PROFESSOR BLACK'S LECTURE.

Clutha Leader, Volume XXI, Issue 1043, 20 July 1894, Page 3

PROFESSOR BLACK'S LECTURE.

There was a very large attendance at the meeting of the Balclutha Literary Society held in M'K^nzie'.s Hall on Friday evening last, when Professor Black, of Dunedin, delivered a lecture on ' Agricultural Chemistry,' in the course of which he made analytical reference to the properties of the different manures in the market?. Amongst those present were a. con siderable number of farmers from the neighboring districts. Tho 'president, Dr Fleming, briefly introduced the lecturer. Professor Black, who received a very cordial reception, after a few preliminary remarks, prodeedod to deal with his subject proper, commencing first with oxygen. Oxygen was found in great abundance in the earth, and in the air 20 parts In every 100 was oxygen. The air also contained nit- j rogen, but nitrogen would not combine directly with anything else. Oxygen was very powerful, and iron wire would burn in it, the ash which j remained being iron sand, the same as was to be found on the West Coast about New Plymouth. When phosphorus was burned in oxygen it produced phosphoric acid, which only required the addition of limo to become phosphate of lime. In 100 tons of limestone there were 44 tons of carbonic acid gas. There were two ways i of getting rid of the carbonic acid gas. One was to burn the stone and the other was to put in a strong acid, such as muriatic acid. Carbonic acid gas was a constituent of the air, and the part from which the plants got their food. Plants breathed in carbonic acid gas and gave out the same volume of oxygen, thereby purifying the air. The most expensive man urn in use was phosphorus. If them were one or two parts of phosphorus in 1000 parts of soil, the soil was considered good. Phosphorus came into the soil from the rocks, which contained large quantiti.s of it, and which were broken up by the action of the weather. The soil also contained phosphates, which went into the plants. Since crops required phosphates it was essential there should be phosphorus put into the soil, since it only contained very little. If they kept on cropping and taking out phosphates it was only a question of time when there would be too little, left to raise any crop. A 50l>ush. crop of wheat, would take 101 bof phosphates out of an acre of soil ; a 70 bushel crop | of oats took 101 b phosphate.?, so would 6 tons of potatoes, 20 tons of turnips, 50 bushels of barley, 1400aal of milk, or a dozen ordinary sheep. Therefore, if they continued* taking it out by cropping and did not put it back their land would in time become too poor. If there was plenty of everything else and a deficiency of phosphates in the land the deficiency would rule thrir j crop?. Their land was very much like a , banking account, if t.hny kept on taking out and not putting in there would soon be nothing left. He would advise them always to put more phosphates in the land than they took oui. Of course if they had leased land and they were near the end of the lease it didn't matter. — (Laughter.) The question was, how were they iioinp; to put the phosphates in again i One hundred pounds of bone dust contained 10lb of phosphate, therefore if they put in that, amount they would have as much as they took out. A hundred pounds of bone-dust would cost 6s or 7s, so that the price' of about three bushels of wheat would replace what they took out. There werp, however, two kinds of bone-dust. The fh'st was made of bones without the latter being boiled or steamed. If they were boiled or steamed half the ammonia was removed, and ammonia was more valuable than phosphates. It was worth 15s a unit, and as there was 4 per cent, in bor.e-dust, bone-dust <vas worth L 3 a ton for its ammonia alone. If they took out 2 per cent, it was only worth 30s a ton. With regard to guanos, Peruvian guano was a favorite manure in England for a number of years. Tt was rich in ammonia, containing 15 or 16 per cent., worth about Ll2 a ton for its ammonia. The guano with which they were acquainted down here did not contain much ammonia. Coral Queen was worth about 15s a ton for its ammonia, Maiden Island 8s or 9« a ton, and Chesterfield 17s or 18s. Maiden Island contained 55 or 60 per cent, of phosphates, so it was richer in phosphates than bone-dust. Guano was also more soluble in soil than bonedust. Coral Queen contained 53 to 60 per cent, of phosphate of lime. Chesterfield was a good guano in many ways. It contained 30 to 50 per cent, of phosphate of lime. By the Act passed two years ago every purchaser was entitled to an analysis of the manure he was buying, so as to test the one with which he was supplied by the vendor. This would cost 7s 6rl, and if the vendor charged too much the buyer should ask him to reducw the price in accordance with the analysis. He would say, however, there was little fault to find with the vendors in Dunedin. One thing about Chesterfield Island guano which helped to explain its good results was that it contained 40 to 50 per cent, of carbonate of lime, which was a splendid thing for limeless lands. They should not, however, pay too much for it, for lime itself was cheap. Another good manure

was hasic slag, which was made in the ! manufacture of step]. Up till about two years ago all agricultural experts thought that plants could not take in anything from the soil except ib was dissolved, l»ut it had sincn been discoverrd that this was not the case. To take in solids, however, they must be very fir oly powdered. There were several kinds of superphosphates, some of which would dissolve in water, j while others would not. Superphosphates made from bones should contain 2 per cent, of ammonia, while, other superphosphates did not contain nny ammonia. It was therefore essential that fanners should get a guarantee with their superphosphates. The various kinds of superphosphates varied greatly in price. Sulphate of lime contained.3o per cent., which at 2d a unit made it worth 5s a ton ; raw phosphate up to 20 per cent, at Is 6d a unit 30s a ton J j . and soluble phosphate up to 36 per cent, at 4s a unit L7 a _ton. Let them suppose two farmers sending cattle to the butchers. One reared his own calves and the other brought them lean on the land and fattened them off. The former would take the most phosphate of lime from the land as fattening did not take any phosphate out of the land. Up till sevfu or eight years ago it was supposed that plants could not take nitrogen in from th» atmosphere. Then a German experimrntialist discovered that under certain circumstanc s plants of the pea tribe had the pow»r of getting nitrogen from the air. Many of them havo noticed knots on the r.)ots of peas, clover, and plants ot that nature. It was long thought they were a disease but some years back it wr^s discovered that they were composed of a terrific number of microbes. It was also found that the life work of these microbes was to feed on the nitrogen in the air, and the plants had the power of absorbing the nitrogen from the microbes and taking it to themselves. This threw a light on what every farmer knows, namely that old clover ground w a s the best on which to grow wheat. No one, however, knew why this was so till the discovery was made relative to insects. It was strange thatonly plants of the leguminous order or pea tribe had the property he bad mentioned. The question was had they the microbes in New Zealand. It was found that clover would not grow well in new soil. Field experiments showed that leguminous plants had not the power of using ammonia though they were able to use nitrogen. Perhaps it was the case tliAt they had got so used to the microbes doing the work for them that they were not now able to do it for themselves. What then was the remedy 1 Suppose they saw a good field of leguminous plants ; let them get some soil from it and spread it over their own soil. This had been done in the old country and there were now factories for the preparation of this microbe. An experiment had been recently conducted respecting this. A piece of soil was analysed and a leguminous crop was grown on it. The soil and crop were afterwards analysed and were found to contain more nitrogen than there was in the soil to begin with. The cultivation of leguminous plants were therefore useful for taking the nitrogen out of the air. This class of plants included peas, beens, vetcnes, lupines, most of the clovers, etc. In conclusion he had to thank them all for coming out in such large numbers and for listening so attentively to his lecture, particularly on such a cold night. On the motion of Mr J. W. Wilson, the professor was accorded a hearty Tote of thanks for his lecture.