MINERAL CONTENT OF PASTURES.

New Zealand Journal of Agriculture, Volume XXXVI, Issue 1, 20 January 1928, Page 22

MINERAL CONTENT OF PASTURES.

PROGRESS OF THE NEW ZEALAND INVESTIGATION.

B. C. Aston,

F.N.Z.lnst., Chief Chemist, Department of Agriculture.

The investigation into the mineral content of pastures in New Zealand has gone steadily forward during the past year, being confined to those areas where deficiency disease due to pasture was definitely known to exist. The analyses of a series of red-clover samples are presented in this article, with a discussion as to the direction in which the results throw light. It is satisfactory to learn that the general conclusions reached several years ago as to the iron-deficiency in the pasture are borne . out by the results of these analyses.

With regard to the occurrence of iron-starvation in countries other than New Zealand affecting animals whose sole diet is natural pasture, it is satisfactory to learn that the authorities in those countries are confirming our experience in the treatment of the disease. It was predicted in 1924 (“ Transactions of the New Zealand Institute,” Vol. 55, p. 723) that the “ pining disease of sheep in the Cheviot district, Scotland, the “ coasty disease ” of Tasmania, and the “ nakuruitis ” disease of cattle in Nairobi, British East Africa, would prove to be the same. This is now becoming verified. In the Australian Veterinary Journal for September, 1927, C. G. Dickinson, B.V.Sc., discusses “ coasty disease ” and finds that it yields to the same treatment as does “ bush sickness ” —the administration of iron and ammonium citrate. Mr. R. E. R. Grimmett reports from the Rowett Institute, Aberdeen, that the “ pining ” of sheep in Scotland is almost identical with the pining of sheep and cattle in certain parts of Auckland Province. He states that the citrate of ammonium and iron lick prescribed by the writer for the cure of affected stock is now being used on pining sheep in the Cheviots with excellent results, and is effecting rapid improvements. Mr. Grimmett further reports that the soil upon which pining develops in North Britain is of the same texture as our Mamaku soila sandy silt. The writer also learns that the nakuruitis disease in Nairobi, occurring on a soil derived from a light-grey volcanic ash, is similarly yielding to the medicinal treatment with iron ammonium citrate.

Methods of Investigation.

The composition of a fodder plant is influenced by three classes of facts (Warrington)—namely, those relating to .(a) the age of a plant, or to the relative development of the parts, leaves, stems, fruit, &c. ; J) the composition and physical condition of the soil in which the plant grows, which includes consideration of the manuring and the climate ; (c) the specific distinctness or the botanical relationship to other plants. It is therefore desirable in studying the mineral composition of pasture to consider the effect of one varying condition at a time, the other conditions being as far as possible kept constant. Accordingly, in the following' account, in an endeavour to arrive at the truth, the inquiry has been limited to three species of plants growing upon three or four types of soil in the same county on both manured and unmanured ground. The stage of growth has been limited to what is

known as well-grazed good cow-pasture, and the samples have as far as possible been taken throughout the whole year. The samples have been carefully selected by Mr. Grimmett or by the writer. They were cleaned of any sandy matter by quickly washing in water, a proceeding which may have resulted in loss of potash and soda, but these were not in any case estimated, and the error from washing in the constituents estimated is probably negligible. After drying, the samples were sent to the Department's Chemical Laboratory at Wellington, where they were carefully picked over, neglecting woody stalks and any material foreign to the species being analysed. In this way it is hoped that the botanical purity may be guaranteed, but that freedom from earthy contamination can be definitely assumed is more than can be hoped. In some cases earthy impurity seemed to adhere so tenaciously to the leaves that it could not be eliminated by washing. After air-drying, the samples were dried in the hot-water oven to a brittle state which enabled the portions to be broken in the hands to a state fine enough for io to 20 gram portions to be weighed with every probability of obtaining a fair sample.

In analysing samples of fodder plants it is desirable to establish the presumption that a sample is pure and free from such contamination of earthy particles as would appreciably affect the' results of any analysis for mineral foods it is sought to estimate. This precaution is especially necessary in the case of elements such as iron and manganese, which exist to a much greater proportion in the. soil than they do in the tissues of the pasture plant which lives on that soil. It is probable that ruminants cannot assimilate such mineral foods when they are present as earthy contamination. Such minerals, it is thought, must first be absorbed and be present in the tissues of the plant before the animal can absorb them.* Iron, for instance, may exist in amounts about r per cent, in a pumice soil, and is extracted by the hydrochloric acid used in dissolving the plant ash. The amount ,of iron (Fe) present in the tissues of dried grass is about o.oi per cent., or one-hundredth of what it is in the soil. It will be easily seen that a very small contamination of the grass with soil will make a very large error in the estimation when the grass ash is analysed. Half a gram of pumice in one hundred grams of dried grass will therefore contribute as large an amount of iron as 0.005 per cent, to the assay, an amount as large as the grass tissue may itself contain, involving an error which therefore doubles the true iron content.

In order, therefore, to guard against the effect of an impurity which all the precautions taken in sampling have not been able to exclude, the results of analysis have been classified into “ contaminated ” and “ uncontaminated ” samples. In the contaminated samples the amounts of iron and of manganese have been given, but these determinations are not to be accepted as representing the natural ash of the plant. On the other hand, the determination of phosphoric acid and lime occurring naturally in pumice soils is so small that contamination does not contribute an error which will swamp general conclusions, and these may. therefore safely be drawn from those determinations of samples contaminated by earth.

In ascertaining from analysis what samples are and what are not contaminated, the writer makes use of two facts —the content of silica and the content of alumina. Silica is absorbed by grasses to a much larger extent than by clovers, so that a different standard is ‘required for each class of pasture plant. When the amount of silica is greater than a certain amount it is valuable evidence of pasture contamination by earthy siliceous matters. The estimation of alumina is especially valuable as a method of determining the purity of a pasture sample., Aluminium always accompanies iron, in New Zealand soils, but it is absorbed by the higher plants—to which the fodders belongonly in very small traces. Hence, if more than traces of aluminium are found in a solution of the ash of a pasture plant one may conclude that it is contaminated by earthy matter, and that the iron determination should be disregarded as probably much too high. Probably also the manganese determination will be in error from the same cause.* As to the manner of stating the results, and the methods used in analysis, the calculations are all stated as percentages of the constituent, calculated on the sample dried in the water oven until the loss on reheating was inappreciable. The method is in conformity with that used by research workers in other parts of the world, and in the writer's opinion is justified by his experience. The methods of analysis used are official or have stood the test of long experience in the writer’s laboratory, and where any method was used other than that sanctioned by official publications it was checked by official methods by another operator.

Attention may again be drawn to the difficulty of obtaining a representative portion for analysis when dry grass or clover tissues of low specific gravity are contaminated with sandy or earthy material of much higher specific gravity. Contaminated samples must therefore be very carefully sampled, and in such cases check assays always made on duplicate weighed portions.

Notes on Results of the Analyses.

The aim in analysing the samples of pasture components was to obtain representative portions of the most commonly occurring plant staples in that condition in which they were actually being consumed by the ruminant. For the present the results reported only refer to cocksfoot-grass, red clover, and white clover. It is hoped to extend the work in the future to other species, to pastures as a whole, and to inorganic constituents other than those upon which the work has hitherto been done.

It should be premised that bush sickness does not in Rotorua County occur on land the topsoil of which is finer than a sandy loam ; further, that although the practice of applying fertilizers, the nearness of the water-table to the surface, the packing of soil particles by running or lake water, and the admixture of “ humus ” may convert a coarse pumice soil to a healthy one for stock, it will be well to regard all soiltypes mentioned herein as suspicious except the external districts’ samples and the sandy loams of those from Oturoa and Te Ngae. Another type of fine soil occurring in the Rotorua district is the silt

* This method was first used by the writer in investigating mortality in lambs in Central Otago. See this Journal for April, 1927.

soil of the Atiamuri Road ; no pasture samples received from there, but it is known to be healthy country. ' : -

RED CLOVERS.

In the uncomtaminated, unmanured samples definite evidence is again obtained of the lack of iron in red clover, an important component of pasture on the pumice lands. The * amounts of lime, magnesia, and phosphoric acid are fairly uniform in all samples. In the contaminated samples, although the iron results must be disregarded, the phosphoric acid, calcium, and magnesium results are valuable evidence. As one would expect, the amount of iron varies as the healthiness of the country ; the healthier the country the more iron, the less healthy the less iron, in the samples. The results of the analyses of white clover and cocksfoot samples will appear in succeeding issues of the Journal.

Explanation of Chemical Formulas, &c., in Tables.

“ Ash ” is the residue obtained on burning the dry matter in a porcelain basin over an Argand burner at the lowest possible temperature, and finishing the combustion in a gas muffle furnace. CO 2 is the amount of carbon dioxide (carbonic acid gas) obtained on boiling the ash with dilute hydrochloric acid and absorbing the dried gas in soda lime. SiO 2 is the total silicon dioxide (silica) obtained by dissolving the ash in hydrochloric acid, evaporating to dryness repeatedly, and separating by filtration. Fe 2 O 3 is the total amount of ferric sesquioxide (iron oxide) estimated by two methods.

P 2 O s is the total phosphoric anhydride (anhydrous phosphoric acid) estimated by two methods. CaO is the total amount of calcic oxide (lime).

MgO is the total amount of magnesic oxide (magnesia). Mn 3 O 4 is the total amount of manganoso manganic oxide (manganese oxide). N is the total amount of nitrogen. A1 2 O 3 is the total amount of aluminium sesquioxide (alumina). The words “ manured ” and “ unmanured ” are used to designate samples from land which has not been dressed with artificial fertilizers. In the classification of samples one cannot guard against the possibility of the samples having been manured by stock-droppings. (To be continued.)

Poultry-farming. — Referring in his last annual report to the census of poultry in New Zealand the Chief Poultry Instructor (Mr. F. C. Brown) remarks : “ The most gratifying feature in the returns is the increased number of people keeping large flocks, or, in other words, sufficient to provide the whole or greater part of a livelihood. In 1921 ninety-six people kept flocks ranging from 500 to 900, and fortyone kept 1,000 and over, whilst in 1926 there were 148 and sixty-six respectively. With the advanced knowledge now available relative to the breeding and management of large flocks, an extension of large plants may be looked forward to with confidence.”

Tree-planting Companies.— Last year’s annual report of the State Forest Service states that the boom in the formation of private and public tree-planting companies and syndicates, which commenced definitely in 1923, reached its climax in 1925, and only three new companies were formed during 1926. Of the thirty-six private and public companies registered in New Zealand, eighteen continued or commenced planting operations during the year, and established 51,242 acres in new plantations. Of this area, 50,937 acres were planted in the North Island and 305 acres in the South Island, bringing the total area planted to date to approximately 70,000 acres. ,

* Experiments with salts of iron in combination with mineral acids alone suggest that these are not so assimilable as those in organic combination.

Laboratory No. Locality. Date. Ash. 2 . SiO. 3 j P2O5. j MgO. M113O4. N. O 3 . Remarks. Kabak aka, Mamaku, and Ngongotaha Mountain. 200-acre paddock. * Highest part of road Summit of mountain Hillside in bracken. T W W W W W 1042 851 1202 1002 1047 1196 Mamaku... Kapakapa Road Ngongotaha Mountain Kapakapa Road Mamaku . . 10/2/26 9/11/26 20/1/27 29/11/26 14/12/26 12/1/27 9-26 10-67 ’ 9’50 8-6o 8- • 91- • 2-12 2-i-77 . i-97 i-97 o-io o-io O-IO 0-12 0’09 O-II 0-014 0-012 o-oii 6-oo8 o-oio 0-009 0-69 o-8o . 0-67 0-48 0-58 0-62 .0-56 '2-04 2-i-75 1-87 1-71 0-67 o-75 o-6o 0’65, o-8i 0-012 O-OII 0-012 o-oio o-oio 0-015 0-016 3'63 4-20 3’54 23’23 3-3-28 0-020 0-020 0-018 0-026 o-oio 0-019 0-029 w 34 Ngongotaha 3 o /3/26 9-59' 2-03 0-13 o-oi 1 2-32 Average ..- 9-40 1-97 o-ii o-oii 0-63 1'92 0-70 0’012 3’43 0-020 Ngongotaha.Wet land. In flower. 1042 851 1202 1002 1047 1196 34 Mamaku .. Kapakapa Road Ngongotaha Mountain Kapakapa Road Mamaku . . Ngongotaha 10/2/26 9/11/26 20/1/27 29/11/26 14/12/26 12/1/27 30/3/26 Kapakc 9-26 | 10-67 9’50 8-6o 8-6i 9’31 9'59 ipa, M 1- 5 2-2-06 i-77 i-97 2:tmaku, o-io o-io o-io 0-12 0-09 O-II 0-13 and N 0-014 0-012 o-oix 0-008 o-oio 0-009 o-oi 1 gongotaha Mov 0-69 1 2-04 o-8o : 1-77 0-67 2-03 0-48 i-75 0-58 1-87 0-62 1-71 0-56 2-32 mtain. 0-67 0’75 o-6o 0-65 o-8i 0-012 O-OII 0-012 , O-OIO o-oio 0-015 0-016 3-63 4'20 3’54 3-3-23 3-28 0-020 0-020 0-018 0-026 o-oio 0-019 0-029 200-acre paddock. Highest part of road Summit of mountain Hillside in bracken. Average 9'4° 1-97 o-n o-oii 0-63 I-92 0-70 0’012 3'43 0-020 AV w w 843 1036 13°° Streamside 3/11/26 . 10/12/26 14/1/27 9-99 8-92 7'79 1-82 i-86 1-63 A/ 0-14 0-20 0-19 wngota} 0-016 0-016 0-016 0-016 0-015 o-93 0-72 o-54 2-08 2-31 i-6o 0-71 0-91 0-64 o-oio 0-008 ' 0-007 4- 6 7 3’33 3-96 0-019 0-025 0-031 0-015 a. o-93 0-72 0’54 2-08 2-31 ; i-6o 0-71 0-91 0-64 o-oio 0-008 0-007 4- 6 7 3’33 3-96 0-019 0-025 O-O3I Wet land. In flower. Average 8-90 1 77 0-18 0-016. o-73 I j 0-75 0-008 3-98 0-025 Oturoa w w w w 1033 1303 246 408 Muir’s 10/12/26 14/1/27 22/6/26 . 22/7/26 9-69 10-03 8-99 10-01 2-06 6 1 • 1’34 1-08 0-15 0-13 0-18 o-oio 0-008 0-023 0-016 0-58 0-52 o-8i 1-05 2-1-62 i-34 o-6i 0-58 ' 0-46 0-69 0-017 0-012 0-015 0-016 2-96 2-96 0-023 0-022 burn Three-year-old Average 9-68 1 1-66 0-15 1 0-014 o-74 1-76 o-59 0-015 I 1 •• 1 Te Ngae. 2004 Gee’s 7/4/ 1 7 , 10-69 1 0-21 Te Ngae. I 0-021 1 o-88 j 2-01 1 0-70 | 0-012 1 4'74 10-030 1 r o-o2i • o-88 2-01 1 0-70 0'012 1 4’74 ! 0-030 1

Table 1.- Analyses of Red Clovers, Uncontaminated and Unmanured.

Laboratory No. Locality. Date. Ash. co. SiO O. Fe 3 P2O5. CaO. MgO. O. 4 3 N. .O 3 Remarks. Oturoa. R 1085 farm . 23/2/24 12-03 3-03 0-26 0-026 0-48 2-71 o-75 0-018 2-78 0-038 W 839 3/11/26 12-13 2-36 0-09 0-012 0-89 2-00 o-73 o-oi6 0-051 Elevated situation, growth backward. >> Average 3/11/26 . 12-13 12-08 2-36 2-69 0-09 0-18 0'012 0-019 0-89 o-68 2'00 2-35 o-73 o-74 0-016 0-017 0-051 0-044 Elevated situation, growth backward. Mawtaku. - Average 12-08 2-69 0-18 0-019 o-68 2-35 o-74 0-017 0-044 Mamaku. W 40 Jackson’s . . 1/4/26 9-67 2-01 0-19 0-012 o-6o 2-28 0-20 0-018 0-055 w 42 200-acre 10/4/26 9'47 1-90 0-12 0-013 o-6x 2-08 0-77 0-016 3-85 0-070 w 314 22/6/26 0-26 0-015 0-89 1-25 0-014 w 357 19/7/26 8-33 0-89 0-40 0-022 o-94 x-x8 o-oxo Unimproved. w 488 18/8/26 8-89 i-i5 0-013 1-02 i-33. 0-41 I w 848 2/11/26 . 10-53 1-83 0-22 0-019 0-84 1-90 0-76 0-018 4-33 0-038 w 1038 10/12/26 . 10-48 2-02 0-30 0-017 0-78 2-29 0-70 0-016 4'51 0-042 Average 9-56 1-63 0-25 0-016 o-8x 6 o-57 0-015 4’23 0-051 Te Ngae w 54 Smith’s 5/4/26 -48 2-55 o-54 0-028 o-55 9 0-63 0-022 0-053 w 316 25/6/26 9'09 1-31 o-57 0-022 0-79 1-26 0-71 0-012 .. 25/6/26 9-09 1-31 o-57 0-022 o-79 1-26 0-71 0-0X2 w 564 Gee’s .28/8/26 10-89 1-68 o-45 O-O32 0-98 1-71 o-oio 4-64 Average 10-49 1-85 0-52 0-027 o-77 2-05 0-67 0-015 Kapakapa and Kaharoa. Kapakap a and Kaharoa. w 34i Road Kapakapa 8/7/26 8-6i 0-43 0-013 0-76 1-05 I w 342 Kaharoa . 8/7/26 9-04 o-95 0-83 0-040 0-72 1-64 3 0-026 farm. .. Brain’s farm. w 561 Road Kapakapa 3/9/26 10-01 ' 1’47 0-28 0-020 0-90 i-43 0-72 0-012 0-042 Average 9-22 I-2I 0-51 0-024 o-79 i-37 o-93 0-016 N Swampy paddock. w 3ii Lakeside 23/6/26 10-20 o-37 0-016 0-78 1-90 0-82 0-034 Swampy paddock. w 363 23/7/26 9-78 0-8 x-68 0-78 0-035 w 484 >> 19/8/26 10-95. i-35 0-46 0-021 1-02 i-54 o-8o 0-029 0-036 Average 10-31 0-42 0-019 0-87 1-71 o-8o 0-033 0-42 0-019 0-87 1-71 o-8o 0-033 - . . ■

Table 2.-Analyses of Red Clovers, Contaminated and Unmanured.