Soil Mineral Nitrogen Content Research Articles

Combined use of NBPT and micronutrients in granulated or coated urea: A new approach to reduce ammonia volatilization losses from soil

AbstractN‐(n‐Butyl) thiophosphoric triamide (NBPT) is the most widely adopted urease inhibitor, used to reduce ammonia (NH3) volatilization from urea. Micronutrients such as boron (B), zinc (Zn), nickel (Ni) and molybdenum (Mo) are also reported to inhibit urease, serving simultaneously as plant nutrients. However, there is little information on the potential synergistic or antagonistic effects of NBPT and micronutrients on urea protection. The aim of this study was to evaluate NH3 volatilization losses, soil pH and soil mineral nitrogen content (‐N and ‐N) after application of urea coated or granulated with the micronutrients B, Zn, Ni or Mo, individually. Thereafter, the fertilizers were applied combined and not associated with NBPT. Ammonia volatilization was measured in a closed static chamber under controlled conditions. Urea granulated with B and Zn reduced NH3‐N volatilization circa 30% compared with untreated urea, while Mo and Ni had no effect. NBPT stabilizer had the greatest effect on NH3‐N volatilization (44%–59% reduction), but was less effective (only 20%–34% reduction) when urea was coated with B, Zn or Mo. On the other hand, when B and Zn were incorporated via granulation, the efficiency of NBPT was not reduced, likely because of the physical separation. These findings demonstrate that granulating urea with B or Zn combined with an NBPT‐coating can be a valuable strategy to reduce NH3 volatilization losses while also supplying micronutrients and hence potentially increase yields in agricultural production systems.

Soil Mineral Nitrogen and Mobile Organic Carbon as Affected by Winter Wheat Strip Tillage and Forage Legume Intercropping

Diversifying crop rotations by incorporating legumes is recommended to enhance the resilience of agricultural systems against environmental stresses and optimize nitrogen utilization. Nonetheless, ploughing forage legumes or grass-legumes poses a significant risk of nitrate leaching. The study aimed to assess the impact of strip tillage intercropping management on soil mineral nitrogen, water-extractable organic carbon, mobile humic substances content, and winter wheat (Triticum aestivum L.) grain yield compared to forage legume and winter wheat monocropping with conventional tillage. In the intercropping systems, the following bicrops were used: black medick (Medicago lupulina L.) with winter wheat, white clover (Trifolium repens L.) with winter wheat, and Egyptian clover (Trifolium alexandrinum L.) with winter wheat. Research was conducted in two experiments. The results indicated that after implementing strip tillage and winter wheat intercropping, the soil mineral nitrogen content was similar to or lower than that observed in conventional tillage and winter wheat sowing after forage legumes. Winter wheat grain yield in intercrops decreased compared to the legumes monocultures that were ploughed before winter wheat sowing. The highest amount of water- extractable organic carbon was in intercropping growing white clover and winter wheat bicrops or in all fields (except Egyptian clover and winter wheat bicrops) after applying strip tillage. During the research period, the quantities of mobile humic substances and mobile humic acids exhibited similar changes. Their content increased substantially in fields with white clover and Egyptian clover, regardless of whether the legumes were ploughed or grown with winter wheat.

N supply and yield of sugar beet after cover cropping: effects of cover crop species and management

Despite long-time practice, the effect of cover crop (CC) cultivation on N supply and yield of subsequent sugar beet (SB) is not clear for the temperate climate of Central Europe. To elucidate, four field trials with oil radish, spring vetch, saia oat, and winter rye CCs were conducted on typical loessial soil in Germany. Mineral fertilizer N dose was varied as second factor: zero (N0) and optimum dose (Nopt). Biomass characteristics before winter, soil mineral nitrogen content in spring (SMN), and sugar yield and total plant N content of SB were measured. The CC N effect (Neff), calculated as the difference in SB N uptake after CC minus bare fallow, was computed for the periods sowing-summer (July/August) and summer-harvest. On average, sugar yield was decreased after rye and increased after vetch CC compared to bare fallow which was more pronounced under N0 than Nopt. In the period sowing-summer, characterized by a high SB N demand, Neff was close to 0 kg N ha–1 after rye and up to +30 kg N ha–1 after vetch. In contrast, Neff in summer-harvest was negative, amounting up to –80 kg N ha–1 after radish and rye. Regression analysis revealed a significant relationship between Neff in the period sowing-summer and the sugar yield difference between the cover crop treatments and bare fallow (R2 = 0.29). A multiple regression analysis (R2 = 0.68) indicated that high CC biomass combined with a large negative spring SMN difference between CC treatment and fallow caused a large yield penalty, which can be compensated for by elevated N fertilization. Moreover, CC management ensuring either a limited CC biomass or low SMN difference of CCs compared to fallow by e.g., later sowing, less vital CC species or early CC termination, will likely secure higher SB yield after CCs than fallow.

Impact of mechanical weed control on soil N dynamics, soil moisture, and crop yield in an organic cropping sequence

Mechanical weed control is a major element of weed suppression in organic farming systems. In addition to the direct effect on weed growth, mechanical weeding, such as harrowing or hoeing, is known to induce side effects on several soil- and crop-related properties. In this study, we investigated the impact of mechanical weeding on soil mineral nitrogen (SMN), soil moisture, and crop yield in an organic crop rotation of grass-clover (Lolium multiflorumLam., Trifolium pratense L.), silage maize (Zea mays L.) and winter barley (Hordeum vulgare L.). The experiment was conducted in two consecutive years (2021, 2022), where each crop was grown in each year on a Plaggic Anthrosol with sandy loam in North-West Germany. Two weed control treatments (mechanical: harrowing, hoeing; chemical: herbicide application) were implemented in a randomized block design with four replications. Greater net nitrogen (N) mineralization in maize compared to winter barley were attributed to the incorporation of grass-clover residues before sowing of maize and greater mineralization potential during the maize growing season. Higher weed growth in maize after mechanical weeding resulted in a reduction of up to 47% in SMN content in the topsoil. In barley, no differences in weed suppression were observed between the treatments and only small effects on SMN were determined after mechanical weeding. The soil water content in the mechanically weeded plots was significantly higher at several events in both years and for both crops, which was attributed to increased water infiltration by disrupting the soil crust. Neither crop yield nor N uptake in harvest products was affected by the different treatments.

Nitrous oxide fluxes during a winter cover crop season in a Mississippi corn cropping system

Agroecosystems are the largest source of anthropogenic N2O fluxes. While cover crops (CC) offer benefits for soil health, their impacts on greenhouse gas fluxes are inconsistent. In the southeastern US, where intensive agriculture and low CC adoption are prevalent, few studies have investigated CC impact on soil N2O fluxes. Our study explored the effects of CC species and management practices on soil N2O fluxes during the winter CC growing season in Mississippi, which was conducted in a non-tilled corn cropping system with seven CC treatments. We measured in situ soil N2O fluxes, along with soil moisture and temperature, throughout the CC growing season from 2022 to 2023. Surface soil samples were also collected to analyze soil mineral nitrogen (N) content and enzyme activity. Over the study period (a total of 188 days), cumulative N2O fluxes were 0.50–1.03 ​kg N2O–N ha−1, with the lowest values from the annually-rotated Elbon rye treatment and the highest from the annually-rotated Austrian winter pea. Our results show that both CC treatments and sampling time significantly affected soil N2O fluxes. There was a strong positive correlation (r ​= ​0.34, p ​< ​0.05) between N2O fluxes and NO3–N content, which was lowest under continuous rye and rotated-rye treatments (0.31 and 0.34 ​mg ​kg−1 ). The results suggest that Elbon rye effectively reduced soil N2O fluxes during this period by lowering the soil NO3–N content, the primary substrate for denitrification. This study is one of the few studies to examine the impacts of cover crops on soil N2O fluxes in cropping systems in the southeastern US, offering insights into the cover crop effects on soil N2O fluxes during their growing season.

Characteristics of N Transformation of Humic Acid Urea in Different Circle Layers of the Fertisphere: A Simulated Experiment

Due to its broad yield-increasing effect and low cost, humic acid urea (HAU) has become one of the leading modified fertilizers worldwide. The fertisphere is the primary space where urea (U) granules participate in the soil nitrogen cycle, forming a nutrient concentration gradient centered on the point of fertilization. The closer the circle layers to the urea granule in the fertisphere, the higher the nitrogen concentration. However, HAU in this microregion remains poorly understood. The differences in the transformation process from the inside to outside circle layers of the U and HAU fertispheres were simulated and studied using soil incubation experiments under 20, 10, 2, 1, and 0.2 g kg−1 nitrogen inputs. The 20 and 10 g kg−1 inputs represent the layers closest to the urea granule. Within the first seven days, HAU treatment showed higher concentrations of soil ammonia-N content than U treatment within the two layers closest to the fertilizer core, while exhibiting lower concentrations under the farthest two layers. Under 2 g kg−1 nitrogen input, the nitrate nitrogen under the HAU treatment was significantly higher than that in the U treatment, indicating a higher nitrification rate. During the 42-day incubation period, soil mineral nitrogen content under the HAU treatment was higher than that for the U treatment in the two closest circles. On the 42nd day, the residual urea-N under the HAU treatment was significantly higher than that for the U treatment when the nitrogen input was higher than 1 g kg−1. The effect of higher fertilizer preservation and supply capacity of HAU in Fluvo-aquic soil was achieved by changing the urease activity and nitrification rate in fertisphere ranges closer to the fertilizer core. An improved understanding of the high-efficiency mechanism of HAU in the fertisphere process will contribute to the development of new-generation high-efficiency urea products.

Maize residue input rather than cover cropping influenced N2O emissions and soil–crop N dynamics during the intercrop and cash crop periods

The well-known benefits of cover cropping for mitigating climate change and improving soil quality could be threatened by increased greenhouse gas emissions. Therefore, such practices could have negative consequences in the context of global climate change. The present year-long field experiment, carried out under irrigated semiarid conditions, evaluated the effect of returning maize crop residues at two topsoil input levels in combination with bare fallow, a cereal (barley, Hordeum vulgare L.) and a legume (vetch, Vicia sativa L.) as cover crops as part of an annual cover crop–cash crop (maize, Zea mays L.) rotation. In addition, control plots, without the addition of nitrogen fertilizer (either in the previous cropping season or during the experiment), were established following the same experimental design in order to assess the carry-over impact of residual nitrogen from prior crops. Nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) fluxes were measured together with soil mineral nitrogen and crop yields and nitrogen use efficiency. The significant effect of maize residue input on N2O emissions during the cover crop phase (this was 43% greater for the lower maize residue input than for the higher) was offset after subsequent maize fertilization (there was a 170% increase following the higher maize residue input compared to the lower). Although no differences in soil mineral nitrogen content were reported between treatments before maize fertilization, N2O emissions were 72% higher on the fertilized plots than on the control plots. Before maize fertilization, N2O emissions were increased by the incorporation of cover crop residues and soil rewetting after irrigation, with the highest N2O fluxes being reported for the cereal crop. Cumulative CO2 fluxes were higher in the plots with cover crops (cereal and legume) than in bare fallow plots, while CH4 sink was not affected by cover cropping or maize residue input. The grain yield penalty for maize production (a 7% decrease) with the legume cover crop on the nitrogen fertilized plots (the opposite of what was observed in the control area) highlights the need for an accurate estimation of the nitrogen supply from the mineralization of legume residues. Overall, cover crop and maize residue input did not have any significant effect on annual cumulative N2O emissions, so the positive effects of these practices should be considered to recommend them under semiarid conditions for climate change mitigation and adaptation.

The Influence of Organic and Inorganic Fertilizer Applications on Nitrogen Transformation and Yield in Greenhouse Tomato Cultivation with Surface and Drip Irrigation Techniques

Facility agriculture in China is facing the challenge of the excessive use of chemical fertilizers (nitrogen fertilizers), which hinder the development of sustainable and environmentally friendly agriculture. Optimizing nitrogen fertilizer allocation is essential to balance agricultural production and environmental concerns. The aim of this study was to determine the optimal organic fertilizer strategy for tomato cultivation under different irrigation methods. An experiment was conducted in a greenhouse, and two irrigation methods, surface irrigation (SI) and drip irrigation (SDI), were used during tomato growth. The fertilization treatments included urea alone (CK); 30%, 40%, and 50% chicken manure mixed with urea (FC1, FC2, FC3); and 50% cow manure and sheep manure mixed with urea (FB3, FS3). The results showed that the irrigation techniques and fertilization had significant effects on ammonia volatilization accumulation, soil mineral nitrogen content, and tomato yield and quality. Compared with the surface irrigation technique with the same amount of fertilizer application, the drip irrigation technique reduced the ammonia volatilization accumulation by a maximum of 76.40%. The SDIFC3 and SDIFB3 ammonia volatilization accumulation was as low as 5.24 (kg·hm−2) and 7.61 (kg·hm−2); the soil nitrate nitrogen content was reduced, and the tomato yield increased significantly by 17.11%. The SDIFC3 treatment achieved a maximum yield of 13,414 (kg·hm−2), increased the tomato vitamin C and soluble sugar contents by 19.13% and 8.97%, and lowered the titratable acid content by as much as 30.51%. Under drip irrigation fertilization conditions, the SDIFC3 treatment showed lower ammonia volatilization accumulation and the highest tomato yield and quality compared to CK and the same proportion of organic fertilizer substitutes with cow and sheep manure. The increase in the proportion of organic fertilizers replacing chemical fertilizers resulted in a gradual decrease in ammonia volatilization accumulation and a gradual increase in the tomato yield and various qualities. The soil mineral N content, on the other hand, was significantly affected by irrigation, fertilizer application, and water–fertilizer interaction effects, with a tendency for the content to increase and then decrease after each fertilizer application. The mineral N content was lower with drip irrigation compared to surface irrigation, especially in the 10–20 cm soil layer than in the 0–10 cm layer. Increasing drip irrigation and organic fertilizer substitution significantly increased the vitamin C and soluble sugar contents in the tomatoes, while decreasing the titratable acid content.

Poly-γ-glutamic acid affects NH3 volatilization, soil nitrogen content, and soybean seedling growth

Abstract Poly-γ-glutamic acid (γ-PGA) is a soil amendment that has been shown to enhance soil water retention capacity. However, the effects of γ-PGA on soil NH3 volatilization, soil nitrogen pool, and crop growth have been rarely studied. This study aimed to investigate the effect of γ-PGA on NH3 volatilization, soil mineral nitrogen content, and soybean seed productivity. We conducted an incubation experiment and a pot experiment using two different textured soils (sandy soil and sandy loam soil) with four γ-PGA application rates (0, 0.1, 0.3, and 0.5%, w/w). The results showed that the application of γ-PGA decreased the peak value of NH3 volatilization and cumulative NH3 emission through the incubation experiment. Cumulative NH3 volatilization decreased with increasing γ-PGA application amount. The addition of γ-PGA to sandy soil and sandy loam soil increased soil N content by 17–63% and 7–33%, respectively. Based on pot experimental results and principal component analysis, we recommend the optimal rates of γ-PGA application were 0.3% (w/w) in sandy soil and 0.1% (w/w) in sandy loam soil. This study provides a theoretical basis for the addition of γ-PGA as a promising strategy to reduce NH3 volatilization and increase soil nitrogen content.

Cover Crop Yield, Nutrient Storage and Release under Different Cropping Technologies in the Sustainable Agrosystems.

Due to short post-harvest seasons, it is not always possible to grow worthy cover crops (CCs). This research aims to clarify the impact of undersown red clover (Trifolium pratense L., RC) and post-sown white mustard (Sinapis alba L., WM) management on their biomass, accumulated nitrogen (N), phosphorus (P), and potassium (K) content and the nutrient release to subsequent main crops. During the study period, RC mass yields varied from 220 to 6590 kg ha-1 DM and those of WM from 210 to 5119 kg ha-1 DM. WM shoot biomass increased with the increase in rainfall in August and the average daily temperature of the post-harvest period. CC productivity and efficiency were higher when growing short-season spring barley than winter wheat. In the warm and rainy post-harvest period, undersown WM after winter wheat increased the biomass by 34.1% compared to post-harvest sowing. The application of straw (+N) increased the accumulation of nutrients in WM biomass. The intensive fertilization of the main crop had a negative effect on RC yield and NPK accumulation. RC shoot biomass was characterized by a higher N content and WM by a higher P concentration. Well-developed CCs could reduce soil mineral nitrogen content by 28.5-58.8% compared to a plot without CCs. Nutrient transfer to spring barley was dependent on the N content of CC biomass and the carbon and nitrogen ratio (C:N < 20). We conclude that CC growth and efficiency were enhanced by the investigated measures, and in interaction with meteorological conditions.

Natural Grass Cultivation Management Improves Apple Fruit Quality by Regulating Soil Mineral Nitrogen Content and Carbon-Nitrogen Metabolism.

Orchard grass cultivation management is an effective measure to safeguard the sustainable development of the fruit industry in China. However, details of the influence of natural sod culture management on carbon (C)-nitrogen (N) nutrition of trees and fruit quality in Hanfu apple orchards are lacking. Therefore, a field experiment was conducted, which consisted of two treatments: clean tillage (CT) and natural grass cultivation (NG). Results revealed that NG treatment contributed to the increases in soil organic matter (SOM), total N, and soil NH4+-N at depths of 0-20 cm and 20-40 cm, while the soil NO3--N concentration under NG treatment was significantly decreased at the same depth, within the range of 0-200 cm of the soil profile, compared with CT. NG treatment also significantly promoted leaf photosynthesis and enhanced leaf N and fruit sugar metabolism. The results of isotope labeling showed that NG treatment obviously elevated the 13C accumulation and distribution rate in fruits, as well as the 15N accumulation in the whole tree, whereas the 15N accumulation in fruits decreased. Furthermore, NG treatment significantly increased the fruit anthocyanin content. These results provide theoretical references for the feasibility of natural sod culture management to improve fruit quality in Hanfu apple orchards.

Nitrate leaching potential from arable land in Germany: Identifying most relevant factors

Diffuse nitrogen losses from agriculture in Germany continue to cause regionally increased nitrate concentrations in groundwater. Groundwater quality monitoring cannot be a timely indicator of the effects of mitigation measures being applied in agriculture, due to frequently long transport routes and high residence times of the leachate. Instead, nitrate leaching potential is often determined at field and farm scale by monitoring soil mineral nitrogen contents at 0–90 cm depth in autumn (SMNa), i.e. before the start of the annual leachate period. In this study, we developed an understanding of the controls on the soil mineral nitrogen content at the start of winter. In an on-farm approach, extensive data was collected from 48 farms in five nitrate-sensitive regions in Germany from 2017 to 2020. From this data set, 25 management and site factors were evaluated with regard to their significance for SMNa by means of a random forest model. With the random forest regression, we identified the role of the factors on SMNa with an acceptable model accuracy with R2 = 0.56. The results show that the cultivated crop is the most important factor influencing SMNa. Potatoes, oilseed rape and maize produced the highest SMNas, whereas SMNas were lowest after spring barley, sugar beet and winter barley. Among site factors, soil type and texture as well as precipitation in October were most decisive. The effects of N fertilisation parameters such as rate and timing were masked by these site factors. The results show that the reduction of nitrogen-intensive crops in crop sequences can be a promising measure for the reduction of nitrate loads. On the other hand, our analysis makes clear that soil-related factors controlling nitrogen release and risk of leaching, as well as weather, can significantly mask the effect of cultivation.

Impacts of measured soil hydraulic conductivity on the space–time simulations of water and nitrogen cycling

In agriculture, variations in soil nutrients and water are driven by soil properties, topography and agronomic practice that typically interact and change over space and time. Agroecosystem models need to capture these sources in variation, where this study’s first objective was to assess the potential of using measured saturated soil hydraulic conductivity (ksat) to improve the simulation accuracy of water and soil mineral nitrogen content from the SPACSYS model for a lowland UK grazed field (6.34 ha). As a second objective, SPACSYS was run at the field level and at the within-field level to provide a further comparison of simulation accuracy. For model calibration, ksat was measured at 27 points at 0–10, 10–20 and 20–30 cm soil depths on a 50 × 50 m grid. For model validation, moisture and mineral nitrogen content in the same three soil layers, at 10 adjacent points on a 25 × 25 m grid, were measured monthly from May 2018 to April 2019, together with in situ field level water flux measurement. Measured ksat coupled with the within-field setting allowed a novel spatial investigation of SPACSYS performance. Measured ksat (as opposed to unmeasured, default values) was found to improve water flux simulation, but only slightly so, which was considered in part due to a high positive skew in the measured ksat coupled with no clear spatial structure. Field level and within-field specifications simulated soil moisture with equal accuracy, while simulation accuracy of soil ammonium and nitrate improved via the within-field setting; for water flux simulation, the field level setting should be preferred. Results provide further evidence for when a field level setting should be preferred to a within-field setting and vice-versa.

Soil mineral nitrogen content and grain yield with enhanced efficiency fertilizers in maize

AbstractUrea is the most common N fertilizer worldwide, but N from urea breakdown can be easily lost through ammonia (NH3) volatilization, ammonium (NH4+) nitrification, nitrate (NO3−) denitrification or NO3−–leaching processes. Enhanced efficiency fertilizers (EEFs) are formulated to minimize N losses and maximize plant N uptake and crop yields. The capacity of urea EEFs (urea with urease inhibitor, nitrification inhibitor, both urease and nitrification inhibitors, and polymer‐coated) to maintain N in the soil profile throughout the growing season was determined by the analysis of [NH4+–N] and [NO3−–N] in three top‐soil depth increments at three dates in three seasons of no‐till maize (Zea mays L.). Surface‐applied EEFs, untreated urea, and injected urea ammonium nitrate (UAN) were compared at an application rate of 168 kg N ha−1. Within and across years, soil [NO3−–N] and [NH4+–N] typically decreased with depth and time since urea application. Among the EEFs, only a polymer‐coated urea produced greater [NO3−–N] and [NH4+–N] at several sampling dates and depths, and greater grain yields than untreated urea across the 3 yr. Nonetheless, the polymer‐coated urea resulted in significantly greater fertilizer use efficiency (FUE) than untreated urea in only 1 of 3 yr. Several EEFs increased grain yields compared to untreated urea each year, but FUE generally was similar to that with untreated urea. Environmental conditions influenced the effectiveness of EEFs in improving soil mineral N availability and increasing grain yield.

Effect of Compost Derived from Urban Waste on Chard (Beta vulgaris L., var cycla) Yield and Soil GHG Fluxes in a Mediterranean Agricultural System

The use of recycled materials as soil amendments and fertilizers is an important priority in the agronomic sector to valorize waste from a circular economic perspective and reduce waste disposal, reduce dependence on external inputs, and provide better climate change mitigation options. In this study, we evaluated the agroecological performance of compost derived from recycled organic matrices of urban waste (mixed composted amendment, MCA) of the metropolitan area of Rome. MCA is available in big quantities and might represent an interesting option to substitute conventional mineral nitrogen fertilizer (CF). The effect of MCA, CF, and a combination of both (MIX 1:1) was tested on crop yield and greenhouse gas emissions in a field trial on a common Mediterranean crop (Swiss chart, one season, two crop cycles). The MCA effect on crop yield was positive and comparable to CF and MIX treatments, while MCA treatment showed the lower soil mineral nitrogen (N) content. GHG emissions in the MCA treatment were comparable to those observed in CF and MIX, being overall quite low. The soil acted as a weak net CH4 sink in all treatments (−12.6 ± 6.1 μg CH4 m−2 h−1); no differences in CO2 emissions between MCA and CF or MIX treatments were observed (range 0.1−0.2 g m−2 h−1). The N2O emission intensity of MCA was slightly lower than MIX and CF treatments (0.09, 0.011, and 0.011 g N2O kg−1 crop dry weight, respectively). Overall, MCA seemed a valid alternative to CF for the tested agro-environmental indicators in the spring/summer Mediterranean conditions.

Soil Organic Carbon and Mineral Nitrogen Contents in Soils as Affected by Their pH, Texture and Fertilization

Soil organic carbon (SOC) and mineral nitrogen (Nmin), especially nitrates (NO3−) in agroecosystems have attracted much attention over the past few decades due to their crucial roles in soil fertility, crop productivity, environmental quality, and/or climate change mitigation and adaptation. The aim of the study was to evaluate the contents of organic carbon, ammonium, and nitrate in soils under differentiated pH, texture, and fertilization rates. A large-scale environmental study was conducted in Polish arable lands. The spatial distribution of the sampling points reflected agricultural production conditions, variability of soil properties, and representativeness of textures that are characteristic of Poland. Our results indicated that SOC content was significantly affected by the soil pH and texture as well as mineral and organic fertilization. The same factors, except organic amendments, significantly supported mineral nitrogen concentration in the present study. The most important factors controlling SOC in the study were ranked as follows: soil pH &gt; pre-crop N fertilization &gt; crop N fertilization &gt; N applied with manure &gt; soil texture. In the case of N-NH4 and N-NO3, mineral fertilization was the most critical variable. The carbon and nitrogen governance in agroecosystems should consider the ranks of factors controlling their contents.

Trees in temperate alley-cropping systems develop deep fine roots 5 years after plantation: What are the consequences on soil resources?

Trees in alley-cropping systems (AC) were reported to develop deeper fine roots compared to forest trees and that they can modify soil water (SWC), mineral nitrogen (SMN) and organic matter (SOM) content. However, intercropping young trees has not been studied extensively. This study aimed to count tree fine roots abundance (TFRA) along a chronosequence of AC stands, to determine factors explaining its variability and to highlight its effects on soil resources. Seventeen alley-cropping plots ranging from 3 to 12 years old were chosen on farms in northern France. TFRA was measured by the core break method using soil samples collected at 0, 1, 3 and 10 m from a referent tree (a maple, a hybrid walnut or a hornbeam) down to 2 m depth. Before four years old, tree fine roots colonized the topsoil (0–30 cm) in rows and then mainly grew vertically from 4 to 6 years old, before laterally exploring deep soil layer (1–2 m) beyond this age. Stepwise analyses showed that stand age, tillage frequency and crop rotation duration explained 60 % of the variability of the sum of TFRA calculated for all soil layers at all distances from the tree row. The SWC was negatively correlated to TFRA suggesting that as trees get older, they dried the deep soil layer below the crop rooting zone and increased the soil depth able to store autumn and winter rainfall. No significant effect of either stand age or distance from tree rows was observed for SMN. It varied significantly with soil depth (R² = 0.3***) and was strongly correlated with soil nitrate content (R² = 0.97***). The soil ammonium content was significantly correlated with TFRA, suggesting that tree fine roots favor ammonium production or accumulation in soil, which may potentially allow for a reduction in the mineral nitrogen (N) mobility for leaching. Finally, we found a significantly high SOM correlated with TFRA only in topsoil on the tree rows at our oldest stands. No change of SOM was observed in the deep soil layer regardless of stand age. From this study, we concluded that fine root plasticity of intercropped trees occurred at early stage and may contribute with age to a better use of soil water, to managing the soil mineral N dynamic and to sequestrating carbon, at least in tree rows.

Effect of Nitrogen Fertilization of Apple Orchard on Soil Mineral Nitrogen Content, Yielding of the Apple Trees and Nutritional Status of Leaves and Fruits

Contemporary trends in horticulture are aimed at limiting the use of mineral fertilizers to the necessary minimum, which is to guarantee adequate profitability of production while maintaining high-quality fruit and at the same time preventing environmental pollution. Thus, in the presented study, we investigate the effect of diversified nitrogen fertilization on soil mineral nitrogen content during vegetation season, yielding of apple trees and the nutritional status of apple leaves and fruits. We compared several ammonium nitrate treatments as well as growth without fertilization as a control. The results of our study show that under the conditions of humus-rich soils and with appropriate agrotechnics, N mineralization from the organic matter available in the soil may completely cover demand of apple trees for this component. Achieved outcomes clearly revealed that nitrogen fertilization in the amount of 100 kg N · ha−1 on the entire soil surface carries a real risk of groundwater contamination, and the same nitrogen dose applied within the grassland does not bring any production effects, therefore it should be considered as unjustified. Obtained results revealed that in a rationally managed, fully fruiting apple orchard, the annual dose of N should not exceed 50 kg N∙ha−1. This dosage of N should fully secure the nutritional needs of apple trees, guaranteeing their high yield and complete safety for the environment. What is important is, nitrogen fertilization strongly affects macroelemental composition of apple leaves and fruits.

Biocrusts from Iceland and Svalbard: Does microbial community composition differ substantially?

A wide range of microorganisms inhabit biocrusts of arctic and sub-arctic regions. These taxa live and thrive under extreme conditions and, moreover, play important roles in biogeochemical cycling. Nevertheless, their diversity and abundance remain ambiguous. Here, we studied microbial community composition in biocrusts from Svalbard and Iceland using amplicon sequencing and epifluorescence microscopy. Sequencing of 16S rRNA gene revealed the dominance of Chloroflexi in the biocrusts from Iceland and Longyearbyen, and Acidobacteria in the biocrusts from Ny-Ålesund and South Svalbard. Within the 18S rRNA gene sequencing dataset, Chloroplastida prevailed in all the samples with dominance of Trebouxiophyceae in the biocrusts from Ny-Ålesund and Embryophyta in the biocrusts from the other localities. Furthermore, cyanobacterial number of cells and biovolume exceeded the microalgal in the biocrusts. Community compositions in the studied sites were correlated to the measured chemical parameters such as conductivity, pH, soil organic matter and mineral nitrogen contents. In addition, co-occurrence analysis showed the dominance of positive potential interactions and, bacterial and eukaryotic taxa co-occurred more frequently together.

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.