniculatus and pasture. Therefore, giventhe average RPM reading or sward surface height SSand the month ofthat reading, the average herbagemass could be calculated.
Calibration parameters to reduce the main sourceof variation due to seasonal changes in sward charac-teristics were also analysed from pooled data acrossyears during early spring (August-September), latespring (October-November), summer (Decem-ber-February), autumn (March-April) and winter(May-July), since this provided more observations,especially over winter, and also supplied more ac-curate field data on the productivity under grazingfrom both L. corniculatus and pasture.
Climatic conditionsAnnual and seasonal rainfall and diurnal soil temper-atures (at a depth of 10 cm) compared with 54- and17-year values, respectively, (New Zealand Mete-orological Service 1983), were recorded at RiversideFarm throughout the 3 consecutive years.
Statistical analysesData for annual and seasonal precipitation and soiltemperature were analysed using arithmetic meanvalues. Data for herbage accumulation in each yearwere analysed using the MIXED procedure of SAS
(SAS Institute 2001 ). The linear model included theeffects of forage type (L. corniculatus or perennialryegrass/white clover dominant pasture), month,their interaction and the residual error. Multiplecomparison of least square means for each forage ineach month were performed.
The significance of the differences between for-age type for annual (2000/01,2001/02 and 2002/03),grazed net herbage accumulation rate, or grazedseasonal net herbage accumulation rate in each yearwere not calculated because the study was a systemsexperiment without true replication. Significantdifferences between forage means of annual andseasonal grazed net herbage accumulation rate wereanalysed using PROC MIXED (SAS Institute 2001)with a linear model that included the effect of foragetype. Correlations between grazed net herbage ac-cumulation rate and soil temperature were analysedusing PROC CORR (SAS Institute 2001).
Seasonal patterns of ungrazed net herbage ac-cumulation rate were analysed using the MIXEDprocedure of SAS (SAS Institute 2001), with a linearmodel for repeated measurements that included theeffect of forage type, day, and their interaction. Us-ing the Akaike's information criterion, a compoundsymmetric error structure was determined as themost appropriate residual covariance structure forrepeated measures over time (Littell et al. 1998).
Regression analysis was used for the predictionof herbage mass by the use of RPM or SS calibra-tion equations. Fitness of the model was determinedby the coefficient of variation (CV) associated withthe calibration equation. The CV was calculatedas residual standard deviation (RSD) divided bythe mean herbage mass. Comparison of regressionslopes between L. corniculatus and pasture wereperformed using the PROC MIXED (SAS Institute2001).
RESULTS
Rainfall and soil temperatureMean annual rainfall (November-October) onthe farm was higher than average in 2001/02, but2000/01 and 2002/03 were close to the 54-year av-erage (New Zealand Meteorological Service 1983;Table 1). The summer/autumn season (Decem-ber-April) in 2002/03 was drier than the 54-yearaverage and the other 2 years (Table 1). Over theperiod 2000-03 mean winter rainfall (May-July)was wetter for the last 2 years than the data recorded
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Ramírez-Restrepo et al.—Lotus corniculatus production under grazing 93
at Waingawa climatological station (lat. 40°59 00 S,long. 175°37 00 E), whilst in contrast drier condi-tions were observed during the spring (August-No-vember) of 2001/02.
Annual soil temperature was higher in 2000/01than the other years, with a similar pattern in thesummer/autumn mean soil temperature during thisyear compared to the following years. The averagetemperature of the soil at 10 cm depth in summer/autumn, winter and spring on the farm was higher
by 2.7,42.1, and 47.5%, respectively, relative to thedata at the nearest climate station (grid reference;NZMS 1, 1:63360 N162103596) in the Wairarapafrom 1963 to 1980 (Table 1).
Annual and seasonal dry matter production
Total DM production over 3 years was similar forL. corniculatus and perennial ryegrass/white clo-ver based pasture (Table 2). Annual DM produc-tion of L. corniculatus was greater than pasture in
Table 1 Seasonal and total rainfall values, and mean diurnal soil temperature (10 cm depth) over 3 consecutive yearsat Massey University's Riverside Farm, in the Wairarapa on the East Coast of the lower North Island, New Zealandcompared with the 54- and 17-year average values respectively from New Zealand Meteorological Service (1983).
2000-01 2001-02 2002-03 54-year average4
Summer/autumn1
Winter2
Spring3
Total
Summer/autumnWinterSpringAverage
305307356967
17.210.916.815.8
Rainfall (mm)
4443552731072
Soil temperature (°C)
16.88.8
11.412.9
230339423991
14.79.3
16.513.9
341306324971
17-year average
15.86.8
10.111.7
1Calculated from Dec to Apr.2May-Jul.3Aug—Nov.4Data recorded at Waingawa climatological station, Masterton (Wairarapa) 20 km south of the site.
Table 2 Seasonal and annual dry matter production (t DM ha–1) of perennial ryegrass/white clover (Lolium perenne/Trifolium repens) pasture and Lotus corniculatus L. averaged over 3 consecutive years in a commercial dryland farmingsystem on the east coast in New Zealand. Mean values with standard error (SEM). NS, not significant.
2000-01 2001-02 2002-03
Summer/autumn1
Winter2
Spring3
Annual4
PastureL. corniculatusP
Pasture L. corniculatus Pasture
1.98 4.480.22 0.064.82 3.917.03 8.46
Summer/autumn
3.27 ± 0.873.24 ± 0.66
NS
L. corniculatus
4.19 3.700.81 0.954.97 5.939.99 10.58
Mean production
Winter
0.34 ± 0.240.34 ± 0.24
NS
Spring
4.40 ± 0.494.48 ± 0.73
NS
Pasture
3.640.003.417.06
L. corniculatus
1.560.133.605.30
Annual
8.02 ± 0.988.08 ±1.51
NS1Estimated from Dec to Apr.2May-Jul.3Aug-Nov.4Calculated from Nov to Oct.
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I I I
Fig. 1 Grazed net herbage ac-cumulation rate (kg DM ha–1
day–1) of (O) perennial ryegrass(Lolium perenne)/white clover(Trifolium repens) pasture and (•)Lotus corniculatus L. grown in theWairarapa on the East Coast of theNorth Island, New Zealand. Datacollected from November 2000 toOctober 2003. Bars (I) indicatepooled standard error when foragessignificantly different (P < 0.05).
12 14 16 18 20 22
Experimental months
24 26 28 30 32
Table 3 Comparative slopes (β1) required to formulate a calibration regression (y = β1x) between herbage mass (kgDM ha–1) cut to ground level and plate meter readings (x) for perennial ryegrass (Loliumperenne)/white clover (Trifo-lium repens) pasture or Lotus corniculatus L. n, Observations for analysis; ß„ slope; R2, coefficient of determination;CV, coefficient of variation.
Month
JanFebMarAprMayJunJulAugSepOctNovDec
n
35833739531415211288
160184235306410
P.160.77193.45218.64203.59141.76221.57203.69155.63127.12136.47137.88153.30
Pasture
SE
3.123.043.724.006.557.688.386.755.713.883.073.58
R2
0.880.920.900.890.760.880.870.770.730.840.870.82
CV
37.731.036.336.555.037.543.363.460.150.340.747.4
n
35535940131514311293
156191244314428
P.165.01145.37184.79199.14161.23217.89171.24151.78150.37143.45162.72160.09
Lotus
SE
3.753.834.327.207.629.487.076.013.793.584.083.55
R2
0.850.800.820.710.760.830.860.800.890.870.840.83
CV
42.651.049.262.253.744.839.549.137.641.345.444.6
Significance
NS0.00010.0001
NS0.06NS0.01NS
0.0001NS
0.0001NS
2000/01 and 2001 /02, but was lower than pasture in2002/03 (Table 2). On a basis of total seasonal DMproduction (mean of 3 years), summer/autumn andspring for both L. corniculatus and pasture were themost productive seasons, and winter was the least(Table 2).
Grazed net herbage accumulation rate
Mean grazed net herbage accumulation rate for L.corniculatus and perennial ryegrass/white cloverdominant pasture were similar in both 2000-01 (L.corniculatus; 21.87 ± 1.85 kg DM ha–1 day–1 versuspasture; 17.67 ± 1.88 kg DM ha–1 day–1) and2001-02
(L. corniculatus; 26.08 ± 1.57 kg DM ha–1 day–1 ver-sus pasture; 25.83 ± 1.59 kg DM ha–1 day–1), but lowerfor L. corniculatus (8.00 ± 1.53 kg DM ha–1 day–1)than for pasture (15.44 ± 1.53 kg DM ha–1 day–1; P< 0.001) in 2002-03. The grazed net herbage accu-mulation rate of L. corniculatus was greater than forpasture in December (P < 0.001), January (P < 0.05),February (P < 0.001), and September (P < 0.01) inthe lower rainfall of 2000-01 rather than in the wet-ter conditions of either 2001-02 or 2002-03 (Fig. 1).The negative grazed net herbage accumulation ratesfor some periods in late autumn and winter (Fig. 1)for L. corniculatus (P < 0.05; r = 0.35) and pasture
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Ramírez-Restrepo et al.—Lotus corniculatus production under grazing 95
160-
140 •
120 -
100-
I I I I
13 27 41 55
Experimental days
10 20 30 40
Experimental days
« 20-
sQS 0
I I I I I i I i
Experimental days
Fig. 2 Comparative ungrazed net herbage accumulationrate (kg DM ha–1 day–1) for spring/summer of (O) perennialryegrass (Loliumperenne)/white clover (Trifolium repens)pasture and ( • ) Lotus corniculatus L. Measured from A,21 Oct 2000 to 12 Jan 2001 and from B, 7 Oct 2002 to10 Feb 2003 in a commercial dryland pastoral system inthe Wairarapa on the East Coast of the southern NorthIsland, New Zealand. Vertical bars (I) indicate pooledstandard error.
100-
8 0 -
6 0 -
40 -
20 •
0 -
-20 -
-40 -
B
•
Experimental days
Fig. 3 Comparative ungrazed net herbage accumulationrate (kg DM ha–1 day–1) for summer/autumn of (O) perennialryegrass (Loliumperenne)/white clover (Trifolium repens)pasture and ( • ) Lotus corniculatus L. Measured from A,16 Feb 2001 to 27 Apr 2001 and from B, 5 Feb 2002 to15 Apr 2002 in a commercial dryland pastoral farmingsystem in the Wairarapa on the East Coast of the lowerNorth Island, New Zealand. Vertical bars (I) representpooled standard error.
growth (P=0.06; r=0.33) were associated with lowsoil temperatures in the range 7.0-12.3°C.
Ungrazed net herbage accumulation rateIn Evaluation 1, the highest net herbage accumula-tion rate of ungrazed perennial ryegrass/white cloverdominant pasture, was observed during late springand early summer at a herbage accumulation coverof 6007 and 9982 kg DM ha–1, respectively, but fromlate spring (4053 kg DM ha–1) to the end of the evalu-ation (mid summer; 5280 kg DM ha–1) L. cornicula-tus accumulated less herbage than pasture (Fig. 2A).A similar trend from initially pre-trimmed areas that
removed fresh growth was found in Evaluation 4,with the highest ungrazed net herbage accumulationrate for both L. corniculatus and pasture occurringduring late spring at a herbage accumulation coverof 1766 and 1956 kg DM ha–1, respectively, but frommid November onwards, L. corniculatus also accu-mulated less herbage than did pasture (Fig. 2B).
In Evaluations 2 and 3 over the summer/autumnperiods minor differences in the dynamics of un-grazed net herbage accumulation rate between spe-cies were detected (Fig. 3), with both species havingan ungrazed negative net herbage accumulation ratefor part of the period.
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Estimation of yields
Monthly herbage mass could be predicted for L.corniculatus from plate meter reading units (Table3) or sward surface height (Table 4), with the lin-
71-89% and 67-91% of the variability (R2) in thedataset, respectively. Slopes of the L. corniculatusregressions (Table 3) were consistently differentfrom those for perennial ryegrass/white clover based
ear regression calibration equations accounting for pasture during February, March, September, and
Table 4 Comparative slopes (β1) required to formulate a calibration regression (y = β1x) between herbage mass (kgDM ha–1) cut to ground level and sward stick height (sward height; cm; 1x) for perennial ryegrass (1Loliumperenne)/whiteclover (Trifolium repens) pasture or Lotus corniculatus L. n, Observations for analysis; ß„ slope; R2, coefficient ofdetermination; CV, coefficient of variation.
Month
JanFebMarAprMayJunJulAugSepOctNovDec
n
29832839531415211288
160184222228294
ß.208.60212.60268.62249.12148.78271.45282.28137.20162.19169.84199.94191.42
Pasture
SE
5.024.965.686.388.77
10.5518.9310.517.076.025.876.93
R2
0.850.850.850.830.660.860.720.520.740.780.840.72
CV
41.743.743.945.965.341.464.191.758.859.045.356.3
n
28130436731514311293
156191177237262
ß.168.09139.20181.02189.44134.08275.02194.04162.06149.59164.14189.16181.33
Lotus
SE
4.194.574.936.867.94
11.0513.396.893.374.984.974.99
R2
0.850.750.790.710.670.850.700.780.910.860.860.83
CV
41.856.753.562.363.141.959.252.034.042.341.643.3
Significance
0.00010.00010.00010.00010.0001
NS0.0010.05NSNSNSNS
Table 5 Comparative seasonal slopes (β1) required for the prediction of herbage mass (y = β1x; kg DM ha–1) cutto ground level from plate meter readings and sward stick height (sward height; cm) for perennial ryegrass (Loliumperenne)/white clover (Trifolium repens) pasture or Lotus corniculatus L. n, Observations for analysis; ß„ slope; R2,coefficient of determination; CV, coefficient of variation.
Plate meterEarly spring1
Late spring2
Summer3
Autumn4
Winter5
Sward stickEarly springLate springSummerAutumnWinter
n
344541
1105709352
344450920709352
ß.
134.23137.55162.25211.65170.21
154.32188.77203.45259.62188.43
Pasture
SE
4.332.372.022.734.68
5.904.253.334.257.01
R2
0.740.860.850.890.79
0.670.810.800.830.67
CV
63.044.242.736.551.3
71.051.348.644.964.3
n
347558
1143716348
347414847682348
ß.
150.67153.88157.88189.09177.50
151.81178.43163.11184.23166.78
Lotus
SE
3.102.792.153.764.89
3.003.602.704.046.28
R2
0.870.850.820.780.79
0.880.860.810.750.67
CV
41.744.446.054.649.4
40.242.747.857.562.1
Significance
0.010.0001
NS0.0001
NS
NSNS
0.00010.0001
0.05
1Calculated from Aug to Sep.2Oct/Nov.3Dec/Feb.4Mar/Apr.5May/Jul.
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Ramírez-Restrepo et al.—Lotus corniculatus production under grazing 97
November (P < 0.0001), July (P < 0.01) and May(P = 0.06) reflecting possible changes in the sward,with the L. corniculatus regressions having a lowerslope (P < 0.0001) than in pasture with plate meterreadings over the autumn season, but higher (P <0.01) during the early spring and late spring (P <0.0001) periods (Table 5).
Additionally, slopes to estimate changes in sea-sonal herbage mass cut to ground level from swardsurface height measurements were only higher forL. corniculatus than for pasture in July (P < 0.001)(Table 4), whilst the pooled calibration regressions(Table 5) had consistently lower slopes inL. cornicu-latus than those in pasture during summer/autumn(P < 0.0001) and winter periods (P < 0.05).
DISCUSSION
In a dryland commercial farming system charac-terised by soil moisture stress in summer, the mostsignificant findings were that Lotus corniculatus cv.'Grasslands Goldie' growing in a moderately fertileand acidic soil exhibited similar levels of seasonaland total DM production to that of perennial/whiteclover dominant pasture over 3 years, with both for-ages averaging 8t DM ha–1 yr–1. The annual produc-tion of L. corniculatus ranged from 5.3 to 8.5t DMha–1, which was similar to that reported by Bolognaet al. (1996) in Canterbury, New Zealand. The ratesof ungrazed net herbage accumulation rate (kg DMha–1 day–1) of L. corniculatus and pasture over thespring/summer (Fig. 2) and summer/autumn periods(Fig. 3) differed only slightly in magnitude with thegeneral trend being similar within seasons.
Lotus corniculatus L. had higher DM productionduring the first 2 years than the perennial ryegrass/white clover dominant pasture, with the extra pro-duction occurring over the summer/autumn seasonin 2000/02 and the spring in 2001/02. This did notinclude the 2002/03 year, when the productivity of theL. corniculatus probably started to decline. It is diffi-cult to draw conclusions about the causes that limitedthe herbage mass accumulation of L. corniculatus inthe third year under grazing management. However,field observations suggested that the agronomic per-formance of L. corniculatus during summer/autumnin the last year decreased due to reduced plant popu-lation as a consequence of the grazing frequenciesand/or grazing intensities used. At times the L. cor-niculatus was grazed more frequently and intensivelythan recommended by Ayala (2001) to meet the feedrequirements of the sheep.
Lotus corniculatus L. is largely dependent for itsregrowth upon carbohydrate production from thecanopy photosynthetic area rather than from rootreserves (Turkington & Franko 1980), in contrast toa larger tap-root legume such as lucerne (Medicagosativa). Also, the regrowth of L. corniculatus de-pends largely on active upper axillary branching,whereas lucerne tends to grow from the crown (Nel-son & Smith 1968a,b). The short lifespan of lateralbranches and leaves of L. corniculatus when hardgrazed by sheep results in slow regrowth, whichmight have encouraged weed invasion (Barry etal. 2003). Previously, Van Keuren & Davis (1968),Van Keuren et al. (1969), and Chapman et al. (1990)reported reduced persistence of L. corniculatus un-der grazing management. However, Van Keuren &Davis (1968) also found that L. corniculatus persistsbetter under rotational than under continuous grazingmanagement.
Defoliation height is important for regrowth,especially during summer, when carbohydrate rootreserves inL. corniculatus are recovering after flow-ering (Smith 1962; Smith & Nelson 1967). Greub& Wedin (1971) reported that close defoliation to3.8 cm removed leaf area and axillary bud sites,and increased crown and root diseases. Alison &Hoveland (1989) found yield reductions of 49% incultivars of L. corniculatus after 2 years when thestubble height was decreased from 10 to 3 cm duringspring with a 21-day harvest interval, whilst standdensity of plants decreased by 48%. More recentquantitative studies by Ayala (2001) demonstratedthat 20- to 30-day grazing intervals and 6-10 cmdefoliation heights during spring, and moderate cut-ting heights ( 6 cm) with rest periods during sum-mer, were critical to persistence of L. corniculatus.Defoliation in late autumn and low cutting height(4 cm), or grazing, in winter reduced L. corniculatuspersistence (Ayala 2001). McGraw & Marten ( 1986)found that plant population density (PPD) is criticalin L. corniculatus as it requires a minimum PPD of30 plants/m2 for high DM production.
Natural reseeding of L. corniculatus can be usedto increase the plant population (Bologna et al. 1996;Ayala 2001). A rest period in late summer/autumnevery 3 years to allow establishment of seedlingsfrom natural reseeding would be useful to researchin the Wairarapa environment.
The negative growth rates (i.e., grazed net herb-age accumulation rate) in Fig. 1 for some periodsin late autumn and winter were most likely due tolow soil temperatures, resulting in L. corniculatusand pasture growth that was slower than the rate
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of senescence. Mitchell (1956a,b) and Kunelius &Clark (1970) have demonstrated that the optimumtemperature range for L. corniculatus and pastureis 18-25°C. However, growth of L. corniculatusceases below 9°C and that of perennial ryegrassceases below 6°C (Mitchell 1956a,b; Kunelius &Clark 1970).
No experiments appear to have been reported thatevaluate the growth rates of L. corniculatus and thepotential use of its feed quality to support animalproduction systems under grazing conditions in dry-land environments. Therefore, the high ungrazed netherbage accumulation and net herbage accumulationrate for L. corniculatus during summer (5.8 t DMha–1; 15.69 ± 13.25 kg DM ha–1 day–1), associatedwith its high feed quality from spring to summer(Ramírez-Restrepo et al. 2005c) suggest that therecould be a possibility in New Zealand to produceconserved feeds from L. corniculatus in order tomatch feed supply and feed demand through the year,for grazing ruminants (Ramírez-Restrepo & Barry2005). Further studies are required to define the roleof L. corniculatus in supplementary feeding systemsrelative to ryegrass/white clover based pastures toincrease the pattern of nutrient supply and efficiencyin production under dryland conditions.
The relationship between herbage mass and bothplate meter readings and sward stick height sug-gested that calibration regressions from both pro-cedures are potential options for the estimation ofL. corniculatus herbage mass in spring. In summer/autumn for the semi-erect L. corniculatus, however,neither technique is likely to be suitable; the calibra-tion equations are less accurate in this season, asindicated by their coefficients of determination (R2)and coefficients of variation (CV) (Piggot 1986;Thomson 1986). Thus, the seasonal changes in thestructure and morphology of L. corniculatus makeit unlikely that a simple indirect method for predict-ing differences in herbage mass of L. corniculatusthroughout its growing season can be developed.
The changes in the regression equations pre-dicting herbage mass of L. corniculatus betweenspring and summer are most likely related to theproduction of erect flowering stems and the resultingchanges in the morphological structure of the sward.Various authors (Earle & McGowan 1979; Stockdale1984; Barthman 1986; Thomson 1986; L'Huiller& Thomson 1988; Thomson et al. 1997; Lile et al.2001; Thomson et al. 2001) have reported that cli-mate, forage type, growth habit, plant morphology,botanical composition, plant density, DM content,soil surface, measuring device performance, and
the equipment operator are components of variationthat affect the accuracy of prediction equations forherbage mass. The RPM measures a combination ofplant density and compressed pasture height in smallareas (Hodgson 1990) and SS measures the swardsurface height (Barthman 1986), and these measuresare related to herbage mass, but both methods havebeen developed to be applied on forages with hightiller populations and prostrate growth habit (Hodg-son 1990).
The variability in the perennial ryegrass/whiteclover pasture calibration slopes for RPM and SSsuggests that in dryland conditions further studieson the estimation methods of herbage mass pastureavailability are required, since standard equationshave not been calculated from data collected in thisparticular environment in New Zealand (Piggot1986; L'Huiller & Thomson 1988; Bishop-Hurley1999; Hainsworth 1999).
Radcliffe (1975) and Bologna et al. (1996) statedthat in a dryland environment, DM production ofpasture andL. corniculatus ranged from 8.9 to 14.9t DM ha–1, and from 7.5 to 13.1 t DM ha–1, respec-tively. It is concluded that Lotus corniculatus cv.'Grasslands Goldie' is as productive as perennialryegrass/white clover dominant pasture in the mod-erate P fertility, acidic soil and summer/autumn lowrainfall conditions of the Wairarapa. The use of L.corniculatus, in turn, will allow more efficient pro-duction in commercial sheep farming systems frommating to finishing periods, due to its high feedingvalue (Ramírez-Restrepo et al. 2005c).
ACKNOWLEDGMENTS
The authors gratefully acknowledge Meat & WoolInnovations for financially supporting this study andthe New Zealand Ministry of Foreign Affairs and Trade,Massey University, and the Colombian AgricultureResearch Agency (CORPOICA) for provision ofscholarship support to Carlos A. Ramírez-Restrepo. Thetechnical assistance of Geoff Purchas, Nathan Crombie,and Colin Morgan is greatly appreciated. For advice onclimatic and soil data, acknowledgment is due to GeoffWarren and Neil Kilmister from Massey UniversityAgricultural Services.
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