Agriculture in the 21st century is facing multiple challenges, such as those related to soil fertility, climatic fluctuations, environmental degradation, urbanization, and the increase in food demand for the increasing world population. In the meanwhile, the scientific community is facing key challenges in increasing crop production from the existing land base. In this regard, traditional farming has witnessed enhanced per acre crop yields due to irregular and injudicious use of agrochemicals, including pesticides and synthetic fertilizers, but at a substantial environmental cost. Another major concern in modern agriculture is that crop pests are developing pesticide resistance. Therefore, the future of sustainable crop production requires the use of alternative strategies that can enhance crop yields in an environmentally sound manner. The application of rhizobacteria, specifically, plant growth-promoting rhizobacteria (PGPR), as an alternative to chemical pesticides has gained much attention from the scientific community. These rhizobacteria harbor a number of mechanisms through which they promote plant growth, control plant pests, and induce resistance to various abiotic stresses. This review presents a comprehensive overview of the mechanisms of rhizobacteria involved in plant growth promotion, biocontrol of pests, and bioremediation of contaminated soils. It also focuses on the effects of PGPR inoculation on plant growth survival under environmental stress. Furthermore, the pros and cons of rhizobacterial application along with future directions for the sustainable use of rhizobacteria in agriculture are discussed in depth.

Cadmium (Cd) is one of the heavy metals that negatively affects the growth of plants. High solubilization in water leads Cd to enter into plants quite easily, thus decreasing seed germination, photosynthesis, and transpiration. It also shows an antagonistic effect with many of the plants’ nutrients like Mn, Ca, K, Mg and Fe. Nowadays, inoculation of plants with ACC deaminase (ACCD) rhizobacteria to mitigate Cd’s adverse effects has drawn the attention of environmental microbiologists. The rhizobacteria secrete organic compounds that can immobilize Cd in soil. Therefore, this study was accomplished to investigate the effect of ACCD plant growth promoting rhizobacteria (PGPR) on the bitter gourd under Cd stress. There were six treatments consisting of two ACCD PGPR (Stenotrophomonas maltophilia and Agrobacterium fabrum) strains and inorganic fertilizers at two levels of Cd, i.e., 2 (Cd2) and 5 mg kg⁻¹ soil (Cd5). The results showed A. fabrum with the recommended NPK fertilizer (RNPKF) significantly increased the vine length (48 and 55%), fresh weight (24 and 22%), and contents of chlorophyll a (79 and 50%), chlorophyll b (30 and 33%) and total chlorophyll (61 and 36%), over control at the two Cd levels i.e., Cd2 and Cd5, respectively. In conclusion, the recommended NPK fertilizer + A. fabrum combination is a very effective treatment with which to immobilize Cd in soil for the improvement of bitter gourd growth.

Biochar application to the soil has been recommended as a carbon (C) management approach to sequester C and improve soil quality. Three-year experiments were conducted to investigate the interactive effects of three types of amendments on microbial biomass carbon, soil dehydrogenase activity and soil microbial community abundance in luvisols of arable land in the Czech Republic. Four different treatments were studied, which were, only NPK as a control, NPK + cattle manure, NPK + biochar and NPK + combination of manure with biochar. The results demonstrate that all amendments were effective in increasing the fungal and bacterial biomass, as is evident from the increased values of bacterial and fungal phospholipid fatty acid analysis. The ammonia-oxidizing bacteria population increases with the application of biochar, and it reaches its maximum value when biochar is applied in combination with manure. The overall results suggest that co-application of biochar with manure changes soil properties in favor of increased microbial biomass. It was confirmed that the application of biochar might increase or decrease soil activity, but its addition, along with manure, always promotes microbial abundance and their activity. The obtained results can be used in the planning and execution of the biochar-based soil amendments.

Landfill leachates are potentially harmful to the environment and to human health. The objective of this study was to characterize leachates in order to analyze whether a relationship exists between the stored waste and the composition of leachates, and to detect possible leakages of pollutants into the environment. To achieve these objectives, field data, Global Positioning System data and physico-chemical data were used. Biological tests are becoming increasingly popular in determining leachate toxicity; therefore, two toxicity tests were performed with the seeds of white mustard (Sinapis alba L.) and duckweed (Lemna minor L.). Leachates were sampled from the leachate pond. Groundwater quality was monitored by using drill holes. The research and analysis carried out are important to determine their potential impact on agricultural areas located near the landfill. Demonstrably increased (P < 0.05) concentrations of heavy metals were detected only in the leachate pond which closes the landfill body, where it links up with the landfill insulation layer. Water sampled from drill holes reaching into groundwater was not contaminated. The results showed that the leachates did not leak outside the landfill. Nevertheless, they were found to be phytotoxic. Both toxicity tests showed that the increasing amount of leachates resulted in the increasing growth inhibition of the tested plants. The proper handling of leachates should have been ensured.

Suitability of the vegetation indices of normalized difference vegetation index (NDVI), blue normalized difference vegetation index (BNDVI), and normalized difference yellowness index (NDYI) obtained by means of UAV at the flowering stage of oil seed rape for the prediction of seed yield and usability of these vegetation indices in the identification of anomalies in the condition of the flowering growth were verified based on the regression analysis. Correlation analysis was performed to find the degree of yield dependence on the values of NDVI, BNDVI, and NDYI indices, which revealed a strong, significant linear positive dependence of seed yield on BNDVI (R = 0.98) and NDYI (R = 0.95). The level of correlation between the NDVI index and the seed yield was weaker (R = 0.70) than the others. Regression analysis was performed for a closer determination of the functional dependence of NDVI, BNDVI, and NDYI indices and the yield of seeds. Coefficients of determination in the linear regression model of NDVI, BNDVI, and NDYI indices reached the following values: R² = 0.48 (NDVI), R² = 0.95 (BNDVI), and R² = 0.90 (NDYI). Thus, it was shown that increased density of yellow flowers decreased the relationship between NDVI and crop yield. The NDVI index is not appropriate for assessing growth conditions and prediction of yields at the flowering stage of oil seed rape. High accuracy of yield prediction was achieved with the use of BNDVI and NDYI. The performed analysis of NDVI, BNDVI, and NDYI demonstrated that particularly the BNDVI and NDYI indices can be used to identify problems in the development of oil seed rape growth at the stage of flowering, for their precise localization, and hence to targeted and effective remedial measures in line with the principles of precision agriculture.

The presented paper deals with the analysis of potential differences between organic waste compost (C_BD), vermicompost (C_VER) and mineral fertilizer (MF; 27% of N) applications affecting the quality of arable soil by influencing microbial activity therein. The selected types of compost represent alternatives to conventional organic fertilizers, which are, however, not available to Czech and Slovak farmers in sufficient amounts. Their mutual comparison and the comparison with organic fertilizers aim to provide farmers further information about their influence on arable land and thus to give them the possibility of deciding on the most suitable amendments. To demonstrate the effect of these amendments, six variants were prepared: one without the addition of fertilizers; two variants with the addition of 40 Mg/ha of C_VER and C_BD; one variant with the addition of double dosed C_VER (80 Mg/ha), and the remaining two variants were fertilized only with MF (0.22 Mg/ha) and with the combination of C_VER (0.20 Mg/ha) and MF (0.11 Mg/ha). Substrate induced respiration (SIR), basal respiration (BS), microbial carbon (C_mic) and enzymatic activities (hydrolysis of fluorescein diacetate—FDA, dehydrogenase activity—DHA, and phosphatase activity—PA) were used to evaluate the effect of C_BD, C_VER and MF application on the soil quality. Both organic and mineral amendments affected BS and SIR. The highest BS and SIR rates were found in variants with compost application (C_VER and C_BD). All variants treated with the mineral fertilizer showed the lowest level of enzyme activities; lower by about 30% in comparison with variants where C_VER, C_BD and the combination of MF and C_VER were applied. We found insignificant differences between the individual types of compost. More importantly, we compared the situation at the beginning of the experiment and after its end. It was found that the application of mineral fertilizers automatically led to the deterioration of all enzymatic parameters, on average by more than 25%, as compared with the situation at the beginning of the experiment. However, when the mineral fertilizer dose was supplemented with organic amendments (C_VER), this negative effect was eliminated or significantly reduced. Furthermore, both composts (C_VER and C_BD) positively affected plant biomass production, which reached a level of production enhanced by the MF. Results clearly showed that the application of both compost types could be used to improve soil quality in agriculture.