MR. McIVOR ON GUANO.

New Zealand Times, Volume XXXI, Issue 4832, 16 September 1876, Page 2 (Supplement)

MR. McIVOR ON GUANO.

(From the Lancejleld Mercury, of July 20.) Mr. Mclvor gave another of his lectures on agricultural subjects at the Town Hall, Lancefiekl, on Saturday last. The attendance was good, the large majority of those present being farmers resident in the district. The lecturer chose for his subject “ Guano, and while speaking was followed with evident attention by the agriculturists present. The following is a full report of the remarks of Mr. Mclvor:— ~ t In various parts of the world there exist large deposits of what is generally believed to, be the excrement of sea-fowl, and which we know as guano. According to the climate of the country from which it has been obtained, it retains to a greater or less extent the am-monia-forming. matters originally present m the excrement. The material obtained from the rainless districts of Peru contains almost the whole of the nitrogen originally present in the excrement, whereas the varieties obtained from other parts of the globe have suffered a loss of ammonia and other very soluble constituents proportionate to the humidity of the climate. In some cases the rain has reduced the ammonia to a mere trace. The guanos which have been deteriorated in this way are those of Australia, KooriaMooria, Patagonia, Chili, and Mexico. The principal ash-constituent of guano is “ bone earth,” which, as you all know, is composed principally of phosphate of lime ; it also contains phosphate of magnesia. Guanos containing a fair percentage of ammonia _ are called nitrogenous, and those containing little or no ammonia, and valuable on account of their phosphates only, are classed as phosphatic. The first and most important guano we have to consider is the Peruvian. It is found in immense quantities on the islands off the coast, and on the mainland of Perm. The people of the country have for generations used it as manure for maize and potatoes, and by its means have succeeded in raising large crops of the former on arid and apparently barren sand. The older travellers brought such glowing accounts of the effects produced by the manure to Europe that doubts were entertained as to their accuracy until Baron Von Humboldt, from personal observation, confirmed them. This distinguished scientist visited the deposits in 1801, and, writing' about them, says:—“The guano is deposited in layers 50 feet or 60 feet thick upon the granite of many of the South Sea Islands off the coast of Peru. During a period of 300 years the birds have deposited the guano only a few lines in thickness. This shows how great have been the number of birds, and how many centuries must have passed over in order to form the present deposits.” In one of the islands the guano covers a circumference of three miles, and has a depth of about 200 feet in some places. The annual import into Britain amounted in 1840 to a_ few barrels only 5 but rapidly increased, until in 1865 it had risen to about 237,393 tons, valued at £2,675,995, of which sum the Peruvian Government received £2,529,408. This enormous importation of birds’ dung Mr. Mechi considers to be “ the astounding fact in modern agriculture.” It is worthy of mention that new deposits are just being opened in the south of Peru, which contain, according to recent reports sent in by the Government engineers, no less than 7,000,000 tons of the manure, valued at not' less than £86,000,000. With these few rather interesting introductory remarks, we will at once pass to the consideration of the chemical constitution of the manure. At the outset I may mention that it is far beyond comparison with any other kind of guano as to agricultural value. Its superiority is mainly due to the very large amount of available nitrogen it contains, principally as ammonia. Indeed, it constitutes the cheapest source of ammonia for agricultural purposes. According to the older chemists, the percentage of nitrogen is equivalent to from 15 to 17 per cent, of ammonia. It is very generally believed that the peculiar unpleasant smell of guano is due to escaping ammonia. That this is not the case is a matter of easy demonstration. If any substance evolving ammonia, in quantity sufficient for detection by the nose, be moistened with ordinary oil of vitriol (sulphuric acid) the smell will disappear, owing to the acid having united with the ammonia and « fixed ” it; or, in other words, rendered it non-volatile. On trying this experiment with the guano it is found that even after treatment with acid it retains its odor, proving that to whatever it may be due it cannot be attributed to the slow volatilisation of ammonia or ammonia compounds. According to Sibson a good authority on such questions —Peruvian guano may be exposed to the sun for a considerable time without undergoing any appreciable deterioration through loss of ammonia. The components of guano ranking next in importance to ammonia are the phosphates. When I say ‘‘ranking next in importance " I, of course, do not mean that nitrogen is a more valuable constituent of plant-food than any of the other constituents, for all are of equal value, but that in guano the ammonia is the most expensive component, and that the phosphates have the next highest monetary value. The bulk of these phosphates are composed of the compounds of lime and magnesia, which united constitute the main portion of ordinary burnt hones or hone-ash. Of the two phosphates : the lime compound greatly preponderates over the phosphate of magnesia. The amount of the two phosphates present in the guano may he stated at about 24 per cent. In addition to these phosphates, which are insoluble in pure water, the manure contains what chemists term alkaline salts. What these salts are I will now try to explain. On treating the guano with water these salts, together with almost the whole of the ammonia, pass into solution, and on evaporating the liquid to dryness and heating the residue somewhat strongly for a short time, the ammonia compounds vaporise and pass into the air, leaving the alkaline salts behind as residue or ash. The residue contains soda and little potash, united with phosphoric, carbonic, and sulphuric acids. In the form in which it occurs in the soluble portion of guano the phosphoric acid is of more yalue, owing to its ready solubility, than when in the condition of comparatively insoluble “hone-ash.” As a rule, the guano contains too large a percentage of ammonia in proportion to its phosphates 5 so that when employed in its natural condition for agricultural purposes the result obtained is not commensurate with the ammonia present in it; or, in other words, a guano containing less ammonia would have served the purposes just as well. It is desirable, then, in order to economise tho ammonia which you all know to be a very expensive material —to increase the proportion of phosphates, and this is easily affected by mixing ifc with about half its weight of a good phosphatic guano or fine bone-dust. Sibson advances a very excellent proposal, to mix the guano with soluble phosphate of lime, or, as it 13 called, dissolved bones, or simply superphosphate. He writes:—“ For wheat on light soils one-half superphosphate may be safely substituted with the best results _ • On strong soils where it is intended to cultivate wheat, the mixture should, on account of the retentive power of clay for ammonia, bo composed of two-thirds guano and one-third superphosphate. For root crops, where it is still thought advisable to use guano, I would recommend tho use of a mixture of two-thirds superphosphate and one-third guano, which will be quite sufficient to preserve the effects of the nitrogenous manure ; and I have no hesitation in saying that a sounder and heavier crop will be obtained. I fully agree with Sibson on the advantages of mixing soluble phosphate of lime with Peruvian guano. Peruvian guano contains, as a rule, about 13 to 15 per cent, of water, and a small but inconstant quantity of sand, and other insoluble, agriculturally worthless matters. Ihe following is Dr. Anderson’s statement of the average composition of the guano from the older deposits : Water .. 1? Phosphates f* Organic matter "2 , Alkaline salts . . ![ band . 100 Phosphoric acid In alkaline salts—2J per cent. Nitrogen In organic matter—l 7 per cent. Dr. Yoelcker fixes tho average percentage of ammonia in the older deposits at 14. In

his report to the Royal Agricultural Society of England on the composition of the guano from the newly-opened deposits in Southern Peru, he states that it is somewhat inferior to the old Chincha Island manure. His average percentage of ammonia is lower, and the amount of insoluble matter higher than the island guano. According to my own work on South Peruvian guano, I have fixed upon the following as being a fair statement of its average composition: Sand 3 0 Organic matter 51‘0 Phosphates .. 26'0 Alkaline salts 10'5 Water.. .. 0o 100 0 Ammonia—l 3 per cent. The above is the mean of 17 analyses. The guano from the new deposits is mostly in excellent condition, dry and free from lumps. Prom the analytical statements given it is obvious that the guano is very rich in the most important manurial components of vegetable food, and it may be considered as the most concentrated and richest artificial fertiliser we have. Many—indeed most —of the objections urged against the employment of the manure are to be attributed to its injudicious employment, It is too concentrated and stimulating a manure to be added to laud without care. McDonald speaks truly when he remarks, “ What braudy is to the constitution, so is guano to the soil.” Having thus shortly considered the chemical constitution of the manure, let us now briefly discuss its physical properties and adulteration. In appearance it has, when genuine, a light-brownish red or fawn color. If it be dark, it in all probability contains an undue amount of water. It has occasionally happened that a guano has been moistened with water to increase its weight, but when an undue percentage of water is present, it is more frequently the case that it has been damaged by sea water during the transit. When it has been thus damaged it not only contains too much water, but has suffered a loss of a greater or less amount of its more soluble constituents. Guano damaged by sea water is sold by auction in England. When purchasing a guano the farmer should see that a handful when pressed together does not cohere strongly. It should not possess a strong ammoniacal smell. When, as is generally the case, it is interspersed with lumps, these latter should, on breaking, have a lighter color than the powdery guano. When rubbed between the fingers it should not feel gritty. A bushel of the genuine manure should weigh from 6S to 72; if it weigh more it may have been adulterated. Although these rude tests may convey a very fair idea as to the quality of the guano, they cannot be implicitly relied on, for they are sometimes imitated with wonderful ingenuity by the skilled adulterator, and they are only applicable to the Peruvian guano, because the other varieties are so variable that no general rules can be given for ascertaining their freedom from adulteration. Neither can they be relied on to give an opinion as to the quality of several samples where all are genuine. The only one who can with certainty detect adulteration is the analyst. The adulterants most likely to be employed are sand, carbonate of lime in the form of limestone or air slaked lime, common salt, and light-colored soils. I have found a sample of what was sold as first-class Peruvian guano to contain 60 per cent, of sand and clay. In a second case I found 25 per cent, of carbonate of lime, and 35 per cent, of sand, in a Peruvian guano. The Peruvian is not unfrequently adulterated with cheaper and very inferior guano, when, of of course, the percentage of ammonia will be lowered. It occasionally happens that a guano is imported, which through carelessness in collecting is largely intermixed with sand, clay, and even pebbles. In some cases adulterated and very poor guano is sold by the analysis of a good sample. It is also not unfrequently a custom of manure dealers to make . one analysis serve for many successive cargoes of guano, which, though all coming from one deposit, may vary much in composition. How often do we see worthless materials sold as good manures on the certificate of an unqualified man, who happens in some strange way or other to have got hold of a few letters to parade after his name. By means of these ill-earned or meaningless letters he deludes the farmer, who purchases the article advertised and applies it, only to meet with disappointment. In many instances he acquires a prejudice against chemists which it is difficult to remove. In this way one of the finest of the applied sciences falls in public estimation, and the really well-informed chemist is classed along with quacks. These quacks, having no true scientific education, cannot appreciate the true nature of the vocation of the chemist, and care little about the truthfulness of their reports so long as they get their fees, and heeding not how they lower the social status of the analyst. In defence of my profession I would mention that many of the differences of opinion regarding ordinary chemical analyses arise not through the deficiencies of chemical science, but through incompetency on the part of the analysts—if I can call them such. When you are desirous of having a manure or soil analysed see that you take it to a person who has gone through a proper course of chemical study under good teachers, and not to any ignorant upstart who thinks proper to call himself a chemist. With these remarks let us proceed with our subject. Let us now discuss the value of Peruvian guano compared with farm-yard manure. It is a wellknown fact that when manured year after year with guano, certain soils become unproductive, or, in other words, get exhausted. Erom what I have said in my former lectures you will at once conclude that this exhaustive influence must be due to the large quantity of ammonia contained in the manure. It is obvious from this exhaustive power that guano must have some deficiencies as a general manure, ■ One of these is the deficiency of alkali, and another, which has been already pointed out in the ealier portion of this discourse, is the want of proportion existing between the ammonia and the phosphates. The manner in which this latter difficulty may he overcome has been explained. Again, the. quantity of organic matter added by a large use of the manure does not fully discharge the functions of decomposing organic bodies in tho soil; the main object of such decomposing matters being to assist the solubility of plant food and to improve tho mechanical condition of the soil. As regards certainty of action guano cannot bo compared to good farmyard dung, which from its containing all the constituents of plant food, is effective in all cases. As it, however, is rich in the chief components of plant food removed by the exported produce or by the animals fed on the land, and also as it accelerates the action of dung, it may serve to make up for any deficiencies of tho latter. By thus employing a mixture of guano and dung pasture lands may bo maintained in very good condition for any length of time. Dr. Anderson, writing on the subject, remarks,:—“ln all cases the rapidity of the action of guano makes it an important auxiliary of farmyard manure, and it is in this way it may be most advantageously employed. Experience has shown that half the farmyard manure may be replaced by guano, with the production of a larger crop than by the former alone in its full quantity. Lawos and Gilbert have shown that guano is the best food for wheat, “ but,” they add, “ it is not to be concluded from this that the farmer may with impunity grow large white straw crops by artificial manures without a due supply of farmyard manure to tho land.” When organic matters and some of the ash constituents of plants have accumulated in a soil through the long-continued use of dung, the guano niay bo used alone with very great advantage. In leaving this portion of my subject I need only sum up what has been said regarding guano as a general manure by saying that the larger percentage of certain constituents of plant food it contains renders it a very valuable auxiliary to, but not a substitute for, farmyard dung. Tho well-known agricultural writer, J. C, Morton; proposes to overcome tho deficiencies of guano as a manure by combining its employment with green manuring. He says :—“ Taking the general abundance of alkalies (potash and soda) in the soil into account—substances-in which the guano

is deficient—it may be said to be a perfect manure, excepting in so far as the carbonaceous element is concerned. . . . Perhaps one of the best modes of its application is in addition to a green crop ploughed in for manure, by which vegetable matter in a condition inducing its rapid decay is added to the soil, along with a sufficiency of phosphates and ammonia—the whole forming, in the case of most soils, a perfect replacement of all that a luxuriant crop may be supposed to deprive the land. . . . And very probably, by means of green manuring in this way, at mtervels of three or four years, the deficiencies of guano might be so far supplemented as to permit the cultivator to depend wholly upon it for the fertility of the soil, even in cases where the whole of the crop was systematically removed from the land." Although not quite so faultless as Mr. Morton appears to think, this is is a very good suggestion, and I will subject it to a thorough discussion when I come to lecture on green manuring. The mode of applying Peruvian guano to cereals practised by the home farmers consists in adding it to the young corn as a top-dressing in spring, the land having been manured the year before with farm-yard dung, and a root crop obtained. I must, however, refrain from entering into the question of the application of the manure until I come to lecture on the different crops. I may, however, mention that in using guano, either as as a top-dressing or otherwise, great care should be taken in preparing it for application to the land. The hard lumps should be broken, and the whole reduced to fine powder by beating and sifting. It should then be well mixed with about four times its weight of dry soil. The object of thus mixing it is simply to ensure its more even distribution over the soil, and the better this has been effected the greater will be the effect of the manure on the crop. This even distribution of the guana is very necessary, for by neglecting this precaution tho larger lumps of ° guano, owing to the ammonia present, are likely to "burn" the plants, and thus do serious injury to the crop. We must now take leave of the subject of Peruvian guano, and pass to phosphatic guano. Tho only member of the second class I need touch upon is tho Maiden Island. This is a very good manure of its kind, being exceptionally rich in phosphates. It contains practically no nitrogen or alkalies; and as nitrogen is a necessary constituent of all cereal manures, it is obvious this guano is of little or no value for wheat, oats, or barley. . It will be found to be a good manure for root crops. Writing on phosphatic guanos, _ Sib son expresses his opinions in the following terms : " Even the better kinds of phosphatic guanos, although valuable for conversion into superphosphate of lime (by treatment with oil of vitriol), do not as a rule possess much value in the soil in an unprepared state, since the phosphate of lime they contain is in an insoluble state, and although in some instances, owing to the fine state of division in which it occurs, such guanos give good results on root crops." I fully agree with Sibson on the value of phosphate guano.