Professor Black's Lectures.

Lake Wakatip Mail, Issue 1518, 5 February 1886, Page 5

Professor Black's Lectures.

AGRICULTURAL CHEMISTRY.

In accordance with a promise made, Professor J. G. Black, on his return from the Head of the Lake (where in company with Mr James Taylor, a member of the Royal College (if Chemistry. England, he paid a visit to the Invincible Co.'s Quartz ami I the Pyrites Co.'s mine), delivered a lecture in the ! School-room, Queenstown, on the 23rd ultimo, the subject being Agricultural Chemistry—during which , a number of tests w ere made. The audience was j rather small, but the lecture—which occupied altout two hours in delivery—was attentively listened to throughtout. The NUyor (Mr Reid) was voted to the chair, and briefly introduced the lecturer. Piofesaor Black said it would be impossible in one lecture to deal fully with such a wide subject, i and he could therefore only make a few suggestions. I and indicate some jxiints in which chemistry wa* ! applicable to agriculture. Firstly, plants depended upon two kinds of food for their growth and sustenance—atmospheric and mineral. Whatsoever came from the gaseous state— carbonic acid being almost entirely the food obtained from the air. The mineral food from the ground was obtained or converted for use only in a soluble condition. Ft instance. tafore a plant could utilise phosphate < f i lime the latt»r must l»e in solution. That was the | earthy food of plants. In 10.000 gallons of air. j however there were onlv about four gallons of j carbonic acid tas. Animals breathed out this tas. | and it was also thrown out by decaying vegetable ! matter, in the burning of coal ami limestone— «>f ! which latter 100 tons contained 44 tons of the acid. j Volcanic discharges also threw off great quantify* j -if it. Kvery a>id strove to *;et lime combined with j it, and when combined the carlionic acid was driven ] out. Carbonic acid was very heavy, but by a law of nature in the diffusion of gases it mixed evenly | with the other elements of the air. The leaves of trees and plants acted as lungs, and the larger the i leaves the greater was the nutriment*—carlionic acid—which found its way through their veins and ti««ues the |>laut-« in their turn throwing off oxygen, which was so necessary for the life of man and the lower animals. One was the counterpart of the other; and an abundance of animal life would produce so much the in<«re nutriment for plan's. (The lecturer then applied some tests and referred to the manner of the growth <>f plants.) Nitrogen also was an essential food of the earth for the growth of plants, although the question had lieen j raised as to whether plants conld not get their | nitrogen from the air ; he believed they c >uld not I get it to any great extent. They might get it from ammonia, of which, for instance, nitrate of soda ) contained a good deal. Guano and other manures j which contained ammonia must not. however, be j mixed with slack or quick lime, as the latter ex- : lulled the ammonia, which thus left the soil. Mr i James Taylor, a gentleman then in Queenstown | (than whom few men knew more of manures), stated | that sulphate of ammonia was greatly used on ! Knglish farms Phosphate of lime was a magnificent : manure and cheap. Lime, phosphoric acid and I potash ncid were the three chief mineral ingredients j necessary for plant growth. Lime existed in various conditions in the earth—the most important being phosphate of lime. Lime played five parts in the constitution of plants. Firstly, it was required as a direct food by leguminous plants, such as clover. Secondly, a lime soil—consisting of carbonate of lime -was often benefitted by a dressing of quick or slack lime. Lime also acted another part in some land which contained too much of obscure acids, as lime, which is the opposite of acid, woul t combine and neutralise the effect of the latter, j Lime also warmed the soil, with which a sprinkling | of it would combine. It was of no use, however, j putting lime on a wet soil. Then, again, all clayey «oils contained potash, but not in solution, which I was necesnary to render it of use to |tota.sh ; but 1 given a little lime and the potash was released, and tl'.e plants thus got lioth potash and lime and magnesia—in fact, the clay changed its ch incter and liecame a rich loam. He would now pass on to phosphorus, which wis death to rabbits and life to plants. The best part of plants was alive with phosphorus—not the straw but the grain, which ; was the most nutritious to animal life. For thousands of years this fact was acknowledged bv men ' of learning in ancient times aud comparatively modern times, but science of late years had pointed or found out the icasoii. Our hones were composed of phosphate of lime—the pro|>ortioo of 56 in every 100 (Hiunds lieing phosphate of lime and the other 44 chiefly gelatine and fat. The phosphate was found in old rocks under various nanu>s, and it was, by the action of frost, rains aud winds, dissolved and carried down in streams—the water containing ammonia dissolving the phosphorus. Carbonic acid iu rain water also dissolved it. Some kinds of spring water w< re not nearly so good a< rain water, because the litter contained much more carl»ouic a- id. Well, we got large quantities of phosphorus from meat, and the question was which is the cheapest souice from which to get it. The grass contained phosphate of lime, but in quantities too small to make it digestible for man The whole energy of the lower animals was expended iu eating and digesting the grass. Man used phosphate of lime in a concentrated form—in meat, in milk, in grain. In this manner he utilised the sheep which contained concentrated phosphate—in fact, the sheep was made to do half the work for us. The more concentrated the food the more intellectual the animal, liecause less strength wai sjient in digesting it. There was a serious aspect of this subject, however. He lielieved conscientiously that the human race had for centuries made a great mist-ike in wasting the phosphorus, and, as a consequence, the world was gradually becoming fearfully iin|iOVerished. The soil was the source of onr food, but its supply cl phosphorus was very limited, and if we got through the supply animal life, as it at present existed, would be impossible. One ton of good soil contained one pound of phosphorus, ; ami a ton of poor soil bl>ont half the quantity of phosphorus. If the first six inches oi land was exhausted the roots of plants could not gut any inore phosphorus. Five bushels of wheat contained a pound of phosphorus, and, therefore, for every five bushels of wheat a man seut off his farm he sent away the nutriment of one ton of soil. If this system of giving away is contiuued, and there is no restoration, it is ouly a question of time as to when . the soil will be exhausted of its phosphorus. But | where, then, did the phosphorus go to? It went chiefly to great cities in the shape o( meat and wheat, it was consumed by the inhabitants, and afterwards carried away in sewers to th« sea, never ' more to be used by the human rSM, by the

comparatively small quantity recovered by man, and contained in the sea birds and fishes which lived on the discarded phosphorised—but invaluable —refuse. In this manner an immense drain had been going on in the old countries. Take England, for instance, whose soil had Iteen worked by man for thousands of years; If phosphates in the form of guano and other manures was not imported into England, very little erain could be grown from the application of a certain quantity. England and other populous civilised countries were draining other parts of the world of their phosphorus by the consumption of imported animals. Look at the animals daily sent to the London market from the north of Scotland. Then take New Zealand, from which grain and sheep are sent to London. Oftentimes the fanner here grow 60 and 70 bushels of wheat to the acres, but he is barely paid for exhausting the soil. It is a loss to send graiu away from land unless phosphate of lime in the shapeof manure or iu some other form is returned to the soil. If this is not done the land mast become comparatively useless—exhausted—and the country sinks iuto insiguifioance. Take, for instance, Babylon ami that great empire which once ruled the world ; also Ninevah and other ancient cities, whose lands are now mere wildernesses. Take old Palestine, which was only about 60 or 70 miles by 25 or 30 miles in extent—in fact, only about size of the ouce province of Southland. It was at one tiina extremely fertile and populous, and we read of ong battle there between 1,300,000 of fine big fightine men. So also in the battle of Jehosaphat. In Judea and Babylon—each about ten miles square—there were about a million of tine meu. But, some may ask, where did these men get the phosphorus from to grow so large! Why, from the soil—from mother earth. In those days 200 bushels to the acre were common, and grapes and other fruit and produce was equally abundant. In those countries at the prt sent day the inhabitants were miserably poor and weak, l»ecause they had nearly used up from the soil all its phosphorus, which had been carried to the sea, never more to be used by the human race. At Home—in the older countries—and even in this colonv we were playing the same game, snl civilisation was bringing a blight over the land. There were one or two exceptions to this deplorable state of things, such as in Egypt and in China— althou.h the soil would have been exhausted iu the former long ago had not fresh phosphates Iteen brought down from the mountains and the laud l>eeii covered by the floods of the Nile. The Chinaman never wastes his phosphorus, for he manures the soil with his sewage. It would be a nice thing to follow China, and to conserve our phosphorus and restore it to the soil. This was iteing done iu Loudon. It was stated, however, that the system did not pav, hut he maintained that it was their duty to conserve the phosphorus. (The learned gentleman then referred to the process gone through in the production of phosphorus.) His friend, Mr Taylor, stited that sugar phosphate i,f lime could be purchased much cheaper at Home than out here, where merchants wanted 100 |«er cent profit. It could be liought in London at £4 13s per ton, and lie recommended the Waikouafi farmers to combine and get a ship load of it. Pi of. Black, after some other remarks as to the effects of exhaustion of the noil in driving the grain-growing settler of Ameri-a to the westward, showed the hearings of catt'e growing upon civilisation. lie sail! it would pay a dealer better to get the cattle after hiving grown on the run ami to fatten them himself, bee one the bones whi h wt-re .row ing in the tirst staue of an animal were composed of the most valuable ingredients on the run, nanu-lv, phosphate of lime ; whilst the lit oily contained charcoal and water, tnit no phosphate, although the lean contained a small portion. Cloxer was very nutri?iou«, Itecause its roots went down deep into the soil perhaps two or three feet—ind the older it was tile more valuable it became —the more nourishing—l»ecause it lifted up the phosphorus. The licturer concluded by saying that, he had only drawn attention to a few facts, showing the connection between chcmistery and agriculture. Fanning was now carried on in the old countries in a systematic manner. Thirty years ago nothing was known of this connection, and little more twenty years ago ; but ten years ago it commenced to make great strides. Iu Canterbury College a great deal of it was taught, but he thought there ought to be agricultural schools in Southland, Waikouaiti and other places, and also an analyst to test and experiment oil the vat ions .soils. Perhaps the colonies were too young for this, but lie believed that, before long, they would see the necessity of taking some such action. (Applause) A hearty vote of thanks was passed to the Professor for his very interesting lecture. Mr Hotop said that one object of the meeting was to form a branch of the School of Mines, already established at Danedin, with the liojie that six assistants would be appointed—two for Otago, two for the Thames and two for the West Coast — and to visit their respective districts periodically. After a few remarks by Professor Black and other speakers, a number of persons gave iu their names as subscribers, and the meeting soon after closed with a vote of tliauks to the chair.