Soil Chemical Property Changes over Time from Struvite Compared to Other Fertilizer-Phosphorus Sources in Multiple Soils

Studies have shown that phosphorus (P) recovered from wastewater as the mineral struvite [MgNH4PO4·6(H2O)] may be a viable alternative fertilizer-P source. This study aimed to compare the effectiveness of electrochemically precipitated struvite (ECST), reclaimed from synthetic wastewater, to other commercial fertilizer-P sources in cultivated soils from Arkansas [AR;silt loam (SiL) and loam (L)], Missouri (MO;SiL), and Nebraska [NE;SiL and sandy loam (SL)]. A plant-less, moist-soil incubation experiment, including ECST, chemically precipitated struvite (CPST), monoammonium phosphate (MAP), triple superphosphate (TSP), and an unamended control (UC), was conducted to quantify soil pH, nitrate (NO3-N), ammonium (NH4-N), and Mehlich-3 (M3)-P, -Ca, -Mg, and -Fe concentrations at 0.5, 1, 2, 4, and 6 months. All measured soil properties differed (P ·kg-1 for AR-L-TSP after 1 month and NE-SiL-MAP after 6 months, respectively. Soil M3-P ranged from -29.6 mg·kg-1 in the AR-L-UC after 1 month to 429 mg·kg-1 AR-SiL-TSP after 0.5 months. Results showed that, over time, ECST had comparable pH and soil NO3-N, NH4-N, and M3-P, -Ca, -Mg, and -Fe behavior compared to CPST, MAP, and TSP across various soil textures.

Effect of lignite amendment on carbon and nitrogen mineralization from raw and composted manure during incubation with soil

The application of animal manure as a source of plant nutrients requires the determination of the amount and pattern of nutrient mineralization from manure.A laboratory incubation study was conducted to investigate the influence of lignite amendment and lignite type on carbon(C)and nitrogen(N)mineralization in raw(feedstock)and composted cattle manure following application to soil at 30 and 60 t ha^(-1).The mineralization of C and N was determined by measuring changes in CO_(2) evolution and mineral N(NH_(4)^(+)-N+NO_(3)^(-)-N)over 40 d.The results showed that lignite amendment suppressed the amount of manure C mineralized in both feedstock and compost,with the effect being more pronounced in the compost.Over the 40-d incubation,the percentage of applied C mineralized was 26.4%-27.8%and 16.3%-21.4%in unamended and lignite-amended feedstocks,respectively.The corresponding C mineralized in the composts was 12.4%-14.1%and 3.5%-6.5%.Lignite had no significant effect on the net N mineralized in compost(4.8%-6.7%and2.5%-7.8%in unamended and lignite-amended composts,respectively).Lignite had either no effect or increased the net N mineralized in feedstock(from3.2%-8.7%without lignite to 10.4%-13.5%)depending on the type of lignite used.This study suggests that using lignite-amended manure,especially when composted,has the potential to build up soil organic C without limiting the availability of mineral N.

Effect of two biogas residues' application on copper and zinc fractionation and release in different soils

Biogas residue （BR） is widely used as a new green fertilizer in agriculture in China. However, it often contains a high concentration of heavy metals so its application should cause our concern. An incubation experiment was conducted to study the risk of pig biogas residue （PBR） and chicken biogas residue （CBR） application on Liuminying soil （LS） and Yixing soil （YS）. The soils were incubated for one, three and six months with 0, 2%, 4% and 6% addition of BRs. According to BCR extraction results, the PBR and CBR applications induced an increase in the concentration of exchangeable fraction of Zn. As for the concentration of exchangeable fraction of Cu, an increase was only observed in the treatments with PBR application. The heavy metal binding intensity also showed a similar trend. With the PBR application, for the LS and YS, the highest concentrations of exchangeable Zn increased 3.6 and 9.5 times, respectively, while the exchangeable Cu was increased by 52.6% and 187.1%. Dissolved organic carbon was the limiting factor for the exchangeable Cu while the exchangeable Zn was controlled by soil pH. PBR presented more agricultural risk than CBR when used as fertilizer. Meanwhile, BRs were more adaptable to LS than YS according to the heavy metal release results.

Time effects of rice straw and engineered bacteria on reduction of exogenous Cu mobility in three typical Chinese soils

Globally,copper(Cu)accumulation in soils is a major environmental concern.Agricultural organic waste and some bacterial species can readily absorb metals in an eco-friendly manner,and thus are commonly used in metal-contaminated soil remediation.This study investigates the change in Cu fractions during the aging process and the time effects of rice straw(RS)and engineered bacteria(EB)(Pseudomonas putida X4/pIME)on reduction of Cu mobility.Three typical Chinese soils(red,cinnamon,and black soils)were incubated with RS or RS+EB in the presence of exogenous Cu for 24 months.The soil physicochemical properties,reactive soil components,Cu fractions,and Cu mobility were determined over time.The Cu mobility factor(MF)values were the lowest in the black soil(6.4-9.2)because of its high organic carbon and clay contents.The additions of both RS and RS+EB accelerated Cu stabilization during the aging process in all three soils.The Cu MF values decreased with time during the initial 20 months;however,the MF values increased thereafter in all soils,which might be due to the reduction of humic substances and amorphous iron oxides and the increase in iron oxides complexed on the organic matter.The reduction rates of Cu MF were similar after 16,24,and more than 24 months in the red,cinnamon,and black soils,respectively,indicating that RS and RS+EB could limit Cu mobility at different times in various soils.The RS treatment showed the greatest efficiency in reducing Cu mobility in the red,cinnamon,and black soils after 12,12,and 8 months of incubation,respectively.The RS+EB treatment was more efficient than the RS treatment in the red soil during the initial 8 months of the incubation period.Our study provides theoretical support for Cu risk assessments and RS supplementation for Cu remediation in different soils.