Availability of phosphorus and utilization of phosphate fertilizers in some great soil groups of Hawaii

Abstract

The soil is a supplier of phosphorus; and. in addition, it governs phosphorus availability through complex reactions between itself and fertilizer phosphorus. Conservative phosphate fertilization of some soils has not always effectively provided phosphorus for crop plants. Low efficiency of phosphorus recovery has long been an important, practical agricultural problem and has led many workers to study the problem of phosphorus immobilization. It is this immobilization which is believed largely responsible for low phosphate fertilizer recovery by plants and for low crop yields. Low recovery of added phosphorus by agronomic crops is a serious problem inmost Hawaiian soils. Experiments conducted by Ayres (1934) and by Chu and Sherman (1952) have shown that phosphorus fixation occurs very rapidly or even almost immediately in many Hawaiian soils. Fixation of phosphorus and thus its availability, can be regulated to some extent by certain management practices of soils. Heavy phosphorus applications are sometimes advocated to saturate the phosphorus fixation complex in soils with excess of phosphorus for plant utilization (Younge, 1961; Younge and Moomaw: 1960). Sometimes also the correct choice of a chemical compound to supply phosphorus may improve fertilizer efficiency. When the factors responsible for phosphorus fixation are understood more completely. a greater measure of fertilizer efficiency will be attained. Direct application of phosphate fertilizer material to the plant could be one solution to the soil fixation problem if a number of difficulties are overcome. Among these are: physiological burning of leaves and stems, poor recovery of added phosphorus, and lack of uniform distribution of the added nutrient within the plant. Some of these difficulties may be overcome by using suitable fertilizer material, controlled pH, proper concentration, and efficient means of application. It is widely believed that the influence of lime on phosphorus availability depends on the solubility and mobility of aluminum. The use of soil amendments such as applications of lime to acid soils may be useful in reducing the solubility and mobility of aluminum. It is commonly believed that phosphorus availability to plants increases as soils are limed close to pH 7.0; but this generalization may not apply in the tropics. Greene (1954) has reported that results from liming in the tropics have usually been unsatisfactory, and he concluded that the question of liming tropical soils should be reconsidered. In this study on phosphorus; one of the hypotheses proposed for testing was: when lime is applied before phosphorus, phosphorus reacts with the precipitated aluminum and forms a surface complex which rapidly equilibrates with the soil solution. And further, when lime is applied after the application of phosphorus, the phosphorus interacts with the surface and becomes covered by the precipitated aluminum. The objectives of the various experiments performed and reported in this thesis are summarized as follows: 1. to determine the influence of two isotopes; P31 and P32 ,phosphorus compounds, rates, and methods of phosphorus application on the availability of native and applied phosphorus in diverse soil systems. 2. to determine the availability of soil phosphorus ("A" value of Fried and Dean; 1952) as influenced by sources and various times of lime and phosphorus application in several Hawaiian soils. 3. to determine the influence of liming and phosphate fertilization on the intensity of phosphorus fixation by soils with diverse mineral systems, such as amorphous hydrated oxides, goethitegibbsite; kaolin (1:1clays), and montmorillonite (2:1 clays), in various tropical soils.