Abstract:
Since man is so dependent upon plants, he has searched for more accurate methods of increasing yields by various chemical methods for approximately 300 years, or since the famous experiment of the willow tree conducted by von Helmont in which he concluded that water was the only factor of plant growth. One hundred and fifty years later Jethro Tull declared earth to be the substance of plants; but, it was not until Justus von Liebig published a series of lectures in 1849 that the problem of plant nutrition began to come into focus. Useful interpretations of plant nutrition have progressed from that time by the aid af such men as Laws and Gilbert of Rothamsted, Winogradsky and Beijerinek with their work on nitrogen fixation and Dyer who supplied infomation on availability of nutrient elements in the soil. Later in the United States two men decided to break away from the European methods and attack the problem on what they believed to be a more fundamental basis. C. G. Hopkins worked on the theory of total content af nutrient elements in the soil and plants, while Milton Whitney thought that the productive capacities of soil were to be found in the natural soil solution. It is meaningless to say wherein these men were right or wrong because both contributed much to scientific agriculture and both contributed greatly toward stimulating workers in experiment stations all over the country to attack the plant nutrition problem.
Keywords:
soils, plant science, plant tissue, foliar, plant needs
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