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Optimal manure management is required to ensure efficient nutrient supply to farmland and to avoid adverse environmental impacts. Accordingly, ammonia (NH3) emissions associated with different slurry application techniques were investigated in grassland trials under different soil and weather conditions across Germany. Cattle slurry was applied in two dressings, early in spring and after the first silage cut, with a target amount of 170 kg N ha−1. The application treatments comprised: trailing shoe (TS), acidified slurry applied with trailing shoe (TS + A), open slot injection (SI), and slurry treated with a nitrification inhibitor (NI) applied by slot injection (SI + NI). In addition, slurry application techniques were compared with a non-N-fertilized control and a mineral fertilizer treatment (calcium ammonium nitrate, CAN). NH3 measurements followed each N application event. NH3 losses were equivalent to 1–39% of total ammoniacal nitrogen (TAN) applied. The average NH3 mitigation potential of the different slurry application techniques compared to TS was 45.7 ± 7, 21.2 ± 6.2 and 13.7 ± 8.2% for TS + A, SI and SI + NI, respectively. The use of nitrification inhibitor with slot injected slurry did not increase NH3 losses relative to TS (p > 0.05). Mean apparent N use efficiency was two times higher for CAN (49%) than the slurry treatments (24%) but was comparable between SI + NI and CAN in five out of the eight cases. Our results indicate that mean TAN related NH3 emissions of tested treatments (3.3, 22.6, 12.2, 17.8 and 19.3% for CAN, TS, TS + A, SI and SI + NI, respectively) were generally lower than described in previous studies. Moreover, the results suggested possible increases in NH3 mitigation and N use efficiency when cattle slurry is applied with acidification or injection techniques. We found no evidence that NI addition to slot injected slurry, a treatment discussed as a measure to reduce N2O emission and nitrate leaching, changed NH3 emission.

Aims This study aimed to investigate how efficiently assimilated carbon (C) is incorporated in plant biomass at an intensively managed old permanent grassland, how C is partitioned between shoots and roots and what are the implications for C sequestration. Methods Using the eddy covariance technique, the atmosphere-biosphere exchange of CO2 was measured for two years at a sandy grassland site in northern Germany. In addition to aboveground net primary production (ANPP), belowground NPP (BNPP) was observed using the ingrowth core method. Results The grassland showed a high productivity in terms of biomass yield (14.8 Mg dry matter ha−1 yr−1) and net CO2 uptake (−2.82 Mg CO2-C ha−1 yr−1). Photosynthetically assimilated C was converted to biomass with a high carbon use efficiency (CUE) of 71% during the growing season. However, a comparably low fraction of 17% of NPP was allocated to roots (fBNPP). Consequently, the main fraction of NPP was removed during harvest, turning the site into a net source of 0.29 Mg C ha−1 yr−1. Conclusions Our study showed the flexibility of grass root growth patterns in response to alterations in resource availability. We conclude that highly fertilized grasslands can lose their ability for C sequestration due to low belowground C allocation.

Agricultural production is predicted to double during the next century. To ensure food security in response to global population growth is a challenge and will require strategies that mitigate associated environmental damage in ways consistent with United Nation’s Sustainable Development Goals. One possible approach is to utilize organic fertilizers from marine sources to improve soil structure by enhancing activities of soil organisms and restoring essential plant nutrients to the soil. Here we identify opportunities to develop organic fertilizers from two types of materials of marine origin: seagrass wrack and jellyfish biomass. Seagrass wrack often occurs as undesirable waste material on beaches. In many coastal areas around the world jellyfish bloom presents a nuisance because of negative impacts on marine ecosystem productivity. Several investigations have reported that organic fertilizers produced from seagrass and jellyfish could enhance coastal ecosystem services by reducing pollution, and by improving soil health and quality. Recent research indicates that seagrass litter improves soil water holding capacity and the nutritional value of crops; moreover, it can be used as multi-functional fertilizer, due to its content of valuable macro- and microelements. The application of jellyfish fertilizer increases soil contents of organic matter, nitrogen, phosphorus and potassium and enhances the growth and survival of seedlings significantly. In this overview we describe novel approaches regarding the utilization of seagrass and jellyfish as sources of fertilizer, and experimental studies on the influences of marine organic fertilizers on soil restoration, and implications for coastal management.

Land-use change (LUC) and conventional tillage (CT) result in the reduction of the high soil organic carbon (SOC) stocks stored in grassland ecosystems during their conversion and renovation, contributing to global warming. While plenty studies show the use of no-tillage (NT) as a promising option to increase the topsoil SOC stocks of arable lands, its potential to conserve SOC during grassland conversion and renovation events has been poorly investigated. Further, the effects of LUC and tillage methods on the SOC dynamics have been limited to the topsoil by most studies, thus overlooking their impact on the subsoil where significant amounts of SOC are stored, and changes in vegetation and residue distribution can negatively affect these. In this study, a 10-year-old grassland was converted to continuous silage maize (CM) using NT (NT-CM) and CT (CT-CM), and renovated using NT (NT-GR), while some part remained undisturbed as a control (GC). The systems were either non-fertilized (N0) or fertilized according to a demand of 180 and 380 kg N ha−1 yr−1 (N1) in the silage maize and grassland systems, respectively. SOC stocks were measured annually and annual SOC changes (ΔSOC, in Mg C ha−1 yr−1) were calculated for different soil layers (0–30, 30–60 and 60–90 cm) and across the whole profile (0–90 cm) over a 6-year period (2014–2020). Annual soil carbon inputs (Ci) via plant residues were quantified and related to ΔSOC. Results showed that cropping systems significantly affected SOC dynamics over time. At 0–30 cm, SOC stocks were significantly reduced after conversion using both tillage methods, however, 44 % lower annual losses were obtained in NT-CM (−1.5 Mg C ha−1 yr−1) compared to CT-CM (−2.7 Mg C ha−1 yr−1). Conversely, SOC stocks remained unchanged after NT-GR same as the GC. In the subsoil, SOC stocks increased under GC (1.1 Mg C ha−1 yr−1) and remained unchanged in the other systems. Across the whole profile, SOC stocks increased in GC, remained stable in NT-GR, and decreased in NT-CM and CT-CM with mean annual change rates of 1.3, −0.1, −1.9 and −3.4 Mg C ha−1 yr−1, respectively. The differences in ΔSOC between the unploughed systems (NT-GR, NT-CM and GC) were strongly related to the annual soil Ci from plant residues in the topsoil. Our findings highlight the great potential of NT to slow down the annual SOC losses after grassland conversion or renovation, and that C sequestration can occur in the subsoil of permanent grasslands when the topsoil C is already saturated. This strengthens the need to consider the SOC changes occurring in the whole profile after a LUC event.

High doses of nitrogen (N) fertiliser input on permanent pastures are crucial in terms of N surplus and N losses. Quantitative analyses of the response of plant functional traits (PFT) driving crop growth rate (CGR) under low N input are lacking in frequently defoliated pastures. This study aimed to understand the significance of PFTs for productivity and N uptake in permanent grasslands by measuring dynamics in tiller density (TD), tiller weight (TW), leaf weight ratio (LWR), leaf area index (LAI), specific leaf area (SLA), as well as leaf N content per unit mass (LNCm) and per unit area (LNCa) in perennial ryegrass (Lolium perenne)-dominated pastures, in a simulated rotational grazing approach over two consecutive growing seasons. Annual N application rates were 0, 140 and 280 kg N ha−1. The phenological development of perennial ryegrass was the main driver of CGR, N uptake and most PFTs. The effect of N application rate on PFTs varied during the season. N application rate showed the greatest effect on TD, LAI and, to a lesser extent, on SLA and LNCm. The results of this study highlight the importance of TD and its role in driving CGR and N uptake in frequently defoliated permanent pastures.

The supply of nutrients for agricultural production faces enormous challenges as food security and sustainability goals have to be ensured. Processing of marine biomass has high potential to provide nutrients for agricultural purposes in coastal areas. One underexplored resource are jellyfish, which occur as blooms and by-catch of the fishing industry. In this context, a pot experiment investigated the effects of jellyfish as a fertilizer on biomass accumulation of annual ryegrass (Lolium multiflorum), and its effect on the important greenhouse gas N2O as a sustainability indicator of novel fertilizers. Dried and ground jellyfish was applied [3 species: Aurelia aurita (AA), Cyanea capillata (CC), Periphylla periphylla (PP)] and compared with an unfertilized and a mineral fertilized (calcium-ammonium-nitrate, CAN) treatment. Dried jellyfish and CAN were applied at equal N rates of 5 g N per m2. The N2O-fluxes from soil were measured over 56 days after fertilizer application. Grass dry matter yields, when using CC and PP treatments, were not significantly different to the CAN treatment (p > 0.05). After reducing its salinity, AA also showed no differences to CAN on plant growth and the lowest coefficient of variation for dry matter yield as an indicator for yield stability. Accumulated N2O-emissions were lowest in the control and were 3-times higher in AA and CC compared to CAN (p < 0.05). If salinity levels are moderate, jellyfish application to soil can compete with artificial mineral fertilizers in terms of N-supply for above- and belowground yield response, regardless of jellyfish species used. However, elevated N2O-emissions are likely to affect its suitability for large-scale application. Nevertheless, if energy-efficient methods of drying and desalination of jellyfish can be developed, in coastal areas dried jellyfish is a valuable fertilizer in coastal areas, particularly in situations where nutrient supplies for agriculture are limited.

In intensive dairy farming in Northwest Europe resource-efficiency of forage production based on permanent grassland in combination with continuous maize is undermined by high nitrogen surpluses. With respect to the paradigm of ecological intensification (EI), a field experiment was set up in northern Germany to answer the question of whether rotational fodder production including silage maize (Zea mays L.) and grassland combined with no-till soil cultivation represents an alternative to conventional tillage. A 10-year-old grassland sward was converted to maize in two ways: (i) with conventional tillage (CT) and (ii) with no-tillage (NT). There were two rates of N-fertilization: fertilized (N1), (grassland 380 kg N ha−1, maize 90 kg N ha−1) and unfertilized (N0). Aboveground net primary production (ANPP) was not significantly different in N1 treatments, with average maize yields of 18 (NT) and 21 t ha−1 (CT). Belowground net primary production (BNPP) showed similar biomass production in NT and CT. N-release from the old sward made additional fertilization unnecessary in the first year. A beginning differentiation between both tillage systems in the second year showed a significant decline in N-yield and N-release in NT N0 treatments. However, crop performance and N-release in N1 treatments continued to be comparable to CT. In terms of N leaching, tillage intensity had no clear effect on drainage N-losses. We conclude that due to comparable yields in both tillage treatments, no-till maize cropping following several years of grassland leys can contribute to EI by saving N-fertilizer input.

The global warming potential of milk production is a key aspect in the assessment of its eco-efficiency. The carbon footprint summarises the climate-relevant emissions of the production cycle, with this study focussing on the emissions from cradle to farm gate as boundaries. Numerous life cycle assessments were published in recent years, presenting the carbon footprint for different regions, production systems and management scenarios. However, despite the obvious high scientific interest in this topic, general conclusions on the climate-friendliness of contrasting production systems can hardly be drawn and there is no clear answer to the question of whether or not grazing systems provide an overall more climate-friendly alternative to confinement systems. To resolve this discussion, a meta-analysis was applied to a dataset, created with data from a selection of 30 published life cycle assessments, comprising in total 87 carbon footprint values from 15 different countries. After a standardisation process, three production system categories (pasture-based, mixed and confinement) were defined based on feeding parameters. Aside from the comparison of the production systems, the effects of various production variables (pasture and concentrate intake, milk yield per cow, milk yield per kg of metabolic live weight, mineral nitrogen fertilisation, feed efficiency and replacement rate) were analysed. Therefore, linear and level-log mixed models were developed and analyses of covariance performed. As the dataset used for the analysis covered a large range of different intensities per production system, the results are based on a robust analysis and can be extrapolated to any milk production system with known in- and outputs. The results show that increases in milk yield, pasture intake and feed efficiency decreased the carbon footprint of milk significantly, independent of the production system. However, the mitigation potential is limited across production systems with regard to their productivity thresholds. The comparison of the systems without consideration of other production parameters did not reveal any significant differences. When controlling for milk yield, however, the pasture-based system achieved lower carbon footprints compared to the other production systems. Thus, irrespective of the importance of milk yield for emissions and the generally lower milk yields of the pasture-based production system, this system still offers a competitive climate impact.

Intensive confinement (IC) systems for dairying have become widespread during the last decades. However, potential advantages of alternative systems such as full-grazing (FG) or integrated dairy/cash-crop (IFG) systems with regards to better provision of ecosystem services are widely discussed. To investigate performance and environmental impacts, we compared four prevailing dairy systems using an on-farm research study. The farm types differed in their share of pasture access and quantity of resource inputs: (i) an IC with a high import of supplements and mineral fertilizers; (ii) a semi-confinement (SC) with daytime pasture access during summer and moderate import of supplementary feeds representing the base-line scenario; (iii) a FG based on grazed seeded grass-clover swards with no purchased N-fertilizers and low quantities of supplementary feeds; and (iv) an IFG comparable to FG but based on grass-clover leys integrated in a cash-crop rotation. Results revealed highest milk productivity (16 t energy-corrected-milk (ECM) ha−1) and farm-N-balance (230 kg N ha−1) in IC; however, the highest product carbon footprint (PCF; 1.2 CO2eq kg ECM−1) and highest N-footprint (13 g N kg ECM−1) were found in the baseline system SC. The FG and IFG revealed on average similar forage dry matter yields (10 – 11 t DM ha−1) at similar crude protein and net-energy-lactation ratios per kg DM-intake compared to the IC and SC. The PCF in FG were comparable to IC (0.9 vs. 1.1 kg CO2eq kg ECM−1) but at a lower N-footprint (9 vs. 12 g N kg ECM−1). However, despite low measured N-losses in the FG system, the farm-N-surplus was exceeded by 90 kg N ha−1. A further reduction was only possible in the IFG (50 kg N ha−1) by accounting for a potential N-carry-over from N-rich plant residues to the cash-crop unit, leading to the lowest PCF (0.6 kg CO2eq kg ECM−1) for the IFG, with still moderate milk yield levels (~10,500 kg ECM ha−1). According to this bottom-up approach based on field data, improved integrated grazing systems could provide an important opportunity to increase the ecosystem services from dairy farming, operating with land use efficiencies similar to IC.

The use of forage legumes and herbs in temporary grassland swards is a promising strategy to enhance productivity, protein supply, herbage quality and species diversity in forage-based low input dairy production. Species containing plant specialized metabolites (PSM; e.g. tannins or polyphenol oxidase) are associated with positive effects on ruminants’ health, performance and nitrogen use efficiency. However, plant growth characteristics and the occurrence of PSMs with potential for improved nutritive value vary greatly depending on species and environment and to date, few species have been exploited agronomically. Thus, the current study aims to screen a range of forage species that are abundant in low input and semi-natural grasslands, in terms of productivity and forage quality for dairy cows under limited nitrogen availability in a ley system. Pure stands of eight legumes, six herbs and perennial ryegrass as reference, were established in a field experiment and sampled over two years (2010 and 2013) in their first full production year. Freeze-dried plant material was analysed for crude protein (CP), enzyme soluble organic matter (ESOM), fibre parameters (ADF, NDF), total phenolics (TP) and condensed tannins (CT). The species variation was significant for each parameter (P < 0.001). In comparison to high yielding legumes, herbage production of investigated alternative species was generally low, but for Cichorium intybus and Plantago lanceolata comparable or even higher than for Lolium perenne. Differences existed in yield development throughout the year, thus exhibiting temporal asynchrony for improved performance if grown in mixtures. Apart from Onobrychis viciifolia, the CP concentration in legume species was highest while ESOM was outstandingly high in herbs (except Plantago lanceolata). TP concentration was generally higher in herbs but in Onobrychis viciifolia and Lotus corniculatus the concentration of condensed tannins exceeded 10 g kg−1 DM. The results indicate that alternative forage species exist with high forage quality and potentially promising PSM concentrations, thus making them interesting additions for temperate grasslands.

For arable stockless farming systems, the integration of catch crops (CC) during the fallow period might be a key for closing the nitrogen (N) cycle, reducing N leaching and increasing the transfer of N to the subsequent crop. However, despite considerable research efforts, the fate of N in such integrated systems remains unclear. To address this, a two-year field experiment was carried out in northern Germany with different CC, including frost-tolerant and frost-killed CC. The experiment started following a two-year ryegrass/red clover ley, which was subsequently sown with a cereal (CE) or a grain legume (field pea, PE). This provided two contrasting systems with high residual N in autumn. The results showed high N uptake of the CC, ranging from 84 to 136 kg N ha&minus, 1 with PE as the pre-crop, and from 33 to 110 kg N ha&minus, 1 with CE. All CC reduced N leaching compared with the control, a bare fallow over autumn/winter. Of the various CC, the frost-killed CC showed higher leaching compared with the other CCs, indicating mineralisation of the CC residue in the later autumn/winter period. The process based APSIM (Agricultural Production SIMulator) model was used to simulate N cycling for a cereal grain legume rotation, including a frost-killed and a frost resistant CC. While the model simulated the biomass and the N uptake by the crops, as well as the reduction of N leaching with the use of CC well, it under-estimated N leaching from the frost-killed CC. The study showed that all CC were affective at reducing N leaching, but winter hard catch crops should be preferred, as there is a risk of increased leaching following the mineralisation of residues from frost-killed CC.

Fertilized agricultural soils serve as a primary source of anthropogenic N2O emissions. In South Africa, there is a paucity of data on N2O emissions from fertilized, irrigated dairy-pasture systems and emission factors (EF) associated with the amount of N applied. A first study aiming to quantify direct N2O emissions and associated EFs of intensive pasture-based dairy systems in sub-Sahara Africa was conducted in South Africa. Field trials were conducted to evaluate fertilizer rates (0, 220, 440, 660, and 880 kg N ha&minus, 1 year&minus, 1) on N2O emissions from irrigated kikuyu&ndash, perennial ryegrass (Pennisetum clandestinum&ndash, Lolium perenne) pastures. The static chamber method was used to collect weekly N2O samples for one year. The highest daily N2O fluxes occurred in spring (0.99 kg ha&minus, 1 day&minus, 1) and summer (1.52 kg ha&minus, 1). Accumulated N2O emissions ranged between 2.45 and 15.5 kg N2O-N ha&minus, 1 and EFs for mineral fertilizers applied had an average of 0.9%. Nitrogen in yielded herbage varied between 582 and 900 kg N ha&minus, 1. There was no positive effect on growth of pasture herbage from adding N at high rates. The relationship between N balance and annual N2O emissions was exponential, which indicated that excessive fertilization of N will add directly to N2O emissions from the pastures. Results from this study could update South Africa&rsquo, s greenhouse gas inventory more accurately to facilitate Tier 3 estimates.

Sustainable intensive agriculture requires enhanced nitrogen use efficiency and reductions in nitrogen (N) leaching losses. To investigate if organic farming systems have potential to achieve this, a comparison between conventional and organic arable farming was carried out over a two-year period. Two differently managed specialized organic arable crop rotations (low N-intensive (Ol), semi-N-intensive (Os)), and a typical N-intensive conventional crop rotation (Ch) were studied. The study was done under commercial farm scale conditions covering close to 400 ha in total (5−23 ha field sizes) in a highly productive arable region on fertile soils in northern Germany. Nitrogen leaching losses were measured using ceramic suction cups. Two functional units were used as indicators for eco-efficiency: N losses per area and per unit of grain equivalent (GE) produced. Results revealed that organic arable crop rotations reduced the nitrate (NO3-N) leaching loads per area significantly, with losses (kg NO3−-N ha-1 a-1) of 22.0 in Ol, 24.4 in Os and 35.1 in Ch. In contrast, when using the functional unit ‘nitrate leaching per grain equivalent’ as an indicator for eco-efficiency the conventional system resulted in 50 % lower N leaching loads per GE. This was due to the much higher land use efficiency of the conventional system (115 GE ha-1 vs 36 GE ha-1 for Ol and 38 GE ha-1 for Os), which resulted in N leaching losses (kg NO3-N GE-1) of Ch 0.32 for Ch, 0.64 for Ol, and 0.66 for Os. Regarding EU-Nitrate directive threshold for drinking water of 11.3 mg NO3-N l-1, all crop rotations exceeded the critical load. For the various main crop/preceeding crop sequences, the soil mineral N content at the end of the vegetation period and the autumn N uptake were the best predictors for N leaching, whereas for the aggregated effect across the various crop rotations within a farm system the N balance was the best descriptor. Considering N leaching loads our results show that both, specialized arable conventional and organic farming systems fail to meet the requirements of given environmental standards for water protection in the EU. This suggests that integrated approaches beyond such specialised systems are necessary, which are based on a balanced combination of forages (with two year leys), catch crops and cash crops.

It is unclear whether the use of multi-species swards is a suitable measure for climate change adaptation by achieving high and stable dry matter (DM) production and good forage quality in grazing systems. The objective of the study is to evaluate whether a complex rather than a simple grass clover mixture enhances performance under nitrogen (N)-deficient conditions due to greater diversity in plant functional traits. During a four-year field experiment, a three-species and a seven-species grass clover mixture were compared under one cutting-for-conservation and two simulated grazing (defoliation every three or four weeks) treatments. The results revealed a similarity in the DM yields of both seed mixtures, indicating that in the given conditions the species in the simple mixture already offered crucial yield-determining functional traits. Different growth patterns, however, led to higher intra-annual yield stability in the complex mixture. In the cutting-for-conservation system, DM yields were higher, but this came at the expense of reduced metabolisable energy and crude protein contents and lower inter-annual yield stability. We conclude that higher seeding costs for multi-species mixtures are compensated by greater yield stability while offering the potential for additional eco-system services like enhanced carbon sequestration and diverse food for pollinators.

Ploughing of grassland for reseeding can result in a temporary decline in soil carbon stocks due to reduced gross primary production and increased soil respiration. To improve understanding of processes affecting the decay of soil organic matter after grassland renovation we measured soil respiration and soil carbon stocks for several months after ploughing and reseeding of 16-year-old grass-clover swards on a sandy loam soil in Sep 2010 (I), May 2011 (II), Sep 2011 (III) and May 2012 (IV). Simultaneously, to establish the CO2-flux baseline, the ecosystem respiration, consisting of autotrophic and heterotrophic soil respiration, was measured on intact control swards (IG). Collected data were used to calibrate a soil carbon model to estimate mid- and long-term carbon losses. Results showed that, on the basis of the model used, heterotrophic soil respiration from ploughed plots exceeded the IG baseline in all experimental periods (I-IV). The amount of residual plant material at the time of ploughing and increased decay of native soil organic matter for approximately six months after soil disturbance were identified as the main drivers for enhanced soil respiration in the short-term. Long-term simulation of the calibrated model for 100 years indicated that net soil carbon stocks can decrease by 21 and 14 Mg C ha−1, compared with intact grassland, when sward renovation by reseeding, involving ploughing, is conducted every 5 to 10 years, and that grassland reseeding in spring carries a higher risk of soil carbon losses compared with reseeding later in the year.

Ruminant livestock in agriculture is one of the largest contributors to anthropogenic greenhouse gas (GHG) emissions. One GHG mitigation strategy is to maintain or increase soil carbon stocks. However, the estimation of the impact of agricultural production systems on soil carbon stocks is often difficult due to lack of data regarding the above- and belowground allocation of the net primary production of plants. Hence, in a 7-year field experiment in northern Germany, the aboveground net primary productivity and carbon budget of three different forage production systems (a crop rotation (grass-clover, maize and winter wheat); continuous maize; and continuous grassland) were quantified, with belowground net primary productivity being determined in two production years. While the net primary production was similar across all systems and ranged between 12.2 and 13.3 t organic matter ha−1, the belowground fraction of the NPP was higher in grasslands with up to 35%, compared to 18 and 23% in continuous maize and the crop rotation. Accordingly after deduction of harvest removal also the carbon inputs as predicted by the soil carbon model were much higher in grassland and carbon stocks are projected to increase by +413 kg C ha−1 a−1 in fertilized grasslands, yet are projected to decrease by −183 kg C ha−1 a−1 in unfertilized continuous maize. However, the best option with respect to both carbon inputs and harvestable yields was the crop rotation, obtaining almost identical yields with the continuous maize with nearly balanced carbon stocks independent of the fertilization.

Management of grassland may affect the dynamics of soil organic carbon (SOC). Objectives were to analyze the effect of different harvesting frequencies and nitrogen fertilization regimes on SOC and total N stocks in a field trial on a sandy loam to loamy sand soil of a grassland site near Kiel (Germany). Additionally, effects on microbial biomass C (Cmic) and ergosterol (as proxy for fungi) contents, water-stable aggregate size-classes and density fractions were studied. In the surface soil (0–10 cm), SOC and total N stocks, amounts of large water-stable macroaggregates (> 2000 µm) and contents of Cmic and ergosterol were significantly higher under a five cut regime. Cmic (rSpearman = 0.61) and ergosterol contents (rSpearman = 0.67) were correlated with amounts of large water-stable macroaggregates suggesting that fungi and microbial biomass play an important role in binding of small macroaggregates into large macroaggregates. The free light fraction of SOM showed significantly higher C concentrat...

The need for improved herbage yield and forage quality, on intensively managed grassland, in dairy farming systems, often results in land being brought into tillage, either by grassland reseeding or conversion to arable cropping (particularly maize ( Zea mays L.) for silage). However, both options are likely to increase the greenhouse gas emissions (GHG) after grassland cultivation, particularly when this involves ploughing, although there is limited information about the level of emissions. In order to estimate whether the time of ploughing and type of forage crop would affect the annual emissions of the important GHG nitrous oxide (N 2 O) in the year after soil disturbance of grassland, a field experiment was established on a Eutric Luvisol in northern Germany. The three factorial experiment comprised the effect of land use management (four treatments: ploughing and reseeding in autumn; ploughing and reseeding in spring, ploughing and conversion to maize in spring; control treatment of intact permanent grassland); the effect of nitrogen (N) fertilizer input (two treatments: 0 and 240 kg N ha −1 year −1 applied as cattle slurry); and the experimental year (two years). Treatments were arranged with three replicates in a randomized block design. N 2 O emissions were measured on a weekly basis with the static chamber method and N drainage during winter was estimated using suction cups. Thus, direct and indirect N 2 O emissions (via N leaching) were calculated per ha as well as per unit of forage yield. Results showed that ground-frost and freeze-thaw cycles were major drivers of enhanced N 2 O fluxes during the winter following ploughing and reseeding of grassland in autumn, resulting in the highest direct emissions of 21.31 kg N 2 O-N ha −1 year −1 . Emissions following grassland ploughing in spring were mainly driven by high soil mineral N-concentrations but with maximum figures of 3.90 and 6.32 kg N 2 O-N ha −1 year −1 after reseeding and conversion to maize respectively. Emissions in the intact permanent grassland were lowest in both years. Forage yield related emissions were also highest for grassland ploughing and reseeding in autumn and lowest for intact permanent grassland, but with no significant differences for reseeding and maize cultivation after grassland ploughing in spring. Application of slurry increased annual N 2 O emissions, particularly when applied in the year of reseeding, but with a lower calculated emission factor as advised by the IPCC guidelines for N fertilizers. We conclude that sustaining highly productive permanent grass-clover swards with moderate N fertilization and without tillage is the best option for ‘climate-smart forage production’ followed, when unavoidable, by tillage operations only in early spring for direct grassland reseeding, or delayed reseeding using a high yielding forage crop like maize.

Pore size distribution (PSD), and wetting/drying mechanism enable proper understanding of how land management changes influence soil structure and function dynamics as a measure for soil quality. Therefore, the objectives of this study are to: (i) estimate the soil quality index under continuous long term grassland management, and its impacts on soil hydro-physical and functional properties; (ii) differentiate the impact of the grassland age on the PSD curve structure using data obtained from soil water retention and (iii) determine the impact of wetting/drying on soil structure and functional dynamics. Soil hydro-physical, and functional properties of grassland at different ages (1, 2, 8, 13, 19 and 24 years) after renovation by plowing were determined. Data from the soil water retention curves were fitted to van Genuchten’s equation. Three (3) wetting/drying cycles were considered for grassland managed for 2, 13 and 24 years in order to detect further soil structure developments due to assumed climate change impacts. Results showed that total soil porosity and the number of coarse pores increased, while the soil bulk density decreased as sward age increases in all studied depths (0–5, 10–15 and 20–25 cm). Soils at 24 years grassland management showed the most intense changes in pore continuity by an increased hydraulic conductivity and an improved pore size distribution which both support root growth and nutrient as well as water accessibility. Notable (significant) difference in the soil hydro-physical properties occurred as early as 2years after grassland renovation, but a measurable improvement of soil functions down to 30 cm depth lasted 19 years. To test the hypothesis how far could a more intense wetting/drying furthermore enhance the restructuring we carried out extra wetting/drying experiments. It could be shown that the Ksat and air permeability values increased the more pronounced when the matric potential gradients and these cycles occurred more often. Thus, with increase in sward age and cycles these values further increased. However, the formation of macroscopic more homogenous structure can also result in higher values of Ksat and air permeability after shorter periods but the heterogeneity of the data was greater than after 24 years, in all depths. Therefore, results from our study can be used to establish a long-term sustainable grassland management without irregular soil inversion as effective strategy for improving soil structure and functionality.

Converting grassland to arable cropping leads to reduced soil organic carbon (SOC) stocks and thereby affects soil and climate protection goals. However, in forage production systems, silage maize produces considerable amounts of herbage and metabolizable energy yields for ruminants. To answer the question whether using direct drilling, as a minimal soil invasive technique, is able to prevent SOC stock degradation without loss of herbage yield in ley-arable systems, a two-year field experiment was set up on a sandy loam soil in northern Germany. In pre-management, a 10-year-old grassland sward was eradicated with a glyphosate and then sown with silage maize with (i) direct drilling (no-till, NT); and (ii) by conventional mouldboard ploughing (conventional tillage, CT). Each treatment included a non-N-fertilized (N0) and a 90 kg N ha−1 year−1 fertilized (N1) treatment. All silage maize treatments were analyzed in terms of above- (ANPP) and belowground net primary production (BNPP) and potential C input in comparison with the grassland control (GC) during the two years after conversion to arable silage maize. Quantification of SOC stocks and origin of C derived from residual plant material was estimated by the determination of natural 13C isotope abundance. Long-term impacts on SOC of a proposed ley-arable system (three years of grassland followed by three years of silage maize) using NT and CT practices were predicted using a soil C model. Results showed that ANPP and BNPP did not differ (p > 0.05) between tillage treatments and the two experimental years. Fertilization increased ANPP only in the second year with a lower fraction of roots belowground in comparison with N0 (p < 0.05). According to the 13C signature the total of silage maize-derived C after two years was up to 2.5–3.2 t C ha−1 in both tillage treatments, of which ∼76% can be explained by the measured C inputs from plant residues. The NT treatment showed lower amounts of decay of previously sequestered C in the upper 10 cm during the two-year period after land use change to silage maize. However, long-term predictions revealed ongoing breakdown of soil C regardless of tillage management used for continuous silage maize after conversion from grassland. The insertion of a three-years grass phase followed by three years of silage maize established with NT techniques was able to maintain SOC stocks in the long-term.

Root functional traits (RFTs) are crucial for understanding nutrient cycling processes. However, seasonal variation of RFTs and their potential changes in root foraging pattern have been almost ignored in field studies. In this work, belowground net primary production (BNPP, g m−2), root length density (RLD, km m−2), specific root length (SRL, m g−1), root N concentration and C/N ratio in defoliated grass-clover swards of different sward ages and receiving different cattle slurry levels were investigated for 2 years. All measured RFTs showed significant seasonal variation: in general, seasonal variation was most marked between primary growth period (until heading stage of perennial ryegrass) and subsequent regrowth periods following defoliation; meanwhile, the rooting pattern also differed. These phenomena were not affected by current management or sward composition, but were correlated with plant C availability. Daily BNPP and RLD rates varied 7- to 8-fold in the growing season. Moreover, BNPP and RLD were asynchronous due to seasonal variation in SRL. Rooting pattern and the relationship with shoot phenology are discussed. We conclude that root functional traits vary with season; thus, roots which develop in different seasons may be involved in belowground nutrient cycling processes with different turnover characteristics; trade-off among traits may also involve temporal variation. Root-C related investigations in grass-clover swards should include root mass sampling rather than use of root length observations alone.

Estimation of belowground net primary production (BNPP) is crucial for prediction of grassland soil organic carbon sequestration, but there are high coefficients of variation (CV) among methods of estimation. We compared accuracy and precision of two variations of the traditional soil core method and three of the ingrowth core method, over 2 years on grass–white clover swards in Germany. The ingrowth core method (5- to 9-week ingrowth period) provided the most accurate BNPP estimate (471 g m−2) with the highest precision (CV: 31%), whereas the two soil core approaches resulted in underestimation and high error. Comparing results with other grassland studies, we found that reliability of the ingrowth core method was influenced by ingrowth period and sward rooting pattern related to grass phenological stages, while the precision was determined by ingrowth period and grassland productivity. We therefore recommend using the ingrowth core method for managed grasslands where belowground productivity is relatively high and installation disturbance is likely to be negligible. Using a 6- to 8-week ingrowth period, the method delivers reliable and feasible BNPP estimates for temperate managed grasslands which can be applied to long-term soil carbon budget simulation. Results from our work and other studies also indicated that standing root biomass masks seasonal pattern of rooting due to synchrony between root birth and death. The soil core method is likely to lead to underestimates and higher errors than the ingrowth core methods and thus should be avoided.

Intensification of forage production often leads to conversion of grassland to arable land, with associated high greenhouse gas (GHG) emissions. By implementing seeding with minimal soil disturbance, i.e. no-tillage, reduction of GHG emissions is possible, while crop yields can still be considerable. On a sandy loam in the Eastern Uplands of Schleswig-Holstein, Northern Germany, a two-year field experiment (Apr 2015 - Mar 2017) was set up, with a 10-year-old grassland sward converted to silage maize (Zea mays L.) with i.) conventional tillage by mouldboard ploughing (CT) and ii.) no-tillage (NT) representing the factor management. The factor N-fertilization consisted of two levels: 90 kg N ha−1 (N1) or no fertilization (N0). The annual N2O, CH4 and CO2 emissions were assessed with the closed chamber method. Global warming potential (GWP) expressed in CO2 equivalents (CO2eq) was calculated on an area basis and at product level to compare the different management systems. The N2O emissions were significantly increased after conversion in the first experimental year but showed no effect of the factor management. The annual GWP was on average highest in the CT treatments with 23.9 (N0) and 29.3 t CO2eq ha−1 (N1), while NT reduced GWP by 67 and 46 % for N0 and N1 compared to CT. Biomass removal by harvesting dominated the GWP in all treatments. Yield-related emissions were significantly lower in NT than CT maize, thus indicating higher eco-efficiency of this management system.

A large share of peatlands in northwestern Germany is drained for agricultural purposes, thereby emitting high amounts of greenhouse gases (GHGs). In order to quantify the climatic impact of fen soils in dairy farming systems of northern Germany, GHG exchange and forage yield were determined on four experimental sites which differed in terms of management and drainage intensity: (a) rewetted and unutilized grassland (UG), (b) intensive and wet grassland (GW), (c) intensive and moist grassland (GM) and (d) arable forage cropping (AR). Net ecosystem exchange (NEE) of CO2 and fluxes of CH4 and N2O were measured using closed manual chambers. CH4 fluxes were significantly affected by groundwater level (GWL) and soil temperature, whereas N2O fluxes showed a significant relation to the amount of nitrate in top soil. Annual balances of all three gases, as well as the global warming potential (GWP), were significantly correlated to mean annual GWL. A 2-year mean GWP, combined from CO2–C eq. of NEE, CH4 and N2O emissions, as well as C input (slurry) and C output (harvest), was 3.8, 11.7, 17.7 and 17.3 Mg CO2–C eq. ha−1 a−1 for sites UG, GW, GM and AR, respectively (standard error (SE) 2.8, 1.2, 1.8, 2.6). Yield-related emissions for the three agricultural sites were 201, 248 and 269 kg CO2–C eq. (GJ net energy lactation; NEL)−1 for sites GW, GM and AR, respectively (SE 17, 9, 19). The carbon footprint of agricultural commodities grown on fen soils depended on long-term drainage intensity rather than type of management, but management and climate strongly influenced interannual on-site variability. However, arable forage production revealed a high uncertainty of yield and therefore was an unsuitable land use option. Lowest yield-related GHG emissions were achieved by a three-cut system of productive grassland swards in combination with a high GWL (long-term mean ≤ 20 cm below the surface).

Plant specialized metabolites (PSMs) have been found to reduce the activity of soil microorganisms lowering the decay rates of plant residues, which might positively affect C sequestration. Several PSM are produced by temperature forage species, but the impact of those material on decomposition has primarily been studies in forest ecosystems. Thus, the objective of this study was to i) quantify the relevant PSMs contained in the aboveground and belowground parts of forage species, ii) identify differences in CO2-emissions resulting from the root turnover of those species, and iii) identify the main chemical root properties that affect the CO2-emissions resulting from the root turnover. Eight cultivars of five forage species were grown in pots in a greenhouse. Aboveground- and belowground biomass was harvested and proanthocyanidins (PAs) and other PSMs (alkaloids and flavonoids) were measured. Afterwards, the roots were incubated for 58 days to investigate the root turnover while the CO2-emissions by the decay of roots from the soil were measured. Results showed i) PA concentrations varied widely among the species (7.8–45.6 mg PA g−1 dry matter (DM)), as well as between above- and belowground biomass; ii) that CO2-emissions differed significantly in terms of dynamics and the amount (15–40% of added C); and iii) that none of the measured root chemical properties could sufficiently explain the variance in CO2-emissions. Nevertheless, the almost three-fold range in turnover rates shows great potential for the future in terms of specifically designing temperate grasslands via species selection to enhance potential carbon sequestration.