LIME TESTS

Southland Times, Issue 18967, 14 June 1923, Page 6

LIME TESTS

MR R. B. TENNENT AT WINTON. AN INTERESTING DEMONSTRATION. Some interesting lime tests were demonstrated to a gathering of Thornbury farmers at Winton yesterday by Mr R. B. Tennent of the Department of Agriculture. In opening, Mr R. B. Tennent said that he was pleased to see so many present from the Thornbury branch of the Farmer’s Union. Before conducting them round the plots he would give them a few simple demonstrations on. lime. They all knew the three chief forms of lime:—Burnt, carbonate and slack. The first was- about twice the strength of the second, and this was accounted for by the elimination of water and other substances during the burning process. Burnt lime was more active than carbonate and they were aware of the effects water had upon burnt lime. “If I applied sulphuric acid to my hands or clothes,” said Mr Tennent “it would immediately burn. I can stop that by washing the acid off with water, or by applying an alkaline substance.” The lecturer then took soine water and added < an acid to it, immediately neutralising the acid by the addition of an alkaline substance. He explained that an acid would kill an alkali and than an alkali would kill an acid. They could secure at any chemist blue litmus paper which would turn red when dipped into an acid solution. This was one test of an acid solution but there was also the indicator method as well, which ncted differently under acid and alkali conditions. In an alkali solution the indicator turned a bright pink. Mr Tennent then mixed an acid solution and showed the litmus paper and indicator tests. He then added burnt lime which turned the acid solution to an alkali, showing the acidity had been overcome by the application of lime. “The acid conditions rule in most of the Southland soils,” said Mr Tennent, “and that is why we require so much lime in Southland. Burnt lime is quicker in action than carbonate, the former being more soluble and its results quicker, i That is the reason why burnt lime is more i suitable for heavy clay soils. Immediately j burnt lime was spread it is carried into the I soil by rain and moisture. After about five i weeks in the soil the burnt lime turned into , carbonate. Before it turned into carbonate I it spread through the soil and effectively I dealt with the acidity.” He went on to I say that carbonate would do the same work, but was slower in action than burnt i lime. Another argument in favour of burnt ! lime was that one ton of burnt lime was j aproximately equal to two tons of carj bonate. When the lime had to be carted any distance this was a big consideration. In carbonate there was a certain amount, of water and rock water which made up the additional weight, this was left behind in the kiln when the lime was burnt. There was also a certain amount of carbonic ! acid gas in carbonate, which was also elimi inated. When burnt lime was spread it absorbed moisture and carbonic acid gas which gradually converted it into carbonate again. The price of carbonate should be ■out 7-12 that of burnt, that was arrived by calculating the amount of calcium . each. To put soils in a fit condition for plant growth they must get the soils “sweet” or .i other words eliminate the acid conditions L.ud to get that condition burnt lime was the best. There was not a single soil in Southland which did not require lime. But they could apply 100 tons of lime to the acre if they choose, but it would be of no value without proper drainage. Drainage and liming went hand in hand. Lime opened out heavy clay soils making them more crumbly and this was one of the biggest advantages of lime. He then made a clay solution in a bottle and added lime V it made the particles of soil ••s nftrsmttinr better cultiv<ricn.

The addition of lime nAde the particles more granular. “I will show you a simple test which you can all apply to your land,” said the lecturer. He then took a small sample of soil and mixed it with water and tested ‘t with a litmus paper. The solution was too weak to provide a striking result. He recommended then to make a paste of the soil and place it upon a litmus paper protected by blotting paper. The paper would show them whether their soils were acid or otherwise. If the land was sour the paper would come out a bright red, but it was more than possible that the paper would only show’ a pu tinge. This was sufficient ti prove sui. acidtiy. This was a good rough test and worked out really well. The best form of lime to use was a debatable problem. He would recommend those farmers who had heavy clay soils to use burnt line. Firstly, because it was quicker in action; secondly, it was more soluble and distributed itself better through the soil; thirdly, because had certain caustic properties and this burning did considerable benefit to the soil. In the lighter soils, which were poor in organic matter, he would recommend carbonate. On those soils he he would not recommend burnt lime, as it would burn out the organic matter, thus leaving the soil in a poorer condition. In answer to a question, Mr Tennent said that lime always had a tendency to sink, and it had to renewed at regular intervals. “That leads to another aspect” said Mr Tennent. “All plants lived in. the top six inches of soil and it is there that the greatest acidity is developed.” Decayed vegetable matter helped form acidity and also the small root hairs, which exuded a weak acid to change the mineral plant food into solubles so that the plant could assimilate it. Wheat produced a considerable amount of acid and the stubble when turned it also added to the acidity. As the stubble rotted in the ground it produced carbonic acid gas. This gas was also present in the air, and as a certain amount of air existed in the soil it helped on the acidity. All these factors assisted towards the gradual accumulation of acid in the soil. If they spread the lime and turned it in, it would go to deep and the same could be said of harrowing. The best method was to apply the lime and let the rain and moisture dissolve it, and it would thus reach the parts of the soil affected. They were only burying lime by turning it in. Every farmer should be able to say how much lime his paddocks required. He should have that knowledge at his finger tips and when asked should be able to say “My homestead paddock requires so much lime. My lea so much and my stubble so much.” They could have this knowledge if they wanted it. The Department of Agriculture would tell them to a pound how much lime their paddocks required if the forwarded samples of the soil for analysis. They could obtain those samples by digging four or five holes in the paddock and sending a sample of the soil to the Department. They could manure as much as they liked but unless they limed they would not get the returns. Superphosphate was a decidedly acid manure, and when applied to acid soils only made them worse. Basic super and basic slag was what should be applied to sour lands. The results would be slower as they were not so soluble. Carbonate could be used for top dressing, but it was not so good as lime and superphosphate, which had the most beneficial effects upon pasture.

Another questioner asked if, as rotting vegetable matter added to the acidity of the soil, would Mr Tennant be against cover crops being ploughed in. Mr Tennent in reply said that the benefits derived from ploughing in a cover crop far outweighed the acidity set up by the decay. The ploughed in crop assisted to change the texture of the soil from a sticky to a fine open one, which was easily worked and better for plant growth. A cover crop provided a great amount of nitrogen. He was not against the ploughing in of crops and would advise them to do it every time possible. “There is always one thing which you should remember,” concluded Mr Tennent, “and that is that lime by itself is not a complete manure. Other manures have to be used to get the best results and you must not lose sight of this. Liming go hand in hand with phosphatic manuring.” This concluded the lime lecture and the party then proceeded to inspect the various plots on the farm. After the farm had been inspected Mr F. Linscott moved a hearty vote of thanks to Mr Tennent for his valuable and instructive address.