Institut für Kulturpflanzenwissenschaften

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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; Herrmann, Michelle Natalie; Institute of Crop Science, Department of Fertilization and Soil Matter Dynamics, University of Hohenheim, Stuttgart, Germany; Griffin, Lydia Grace; Institute of Crop Science, Department of Fertilization and Soil Matter Dynamics, University of Hohenheim, Stuttgart, Germany; John, Rebecca; Institute of Crop Science, Department of Fertilization and Soil Matter Dynamics, University of Hohenheim, Stuttgart, Germany; Mosquera-Rodríguez, Sergio F.; Institute of Crop Science, Department of Fertilization and Soil Matter Dynamics, University of Hohenheim, Stuttgart, Germany; Nkebiwe, Peteh Mehdi; Institute of Crop Science, Department of Fertilization and Soil Matter Dynamics, University of Hohenheim, Stuttgart, Germany; Chen, Xinping; College of Resources and Environment, Academy of Agricultural Sciences, Southwest University, Chongqing, China; Yang, Huaiyu; College of Resources and Environment, Academy of Agricultural Sciences, Southwest University, Chongqing, China; Müller, Torsten; Institute of Crop Science, Department of Fertilization and Soil Matter Dynamics, University of Hohenheim, Stuttgart, Germany
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.
Local and systemic metabolic adjustments to drought in maize: hydraulic redistribution in a split‐root system
(2022) Werner, Lena Maria; Hartwig, Roman Paul; Engel, Isabelle; Franzisky, Bastian Leander; Wienkoop, Stefanie; Brenner, Martin; Preiner, Julian; Repper, Dagmar; Hartung, Jens; Zörb, Christian; Wimmer, Monika Andrea
Background: It is yet unknown how maize plants respond to a partial root drying under conditions of a limited total water supply, and which adaptation mechanisms are triggered under these conditions. Aims: The aims of this study were to assess whether partial root drying results in distinguishable local and systemic physiological and metabolic drought responses, and whether compensatory water uptake and/or alteration of root architecture occurs under these conditions. Methods: Maize plants were grown in a split-root system. When plants were 20 days old, the treatments ‘well-watered’, ‘local drought’ and ‘full drought’ were established for a period of 10 days. Shoot length and gas exchange were measured non-destructively, root exudates were collected using a filter system and biomass, relative water content, osmolality and proline content were determined destructively at final harvest. Results: Local drought triggered stress responses such as reduced biomass, shoot length, relative water content and increased osmolality. Maintained root growth was systemically achieved by hydraulic redistribution rather than by altering root architecture. Local and systemic osmolyte adjustments contributed to this hydraulic redistribution. Conclusions: Both local and systemic metabolic responses helped the plants to induce hydraulic redistribution, enhance water availability and in consequence plant water relations. This resulted in a surprisingly well-maintained root growth even in the drought stressed root compartment.
Long-term breeding progress of yield, yield-related, and disease resistance traits in five cereal crops of German variety trials
(2021) Laidig, Friedrich; Feike, T.; Klocke, B.; Macholdt, J.; Miedaner, Thomas; Rentel, D.; Piepho, Hans-Peter
Plant breeding and improved crop management generated considerable progress in cereal performance over the last decades. Climate change, as well as the political and social demand for more environmentally friendly production, require ongoing breeding progress. This study quantified long-term trends for breeding progress and ageing effects of yield, yield-related traits, and disease resistance traits from German variety trials for five cereal crops with a broad spectrum of genotypes. The varieties were grown over a wide range of environmental conditions during 1988–2019 under two intensity levels, without (I1) and with (I2) fungicides and growth regulators. Breeding progress regarding yield increase was the highest in winter barley followed by winter rye hybrid and the lowest in winter rye population varieties. Yield gaps between I2 and I1 widened for barleys, while they shrank for the other crops. A notable decrease in stem stability became apparent in I1 in most crops, while for diseases generally a decrasing susceptibility was found, especially for mildew, brown rust, scald, and dwarf leaf rust. The reduction in disease susceptibility in I2 (treated) was considerably higher than in I1. Our results revealed that yield performance and disease resistance of varieties were subject to considerable ageing effects, reducing yield and increasing disease susceptibility. Nevertheless, we quantified notable achievements in breeding progress for most disease resistances. This study indicated an urgent and continues need for new improved varieties, not only to combat ageing effects and generate higher yield potential, but also to offset future reduction in plant protection intensity.
Phosphorus- and water- deficiency induced morpho-physiological and yield changes in maize (Zea mays L.)
(2024) Ning, Fangfang; Graeff-Hönninger, Simone
Phosphorus (P) is a nonrenewable and finite resource for all living things. It plays a crucial role as an essential nutrient in crop production. However, plants have low efficiency in utilizing P due to its immobility and low bioavailability. P deficiency can cause irreversible effects, particularly during the early stages of maize growth. Drought further exacerbates nutrient uptake challenges, especially for P, by limiting its diffusion in the soil. Therefore, the dual stress of drought and P deficiency restricts plants' shoot and root growth. It is necessary to investigate the interaction between P deficiency and drought and better understand the response mechanisms, as the effect of P deficiency on plant growth precedes the plant's own drought regulatory mechanisms. In Paper I, the effects of placed diammonium phosphate (DAP) and rock phosphate (RP) on the growth and development of two maize cultivars (Stabil and Ricardinio) were investigated combined with soil liming. Maize cultivars differed in their P utilization characteristics under low-P field conditions. The results showed that RP resulted in a lower leaf area index and light interception than DAP. This led to a 33% lower silage yield and a 29% lower P content at harvest. The PUE of RP was found to be 18%, which is 37% lower than that of DAP. Furthermore, soil liming reduced shoot biomass and caused a 35% decrease in shoot P content at the six-leaf stage. Maize cultivar ‘Stabil’ showed higher yield and P uptake. This paper demonstrated that placed RP could not be used as a substitute for DAP in silage maize production regardless of the application of lime to the soil. Paper II explored the impact of different types of P fertilizer (DAP and RP) on the root systems of maize. The results showed that P deficiency in the early stages of growth hindered root growth. However, in later stages, the roots exhibited enhanced lateral root growth in response to P deficiency. Although the differences in organic acids and phytohormones across different zones of the maize root system were not significant due to the delayed sampling, it is still feasible and necessary to conduct further investigations on organic acids and phytohormones in various root locations. Paper III tested deep P fertilizer placement as a strategy to alleviate combined drought and P deficiency stress in maize. It was tested under greenhouse conditions involving three factors: P fertilizer amount (low-P: LP, and high-P: HP), fertilizer placement (mixed (M, 0-18 cm), lower (L, 10-18 cm), and upper (U, 0-9 cm)), and soil water content (DS, 45% of soil water holding capacity (WHC)) and well-watered: WW, 75% WHC) and well-watered: WW). LP decreased shoot P content and both root and shoot biomass compared to HP. Under DS, root biomass increased by 50% and 95% in 0-18 and 10-18 cm depth at the fourth-leaf stage compared to WW treatment. However, root biomass decreased by at least 41% in different depths at the tenth leaf stage. Plants under DS consistently exhibited lower shoot biomass and P uptake at both stages. Although L-DS did not improve shoot growth and P uptake until the tenth-leaf stage, more than 55% higher root biomass and increased root length could be found in 10-18 cm depth compared to M-DS and U-DS treatments. This could potentially enhance P exploration in a larger soil volume and enable water absorption from deeper soil layers. However, no advantage in P uptake was observed with LP and HP until the ten-leaf stage. In conclusion, this thesis highlights the importance of optimizing P utilization strategies in maize production systems facing the dual challenges of P deficiency and drought stress. While soil liming and cultivar selection can help, high-solubility P fertilizers like DAP remain irreplaceable by RP due to their superior ability to support root development. It also discussed the possibilities and mechanisms for mitigating P and water- deficiency by promoting root growth in deeper soil layers through applying P fertilizers. This study provides a comprehensive evaluation of the feasibility of various maize cultivation and management practices under combined P deficiency and drought conditions, offering valuable references and practical guidelines for sustainable maize production in resource-limited environments.

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