Background to the Invention

Sethoxydim (hereafter referred to by its trade name, "Sertin®") is a known selective herbicide, for controlling monocot (grass-type) weeds in dicot crops. In 1989, Sertin® was entered into the cereal tolerance screens of the Agricultural Chemicals Evaluation Scheme (ACES) of the Department of Agriculture at Mallala and Sheaoak Log, as a Weed Science Unit (WSU) entry. It was found that volunteer cereals, although being monocots, often escaped control with this herbicide when it was applied to grain legumes to control grass weeds (the approved use for Sertin®) .

At the time, officers of the WSU were working on a project, the aim of which was to derive herbicide recommendations to control brome grass selectively in cereal crops.

Although Sertin® has only a weak effect on brome grass at commercial rates, it was reasoned that, if Sertin® was adequately tolerated by cereals at relatively low rates, it might represent a herbicide that could be used successfully, in a herbicide mixture with other selective herbicides active against brome grass in cereals, to control the weed.

It was surprisingly found that, when applied at lower rates than recommended for herbicidal use, Sertin® stimulated the yield of cereal crops, in particular certain wheat varieties .

Sertin®, or 2-( l-ethoxyiminobutyl)-5-[2- (ethyithio)propyl]-3-hydroxycyclohex-2-enone, is a representative member of a group of herbicidal hydroxycyclohexenones (or cyclohexanediones). A further group of herbicidal compounds, being the aryloxyphenoxypropanoates, have a similar mechanism of herbicidal action. Both groups of

compounds are known selective herbicides, for controlling monocot weeds. Accordingly, other hydroxycyclohexenones and aryloxyphenoxypropanoates were also tested to see whether (a) they were tolerated by cereal crops, and (b) they increased cereal crop yield.

As these compounds are, in general, selective for monocot weeds, it is surprising that they should prove beneficial to cereal crops, in the absence of weeds.

Summary of the Invention

According to one aspect of the invention, a cereal crop yield stimulating composition is provided. This composition comprises a herbicidal hydroxycyclohexenone, cyclohexanedione or aryloxyphenoxypropanoic acid compound, or a salt thereof, together with agronomically acceptable excipient(s) . The concentration of active ingredient may be less than for a corresponding herbicidal composition.

According to a further aspect of the invention, the yield of a cereal crop is increased by administering to the crop or its environs a herbicidal hydroxycyclohexenone, cyclohexanedione or aryloxyphenoxypropanoic acid compound, or a salt thereof. The rate of application may be lower than that recommended for herbicidal use.

For example, for crop yield stimulation, sethoxydim is preferably applied at the rate of lOg to lOOg active ingredient/hectare, or about 50ml to 550ml of the commercial formulation (Sertin ^® ) per hectare. (The commercial formulation comprises 186.8 g/L sethoxydim.) Herbicidal rates of application generally range from 500ml to 2L per hectare.

It should be noted that incorporation of a spraying oil or a wetter increases the crop stimulating effect, so that the rate of application of the active ingredient can be further decreased.

The compounds of the present invention may be used to stimulate crop yield of cereal crops, such as (but not limited to) wheat, barley, triticale, oats, rye and rice.

The herbicidal hydroxycyclohexenone or cyclohexanedione compound may be, for example:

TM Common Name Chemical Name

Sertin ^® sethoxydim 2-(1-ethoxyiminobutyl)-5-[2-

(ethylthio)propyl]-3- hydroxycyclohex-2-enone

Select® clethodim 2-[ 1-(3-chloroallyloxyimino)propyli

5-[2-(ethylthio)propyl]-3- hydroxycyclohex-2-enone

The herbicidal aryloxyphenoxypropanoic acid compound may be, for example:

TM Common Name Chemical Name

Fusilade® fluazifop 2-[4-(5-trifluoromethyl-2- pyridyloxy)phenoxy] propionic acid

Assure ^® quizalofop 2-[4-(6-chloroquinoxalin-2- yloxy)phenoxy] propionic acid

Verdict ^® haloxyfop 2-[4-(3-chloro-5-trifluoromethyl-2- pyridyloxy)phenoxy] propionic acid

Topic" chlorazifop 2-[4-(3,5-dichloro-2-pyridyloxy) phenoxy] propionic acid

It has been found that the compounds of the present invention can be mixed with some other selective herbicidal compounds, such as metribuzin (4-amino-6-tert.butyl-3- methylthio-1,2,4-triazin-5(4H)-one) , without any substantial adverse effect on the selective herbicidal activity of those other compounds. Accordingly, the compounds of the present invention may be applied during spraying of cereal crops for

control of weeds - there is no need for farmers to depart from their normal crop spraying regime.

Under South Australian conditions (mid-north of the State) . the crop stimulation compounds are preferably applied at the two to three leaf stage, through to the early tillering stage, of the cereal crop. For later ^* maturing varieties, application at the mid-tillering stage is preferable, on available evidence. Under other conditions (e.g. in other countries), the timing of the application may vary outside this range, e.g. early- to mid-jointing stage. However, it is not essential for the compounds to be applied during these stages, and some modification is possible, to fit in with normal spraying patterns for weed control.

Detailed Description of the Invention

The following examples are presented as illustrative, but not restrictive, of the present invention.

Exam le ;

ASSESSMENT OF SERTIN* IN WHEAT - 1989

SUMMARY

Sertin* (sethoxydim) is a widely used "grass selective" herbicide in grain legumes and pastures. However some tolerance of cereals, particularly wheat, has been indicated because volunteer cereals have proven difficult to control with this herbicide in some situations, at lower rates. This screen was carried out to find support for this effect

Sertin* (186 g/L sethoxydim) was applied at 250, 350 and 500 ml/ha plus oil (1 L/ha D-C-Tron*) when the cereals were in the 5-6 leaf stage at both Mallala and Sheaoak Log.

Wheat: Results were variable both between varieties and between sites. Yield was stimulated in Blade, Cocamba and an un-named advanced breeder's line - C8MM/45/3 - at Sheaoak Log, but yield was . reduced in Cocamba and C8MM/45 3 at Mallala. The yield of Tatiara was badly reduced at Mallala and marginal at Sheaoak Log. Conversely the yield of Machete was reduced at Sheaoak Log but was markedly stimulated at Mallala - up to a remarkable 181% of the untreated control in the 350 ml ha treatment Yield was also stimulated in Sunfield, Schomburgk, Molineux, Aroona and Oxiey at Mallala. Meaned over all the varieties, the yields showed wheat was tolerant of Sertin* up to 350 ml/ha and marginal at 500 ml/ha.

ASSESSMENT: Cereals 1989

CHEMICAL: SERTIN* a± 186 g/1 SETHOXYDIM

SITE: Site 1 Sheaoak Log. Red-brown earth, pH 7.5, silty loam.

Site 2 Mallala. pH 8.5, silty sand.

RATE OF APPLICATION: Rate l 250 ml -h 1 L D-C-TRON in 150 1 water.

Rate 2 350 ml + 1 L D-C-TRON in 150 1 water.

Rate 3 500 ml -1- 1 L D-C-TRON in 150 1 water.

All rates used at both sites. Treatments carried out at the 5/6 leaf stage of the wheat

Yields: expressed as a percentage of control.

Wheat

Key * significant at the 5% level

** significant at the 1% level

NOTE: Results analysed by variety only - no statistical comparison between varieties can be made.

These tests showed that, at the rates used, Sertin® stimulated the yield of certain wheat varieties. Tests carried out at Mallala were especially successful - there was a maximum 81% increase in yield of the wheat variety* Machete.

Example 2

In 1990, Sertiirwas entered into the ACES screens in. a mixture with the herbicide metribuzin. Metribuzin is tolerated by wheat and barley, and is herbicidally active against brome grass.

ASSESSMENTOFSERTIN*-I-METRIBUZININWHEAT-1990

Metribu- n Sertin mixtures

(SENCOR 480 4- SERTIN - metribuzin 480 g/L + sethαxydim 186 g/L).

Sfte i Mallala silty sand pH 8-5 g _jte 2 Sheaoak Log redbrown earth pH 7.4

Both treatments replicated 4 times at both sites.

_{Sϊte l} Crop sown 19/690. Treatments applied 2/890.

Temperature 14°C, nil cloud cover. Growth stages of cereals:

Oats 3V_ leaf. Barley 4-5 leaf. Wheat 3V_ leaL Triticale 3V_ leaf. Rye 3-3Vi leaf.

_{Site 2} Crop sown 10/7/90. Treatments applied 21/8/90.

Temperature 15°C, 10/10 cloud cover. Growth stages of cereals:

Oats 3V_-4 leaf. Barley 4-5 leaf. Wheat 3-3y ₂ leaf. Triticale 3V_ leaf- Rye 3-3% leaf.

Yields These are expressed as a percentage of the untreated.

WHEAT

NOTE: Results analysed by variety only no statistical comparison between varieties can be made.

It was found that the mixture of Sertin ®and metribuzin also produced yield stimulation effects in wheat, although the pattern was somewhat different to that in 1989 (Example 1).

Example 3

In 1991 , Sertin ® plus oil was tested more comprehensively on five wheat varieties that had shown varying responses to the chemical in the 1989 tests (Example 1) .

ASSESSMENT - YIELD EFFECTS OF SERTIN ON WHEAT

MAT JΛTA AND KAPUNDA 1991

CHEMICAL SETHOXYDIM 186 a.L/1

RATE OF APPLICATION

Rate l 100 mls/ha + 1 1 D.C-TRON oil Rate 2 200 mls/ha + 1 1 D.C-TRON oil Rate 3 300 mls/ha + 1 1 D.C-TRON oil Rate 4 400 mls/ha + 1 1 D.C-TRON oil Rate 5 500 mls/ha + 1 1 D.C-TRON oil

TIME OF TREATMENTS

Time 2-3 leaf ZADOC 12-13 Time 2 6 Ieaf/earlv tillering ZADOC 16-21 Time 3 3-4 tillers ZADOC 23-24

CUϋπVARS SCREENED The following wheat cultivars were used:

MACHETE

SPEAR

BLADE

SCHOMBURGK Y10

TATIARA

SUMMARY OF YIELD RESULTS

The results show that the "successful" treatments, taken as a whole, exhibited a highly significant (at the 1% level) yield increase at both sites - 8.0% at Kapunda and 63% at Mallala. The defined "successful" treatments are:

Kapunda - 100-400 ml/ha Sertin at early tillering (Z16-23) and 100-200 ml/ha at early post emergence (Z12-13) in all varieties.

Mallala - 100-400 ml/ha at early tillering in Spear, Blade and Schomburgk and 100-300 ml/ha at early post emergence in Blade.

A general interpretation is that at Kapunda yield increase in all varieties (maximum 18% in Machete) occurred at 100-200 ml/ha at the 2-3 leaf stage (mean ^• +* ^■ 10%) and 100-400 ml/ha at the early tillering stage (mean +8%). At Mallala 100-300 ml/ha at the 2-3 leaf stage produced rather different effects according to cultivar with Machete being relatively poor, the average over ail cultivars exceeded the untreated by 1%. The 100-400 ml/ha treatments, at the early tillering stage were equal or above untreated (mean +4%). Application at the mid tillering stage -was, generally only tolerated at 100 ml/ha at both sites, except for Tatiara (a late maturing variety) at Kapunda, which not only performed better at this application stage than the earlier varieties (Machete, Spear and Blade) but also better than the earlier times of application for Tatiara.

Table A. Yield as a percent of control - fitted values

Derivation

An examination of the yield results of the 1991 experiments at Mallala and Kapunda, with particular reference to the untreated controls, revealed a pattern in spatial variation, particularly at Kapunda. This led to re-analyses of the results, superseding the simple two-way analyses of variance carried out on the data by Allan Fischle in the preliminary report forwarded to L Black, in which the location of a particular Sertin X variety treatment set of plots may have suggested a statistically significant over- or under-estimate for that particular treatment

To counteract this instability a response surface was fitted to the yields which took account of the location of each experimental plot and its treatment (the cultivar sown, the rate and time of application of Sertin and interactions between these factors). Responses to the six rates of Sertin, including nil, were smoothed by fitting third order polynomials at each time of application. Further, additional data was incorporated from a strip covering all cultivars along one edge of the experiment at Kapunda, which was untreated. These measures dealt effectively with the bias caused by spatial variations.

A multiple regression incorporating spatial terms allowed some of the unevenness in response to come through to the fitted surface rather than presenting an idealised and over-smooth version.

The choice of "successful" treatments was made on the basis of including strongly related groups of treatments. The statistical significance of interactions involving cultivars from the analyses of variance was referred to in discriminating between cultivars to include in a "rates within time of application" group. Selection on an individual, treatment basis would certainly have led to bias.

Table A. Yield as a percent of control - fitted values

^a Fitted values derived from a non-linear analyses of variance, clearly phytotoxic treatments omitted from the analysis.

" Significant at the 1% leveL

METHODS

There were four replicates in a strip-plot design with randomisation of cultivars between replicates. Plot size 2 m x 2_2 m, harvest area 1-25 x 22 m. Growing season sampling was taken from sister plots adjacent to yield plots.

SUBSTITUTE SHEET

1 1

Trea _t ments were applied using a gas-pressurised hand-held 2 m _b oom at 150 L/ha sprav volume. ,

?reϊtments were harvested with a Hege 125C small-plot ^H arves ^t er.

Flag leaf areas were measured as length by maximum width from 24 tillers per replicate. Top weights and root weights (to a depth of 15 cm) were taken at two times using 24 plants per replicate. Soil moisture was taken from each sampling replication to a depth of 15 cm. 1,000 grain weights were measured from a random sample of the grain from each repiicate-

Sites Two sites were used.

Site 1 Mallala - silty sand, pH 83 Site sown 13 June 1991.

Soil moist Treatments applied as follows:

Time 1 2 July 1991. Temperature 16°C, 1/10 cioud cover, soil moist Wheat Z 12-13.

Time 2 25 July 1991. Temperature 14°C, 2/10 cioud cover, soil moist Wheat Z 16-21.

Time 3 2 September 1991. Temperature 15°C, cioud cover 3/10, soil moist Wheat Z 23-24.

Site 2 Kapunda - red brown earth, pH 6.5. Site sown 24 June

1991. Soil moist Treatments applied as follows:

Time 1 18 July 1991. Temperature 13°C, 8/10 cloud cover, soil moist Wheat Z 12-13.

Time 2 15 August 1991. Temperature 14°C, 9/10 cloud cover, soil moist Wheat Z 16-21.

Time 3 18 September 1991. Temperature 17°C. 8/10 cioud cover, soil moist Wheat Z 23-24.

.ASSESSMENTS

Visual assessments were carried out at both sites, as well as soil moisture measurement wt of roots, and wt of tops. On the third assessment the area of flag leaf was also measured.

Site 1 Mallala. Visual assessments carried out 2 weeks, 6 weeks, at booting.

Sampling was carried out on 9 September 1991 and 8 October 1991 at Mallala.

Visual observations

Time 1 2 July 1991. Z 12-13 + 2 weeks

Growth check on all 5 wheat cultivars from Rate 3 to Rate 5.

Rate 5 caused considerable yellowing, rated 7 (EWRC).

SUBSTITUTE SHEET

Z 12-13 -1- 6 weeks

Rates 1-3 all satisfactory. Rates 4 and 5 show considerable mortality.

Z 12-13 on 8 October 1991

Rates 1-3 satisfactory. Severe thinning with Rate 4 of all cultivars and complete kill of all cultivars with Rate 5.

Time 2 25 July 1991 Z16-21 + 2 weeks

Slight retarding of Rates 4 and 5 all cultivars.

Z16-21 -4- 6 weeks

Slight retarding and height reduction for Rates 4 and 5 all cultivars.

Z16-21 on 8 October 1991

Some height reduction of with treatments 4 and 5 for all cultivars except TATIARA

Time 3 2 September 1991 Z23-24 + 2 weeks

Some retarding at ail rates from 2-5. SCHOMBURGK Y10 and

TATIARA least effected.

Z23-24 -t- 6 weeks

General height reduction on all cultivars treated with rates 3-5.

Z23-24 →- 10 weeks

All cultivars reduced in height from treatments 2-5. TATIARA least effected.

Site 2 Kapunda. Visual assessments carried out 2 weeks, 6 weeks and at booting.

Sampling was performed on 11 September 1991 and 10 October 1991.

Visual observations

Z16-21 -- 6 weeks

MACHETE retarded by rates 3-5, SPEAR showed slight reductions at all rates. The remaining cultivars reduced by rates 4-5.

Z16-21 on 10 October 1991

All cultivars reduced in height by Rates 4 and 5. Rates 1-3 generally satisfactory.

Tune 3 18 September 1 ^QQ 1 77.--.-24 + 2 weeks

Slight general retarding all cultivars by Rates 1-5.

Z23-24 + 6 weeks

General retarding of all cultivars. SCHOMBURGK Y10, SPEAR and TATIARA most effected, especially at Rates 4-5.

Z23-24 + 10 w-seks

All cultivars retarded and reduced in height and bulk at Rates 2-5.

Some recovery made by all cultivars with late rain.

SOIL MOISTURE

These were taken at the same time that assessments were made.

There were no differences between treatments and hence the means are given.

Site l Mallala.

Site 2 Kapunda

YIELD RESULTS - RAW DATA

Results are given as a percentage of control yields.

CULTIVAR BLADE - RAW DATA

1.63 t/ha ^b 33.2 g ^c 3.42 t/ha 37.2 g

CULTIVAR TATIARA - RAW DATA

^a 1.84 tha ^b 30.8 g ^c 294 t/ha ^d 36.0 g CULTIVAR SPEAR - RAW DATA

1.92 t ha ^b 31.9 g ^c 3.40 t ha ^d 32.4 g

CULTIVAR SCHOMBURGK YlO - RAW DATA

^a 1.50 tha ^b 33.9 g ° 3.41 t/ha ^d 363 g CULTIVAR MACHETE - RAW DATA

1.81 tha 33.1 g ° 3.14 tha ^d 38.7 g

FT AΓT T FAF APKAS

Flag leaf areas were sampled from Mallala on the 10 October 1991 and at Kapunda on the 16 October 1991.

Because of high variability, only the combined results for the cultivars are shown..

Results are given as a percentage of the untreated control.

R AG T.F AF AR FAS - COMBINED RESULTS, ALL CULTIVARS

VEGETATIVE SAMPLING RESULTS

Root and top weights were sampled as four 025 m ² quadrats per plot and oven dried. Sampling took place on 9 September and 8 October at Mallala and 11 September and 10 October at Kapunda. Note that at Kapunda the second sampling time may not be indicative because the crop was able to take advantage of a late rainfall event on 31 October - 2 November.

Because of high variability, only the combined results for the cultivars are shown, and at the second sampling time. In addition the root weights for Kapunda are omitted as the sampling technique did not allow a depth of 15 cm to be consistently reached in the clay soil- Results expressed as a percentage of control

The yield results show that there was a positive response at certain rates and times of application, and there was less variation in response to Sertin ^® than in the 1989 tests (Example 1). The firm conclusion from the data, after extensive analysis and re-analysis of the data, taking into account (as far as possible) spatial effects of treatment plot location in relation to site variation, was that there was a "real" crop stimulation effect, at specified rates and times .

The 1000 grain weight data was proportional to yield. Therefore, yield increases are not caused by an increase in the number of grains formed in the crop.

Overall, flag leaf area was increased in the successful treatments, indicating that the mechanism involves more efficient photosynthesis at the time of grain filling.

The vegetative sampling results are generally thought to be inconclusive as a result of a fairly crude sampling technique, although at Mallala the data appear sufficiently strong to conclude that root growth in the successful treatments was greater than the untreated. This may mean the crop was better able to exploit the available soil moisture in these treatments, and exhibited this in increased yield.

Example 4

In 1985, Sertin® was tested in the cereal screen at Mallala, although the treatments were not replicated. Tests were conducted to see whether there was a difference between use of oil or use of wetter with a competitor to Sertin® (i.e. Fusilade®) in terms of the chemical's biological activity, as assessed by its effect on cereals. Sertin® plus oil was used as the standard.

EFFECT OF SERTIN AND FUSILADE ON WHEAT - 1985

Site: Mallala

-towing Date: 4 June

Crop Stage at Application 2-3 leaf (Z12-13) of herbicide:

WHEAT - MAT TAT .A - 19R5

YIELD AS % OF UNTREATED fUNREPLICATED .

WHEAT-MATJATA - 10RS

Again, there appeared to be a yield stimulation effect from Sertirr^in certain cases (although rather less conclusive, due to the lack of replication of treatments).

Example 5 ²²

EFFECT OF GROWING SEASON

Sertin has now been used in the cereal variety herbicide tolerance screens for three seasons, and once in a mixture with a herbicide, metribuzin.

The graph below shows that the yield effect of Sertin on wheat in these four seasons is closely related to the degree days in the growing season, with yield stimulation increasing with accumulated degree days.

"Accumulated degree days" is defined as the sum over days of the mean daily temperature minus 5 (degrees C) over the period from the date of sowing until the date when the crop became moisture stressed at the end of the season (the latter estimated from temperature and rainfall data) .

The data shown in the graph exhibit such a strong relationship that a non-abrupt finish to the growing season, or early sowing, appear to be causal.

Further, even in seasons where accumulated degree days are short, as at Mallala in 1991 or Sheaoak Log (SL) in 1989, successful treatments were "safe" in that they did not reduce yield (SL) or gave a mild stimulation (Mallala) .

Effect of Sertin "safe" treatments & degree days in growinσ season for Machete, Spear & Blaoe. c f. untreated

120 - 1038 1-.22

115 1249

Yield no - 1349

105 - ' S-πm- i mβtxiou***-* ^■ β ' 9 105.

100 <3 **'"> ^• «

900 350 1000 1050 1100 1150 1200 1250 1300 1350

DegreeDays

SUBSTITUTE SHEET

SERTINTREATMENTS

SERTIN + METRIBUZINTREATMENTS

The results from 1991 and previous seasons show that wheat yield in stimulated by Sertirt*; the extent depending on the rate, time of application, accumulated degree days and, with less certainty, the variety.

Specifically, 100-200 ml/ha SertirTat the 2-3 leaf stage of wheat, 100-400 ml/ha at the early tillering stage of the crop and, for later maturing varieties, 100-200 ml/ha at the mid tillering stage will either give a yield stimulation or be safe to use on the crop, depending on the accumulated degree days in the growing season, although this may depend on variety.

Further, there is a margin of tolerance in rate and time adjustments that allows farmers, with current levels of expertise, to use Sertirrto improve crop yield, and with current spraying technology.

Example *?

Other herbicidal hydroxycyclohexenone and aryloxyphenoxypropanoic acid compounds were tested on cereals.

ASSESSMENT SCFIEEN OF VARIOUS CHEMICALS ON CEREALS

ChθfnJcsds and rates:

1. Fusalade* 212 g/I at 75mi/ha --ι- wetter

2. Fusilade*» 212 g/1 at 125 ml/ha + wetter

7. Verdict* 104 g/l at 100 ml ha + Dctron oil

8. VerdfcP.04 g I at 175 ml ha + Dctron oil

9. TopicgOO g l at 50 ml/ha + wetter

10. Topi<_i X) g/l at 75 ml/ha •+ ^■ wetter

11. Untreated Control

Sites:

Srte 1 : Mallala silty sand pH 8.3.

Site 2: Kapunda red brown earth, pH 6.5.

Time of AppBcaϋon:

Site 1 : Cereals sown 1«4/06/91.

All treatments applied 68 91. Temperature 14°C, cioud cover 10/10.

Growth stage of cereals:

Site ≥ Cereals sown 25/06/91.

All treatments applied 28/08/91. Temperature 17°C, cloud cover NIL

Actual Growth stage of cereals:

Cereal Rye 6.

Yield Results:

Yields are the mean of 4 replications expressed as a percentage of control yield.

Control yields are shown as the equivalent of TONNES/ha OATS

Site l

Key: significant at the 5% level significant at the 1% level

Site 2

Key: significant at the 5% level significant at the 1% level

BARLEY

Ste 1 - Maβata

Key: ^• significant at the 5% level ^•• significant at the 1% level

Note: High yields for treatments 9 and 10 due to an invasion by wild oats Av na. spp.

Ste 2 - Kapunda

Key: significant at the 5% level significant at the 1% level

WHEAT

Key: ^• significant at the 5% level " significant at the 1% level

sa» 2 - Kapunda

Key: significant at the 5% level significant at the 1% level

Comment

Yields of ail cultivars enhanced by some benefit gained by partial wild oats control. RAC605, SCHOMBURGK and JANZ have had any sensitivity to the treatments masked by low control yields.

TRITICALE

Key: significant at the 5% level significant at the 1% level

Key: ^• significant at the 5% level " significant at the 1% level

CΞtEA YE

Key: significant at the 5% level significant at the 1% level

Although results were inconclusive with respect to some of the compounds tested, these compounds may exhibit crop stimulation effects, if applied at lower rates.

While the invention has been particularly described with reference to preferred embodiments, it will be understood by those skilled in the art that various other modifications and changes may be made, without departing from the spirit and scope thereof, as encompassed by the accompanying claims.