Mineral Nitrogen Content Research Articles

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.

Meat Processing Waste as a Source of Nutrients and Its Effect on the Physicochemical Properties of Soil

The aim of this study was to determine the effect of meat processing waste applied in the form of meat and bone meal (MBM) as a source of nutrients on the physicochemical properties of soil. A short–term small–area field experiment using MBM in maize monoculture was conducted in 2014–2017. Each year, MBM was applied presowing at 1.0, 2.0, and 3.0 t ha−1 to maize grown in experimental plots. The application of MBM decreased the bulk density and specific density and increased the pH of Haplic Luvisol Loamic (HLL) soil. The mineral nitrogen (N) content was highest when MBM was applied at 3.0 t ha−1 in HLL soil and 2.0 t ha−1 in Haplic Luvisol Arenic (HLA) soil. The minor differences in the mineral N content of soil between the treatment without fertilization and MBM treatments could be attributed to high N utilization by maize plants. The phosphorus (P) content of soil increased with a rise in the MBM dose. The P content of the arable layer was lower in HLA soil than in HLL soil, which resulted from higher P uptake by maize grain. The highest maize grain yield was achieved in the last year of the study, in response to the highest MBM dose and due to the residual effect of MBM.

IMPACT OF FISH PROCESSING BY-PRODUCT AMENDMENT ON SOIL PROPERTIES

A pot experiment was carried out at the Vytautas Magnus University Agriculture Academy in Lithuania to examine the possibilities of fish processing wastes to improve soil properties. The fish bones powder (FBP) was mixed with the soil, it was placed into the special vegetative pots of 5 l in volume up to the thickness of 25 cm. The soil type was Endocalcaric Endogleyic Luvisol (WRB 2014, update 2015) and according to granulometric composition was medium heavy loam. The experiment has designed in 4 variants and 6 replications. Soil samples were collected from the substrates in the vegetative pots 360 days (twelve months) after the application of fish processing by-products. The results obtained show that FBP application has significantly influenced the increase of organic carbon, available phosphorus, potassium and calcium contents in tested soil. The amount of FBP application didn’t show any noticeable impact on soil pH value, magnesium and sulphur content in medium heavy loam soil. Although the total nitrogen and mineral nitrogen contents have increased in soil a significant changes were found only after use of 6.5 t ha-1 FBP rate. The FBP application has significantly influenced the increase of microbiota abundance, microbial biomass C and microbial biomass N in tested soil. The microbial biomass C and N directly depended on the (FBP) rate.

ASSESSMENT OF THE ECOLOGICAL STATE OF WATERS BY THE SPECIES COMPOSITION OF ZOOPLANKTON AND PHYTOPLANKTON

Presented the results of studies of macrophytes, zooplankton and phytoplankton and the chemical composition of water polluted by sewage from a livestock enterprise and a conditionally clean pond. It was established that changes in the chemical composition of water after entering the reservoir of wastewater from a livestock enterprise due to an increase in the concentration of mineral and ammonium nitrogen, sodium ions, a decrease in the content of calcium and magnesium ions and hydrogen carbonate ions, at constant values of the pH indicator, total mineralization, potas-sium ions, chlorides and sulfates. Compared to a conditionally clean reservoir, it became polluted with sewage and was characterized by the intensive development of higher aquatic plants, a smaller number of zooplankton species, and its abundance and biomass underwent changes due to a decrease in the number of rotifers (Rotatoria) and an increase in the number of spiny (Sladocera) and copepods (Copepoda) crustaceans. Studies of the species composi-tion, number and biomass of phytoplankton in a pond polluted with wastewater from a livestock enterprise estab-lished the predominance of euglena algae over other species in the reservoir, a significant increase in the number of blue-green (Cyanophyta) and diatom (Bacillariophyta) algae in biomass, the presence of small-celled flagellates with department of cryptophytic and bacterial-fungal accumulations, in contrast to a conditionally clean water body. A conclusion was drawn on the expediency of using the species composition of phytoplankton and zooplankton, as well as individual indicators of the chemical composition of water as criteria for assessing the ecological state of ponds located in the area of activity of livestock enterprises when polluted by sewage.

Morphological variability, density and yield of Trifolium repens in different ecological and coenotic conditions

White clover (Trifolium repens L.) is a valuable melliferous, pasture and a promising species for use as a medicinal raw materials. T. repens herb contains ascorbic acid, carotene, alkaloids, glycosides and other substances. Fourteen coenopopulations of T. repens were studied on the territory of the Republic of Tatarstan. The assessment of habitats of T. repens was carried out by indicator methods using the ecological scales of G. Ellenberg. The density of coenopopulations, comparative morphometric analysis and reserves of dry aboveground biomass are analyzed in this article. It was found that the soils in the subtaiga subzone are weakly acidic, fresh in terms of moisture, with a nitrogen content above average; soils in the north of the broad-leaved subzone are dry and periodically fresh, with a slightly acidic reaction and an average content of mineral nitrogen; and the soils in the south of the broad-leaved subzone are dry and periodically fresh, predominantly neutral, with a nitrogen content above average. A comparative analysis of the scoring of soil characteristics with the content of the main nutrients in the soil has been carried out. T. repens coenopopulations in the north of the broad-leaved subzone have of low density, and high biomass shoots are formed. The yield of the studied T. repens plants is from 21-178 kg of dry weight/ha. The highest yields of dry aboveground biomass of plants was observed in the northern deciduous subzone. We recommend the highest-yielding coenopopulations of T. repens for harvesting plant material.

Quantification and comparison of ecosystem services of grasslands versus another fodder crop (maize) based on mineral nitrogen content in the 60–90 cm soil layer

Grasslands provide many ecosystem services. Apart from being a source of fodder for animals, grasslands regulate water and soil quality by reducing nitrogen emissions to the environment. The aim of the study was to determine the biophysical and monetary value of ecosystem services of grassland based on the “mineral nitrogen content in the soil layer 60–90 cm” indicator depending on the method of use and the type of soil, against the cultivation of maize for green fodder. The study area encompassed three provinces, different in terms of soil use, livestock population and intensity of grassland use. The investigation indicated that the value of ecosystem services provided by grasslands varied spatially and depended on the type of use and type of soil. In mineral soils, the lowest levels of this index were recorded from sites used for pasturing, while the highest levels were found under maize crops. In organic soils (without maize crops), the smallest losses of Nmin were observed in meadows while the highest losses were in pastures. Nmin losses in organic soils were higher than in mineral soils. The losses observed were highest in Opolskie Province, followed by Podlaskie Province, with the lowest losses in Lubelskie Province.

Agrochemical indicators of sod-podzolic sandy loam soil under the influence of fertilizer mixtures with sewage sludge

The paper presents the data of a three–year field experience on the study of the effect of the combined introduction of sewage sludge (WWS) and additional organic substrates (sawdust, peat, straw) in different ratios (1: 1, 1: 2, 1: 3) on the content of basic nutrients sod–podzolic sandy loam soil and the yield of field crops in the crop rotation link: vetch–oat mixture – winter rye – spring barley. For comparative characteristics, the experiment included a variant with ready–made compost based on WWS. The content of the main nutrients in the plow horizon of the soil was in direct proportion to the share of WWS in the composition of the mixture. The most effective influence on the studied parameters was provided by the introduction of WWS with peat in a 1:1 ratio. For 3 years, the content of mineral nitrogen exceeded the effect of compost by 12.5–32.6%, mobile phosphorus – by 7.0–32.9%, exchangeable potassium – by 15.6–18.5%. With the introduction of WWS and peat (1: 1), there was a significant increase in the yield of field crops relative to the option with ready–made compost: vetch–oat mixture – by 37.5%, winter rye – by 9.2%, spring barley – by 10.0%. Other types of fertilizer mixtures with the participation of WWS also had a positive effect on the agrochemical characteristics of the soil and yield in comparison with the control. In the year of direct action, the biomass increase was 30.9–74.5% (vetch–oat mixture), in the first year of aftereffect – 21.5–53.4% (winter rye), in the second year of aftereffect – 56.4–94.8. The studied dose of WWS of 30 t / ha did not cause excessive accumulation of toxic elements in the grain of winter rye and spring barley.

THE INFLUENCE OF EROSION PROCESSES ON THE CHANGE IN THE PARAMETERS OF THE MAIN AGROCHEMICAL INDICATORS OF SOIL FERTILITY ON SLOPING AGRICULTURAL LANDS OF THE REPUBLIC OF BELARUS

The article presents the results of studies of changes in the main indicators of fertility of sod-podzolic soils of slope lands under the influence of erosion processes. Determined the ranges of their reduction depending on the degree of erosion, constituting up to 20–30 % on weakly eroded soils, up to 30–40 % on moderately eroded soils, and up to 40 % and more percent on heavily eroded soils.
 The presence of trends in multidirectional changes in the content of humus, mobile phosphorus, mobile potassium and mineral nitrogen in the conditions of industrial crops on soils of various genesis and the degree of manifestation of erosion processes has been established.

Understanding Arbuscular Mycorrhizal Colonization in Walnut Plantations: The Contribution of Cover Crops and Soil Microbial Communities

Soil microorganisms play a central role in biological soil functioning. One of the beneficial microbiota that has a symbiotic association with most of the plants is arbuscular mycorrhizal fungi (AMF). Nevertheless, little is known about the impact of cover crops—widely used in conservation agriculture or organic farming—on native mycorrhizal fungi. This study was conducted in Southern France, in 20-year-old walnut orchards, where faba bean (Vicia faba Roth) was intercropped. To find whether the native AM fungal community associated with walnut trees was influenced by cover crops and soil microbial communities, analyses of soil physicochemical and microbiological indicators were carried out with roots and soil samples collected from four modalities (walnut in conventional farming with and without cover crops, and walnut in organic farming with and without cover crops). Our results showed that the presence of cover crops mainly influenced the soil microbial abundance and activities in conventional plots. In contrast, cover crops stimulated AM fungal colonization of walnut roots in organic plots, reaching 35% and 54% for arbuscule abundance and mycorrhizal intensity, respectively. In conventional plots, ergosterol and mineral nitrogen contents were mainly correlated with mycorrhizal colonization, while only acid phosphatase activity in soil was positively correlated with mycorrhizal colonization in organic plots. The use of the faba bean showed the great role played by cover crops in the enhancement of walnut trees’ mycorrhizal colonization. Identification of the functional traits of AM fungi sensitive to walnut trees is required to inform decisions in specific agricultural practices.

Subsoil carbon input by cover crops depends on management history

Cover crops represents an agricultural management option, which has the potential to increase soil carbon (C) stocks and contribute to atmospheric CO2 reduction. However, there is a scarcity of studies quantifying the C inputs from cover crops, particularly into subsoil layers. Furthermore, estimates of plant C inputs to soils often lack accounting of root fragments (here defined as roots in the size class of 0.25–4 mm) and net phyllo- and rhizodeposition. Based on a field experiment with multiple 13C-CO2 pulse labeling, we investigated the short-term C inputs from cover crop mixtures to 1-m depth in two long-term cropping systems with organic and conventional management. We used a novel 13C-based approach to quantify the amount of C in root fragments, as young fragile cover crop roots are challenging to sample in soils. The results showed that the total belowground C input to 1-m depth (570–1000 kg C ha−1) was similar across long-term management (organic and conventional, with or without a history of cover crops), but with a higher belowground C input for mixtures established without winter vetch (Vicia villosa Roth). The C input to the subsoil (> 25 cm) by cover crops accounted for 11–42% of the total plant belowground C input, which was significantly and negatively correlated to the soil fertility measured as the initial mineral nitrogen (N) content in the topsoil. The results suggest that root exploitation, and thus plant C inputs into the subsoil, was enhanced in relatively N poor cropping systems. Root fragments and net phyllo- and rhizodeposition accounted for 39–59% and 5–37%, respectively, of the total cover crop belowground C input, i.e., both representing significant pools of plant C input. We conclude that future studies on the effects of cover crops on soil C storage need to account for subsoil C pools including root fragments and rhizodeposition to achieve a comprehensive estimation of plant C inputs.

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.

Вплив диференціації азотного удобрення темно-каштанового солонцюватого ґрунту на його агрохімічні показники та врожайність сільськогосподарських культур

Goal. To establish features of the influence of differentiation (address rationing) of mineral nitrogen fertilizers application on agrochemical indicators of dark chestnut weakly alkaline soil (the content of mineral nitrogen and humus) and crop yield. Methods. Field — to study the effect of gypsum and nitrogen fertilizer on the properties of dark chestnut soil and crop yields, laboratory analysis — o determine the content of mineral nitrogen and humus, mathematical — to assess the reliability of research results. Results. The application of mineral nitrogen fertilizers has led to a tendency to increase the content of mineral nitrogen in dark chestnut weakly alkaline soil. Fertilization and cultivation of crops did not affect the variability of mineral nitrogen content, which in general in the experiment remained moderate, the coefficient of variation did not change. Although the average amount of nitrogen fertilizer applied to the plots in the variant of differentiated application is 92.1 kg/ha, was less than in the plots with the maximum level of fertilizer, the yield did not differ from that with the maximum level of application and was reliably higher than in the variant with the average level of application. Conclusions. It is established that under the influence of growing crops and applying nitrogen fertilizers, the supply of dark chestnut weakly alkaline soil with mineral nitrogen improves at medium and maximum levels of fertilizer. It is established that the lack of fertilizer or low doses of nitrogen fertilizers increase the variability of the soil in terms of mineral nitrogen content, and the high level of application (390 kg/ha) for 6 years under 3 crops equalizes this indicator. There was a decrease in the variability of dark chestnut weakly alkaline soil in terms of humus content in the arable layer. A stable significant increase in the yield of grain and fodder crops depending on the levels of nitrogen fertilizer application has been also established. Differentiation of nitrogen fertilizers allows saving nitrogen fertilizers in the amount equivalent to almost 15 kg/ha of active substance per year in grain-feed 6-field crop rotation in the absence of a significant reduction in yield on dark chestnut weakly alkaline non-irrigated soils.

Long term field trials demonstrate sustainable nutrient supply and uptake in rehabilitated bauxite residue

Establishing a sustainable vegetation cover is one of the most important steps in progressive rehabilitation and final closure of ore-processing residues and tailings facilities. Sustainable rehabilitation partly depends on establishing and maintaining a supply of plant-available nutrients, but few long term field studies demonstrating the success or failure of rehabilitation of degraded land such as mineral processing tailings have been reported. Bauxite-processing residues are a highly sodic, highly alkaline, nutrient-poor by-product generated from alumina extraction, and pose many challenges for successful rehabilitation. This study investigated long term performance of rehabilitation established on bauxite-processing residue storage areas (RSAs) by comparing the nutrient content of the vegetation cover with nutrient concentrations in the underlying residue sand. Five plant species having diverse physiology were selected from rehabilitation varying in age from 1 to 10 years old; these being: Hardenbergia comptoniana – a vigorous growing legume ground cover/creeper), Acacia cochlearis and A. rostellifera - legume shrubs tolerant of sandy, alkaline conditions, Grevillea crithmifolia - a drought-tolerant proteaceous shrub tolerant of alkaline soil, and Spyridium globulosum - a robust, fast-growing shrub, commonly found on alkaline coastal soils. Gypsum incorporation reduced the pH and soluble aluminium levels in residue sand, but also acted as a long-term source of nutrients for the vegetation cover. Legume species contained more nitrogen than non-legumes (2.5% N and 1.5% N, respectively), and decomposition of surface litter increased organic carbon and total and mineral nitrogen contents of the residue sand over time. Nutrient cycling maintained a supply of macro- and micro- nutrients for the vegetation cover, and 10-year old rehabilitation exhibited characteristics similar to an analogue site. This study highlighted the importance of organic matter accumulation, developing a functional microbial community, and a diverse plant species mix on transforming the residue sand characteristics and encouraging nutrient cycling as key mechanisms for establishing a sustainable vegetation cover and functional ecosystem on residue sand embankments.

Physico-chemical Characteristics and Nitrogen Use Efficiency of Nine Human Urine-Based Fertilizers in Greenhouse Conditions

Most of the nutrients in wastewater come from human urine and their recycling for agricultural purposes is very limited. After source separation, urine can be treated to produce various urine-based fertilizers. This study aims to characterize the nitrogen use efficiency of different urine-based fertilizers. Nine urine-based fertilizers were compared together with ammonium nitrate and cattle slurry in a greenhouse pot trial with English rye-grass, (Lolium perenne L.). The detailed physico-chemical characteristics of the fertilizers were analyzed. The biomass production and nitrogen uptake of the plants were measured. The nitrogen use efficiency and the mineral fertilizer equivalent were determined for each fertilizer. The urine-based fertilizers were classified in four types based on their nitrogen forms (ammonia, nitrate, urea, or organic). The mineral fertilizer equivalent of most urine-based fertilizers were above 85% and even higher than 100% for nitrified concentrated and acidified stored urine. The lowest mineral fertilizer equivalent were found for fermented fresh urine and the mixture of fresh urine and woodchips but remained between 65 and 75%. In all cases, the nitrogen use efficiencies of urine-based fertilizers were higher than that of cattle slurry. The differences among the urine-based fertilizers and from the cattle slurry were attributed to the mineral nitrogen content which was much higher in urine-based fertilizers. Indeed, they contain mainly mineral nitrogen. Their content of trace element contaminants is low. Their efficiency as nitrogen fertilizers is high and close to that of mineral fertilizer. However, new valorization pathways from cities to agriculture need to be developed.

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.