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Many studies describe the positive effect of mycorrhiza, but few report on negative effects. Furthermore, there is a research gap on the mechanisms under which conditions the symbiotic mycorrhizal plant interaction or a parasitic one predominates. The study was conducted as a field experiment over three years to investigate the effect of mycorrhiza (Rhizoglomus intraradices) and soil bacteria applications on fertile soil. A standard fertilizer (diammonium phosphate) and two microgranular fertilizers (mineral and organomineral) were applied alone or in combination with the biostimulants mycorrhiza and/or soil bacteria (Bacillus velezensis). The application of the mycorrhiza as the only biostimulant resulted in lower yields compared to all fertilizer variants without the mycorrhiza or with mycorrhiza in combination with soil bacteria in the dry years 2015 (p = 0.0241) and 2016 (p = 0.0003). The usage of soil bacteria alone, or soil bacteria with fertilizer, resulted in few occasional significant differences. The combination with soil bacteria raised the yield of mycorrhiza-treated fertilizer variants to a significant extent in 2015 (p = 0.0007) and 2016 (p = 0.0019). The negative effects of mycorrhiza application in this study were alleviated by the simultaneous use of soil bacteria. Treatments with organomineral microgranular fertilizer, which were expected to promote the naturally occurring soil microbiome more than the mineral fertilizer variants, were most negatively affected by the mycorrhiza. We hypothesize that the naturally occurring microbiome of the study site was already optimal for maize plants, and thus the successful introduction of other microorganisms through the application of the mycorrhiza and soil bacteria tended not to be beneficial. The present study is the first report on the negative influence of arbuscular mycorrhiza on maize yields gained with a standard fertilizer (diammonium phosphate) and two microgranular fertilizer, and the alleviation of that impact by combined application of soil bacteria. We conclude that the application of the used biostimulants may have negative impacts on maize yield if the soil is already rich in nutrients and water is the limiting factor.

Questions: Livestock management in rangelands depends on the production of plant biomass. Biomass production is driven by the temporal and spatial variability in precipitation, but our understanding of how precipitation variability mediates grazing effects on biomass production is still fragmented. Along a 600-km precipitation gradient we extracted biomass data to ask the questions: (a) what are the effects of grazing intensity on biomass production; (b) does grazing intensity interact with plant species richness to affect biomass production; and (c) how do plant functional groups respond to grazing and precipitation?. Location: Mongolia. Methods: Biomass was sampled along 15 grazing intensity transects within the precipitation gradient over two consecutive years. We modeled spatial variability in above-ground plant biomass using mixed-effects models. Normalized difference vegetation index (NDVI) data were combined with field-sampled biomass data to correct for inter-annual precipitation variation. The effects of species richness were modeled with respect to possible interactions with grazing intensity, and the composition of plant functional groups was modeled with respect to possible interactions between grazing intensity and precipitation. Results: Biomass was negatively correlated with grazing intensity and this effect increased as precipitation increased. Biomass was positively correlated with species richness in both years, but the strength of this effect and the interaction between species richness and grazing intensity differed between 2014 and 2015 in line with highly variable precipitation between both years. The plant functional groups grasses, sedges, legumes, wormwood and forbs had contrasting responses to grazing and precipitation. Conclusion: Biomass production in drylands is more vulnerable to changes in precipitation variability and grazing intensities in relatively moist and productive rangelands than in dry and unproductive ones. Future rangeland management needs to address potentially increasing precipitation variability in order to promote desired forage plants, and to preserve the positive effects of biodiversity for biomass production.

Mongolia contains some of the largest intact grasslands in the world, but is vulnerable to future changes in climate and continued increases in the number of domestic livestock. As these are two major drivers of change, it is important to understand interactions between the impact of climate and grazing on productivity of Mongolia’s rangelands and the livelihoods they sustain. We use a gridded, spatially explicit model, the Rangeland Production Model (RPM), to explore the simultaneous and interacting effects of climate and management changes on Mongolia’s rangeland and future livestock production. Comparing the relative impact of temperature, precipitation, and grazing intensity, varied individually and in combination, we find that climatic factors dominate impacts on forage biomass and animal diet sufficiency. Site rainfall strongly mediates the impact of grazing on standing biomass, such that more productive or higher-rainfall sites are more vulnerable to increases in grazing pressure. Gridded simulations covering Mongolia’s Gobi-Steppe ecoregion show that while rangeland biomass is generally predicted to increase under future climate conditions, interactions among spatially varying drivers create strong heterogeneity in the magnitude of change.

As a result of water regulation measures and the subsequent introduction of intensive use practices, riverine floodplains have suffered severe habitat and species losses. With the changed economic conditions and decrease in animal stocking rates after 1990, opportunities arose for the partial restoration of species-rich vegetation areas in East Germany. Sixty permanent plots were established in the lower Havel Valley in the federal state of Brandenburg from 1993 to 1999. We studied the effects of extensification and partial rewetting in this area during a monitoring programme that lasted until 2018. For this purpose, groundwater levels, historical land use, and soil chemical parameters were investigated, and the soil seed bank and phytosociological releves were sampled. Previous research has shown that an extended period of intensive grassland use eliminates the possibility of success in short- to medium-term natural restoration because of the lack of suitable propagules. Our question was as follows: how does a floodplain grassland respond to extensification and decreased water regulation in an area that experienced a shorter period of intensification in the past, such as the lower Havel floodplain? Tests of soil samples showed a depleted soil seed bank at the beginning of the monitoring period, but the seed bank was less depleted than those in other areas. Using cluster analysis followed by discriminant analysis, we identified water regime parameters and historical land-use intensity as the main drivers of vegetation differentiation. The classification resulted in the differentiation of vegetation into 13 plant communities. Plant communities were combined into 5 main groups based on their location in the ordination diagram of a detrended correspondence analysis. The shift in group centroids over time correlated with increases in the species diversity and moisture level for all groups. The altered species composition as a result of the changed water regime after 1990 influenced the usability of the grassland differently depending on the relief level. At the end of monitoring, vegetation at sites in the mesic moisture range was determined to have the highest fodder quality observed in this study. With increasing mean groundwater levels, the forage quality of the vegetation decreased until it was so low that the vegetation was hardly suitable for use as animal forage. The plant species diversity was negatively correlated with the plant-available P and Ellenberg N indicator value. Plant-available P, K and Mg showed evidence of leaching during the later study period. The abundance of red-listed species and extensive-use indicator species increased over the course of the study period. This positive trend was reversed by the extreme flood event in the summer of 2013. However, the high species richness and the species compositions of the reference communities were not equal in the other communities, even after almost 30 years of extensification. This finding underlines the importance of the few remaining meadows that are rich in typical floodplain species as donor areas of autochthonous seeds. The results of this study are discussed in light of sustainable management practices and global climate change.

The eutrophication of groundwater through widespread diammonium phosphate (DAP) fertilization and excessive farm fertilizer is one of the major problems in European agriculture. Organomineral microgranular fertilizers that have a reduced phosphorus (P) content, alone or in combination with biostimulants, offer promising alternatives to DAP fertilization. We conducted a field experiment with maize (Zea mays) on a marshland soil site in order to compare the yield increase and the phosphorus balance of DAP and microgranular fertilizer variants. P content of the soil on the study site is 3.9 g P per 100 g soil. Treatments involved a combination of two fertilizers, namely DAP or a P-reduced microgranular slow-release organomineral fertilizer (Startec) and the biostimulants mycorrhiza, humic substances and soil bacteria, applied individually or along with two of the above biostimulants. Fertilizer variants were also tested individually without additional biostimulants. One in four plots was used as a control, treated only with biogas slurry, to identify site-specific spatial variability and to implement correction factors to process raw data using standardized methods. Startec performed as well as DAP in terms of both the yield and corn cob ratio, while the P excess was lower in plots treated with Startec (av. = 4.5 kg P2O5 ha-1 ) compared to DAP (av. = 43.7 kg P2O5 ha-1 ). The latter differences are of statistical significance. Individual biostimulants and a combination of multiple biostimulants rarely resulted in significantly higher yields, with the exception of some combinations with humic substances and mycorrhiza in individual years. The influence of the climatic conditions in each of the years was higher than the influence of the biostimulants. However, average increases in yield over three years would be economically beneficial for farmers in the case of the applied humic substances product and mycorrhiza. An adequate alternative to DAP was found in the form of a P-reduced microgranular fertilizer from Startec.