Shah Rukh

Relationship of Phosphorus Uptake with Its Fractions in Different Soil Parent Materials

The objectives were to determine inorganic P fractions in selected parent material soils and to develop a relationship of various P fractions with P uptake by Zea mays . Experimental study was conducted at Soil Chemistry Laboratory, Department of Soil Science and Soil and Water Conservation, Pir Mehr Ali Shah Arid Agriculture University, Rawalpindi, Pakistan, during February, 2013 to January, 2014. Triplicate soils were selected at three different level of development in each of loess, alluvium, shale residuum, and sandstone residuum, and surface and subsurface samples were taken. Samples were analyzed for pH, soil test P, total P, CaCO 3, dissolved and total organic carbon, dithionite extractable and amorphous iron. Soil P was fractioned into Ca 2-P, Ca 8-P, P adsorbed by Fe and Al, P occluded in iron oxides bodies, and apatite-P. Apatite-P was 33-71 %, and secondary phosphates i.e. occluded P, iron oxides surface adsorbed P and aluminum oxides surfaces adsorbed P ranged between 0.80 – 4.0 %, 2.65 – 14 % and 1.20 – 5.0 % of total P, respectively. Phosphorus uptake also differed significantly with soil parent material. The bioavailability of soil P fractions follow the order Ca 2-P > Org-P > Al-P > Fe-P > Ca 8-P > Occluded P > apatite-P. Dicalcium phosphates, iron adsorbed P, aluminum oxides adsorbed P and organic P control P bioavailability in Zea mays . Olsen P and occluded P gave better prediction for P uptake rather than Olsen P alone. This study will help to improve P fertilizer management and ultimately result in increase crop production. Original Research Article

Apatite Loss in Pothwar Loess Plain （Pakistan） Fits a Simple Linear Reservoir Model

Abstract Apatite is the dominant phosphorus (P) mineral in early stages of soil development, and its redistribution as labile forms under pedogenesis controls terrestrial bioavailability. Quantitative distribution of labile forms of P and apatite-P was examined in Pothwar Loess Plain, Pakistan where the degree of pedogenesis varied with relief. Four soil types, Typic Ustorthents (Rajar), Typic Calciustepts (Missa), Udic Calciustepts (Basal), and Udic Haplustalfs (Guliana), were sampled from three replicated locations at genetic horizon level. With the exception of total P value at surface, the mean total and apatite-P decreased towards the surface in Udic Haplustalfs and Udic Calciustepts where dicalcium and octacalcium phosphate increased toward surface. Iron (oxides and oxyhydroxides) adsorbed and occluded P forms were also in greater quantities in Udic Haplustalfs and increased toward the surface, whereas they were lowest and uniform in the Typic Ustorthents. Aluminum- and organic P correlated with soil organic matter. Apatite-P decreased exponentially with an increase in the sum of iron adsorbed and occluded P fractions, and fitted the equation M ( x ) = M 0 [1 – exp(– wx )] with r 2 = 0.996, where M ( x ) is the mean apatite-P concentration in solum, M 0 is the apatite-P content in the loess sediments, x is the cumulative iron adsorbed and occluded P, and w is an empirical factor indicating the change rate of apatite-P in the loess. From the calculated apatite-P of 740 mg kg −1 at the time of deposition, mean apatite-P loss was 60% in Udic Haplustalfs, 33% in Udic Calciustepts, 23% in Typic Calciustepts, and 8% in Typic Ustorthents. The transformation of soil P to labile forms was faster and deeper in level or slight depressions followed by gently sloping areas in wide plains, and was the least in the gullied land.

Iron Oxides Minerals in Soils Derived from Different Parent Materials

The knowledge on soil iron oxides morphology and crystallization is important for the management of nutrients especially phosphorus. The objectives of the study were to determine the iron oxides minerals in Pothwar uplands. In the study one soil from each parent material (loess, alluvium, sandstone and shale) was selected. Selected clay samples suspensions were observed under transmission electron microscope. Ferrihydrite was common iron oxide mineral observed in all selected parent material soils at different level of crystallinity. Ferrihydrite was observed in scattered granules and also as aggregates or clusters. Crystalline iron oxides hematite and lepidocrocite was observed only in shale derived Murree soil. Mica and Rutile were the inorganic crystalline material on which masses of ferrihydrite was scattered. Energy dispersive spectra of scattered ferrihydrite masses show it has more phosphorus than lepidocrocite and hematite. The study concludes that ferrihydrite was the major iron oxides mineral in all selected parent material soils while shale derived soil also had lithogenic hematite and lepidocrocite. Short Research Article Mehmood et al.; IJPSS, 5(2): 110-116, 2015; Article no.IJPSS.2015.065 111

Changes in soil phosphorus fractions across a toposequence in the estuary plains of Pakistan

ABSTRACT Understanding the regional dynamics of soil phosphorus (P) chemistry is essential for developing the best fertilizer management practices aimed at enhancing P use efficiency in cropping systems. The soil content of apatite, an important P-containing lithogenic mineral, can be influenced by its position in the local relief of a landscape. The objective of this study was to determine quantitative distribution of various P-forms in estuary plains of southern Pakistan in relation to soil genesis. Soils at different positions within the estuary plain were sampled at various genetic horizons. Apatite-P was the most abundant inorganic P constituent (380-590 mg kg−1) in all cases, followed in decreasing abundance by iron oxides surfaces adsorbed phosphorus (Fe-P), octacalcium phosphates (Ca8-P), aluminum oxides with surface bound P (Al-P) and the least abundant was the phosphorus occluded in iron oxides mineral (Occl-P). The abundance of apatite-P and these other forms of secondary phosphate varied for the soils at different relief positions in these estuary plain landscapes.