Soil Mineral Nitrogen Content Research Articles

The influence of biological preparations Azofix and Maxprolin and nitrogen fertilisation on soil mineral nitrogen content in growing season and after spring wheat harvest

The objective of the research reported here was to determine the effect of Azofix and Maxprolin against nitrogen fertiliser on mineral nitrogen content in the soil during the period of intensive growth of spring wheat plants and after its harvest. The following two factors were chosen: I. Biological products: control, Azofix, Maxprolin, Azofix + Maxprolin; II. Nitrogen fertilisation: non-fertilised control, 60 kg N ha–1, 90 kg N ha–1, 90 kg N ha–1 + foliar fertilisation. During the period of intensive growth of spring wheat plants and after harvesting, mineral nitrogen content in the soil was determined. The research demonstrated that, during the period of their intensive growth, spring wheat plants had access to the largest amount of mineral nitrogen in the topsoil following treatment with Azofix + Maxprolin and an application of the nitrogen rate of 90 kg N ha–1.

Modeling nitrous oxide emissions from agricultural soil incubation experiments using CoupModel

Abstract. Efforts to develop effective climate mitigation strategies for agriculture require methods to estimate nitrous oxide (N2O) emissions from soil. Process-based biogeochemical models have been often used for field- and large-scale estimates, while the sensitivity and uncertainty of model applications to incubation experiments are less investigated. In this study, a process-oriented model (CoupModel) was used to simulate N2O and CO2 fluxes and soil mineral nitrogen (N) contents in a short-term (43 d) factorial incubation experiment (16 treatments). A global sensitivity analysis (GSA) approach, “Morris screening”, was applied to quantify parameter sensitivity. The GSA suggested that a higher number of sensitive parameters was associated with N2O flux estimates and that inter-treatment variations in parameter sensitivities were distinguished by soil moisture levels or NO3- content and residue types. Important parameters regarding N2O flux estimates were linked to the decomposability of soil organic matter (e.g., organic C pool sizes) and the denitrification process (e.g., Michaelis constant and denitrifier respiratory rates). After calibration, the model better captured temporal variations and magnitude of gas fluxes and mineral N in unamended soils than in residue-amended soils. Low-magnitude daily and cumulative N2O fluxes were well simulated with mean errors (MEs) close to zero, but the model tended to underestimate N2O fluxes, as observed daily values increased by over 0.1 g N m−2 d−1, in which the major mismatch was due to limited success of the model to describe the high emissions during the first few days after crop residue addition. A larger uncertainty was also seen in the magnitude of pulse emissions by the posterior simulations. We also evaluated ancillary variables regarding N cycling, which indicated that more frequent measurements and additional types of observed data such as soil oxygen content and the microbial sources of emitted N2O are required to further evaluate model performance and biases. The major challenges for calibration were associated with high sensitivities of denitrification parameters to initial soil abiotic conditions and the instantaneous residue amendment. Model structure uncertainties and improved modeling practices in the context of incubation experiments were discussed.

Effects on soil nitrogen and plant production from land applying three types of biosolids to an agricultural field for three consecutive years

Land application of biosolids as a source of crop fertilizer and soil organic matter can be viewed as a sustainable approach to maintain soil productivity. Field-based experiments were conducted to examine the effects of three municipal biosolids (composted, liquid mesophilic anaerobically digested, and alkaline treated) on soil nitrogen dynamics and corn response, applied over three years in Nova Scotia, Canada. A total of fifteen treatments were evaluated in this study based on application management (surface vs. incorporation) of biosolids and the application of biosolids at a reduced rate with urea supplementation. Agronomic parameters were measured (corn yield and nitrogen uptake) and examined relative to the amendment rates to develop nutrient use efficiency indices. Our results indicate that soil pH was significantly increased by 1–1.5 pH units in alkaline treated biosolids (ATB) treatments under both application methods compared to liquid mesophilic anaerobically digested biosolids (LMAD), composted biosolids (COMP), urea, and an unamended soil control. The soil and plant responses were greatest for ATB>LMAD>COMP. Average soil mineral nitrogen (SMN) concentrations in surface applied biosolids ranged from 25.1 to 33.28 mg kg-1 in the three years of the study, but greater concentrations (33.27–39.39 mg kg-1) were observed when the biosolids were incorporated. The incorporation of biosolids also increased corn biomass yield by 18–33% and nitrogen uptake by 25–38% compared to the surface applied over three years.

Soil mineral nitrogen dynamics in fallow periods in a rainfed semiarid Mediterranean agricultural system

Rainfed agricultural systems in semiarid Mediterranean environments are subject to erratic but often heavy rainfall events. As an agronomic practice, fallow periods can be included even within the existing EU common policy for crop diversification. This research aimed to quantify the effects of a previous mineral fertilization on the soil mineral nitrogen (N min ) content and on potential nitrate leaching during no-tilled fallow periods of a crop rotation. Water and N min soil measurements obtained during three fallow seasons were used. Data were also used to check if the Leaching Estimation and Chemistry Model (LEACHM) can be used for the soil N min prediction after fallow. During these periods, the N min measured in the soil profile increased on average by 125 kg N ha -1 , while the model averaged an increase of 95 kg N ha -1 . The estimate of N leached ranged from 11 to 38 kg N ha -1 . The N balance simulated using LEACHM might differ from the actual processes. After a drought period followed by a soil water replenishment, the calibrated LEACHM underestimated soil N min probably due to the “Birch effect”. After occasional rainy spells when soil quickly became saturated, LEACHM overestimated soil N min probably due to occasional N 2 O emissions not being fully accounted by the model and to specific preferential water flow, which might produce a greater nitrate leaching than that simulated by LEACHM using the convection-dispersion equation . The results show that soil N min measurements by sampling after the fallow period cannot be replaced by LEACHM simulations. These samplings are of interest in fallow established inside a rotation and to avoid over-fertilization in the following cropping season, while reducing N environmental impacts.

Effects of shallow non-inversion tillage on sandy loam soil properties and winter rye yield in organic farming

Due to an expected improvement of soil quality and soil water storage, the substitution of mouldboard ploughing by reduced tillage was identified as a potential climate change adaptation measure for organic farming in a relatively dry region with a humid continental climate. In a field trial on a sandy loam soil in eastern Germany, reduced tillage was carried out to 6 cm soil depth by means of a ring cutter and compared to mouldboard ploughing with 25 cm tillage depth. In the present study, the influence of ring cutter tillage on soil properties was investigated for the first time. The effects of shallow ring cutter tillage on soil physical parameters, soil organic matter distribution, soil mineral nitrogen content, total nitrogen uptake by the crop, root content, and grain yield of organically grown winter rye (Secale cereale L.) were analysed in the uppermost 20 cm of a sandy loam soil and compared to those of mouldboard ploughing.Under ring cutter tillage, soil bulk density was in 8–20 cm soil depth by up to 15% higher than under mouldboard ploughing. In 9–15 cm soil depth, ring cutter tillage resulted in smaller contents of coarse macropores and mesopores, more micropores, and an 11% smaller available water capacity compared to mouldboard ploughing. The total nitrogen uptake by winter rye was in the ring cutter treatment by up to 44% smaller than in the mouldboard plough treatment. Root content was up to 209% higher in 1–6 cm soil depth and up to 71% smaller in 8–20 cm soil depth after ring cutter tillage than after mouldboard ploughing. Winter rye yield declined by 22–43% in the ring cutter treatment relative to the mouldboard plough treatment.Shallow ring cutter tillage resulted in a root growth-restricting soil compaction in the non-tilled soil layers below 6 cm depth and led to a limitation of nitrogen mineralisation until spring. Both effects likely caused the considerable reduction of crop yield. The results suggest that shallow ring cutter tillage in organic farming seems to be not suitable for sandy loam soils as long as the risk of a soil compaction-induced limitation of root growth and nitrogen supply cannot be minimised.

Improving the AquaCrop model to achieve direct simulation of evapotranspiration under nitrogen stress and joint simulation-optimization of irrigation and fertilizer schedules

Water and fertilizer management strategy profoundly influences crop yield, water and nitrogen use efficiency. In this study, a framework for joint simulation-optimization of irrigation and fertilizer schedules (JSOIFS) was established by coupling the improved AquaCrop model, W*N-Jensen model and multi-objective programming. Firstly, the AquaCrop model was modified to simulate evapotranspiration (ET) under nitrogen stress through introducing the concept of shoot actual, critical and minimal nitrogen concentration. The accuracy and applicability of the improved AquaCrop model to simulate ET were verified, taking seed maize of Shiyanghe River Basin as a case. On the basis, an optimization model with the objective of maximum yield calculated by W*N-Jensen model and water use efficiency was developed under the scenarios of different levels of available water and nitrogen, and initial soil mineral nitrogen content. Results showed that the improved model can simulate canopy cover (CC) and ET well with and without water stress. Meanwhile, the precision for CC, biomass, ET and yield of seed maize can be guaranteed when water and nitrogen stress coexist. It indicated that the improved model can be used for irrigation and fertilizer management. The optimal irrigation and fertilizer schedules pointed out that the irrigation and nitrogen application, and initial soil mineral nitrogen all have significant effects on yield. In low fertility soils, irrigation should be concentrated during tasseling stage and fertilization is as critical as irrigation. Conversely, in high fertility soils, irrigation should be dispersed throughout the growth period. Water and nitrogen use efficiency have been promoted compared with the status quo. The recommended water and nitrogen application for seed maize are 150–200 mm and 100–150 kg N/ha, respectively, in study area with the mean soil mineral nitrogen of 182 kg N/ha. The improvement of ET simulation performance of AquaCrop model under simultaneous stress of water and nitrogen provides convenience for achieving precise crop management. Meanwhile, the JSOIFS framework realizes the efficient irrigation and fertilizer schedules in arid areas, improves the resources use rate, and is equally applicable to other regions with the same goals.

P is for persistence: Soil phosphorus remains elevated for more than a decade after old field restoration.

Understanding constraints to ecological restoration on former agricultural land has become increasingly important due to agricultural land degradation in the developed world, and growing evidence for enduring agricultural legacies that limit native species recovery. In particular, the removal of native plant biomass and subsequent disturbance of soil properties through farming activities can alter soil ecosystem processes. Planting of native plant species is a common approach to restoring native vegetation on agricultural land and is assumed to benefit soil ecosystem processes, but the degree to which altered soil chemical processes recover is poorly documented. We investigated recovery of soil chemical properties after restoration in semiarid Western Australia, hypothesizing that elevated nutrient concentrations would gradually decline post planting, but available phosphorus (P) concentrations would remain higher than reference conditions. We used a space-for-time substitution approach, comparing 10 planted old field plots with matched fallow cropland and reference woodlands. Sampling on planted old fields and reference woodland plots was stratified into open patches and under tree canopy to account for consistent differences between these areas. The most prominent legacy of cropping was significantly and substantially higher concentrations of soil available P in fallow croplands and restored old fields compared with reference woodlands. Soil mineral nitrogen (N) concentrations were elevated in fallow croplands compared to open patches in reference woodlands (ammonium and nitrate) and under the tree canopy (ammonium). However, in restored old fields, mineral N concentrations were similar to woodland sites, providing evidence for amelioration over time. No significant differences in nutrient concentrations under tree canopies compared with open patches had developed in the planted old fields, despite a distinction between open patches and he under ttree canopy in reference woodlands for total N. We conclude that soil P legacies in old fields may inhibit the recolonization of native species that are sensitive to, or uncompetitive at, elevated P concentrations. To achieve full recovery, further research is required to test restoration practices aimed at reducing soil P concentrations to facilitate native plant establishment and persistence.

Contrasting ecological processes shape the Eucalyptus phyllosphere bacterial and fungal community assemblies

AbstractIntroductionPhyllosphere microbiome is intrinsically linked to plant performance and ecosystem functioning. However, our knowledge about the role of ecological processes in shaping the biogeography of different phyllosphere microbial communities is scarce.Materials and MethodsHere, we compared the biogeographic patterns of bacterial and fungal communities in phyllosphere samples of plants belonging to the genus of Eucalyptus of the Myrtaceae family collected from an over 4000 km transect. We investigated the relative importance of two major ecosystem processes (stochastic vs. deterministic) in shaping phyllosphere microbial community assemblies.ResultsOur results demonstrated that the neutral community model, which can quantify the degree of a community assembly determined by stochastic processes, explained 64.2% of the variations in bacterial community assembly, which had a normalized stochasticity ratio of 71.8%. These results suggest that the dominant role of stochastic processes in shaping bacterial community assembly. In contrast, phyllosphere fungal community assembly was mainly shaped by deterministic processes as revealed by a relatively small explanation rate of the neutral community model (48.7%) and a normalized stochasticity ratio of 25.1%. Variation partitioning analysis and random forest modelling results indicated that climatic factors, particularly mean annual precipitation and aridity index, were important in driving both bacterial and fungal biogeographic patterns in the phyllosphere. Edaphic factors, such as soil organic and mineral nitrogen content, were more closely related to fungal community assembly than to bacterial community assembly. The differential responses of bacterial and fungal communities to environmental factors could be attributed to the different traits of bacteria and fungi, that is, the higher potential dispersal rate and wider habitat niche of bacteria than fungi.ConclusionOur findings demonstrated that phyllosphere bacterial and fungal communities followed distinct community assembly processes, which is supported by the ‘size plasticity’ hypothesis that smaller organisms (bacteria) are less influenced by environmental conditions and are more homogeneous across space than larger organisms (fungi). These findings provide new insights into the microbial ecology of plant phyllosphere microbiomes.

Evaluating microbial role in reducing N2O emission by dual isotopocule mapping following substitution of inorganic fertilizer for organic fertilizer

Organic and inorganic fertilizers are major sources of N2O emission in vegetable field and their combined applications are recommended in China. However, the microbial processes for N2O production and consumption after combined applications of organic and inorganic fertilizers to vegetable field remain unclear making the optimal fertilization scheme less accurate. To address this issue, five substitution rates of organic fertilizer for inorganic fertilizer including 0 (0M), 20 (20M), 50 (50M), 80 (80M), and 100% (100M) and a no fertilizer control (NF) were evaluated on Chinese cabbage (Brassica pekinensis L. var). N2O fluxes, N2O isotopocule ratios, Chinese cabbage yield and environmental parameters were measured. According to the revised dual isotopocule mapping of δ18O vs. δ15NSP (difference value of 15N in Nα–Nβ–O molecule site preference), the nitrification contribution for the 100M, 80M, 50M, 20M, 0M and NF treatments were 41, 28, 33, 34, 39, and 37%, respectively, and the extent of N2O reduction were 74, 67, 48, 35, 11, and 78%, respectively. Such results suggest that denitrification was the major microbial process and was promoted by adding organic fertilizer. Increasing the substitution rates of organic fertilizer improved the extent of N2O reduction and thus mitigated N2O emission. In addition, increasing the substitution rates of organic fertilizer improved C/N ratio and N2O isotopocule deltas, yet reduced N2O emission, Chinese cabbage yield, and soil mineral nitrogen content. In all the evaluated substitution rates, the 20M treatment had the best performance in maintaining the Chinese cabbage yield and reducing the N2O emission. These findings reveal that the dual double isotopocule mapping is useful for partitioning N2O source and sink on a field scale. Adding organic fertilizer could reduce N2O emission by enhancing N2O reduction to N2 and the 20% substitution rate of organic fertilizer is the appropriate substitution rate. Furthermore, an optimal substitution rate of organic fertilizer should be explored between 20% and 50% in later studies.

Simplifying residual nitrogen (Nmin) sampling strategies and crop response

Globally, important nitrogen fertilizer decisions are often made at the early stages of plant development, when plants are not yet sufficiently indicative of their needs. Optimizing nitrogen fertilization of crops requires assessing the available soil mineral nitrogen content (Nmin) at the beginning of the season and was assessed exemplarily for wheat and maize. Since 2020 a mandatory soil Nmin analysis for each crop on a representative field is required in Germany in zones characterized by increased nitrate concentrations in the groundwater, encompassing approximately 28 % of the arable land. However, soil analysis is time-consuming, costly, and labor-intensive and requires further optimization beyond the current practice.In this study, wheat fields in 2018 and 2019 and maize fields in 2018 were sampled in a grid pattern in spring, and the soil nitrate-N content was determined in 30 cm layers down to 60 cm soil depth in 11 fields and further down to 90 cm soil depth in two of the fields. For each single and the combined soil depths, all fields could be sampled with a deviation of less than 10 kg nitrate-N ha−1 with only two soil samples. Overall, the reduced field-specific soil sampling strategy proved advantageous compared to crop-specific, regionally representative Nmin values offered by the official advisory authorities based on multiple averaged field investigations with an increased sampling intensity of 16 samples per field. Further, the reduced field-specific soil sampling strategy delivered more precise Nmin values by 11.2 kg nitrate-N ha−1 for wheat fields and slightly less precise values by 4.8 kg nitrate-N ha−1 for maize fields. The reduced field-specific soil sampling has great potential to reduce analysis and soil sampling costs. Nitrogen fertilization experiments supported the usefulness of the new simplified Nmin strategy. Multispectral in-season satellite imagery from Sentinel-2 could not adequately capture the spatial nitrate-N level differences and confirms soil samplings needs early in the season.Because most farmers base their fertilization strategy on regionally crop-specific aggregated Nmin values delivered by the official advisory system, we consider a simplified strategy to be more indicative of the field-specific soil Nmin status, which is eased by a markedly reduced sampling frequency and further simplifies the analysis by aggregating the separately analyzed soil depths to only one single depth. Further, currently available simplified on-farm analyses of the soil nitrate content allow for conducting more intensive field-specific soil Nmin analysis, thus contributing to improved nitrogen demand management and decreasing adverse environmental effects.

Soil microbes drive the effect of plant species and genotypic diversity interaction on productivity.

PurposeThe effect of plant species and genotypic diversity on productivity has been well documented but little is known about the contribution of the interaction between species and genotypic diversity. Since the influence of soil microorganisms on the plant diversity-productivity relationship is increasingly recognized, we investigated potential interactions between plant species diversity, plant genotypic diversity and soil microbes. We hypothesized that the non-additive effects of plant species and genotypic diversity on productivity could be microbe-driven.MethodsWe set up pea and wheat monocultures and mixtures in a growth chamber, varying for their levels of genotypic diversity under three different soil microbial contexts. We assessed plant shoot and root biomass production, soil mineral nitrogen content and described the soil bacterial communities.ResultsWe found that shoot biomass in mixtures involving both species and genotypic diversity was higher than expected considering the additive effects of plant species diversity and genotypic diversity. Rather than a synergy between two positive effects of species and genotypic diversity, we observed that species mixture compensated the negative effect of genotypic diversity. Regarding microbial influence, we found that the effect of plant species diversity, plant genotypic diversity and their interaction on productivity were all driven by the soil microbial community as no effect was observed in a pre-sterilised soil.ConclusionOur study suggests that the plant diversity-productivity relationship could be shaped by a three-way interaction between plant species diversity, plant genotypic diversity and soil microbes. Thus, plant-microbe and plant-plant interactions could be a determinant of the plant diversity-productivity relationship.

Effect of conservation tillage on yield of spring wheat (<i>Triticum aestivum</i> L.) and soil mineral nitrogen and carbon content

Effect of conservation tillage on yield of spring wheat (<i>Triticum aestivum</i> L.) and soil mineral nitrogen and carbon content

Effect of urea and polymer-coated urea on N content of soil and leaves of maize cultivated in Brazilian Cerrado

The development of technologies that provide rational and sustainable use of nitrogen fertilizers is among the priorities of agronomic research in 21st century. Therefore, the objective of this study was to evaluate the effects of conventional urea or polymer-coated urea (PCU) on soil mineral nitrogen (N) content, plant dry mass and leaf N content in maize (Zea mays L.), cultivated in two seasons (first and second-crop) and in two regions of the Brazilian Cerrado (Chapadão do Sul - MS and Selvíria - MS). The treatments consisted of the combination of two sources of N (conventional urea or polymer-coated urea) and five doses of N (0, 45, 90, 135 or 180 kg ha−1), in a randomized complete block design, with a 2 × 5 factorial scheme with four replications. The following parameters were evaluated: soil mineral N content (NH4+, NO3- and total mineral N), plant dry mass and leaf N content. Although the PCU did not change the NH4+, NO3- and total mineral N content in the soil, nor the dry mass of the plants, it provided, on average, higher N content in the leaves, when compared to CU. The increasing rates of N linearly increased the levels of NH4+, NO3- and total mineral N content in the soil, as well as the dry mass of the plants and the N content in the leaves, regardless of N source or study location.

生物炭添加对不同水氮条件下芦苇生长和氮素吸收的影响

生物炭能改良土壤从而促进植物生长和氮素吸收，但其作用效果是否受水氮条件的影响尚不清楚。以湿地植物芦苇为研究对象，在3种氮添加水平（无添加，30 kg hm^-2 a^-1和60 kg hm^-2 a^-1）和两种水分（淹水和非淹水）条件下分别进行生物炭添加和不添加处理，结果表明：（1）生物炭添加能促进芦苇根系生长，在非淹水条件下根系生物量增加了40.5%，在淹水条件下根系生物量增加了20.1%。（2）生物炭添加能促进非淹水条件下芦苇的氮素吸收，能提高淹水条件下芦苇的氮素生产力。（3）生物炭添加加剧了土壤氮素损失，且在非淹水高氮条件下作用最强，可能是由于生物炭促进了芦苇的氮素吸收。芦苇氮素吸收速率与土壤氮损失之间存在显著的正相关关系。因此，在添加生物炭时，需要考虑土壤水分状况和氮素富集程度以及植物的氮素吸收偏好。该研究结果可为生物炭在湿地生态系统中的应用提供参考。;Nitrogen is an essential element for plant growth and is closely related to plant life activities. In most terrestrial ecosystems, plant growth is limited by nitrogen availability. Therefore, it is important to improve plant productivity in terrestrial systems by increasing the nitrogen uptake capacity of plants. Biochar is regarded as a kind of soil conditioner produced by pyrolysis of biomass under high temperature and hypoxia conditions. It has attracted more and more attention because of its important role in promoting crop yield, reducing greenhouse gas emissions and environmental pollution control in recent years. Most previous studies have applied biochar in dryland ecosystems, but few in wetland ecosystem. Though biochar has been proved to be beneficial of plant growth and nitrogen uptake, but whether it is influenced by different nitrogen availability and water conditions is still unclear. Therefore, we conducted a greenhouse experiment to investigate the effects of biochar addition on the growth and nitrogen absorption of Phragmites australis with three nitrogen additions (no addition, 30 kg hm^-2 a^-1, 60 kg hm^-2 a^-1) and two water treatments (inundation and no inundation). The results showed that:(1) biochar addition promoted the root growth of P. australis, increased the root biomass by 40.5% in the non-flooded treatment and by 20.1% in the flooded treatment, but have no significant effects on biomass of other parts and total biomass. (2) Biochar addition could improve the nitrogen absorption rate in the non-flooded condition, increased the nitrogen absorption rate by 23% in average. Biochar addition also enhanced the nitrogen productivity of P. australis in the flooded condition by 22% in average. (3) Biochar significantly decreased the soil ammonium-N, nitrate-N and mineral nitrogen concentrations, increased the soil nitrogen loss, and the effects were the strongest in the non-flooded and high nitrogen treatments because biochar promoted nitrogen absorption rate of P. australis. There was a significantly positive correlation between nitrogen absorption rate of P. australis and soil nitrogen loss. Our study shows that biochar has different effects on growth, nitrogen absorption and utilization of P. australis in different soil nitrogen availability and water treatments, and the difference may be related to the absorption preference of plants on different nitrogen chemical forms. Therefore, it is necessary to comprehensive balance soil water status, nitrogen enrichment and nitrogen absorption preference of plants when applying biochar in field. This result can practically provide scientific support for the application of biochar in the wetland ecosystem.

Effects of Adapted N-Fertilisation Strategies on Nitrate Leaching and Yield Performance of Arable Crops in North-Western Germany

Groundwater pollution with nitrate is a big challenge for drinking water abstraction in regions with intensive agricultural land-use, specifically with high livestock densities on sandy soils in humid climates. Karst aquifers with high water flow velocities are extremely vulnerable to this problem. To cope with this situation, a field trial with an installation of ceramic suction cups under a randomised block design with a typical north-German cropping sequence of silage maize–winter wheat–winter barley was established in a karst water protection zone. Over three years, reduced nitrogen (N) application rates and N type (mineral or combined organic + mineral fertilisation) were tested for their effects on crop yields and leachate water quality below the root zone. Results showed no significant reductions in crop yields with 10/20% reduced N rates for cereals/maize and only slight reductions in cereal protein content. Nitrate concentration from adapted N rates was significantly lower in treatments with an application of organic fertilisers (−7.74 mg NO3-N l−1) with greatest potential after cultivation of maize; in only mineral fertilised plots the effect was smaller (−3.80 mg NO3-N l−1). Cumulative leaching losses were positively correlated with post-harvest soil mineral nitrogen content but even in unfertilised control plots losses >50 kg N ha−1 were observed in some crop-years. Reduced N rates led to decreased leaching losses of 14% (6.3 kg N ha−1 a−1) with mineral and 29% (20.1 kg N ha−1 a−1) with organic + mineral fertilisation on average overall cops and years. The presented study revealed the general potential of adapted fertilisation strategies with moderately reduced N applications (−10/−20%) to increase leachate water quality without affecting significantly crop yields. However, regionally typical after-effects from yearlong high N surpluses in livestock intensive farming systems are a limiting factor.

Preliminary Study of the Effect of Chemical and Organic Fertilizers on a Semi-Natural Grassland in Vlăhiţa, Harghita Mountains, Romania

AbstractThe aim of the research was to examine the effect of different fertilizers on the floristic composition and biomass yield of the semi-natural grassland used as hayfield near Vlăhița locality (Harghita County, Romania) in order to improve its management. In the same time the qualitative structure of the studied grassland was evaluated after the first application of the fertilizers. The vegetation survey was made before mowing, and a total of 84 plant taxa were identified. The studied plant community belongs to the associationFestuco-Agrostetum capillarisHorv. 1951. From the 31 fodder species, 13 had very good or good nutritional value. The qualitative structure analysis indicates that the vegetation has developed under moderate anthropogenic pressure. Beside the Euro-Asian elements the Circumpolar and the Cosmopolite elements were well represented. Many species with high tolerance for temperature, soil pH, and soil mineral nitrogen content were registered. After the first application of fertilizers in all treated plots the biodiversity increased compared to the control plot. Fertilized plots also had a significantly higher biomass yield than the control plot. All fertilizers reduced the proportion of the species with good nutritional value from the Poaceae family. Organic fertilizer affected positively the proportion of other plant families than Poaceae and Fabaceae. Long-term experiments are necessary to evaluate the response of the vegetation on treatment with organic fertilizer in order to optimize productivity of the hayfield and sustain species richness.

Higher biochar rate strongly reduced decomposition of soil organic matter to enhance C and N sequestration in nutrient-poor alkaline calcareous soil

Our knowledge of biochar as a tool for soil carbon (C) sequestration and soil quality in semi-arid regions remains limited in recent years. Moreover, there is a lack of understanding on the comparison between effects of biochar rates on soil organic C (SOC) and nitrogen (N) mineralization in organic C poor soils. Interactive effects of corncob-biochar (B), prepared at 450 °C pyrolysis temperature, and wheat straw (W) on soil native and fresh organic matter were investigated in sandy loam alkaline calcareous soil. The corncob-biochar was applied alone and in combination with wheat straw (WB) at rates equivalent to 0 t ha-1 (unamended control), 22.5 t ha-1 (B1, W1, W1B1), and 45 t ha-1 (B2, W2, W2B2). After treatment applications, soils were incubated under laboratory conditions for 61 days and periodic CO2 evolution rates were measured to calculate the cumulative CO2 efflux and priming effects. The lowest CO2 efflux was found in B2 treatment, whereas CO2 efflux was lower in W1B1 than in W1 treatment. Biochar alone and with wheat straw significantly reduced net C mineralization (NCM) compared to wheat straw only treatments and the effects became stronger as biochar rate increased. This was reflected in data on the priming effect, which also showed that increased biochar rates induced a stronger negative priming (− 87 to − 67%) on SOC. Biochar with wheat straw at both rates enhanced microbial biomass C (MBC) compared to the control, W1, B1, and B2 treatments. However, the W1B1 and W2B2 treatments decreased water-extractable organic C (WEOC) contents compared to W1 and W2. Microbial metabolic quotient (qCO2) and MBC/TOC ratio increased with biochar rate, suggesting more efficient utilization of labile C by microorganisms at higher biochar rate. Biochar alone and with wheat straw reduced soil mineral nitrogen (N) contents than the control treatment and resulted in net negative N mineralization or net N immobilization. Our findings indicate that biochar can reduce decomposition of soil organic matter to facilitate C and N sequestration in low organic C soils. However, our study also suggests the co-application of biochar and organic amendments/residues as labile C source to induce co-metabolism to improve microbial functions and C utilization efficiency in soils that are deficient in organic C.

Soil carbon balance by priming differs with single versus repeated addition of glucose and soil fertility level

Labile carbon (C) inputs strongly alter soil organic matter (SOM) turnover by priming, thus affecting soil C dynamics and soil fertility in the long term. The frequency of labile C inputs is expected to affect the intensity of priming effect. We evaluated the effects of single versus repeated additions of 13C-labeled glucose (with added 13C corresponding to 2% of soil organic C content) to five soils with increasing fertility level on the intensity of priming effect and soil C balance. Repeated glucose addition induced 61–108% greater C mineralization due to positive priming than the single addition in all soils. The intensity of priming effect declined with soil fertility level and mineral nitrogen (N) content, but increased with higher activities of N-acquisition enzymes (N-acetyl-glucosaminidase and leucine amino peptidase). Consequently, the decrease in N availability strongly increased the intensity of priming effect presumably by enhancing microbial N mining from SOM. Considering the C balance between SOM losses due to priming and glucose-C retention, glucose addition was responsible for net C losses in the low and moderate fertility soils (−14.0 to −0.30 mg C g−1 SOC after 14 weeks) but led to C gains in the high fertility soils (+0.44 to +4.36 mg C g−1 SOC). Greater retention of glucose-C was attributed to higher N availability and more intensive microbial growth, thus supporting microbial necromass formation and soil C sequestration. Compared to single addition, repeated glucose addition caused larger net C losses or lower C gains due to stronger SOM priming. In conclusion, the frequency of substrate addition and soil fertility are important regulators of SOM priming and the C balance. This knowledge should be informative to interpret soil C dynamics in response to labile C inputs in agroecosystems.

Influence of organic technology on vegetative growth and production of three climbing edible roses (Rosa sp.)

In the present study, three climbing edible roses (‘Crown Princess Margareta’, ‘Falstaff’ and ‘Brother Cadfael’) were evaluated for total vegetative growth and flowers production, besides correlations with soil microbiological and agrochemical parameters. The applied organic technology included a soil preparatory stage with three ameliorative plants (Sinapis alba L., Phacelia tanacetifolia L. and Tagetes patula L.) and two organic mulch variants (wood chips and wool) after plantation. In variant Sinapis and Tagetes, all three varieties of roses showed the highest values for parameters: total vegetative growth, number of shoots, average shoots length and flowers number. Significant positive correlations between biometric parameters and soil bacteria, phosphorus, mineral nitrogen, potassium (0-20 cm horizon) and humus (20-40 cm horizon) content were observed. Significant positive correlations between the number of flowers and the soil respiration coefficient, soil content in phosphorus, potassium, humus, total soluble salts and mineral nitrogen were noticed. Negative correlations with soil pH have been observed. Taking into account the data obtained in the two flowering stages in 2017, the average yield per hectare cultivated with ‘Crown Princess Margareta’ was 9.44 t petals/ha. For the ‘Falstaff’ and ‘Brother Cadafael’ cultivars, the yields were 7.54 and 5.62 t petals per hectare respectively.

Effects of different integration of water and fertilizer modes on the absorption and utilization of nitrogen fertilizer and fruit yield and quality of apple trees

We examined nitrogen use efficiency of 15N-urea of 15-year-old 'Gala' apple trees by broadcast fertilization (T1), nitrogen fertilization with drip irrigation (T2) and nitrogen fertilization with subsurface irrigation (T3), to further improve the water and fertilizer integration technology for apple orchard and to improve nitrogen utilization efficiency. The results showed that leaf area, chlorophyll, and leaf nitrogen content of leaves were significantly higher in T3 treatment than those in T1 and T2 treatments. Soil mineral nitrogen content (20-40 cm) in each period followed the order of T3>T2>T1, while that in 0-20 cm followed an order of T2>T3>T1. The Ndff value at organ level (the contribution rate of the 15N amount absorbed by various organs of the tree to the total nitrogen content of the organ) was the highest in T3 treatment in each period, followed by T2 and T1 treatments. The utilization rate of 15N in the fruit ripening period followed an order of T3>T2>T1. The 15N utilization rate of T3 reached 24.2%, being 1.19 and 1.65 times of T2 and T1, respectively. The 15N distribution rate in the fruits during the fruit maturity stage was the highest in T1 treatment, while that in the storage organs was the highest in T2 treatment and that in the reproduction organs was the highest in T3 treatment. The single fruit weight, yield, soluble solids, hardness, soluble sugar and sugar-acid ratio were the highest in T3 treatment, followed by T2 and T1 treatments. In summary, nitrogen application by percolation irrigation (subsurface application) significantly promoted leaf growth and nitrogen utilization of apple tree, and improved fruit yield and quality.