Purification Effect of the Aquaculture Wastewater and Sediment by Microbial Nanospheres with Different Material Ratios and Dosing Methods

Nanospheres were prepared by different materials of nano-bamboo charcoal powder, zeolite powder, and aquaculture pond sediment in different ratios. It was then fermented with effective microorganisms (EM) active calcium liquid to synthesize the bioactive microbial nanospheres. These nanospheres were used to compare the purification effect of ammonium nitrogen (NH4+-N), total nitrogen (TN), and total phosphorus (TP) pollutants in aquaculture wastewater. The indoor simulation experiment was also conducted to compare the different dosage methods (one-time dosing without aeration, multiple dosing without aeration, and multiple dosing with aeration) of microbial nanospheres on the removal of organic matter (OM) and effect of the biodegradability (G value) in aquaculture sediment. The results obtained indicated that the purification effect was most remarkable when the mass ratio of nano-bamboo charcoal powder: zeolite powder: pond sediment was 10%: 15%: 75%, in which the maximum removal rate of NH4+-N, TN, and TP reached up to 84.86%, 52.15%, and 50.35%, respectively. Under the same microbial nanospheres amount, the effect of one-time addition on the removing of OM in sediment was not as effective as that of multiple dosing. After the 20th day, the removal rate of OM reached 25.99% in multiple dosing treatment and it was 35.58% higher than one-time dosing treatment. The OM content in sediment was reduced by 32.38% under the multiple dosing with aeration treatment. Multiple dosing of microbial nanospheres with aeration increased the G value of sediment about 337.0%. In situ experiment further indicated that the microbial nanospheres dosage with aeration had a good sediment bio-remediation effect, which is applicable to solve the problem of endogenous pollution in aquaculture ponds

Soil C:N:P Stoichiometry Succession and Land Use Effect after Intensive Reclamation: A Case Study on the Yangtze River Floodplain

The coupling cycles of soil carbon (C), nitrogen (N), and phosphorus (P) have a significant impact on biogeochemical processes and ecosystem services. For centuries, large areas of floodplain wetlands in China have been extensively reclaimed for agricultural purposes due to population growth. However, little is known about the evolution of soil C:N:P stoichiometry along a reclamation chronosequence, particularly across different land uses. In this study, we investigated the variations in soil C:N:P ratios with land use and time gradients along a reclamation chronosequence comprising c. 0, 60, 100, 280, 2000, and 3000 years. Land reclamation induced nutrient decoupling, as it facilitated C and N accumulation from biological processes but restricted P supply controlled by geochemical processes. Soil C and N sequestration reached a stable state after 2000 years, while P declined steadily from 60 years. Soil C/P and N/P increased significantly and were controlled by organic carbon (OC) and total nitrogen (TN), respectively, indicating that an increase in C and N could also promote P uptake. Soil C/N declined in the first 60 years and stabilized at a threshold of 10:1. Different land use patterns following reclamation resulted in distinct soil nutrient structures. Paddies retained more OC and TN but exhibited lower adsorption of total phosphorus (TP) compared to adjacent dryland, leading to significant differences in C/P and N/P between land uses. Based on the redundancy analysis and random forest model, soil OC and TN were mainly affected by the abundance of bacteria metabolizing cellulose, while metal oxides, including Fe2O3 and CaO, could best predict TP. Soil C/P and N/P were mainly driven by soil texture and rose significantly with the increasing proportion of clay particles. Our study suggests that as reclamation proceeds, more anthropogenic management is required to regulate potential nutrient imbalances in order to prevent adverse effects on crop growth, soil quality, and ecosystem health. Additionally, any fertilization strategy should be developed based on dryland C and N deficiencies, and lack of P in paddies

Nitrate availability controls translocation of the transcription factor NAC075 for cell-type-specific reprogramming of root growth

Plant root architecture flexibly adapts to changing nitrate (NO3−) availability in the soil; however, the underlying molecular mechanism of this adaptive development remains under-studied. To explore the regulation of NO3−-mediated root growth, we screened for low-nitrate-resistant mutant (lonr) and identified mutants that were defective in the NAC transcription factor NAC075 (lonr1) as being less sensitive to low NO3− in terms of primary root growth. We show that NAC075 is a mobile transcription factor relocating from the root stele tissues to the endodermis based on NO3− availability. Under low-NO3− availability, the kinase CBL-interacting protein kinase 1 (CIPK1) is activated, and it phosphorylates NAC075, restricting its movement from the stele, which leads to the transcriptional regulation of downstream target WRKY53, consequently leading to adapted root architecture. Our work thus identifies an adaptive mechanism involving translocation of transcription factor based on nutrient availability and leading to cell-specific reprogramming of plant root growth