Browsing by Person "Herrmann, Michelle Natalie"

Now showing 1 - 3 of 3

A global network meta-analysis of the promotion of crop growth, yield, and quality by bioeffectors
(2022) Herrmann, Michelle Natalie; Wang, Yuan; Hartung, Jens; Hartmann, Tobias; Zhang, Wei; Nkebiwe, Peteh Mehdi; Chen, Xinping; Müller, Torsten; Yang, Huaiyu
Bioeffector (BE) application is emerging as a strategy for achieving sustainable agricultural practices worldwide. However, the effect of BE on crop growth and quality is still controversial and there is still no adequate impact assessment that determines factors on the efficiency of BE application. Therefore, we carried out a network metaanalysis on the effect of BEs using 1,791 global observations from 186 studies to summarize influencing factors and the impact of BEs on crop growth, quality, and nutrient contents. The results show that BEs did not only improve plant growth by around 25% and yield by 30%, but also enhanced crop quality, e.g., protein (55% increase) and soluble solids content (75% increase) as well as aboveground nitrogen (N) and phosphate (P) content by 28 and 40%, respectively. The comparisons among BE types demonstrated that especially non-microbial products, such as extracts and humic/amino acids, have the potential to increase biomass growth by 40–60% and aboveground P content by 54–110%. The soil pH strongly influenced the efficiency of the applied BE with the highest effects in acidic soils. Our results showed that BEs are most suitable for promoting the quality of legumes and increasing the yield of fruits, herbs, and legumes. We illustrate that it is crucial to optimize the application of BEs with respect to the right application time and technique (e.g., placement, foliar). Our results provide an important basis for future research on the mechanisms underlying crop improvement by the application of BEs and on the development of new BE products.
Limitations of soil-applied non-microbial and microbial biostimulants in enhancing soil P turnover and recycled P fertilizer utilization: A study with and without plants
(2024) Herrmann, Michelle Natalie; Griffin, Lydia Grace; John, Rebecca; Mosquera-Rodríguez, Sergio F.; Nkebiwe, Peteh Mehdi; Chen, Xinping; Yang, Huaiyu; Müller, Torsten
Introduction: Phosphorus recovery from waste streams is a global concern due to open nutrient cycles. However, the reliability and efficiency of recycled P fertilizers are often low. Biostimulants (BS), as a potential enhancer of P availability in soil, could help to overcome current barriers using recycled P fertilizers. For this, a deeper understanding of the influence of BSs on soil P turnover and the interaction of BSs with plants is needed. Methods: We conducted an incubation and a pot trial with maize in which we testednon-microbial (humic acids and plant extracts) and microbial BSs (microbial consortia) in combination with two recycled fertilizers for their impact on soil P turnover, plant available P, and plant growth. Results and discussion: BSs could not stimulate P turnover processes (phosphatase activity, microbial biomass P) and had a minor impact on calcium acetate-lactate extractable P (CAL-P) in the incubation trial. Even though stimulation of microbial P turnover by the microbial consortium and humic acids in combination with the sewage sludge ash could be identified in the plant trial with maize, this was not reflected in the plant performance and soil P turnover processes. Concerning the recycled P fertilizers, the CAL-P content in soil was not a reliable predictor of plant performance with both products resulting in competitive plant growth and P uptake. While this study questions the reliability of BSs, it also highlights the necessity toimprove our understanding and distinguish the mechanisms of P mobilization in soil and the stimulation of plant P acquisition to optimize future usage.
Rhizosphere manipulation to optimize fertilizer and soil phosphate availability
(2024) Herrmann, Michelle Natalie; Müller, Torsten
Phosphorus (P), which occurs as orthophosphate in living organisms, in soil, and in fertilizers, primarily derives from non-renewable resources. Due to open nutrient cycles, most applied P is at risk of ending up in the environment. At the same time, P fertilization in modern agricul-tural systems is inefficient. In Europe, farmers tended to apply more P than the crop’s demand because of P immobilization in soil and the resulting poor fertilizer efficiency. This has led to an accumulation of P in the soil, and environmental P pollution from leaching, soil erosion, and runoff. This work aimed to increase soil P availability and promote the use of recycled P ferti-lizers by improving the P fertilizer use efficiency. The approach compromised various strategies, which shall be evaluated based on their effectiveness in promoting plant growth and P acquisi-tion under P limitation and stimulating P turnover processes close to the rhizosphere. The first study addressed the impact of placed starter fertilization on yield, N and P uptake as well as on nutrient use efficiency. In the last decades, numerous studies have been published, enabling us to summarize the results. Therefore, the positive effect of placed starter fertilization was evaluated by conducting a network meta-analysis. Additionally, one aim was to identify relevant environmental and management factors influencing the effectiveness under field conditions. Here, it was found that placed starter fertilization increased yield by 9.4 %. P uptake and P use efficiency benefitted significantly from a placed starter fertilization, whereas N uptake and N use efficiency were unaffected. The climate was identified as one of the most decisive environmental factors, with arid climates and hyper-humid climates showing the greatest yield advantage. Using ammonium-based fertilizers enhanced the positive effect on yield and P use efficiency. In the second study, biostimulants, as potential enhancers of P availability in soil, were tested for their impact on P turnover in soil, and their ability to improve the fertilizer use efficiency of recycled fertilizers. To distinguish between the influence of biostimulants on soil and the plant-biostimulant interaction, an incubation and a pot trial with maize were designed. Non-microbial and microbial biostimulants were applied to the soil in combination with two recycled P fertilizers. This study revealed that biostimulants did not stimulate P turnover processes with phosphatase activity or microbial biomass P as indicators and only minorly influenced CAL-P in the incubation trial. Likewise, the biostimulants did not affect plant growth and nutrient acquisition in the pot trial. In summary, albeit being a promising strategy to improve P fertilizer utilization, biostimulants were proved again to be unreliable. Two studies focused on integrating legumes in maize-based cropping systems to optimize the use of P stored in the rooting zone and derived from poorly available (recycled) fertilizers. Legume-based crop rotations and legume-maize intercropping systems were tested in pot trials. Key P mobilization processes as well as plant performance and P uptake were studied as indicators for the P use. Legumes consistently stimulated soil P turnover processes independent of the fertilization regime indicated by a higher phosphatase activity and higher Mn-leaf concentration which correlated with the root exudation of carboxylates. Nevertheless, maize did not benefit from integrating legumes into the cropping system. In the crop rotation, maize following a legume did not increase biomass and P offtake compared to maize after maize. With the rel-atively lower biomass production of the legume pre-crop compared to the maize pre-crop, these crop rotations could not keep up with the maize-maize rotation in terms of total biomass pro-duction and P offtake. Concerning the intercropping, maize intercropped with beans was hin-dered in growing due to the competition for limited resources. However, the total biomass pro-duction of the maize–bean intercropping system was significantly higher than the maize monoculture and could compete with the conventional maize monoculture fertilized with triple super phosphate. In summary, this work provides a comprehensive overview and evaluation of future possibili-ties for improving P use efficiency. In combination with recycled fertilizers, intercropping legumes, and a placed starter fertilization can contribute to sustainable P management in the future.