Mineral N-fertilization Research Articles

Effect of agricultural management practices on rice yield and greenhouse gas emissions in the rice–wheat rotation system in China

Agricultural management practices (AMPs) have the potential to significantly enhance crop yield, albeit with the possible side effect of escalating greenhouse gas emissions. Few studies have undertaken a comprehensive quantification of the impact of AMPs on crop production and soil GHG, particularly in identifying the optimal AMPs for rice cultivation within rice-wheat rotation system. Here, we combined data analysis and keyword search methods on 1433 individual experimental observations from 172 studies on diverse soil types in the subtropical monsoon climate zone of China to assess the impact of AMPs on rice yield, CH4 and N2O emissions, total greenhouse gas emissions (TGHGE). We focused on four key AMPs: mineral N fertilizer management (including ordinary N fertilizer and slow−/controlled-release fertilizer (SCRF)), organic material management (incorporating organic fertilizer, biochar amendment, and straw return), water-saving irrigation, and no-tillage. Our result showed the rice yield ranged from 2525 to 31,196 kg ha−1, and mineral N fertilizer and organic material management boosted rice yield by 2.84–16.19 % and 2.47–8.52 %, respectively. In terms of N2O emissions, biochar amendment resulted in a decrease of 13.05 %, while ordinary N fertilizer, organic fertilizer, and water-saving irrigation led to increases of 63.16 %, 136.66 %, and 37.41 %, respectively. The implementation of SCRF, water-saving irrigation, and no-tillage significantly curtailed CH4 (6.83 %–35.91 %) and TGHGE (6.22 %–20.59 %). Conversely, organic fertilizer and straw return significantly escalated CH4 emissions by 102.20 % and 33.64 % and TGHGE by 85.03 % and 32.40 %. Rice yield and GHG emissions are mainly influenced by variables such as soil bulk density, pH, soil organic carbon, soil texture, mean annual temperature, and total nitrogen. Our study demonstrates that the application of SCRF, water-saving irrigation, and no-tillage can effectively reduce GHG without compromising yield. These practices are particularly effective under climatic and soil conditions of rice-wheat rotation systems in China, thereby contributing to the sustainable rice farming.

Minimizing mineral-N fertilization Superior seedless grapevines by using humic and fulvic acids

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Impacts of the components of conservation agriculture on soil organic carbon and total nitrogen storage: A global meta-analysis

Conservation agriculture (CA) can be an important strategy for improving soil organic carbon (SOC) and total nitrogen (TN). Numerous studies have examined SOC and TN dynamics in different cropping systems. However, there is some uncertainty regarding the relative impacts of some CA practices, and it is not always clear how other agricultural management, particularly nitrogen addition, interacts with these practices to influence SOC and TN sequestration. Thus, we conducted a global meta-analysis of 752 comparisons from 97 papers to analyze the impacts of nitrogen fertilizers and CA practices (namely crop diversification, minimal soil disturbance (no-tillage) and permanent soil cover), on SOC and TN content worldwide. Overall, our study showed the most significant increase of SOC [21.39 % (CI = 15.16 to 28.64)] and TN [54.34 % (CI = 26.19 to 96.69)] stock with CA practices compared to conventional practices in the 0–15 cm soil depth. It also showed a significant increase in SOC and TN stock with all the individual components of CA compared to conventional practices in the 0–15 cm soil depth. However, the impact of CA on SOC and TN is reduced in 0–60 cm depths compared to surface soil depths due to the limited input of crop residue deeper in the soil profile. Manure and manure mixed with mineral-N led to greater SOC sequestration [20.67 % (CI = 15.23 to 27.10) and 41.67 % (CI = 31.03 to 52.79), respectively] than mineral-N alone [9.08 % (CI = 6.44 to 11.83)]. Cropping systems that included legume residue decreased the C/N ratio. This highlights that adequate mineral-N fertilizer addition may also be required in conjunction with residue retention practices to improve SOC and TN content. Overall, these results show that CA systems that include legume residue and manure mixed with mineral-N have great potential to increase SOC and TN, particularly at 0–15 cm and 0–30 cm soil depth.

Effect of crop rotation and straw application in combination with mineral nitrogen fertilization on soil carbon sequestration in the Thyrow long-term experiment Thy_D5

AimsThe aim of study was to quantify the temporal change of soil organic carbon content in relation to agricultural management for a dry sandy arable soil and to derive the C sequestration potential.MethodsWe analyzed data from a long-term field experiment with three crop rotations of different cereal proportions, with two levels of straw application (removal/return) in combination with four mineral nitrogen rates (40 … 160 kg ha-1 yr-1). Treatments are arranged in a two-factorial block design with two replicates for each rotation. During the 24-year study period, grain and straw yield of two cereal test crops and soil organic carbon content in topsoil were determined annually from each plot.ResultsSoil organic carbon content was positively influenced by removing non-cereal crops from the rotation and – to a smaller extent – by straw application. Increasing mineral N-fertilization from 40 kg ha-1 yr-1 to higher rates increased grain yield of rye but not barley, increased straw yield of both cereals more, with no effect of higher straw yields on soil organic carbon content.ConclusionsDespite the overall soil organic carbon content of the sandy soil under study is comparatively low, the results indicate that agricultural management has a relevant impact on soil carbon stocks. Straw return contributes to carbon sequestration even in rotations with a low potential for reproduction of organic matter. High mineral N-fertilization is not an adequate measure to sequester carbon in these soils.

Interactive effects of crop residue quality and nitrogen fertilization on soil organic carbon priming in agricultural soils

Soil organic carbon (SOC) priming affects C sequestration in soils, the intensity of which differs depending on residue quality. N fertilization could also alter SOC priming. However, the interaction of crop residue quality and N fertilization on the SOC priming is still not clear. To address this gap in knowledge, we conducted this study. We undertook a 110-day laboratory incubation experiment to evaluate the SOC priming and sequestration induced by maize shoot and root residues with and without the application of mineral fertilizer-N in two types of agricultural soils (Andisol and Entisol). Application rates of maize residue and N were 3 g C kg−1 soil and 60 mg N kg−1 soil, respectively. 13C-labeled maize residue allowed quantifying residue decomposition and calculating SOC priming and sequestration. After 110 days of incubation, the cumulative intensity of priming effect was higher for root residue than shoot residue. Addition of N results in contrasting effects on the priming effect induced by root and shoot residue in both types of soils; with root residue, it reduced the intensity of priming effect and resulted in a higher net C sequestration because of reduced N mining, whereas it had little effect with shoot residue, where co-metabolism is the likely explanation for the positive priming effect. Crop residue quality and N fertilization can interactively affect the SOC priming. N fertilization is beneficial for soil C sequestration when soil is treated with low-quality crop residue (e.g., root residue) because of lowering of the intensity of priming effect and crop residue decomposition.

Effect of chemical and mechanical grassland conversion to cropland on soil mineral N dynamics and N2O emission

Grassland conversion to cropland bears a risk of increased nitrate (NO3−) leaching and nitrous oxide (N2O) emission due to enhanced nitrogen (N) mineralization. This study investigates the dynamics of mineral N and N2O emissions following chemical and mechanical conversion from permanent grassland to cropland (maize) at two sites with different texture (clayey loam and sandy loam) and fertilization regime (with and without mineral N-fertilization) over a two-year period. Soil mineral N levels increased shortly after conversion and remained elevated in converted plots compared to permanent grassland or long-term cropland in the second year of investigation. Fluxes of N2O were higher from converted plots than permanent grassland or cropland. However, soil mineral N contents and cumulative N2O emissions did not differ between conversion types. Only the distribution of N2O losses over the two years differed: while losses were of similar magnitude in both years in mechanically converted plots, the major part of N2O loss in chemically converted plots occurred in the first year after conversion while emissions approximated grassland level in the second year. N2O fluxes were mainly controlled by water-filled pore space and soil NO3− levels. Despite differences in N levels at the two sites, these key findings are similar on both study sites. They indicate strongly accelerated mineralization after conversion, an effect that still lasted in the converted plots at the end of the two-year investigation irrespective of the conversion type used.

The Response of the Soil Microbiota to Long-Term Mineral and Organic Nitrogen Fertilization is Stronger in the Bulk Soil than in the Rhizosphere.

The effects of different agronomic practices, such as fertilization regimes, can be experimentally tested in long-term experiments (LTE). Here, we aimed to evaluate the effect of different nitrogen fertilizations on the bacterial microbiota in both rhizosphere and bulk soil of sugar beet, in the Giessen-LTE (Germany). Fertilization treatments included mineral-N, manure, mineral-N + manure and no N-amendment. Metabarcoding and co-occurrence analysis of 16S rRNA genes, qPCR of amoA, nirK, nirS, nosZ-I and nosZ-II genes and soil physico-chemical analyses were performed. The effect of the fertilization treatments was more evident in the bulk soil, involving 33.1% of the microbiota. Co-occurrence analysis showed a rhizosphere cluster, dominated by Proteobacteria, Actinobacteria and Verrucomicrobia (hub taxa: Betaproteobacteriales), and a bulk soil cluster, dominated by Acidobacteria, Gemmatominadetes and “Latescibacteria” (hub taxa: Acidobacteria). In the bulk soil, mineral N-fertilization reduced nirK, amoA, nosZ-I and nosZ-II genes. Thirteen Operational taxonomic units (OTUs) showed 23 negative correlations with gene relative abundances. These OTUs likely represent opportunistic species that profited from the amended mineral-N and outgrew the species carrying N-cycle genes. Our results indicate trajectories for future research on soil microbiome in LTE and add new experimental evidence that will be helpful for sustainable management of nitrogen fertilizations on arable soils.

New Pelleted Plant-Based Fertilizers for Sustainable Onion Production

Pelletized plant-based fertilizers Ekofert K (red clover) and Ekofert L (lucerne) was compared to non-fertilized control and mineral N-fertilization (100 kg N ha-1) in sustainable onion cultivation (2012–2013). The organic fertilizers at pre-plant rates equivalent to 120, 180 and 240 kg N ha-1 were applied on a field fertilized with compost (25 t ha-1). The fertilizers Ekofert K and L significantly increased onion production as compared to the basic fertilization with compost alone. The increase in yield was favorably correlated with the applied fertilizer rates. The lowest rate of organic fertilizers ensured a yield at the level of mineral fertilization at the rate of 100 kg N ha-1 as single application. The higher rates of Ekofert K and L (180, 240 kg N ha-1) resulted in a marketable yield increase relative to single mineral fertilization. The use of organic as well as mineral fertilization increased nitrogen and chlorophyll contents in onion leaves, compared to the non-fertilized control treatment. The increase was positively correlated with fertilizer rates. The N-NO3 content in onion bulbs was in general not influenced by the application of organic fertilizers, compared to non-fertilized control treatment. Nitrogen content in the top soil (0–30 cm) was the highest after 5 weeks from incorporation of the fertilizers and diminished in following 4 weeks on average by 46% due to plant development and intensive nutrient uptake. After onion harvest, continued mineralization of soil organic matter and lack of uptake by plants increased average nitrogen content nearly to the level at stage of early plant growth. The N-NO3 content in soil increased with rates of the Ekofert fertilizers. In subsoil horizon (30–60 cm), the N-NO3 content was 2.5 times lower than in topsoil and significant only for the highest rate of the fertilizers.

Effect of cattle slurry application techniques on N2O and NH3 emissions from a loamy soil

AbstractWe determined N2O fluxes from an unfertilized control (CON), from a treatment with mineral N‐fertilizer (MIN), from cattle slurry with banded surface application and subsequent incorporation (INC), and from slurry injection (INJ) to silage maize (Zea mays, L.) on a Haplic Luvisol in southwest Germany. In both years, amount of available N (total N fertilized + Nmin content before N application) was 210 kg N ha−1. In the slurry treatment of the 1st year, 140 kg N ha−1 were either injected or incorporated, whereas 30 kg N ha−1 were surface applied to avoid destruction of the maize plants. In the 2nd year, all fertilizers were applied with one single application. We calculated greenhouse gas emissions (GHG) on field level including direct N2O emissions (calculated from the measured flux rates), indirect N2O emissions (NH3 and induced N2O emission), net CH4 fluxes, fuel consumption and pre‐chain emissions from mineral fertilizer. NH3 losses were measured in the 2nd year using the Dräger‐Tube Method and estimated for both years. NH3 emission was highest in the treatment without incorporation. It generally contributed less than 5% of the greenhouse gas (GHG) emission from silage maize cultivation. The mean area‐related N2O emission, determined with the closed chamber method was 2.8, 4.7, 4.4 and 13.8 kg N2O‐N ha−1 y−1 for CON, MIN, INC, and INJ, respectively. Yield‐related N2O emission showed the same trend. Across all treatments, direct N2O emission was the major contributor to GHG with an average of 79%. Trail hose application with immediate incorporation was found to be the optimum management practice for livestock farmers in our study region.

Assessment of Two Sheep Wool Residues from Textile Industry as Organic Fertilizer in Sunflower and Maize Cultivation

Sustainable agricultural practices that enhance soil fertility and increase its capacity for carbon sequestration are increasingly needed. This study evaluates two types of sheep wool residues (SWRs)—carbonized (black wool, BW) and non-carbonized (white wool, WW) to enhance soil fertility and act as a N-source. The two SWRs were tested on two plant species, in two pot experiments: ornamental sunflower on soil mixtures with each of SWR types at different concentrations (0, 0.5, 1, and 2% w/w), and maize on BW- or WW-soil mixture (1% w/w) and supplementary N fertilization (0, 50, and 100% of recommended N rates). In sunflower, with the exception of WW at 2%, all SWRs-soil mixtures increased plant growth and biomass production. Lower SWRs concentrations enhanced the growth rate at an initial stage, and in general, BW provided optimal biomass, and flower yield. In maize, the SWRs (1%), especially BW, even without N-fertilization, were beneficial for plant physiological behavior and biomass production. High mineral N-fertilization (100% N with BW1%- or WW1%-soil mixture) resulted in lower biomass than the other BW-treatments. The results highlighted the efficacy of BW on biomass production for both species growing in a sandy-loam soil, and for maize, no need for further mineral N-fertilization.

Productivity and Quality of Kohlrabi Grown in a Newly Reclaimed Sandy Soil Using Organic and Mineral-N Fertilizer regimes with or without Spraying of Spirulina platensis Extract

The current study aimed to investigate the influence of organic manure and/or mineral N-fertilizer with or without Spirulina platensis alga cells extract on growth, yield and quality of kohlrabi knobs. Field experiments were carried out on Kohlrabi (Brassica oleracea var. gongylodes) cv. White Vienna at the Experimental Farm of the Environmental Studies and Research Institute, El-Sadat City University, Egypt, during the winter seasons of 2015/2016 and 2016/2017 under drip irrigation systems. The obtained results showed that using 50% mineral-N + 50% organic-N combined with spirulina extract improved plant growth, yield and knob quality compared to other N-fertilizer regimes. Therefore, this treatment gave the best growth and increased total yield with the best knob quality as compared with no added. The highest content of nitrate in knobs (473.85 mg kg-1 DW) was recorded by using 100% mineral-N treatment (as an average in both seasons). Whereas, adding 100% organic-N recorded the lowest content of nitrate in knobs (83.45 mg kg-1 DW) as an average of both seasons. It is worthy to mention that nitrate concentration in tested kohlrabi knobs is still in the safe border for human consumption.

Improved management increases carrying capacity of Brazilian pastures

Grazing pasture without appropriate soil conservation and animal management often leads to reduced soil quality and decreased productivity because of trampling induced compaction. Our objective was to evaluate the effect of three conservation-based pasture management strategies on soil physical attributes. The treatments were (1) Brachiaria decumbens + mineral-N fertilization, (2) mixed pasture + legume (forage peanut, Arachis pintoi), and (3) Brachiaria without fertilization were compared with a native grassland reference area without management. The hypothesis is that nitrogen fertilization favors an increase in the animal stocking rate, maintaining the physical quality of the soil. The treatments had no significant effect on soil porosity, bulk density, or water retention. The S-index showed that intense animal trampling in the treatment with nitrogen fertilization resulted in the most intense degradation. Mixed pasture with the intercropped legume and N-fertilization maintained soil physical quality similar to the area without management, reinforcing the importance of appropriate soil management practices in pasture. However, although the N-fertilized area had soil physical quality similar to the others, it could support more animals, suggesting an economic advantage over other soil management practices. To preserve or enhance soil physical quality, mixed pastures and fertilization can be adopted, increasing the soil load-bearing capacity, which represents more animals per area.

Water table management and fertilizer application impacts on CO2, N2O and CH4 fluxes in a corn agro-ecosystem

Water table management with controlled drainage and subsurface-irrigation (SI) has been identified as a Beneficial Management Practice (BMP) to reduce nitrate leaching in drainage water. It has also been shown to increase crop yields during dry periods of the growing season, by providing water to the crop root zone, via upward flux or capillary rise. However, by retaining nitrates in anoxic conditions within the soil profile, SI could potentially increase greenhouse gas (GHG) fluxes, particularly N2O through denitrification. This process may be further exacerbated by high precipitation and mineral N-fertilizer applications very early in the growing season. In order to investigate the effects of water table management (WTM) with nitrogen fertilization on GHG fluxes from corn (Zea mays) agro-ecosystems, we conducted a research study on a commercial farm in south-western Quebec, Canada. Water table management treatments were: free drainage (FD) and controlled drainage with subsurface-irrigation. GHG samples were taken using field-deployed, vented non-steady state gas chambers to quantify soil CO2, N2O and CH4 fluxes weekly. Our results indicate that fertilizer application timing coinciding with intense (≥24 mm) precipitation events and high temperatures (>25 °C) triggered pulses of N2O fluxes, accounting for up to 60% of cumulative N2O fluxes. Our results also suggest that splitting bulk fertilizer applications may be an effective mitigation strategy, reducing N2O fluxes by 50% in our study. In both seasons, pulse GHG fluxes mostly occurred in the early vegetative stages of the corn, prior to activation of the subsurface-irrigation. Our results suggest that proper timing of WTM mindful of seasonal climatic conditions has the potential to reduce GHG emissions.

Soil Fertility, Onion-Maize Productivity and N-Use Efficiency as Affected by Green Manure, Mineral and Bio Fertilizers.

SOIL fertility was and still one of the most important factors controlling the productivity of crops. A field experiment was conducted at Sakha Agricultural Research Station, Egypt to assess the effect of green manure, bio-N fertilizer and mineral nitrogen fertilizer on some soil properties, mineral nitrogen fertilizer efficiency (i.e., N-use efficiency) and yield of onion (in winter season 2015/2016) following by maize (in summer 2016). Treatments included bio-N-fertilizers, mineral nitrogen fertilizer and green manure. The results showed that using all green manures (i.e., Egyptian clover and fenugreek) before planting onion significantly developed soil properties; increased availability of the studied nutrients and total porosity. Inoculations with bio-fertilizer maximize these effects on soil properties and yield of onion and maize. Interaction between fenugreek with bio-fertilizer and mineral N-fertilizer at 120 kg fed-1 attained the highest values of total onion yield, averages of bulb weight, diameter, dry matter content and nutrients-uptake of NPK in the first season after green manure application. After cultivation of maize, the highest values of grain and dry stalks yields, 100-grain weight and NPK-uptake were obtained with the interaction of Egyptian clover with bio-fertilizer and N-fertilizer at 90 kg fed-1. The use of Egyptian clover as green manure with bio-fertilizer increased N-use efficiency for onion at 60 kg N fed-1 and for maize grain yield was at 120 kg N fed-1. So, the study concluded importance of using green manures to improve soil properties and use efficiency of mineral nitrogen fertilizer.

Mineralization of organic carbon and nitrogen in semi-arid soils under organic and inorganic fertilization

Abstract Although compost is added to soils to improve their nutritive status and properties; yet upon its decomposition, considerable amounts of CO2 might be emitted to the atmosphere causing hazardous environmental risks. Investigating the mineralization of compost applied to a sandy soil and a silty clay one of low organic-C content in the green house for 90 days under soil moisture contents of 75 or 100% of FC was considered. Efflux rate of CO2 decreased considerably for one day in the sandy soil after application of the compost; beyond which showed an almost constant rate. In the silty clay soil, the efflux rate decreased obviously to achieve non detectable value 3 days later. Even in soils amended with mineral N-fertilizer, CO2 emissions were valued while decreased with time. By the end of the incubation time, the rate of C-mineralization was significantly higher in the sandy soil compared with the silty clay one. Increasing soil moisture content from 70 to 100% of the field capacity led to further increases in rates of CO2 efflux as well as org-C mineralization. The amount of N mineralized in the sandy soil was 1.7 times higher than its content in the silt clay one at the FC and 1.1 times in case of 70% of FC. In conclusion, a reversible equilibrated process between decomposition of soil organic matter and buildup of more stable organic components might exist at the same time.

ROLE OF BIOEFFECTORS AND SOIL AMELIORATES ON COWPEA YIELD GROWN ON SALINE SOIL WITH AID OF 15N ISOTOPE DILUTION TECHNIQUE

A field experiment was conducted on salt affected soil cultivated with cowpea crop (Vigna unguiculata)under drip irrigation system to evaluate the impact of using mineral fertilizer, fulvic acid, and seaweeds with or without bio-inoculation to combat soil salinity stress. All soil ameliorates were applied in combination with or without Aspergillus terreus inoculation. Seeds of cowpea plants were inoculated with Bradyrhizobium spp for all fertilization and amendment treatments. 15N isotope dilution technique was followed to accurately distinguish between N-derived sources gained by cowpea crop. Results indicated that shoot fresh weight of plants treated with full dose of mineral fertilizer was enhanced by fungal inoculation comparing to the un-inoculated plants. Similar trend, but to somewhat lower extent, was noticed with both root and seeds. Fresh weight of shoot, root and seeds of plants either inoculated or not were decreased, except shoot of un-inoculated one, when seaweeds were added as compared to those fertilized with mineral fertilizer. Similar trend, but to somewhat higher extent, was noticed with fulvic acid treatment. Contrary, seeds of plants were severely decreased in the presence of fulvic acid comparing to those treated with seaweeds or mineral N-fertilizer. The positive effect of fungal inoculation on enhancement of fresh weight was noticed with plants fertilized with mineral N-fertilizer. Nitrogen uptake by shoots of inoculated plants was higher in case of mineral fertilizer than those recorded with seaweeds but nearly similar to those induced by application of fulvic acid. In contrast, the un-inoculated plants didn't reflect any significant variation between the fertilization treatments. N uptake was increased with application of mineral fertilizer comparing to those resulted from application of seaweeds or fulvic acid. But the effect was not significant in fungal inoculated plants. N uptake by seeds of inoculated plants fertilized with full dose of mineral fertilizer was higher than those of plants treated with fulvic acid but nearly closed to those induced by addition of seaweeds. The highest values of nitrogen derived from fertilizer (Ndff) were recorded with application of mineral fertilizer. This holds true for all plant organs. Remarkable enhancement of Ndff was noticed in case of fungal inoculated plants comparing to the un-inoculated ones. Nitrogen derived from air (%Ndfa) ranged from 35% up to more than 60% depending on plant organ and fungal or non-fungal inoculation treatments. Ndfa were higher in un-inoculated plants than those recorded with the inoculated one. Seeds accumulate more Ndfa than roots or shoot.

Effect of biogas digestate, animal manure and mineral fertilizer application on nitrogen flows in biogas feedstock production

Abstract The expansion of biogas feedstock cultivation may affect a number of ecosystem processes and ecosystem services, and temporal and spatial dimensions of its environmental impact are subject to a critical debate. However, there are hardly any comprehensive studies available on the impact of biogas feedstock production on the different components of nitrogen (N) balance. The objectives of the current study were (i) to investigate the short-term effects of crop substrate cultivation on the N flows in terms of a N balance and its components (N fertilization, N deposition, N leaching, NH3 emission, N2O emission, N recovery in harvested product) for different cropping systems, N fertilizer types and a wide range of N rate, and (ii) to quantify the N footprint of feedstock production in terms of potential N loss per unit of methane produced. In 2007/08 and 2008/09, two field experiments were conducted at two sites in Northern Germany differing in soil quality, where continuous maize (R1), maize–whole crop wheat followed by Italian ryegrass as a double crop (R2), and maize–grain wheat followed by mustard as a catch crop (R3) were grown on Site 1 (sandy loam), and R1 and a perennial ryegrass ley (R4) at Site 2 (sandy soil rich in organic matter). Crops were supplied with varying amounts of N (0–360 kg N ha−1, ryegrass: 0–480 kg N ha−1) supplied as biogas digestate, cattle slurry, pig slurry or calcium-ammonium nitrate (CAN). Mineral-N fertilization of maize-based rotations resulted in negative N balances at N input for maximum yield (Nopt), with R2 having slightly less negative balances than R1 and R3. In contrast, N balances were close to zero for cattle slurry or digestate treatments. Thus, trade-offs between substrate feedstock production and changes of soil organic matter stocks have to be taken into consideration when evaluating biogas production systems. Nitrogen losses were generally dominated by N leaching, whereas for the organically fertilized perennial ryegrass ley the ammonia emission accounted for the largest proportion. Nitrogen balance of the ryegrass ley at Nopt was close to zero (CAN) or highly positive (cattle slurry, digestate). Nitrogen footprint (NFP) was applied as an eco-efficiency measure of N-loss potential (difference of N input and N recovery) related to the unit methane produced. NFP ranged between −11 and +6 kg N per 1000 m3 methane at Nopt for maize-based rotations, without a significant impact of cropping system or N fertilizer type. However, for perennial ryegrass ley, NFP increased up to 65 kg N per 1000 m3. The loose relation between NFP and observed N losses suggests only limited suitability for NFP.

Greenhouse gas emission of biogas production out of silage maize and sugar beet – An assessment along the entire production chain

The study delivers values on greenhouse gas (GHG)-emission via cultivation of silage maize and sugar beet and of GHG-saving potential of electricity produced from biogas out of both biomass crops. Data are based on three rainfed crop rotation field trials in Germany (2011–2014) representative for Central Europe and can serve as default values. It was found that GHG-emission via crop cultivation was driven mainly by nitrous oxide emission from soil and mineral N-fertilizer use and was 2575–3390kg carbon dioxide equivalents (CO2eq) per hectare for silage maize and 2551–2852kgCO2eqha−1 for sugar beet (without biogas digestate application). Integrating a GHG-credit for surplus N in the biogas digestate reduced total GHG-emission via crop cultivation to 65–69% for silage maize but only to 84–97% for sugar beet. The GHG-saving potential of electricity production from biogas was calculated for three biogas plants differing in technical characteristics. The GHG-saving potentials were generally >70% (silage maize: 78–80%, sugar beet: 72–76%) and the authors concluded that the technical setting of the biogas plant had a slight impact only. Overall, the authors assumed that the major potential for GHG-emission's reduction along the bioenergy production chain were N-management during crop cultivation and methane losses at the biogas plant. Finally, sugar beet, if cultivated in crop rotation, was shown to be an efficient alternative to silage maize as a biomass crop in order to achieve a higher diversity in biomass crop cultivation.

Response of Maize to the Integrated Use of Date Palm Compost and Mineral-N Fertilizer

Response of Maize to the Integrated Use of Date Palm Compost and Mineral-N Fertilizer

Replacing organic with mineral N fertilization does not reduce nitrate leaching in double crop forage systems under Mediterranean conditions

This research evaluated the impact of four nitrogen (N) fertilizer management systems on nitrate losses in an irrigated forage system under Mediterranean conditions within a Nitrate Vulnerable Zone (NVZ). The experiment was conducted from June 2009 to May 2012 in an intensive dairy cattle farm that produces silage maize and Italian ryegrass in a double cropping system. A monthly monitoring of the nitrate concentrations in the soil solution was carried out using 10cm diameter disk lysimeters. The N fertilization systems had a target N application of 316 and 130kgha−1 for maize and Italian ryegrass, respectively. Four systems were compared: cattle manure (MA); cattle slurry (SL); cattle slurry+mineral N fertilizer (SM); mineral N fertilization (MI). A clear seasonal dynamics of nitrate concentration was observed in the three years and was similar among treatments, with maximum occurring in autumn–winter. On average, at soil depths between 50 and 90cm, nitrate concentrations in the soil solution were intermediate for the MI treatment (146±10.4mgL−1), in between those of SL or SM (202±11.3 and 164±9.4mgL−1, respectively) and MA (78±4.9mgL−1). Despite the high average concentrations, only in some sampling dates the nitrate concentration was significantly higher than 50mgL−1. The estimated annual N leaching losses below 90cm soil depth ranged from 42 (MA) to 110 (SL)kgNha−1.These findings highlighted that, under Mediterranean conditions and with the N input rates, nitrate leaching in autumn–winter cannot be easily controlled through N fertilizer management because it is mainly associated to the natural water surplus and the low N uptake from the winter crop. The cattle manure has proved to be the most conservative in terms of N leaching, while replacing organic with mineral sources of N did not reduce nitrate leaching.