| In North-American, intensive livestock operations and N-base manure application have caused dramatic increases in phosphorus (P) content of surface soil, leading to high risk of potential P loss in environment. To mitigate potential P risk, P-based manure application has been proposed according to the content of total P assuming that P in various forms of manure behaves similarly. This study was conducted to evaluate whether various forms of swine manure are different in the effects on agronomic performance, cumulative contributions of soil test P (STP), the relative availability and the fate of P applied. Three forms of swine manure, liquid, solid, and composted, were applied every 2 year in corn phase at 100 kg P ha-1 in comparison with chemical fertilizer under corn-soybean rotation during 2004-2012 on a Brookston clay loam soil.Swine manure performed differently in crop production depending on manure forms, crop species, and climate effect. The grain yield for corn was in the order of LM> SM?MC, while it for soybean was no difference in tested 3 forms of manure. Similar pattern were obtained for total P and grain P uptake. As a consequence, manure P agronomic coefficients were 1.14,0.85 and 0.74 for corn and 1.00,1.02, and 0.93 for soybean, for LM, SM, and MC, respectively. In this study, the PFPp and CPAE were used to reflect and differentiate the P efficiency in various P sources for the repeated P addition. Our result indicated that similar efficiency was observed on both PFPp and CPAE in tested manure forms for specific cropping year, but multiple over-manure application decreased the P efficiency in the long time effect.After eight year corn-soybean rotation production, post-harvest soil Olsen P content steeply increased in 0-30 cm soil profile, below of which, STP remained unchanged. The extent of STP increase was determined by manure form and soil depth. Furthermore, the increase of soil Olsen P was linearly correlated with cumulative P addition at both 0-15 and 15-30 cm soil depth. In 0-15 cm soil profile, insignificant differences were observed in increasing slopes of STP between the manure forms and CF, but at 15-30 cm depth, MC significantly increased the slope of STP relative to LM and SM, respectively. Consequently, to increase by 1.0 mg P kg-1 soil Olsen P, the amount of 14.0,25.6 and 15.0 kg ha-1 total P was required for LM, SM, and MC, respectively in 0-30 cm depth. After crop P removal was subtracted from the total P applied, the amount of manure P required to increase each unit of STP was 9.8,16.1 and 10.7 kg net P ha-1 in 0-30 cm soil profile. To differentiate relative availability from applied P sources, the PSC (STP mass+crop P uptake) manure/(STP mass+ crop P uptake) chemical fertilizer p was proposed and calculated as a weighting factor relative to chemical P after considering the cumulative P uptake during crop growth. Across eight-year corn-soybean rotation production, the values of PSC were 1.11,1.07 and 0.96 in the 0-15cm soil depth for LM, SM, and MC, respectively, while it was 1.10,1.07, and 1.02 for corresponding manure forms in 0-30 cm soil profile.The relative availability and the fate of P were determined on specific manure forms and soil fractions. Similar effect was observed between LM and CF on all tested P fractions, whereas SM increased the fractions of soil most labile Pi (H2O-Pi) and moderately labile Pi (NaOH-Pi) relative to CF. For MC, no differences were observed on the forms of soil LPi (NaHCO3-Pi) and most labile Pi, as well as moderately stable P (HCl-Pi), compared with CK treatment. Therefore, the PAC (P availability coefficients, a ratio of soil NaHCO3-Pi derived from swine manure P to that of fertilizer P), were 1.11,1.14, and 0.59, respectively for LM, SM and MC at the end of 9 year corn-soybean rotation. When taking crop P removal and the increases of soil H2O-Pi into account, then it would be 1.11,1.19, and 0.75, respectively for LM, SM and MC in corn-soybean system.Overall, our result indicated that P-based application must be optimized on a manure form-specific base and take the long-term legacy P and P migration or trasformation in soil profile into consideration in guiding manure strategy.Phytoremediation of the mining-disturbed land has been a challenge due mostly to the low bioavailability of soil indigenous P, low water retention capacity and the low fertilizer P use efficiency, which may be improved through inoculation of arbuscular mycorrhizal fungi (AMF). A greenhouse experiment was conducted to evaluate the effects of AMF(Glomus mosseae) and fertilizer P addition on leaf photosynthesis and growth of maize in a mining-disturbed loess soil and to quantify the relationships among these effects. Compared with non-AMF (NAMF), AMF inoculation increased P concentrations of shoot and root respectively by 16.7 and 72.9%, net photosynthetic rate (Pn) by 12.2%, leaf area by 21.9%, stem diameter by 23.6%, shoot dry mass by 31.7%and P use efficiency by 44.3%. Regardless of AMF inoculation, P contents of root and shoot, leaf area, stem diameter, and plant height increased linearly with the increases of P rate, while root colonization, Pn, and shoot biomass responded to P rate added in a quadratic pattern, with their maximums obtained at the P rates between 73 and 141 mg kg"1. Measurements of photosynthesis-related parameters including stomatal conductance, transpiration rate, and intercellular CO2 concentration decreased with the increases of P rate, but the extents of decline were reduced with AMF relative to NAMF. Water use efficiency increased linearly with increases of P rate at a smaller rate with AMF than with NAMF. Inoculation of AMF promoted maize growth and reduced the dependency of crop on addition of fertilizer P, which can be practically significance for the phytoremediation program of rehabilitation of mining-disturbed soils. |
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