Soil conditions and plant growth

Abstract

HISTORICAL AND INTRODUCTORY 19 estimated, and before he had finished, the essential facts of plant nutrition were settled and the lines were laid down along which scientific manuring was to be developed. The water cultures of Knop and other plant physiologists showed conclusively that potassium, magnesium, calcium, iron, phosphorus, along with sulphur, carbon, nitrogen, hydrogen, and oxygen are all necessary for plant life. The list differs from Liebig's only in the addition of iron and the withdrawal of silica; but even silica, although not strictly essential, is advantageous to cereals.In two directions, however, the controversies went on for many years. Farmers were slow to believe that "chemical manures" could ever do more than stimulate the crop, and declared they must ultimately exhaust the ground. The Rothamsted plots falsified this prediction ; manured year after year with the same substances and sown always with the same crops, they even now, after sixty years of chemical manuring, continue to produce good crops, although secondary effects have sometimes set in. In France the great missionary was Georges Ville, whose lectures were given at the experimental farm at Vincennes during 1867 and 1874-5 (288).He went even further than Lawes and Gilbert, and maintained that artificial manures were not only more remunerative than dung, but were the only way of keeping up fertility. In recommending mixtures of salts for manure he was not guyded by ash analysis but by field trials. For each crop one of the four constituents, nitrogen compounds, phosphates, lime, and potassium compounds (he did not consider it necessary to add any others to his manures) was found by trial to be more wanted than the others and was therefore called the " dominant " constituent. Thus for wheat he obtained the following results, and therefore concluded that on his soil wheat required a good supply of nitrogen, less phosphate, and

Rapid N^2 Fixation in Pines, Alder, and Locust: Evidence From the Sandbox Ecosystems Study

“…Rates of N 2 fixation are thought to range up to as much as 325 kg·ha-Lyr-1 in alders (Cromack eta!. 1979) and up to 500 kg· ha-1 ·yr· 1 in cultivated legume crops (Russell 1973). Rates for black alder in this study (266 kg·ha-1 ·yr-1 ) are higher than most values in the literature.…”

“…A wide range of scientific approaches has helped to shape a consensus view on the importance of symbiotic ' Manuscript received 28 June 1991;revised 6 April 1992;accepted 7 April 1992. N2 fixation at the ecosystem level. The process of biological N2 fixation was discovered only after the studies of N mass-balance in field plots by Boussingault in the 19th century (Russell 1973). These were the first experiments to demonstrate large unexplained N accumulations with leguminous crops.…”

A Review of the Effects of Pesticides on Microbial Activity in Soils

“…LARGE quantities of pesticides reach the soil either by direct application or as run-off from treated crop plants (Goring, 1972). Once in the soil they may influence the growth and activity of the organisms which are largely responsible for the maintenance of soil fertility (Russell, 1973). The majority of biochemical transformations in soil result from microbial activity.…”

Distribution of Carbon Dioxide in the Aqueous Phase of Aerobic Soils

“…CARBON dioxide has long been regarded as having a considerable influence on chemical reactions within soil and thus on the availability of nutrients to plant roots (Alexander, 1961 ;Russell, 1961). Large uanto the atmosphere above the soil.…”

“…As there was little evidence with which to check these notions it seemed worth while to study the distribution of carbon dioxide and oxygen in the aqueous phase of aerobic soils. Furthermore as it is usually assumed that e is much greater at the surfaces of roots than in the bulk of soil (Russell, 1961 ;Alexander, 1961) it seemedthat thechanges in e around the roots should also be studied.…”