Development and Validation of a Phosphate Rock Decision Support System

Abstract

Although some mathematical models exist to assist in deciding whether or not to apply phosphate rock (PR) to soils as a source of P, these models focused either on the use of highly soluble PR sources, mainly for pastures, or were too impractical for field use. There was, therefore, a need to develop a Phosphate Rock Decision Support System (PRDSS) with more comprehensive capabilities to predict the relative agronomic effectiveness (RAE) of PR with respect to watersoluble phosphorus (WSP) fertilizers at field and farm level. The PRDSS includes PR sources varying widely in solubility and different crop species grown on variable soil properties and rainfall conditions. In this paper, we describe the development and use of the mathematical model, PRDSS, to estimate RAE of PR sources with respect to WSP fertilizers and to calculate a simple index to be used for preliminary economic comparison of these two types of P sources. The PRDSS is able to function with a minimum input of only soil pH, the name of the mine that is the source of the phosphate rock, and the species of crop to be grown. A more accurate prediction of RAE is obtained from the PRDSS when more detailed data describing the soil, crop, and weather are included as inputs.

Potential Utilization of Local Phosphate Rocks to Enhance Rice Production in Sub-Saharan Africa

“…To solve this difficulty, a Phosphate Rock Decision Support System (PRDSS) has been developed by the IFDC. The PRDSS is a mathematical model that was derived from datasets of various experiments conducted by collaborating scientists in a number of countries 20,41 . The PRDSS was designed to predict the RAE of PRs with respect to watersoluble P-fertilizers and calculate a simple index usable for preliminary economic comparisons of these 2 types of P sources 41 .…”

“…The PRDSS is a mathematical model that was derived from datasets of various experiments conducted by collaborating scientists in a number of countries 20,41 . The PRDSS was designed to predict the RAE of PRs with respect to watersoluble P-fertilizers and calculate a simple index usable for preliminary economic comparisons of these 2 types of P sources 41 . The PRDSS includes information on PR sources that vary widely in solubility and on different crop species that are grown in soils of variable properties, and under different rainfall conditions and crop management methods 16,41 .…”

“…The PRDSS was designed to predict the RAE of PRs with respect to watersoluble P-fertilizers and calculate a simple index usable for preliminary economic comparisons of these 2 types of P sources 41 . The PRDSS includes information on PR sources that vary widely in solubility and on different crop species that are grown in soils of variable properties, and under different rainfall conditions and crop management methods 16,41 . Therefore, the PRDSS can function with a minimum input of only soil pH, the name of the mine where the PR originated, and the crop species to be grown to estimate the RAE roughly.…”

“…The PRDSS uses soil pH, the soil P-fixation capacity, aluminum saturation, and so on as soil factors to calculate PR dissolution 41 . However, this calculation cannot take account of changes in P forms in the reduction-oxidation process.…”

An evaluation of three Thai phosphate rocks for agronomic use based upon their chemical and mineralogical properties

“…The Ca-P minerals (apatite) may be highly reactive and suitable for direct use on acid soils. However, Ca-Fe-Al-P minerals (crandallite) are not reactive and are a poor source of P for upland crops, but may be effective for flooded soils (Gilkes and Palmer 1979;Smalberger et al 2006;Francisco et al 2008). There are many types of phosphate minerals in PR in Thailand, such as apatite and crandallite in Ratchaburi-and Kanchanaburi-PR derived from guano occurring in limestone (Japakasetr 1982;Boonampol and Cholitkul 1995), and variscite in Roi-Et-PR derived from cementing matrix within sandstone (Sheldon 1984).…”