Effect of band geometry and chemistry on fertilizer phosphorus availability

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Hammond, Derwyn
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Growth chamber experiments were conducted from 1992 to 1994 on a calcareous silty clay loam soil (pH $\approx$ 7.9) low in levels of available phosphorus. A number of different band geometries were assessed for their effect on the efficiency of P utilization from applied monoammonium phosphate (MAP). Ammonium and magnesium sulfates, urea, and organic amendments (lignosulfonates) were also incorporated into P fertilizer bands to study their effect on uptake of applied P by plants. The MAP was labelled with the radioisotope $\sp{32}$P in order to determine utilization of fertilizer P specifically. Dry matter yields and total P uptake were also measured. Canola was very efficient at utilizing applied P, with no apparent benefit from increased area of application or dual banding with N. However, fertilizer P uptake by wheat increased slightly with area of application, Dual banding the P fertilizer with N or MgSO$\sb4$ stimulated P uptake by wheat. Ammonium sulfate was most effective in increasing P utilization.Urea initially slowed uptake, but increased P utilization at later stages of plant growth. Studies were also conducted using very wide band widths. Labelled MAP was randomly applied in powdered form to several points within the bands, to simulate granular applications. Ammonium sulphate was dual banded with the MAP granules (placed in direct contact) or randomly scattered within the band. Fertilizer P uptake declined slightly as band width increased from 2.5 to 15 cm, particularly at earlier growth stages. Dual banding with ammonium sulphate improved P fertilizer utilization and yield. (Abstract shortened by UMI.)