The use of urease- and nitrification inhibitors (UI, NI) is widely accepted in agriculture. However, robust ammonia (NH3) reduction factors for specific compounds and regions are missing. This study of coordinated field trials evaluated NH3 emissions in Germany across 22 site-year combinations after the application of inhibited urea in winter wheat. Tested fertilizers were urea (U), urea with UI (U+UI), and double-inhibited urea (U+UI+NI). Ammonia emissions were determined using ALPHA samplers, inverse dispersion modeling, and semi-quantitative passive flux samplers. Improving the existing calibrated passive sampling approach, a linear mixed-effects model was developed, accounting for the placement of individual plots within the trial layout. Regardless of the fertilizer treatment, the weather covariates and the clay content significantly influenced the emission factors (EFs, expressed as NH3-N per unit N applied). Average EFs for the treatments were 8.0, 3.1, and 3.8% for U, U+UI, and U+UI+UI, respectively. Compared to U, the emission reduction was affected by inhibitor treatment, soil clay content, and temperature, and was highest under high N-loss scenarios. Average reductions were 61% for U+UI and 52% for U+UI+NI. The results suggest a regionalization of EFs and reduction factors. Grain N yield was significantly influenced by inhibitor treatment and was highest for U+UI with 164 kg N ha-1. U+UI+NI featured the highest absolute yield. With a reduced grain protein concentration, this resulted in a similar grain N yield when compared to U. Combining results of emission and yield measurements, recommendations for specific production targets in winter wheat production are derived.

ABSTRACT Introduction Current recycling measures for closing the phosphorus (P) cycle are limited by the lower fertiliser use efficiencies of recycled products. Increasing P use efficiency (PUE) through maize genotype selection and management may offer a sustainable solution, but the potential of variety choice and its interaction with placed fertilisation for enhancing recycled fertilisers' efficiency remains unclear. Material and Methods Four maize genotypes differing in P efficiency were tested in a pot trial, where microbial P, phosphatase activity, and Olsen‐P were measured and their links to PUE were investigated. Three of these genotypes were examined in a two year field trial comparing two fertiliser types (diammonium phosphate (DAP); struvite) and application methods (broadcast vs. placed). Results Stabil showed higher microbial biomass P and LG_30258 higher phosphatase activity than other varieties. Although not significant, the PUE, expressed as biomass divided by fertilisation, varied among genotypes ( Amaroc 3.4 x higher than Ricardinio ). In the field, no genotype × management interaction was detected and genotypic differences became minimal ( LG_30258 1.4 x higher than Stabil ). Struvite performed comparably to DAP across both years, while fertiliser placement only increased biomass and P offtake in the drier year, 2022. P mobilisation traits could not predict PUE, however, P offtake in the pot and field trial followed the same ranking order as the P mobilization traits. Conclusion This study highlights that the slow‐release fertiliser, struvite, has a comparable fertiliser efficiency than DAP, and fertiliser placement can further enhance PUE in dry seasons, independent of the fertiliser source. Although slight genotypic variance in P mobilisation exists in modern maize varieties and can predict P responsiveness, the influence of genotype choice and management options appeared additive rather than synergistic since genotype x management interaction was not significant. Future research should further explore how to exploit synergies between genotypes, management, and fertilisers.

Definitions of plant nutrient elements, historically anchored in the essentiality criteria of Arnon and Stout, have provided a robust basis for identifying essential mineral nutrients. Yet, they are increasingly challenged by evidence for context-dependent benefits of additional elements and by regulatory demands that tie fertiliser constituents to officially recognized ‘nutrients’. Recent proposals to expand the nutrient concept to include beneficial elements and nutrient effects on quality attributes of harvested products have intensified this debate. This opinion paper evaluates such proposed revisions from a plant-centred perspective. We argue that, while inclusion of elements that improve plant performance under defined conditions is justified, incorporating the broadly used and target-group-dependent concept of ‘quality’ introduces ambiguity and may foster misleading claims, including alleged ‘quality improvements’ driven by stress responses or concentration effects. To improve precision, we propose the term ‘conditionally beneficial elements’ for elements that enhance growth, development or reproduction only in specific species and/or under specified growth conditions. Building on classical essentiality while acknowledging practical experimental constraints, we advance an updated definition for vascular plants, namely: A plant nutrient element, considering natural or managed environments, is essential if deprivation impairs growth, development, or reproduction, or conditionally beneficial if it improves these performance traits in a given species under specified conditions. In both cases, the element must have an established performance-improving role in plant biology. The essential mineral elements comprise the macronutrients N, P, S, K, Ca, and Mg and the micronutrients Fe, Mn, Zn, Cu, Ni, B, Cl, and Mo, whereas Na, Si, Co, Al, and Se are currently classified as conditionally beneficial elements. We argue that this definition supports conceptual clarity in research as well as recognition of nutrient elements in fertiliser legislation, while protecting against unfounded claims.

Introduction This study aimed to investigate the effects of nitrification inhibitors (NIs), specifically DMPP (Dimethyl pyrazole phosphate) and DMPFA (Dimethyl pyrazole fulvic acid), and plant growth-promoting microorganisms (PGPM) on nutrient uptake, allocation, and plant growth in maize under low phosphorus (P) availability. The research questions explored whether NIs enhance P, manganese (Mn), and zinc (Zn) uptake through rhizosphere acidification, alter nutrient partitioning between roots and shoots, and whether DMPFA-PGPM combinations synergistically improve plant growth and nutrient acquisition. Methods Two rhizobox experiments were conducted using silt loam soil with low P content (8.7 mg kg(-1) P-CAL, pH 6.4).Results In the first experiment, maize was subjected to ten treatments, including ammonium (NH4 +) and nitrate (NO3 -) with or without DMPP, DMPFA, and rock phosphate (RP), compared to controls. The second experiment tested five treatments, including NH(4 + )with DMPFA, fulvic acid, and Bacillus atrophaeus (ABi05) as PGPM. Measurements included rhizosphere pH, acid/alkaline phosphatase activity, root exudates, phytohormones, root morphology, plant biomass, and nutrient (P, Mn, Zn, Fe, Ca, Mg, K) concentrations in shoots and roots. Nutrient use efficiencies (PUE, PFPp, NRE) were calculated, and data were analyzed using one-way ANOVA with Fisher's LSD test (p<0.05). In the first experiment, DMPP+RP and DMPFA+RP treatments increased biomass by 31.8% and 38.5%, respectively, compared to the negative control, with total root length rising by up to 169.5% in the positive control (NO3 -+soluble P). Shoot Fe content was 60% higher in NI treatments, with Mn and Zn shoot concentrations increasing by up to 40.4% and 32.8%, respectively, in DMPFA treatments. The rhizosphere pH dropped by 0.5 units in NI treatments, thereby enhancing acid phosphatase activity. In the second experiment, DMPFA and DMPFA+ABi05 increased shoot biomass by 47.5% and 50.7%, respectively, and shoot P content by 45.1% and 62.7%. PUE was 56.2% higher with DMPFA+ABi05, and zeatin concentrations rose by 79.1% compared to controls. Conclusion DMP-based NIs significantly enhance P, Mn, and Zn uptake in maize by acidifying the rhizosphere and increasing nutrient solubility. NIs shift mainly Fe and Mn allocation toward shoots, improving nutrient mobilization. The synergistic effect of DMPFA and PGPM (ABi05) further boosts PUE and Zeatin.

Background With their ability to efficiently acquire P, integrating legumes in phosphorus (P)-inefficient cereal-based rotations may enhance P use efficiency (PUE). However, previous studies on crop rotations have not linked growth gains of successive crops to the stimulation of soil P processes by legumes. Thus, knowledge gaps exist in the relevance of changes in soil induced by legumes for the growth and P nutrition of successive crops and the PUE of the entire crop rotation. Aim This study aims to address the abovementioned points by testing four short-term crop sequences (alfalfa (Medicago sativa)/maize (Zea mays cv. Johaninio), faba bean (Vicia faba cv. Augusta)/maize, white lupin (Lupinus albus cv. C & eacute;lina)/maize, and maize/maize) under P limitation and with the application of P fertilizers differing in their P availability (rock phosphate, struvite, and triple superphosphate) in a pot trial. Results Acid and alkaline phosphomonoesterase activity were strongly and persistently stimulated by white lupin and faba bean (2 & times; for acid and 1.22-1.23 & times; for alkaline phosphomonoesterase activity). However, even under P limitation, biomass and P offtake of successive maize did not benefit from the previous cultivation of legumes. In contrast, lupin strongly inhibited the growth of successive maize (0.4 & times; aboveground biomass of maize after maize), although lupin increased calcium-acetate extractable P. None of the legume-based early growth sequences could compete with maize monoculture regarding PUE due to the low aboveground biomass of legumes compared to pre-crop maize. Conclusion This study questions the one-sided positive portrayal of legumes in crop rotations for improving the P nutrition of succeeding maize and can guide the design of future field experiments.

Understanding how horticultural crops coordinate multiple phosphorus (P) acquisition pathways is essential for improving nutrient management and reducing excessive fertilizer inputs. However, the dominant P foraging strategies of pepper (Capsicum annuum L.) and their relationships with root traits and rhizosphere processes remain poorly understood. A two-year field experiment with five P fertilization rates combined with a hydroponic experiment was conducted to investigate yield responses, root morphology, rhizosphere processes, and arbuscular mycorrhizal fungi (AMF) colonization under varying P supply. Pepper yield increased with P fertilization and plateaued at 65 kg P ha−1, corresponding to a critical soil Olsen-P threshold of 24.4 mg kg−1 that ensured 87.5

ABSTRACTBackgroundLoss of gaseous reactive nitrogen in the form of aerosols may impact human health, and its deposition leads to eutrophication and acidification of natural ecosystems. In order to reduce ammonia (NH3) emissions, which are a main pathway of nitrogen loss to the environment, accurate monitoring and understanding of the factors involved is required.AimsAs information on the absorption of NH3 by wheat plants in central Europe is scarce, we conducted a field experiment to quantify NH3 absorption by a winter wheat canopy in May and June with each two emission scenarios (5 and 12 kg NH3‐N ha−1).MethodsTo induce NH3 emissions, a 15N enriched ammonium sulfate solution (pH 9) was applied in trays between the wheat rows.ResultsAbsorption of the volatilized NH3 of the aboveground plant biomass ranged between 23 and 181 mg NH3‐N m−2 (corresponding to 14.8% and 20.0% of the emitted NH3) and was significantly higher during the first sampling in May, when compared to the second sampling in June. A higher emission led to a higher absolute amount absorbed.ConclusionsThe results indicate that wheat will indeed absorb significant amounts of NH3 emitted at ground level. They will be useful for further improving NH3 emission factors and the understanding of the NH3 emission pathway.

Ammonia (NH3) emissions in Germany originate mainly from agricultural activities, leading to numerous negative impacts on ecosystems, human health and environment. To reduce NH3 emissions, the addition of urease inhibitors (UI) to synthetic urea fertilizer is proposed and implemented in practical agriculture. Nevertheless, there are still uncertainties about the reduction potential of UIs under varying environmental conditions. In this incubation study, we examined the influence of soil water content (low: 10%, medium: 17.5%, high: 25% w/w) and rainfall (1, 5, 10 mm) on NH3 emissions after the application of urea fertilizer. Ammonia was trapped by sulfuric acid in an incubation setup for three weeks after fertilizer application. Daily cumulative emissions were fitted to a logistic growth function. Cumulative emissions of the fertilized treatments, ranged between 1.6 and 24.9% of the applied N and were highest at the medium soil water content. Low soil moisture at application hindered granule dissolution, resulting in emissions of 8.4% across all fertilizers. High soil water content led to low emissions (7.2%) due to a faster diffusion of urea into the soil. The results indicate, that UI always reduced NH3 emissions with a mean reduction of 73.3% over all soil moisture and rain treatments. Under conditions favoring high NH3 emissions, the emission of a double inhibited urea fertilizer (UI and nitrification inhibitor) was higher when compared to fertilizer only with UI, but still lower than from untreated urea. Rainfall linearly decreased cumulative emissions, independent of fertilizer choice by 4.7% per mm of rain.

Biostimulants (Bio-effectors, BEs) comprise plant growth-promoting microorganisms and active natural substances that promote plant nutrient-acquisition, stress resilience, growth, crop quality and yield. Unfortunately, the effectiveness of BEs, particularly under field conditions, appears highly variable and poorly quantified. Using random model meta-analyses tools, we summarize the effects of 107 BE treatments on the performance of major crops, mainly conducted within the EU-funded project BIOFECTOR with a focus on phosphorus (P) nutrition, over five years. Our analyses comprised 94 controlled pot and 47 field experiments under different geoclimatic conditions, with variable stress levels across European countries and Israel. The results show an average growth/yield increase by 9.3% (n=945), with substantial differences between crops (tomato > maize > wheat) and growth conditions (controlled nursery + field (Seed germination and nursery under controlled conditions and young plants transplanted to the field) > controlled > field). Average crop growth responses were independent of BE type, P fertilizer type, soil pH and plant-available soil P (water-P, Olsen-P or Calcium acetate lactate-P). BE effectiveness profited from manure and other organic fertilizers, increasing soil pH and presence of abiotic stresses (cold, drought/heat or salinity). Systematic meta-studies based on published literature commonly face the inherent problem of publication bias where the most suspected form is the selective publication of statistically significant results. In this meta-analysis, however, the results obtained from all experiments within the project are included. Therefore, it is free of publication bias. In contrast to reviews of published literature, our unique study design is based on a common standardized protocol which applies to all experiments conducted within the project to reduce sources of variability. Based on data of crop growth, yield and P acquisition, we conclude that application of BEs can save fertilizer resources in the future, but the efficiency of BE application depends on cropping systems and environments.

Despite the essential role of nitrogen fertilizers in achieving high crop yields, current application practices often exhibit low efficiency. Optimizing nitrogen (N) fertilization in agriculture is, therefore, critical for enhancing crop productivity while ensuring sustainable food production. This study investigates the effects of nitrification inhibitors (Nis) such as Dimethyl Pyrazole Phosphate (DMPP) and Dimethyl Pyrazole Fulvic Acid (DMPFA), plant growth-promoting bacteria inoculation, and phosphorus (P) application on the soil-plant-microbe system in maize. DMPFA is an organic nitrification inhibitor that combines DMP and fulvic acid for the benefits of both compounds as a chelator. A comprehensive rhizobox experiment was conducted, employing varying levels of P, inoculant types, and Nis, to analyze the influence of these factors on various soil properties, maize fitness, and phenotypic traits, including root architecture and exudate profile. Additionally, the experiment examined the effects of treatments on the bacterial and fungal communities within the rhizosphere and maize roots. Our results showed that the use of Nis improved plant nutrition and biomass. For example, the use of DMPFA as a nitrification inhibitor significantly improved phosphorus use efficiency by up to 29%, increased P content to 37%, and raised P concentration in the shoot by 26%, compared to traditional ammonium treatments. The microbial communities inhabiting maize rhizosphere and roots were also highly influenced by the different treatments. Among them, the N treatment was the major driver in shaping bacterial and fungal communities in both plant compartments. Notably, Nis reduced significantly the abundance of bacterial groups involved in the nitrification process. Moreover, we observed that each experimental treatment employed in this investigation could select, promote, or reduce specific groups of beneficial or detrimental soil microorganisms. Overall, our results highlight the intricate interplay between soil amendments, microbial communities, and plant nutrient dynamics, suggesting that Nis, particularly DMPFA, could be pivotal in bolstering agricultural sustainability by optimizing nutrient utilization.

Background: Placed starter fertilization, a well-established fertilization practice in agriculture, aims to increase fertilizer use efficiency and yield. So far, numerous studies have proven positive effect on yields. However, the impact on nutrient use efficiency and nutrient uptake was not investigated profoundly. Additionally, diverse unidentified edaphic and environmental factors, and fertilization strategies cause a high uncertainty for the outcome under field conditions. Objectives: The aim of this study was to quantify the impact of a placed starter fertilization on yield, N and P uptake as well as N and P use efficiency. Thereby, the importance of influencing environmental factors and management strategies and the magnitude of their impact should be clarified. Methods: We performed a network meta-analysis including 1158 observations from 57 peer-reviewed studies and provided a holistic investigation on the effect of placed starter fertilization on yield, nutrient use efficiencies, and aboveground nutrient contents compared to fertilizing without starter fertilization. Results: This study revealed that placed starter fertilization significantly increased yield by 9.4 %. Especially in warm, arid climates as well as in warm, hyper-humid climates the fertilizer use efficiency gain was most pronounced. While N uptake and N use efficiency could not benefit significantly from a placed starter fertilization, P uptake and P use efficiency were both enhanced. In the future, combining N and P and using ammonium-based fertilizers can guarantee the effectiveness of a placed starter fertilization. Conclusions: In summary, placed starter fertilization is a potent strategy to increase yield and improve P use efficiency and P uptake. When applied in the right climate, with the right dosage and N compound, additional advantages of a placed starter fertilization can be exploited. Implications: The current study not only deepens our understanding of the connection of fertilization methods and agronomic performance, but also provides a guideline for improving the efficiency of placed starter fertilization.

Novel recycled fertilizers could help close environmental nutrient cycles in the circular economy. To better understand their performance and residual value, commercially available biobased nitrogen (N) and phosphorus (P) fertilizers (BBFs) were tested in a two-year crop cycle of winter wheat and ryegrass. The N fertilizer replacement value of N-BBFs ranged from 47 to 80% in the main crop. Not all BBFs led to a similarly high N concentration as the mineral reference in the wheat straw. However, full and early fertilization with incorporation could make the fertilizing effect of N-BBFs more reliable. The P fertilizer replacement value ranged between 105 and 161% for the crop cycle. We assume that the N contained in biobased phosphorus fertilizers can be seen as unproblematic for losses during winter and can serve as a starter fertilizer already present in the soil for the succeeding crop in spring. In general, biobased P fertilizers had a higher residual value than biobased N fertilizers. However, these residual values were comparable to those of mineral fertilizer references. While P-BBFs proved to be a sustainable and reliable nutrient source for a crop cycle, the N-BBFs used as the main crop fertilizer were found to be more prone to environmental influences.

Context or problem: Substituting mineral fertilizers with novel biobased fertilizers (BBFs) produced from various organic waste and side streams could contribute to a reduction in the environmental and climate impacts of fertilizer production and use and the recycling of otherwise potentially wasted nutrients. For the substitution to be beneficial for farmers, the environment, and food security, the BBFs need to be effective, reliable and safe. However, the agronomic performance of novel, nitrogen (N) rich BBFs has not yet been well studied. Objectives or research question: The main objective of this study was to determine the agronomic efficiency of N in a relevant range of commercially available BBFs. We hypothesised that they can function as effective substitutes for mineral N fertilizers, independent of the agricultural and geographic settings. Methods: Field trials (fully randomized block design) were conducted at four field sites across Europe covering different climates, soil types, and crop sequences. In total 18 BBFs were tested, 7 of which were common BBFs tested at all sites, while the other 11 (2 -3 per site) were local BBFs at individual sites. The design included 4 -5 increasing levels of mineral N reference. Trials with BBF application were conducted over 2 years, and the agronomic performance (crop yield and N offtake) was determined to estimate 1 st year mineral N fertilizer replacement value (NFRV) in both years, while residual NFRV was estimated only in the 2 nd year. Results: The BBFs showed an average N fertilizer replacement value (NFRV) of 70 % across sites and years, with variations in the agronomic performance between the trial sites and years. Compared with the mineral N fertilizer reference applied at the same total N level, no consistent ranking of BBF and no significant differences in yields were found. The BBFs tended to have a higher NFRV when incorporated compared to surface application. Of the 18 BBFs tested, 8 had a NFRV above 75 %, 6 were in the range 60 -75 % and 4 were in the low range of 10 -60 %. The residual effect of BBFs in the year after application was not significantly higher for any of the BBFs than that of the mineral N fertilizer. Conclusions: Generally, the BBFs performed similar to the mineral reference applied at the same total N level. The performance of BBFs was not significantly affected by climate or soil type. The BBFs appeared to have higher agronomic performance when incorporated into the soil compared to surface application. The second year residual effect of BBF was not significantly higher than that of the mineral reference fertilizer. Implications or significance: In general, most of the investigated BBFs can be considered reasonably effective substitutes for mineral N fertilizers. The results suggest that soil incorporation of BBFs will result in better agronomic performance than surface application.

IntroductionPhosphorus 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. MethodsWe 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 discussionBSs 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.

Introduction:The production of high-quality food for the growing world population on the one hand and the reduction of chemical-synthetic pesticides on the other hand represents a major challenge for agriculture worldwide. The effectiveness of a combination of microbial and non-microbial biostimulants (BSs) with various nitrogen (N) forms in pathogen defense is discussed as a promising, but still poorly understood bio-based alternative for crop protection. Methods:For this reason, nitrate and stabilized ammonium fertilizer both combined with a consortium of Pseudomonas brassicacearum, Bacillus amyloliquefaciens, and Trichoderma harzianum as soil treatment or with a mixture of seaweed extract (Ascophyllum nodosum) together with chitosan-amended micronutrient fertilizer as foliar spray application were compared under controlled greenhouse conditions. Furthermore, a combination of microbial and different non-microbial BSs (seaweed extracts + chitosan) and micronutrients with nitrate or with stabilized ammonium fertilizer was tested under field conditions to improve nutrient availability, promote plant growth, and suppress Zymoseptoria tritici (Zt) in winter wheat. Results and discussion:While plant-protective effects against Zt by the microbial consortium application could be observed particularly under ammonium fertilization, the application of seaweed extract-chitosan mixture expressed plant defense against Zt more strongly under nitrate fertilization. In the field trial, the combination of microbial consortium with the seaweed extract-chitosan mixture together with micronutrients zinc (Zn) and manganese (Mn) showed positive effects against Zt under ammonium fertilization, associated with increased levels of defense metabolites. Furthermore, the additional input of Zn and copper (Cu) from the chitosan application improved the micronutrient status by minimizing the risk of Zn and Cu deficiency under controlled and field conditions. The use of BSs and the inoculation of Zt did not show any effects on plant growth and yield neither under controlled greenhouse conditions nor in the field. Summarized, microbial and non-microbial BSs separately applied or even combined together as one treatment did not influence plant growth or yield but made a positive contribution to an N form-dependent promotion of pathogen defense.

Soil organic phosphorus (Porg) is of interest for plant nutrition because it can comprise between 20 and 80

Miscanthus × giganteus may play an important role in replacing fossil energy

BackgroundOrganic farmers frequently report sufficient yield levels despite low or even very low soil phosphorous (P) contents questioning the applicability of widely used laboratory methods for soil P testing for organic farming.AimsThe aim of this study was to compare the validity of a broad range of different soil extraction methods on soils under organic management from South West Germany and to test the correlation of the measured soil P concentration with plant offtake.MethodsTwenty-two soil samples of eight different organic farms were extracted with different solutions: (1) water, (2) CAL, (3) Olsen, (4) Mehlich 3, (5) Bray P1, (6) Bray P2, (7) NaOH+Na2EDTA, and (8) total P. The results were then correlated with above ground plant P.ResultsSpearman's rank correlation coefficient (rs) of correlations between above ground plant P and extractable soil P (Water-P, CAL-P, and Olsen-P [+active charcoal {+AC}]) determined with ICP-OES were strong (0.94, 0.90, and 0.93, respectively). Among the tested methods, above ground plant P showed a strong correlation with CAL-P as detected by ICP-OES (rs = 0.90) and colorimetry (rs = 0.91). The comparison of CAL-P data provided by farmers and CAL-P analyzed during this research showed discrepancies between the results.ConclusionsThe results of this study indicate that the CAL method can be used in organic farming despite a low extraction of organic P (Porg). Furthermore, it is recommended for farmers to take soil samples for analyses regularly and interpret changes in P in the long-term instead of interpreting individual samples.

0.98 Mg·ha−1·yr−1 Corg accumulation under miscanthus over 26 years. ● Corg accumulation under miscanthus continued even up to 26 years. ● Reintegration of a miscanthus site into a crop rotation induced decreasing C stocks at first after 6 years. Miscanthus× giganteus may play an important role in replacing fossil energy resources by bio-based alternatives. One further advantage of miscanthus production is the generally high soil organic carbon (Corg) enrichment in soils. Due to declining yields, miscanthus stocks are commonly reintegrated into crop rotation after approximately 20 years. Currently there is only few information, whether these high amounts of Corg can be conserved while intensifying soil tillage and crop management after reintegration. Therefore, we monitored Corg stocks in a control with more than 20 years of continuous miscanthus and in a treatment with reintegration of a 20-years old miscanthus stock into an organic crop rotation. Based on δ13C soil values, we calculated an annual Corg enrichment of 0.98 Mg·ha−1·yr−1 C under miscanthus. More than 95% of the miscanthus-C was determined in the upper 0.25 m of soil. Continuing miscanthus cultivation did not affect yields during the first five extension years and Corg stocks increased further. Following reintegration, Corg stocks remained constant during five years, which was mainly attributed to the humification and/or stabilization of high amounts of destroyed roots and rhizomes. A significant decrease in Corg (−5.7 Mg·ha−1 C) compared to the continuing miscanthus cultivation was at first measured six years after reintegration into crop rotation, underlining the need of long-term investigations. Our data also show, that miscanthus production cycles can be extended in our region, and that sowing of the alfalfa grass mixture after rhizome/root destruction was efficient in preserving Corg stocks for at least first five years after reintegration.

BackgroundFertilization with organic waste compost can close the nutrient cycles between urban and rural environments. However, its effect on yield and soil fertility must be investigated. AimThis study investigated the long-term effect of compost on soil nutrient and potentially toxic elements (PTEs) concentration, nutrient budgets, and nitrogen (N) mineralization and efficiency. MethodsAfter 21 years of annual compost application (100/400 kg N ha(-1) year(-1) [100BC/400BC]) alone and combined with mineral fertilization, soil was analyzed for pH, organic carbon (SOC), nutrient (total N and P, N-min, extractable CAL-P, CAL-K, and Mg), and PTE (Cu, Ni, Zn) concentrations. Yields were recorded and nutrient/PTE budgets and apparent net mineralization (ANM, only 2019) were calculated. ResultsN efficiency was the highest in maize and for mineral fertilization. Compost application led to lower N efficiencies, but increased ANM, SOC, pH, and soil N, and surpluses of N, P, and all PTEs. Higher PTE concentrations were only found in 400BC for Cu. Nutrient budgets correlated with soil nutrient concentration. A surplus of 16.1 kg P ha(-1) year(-1) and 19.5 kg K ha(-1) year(-1) resulted in 1 mg kg(-1) increase in CAL-P and CAL-K over 21 years. ConclusionCompost application supplies nutrients to crops with a minor risk of soil-accumulation of PTEs. However, the nutrient stoichiometry provided by compost does not match crop offtakes causing imbalances. Synchronization of compost N mineralization and plant N demand does not match and limits the yield effect. In winter wheat only 65-70% of N mineralization occurred during the growth period.