Search

Adding biochar to paper mill biosolids (PB) amendments may affect PB mineralization rate and nitrogen (N) availability. The objective of this 224-day incubation study was to evaluate the effect of amending two PB types varying in carbon (C)/N ratio (PB1, C/N = 24; and PB2, C/N = 13) with three rates (0%, 2%, and 5%) of pine (Pinus strobus L.) biochar produced at 700 °C on the dynamics of total C, total N, mineral N, N mineralization rate, and microbial biomass C (MBC) and N (MBN) in two agricultural soils (Kamouraska clay and St-Antoine sandy-loam). Two reference treatments were also included, namely, mineral fertilization and unamended soil. Total soil C concentration remained stable over the incubation period, whereas a decrease in total soil N was observed in both soils. In comparison with the unamended soil, the application of PB significantly increased total N, NH 4 -N, NO 3 -N, net mineralized N, applied N mineralization rate, and MBC in both soils. In comparison with the application of PB alone, biochar addition increased total C and MBC but decreased NH 4 -N, NO 3 -N, net N mineralization, and applied N mineralization rate in both soils. The co-application of biochar and PB1 resulted in the sequestration of mineral N released, which was more pronounced in the Kamouraska clay soil. The co-application of biochar and PB2 resulted in moderate release of mineral N. This study showed that the co-application of biochar and PB can benefit agricultural soils by improving NO 3 -N retention in agroecosystems while increasing organic matter and promoting microbial biomass. [ABSTRACT FROM AUTHOR]

• Long-term rotations with/without nitrogen (N) and phosphorus (P) fertilization. • Multiple techniques: P-NMR, P K-edge XANES, P fractionation, phosphatase assays. • Soil pH and organic carbon were significant predictors of soil P forms. • Long-term fertilization altered P forms by changing soil chemistry. • Rotation phase altered total and organic P concentrations regardless of fertilization. Efficient phosphorus (P) management is important for crop production and environmental sustainability of cropping systems. The effects of the agricultural management practices of crop rotation and fertilization on soil P forms and cycling were investigated in plots in Swift Current, SK, Canada, under three crop rotation phases [fallow (F), wheat after fallow (WF), and wheat after wheat (WW)], with four nitrogen (N) and/or P fertilizer treatments (+N+P, -N+P, +N-P, and -N-P), using techniques including sequential fractionation, 31P nuclear magnetic resonance (P-NMR), and P K-edge X-ray absorption near-edge (P-XANES). Soil total P (TP) and organic P (P o) concentrations were significantly reduced in F and WW phases compared to WF regardless of fertilization practice. Compared to WW, WF had the highest grain yield and nutrient uptake. Fertilization with N and P significantly influenced soil total carbon (C), total N, TP, and Mehlich 3-P concentrations and acid phosphatase activities, as well as the concentration of some P pools by sequential fractionation and stable P determined by P-XANES. Stopping P fertilization significantly increased the proportions, but not concentrations, of soil P o determined by P-NMR compared to plots still receiving P fertilizers, while the concentration of total diesters increased in plots fertilized with N. Redundancy analysis showed that soil pH and organic C were the significant predictors of P forms in these soils, suggesting that long-term N and P fertilization altered soil P forms by changing soil chemical properties. [ABSTRACT FROM AUTHOR]