| [Object] Soil P fixation is a big problem which limited P fertilizer utility efficiency. Recent research shown fluid fertilizers have obvious effects on improve crop P nutritional status and soil P bioavailability as well, especially on calcareous soil. In present study, stimulating incubation experiment and pot experiment were carried out to compare the differences of soil P availability, mobility, liability as well as maize P nutrition between granular and fluid form of P fertilizers in sandy soil, loam soil and clay soil. The objectives are to improve our understanding on the mechanism of different forms of soil P transformation, provide a new approach to evaluate phosphate fertilizers bioavailability, which are fundamental knowledge on P fertilizer efficient utility and soil P resources management on calcareous soil under fertigation condition in arid region, Xinjiang.[Method:] 1. Employed Petri dish to investigate the differences between granular and fluid form of phosphate fertilizers placed in 3 calcareous soils.2. Using continuous irrigation and intermittent irrigation in greenhouse to compare the availability of granular and fluid P fertilizers, and open out the mechanism of soil P activation by fertilizer.3. Employed DGT(diffusive gradients in thin films) to simulate root P uptake from soil.4. Compare the inorganic phosphorus fraction sequentially extracted method between method Jiang-Gu and method Guppy, in order to find out the rule of inorganic phosphorus transforming, and combine with plant uptake to estimate calcareous soil's P provided ability.[Results] 1. Soil Olsen-P content decreased significantly with increasing the distance from the P fertilizer application point to the edge of Petri dish (0-43mm). Furthermore, it is observed Olsen-P always much higher under the treatment of fluid fertilizer than granular fertilizer, except P fertilizer placement point.2. In contrast with granule fertilizer, soil P mobility increased greatly with fluid fertilizer application, i.e., almost 55-70% of the applied P still distributed in 0-7.5 mm section soil with granule P fertilizer treatment, whereas, that is 15-40% under fluid P supply, and 60-85% of applied P diffused more far within the distance of 7.5-43 mm.Three fertilizer concentration showed the same variety in three soil types.3. Changes in pH caused by fertilizers were small and limited to the soil section where the fertilizer was applied. Soil pH was significantly low in the 0-13.5 mm section across all soil types (p<0.05).4. By means of DGT method, we found total P absorbed by oxidized Fe gel were 6.84-8.26μg of fluid P and 5.42-6.68μg of granular form of P supply respectively, suggesting P bioavailability increased substantially (p<0.05) under fluid P application. 5. From soil inorganic P fraction sequential extraction approaches (Guppy and Jiang-Gu), we found the proportion of available forms of resin-P and Ca2-P increased by 19.5% and 17.2% with fluid P fertilizer treatment.6. Maize dry matter weight and P uptake of are 79. 1g plant-1 and 0.42g plant-1, compared with the treatment of granule P application, which increased by 27.4% and 35.5% respectively, indicating maize growth and P nutrition greatly improved through fluid P fertilizer application.7. Higher P fertilizer recovery rate (25-29%) obtained with the fluid form P supply than that (11-18%) with granular P supply. Moreover, although a bit higher P recovery rate observed with continuous irrigation, but the two irrigation model (intermittent or continuous irrigation) has no statistical difference on plant P utility.8. When in continuous irrigation, resin-P,Ca2-P's correlation coefficient with phosphorus uptake by corn leaf were 0.9365 and 0.9218; the correlation coefficient with phosphorus uptake by corn stalk were 0.9277 and 0.8950.[Conclusion]1. Fluid fertilizer can provide a greater diffusion, availability and lower fixation by soil compared with granular fertilizers in calcareous soil.2. The dry mass of corn were higher in fluid P fertilizer treatments than that in granular fertilizer treatments. The dry mass of corn were higher with continuous irrigation than with intermittent irrigation.3. The bioavailability of fluid P fertilizers were higher than granular fertilizers. Whether it is in continuous irrigation or continuous irrigation, the phase availability of fluid P fertilizers were significantly higher than granular fertilizers, but it was not significantly between the treatment of granular fertilizer applied in one time and granular fertilizer applied in four times.4. Compared with granular fertilizers, Fluid P fertilizers increase the proportion of available inorganic phosphorus fraction and restrain the proportion of unavailable inorganic phosphorus fraction.5. The correlation between resin-P in method Guppy and phosphorus uptake by corn was more significantly when compared with Ca2-P in method Jiang-Gu. |
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