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The study examines the effects of different fertilisation methods on greenhouse gas emissions in organic farming.

The severity of drought is predicted to increase across Europe due to climate change. Droughts can substantially impact terrestrial nitrogen (N) cycling and the corresponding microbial communities. Here, we investigated how ammonia-oxidizing bacteria (AOB), archaea (AOA), and comammox (complete ammonia oxidizers) respond to simulated drought in a rain-out shelter experiment in the DOK long-term field trial comparing different organic and conventional agricultural practices since 1978. This study is part of the MICROSERVICES (BiodivERsA) project aiming to understand and predict the effects of climate change on crop-associated microbiomes and their ecosystem functions. We monitored the diversity, the composition, and the abundance of ammonia-oxidizers for five months by Illumina-based amplicon sequencing and quantitative real-time PCR using the amoA gene as molecular marker. We found that the effect of drought varied depending on the ammonia-oxidizing community and also on the agricultural practices. The community structures of AOA and comammox were more strongly affected by drought than the AOB community structure. Drought also had a stronger impact on the community structure in the biodynamic (organic) cropping system than in both the mixed and mineral-fertilized conventional systems. The abundance of ammonia oxidizers was also influenced by drought, with comammox clade B exhibiting the strongest sensitivity to drought. The drought effect on the community abundance was more prominent in the biodynamic and mixed-conventional systems than in the mineral-fertilized conventional system. We further found a significant interaction between drought and agricultural practices on the abundance of all groups of ammonia-oxidizers except AOB. Overall, our study showed that the impact of drought on ammonia oxidizers was modulated by agricultural practices and varied with time as well as among members of ammonia-oxidizers. These results underscore the significance of agricultural

The impacts of climate change, such as drought, can affect soil microbial communities. These communities are crucial for soil functioning and crop production. Organic and conventional cropping systems promote distinct soil microbiomes and soil organic carbon contents, which might maintain different capacities to mitigate drought effects on cropping systems. A field-scale drought simulation was performed in long-term organically and conventionally managed cropping systems differing in fertilization and pesticide application. The soil microbiome was assessed during and after drought in bulk soil, rhizosphere, and roots of wheat. We found that drought shifted microbial community structures, affecting fungi more strongly than prokaryotes. Microbial communities associated with crops (i.e. rhizosphere and root) were more strongly influenced by drought compared to bulk soil communities. A drought legacy effect was observed in the bulk soil after harvesting and rewetting. The resistance and resilience of the soil microbiome to severe drought did not significantly differ across the organic and conventional cropping systems, although few individual genera (e.g. Streptomyces, Rhizophagus, Actinomadura, and Aneurinibacillus) showed system-specific drought responses. All cropping systems showed relative increases in potential plant growth-promoting genera under drought. This agricultural field study indicated that fungal communities might be less resistant to drought than prokaryotic communities in cropping systems and these effects get more pronounced in closer association with plants. Organic fertilization or the reduction in pesticide application might not have the ability to buffer severe drought stress and additional farming practices might have to be incorporated to improve drought tolerance in cropping systems.

Agricultural systems put severe pressure on the environment, and management practices balancing the need for agricultural production and environmental health are urgently needed. Key environmental challenges for agricultural systems include the reduction of nutrient losses, the mitigation of greenhouse gas emissions and the preservation of soil biodiversity. Organic farming systems are proposed as environmentally friendly alternative to conventional systems due to their focus on long-term soil quality, but often show lower yields. Long-term field trials are the backbone to assess the impact of farming systems on agronomic and environmental parameters. In this study we present the results from a 42-year-old field trial (DOK trial), located in Therwil, CH on key agronomic and environmental parameters. The trial compares two organic (BIODYN, BIOORG) and two conventional (CONFYM, CONMIN) farming systems with an unfertilized control (NOFERT) and follows a system comparison approach. Farming systems mainly differ in plant protection and fertilization strategy but follow the same tillage strategy and 7-year crop rotation. CONFYM receives the highest external inputs in terms of nutrients and chemical plant protection followed by CONMIN, BIOORG, and BIODYN. Across the five main crops, (grass-clover, wheat, potato, maize, and soybean) organic farming systems maintained yields at ~85% of conventional systems with distinct differences between legume and non-legume crops. Farming systems receiving organic inputs at a rate of 1.4 livestock units per hectare and year stabilized (BIOORG, CONFYM) or even enhanced (BIODYN) soil organic carbon and nitrogen stocks. Yet, soil organic carbon and nitrogen contents evolved slowly and differences became statistically significant only after 22 years. All fertilized farming systems showed a positive nitrogen balance when nitrogen fixation via legumes was included. Still purely mineral fertilized (CONMIN) and unfertilized (NOFERT) systems lost

1978 wurde von Landwirten und Forschenden gemeinsam der berühmte DOK-Versuch in Therwil bei Basel eingerichtet. Dort werden seitdem die Anbausysteme "biologisch-dynamisch" (D), "biologisch-organisch" (O) und "konventionell" (K) miteinander verglichen. Der DOK-Versuch ist damit weltweit der am längsten andauernde Systemvergleichsversuch in der Landwirtschaft. In der aktuellen Podcast-Folge spricht Vanessa Gabel mit den beiden Gästen, Paul Mäder vom FiBL Schweiz und Jochen Mayer von Agroscope, über ihre langjährigen Erfahrungen im DOK-Versuch, der von beiden Institutionen gemeinsam geleitet wird. Die beiden Forscher erklären den Versuchsaufbau und fassen die wichtigsten Erkenntnisse zusammen. Sie berichten darüber, was den Versuch so besonders macht und welche Highlights aber auch welche Schwierigkeiten sie erlebt haben. Sie erzählen, warum der Versuch auch heute noch neue und zum Teil auch unerwartete Ergebnisse hervorbringt und was sie in der Zukunft noch gerne im DOK untersuchen würden.