Contrasting Effects of Cattle Manure Applications and Root-Induced Changes on Heavy Metal Dynamics in the Rhizosphere of Soybean in an Acidic Haplic Fluvisol: A Chronological Pot Experiment

Abstract

To characterize the dynamic mobilization of heavy metals (HM) in a crop-soil system affected by cattle manure (CM) application, soybean [Glycine max L. Merr. cv. Toyoharuka] crops were exposed in a chronological pot experiment to three CM application rates and sampled at two vegetative stages and two reproductive stages. A sequential extraction procedure for metal fractionation, soil pH, microbial activity, and plant HM uptake was determined. In non-rhizopshere soil, with CM application a liming effect was detected, and increased microbial activity was detected at the reproductive stage. CM application shifted Cd from available state to oxide-bound pool in non-rhizosphere soil; however, shifts in Cd from an oxide-bound pool to the available state were observed in rhizosphere soil. CM application stabilized the available Zn and Pb to oxide-bound Zn and organic-bound Pb in both non-rhizosphere and rhizosphere soils, and the stabilizing degree increased with higher CM application rates. The promoted Zn immobilization in the rhizosphere was due to the liming effects induced by added CM that counteracted the root-induced acidification. On the basis of a stepwise multiple regression analysis, the shift of Cd and Pb fractionation was mainly related to microbial activity. Adding manure inhibited Zn and Pb uptake but promoted Cd uptake by soybean, and a greater influence was detected at the reproductive stage, at which CM application increased the root Cd-absorbing power but did not significantly affect the Zn- and Pb-absorbing powers. In an agricultural context, long-term CM application, even at the recommended rate of 10.13 Mg ha, may cause a soybean Zn deficiency and high Pb accumulation in Haplic Fluvisols, although CM is often considered as an environmentally friendly fertilizer.

Hydrothermal carbonization of microalgae for phosphorus recycling from wastewater to crop-soil systems as slow-release fertilizers

“…In order to satisfy the J o u r n a l P r e -p r o o f requirement of sampling at two different growth stages, two batches of experiments were conducted at the same time. Rhizosphere soil samples were collected by carefully cleansing the soil from the roots (Chu et al, 2017;Sha et al, 2020). The soil samples were divided into two parts: one portion was freshly prepared for the determination of enzyme activity and soil microbial C and P content, and another portion was air-dried for analysis by sequential P fractionation.…”

Cadmium Immobilization in the Rhizosphere and Plant Cellular Detoxification: Role of Plant-Growth-Promoting Rhizobacteria as a Sustainable Solution

“…Cadmium concentrations in the rhizosphere typically reach a toxic level by the influence of root exudates and microbial activities by altering the plant macronutrient (P, N, Ca, Mg, and S) and micronutrient (Fe, Zn, Al, and Mn) availability . As a result, this is the most crucial plant–soil microecology point where we need to focus on the Cd immobilization process, especially for phytoavailable Cd. − Lignite, compost, phosphate, biochar, zeolites, manure, lime, etc. are being used in soil for in situ Cd immobilization to minimize the uptake of Cd in plants .…”

The interaction of soil aggregate stability with other soil properties as influenced by manure and nitrogen fertilization

“…The higher soil acidity levels found in FYM treatments compared with N fertilization-only treatments could be due to the CaCO 3 in FYM from cattle feed rations. This could have had a liming effect that increased soil acidity levels (Chu et al, 2017) and reduced the acidification caused by nitrogen fertilizer application. It is known that FYM application increases microbial activity and hydrophobic properties, which enhances WSA stability, but the interaction between WSA stability and FYM application was more complicated in the current study.…”