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Fluid Journal : Winter 2017
16 The Fluid Journal Winter 2017 ACT NOW! Write, call or e-mail the Fluid Fertilizer Foundation Phone: 785-776-0273 •E-mail: firstname.lastname@example.org Research and education for efficient use of fluids. The Fluid Fertilizer Foundation We need you to join hundreds of other growers, dealers, fertilizer manufacturers and other supporting industries JOIN IN THE SUPPORT OF THIS ORGANIZATION THAT DIRECTLY BENEFITS YOUR BUSINESS! control soil. All treatments possessed between 67 and 72% calcium phosphate minerals. The best fit lines for APP and the 80/20 treatment revealed more Al adsorbed P, while the MAP and control P appear more closely associated with clay and Fe. Currently, no concrete evidence exists to explain this dichotomy, but given that significantly less MAP diffused into the second ring relative to the APP and 80/20 treatments, a PP presence effect is arguable. Additionally, the P in the APP treatments may be involved in weaker, outer-sphere associations and the MAP samples could have chemisorbed to Fe minerals via inner-sphere interactions that are significantly stronger, making P less labile. Summing up Small changes in P fertilization practices could save farmers money and reduce total P input requirements. Based on the results of this study, including small amounts of PPs when applying fluid MAP to calcareous soils, could potentially allow growers to apply less total phosphorus to agricultural systems without compromising plant performance. At this time, caution should be taken not to extrapolate the proposed mechanisms too far until future studies, at variable P rates in a wider array of calcareous soils, establish more incontrovertible evidence. The lack of biological activity in this study may overestimate the amount of time PPs remain in soil. While temperature, moisture, pH, and many other abiotic factors influence PP hydrolysis rate, the presence of plants and the myriad of microbiota associated with the rhizosphere will also expedite the process for two reasons: 1) the concentration of PP will likely be greater thus increasing the total rate of conversion of PP to OP, and 2) plant root/microbial/mycorrhizal removal of OP from solution will drive greater dissolution rates to maintain solution OP activity. Although not assessed, microbial activity is surely taking place in the described incubation study albeit not to the extent that one would expect in an active root zone (Adesemoye and Kloepper 2009). Even if PP does not persist more than four weeks, as was the case in this study, the potential benefit of using calcium polyphosphate precipitates as intermediates, to briefly maintain higher OP fluid activity early in the growing season, cannot be dismissed. Not only would this scenario possibly help mitigate P deficiency risks in cold soils of the early season, but the system allows for greater P diffusion from the POA creating conditions more conducive to nutrient sorption (more plant available) than precipitation (virtually plant unavailable). Enhanced nutrient movement also creates a greater fertilizer “footprint,” increasing the likelihood that crop roots encounter and exploit the P enriched zone. In many ways, the 80/20 MAP/ APP treatment combined the best attributes of MAP application (high OP, plant available P) and APP (prolonged temporal lability and greater diffusion) to create an ideal scenario to provide P nutrition. While more work is necessary, our group believes the blending approach possesses tremendous potential to reduce total P inputs to calcareous soils in the future, simultaneously saving grower capital, conserving a non-renewable resource, and protecting freshwater ecosystems. J. Weeks is a PhD student studying soil and environmental chemistry at Kansas State University, and Dr. Hettiarachchi is a Professor of Soil and Environmental Chemistry in the Department of Agronomy, Kansas State University, Manhattan, KS.