Influence of Fertilization Methods and Types on Wheat Rhizosphere Microbiome Community and Functions

To investigate the effects of fertilization methods and types on wheat rhizosphere microorganisms, macroelement (N, K) and microelement (Zn) fertilizers were applied on wheat by foliar spraying (FS) and root irrigation (RI) methods in a field experiment. The results indicated that fertilization methods and types can have significant impacts on the diversity and structure of rhizospheric microorganisms in wheat. The application method produced more significant effects than the fertilizer type. RI-N played a more important role in improving the wheat yield and quality and affected the changes in some nitrogen-fixing bacterial communities. Finally, eight strains of bacteria belonging to Pseudomonas azotoformans and P. cedrina showed positive effects on the growth of wheat seedlings. Overall, our study provides a better understanding of the dynamics of wheat rhizosphere microbial communities and their relation to fertilization, yield, and quality, showing that plant growth-promoting rhizobacteria with nitrogen fixing may be a potential approach for more sustainable agriculture production.

Plant growth-promoting bacteria isolated from earthworms enhance spinach growth and its phytoremediation potential in metal-contaminated soils

The aim of this study was to evaluate the impact of metal-tolerant plant growth-promoting bacteria (PGPB) isolated from the chloragogenous tissue of Aporrectodea molleri, which represents a unique habitat. Our objectives were to investigate their effects on the growth of Spinacia oleracea under heavy metal stress and assess their potential for enhancing phytoremediation capabilities. The experiment was conducted in an alkaline soil contaminated with 7 mg kg-1 of cadmium, 100 mg kg-1 of nickel, 150 mg kg-1 of copper, 300 mg kg-1 of Zinc, and mg kg-1 of 600 Manganese. The results showed that heavy metal stress considerably diminished root (42.8%) and shoot length (60.1%), biomass (80%), chlorophyll content (41%), soil alkaline (45%), and acid (51%) phosphatases (42%) and urease (42%). However, soil inoculation with bacterial isolates remarkably improved plant growth. Soil bioaugmentation increased spinach growth (up to 74.5% for root length, up to 106.3% for shoot length, and up to 5.5 folds for fresh biomass) while significantly increasing soil enzyme activity and NPK content. Multivariate data analysis indicated that soil inoculation with Bacillus circulans TC7 promoted plant growth while limiting metal bioaccumulation, whereas Pseudomonas sp. TC33 and Bacillus subtilis TC34 increased metal bioaccumulation in spinach tissues while minimizing their toxicity. Our study confirms that earthworms are a reservoir of multi-beneficial bacteria that can effectively improve phytoremediation efficiency and mitigate the toxic effects of heavy metals on plant growth. Further studies are needed to investigate the long-term effects and feasibility of using these isolates as a consortium in field applications.

The responses of CO2 emission to nitrogen application and earthworm addition in the soybean cropland

The effects of nitrogen application or earthworms on soil respiration in the Huang-Huai-Hai Plain of China have received increasing attention. However, the response of soil carbon dioxide (CO2) emission to nitrogen application and earthworm addition is still unclear. A field experiment with nitrogen application frequency and earthworm addition was conducted in the Huang-Huai-Hai Plain. Results showed nitrogen application frequency had a significant effect on soil respiration, but neither earthworms nor their interaction with nitrogen application frequency were significant. Low-frequency nitrogen application (NL) significantly increased soil respiration by 25%, while high-frequency nitrogen application (NH), earthworm addition (E), earthworm and high-frequency nitrogen application (E*NH), and earthworm and low-frequency nitrogen application (E*NL) also increased soil respiration by 21%, 21%, 12%, and 11%, respectively. The main reason for the rise in soil respiration was alterations in the bacterial richness and keystone taxa (Myxococcales). The NH resulted in higher soil nitrogen levels compared to NL, but NL had the highest bacterial richness. The abundance of Corynebacteriales and Gammaproteobacteria were positively connected with the CO2 emissions, while Myxococcales, Thermoleophilia, and Verrucomicrobia were negatively correlated. Our findings indicate the ecological importance of bacterial communities in regulating the carbon cycle in the Huang-Huai-Hai Plain.

Augmentation of plant biomass productivity using epigeic earthworm Perionyx excavatus and Eisenia fetida as soil nutrient facilitators

With the increasing demand for organic food production, the earthworm is used as a soil nutrient facilitator. The present study was conducted to assess the effect of epigeic earthworms Perionyx excavatus and Eisenia. fetida on soil nutrients and the consequent improvement of biomass productivity and yield of Capsicum chinense Jacq and Zea mays L. The experiment was conducted in 5 L and 15 L capacity plastic pots for C. chinense and Z. mays with 150 g and 300 g of half-decomposed cow dung, respectively. It was observed that the weekly harvest rate of ripened chili was 17.59 g, 13.91 g, and 9.24 g in P. excavatus, control, and E. fetida pot showing 26.49% higher in P. excavatus. Also, the total kernel count per corn was significantly different (F(2, 9) = 37.78, p < 0.05), with the highest kernel present in P. excavatus(333.5 ± 13.5), followed by E. fetida(261.5 ± 16.5) and control (235 ± 22). The impact of P. excavatus was more perceptible in C. chinense, indicated by higher leaf biomass (69.16%), root length (30.14%), and fruit harvest (71.03%). However, the effect of E. fetida was noticed more in Z. mays (stem length, 19.24%, stem biomass, 14.39%, root biomass, 20.9%, kernel count, 41.91%, and kernel weight, 95.07%). Enhanced plant productivity was also supported by an increasing soil nutrient turnover in organic carbon (OC) (25.76% and 23.4%), Phosphorus (P) (31.03% and 25.67%), and Potassium (K) (41.67% and 12.26) in P. excavatus and E. fetida worked soil respectively. The findings indicate that earthworms have a notable impact on plant biomass productivity by promoting the mineralization of soil nutrients and imply on possibility of organic cultivation of seasonal vegetables without using synthetic fertilizers.

Turning earthworms into moonworms: Earthworms colonization of lunar regolith as a bioengineering approach supporting future crop growth in space

The earthworms beneficial effects on soils may be promising to improve lunar soil fertility, enabling the use of local substrates for space farming. Herein, we investigated the effects of the lunar regolith simulant (LHS-1) at different concentrations in cow manure mixtures on the survival and fitness of Eisenia fetida. During 14 and 60-day experiments, although E. fetida showed an increased mortality with LHS-1 alone, most of the population survived. More numerous tunnels were observed when exposed to the higher concentrations of LHS-1 (poor in nutrients for earthworms). This may be related to an increased mobility for food search. The cocoons production was not affected by different substrate treatments, except for the highest concentration of LHS-1. No effects of different LHS-1 concentrations on the amount of ingested substrate were recorded. This study shows that E. fetida can potentially colonize lunar regolith representing a future valuable biological tool for supporting crops growth on the Moon.

Bio-Priming with Compatible Rhizospheric Microbes Enhances Growth and Micronutrient Uptake of Red Cabbage

Red cabbage is known as the millennium’s functional food, which has a lot of importance in our diet because of the health-promoting ingredients present in it. The current study investigated the synergistic relationship of rhizospheric-competent microbial agents (Trichoderma harzianum, Pseudomonas fluorescens, and Bacillus subtilis) in modulating the performance of red cabbage under the field conditions of Middle Gangetic Plains, India. Growth parameters were studied at three developmental stages, viz., pre-cupping, early head formation, and maturity. Our results suggested that the dual application of T. harzianum + P. fluorescens along with the 75% recommended dose of fertilizers (RDF) increased the number of leaves (24.6), leaf area (537.2 cm2), root length (19.8 cm), and micronutrient uptake (Fe, Mn, and Cu) by head of the crop, whereas the co-inoculation of P. fluorescens and B. subtilis along with 75% RDF enhanced plant spread (39.0 cm), earliness (95.2 days), and Zn uptake. Maximum plant height (28.7 cm) and chlorophyll (SPAD, 77.3) were recorded in 100% RDF (120:60:60 kg ha−1) and the combination of T. harzianum + B. subtilis along with 75% RDF, respectively. Interestingly, consortium (T. harzianum + P. fluorescens) bio-primed plants recorded about 14% higher root length in comparison to plants receiving sole fertilizers. The regression analysis revealed a significant relationship of Fe and Mn uptake with chlorophyll (SPAD) and between Zn uptake and the earliness of the crop. The present study indicated that seedling bio-priming with the dual consortium of efficient bio-agents is a viable strategy to lessen our dependence on chemical fertilizers for improving red cabbage production.