Effect of the use of lime and other soil amendments on amorphous and differentially crystallized subsoil of the Akaka series

Abstract

While calcium has long been known as an essential macro-nutrient for plants, it has had the distinction of having been used as a soil ameliorating agent from the very beginning of organized soil husbandry (Thompson, 1957). Calcium is ascribed several roles in plant nutrition, among which is its role in the formation of cell wall constituents, that of nitrogen metabolism and as activator of several enzyme systems. (Meyer et al., 1960). Even so, Fried and Peech (1946) discussing calcium as a nutrient, carne to the conclusion that supplying calcium as such was not important, on the probable assumption that most well-cultivated agricultural soils have a sufficient supply of calcium for nutritional purposes. Thus, it is no surprise that most of the work done with calcium has been on its role as a soil ameliorating agent, or as a liming material on acid soils, for promoting the growth of certain crops. Under the general term of lime, many materials, such as calcium carbonate, hydrated lime, dolomitic limestone, silicic slags of various descriptions, crushed serpentine rocks, cement kiln dusts, etc., have been included. Numerous reasons have been adduced by several workers for the ameliorating effect of these soil amendments in relation to the growth of specific plants on these acid soils. Among these, some of the more important are: a) Promotion of more favorable soil physical conditions (Coleman et ~, 1958). b) Improvement in the fixation of nitrogen by improved soil microbial activity (Black, 1957). c) Beneficial effect of phosphorus release from the breakdown of organic phosphates (Ghani & Aleem, 1942). d) Reduction of phosphorus fixation in soils (Mitscherlich, 1947). e) Reduction of toxic levels of manganese and aluminum in soils (Mulder & Gerretsen, 1952). f) Increasing the general effectiveness of other elements (Truog, 1953). The literature also gives ample evidence of injury to crops due to overliming (Richardson, 1951; Russel, 1961). In tropical soils, while a great deal of research has been concentrated on the amelioration and utilization of leached-out acid soils, nevertheless many gaps as in a "jigsaw puzzle" yet remain to be filled. 111is situation is best illustrated in the words of Schmehl et al., (1950) " . . . the poor plant growth associated with acid soils is a complex function of many contributing factors, all of which may be modified by liming. Not until the relative importance of the different beneficial effects of liming acid soils is fully evaluated will it be possible to make the most intelligent use of lime . . ." As for the research findings reported in this thesis, it must be pointed out that much work has already been done on the amelioration with lime of these Akaka soils (Monteith, 1961; King, 1961; Rixon, 1962; Clements, 1962, 1963; Reddy, 1964; Rana, 1964). The present work is thus an extension of the work already done, in which Akaka subsoil (2-5 feet depth) has been investigated. The main areas where the work to be reported here would contribute to additional. knowledge are: a) The laboratory study of the progressive dehydration of these soils from the state of field moistness to complete dryness, with respect to certain chemical, physical, as well as mineralogical changes. b) Use of these soils at three different moisture levels (moist, 50% moist, dry)1 for studying their response to liming. This is the first time that an intermediate moisture level has been investigated in fertility studies in these soils. c) An investigation concerning the physical mixing of the moist and dry soils in varying proportions with respect to response to lime and plant growth. d) The use of crushed Olivine Sand as a soil amendment, since this material is found occurring in abundance in the Hawaiian islands. It would prove to be an economic soil amendment if found efficacious. In addition to crushed Olivine sand, crushed coral rock and calcium silicate (TVA) was also investigated.