A meta-analysis of arable soil phosphorus pools response to manure application as influenced by manure types, soil properties, and climate.

Manure amendments to agricultural soils is an excellent opportunity for sustainable utilization of agricultural waste while providing multiple benefits to improve soil quality and increase the availability of nutrients to plants, including phosphorus (P). In this study, a meta-analysis of published data from 411 independent observations based on 133 peer-reviewed papers was performed for an in depth understanding of various factors affecting the transformation of soil P pools with manure application. Manure application increased all soil inorganic P (Pi) by 58.0%-282% and organic P (Po) by 65.0%-105%, while decreasing Po/total P (TP), compared to those in unamended soils. Manure types, soil TP, and manure application rates were the important factors that influenced soil P fractions. Elevation of soil labile Pi was more pronounced with compost application, while poultry and pig manure were more beneficial for promoting soil Pi fractions and stable Po contents compared with other manure types. The manure application rate had pronounced effect on increasing the stable Po fractions. The effects of manure application on increasing soil P fractions were greater in soils with lower TP contents as compared to that in high TP soils. Manure effects on enhancing soil labile Pi and moderately labile Pi were greater in acidic soil than that in neutral and alkaline soils. In addition, soil P fractions showed significant correlation with latitude and mean annual precipitation (MAP). By integrating the impacts of manure types, soil properties, and climate, this meta-analysis would help to develop the management of manure application in a specific region of agriculture as well as promote the interpretation of the interfering factors on the soil P fractions changes in the manure-amended soils.

Co-transport of graphene oxide and titanium dioxide nanoparticles in saturated quartz sand: Influences of solution pH and metal ions.

Increasing production and application of nanomaterials lead to their environmental release possible. The nanomaterials with different properties may transport together in porous media, and consequently affect their environmental fates. In this study, column experiments were conducted to investigate the co-transport of two typical nanomaterials, graphene oxide (GO) and nano-titanium dioxide (nTiO2), in saturated quartz sand in NaCl and CaCl2 electrolyte solutions under both favorable and unfavorable conditions. The breakthrough curves as well as the retained profiles of single and binary nanoparticles were examined. The results indicated that nTiO2 significantly enhanced the GO retention under all examined conditions, especially at lower pH, higher ionic strength and the presence of divalent cation Ca2+. This might be attributed to the formation of less negatively charged and larger-sized GO-nTiO2 agglomerates as well as the increased retention sites on sand surface by preferentially deposited nTiO2. However, GO merely slightly enhanced the transport of nTiO2 in NaCl solutions, whereas had negligible effect on nTiO2 transport and retention in CaCl2 solutions. The highly hydrophilic and mobile GO served as a carrier and facilitated the transport of nTiO2 in NaCl solutions. In CaCl2 solutions, the strong attachment affinity between positively charged nTiO2 and negatively charged quartz sand (at pH 4.5), and dramatical accumulation of large nTiO2 agglomerates near the column inlets (at pH 6.5) led to significant deposition of nTiO2 on quartz sand. The co-presence of GO failed to counteract the retention of nTiO2 particles on sand.