Tuesday, 11 July 2006

Isotopic and Spectroscopic Investigations toward Understanding Differential Behavior of Fluid and Granular Micronutrient Fertilizers in Soils.

Ganga Hettiarachchi, Univ of Adelaide, School of Earth and Environmental Sciences, Glen Osmond, 5064, Australia, Enzo Lombi, Land and Water, CSIRO, PMB 2 Glen Osmond, SA 5064, Adelaide, 5064, Australia, Michael McLaughlin, CSIRO Land and Water, PMB 2, Glen Osmond, 5064, Australia, and David Chittleborough, Soil and Land Systems, School of Earth and Environmental Sciences, Univ of Adelaide, Adelaide, 5005, Australia.

Millions of hectares of arable land worldwide, particularly in arid and semi-arid regions, are deficient in plant available micronutrients. Thus, various organic and inorganic micronutrient fertilizers have been used to correct their deficiencies. Inclusion of micronutrient in commercial macronutrient fertilizers is a common practice throughout the world and has been driven mainly by product physical characteristics than by considerations of fertilizer efficiency. The cost of conventional micronutrient fertilizers as well as yield loss due to their inefficient utilization is considerable and therefore it is essential to find new application methods that increase the efficiency of micronutrient acquisition. Despite their economic importance, investigations on the chemistry of micronutrient fertilizers in soil have rarely been conducted. Research conducted by our group showed that in calcareous soils a significant increase in yield (8 to 48%) can be achieved using fluid fertilizers such as ammonium polyphosphate compared to equivalent granular fertilizer. Further, recent field studies have shown an increase response to fluid Zn (Zn concentration in grain) compared to granular fertilizers in calcareous sandy loam soils. We also showed increasing Zn response with increasing rates of fluid P/Zn while there was no Zn response with increasing granular P/Zn. These results are very significant in terms of increasing crop production in Australia and in other arid/semi-arid regions of the world. This study aimed to improve our understanding of the chemical and physical processes underlying the differential efficiency of added micronutrient Cu, Mn, Mo, and Zn in different forms to different soils. Results examining the diffusion of micronutrient from the point of fertilizer placement, the lability of micronutrients measured using isotopic dilution techniques, and fertilizer reaction products identified using various spectroscopic techniques will be presented.

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