The principles of crop production
Journal of the Chemical Society Transactions
IN any discussion of the principles of crop production it is necessary to begin with the year 1840. By that time i t was definitely knowrr that plank consist mainly of organic matter along with a little mineral matter-phosphorus, calcium, potassium, sodium, etc.-to which, however, very little importance was attached. The practical man knew that farmyard manure was the great fertiliser; he also knew that other substances, bones, salt, etc., had, in certain circumstances, considerable f
... derable f ertilising value. The most obvious facts were the large amounf, of organic matter in the plant and the large amount of organic matter in the best manures; and it is only natural that chemists and physiologists should have connected these, and argued that the object of the manure was to furnish organic matter for the plant. By a brilliant stroke Liebig, in 1840, brushed aside this obvious connexion and declared that the true function of the manure was to provide, not organic matter, but the mineral constituents which the chemists had ignored. The first step, he said, was t o find out what mineral constituents the plant contains, and then t o supply these substances in a suitable form. If any one of them is lacking the soil is rendered infertile, and matters will not be put right until that one is added. Thus the whole art of manuring was reduced t o an exact science. Liebig was a brilliant writer and secured many disciples. Farmers were told that they need only use a few pounds of simple salts to make their crops grow. It was the first time they had heard the fairy tales of science. We can only faintly realise the utter incredulity with which they received the idea that crops could be raised by small doses of chemicals sold in bags from a factory, in place of the cartloads of farmyard manure that had always been regarded as necessary and sufficient,. It was as if farmers had been told that they themselves could dispense with the beef, bread, and beer that Cobbett had said was their Divinely prescribed diet, and could live instead on tablets of chemicals. The comments of the local wits were pretty caustic; some of them are still preserved in the countryside, but they are hardly suitable for the polite audience that I have the honour of addressing to-night.