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THE PHOSPHATE STATUS OF IRISH SOILS WITH PARTICULAR REFERENCE TO FARMING SYSTEMS
Author(s) -
McDONNELL PATRICK M.,
WALSH THOMAS
Publication year - 1957
Publication title -
journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 0022-4588
DOI - 10.1111/j.1365-2389.1957.tb01871.x
Subject(s) - phosphorus , fractionation , soil water , pasture , chemistry , phosphate , environmental chemistry , agronomy , environmental science , soil science , biology , organic chemistry
Summary The phosphorus status of selected permanent pasture and tillage soils has been examined by a fractionation technique. This has shown a distinct difference between the soils especially with regard to the organic‐phosphorus fraction. Some of the reasons for these differences are discussed. The readily available phosphorus level of a highly productive, permanent pasture soil which has received no phosphatic fertilizer for years was found to be good, indicating a satisfactory mineralization of organic phosphorus which was the only form in which this nutrient was added. Irrespective of whether phosphorus was added in the organic or inorganic form there was an appreciable accumulation in the surface 3 in. of permanent pasture, indicating stabilization of applied phosphorus in that zone. Adsorbed phosphorus constituted a relatively small proportion of the inorganic phosphorus, the latter faction varying but slightly in the different soils. A comparison between Morgan's solution (sodium acetate‐acetic acid) and other extractants showed that this solution provides a good index of phosphorus availability, when the P value of the extract is regarded as an intensity value. When phosphorus fractionation studies were carried out on four soils in hydrologic sequence and occurring in close proximity in an area unmanured for about a century, distinct differences in phosphorus categories were found. These differences were especially striking between the impeded and free‐draining members. They were further explored through the medium of fractionation studies on different textural fractions. The main difference was found in the organic‐phosphorus level and was associated with the fine‐clay fraction. The general significance of the results in relation to farming systems, the phosphorus cycle and methods designed to determine the phosphorus status of soils, is discussed.