Climate effects of recycled fertilizers and biochar: emissions of nitrous oxide, methane and ammonia in a field experiment

Background Nitrogen (N) fertilizers are essential for crop production. Farmyard manure and slurry traditionally constitute about half of the total N inputs into crop production in Switzerland. Recycled fertilizers such as biogas slurry, liquid digestates and compost enable simultaneous energy production and closing of nutrient cycles. There is evidence that recycled fertilizers can help to increase N use efficiencies and to improve N supply in organic farming. Biochar amendment has shown a potential to mitigate soil greenhouse gas (GHG) emissions, in particular nitrous oxide (N2O) emissions. Here, we combine one of the liquid recycled fertilizer treatments with biochar. In a 2.5-years on-farm experiment, we quantify GHG emissions and further gaseous N-losses via ammonia (NH3) emissions

Rezyklierte Phosphordünger - was die Branche davon hält

Phosphor in Abwässern muss ab 2026 rückgewonnen werden. Was halten Landwirte und andere Düngeexperten davon

Valeur de référence pourl'humus des terres assolées - Etablissement d’une valeur de référence applicable à la teneur en matière organique des sols minéraux agricole

La présente brochure s’adresseaux organes exécutifs de protection des sols et aux professionnels avertis. Elle présente les possibilités d’établir une valeur de référence applicable à la teneur en matière organique des sols minéraux agricoles. Elle intègre la réglementation suisse ainsi que les acquiset les avis d'un atelier réunissant des acteurs de l'agriculture, de la protection de l'environnement et de l’exécution cantonale, qui s'est tenu le 16novembre 201

Tracing the fate of 15N-labelled animal manure in the environment

Background • Nitrate leaching threatens both the environment and drinking water quality • Switzerland ca. 380,000 ha with > 25 mg nitrate/L in groundwater (quality criteria for drinking water) [1]; the Gäu region (Canton Solothurn) is especially vulnerable • Organic fertilizers (slurry, farmyard manure, etc.) might entail considerably increased leaching risks due to variable nitrogen (N) content and availability • Aim: increase N use efficiency, simultaneously reduce leachin

Einfluss unterschiedlicher Bewirtschaftungsverfahren auf P-Formen und P-Dynamik im Boden

The impact of cropping systems on soil phosphorus (P) forms and P dynamics was studied. The systems were a biodynamic (DYN), a bioorganic (BIO), a conventional (CON), a stockless system (MIN) and an unfertilized control (NON). These cropping systems are part of the DOK field trial in Therwil near Basel. The systems differed in fertilization and plant protection. The P budgets over 30 years were negative except for CON and increased in the order: NON < DYN < ORG < MIN < CON. A sequential P extraction scheme was used to characterize the P forms in soil samples from 2007 and 1977 (before the start of the trial). Labile inorganic P (Pi) forms differed significantly between cropping systems. Organic P forms (Po) and stable Pi forms were not affected by the cropping systems apart from Po in concentrated HCl extract. The comparison between P forms in the soils of 2007 and 1977 revealed depletion in labile Pi forms in all systems. The changes were related to the P budget. Po changes were small and thus most of Po appears to be strongly stabilized in the soil

Soil quality: a critical review and a look into the future

Soils are complex systems with physical, chemical and biological properties which depend on pedo-climatic conditions as well as previous and current land use. Soil status and use potential is frequently assessed from plot to national scales, using either visual examination or laboratory analysis of samples. However, the choice of relevant soil attributes and interpretation of measurements are not straightforward. In this presentation, we review soil quality and related concepts, in terms of definition, assessment approaches, and indicator selection and interpretation. We identify the most frequently used soil quality indicators under agricultural land use. We also consider novel indicators as evaluated using 10 European long-term field experiments. Explicit evaluation of soil quality with respect to specific soil threats, soil functions and ecosystem services is rare, and few approaches provide clear interpretation schemes of measured indicator values. This limits their adoption by land managers as well as policy. The development of a soil quality assessment procedure that is scientifically sound and supports management and policy decisions that account for the multi-functionality of soil requires the involvement of the pertinent actors, stakeholders and end-users. Several interactive tools that are currently being developed will be shown and can be tested during the field trip of the conference

Field‑scale monitoring of nitrate leaching in agriculture: assessment of three methods

Deterioration of groundwater quality due to nitrate loss from intensive agricultural systems can only be mitigated if methods for in-situ monitoring of nitrate leaching under active farmers’ fields are available. In this study, three methods were used in parallel to evaluate their spatial and temporal differences, namely ion-exchange resin-based Self-Integrating Accumulators (SIA), soil coring for extraction of mineral N (Nmin) from 0 to 90 cm in Mid-October (pre-winter) and Mid-February (post-winter), and Suction Cups (SCs) complemented by a HYDRUS 1D model. The monitoring, conducted from 2017 to 2020 in the Gäu Valley in the Swiss Central Plateau, covered four agricultural fields. The crop rotations included grass-clover leys, canola, silage maize and winter cereals. The monthly resolution of SC samples allowed identifying a seasonal pattern, with a nitrate concentration build-up during autumn and peaks in winter, caused by elevated water percolation to deeper soil layers in this period. Using simulated water percolation values, SC concentrations were converted into fluxes. SCs sampled 30% less N-losses on average compared to SIA, which collect also the wide macropore and preferential flows. The difference between Nmin content in autumn and spring was greater than nitrate leaching measured with either SIA or SCs. This observation indicates that autumn Nmin was depleted not only by leaching but also by plant and microbial N uptake and gaseous losses. The positive correlation between autumn Nmin content and leaching fluxes determined by either SCs or SIA suggests autumn Nmin as a useful relative but not absolute indicator for nitrate leaching. In conclusion, all three monitoring techniques are suited to indicate N leaching but represent different transport and cycling processes and vary in spatio-temporal resolution. The choice of monitoring method mainly depends (1) on the project’s goals and financial budget and (2) on the soil conditions. Long-term data, and especially the combination of methods, increase process understanding and generate knowledge beyond a pure methodological comparison

Ammonia emissions from cattle slurry and digestates

The recycling of organic waste in biogas plants is proposed as a measure to close nutrient cycles and possibly reduce nitrogen losses such as nitrous oxide emissions and nitrate leaching. Ammonia volatilization after fertilizer spreading is yet another nitrogen loss pathway which is often understudied and not yet fully understood but the knowledge is needed in order to optimize fertilizer management. We therefore aimed to quantify the volatilization of ammonia after the trail-hose application of digestates compared to cattle slurry. We hypothesize that digestates have larger and longer lasting nitrogen losses via ammonia volatilization due to higher NH4+ contents and pH values compared to fresh manure. In this project, digested and un-digested organic fertilizers were applied twice per year in a 2.5-years field experiment with three consecutive arable crops (maize, winter wheat and winter barley) under organic farming. We used Automated Low Cost Impinger Systems to measure ammonia emissions after fertilizer application. The emissions were then modeled using the backwards Langrangian stochastic dispersal model with respect to wind conditions. A preliminary presentation of the data indicates that ammonia emissions from the cattle slurry, slurry-based digestate, and industrial digestate are alternately higher or lower. In 2018, emissions from cattle slurry tended to be lower than those from slurry-based digestate and industrial digestate, while in 2019 and 2020 all three liquid organic fertilizers had similar emissions. In the measurement period after the second fertilizer application in 2018, which took place at the end of May, conspicuously high emissions were measured. This can be explained by the high temperatures during this period. Adaptive strategies in fertilizer management should thus consider reduced inputs of organic fertilizers during warm periods

Reliance on Biological Nitrogen Fixation Depletes Soil Phosphorus and Potassium Reserves

Limited nutrient availability is one of the major challenges in organic farming. Little is known about nutrient budgets of organic farms, the underlying factors or effects on soil fertility. We therefore assessed farm gate nutrient budgets for nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg) and sulfur (S) of 20 organic farms in Germany and analyzed their soil nutri-ent status. In average, the budgets showed a surplus of N (19 kg ha−1), K (5 kg ha−1), S (12 kg ha−1), and Mg (7 kg ha−1), and a deficit of P (−3 kg ha−1). There was, however, high variability between farms (e.g. standard deviation up to ± 36 kg N ha−1), which was mainly explained by different degrees of reliance on biological N fixation (BNF) as N source. When farms obtained more than 60% of their N input through BNF, they had deficits of P (mean −8 kg P ha−1) and K (mean −18 kg K ha−1). Nutrient status of most soils was within the ad-vised corridor, but for P, K and Mg, 10–15% of fields were lower and 45–63% were higher than advised. Extractable soil nutrient contents did not correlate with the nutrient budgets, inputs or outputs. Only extractable soil P increased with increasing P inputs and outputs. Fur-thermore, a decrease in extractable soil P was detected with a prolonged history of organic farming, indicating a risk of soil P mining in organic farming systems. In conclusion, the study revealed nutrient imbalances in organic farming and pointed to P and K scarcity as a major challenge for organic farms with high reliance on BNF in the long term

Assessing the phosphorus demand in European agricultural soils based on the Olsen method

Overcoming the consequences of future scarcity of P is crucial to ensure agriculture sustainability. This requires decision-making processes depending on data on the P status of agricultural fields, commonly conducted with soil P tests (SPTs), and efficient use of the resource on a societal scale following a circular economy approach. All this will decrease the P losses and the subsequent environmental impact. However, SPTs are not universal and, even for a given SPT, the definition of threshold values for fertilizer response is not accurate. This work aimed to define models to predict Olsen P threshold values, allowing the identification of P-responsive sites at the European scale as a basis for more accurate and sustainable P fertilization schemes based on a circular economy approach. To this end, a data set was compiled based on a literature review that describes the Olsen P threshold values for different crops under field conditions. Subsequently, an analysis of potential P fertilizer requirements was performed on agricultural soils of the European Union (EU) using the data set of the LUCAS project and how this need can be covered with a circular economy approach. Environmental factors were more relevant than crops to explain the variation in threshold values. A regression model involving soil pH and clay content and annual average rainfall as independent variables explained 61% of the variance in Olsen P threshold values. When soil pH and clay content were the only explanatory variables, the explained variance was 49%. This reveals the need to take into account factors related to P buffer and sorption capacity to estimate accurate threshold values. We detected that only 27.8% of EU cropland soils and 42.7% of grassland soils were P-responsive. We can conclude that a more precise allocation of the resource is possible in P-responsive sites and also that most of the European demand for P could be covered by recycling P from manure, wastewater, and municipal solid waste