Must Limestone Be Finely Ground?

New Zealand Journal of Agriculture, Volume 62, Issue 2, 15 February 1941, Page 95

Must Limestone Be Finely Ground?

Recent experiments at Marton have shown that the commercial samples of both the hard and the? soft limestones do not differ significantly in their

effect on pasture yields. It has also been demonstrated that it is not necessary to have lime more .finely ground than is found in the average commercial lines at present on the market.

THERE are three features of agricultural lime about which the farmer should satisfy himself before arranging purchase. These are: (1) The content of calcium carbonate. (2) The fineness of grinding. (3) The “hardness” of the rock. The most important of these factors is, of course, the purity, which is measured by the percentage of calcium carbonate. Good limestones will contain 90 per cent, or more calcium carbonate, while inferior samples will have from 50 to 70 per cent. This factor measures the fundamental worth of the lime, but the importance of the fineness of grinding and the hardness of the rock has, in the past, been less well determined. It has long been recognised that the finer the lime is ground the more rapid is its reaction with the soil and with plant growth. Limestones also differ in formation. Some are naturally hard and difficult to grind, whereas others are softer, and the opinion has been advanced that the latter type would be more reactive and therefore of greater value than the hard rock. It was to discover the effect on the soil and on pasture production of hard and of soft limestones and of coarse and of finelyground samples that a mowing trial was laid down at the Marton Experimental Area in 1934. This trial has been in progress for six years, and the results from it are now available for publication.* Description of The Experiment The trial was conducted' under the mowing and grazing technique! which ensures that the pasture is managed by alternate grazings with sheep and cuttings to . measure production so that it does not deteriorate in composition. The plots of each treatment' were replicated 18 times, .

Recent Tests To Discover The Most Effective Types Of Ground Limestone

By A. G. ELLIOTT,

Crop Experimentalist, and P. B. LYNCH, Assistant Crop

Experimentalist, Fields Division.

Samples of herbage from each treatment at each cut were examined by Mr. B. W. Doak, Plant Chemist, Palmerston North, for the determination of , dry matter. This figure was obtained by drying the green herbage in a gas oven, grinding, and finally drying it under low pressure at 55deg.C. Treatments per Acre 1. No treatment. .... - ...> , 2. Superphosphate 4cwt. per annum. 3.. Superphosphate, 4cwt. per annum + Mauriceville commercial ground limestone (hard). 4. Superphosphate 4cwt. per annum + Waikari commercial ground limestone (soft). 5. Superphosphate 4cwt. per annum + Mauriceville coarse ground limestone. 6. Superphosphate 4cwt. per annum + Waikari coarse ground limestone. 7. Superphosphate 4cwt. per annum + Mauriceville fine ground limestone. 8. Superphosphate 4cwt. per annum + Waikari fine ground limestone. Superphosphate was applied to Treatments 2 to 8 inclusive in two annual

applications of 2cwt. each in the summer and autumn. The amounts of ground limestone applied per acre were as follows:

In all, lj tons of ground limestone were applied to Treatment 3 (Mauriceville commercial lime), i while the quantities of limestone on the other lime treatments were adjusted to give equivalent amounts of calcium carbonate to this dressing. Mauriceville limestone is shelly in character and may be described as “hard,” whereas the Waikari material is formed of a soft deposit known as Globigerina ooze. In an experiment on the effect of these limestones when used with superphosphate to reduce germination injury to turnips*, it was found that the former limestone was relatively slow-acting and too uncertain for use in this connection, whereas the Waikari lime was very satisfactory. To separate the “fine” and “coarse” samples, the commercial material was screened on a sieve with 30 meshes to the inch. The portion retained on the sieve was termed the coarse fraction, and that passing was

The relative cover from coarse and fine fractions. Note that the fine fraction is shown as applied at one-quarter the rate of the coarsely ground material.

the fine material. Analysis showed the percentage of calcium carbonate in these fractions to be as follows:

The amounts of lime applied to the various treatments were adjusted on the basis of these figures.

Botanical Composition Of the Pasture « Perennial ryegrass was the dominant constituent of the sward throughout most of the year, and with white clover these two species contributed the bulk of the pasture production. Other species of relatively less importance were cocksfoot, crested dogstail, sweet vernal, yorkshire fog, brown top, poa pratensis, poa annua, and poa trivialis. The last-named species was occasionally too prominent on the sward to allow of maximum production, and in April, 1935, an attempt was made to

eradicate it by severe harrowing and surface sowing with certified white clover. . This, however, met with little success. The sward was sown down originally before the certification of pasture seeds was introduced, and unfortunately an inferior strain of white clover was used. This was reflected in a pasture with too little clover at most periods of the year, and also in one with rather large amounts of low-producing grass species. Separations of the mown herbage into its species components showed that the effect of lime was to increase the clover-content slightly,

and to decrease the percentage of inferior grasses. Effect of Treatments On Yield of Herbage Table 1 shows the yield of green herbage in each season for the control (Treatment 1) and the response in production to- superphosphate and Mauriceville commercial lime respectively. The differences in black type are statistically significant. To analyse the results statistically we have to use the green weights, but the yields of dry matter are strictly comparable with these. Tables 2 and 3 show the small differences between the types of limestones and their effect on production.

(The differences in black type are statistically significant.) The above tables may be summarised as follows: (a) The response to limestone is not great in comparison with that to superphosphate, but it is definite and consistent. (b) ■ There is no significant difference between the Mauriceville and Waikari limestones in their effect on pasture production in any of the fractions studied. (c) There is no significant difference between the commercial sample and the fine fraction of either the Mauriceville or the Waikari limestone. (d) The fine fraction tends to yield more than the coarse, but the effect is not marked except in the first years of the trial, although it is more sustained in the case of the Waikari lime. It may be concluded, therefore, that the commercial samples of both the hard and the soft limestones do not differ significantly in their effect on pasture yields, nor do they differ from the “fine” fraction. The coarser material is less effective than any of the above types. , ,

No lime was applied after July, 1936, and it will be seen from the foregoing tables that the duration of the lime response was similar on all treatments, although, as expected, the coarser samples tended to make good their disadvantage in respect of pasture production towards the end of the trial period. Mr. Doak in his paper referred to previously, reaches the following decisions based on chemical evidence: —“Ground limestone containing at least 50 per cent, of material passing 30-mesh screen is quite satisfactory and the cost of finer grinding is not justified,” and “for pasture topdressing, hard limestone was as effective as the soft.” These conclusions are fully supported by the yield data. Acknowledgments The thanks of the writers are due to Mr. W. B. Wards, Overseer at the Marton Experimental Area, for the accurate and detailed field work of the trial. The experiment was started by Mr. A. W. Hudson, former Crop Experimentalist to the Department, and has been carried ,on since then by Mr.

J. W. Woodcock and his successor, Mr. A. G. Elliott. The analyses of herbage for dry matter and the soil analyses were carried out by Mr. B. W. Doak, Grasslands Division, Palmerston North. Other Officers of the Grasslands Division carried out detailed botanical analyses of the sward of the trial, and much assistance was freely offered by many officers from the Department of Agriculture and the Department of Scientific and Industrial Research.

Sheep Mortality In Canterbury FOLLOWING the field survey of sheep mortality in Canterbury by veterinarians and agriculturists, it was considered that further progress necessitated intensive investigations on an experimental farm with a bad history, writes the Acting Director of the Animal Research Division in his annual report. Such a farm has been leased in the Kirwee district as from January 1, 1940, and experiments have been initiated to study all phases of sheep mortality which occurs in the Canterbury district, especially in wet seasons. Special attention is being paid to the effect ■of parasite control and various methods of sheep management and feeding. The role played by parasites must be closely studied, and regular chemical analyses of pasture and supplementary feeds are being made. The Canterbury Agricultural College is actively collaborating in this work and is especially interesting itself in the digestibility of pasture and supplementary crops grown in Canterbury.

*A technical paper on this trial will be published in the “N.Z. Journal of Science and Technology.” The soil data has been prepared by B. W. Doak, Plant Chemist, Grasslands Division, and the yield figures by the authors. - t Hudson, A. W. Imperial Bureau of Plant Genetics. . Herbage Plants: Bulletin 11: 1933. .

• * Hudson, Woodcock and Doak: N.Z. Journal of Science and Technology: 1937:. vol. 18: pages. 739-749. '

Treatment. 26/7/34. 18/7/35. 23/7/36. 3 .. 2,240 lb. 336 lb. 784 lb. 4 .. 2,423 lb. 363 lb. 847 lb. 5 .. 2,207 lb. 331 lb. 772 lb. 6 .. 2,392 lb. 359 lb. 857 lb. 7 .. 2,274 lb. 341 lb. 796 lb. 8 .. 2,434 lb. 365 lb. 852 lb.

Mauriceville . (hard) > Waikari (soft) Complete Commercial Sample 92.9 85.9 Coarse Sample 94.3 87.0 Fine Sample . . 91.5 85

Year. Treatment 1 ' (control). Difference in Production between Treatments. Treatments 2-1. Super response. Treatments 3-2. Mauriceville lime response. 3934/35 .. 314.8 68.5 24.0 1935/36 508.8 ■ 128.5 32.8 1936/37 494.5 95.0 13.6 1937/38 : 301.1 62.7 31.8 1938/39 .. : .. .. .. 292.5 87.6 33.5 1939/40 300.7 73.1 . 20.5 Total period 1934/40 .. .. .. period 1934/40 2,212.5 2,212.5 515.4 . " ; 515.4 156.3 156.3

TABLE 1: YIELDS OF GREEN HERBAGE IN CWT. PER ACRE.

Year. Response to Mauriceville Commercial Limestone. Differences in Favour of Waikari Lime. Commercial Sample. Coarse Fraction. Fine Fraction. 1934/35 24.0 ' + 8 0 + 6.9 —3.9 1935/36 .. 32.8 —7.9 —0.1 +0.3 4-0.3 1936/37 13.6 . —2.9 —5.2 + 1.4 1937/38 31.8 —7.8 . —5.4 4-6.0 1938/39 33.5 —2.2 —0.9 —2.3 1939/40 20.5 —0.1 —2.9 +8.8 / Total Period 1934/40 156.3 —12 7 —7.2 4-10.3

TABLE 2: DIFFERENCES IN YIELDS (CWT. PER ACRE) OF GREEN HERBAGE (COMPARISON OF MAURICEVILLE (HARD) WITH WAIKARI (SOFT) LIMESTONES).

Year. Response to Mauriceville Commercial Limestone. Difference in Favour of Fine Fraction. Commercial Sample. Coarse Fraction. Mauriceville Waikari. Mauriceville Waikari. 1934/35 24.0 4-11.5 —0.4 + 26.1 + 15.2 1935/36 32.8 —5.8 . 4-2.4 + 12.8 4-12.9 1936/37 13.6 —4.9 —0.7 4-19.5 + 26.0 1937/38 31.8 —9.8 4-4.0 + 7.5 + 18.9 1938/39 33.5 —6.5 —6.6 • —1 8 —3.2 1939/40 20.5 —2.0 6.7 4-4.9 + 16.6 X +4.9 + 16.6 Total Period 1934/40 156.3 —17.5 4-5.5 + 69.0 4-86.4

TABLE 3: DIFFERENCES IN YIELDS (CWT. PER ACRE) OF GREEN HERBAGE (COMPARISON OF THE EFFECTS OF FINENESS OF GRINDING)