Application of zeolite improves water and nitrogen use efficiency while increasing essential oil yield and quality of Salvia officinalis under water-deficit stress

Soil moisture and nitrogen (N) are two of the most important factors affecting the production of medicinal plants. So, the management strategy of these factors is critical and to be identified. In order to study the application of zeolite (Z) (0 and 10 ton ha^?1) in S. officinalis culture medium under different irrigation regimes (30 % depletion of available soil water (ASW)) and 60 % depletion of ASW) and N (0, 75 and 150 kg N ha^?1) a split-factorial experiment was carried out with three replicates in 2018. The highest fresh and dry weight were achieved at irrigation after 30 % depletion of ASW while using 150 kg N ha^?1 and 10 ton Z ha^?1. Maximum water use efficiency (WUE) (22.10 g.L^-1) was obtained after 60 % depletion of ASW and 150 kg N ha^?1 and 10 ton Z ha^?1. Besides, the maximum nitrogen use efficiency (NUE) was obtained after 60 % depletion of ASW and 75 kg N ha^?1 and 10 ton Z ha^?1 (14.25 kg.kg^-1N). Maximum essential oil (EO) content (1.06%) and cis-Thujone were obtained from plants subjected to 60 % depletion of ASW and, application of 75 kg N ha^?1 and 10 ton Z ha^?1. Applying Z with N, in different irrigation regimes did improve soil conditions for achieving higher, WUE and NUE, increased the EO content and yield while decreasing the negative effects from water-deficit stress and has provided a direction towards a stable system.     

Revegetation and reclamation of soils using wild leguminous shrubs in cold semiarid Mediterranean conditions: Litterfall and carbon and nitrogen returns under two aridity regimes

This study was designed to evaluate the litter produced by Mediterranean shrub legumes subjected to two conditions of aridity. Seasonal litterfall patterns and litter chemistry showed no significant variation with soil aridity. The effects of aridity on the amount of litter produced were related to the plant species. A higher availability of water led to a 110% increase in litter production by Colutea arborescens (3191 vs. 1516 kg ha^–1) and to a 24% increase for Medicago strasseri (5288 vs. 4258 kg ha^–1). The litter provided by Colutea cilicica failed to significantly increase (1651 vs. 1825 kg ha^–1) in less arid conditions. In our experimental conditions, Dorycnium hirsutum showed high mortality and scarce persistence. In general, the litter supplied by these shrub legumes was low in lignin and showed high levels of easily degradable organic-C. Its N content, in the range 18 to 26.5 g kg^–1, was similar to that described by others for multipurpose tropical legumes. Under the semi-arid conditions of central Spain, C. arborescens and C. cilicica gave rise to potential yearly returns of 662 and 693 kg ha^–1 organic-C, and 35 and 44 kg ha^–1 N, respectively. M. strasseri provided a yearly organic-C return (1742 kg ha^–1) similar to that of a mature Mediterranean wood, and to a potential N return (78 kg ha^–1) that substantially exceeded this reference. Compared to the sclerophyllous species typical of the Mediterranean environment, shrub legumes show a much greater potential for enhancing N and organic-C levels, and consequently, for improving the biological activity of degraded soils. This feature is thought to be associated with the rapid and constant renewal of their leaves and their ability to provide the soil with other easily degraded materials.     

Biomass and nutrient stock of submersed and floating macrophytes in shallow lakes formed by rewetting of degraded fens

Ecosystem restoration by rewetting of degraded fens led to the new formation of large-scale shallow lakes in the catchment of the River Peene in NE Germany. We analyzed the biomass and the nutrient stock of the submersed (Ceratophyllum demersum) and the floating macrophytes (Lemna minor and Spirodela polyrhiza) in order to assess their influence on temporal nutrient storage in water bodies compared to other freshwater systems. Ceratophyllum demersum displayed a significantly higher biomass production (0.86–1.19 t DM = dry matter ha⁻¹) than the Lemnaceae (0.64–0.71 t DM ha⁻¹). The nutrient stock of submersed macrophytes ranged between 28–44 kg N ha⁻¹ and 8–12 kg P ha⁻¹ and that of floating macrophytes between 14–19 kg N ha⁻¹ and 4–5 kg P ha⁻¹ which is in the range of waste water treatment plants. We found the N and P stock in the biomass of aquatic macrophytes being 20–900 times and up to eight times higher compared to the nutrient amount of the open water body in the shallow lakes of rewetted fens (average depth: 0.5 m). Thereafter, submersed and floating macrophytes accumulate substantial amounts of dissolved nutrients released from highly decomposed surface peat layers, moderating the nutrient load of the shallow lakes during the growing season from April to October. In addition, the risk of nutrient loss to adjacent surface waters becomes reduced during this period. The removal of submersed macrophytes in rewetted fens to accelerate the restoration of the low nutrient status is discussed.     

Response of Arbuscular Mycorrhizal Fungi on Wheat (Triticum aestivum L.) Grown Conventionally and on Beds in a Sandy Loam Soil

The present study was undertaken to assess the benefit and compare the functioning of AM fungi on wheat grown conventionally and on beds. Ten treatment combinations were used, treatments 1 and 2: no fertilizers with and without arbuscular mycorrhizal (AM) fungi (In vitro produced Glomus intraradices); 3:100% of recommended NPK: (120 kg ha⁻¹ N; 60 kg ha⁻¹ P; 50 kg ha⁻¹ K), and 4 and 5: 75% of recommended NPK dose with and without AM inoculation in a 5 × 2 split-plot design on wheat using conventional/flat system and elevated/raised bed system. The maximum grain yield (3.84 t ha⁻¹) was obtained in AM fungi inoculated plots of raised bed system applied with 75% NPK and was found higher (although non- significant) than the conventional (3.73 t ha⁻¹) system. The AM inoculation at 75% fertilizer application can save 8.47, 5.38 kg P and 16.95, 10.75 kg N ha⁻¹, respectively, in bed and conventional system. While comparing the yield response with 100% fertilizer application alone, AM inoculation was found to save 20.30, 15.79 kg P and 40.60, 31.59 kg N ha⁻¹, respectively, in beds and conventional system. Mycorrhizal inoculation at 75% NPK application particularly in raised bed system seems to be more efficient in saving fertilizer inputs and utilizing P for producing higher yield and growth unlike non-mycorrhizal plants of 100% P. Besides the yield, mycorrhizal plants grown on beds had higher AM root colonization, soil dehydrogenases activity, and P-uptake. The present study indicates that the inoculation of AM fungi to wheat under raised beds is better response (although non-significantly higher) to conventional system and could be adopted for achieving higher yield of wheat at reduced fertilizer inputs after field validation.     

Evaluation of nutrient retention in four restored Danish riparian wetlands

During the last 15–20 years, re-establishment of freshwater riparian wetlands and remeandering of streams and rivers have been used as a tool to mitigate nutrient load in downstream recipients in Denmark. The results obtained on monitoring four different streams and wetland restoration projects are compared with respect to hydrology, i.e. flow pattern and discharge of ground or surface water, retention of phosphorus (P), and removal of nitrogen (N). Furthermore, the monitoring strategies applied for quantifying the post-restoration nutrient retention are evaluated. The four wetland restoration projects are the Brede River restoration (including river valley groundwater flow, remeandering and inundation), Lyngbygaards River restoration (groundwater flow, irrigation with drainage water, inundation with river water and remeandering), Egeskov fen (fen re-establishment and stream remeandering) and Egebjerg Meadows (fen restoration and hydrological reconnection to Store Hansted River). Retention of phosphorus varied between 0.13 and 10 kg P ha⁻¹ year⁻¹, while the removal of nitrogen varied between 52 and 337 kg N ha⁻¹ year⁻¹. The monitoring strategy chosen was not optimal at all sites and would have benefitted from a knowledge on local hydrology and water balances in the area to be restored before planning for the final monitoring design. Furthermore, the outcome concerning P retention would have benefitted from a more frequent sampling strategy.     

Impact of long-term nitrogen addition on carbon stocks in trees and soils in northern Europe

The aim of this study was to quantify the effects of fertiliser N on C stocks in trees (stems, stumps, branches, needles, and coarse roots) and soils (organic layer +0–10 cm mineral soil) by analysing data from 15 long-term (14–30 years) experiments in Picea abies and Pinus sylvestris stands in Sweden and Finland. Low application rates (30–50 kg N ha⁻¹ year⁻¹) were always more efficient per unit of N than high application rates (50–200 kg N ha⁻¹ year⁻¹). Addition of a cumulative amount of N of 600–1800 kg N ha⁻¹ resulted in a mean increase in tree and soil C stock of 25 and 11 kg (C sequestered) kg⁻¹ (N added) (“N-use efficiency”), respectively. The corresponding estimates for NPK addition were 38 and 11 kg (C) kg⁻¹ (N). N-use efficiency for C sequestration in trees strongly depended on soil N status and increased from close to zero at C/N 25 in the humus layer up to 40 kg (C) kg⁻¹ (N) at C/N 35 and decreased again to about 20 kg (C) kg⁻¹ (N) at C/N 50 when N only was added. In contrast, addition of NPK resulted in high (40–50 kg (C) kg⁻¹ (N)) N-use efficiency also at N-rich (C/N 25) sites. The great difference in N-use efficiency between addition of NPK and N at N-rich sites reflects a limitation of P and K for tree growth at these sites. N-use efficiency for soil organic carbon (SOC) sequestration was, on average, 3–4 times lower than for tree C sequestration. However, SOC sequestration was about twice as high at P. abies as at P. sylvestris sites and averaged 13 and 7 kg (C) kg⁻¹ (N), respectively. The strong relation between N-use efficiency and humus C/N ratio was used to evaluate the impact of N deposition on C sequestration. The data imply that the 10 kg N ha⁻¹ year⁻¹ higher deposition in southern Sweden than in northern Sweden for a whole century should have resulted in 2.0 ± 1.0 (95% confidence interval) kg m⁻² more tree C and 1.3 ± 0.5 kg m⁻² more SOC at P. abies sites in the south than in the north for a 100-year period. These estimates are consistent with differences between south and north in tree C and SOC found by other studies, and 70–80% of the difference in SOC can be explained by different N deposition.     

Biochar in Combination with Nitrogen Fertilizer is a Technique: To Enhance Physiological and Morphological Traits of Rice (Oryza sativa L.) by Improving Soil Physio-biochemical Properties

The over use of synthetic nitrogen (N) fertilizers is the major anthropogenic cause of low N-use efficiency and environmental damage in wetland rice production. Biochar (B) addition to soil is suggested as a climate change mitigation tool that supports carbon sequestration and reduces N losses and greenhouse gas emissions from the soil. Therefore, this study assessed the effect of four levels of B (0, 10, 20 and 30 t ha^?1) combined with two levels of N (135 and 180 kg ha^?1) on soil health, roots dynamics, physiological attributes, and yield components of rice. The addition of B at 30 t ha^?1 combined with 135 N kg ha^?1 increased chlorophyll content, net photosynthetic rate, biomass, and grain yield by 104%, 64%, 12%, and 30%, respectively, over control. Further, root traits such as total root length (TRL), total root volume (TRV), total root surface area (TRSA), and total average root diameter (TARD) were improved under 30 t ha^?1 combined with 135 N kg ha^?1 by 20%, 13%, 13%, and 25%, respectively, than non-biochar treatment under lower N application. Improvements in these traits resulted from higher N uptake due to improved soil physiochemical properties and soil microbial biomass combined with biochar. Interestingly, enhanced N metabolizing enzyme activities, including nitrate reductase (NR), glutamine synthetase (GS), and glutamine oxoglutarate aminotransferase (GOGAT) in biochar-treated plots, further supported the increases in these traits. Our results revealed that the integration of 30 t B ha^?1 with 135 kg N ha^?1 is a favorable option for enhancing soil health and rice grain yield.

     

Soil Inorganic N Leaching in Edges of Different Forest Types Subject to High N Deposition Loads

We report on soil leaching of dissolved inorganic nitrogen (DIN) along transects across exposed edges of four coniferous and four deciduous forest stands. In a 64-m edge zone, DIN leaching below the main rooting zone was enhanced relative to the interior (at 128 m from the edge) by 21 and 14 kg N ha⁻¹ y⁻¹ in the coniferous and deciduous forest stands, respectively. However, the patterns of DIN leaching did not univocally reflect those of DIN throughfall deposition. DIN leaching in the first 20 m of the edges was lower than at 32–64 m from the edge (17 vs. 36 kg N ha⁻¹ y⁻¹ and 15 vs. 24 kg N ha⁻¹ y⁻¹ in the coniferous and deciduous forests, respectively). Nitrogen stocks in the mineral topsoil (0–30 cm) were, on average, 943 kg N ha⁻¹ higher at the outer edges than in the interior, indicating that N retention in the soil is probably one of the processes involved in the relatively low DIN leaching in the outer edges. We suggest that a complex of edge effects on biogeochemical processes occurs at the forest edges as a result of the interaction between microclimate, tree dynamics (growth and litterfall), and atmospheric deposition of N and base cations.     

Optimizing nitrogen supply promotes biomass,physiological characteristics and yield components of soybean (Glycine max L. Merr.)

Avoidable or inappropriate nitrogen (N) fertilizer rates harmfully affect the yield production and ecological value. Therefore, the aims of this study were to optimize the rate and timings of N fertilizer to maximize yield components and photosynthetic parameter of soybean. This field experiment consists of five fertilizer N rates: 0, 75, 150, 225 and 300 kg N ha⁻¹ arranged in main plots and four N fertilization timings: V₅ (trifoliate leaf), R₂ (full flowering stage) and R₄ (full poding stage), and R₆ (full seeding stage) growth stages organized as subplots. Results revealed that 225 kg N ha⁻¹ significantly enhanced grain yield components, total chlorophyll (Chl), photosynthetic rate (P_N), and total dry biomass and N accumulation by 20%, 16%, 28%, 7% and 12% at R₄ stage of soybean. However, stomatal conductance (g_s), leaf area index (LAI), intercellular CO₂ concentration (Ci) and transpiration rate (E) were increased by 12%, 88%, 10%, 18% at R₆ stage under 225 kg N ha⁻¹. Grain yield was significantly associated with photosynthetic characteristics of soybean. In conclusion, the amount of nitrogen 225 kg ha⁻¹ at R₄ and R₆ stages effectively promoted the yield components and photosynthetic characteristics of soybean.     

N:P Ratio and the Nature of Nutrient Limitation in Calluna-Dominated Heathlands

There is growing evidence from different sources that prolonged high N deposition causes a shift from nitrogen (N) limitation to nitrogen and phosphorus (P) co-limitation or even P limitation in many terrestrial ecosystems. However, the number of ecosystems where the type of limitation has been directly tested by longer-term full-factorial field experiments is very limited. We conducted a 5-year fertilization experiment with N and P in the Lüneburger Heide (NW Germany) to test the hypothesis that, following decades of elevated atmospheric N inputs, plant growth in dry lowland heaths may have shifted from N to N–P co-limitation or P limitation. We also tested whether the plant tissue N:P ratio reflects the type of nutrient limitation in a continental lowland heathland. Experimental plots dominated by Calluna vulgaris received regular additions of N (50 kg N ha⁻¹ y⁻¹), P (20 kg P ha⁻¹ y⁻¹), a combination of both, or water only (control) from 2004 to 2008. Over the whole study period, a highly significant positive N effect on shoot length was found, thus indicating N limitation. We conclude that a clear shift from N limitation to N–P co-limitation or P limitation has not yet occurred. Tissue N:P ratios showed a high temporal variability and no relationship between tissue N:P ratio and the shoot length response of Calluna to nutrient addition was found. The N:P tool is thus of limited use at the local scale and within the range of N:P ratio observed in this study, and should only be used as a rough indicator for the prediction of the type of nutrient limitation in lowland heathland on a larger geographical scale with a broader interval of N:P ratio.     

Nitrogen fixation and N transfer from peanut to rice cultivated in aerobic soil in an intercropping system and its effect on soil N fertility

The novel cultivation of paddy rice in aerobic soil reveals the great potential not only for water-saving agriculture, but also for rice intercropping with legumes and both are important for the development of sustainable agriculture. A two-year field experiment was carried out to investigate the yield advantage of intercropping peanut (Arachis hypogaea L., Zhenyuanza 9102) and rice (Oryza sativa L., Wuyujing 99-15) in aerobic soil, and its effect on soil nitrogen (N) fertility. A pot experiment was also conducted to examine the N₂-fixation by peanut and N transfer from peanut to rice at three N fertilizer application rates, i.e., 15, 75 and 150 kg N ha^–1 using a ¹⁵N isotope dilution method. The results showed that the relative advantage of intercropping, expressed as land equivalent ratio (LER), was 1.41 in 2001 and 1.36 in 2002. Both area-adjusted yield and N content of rice were significantly increased in the intercropping system while those of peanut were not significantly different between intercropping and monocropping systems. The yields of rice grain and peanut, for example, were increased by 29–37% and 4–7% in the intercropping system when compared to the crop grown in the monocropping system. The intercropping advantage was mainly due to the sparing effect of soil inorganic N contributed by the peanut. This result was proved by the higher soil mineral N concentration under peanut monocropping and intercropping than under the rice monocropping system.%Ndfa (nitrogen derived from atmosphere) by peanut was 72.8, 56.5 and 35.4% under monocropping and 76.1, 53.3 and 50.7% under the intercropping system at N fertilizer application rates of 15, 75 and 150 kg ha^–1, respectively. The ¹⁵N-based estimates of N transfer from peanut (%NTFL) was 12.2, 9.2 and 6.2% at the three N fertilizer application rates. N transferred from peanut accounted for 11.9, 6.4 and 5.5% of the total N accumulated in the rice plants in intercropping at the same three N fertilizer application rates, suggesting that the transferred N from peanut in the intercropping system made a contribution to the N nutrition of rice, especially in low-N soil.     

Nitrogen Transformations in Flowpaths Leading from Soils to Streams in Amazon Forest and Pasture

The modification of large areas of tropical forest to agricultural uses has consequences for the movement of inorganic nitrogen (N) from land to water. Various biogeochemical pathways in soils and riparian zones can influence the movement and retention of N within watersheds and affect the quantity exported in streams. We used the concentrations of NO₃ ⁻ and NH₄ ⁺ in different hydrological flowpaths leading from upland soils to streams to investigate inorganic N transformations in adjacent watersheds containing tropical forest and established cattle pasture in the southwestern Brazilian Amazon Basin. High NO₃ ⁻ concentrations in forest soil solution relative to groundwater indicated a large removal of N mostly as NO₃ ⁻ in flowpaths leading from soil to groundwater. Forest groundwater NO₃ ⁻ concentrations were lower than in other Amazon sites where riparian zones have been implicated as important N sinks. Based on water budgets for these watersheds, we estimated that 7.3–10.3 kg N ha⁻¹ y⁻¹ was removed from flowpaths between 20 and 100 cm, and 7.1–10.2 kg N ha⁻¹ y⁻¹ was removed below 100 cm and the top of the groundwater. N removal from vertical flowpaths in forest exceeded previously measured N₂O emissions of 3.0 kg N ha⁻¹ y⁻¹ and estimated emissions of NO of 1.4 kg N ha⁻¹ y⁻¹. Potential fates for this large amount of nitrate removal in forest soils include plant uptake, denitrification, and abiotic N retention. Conversion to pasture shifted the system from dominance by processes producing and consuming NO₃ ⁻ to one dominated by NH₄ ⁺, presumably the product of lower rates of net N mineralization and net nitrification in pasture compared with forest. In pasture, no hydrological flowpaths contained substantial amounts of NO₃ ⁻ and estimated N removal from soil vertical flowpaths was 0.2 kg N ha⁻¹ y⁻¹ below the depth of 100 cm. This contrasts with the extent to which agricultural sources dominate N inputs to groundwater and stream water in many temperate regions. This could change, however, if pasture agriculture in the tropics shifts toward intensive crop cultivation.     

Direct and residual effects of nitrogen fertilization, foliar application of potassium and plant growth retardant on Egyptian cotton growth, seed yield, seed viability and seedling vigor

In order to obtain high productivity for a cotton crop, one of the major requirements is to establish an adequate plant population. The use of good-quality seed may ultimately be the best approach to attain this goal problem. The objective of this research was to study the effect of N-fertilization (at rates of 95.2 and 142.8 kg of N ha⁻¹), foliar application of K (at rates of 0, 0.38, 0.77, 1.15 kg of K₂O ha⁻¹, applied twice during square initiation and boll development stages) and the plant growth retardant (PGR), mepiquat chloride (applied twice, 75 days after planting at 0.0 [control] and 0.048 kg a.i. ha⁻¹, and 90 days after planting at 0.0 [control] and 0.024 kg a.i. ha⁻¹), on seed yield, viability, and seedling vigor of Egyptian cotton (Gossypium barbadense cv. Giza 86). A field experiment was conducted at the Agricultural Research Center, Giza, Egypt in two growing seasons. Growth, mineral uptake, seed yield per plant and per ha, seed weight, seed viability, seedling vigor and cool germination test performance were all found to increase significantly due to the addition of the high N-rate, the foliar application of three potassium concentrations, and the PGR mepiquat chloride. The N and K rates as well as application of mepiquat chloride had no significant effect on the germination rate index in both seasons. Under the conditions of this study, applying N at a rate of 142.8 kg ha⁻¹ combined with spraying cotton plants with K₂O at 1.15 kg ha⁻¹ and with mepiquat chloride at 0.048 + 0.024 kg ha⁻¹ were found to improve seed yield as well as seed viability and seedling vigor in the next season.     

Anthropogenic nitrogen enrichment enhances soil carbon accumulation by impacting saprotrophs rather than ectomycorrhizal fungal activity

There is evidence that anthropogenic nitrogen (N) deposition enhances carbon (C) sequestration in boreal forest soils. However, it is unclear how free‐living saprotrophs (bacteria and fungi, SAP) and ectomycorrhizal (EM) fungi responses to N addition impact soil C dynamics. Our aim was to investigate how SAP and EM communities are impacted by N enrichment and to estimate whether these changes influence decay of litter and humus. We conducted a long‐term experiment in northern Sweden, maintained since 2004, consisting of ambient, low N additions (0, 3, 6, and 12 kg N ha^?1 year^?1) simulating current N deposition rates in the boreal region, as well as a high N addition (50 kg N ha^?1 year^?1). Our data showed that long‐term N enrichment impeded mass loss of litter, but not of humus, and only in response to the highest N addition treatment. Furthermore, our data showed that EM fungi reduced the mass of N and P in both substrates during the incubation period compared to when only SAP organisms were present. Low N additions had no effect on microbial community structure, while the high N addition decreased fungal and bacterial biomasses and altered EM fungi and SAP community composition. Actinomycetes were the only bacterial SAP to show increased biomass in response to the highest N addition. These results provide a mechanistic understanding of how anthropogenic N enrichment can influence soil C accumulation rates and suggest that current N deposition rates in the boreal region (≤12 kg N ha^?1 year^?1) are likely to have a minor impact on the soil microbial community and the decomposition of humus and litter.     

Nitrous oxide emissions from silage maize fields under different mineral nitrogen fertilizer and slurry applications

Intensive dairy farming systems are a large source of emission of the greenhouse gas nitrous oxide (N₂O), because of high nitrogen (N) application rates to grasslands and silage maize fields. The objective of this study was to compare measured N₂O emissions from two different soils to default N₂O emission factors, and to look at alternative emission factors based on (i) the N uptake in the crop and (ii) the N surplus of the system, i.e., N applied minus N uptake by the crop. Twelve N fertilization regimes were implemented on a sandy soil (typic endoaquoll) and a clay soil (typic endoaquept) in the Netherlands, and N₂O emissions were measured throughout the growing season. Highest cumulative fluxes of 1.92 and 6.81 kg N₂O-N ha^–1 for the sandy soil and clay soil were measured at the highest slurry application rate of 250 kg N ha^–1. Background emissions from unfertilized soils were 0.14 and 1.52 kg N₂O-N ha^–1 for the sandy soil and the clay soil, respectively. Emission factors for the sandy soil averaged 0.08, 0.51 and 0.26% of the N applied via fertilizer, slurry, and combinations of both. For the clay soil, these numbers were 1.18, 1.21 and 1.69%, respectively. Surplus N was linearly related to N₂O emission for both the sandy soil (R²=0.60) and the clay soil (R²=0.40), indicating a possible alternative emission factor. We concluded that, in our study, N₂O emission was not linearly related to N application rates, and varied with type and application rate of fertilizer. Finally, the relatively high emission from the clay soil indicates that background emissions might have to be taken into account in N₂O budgets.     

Comparison of maize,permanent cup plant and a perennial grass mixture with regard to soil and water protection

Agricultural production of biogas maize (Zea mays L.) causes hazards to aquatic ecosystems through high levels of nitrogen (N) inputs. Newly introduced and already established perennial crops such as the cup plant (Silphium perfoliatum L.) and perennial grass mixtures offer the possibility of more environmentally friendly agricultural bioenergy production. The objectives of this field study were to quantify and compare soil mineral N, water infiltration, water runoff, soil erosion and N leaching under maize, permanent cup plant, and a perennial grass mixture. The study was conducted from October 2016 to March 2019 in Braunschweig, Germany. Plots with cup plant and grass mixture exhibited lower mineral N contents than maize, especially between 30 and 90 cm soil depth. Soil water infiltration was significantly different between the three crops. The grass mixture had the highest infiltration rates (6.2 mm/min averaged across 3 years), followed by cup plant (3.6 mm/min) and maize (0.9 mm/min). During wet periods, higher N leaching was found for maize (up to 42 kg N ha^?1 year^?1) than for cup plant (up to 5 kg N ha^?1 year^?1) or the grass mixture (up to 11 kg N ha^?1 year^?1). While runoff and erosion for cup plant and the grass mixture were negligible during the study period, considerable amounts of runoff water and eroded sediment of up to 1.5 Mg ha^?1 year^?1 were collected from the maize plots despite the near flat terrain of the experimental field. Overall, permanent cup plant proved suitable as a component for energy cropping systems to reduce the risk of N leaching and soil erosion, which is particularly important for the preventive flood protection in view of the more frequent occurrence of high intensity rainfall under climate change conditions.     

Impact of nitrogen cycling on stream water quality in a basin associated with forest, grassland, and animal husbandry, Hokkaido, Japan

The direct discharge of wastes from agricultural fields and livestock feedlots increases the concentration of nitrogen (N) in streams. This study was conducted to determine the impact of farm N budgets on stream water quality. In 1999–2000, we investigated an experimental livestock farm of 457 ha in the Kepau River watershed in Shizunai, Southern Hokkaido, Japan, where grasslands and maize fields account for 33% of the farm's total area. Annual N flow was calculated on the basis of the farm's land management records. Livestock was supplied with 15.2 t N yr⁻¹ from agricultural lands, which made the farm 81% self-sufficient. Livestock excreta produced 17.2 t N yr⁻¹, of which 4 t N yr⁻¹ was lost, probably by ammonia volatilization during decomposition. Apart from manure, the major N inputs were 9.1 t N yr⁻¹ of chemical fertilizers, 6.4 t N yr⁻¹ of atmospheric deposition, and 12.6 t N yr⁻¹ biological N fixation. The major outputs were uptake by forest vegetation of 11.0 t N yr⁻¹, denitrification of 1.5 t N yr⁻¹, and livestock feed production. Consequently, the annual surplus N on the whole farm was estimated to be 12.7 t N yr⁻¹, which corresponds to 28 kg N ha⁻¹ of agricultural land.The annual N load from the farm to the Kepau River was measured at 14.4 t N yr⁻¹. Ninety percent of this load, however, occurred during rainfall and spring snowmelt. Within one 2-week snowmelt period, 5.0 t N was discharged, which corresponds to 35% of the annual load. Although the average N concentration of stream water below the farm was 2.8 mg N L⁻¹, the maximum concentration recorded during the snowmelt season was 13.5 mg N L⁻¹. The N concentration of the stream water increased and the silica (Si) concentration decreased as the stream flow rate increased. Consequently, the molar ratio of Si/N frequently dropped below 2.7, the critical level for the occurrence of eutrophication. The large N load during rainfall and snowmelt could be ascribed to open ditches, which collect tile drainage and surface runoff from the fields, discharging it directly to the river, bypassing the forested riparian zone.     

Long-term effects of drainage and hay-removal on nutrient dynamics and limitation in the Biebrza mires,Poland

To provide a reference for wetlands elsewhere we analysed soil nutrients and the vegetation of floodplains and fens in the relatively undisturbed Biebrza-valley, Poland. Additionally, by studying sites along a water-table gradient, and by comparing pairs of mown and unmown sites, we aimed with exploring long-term effects of drainage and annual hay-removal on nutrient availabilities and vegetation response. In undrained fens and floodplains, N mineralization went slowly (0–30 kg N ha⁻¹ year⁻¹) but it increased strongly with decreasing water table (up to 120 kg N ha⁻¹ year⁻¹). Soil N, P and K pools were small in the undisturbed mires. Drainage had caused a shift from fen to meadow species and the disappearance of bryophytes. Biomass of vascular plants increased with increasing N mineralization and soil P. Annual hay-removal tended to have reduced N mineralization and soil K pools, but it had increased soil P. Moreover, N concentrations in vascular plants were not affected, but P and K concentrations and therefore N:P and N:K ratios tended to be changed. Annual hay-removal had induced a shift from P to K limitation in the severely drained fen, and from P to N limitation in the floodplain. The low nutrient availabilities and productivity of the undisturbed Biebrza mires illustrate the vulnerability of such mires to eutrophication in Poland and elsewhere. In nutrient-enriched areas, hay removal may prevent productivity increase of the vegetation, but also may severely alter N:P:K stoichiometry, induce K-limitation at drained sites, and alter vegetation structure and composition.     

Nitrogen-molybdenum-manganese co-fertilization reduces nitrate accumulation and enhances spinach (Spinacia oleracea L.) yield and its quality

Spinach (Spinacia oleracea L.) is considered a nitrogen (N) intensive plant with high nitrate (NO₃^?) accumulation in its leaves. The current study via a two-year field trial introduced an approach by combining N fertilization from different sources (e.g., ammonium nitrate; 33.5 % N, and urea; 48 % N) at different rates (180, and 360 kg N ha^?1) with the foliar spraying of molybdenum (Mo) as sodium molybdate, and/or manganese (Mn) as manganese sulphate at rates of 50 and 100 mgL^?1 of each or with a mixture of Mo and Mn at rates of 50 and 50 mg L^?1, respectively on growth, chemical constituents, and NO₃^? accumulation in spinach leaves. Our findings revealed that the highest rate of N fertilization (360 kg N ha^?1) significantly increased most of the measured parameters e.g., plant length, fresh and dry weight plant^?1, number of leaves plant^?1, leaf area plant^?1, leaf pigments (chlorophyll a, b and carotenoids), nutrients (N, P, K, Fe, Mn, Zn), total soluble carbohydrates, protein content, net assimilation rate, and NO₃^? accumulation, but decreased leaf area ratio and relative growth rate. Moreover, plants received urea-N fertilizer gave the highest values of all previous attributes when compared with ammonium nitrate –N fertilizers, and the lowest values of NO₃^? accumulation. The co-fertilization of N-Mo-Mn gave the highest values in all studied attributes and the lowest NO₃^? accumulation. The best treatment was recorded under the treatment of 360 kg N-urea ha^?1 in parallel with the combined foliar application of Mo and Mn (50 + 50 mg L^?1). Our findings proposed that the co-fertilization of N-Mo-Mn could enhance spinach yield and its quality, while reducing NO₃^? accumulation in leaves, resulting agronomical, environmental and economic benefits.