Mineral Nitrogen Content Research Articles

Geobotanic and phytoindication characteristics of Amorpha fruticosa L. population in the serious coenosis conditions of the floodplain in the lower level Kaniv hydro power plant

On the basis of geobotanical descriptions of phytocenoses with Amorpha fruticosa L., representing primary succession separate stages of different floodplain altitude levels made on the islands territory below the Kaniv hydro power plant, the general characteristic of the vegetation dynamics with this species participation is presented. Using the method of phytoindication, the main characteristics of ecological factors indicators and their change directions during xero-, meso- and hydroseries are determined. The ecological factors indicators were obtained by the method of syphitoindication: soil moisture (Hd), variability of soil moisture (fH), soil aeration (Ae), general soil salt regime (trophic) (SL), soil acidity (Rc), mineral nitrogen content (Nt ) and carbonate content (Ca) in the soil, thermal regime (Tm), continental (Kn), frost (cryo) (Cr), climate humidity (humidity) (Om), luminosity (Lc). To compare ecological amplitude and elucidate the relationship between coenoses, the cluster analysis method and the shifted ratio analysis (DCA) method were used. A. fruticosa, characterized by a wide phytocenotic range, is included in phytocenoses at all stages of succession of Middle Dnieper floodplain three levels, representing xero-, meso- and hydroseries. During the succession, the qualitative and quantitative changes of such phytocenoses geobotanical characteristics as the species number and their composition, the A. fruticosa role as a coenotic agent, the age structure of its co-populations are natural. Also, based on the phytoindication method, the differences of phytocenoses representing xero-, meso- and hydroseries are monitored, a relatively wide range of ecotopes differing in humidity and soil aeration factors, favorable for the growth of A. fruticosa regular trend of most ecological factors during xeroseries and hydroseries towards the indices of mesoseries phytocenoses

Agroecological practices for organic lettuce: effects on yield, nitrogen status and nitrogen utilisation efficiency

ABSTRACTClimate change tends to intensify extreme weather events worldwide, negatively affecting agriculture and threatening global food security. More resilient agroecosystems are required to assure yield stability. In this research, which was carried out in a Mediterranean environment in 2013–2015, the response of organic lettuce to cover crop management and organic fertilisation, in terms of yield, nitrogen status and efficiency, was investigated. A vetch cover crop was introduced before the lettuce and was terminated by the no-till roller crimper strategy (RC), which was compared with incorporation of the vetch into the soil as green manure (GM) and with a no-vetch control (No_V). Two organic fertilisers derived from waste recycling, anaerobic digestate (AD) and municipal solid waste compost (MSW), were compared with a commercial organic fertiliser (ORG) and with a control with no fertiliser (No_F). The RC treatment resulted in high lettuce yields in both years, whereas GM showed intermediate yield values (significant differences in 2014). Crop N status reflected yield, with improved values in RC plots. At harvest, particularly in 2014, the use of vetch and fertilisers increased soil mineral nitrogen concentrations compared with those in No_V and No_F treatments, though the differences were not statistically significant. Lettuce N use efficiency (NUE) had an inverse trend to that of the yield; the lower the yield the higher the NUE. The RC in combination with the use of organic fertilisers assured a satisfactory response to the variability in weather, in terms of both yield stability and preservation of soil fertility.

Динаміка родючості чорнозему типового глибокого залежно від системи удобрення і ланки сівозміни

The purpose. To determine rational alternatives of fertilizer system and rotation of crops of grain-tilling link of 10-field crop rotation for preserving soil fertility, restoring the content of humus and heightening values of agrochemical indexes of soil. Methods. Field test, physical and chemical, agrochemical. Results. Agrochemical researches were carried out in formation of fertility of typical deep chernozem in links of field crop rotation depending on system of fertilizing. Use during 40 years of organic-mineral systems of fertilizing in grain-beet crop rotation has not ensured restoration of the content of humus in typical chernozem up to the level of layland. At importation of decomposed manure in dose of 8,3 t/hectare + N29.3P45K36.7 the content of humus in arable layer on completion of 4 rotations made 4,59%; 16,7 t/hectare of decomposed manure + N29.3P45K36.7 — 4,72%, and in layland — 5,20%. Application of decomposed manure in dose of 8,3 t/hectare + N29,3P45K36,7 has ensured to the end of 4-th rotation the content of mineral nitrogen in arable layer in the link barley-pease-sugar beet — 19,1 mg/kg of soil; in the link vetch-oats-winter wheat-sugar beet — 16,4 mg / kg of soil. At increase of dose of fertilizers up to 8,3 t / hectare of decomposed manure + N36P85K76.7 — 21 mg / kg of soil. That exceeds initial indexes on 8,1; 5,4 and 10 mg/kg of soil. Resources saving fertilizer system (8,3 t/hectare of decomposed manure + N29,3P45K36,7) formed to the end of 4-th rotation the heightened content of mobile phosphorus in arable layer — 119,3 mg/kg of soil, at increase of dose of fertilizers up to 8,3 t / hectare of decomposed manure + N36P85K76.7 mg/kg of soil — its content reached 200 mg/kg of soil. At importation during 4 rotations of decomposed manure in dose of 8,3 t / hectares + N29.3P45K36.7 the content of mobile potassium in arable layer made 129,2 mg/kg of soil; 8,3 t/hectare of decomposed manure + N36P55K46.7 — 145,1 mg/kg of soil. That exceeded initial indexes accordingly on 18,9; 35 mg/kg of soil. Long use during 40 years of organic-mineral system of fertilizing caused acidification of soil solution. At importation of decomposed manure in dose of 8,3 t/hectares + N36P35K46.7 pHsalt in comparison with layland decreased on 1,0–1,2, Ng increased on 2,2–2,4 smol/kg of soil, at absolute values — accordingly on 5,2–5,3 and 4,0–3,6 smol/kg of soil. Conclusions. Use of organic-mineral system of fertilizing in dose of 8,3 t/hectare of decomposed manure + N29.3P45K36.7 on typical deep chernozem in the link of field crop rotation promotes optimization of agrochemical nature of soil and preserves its fertility.

The potential of digestate as a biofertilizer in eroded soils of Lithuania

The objective of this work was to determine the potential of using of solid and liquid digestate, as biofertilizer and soil amendment, and to address adverse unfertile soil erosion problems after analysing areas of potential use. We found a high concentration of organic carbon in a solid fraction of the digestate, which indicates a significant potential for returning carbon to the soil. The influence of digestate fertilization on soil fertility as a function of the amount of available phosphorus (P2O5) and potassium (K2O) in the 0–40 cm layer was found to be very important. The soil fertility category was changed from “high” (200–300 mg kg−1) to “very high” (>300 mg kg−1) according P2O5, using only 170 kg ha−1 of nitrogen in solid and liquid digestate rate. Fertilization with all phases and rates of digestate tend to increase the amount of K2O. The solid digestate fertilization using the 170 kg ha−1 N rate showed a significant increase (5 times) of mineral nitrogen content in the 0–40 cm soil layer. The advantage of solid digestate as a soil improver has been highlighted because it has a positive effect on soil fertility, quality, sustainability and durability. The amount of mobile humic acids (MHA) in eroded loamy Retisol increased 1.6 times in soil 0–40 cm layer with a fertilization rate of 170 kg ha−1 and 1.5 times – of 85 kg ha−1 of solid digestate compared to the untreated. Similar trends of MHA but in lower amount were identified when liquid digestate was applied.

Post-harvest residues of field pea/oat mixtures as a source of biological nitrogen for hybrid winter rye

ABSTRACTThe conducted studies show post-harvest residues of sowing/pea mixtures limit leaching of mineral nitrogen deeper into the soil profile compared to post-harvest residues of sowing peas, as they affect the yield and amount of nitrogen accumulated in hybrid winter rye grain. The objective of the study was to determine the effect of the post-harvest residue biomass of field pea, oat and their mixtures on yielding and quantity of nitrogen accumulated in hybrid winter rye grain. Two factors were examined: factor I − post-harvest residues of field pea 100% − pure stand, oat 100% − pure stand, field pea 75% + oat 25%, field pea 50% + oat 50%, field pea 25% + oat 75%; factor II − forecrop harvest date: the stage of field pea flowering, the stage of field pea flat green pod. The obtained results demonstrated that the lowest mineral nitrogen content in two soil layers was recorded following oat harvested at the stage of field pea flat green pod. The research revealed that hybrid winter rye cultivated after the mixture consisting of 50% field pea and 50% oat should be recommended for wide agricultural application in order to obtain high grain yield.

Mineral nitrogen content in hydrographic areas of Poland depending on land use

Mineral nitrogen content in hydrographic areas of Poland depending on land use

Effect of autumn nitrogen fertilization on winter oilseed rape growth and yield parameters

Autumn fertilization of winter oilseed rape with nitrogen was monitored in exactly delimited small field experiment in the period of 2013/14–2015/16. The cultivar used was DK Exstorm, sowing amount: 50 seeds/m<sup>2</sup> and fertilizer applied in autumn was Ureastabil – granulated urea with urease inhibitor (NBPT). The application period was at the end of October, doses 40 and 80 kg N/ha. Research results confirmed a statistically important effect of autumn fertilization on growth of the above-ground biomass and roots. Statistically important effect on seed yield was confirmed, too. The dose of 40 kg N/ha resulted in the highest seed yield, on average by 10.6% higher than reference (5.7–6.5 t/ha). On the other hand, the dose of 80 kg N/ha increased the seed yield only by 7.4% on average (5.4–6.3 t/ha).Fertilization effects on the oil content and one thousand seeds’ weight were statistically insignificant. The results show that considering the given local and weather conditions and low mineral nitrogen content in the soil, the most suitable nitrogen dose for autumn fertilization is 40 kg N/ha. This dose follows the nitrate directive rules, supports oilseed rape strengthening before winter and intensifies it for better seed yield.

Trade-offs between residue incorporation and K fertilizer on seed cotton yield and yield-scaled nitrous oxide emissions

Crop residues can effectively replace inorganic potassium (K) fertilizers to increase crop yield. However, the effect of incorporating consecutive crop residues instead of applying inorganic K fertilizers on seed cotton yield and yield-scaled N2O emissions (N2O emissions per unit yield of seed cotton) over a long period has rarely been reported. Therefore, a six-year (2011–2016) study incorporating crop residue instead of applying inorganic K fertilizer was conducted in a cotton-wheat system (transplanting cotton after wheat harvesting within the same crop season). Results showed that no statistical difference was observed between crop residue treatments and K fertilizers application on seed cotton yield during 2011–2014. However, in 2015, the yields of the inorganic K treatments were superior to the yields of the residue retained treatments. In 2016, the residue retained treatments and inorganic K treatments had similar seed cotton yields except that the K300 (300 kg K2O ha−1) treatment had a significantly higher yield than the 9000 kg ha−1 wheat straw + 7500 kg ha−1 cotton residue treatment (C7500 + W9000). The seasonal N2O emissions and yield-scaled N2O emissions increased by 1.01–1.65 times and 1.02–1.94 times in residue incorporation compared with inorganic K application treatments during 2015 and 2016 (the fifth and sixth year of residue incorporation), respectively. Furthermore, the soil N2O fluxes were significantly correlated with soil dissolved carbon and available mineral nitrogen contents. In conclusion, crop residue as a K source is a suitable alternate to enhance cotton yield and to replace inorganic K fertilizers but this could also boost the soil N2O fluxes, seasonal N2O emissions, and yield-scaled N2O emissions.

Interaction effects of nitrogen and phosphorus fertilizer on nitrogen mineralization of wheat residues in a calcareous soil

Because of the high pH of the soil in semiarid regions, phosphorus adsorption is unfavorable. So, considerable amounts of phosphorus fertilizers are used annually, where this fertilizer may affect the plant residues' decomposition. To examine the interaction effects of nitrogen and phosphorus on nitrogen mineralization in calcareous soil, a factorial experiment was performed in a completely randomized design with three replications. The first factor consisted of various C:N ratios (20, 40, and 60 or three levels of nitrogen N1:0, N2:11, and N3:43 kg N ha−1, respectively) and the second factor consisted of various C:P ratios (87, 174, and 260 or three levels of phosphorus P1:0, P2:12, and P3:45 kg P ha−1, respectively), under incubation conditions. The results indicated that the cumulative mineral nitrogen content in all treatments, except for N1P2 and N1P3 treatments, started from a positive amount and remained positive until the end of the incubation period. The highest amount of cumulative mineral nitrogen among treatments was related to N3P1 treatment, while the lowest was associated with N2P3 treatment. Mineralization of nitrogen during 60 d of incubation was the dominant phenomenon, except for the N1P2 and N1P3 treatments which remained in the organic phase. The effect of phosphorus on the cumulative mineralization of nitrogen was significant. With increasing the amount of phosphorus, the total inorganic nitrogen diminished. Nitrogen release begins earlier with lower C:N ratios, and therefore the available nitrogen can be released more quickly to the plant. It is generally concluded that, in calcareous soil, the use of nitrogen fertilizer to adjust C:N ratio and to improve the mineralization of wheat residues will be a suitable option.

RETROSPECTIVE AND MODERN CONDITIONS OF THE CHERNOZEMS OF THE NYZHNIODNIESTROVSKAYA IRRIGATION SYSTEM

Problem Statement and Purpose The experience of the using large-scale regular irrigation in the south of Ukraine shows that along with the positive productive effect of irrigation, there is a worsening of the ameliorative state of irrigated soils. In the present conditions of a significant decrease in the actual irrigated lands andthe intensity of irrigation on the background of the extension of agriculture, there is an increasing need to monitor and evaluate the reclamation-resource state of the soil in order to develop timely environmental measures. Accordingly, the purpose of the article is to assess the ameliorative-resource state of the southern chernozems and modern trends of its change.Data & Methods. The studies were carried out on the territory of land use of “Agrofirm Petrodolinskoe” of the Ovidiopolsky district of the Odesa region, which is located within the Nyzhniodniestrovskaya irrigation system. Laboratory and analytical studies were performed according to standard certified methods followed by statistical processing, which included determining the salt composition of the aqueous extract, physical and chemical properties of the soil and the humus, mineral nitrogen, mobile phosphorus and potassium contents in the soil (according to the method of Machigin).Results. According to the results of the study, the southern chernozems of the Nyzhniodniestrovskaya irrigation system are classified as non-degraded because of the risk of irrigation salinity. With a decrease in the intensity of irrigation and its periodic use, the content of carbonates significantly increases and the boiling line increases from 10% HCl to 76 cm with systematic irrigation to 57 cm in recent years. Soil alkalinity occurs throughout the study territory. In the conditions of decreasing the intensity of irrigation and extensification of agriculture, disaggregation is noticeable like consolidation of the composition of the upper horizons of the soil. A decrease in the degree of aggregation and the potential ability for the structuring of southern chernozems is established in the southern chernozems. According to the results of the analysis of the retrospective and modern state of chernozem in the southern Nyzhniodniestrovskaya irrigation system, a general pattern of degradation of their agrochemical properties has been established. During the investigated period, the humus contents in the upper horizons decreases to 0,1 %. In the present economic conditions of land use there is a decrease in the mineral nitrogen and mobile phosphorus contents in soils, the spatial variability of phosphorus and potassium contents is reduced, while the distribution of mineral nitrogen contents remains significantly heterogeneous. Despite of some changes, the southern chernozems are suitable for irrigation, but with agromeliorative measures to maintain and increase their fertility.

Leek production in conventional and organic arable-vegetable rotations in the Netherlands

Leek production, one of the most important vegetables grown on the sandy soils in the South East of the Netherlands, is known to have a high rate of nitrogen leaching. Nitrogen leaching from leek cultivation depends not only on the cropping strategy but also on the whole farming system. The objective of this study was to evaluate nitrogen losses and crop yield of leek cultivation and the total farming system with different fertilization strategies. A farming systems experiment with two conventional and one organic farming system with arable and vegetable crops on sandy soils was evaluated. One conventional farming system (LOW) had a low organic matter input consisting of crop residues and green manure crops only. The other conventional farming system (STANDARD) had a regular organic matter input including cattle and pig slurry. The organic system had a high organic matter input because of the use of farm yard manure and cow slurry. Data of crop yield, nutrient balances and nitrate leaching for the period 2011-2016 are discussed. In the LOW system, crop production was on average 5% lower than in STANDARD. Nitrogen surplus was lower in LOW than in STANDARD. Phosphorus surplus was about equal between the systems and potassium surplus was higher in LOW than in STANDARD. Nitrate leaching was comparable in LOW and STANDARD, but both above the limit set in the EU nitrates directive of 50 mg L-1. Other indicators of nitrogen leaching as soil mineral nitrogen content and nitrogen surplus indicate that leaching risk in LOW is lower than in STANDARD. Leek yield in the organic system was low because of incidences of pests and diseases. However, in years with low disease pressure yields were only a few percent lower compared to the conventional yields. Nutrient surpluses of N, P and K were high in the organic system. Nitrogen leaching was below 50 mg L-1 in the organic system. A dilemma still exists between crop yield and nitrate leaching in the conventional systems: lower nitrate leaching is coupled with lower crop yields. The organic system gives relatively low yield however with good results regarding nitrate leaching.

Microbial and enzyme analysis of soil after the agricultural utilization of biogas digestate and mineral mining waste

The intensity of organic matter transformation in soil may be subject to various factors, especially to the previously applied non-standard chemical-based fertilizers. The objective of study was to assess the number of selected groups of microorganisms and enzymatic activity in soil after waste utilization. Biogas digestate (1.5 and 3.0%) and mineral mining waste (10 and 20%) were added to podzolic soil. The results demonstrated that the application of these wastes increased the number of microorganisms in the soil. 20% mineral mining waste provided the most favorable conditions for the development of oligotrophs and copiotrophs, whereas 3% biogas digestate most positively affected the total number of bacteria. This waste increased soil enzyme activity proportionally to the applied concentration. The highest activity was obtained for 1.5% biogas digestate. The number of oligotrophs, copiotrophs, and proteolytic microorganisms correlated positively with pH, organic carbon content, total nitrogen, and micronutrients present in the soil, while negatively with phosphorus content. The activity of the majority of enzymes was positively correlated with the content of mineral nitrogen, phosphorus, and potassium. In this study, we were not able to demonstrate a negative correlation between the content of heavy metals and the number of microorganisms in the soil. These results suggest that biogas digestate and mineral mining waste can be used in agricultural practice to improve microbial activity of the subsoil with a large reserve of safety for the soil environment.

Effects of soil wetness and tyre pressure on soil physical quality and maize growth by a slurry spreader system

Slurry spreaders are among the heaviest machines used for farming operations. The effects of soil wetness and tyre pressure on physical soil properties were evaluated by using a ˜5 Mg wheel load slurry spreader mounted on a tractor. The impacts were also compared with Terranimo® model predictions and X-ray micro-computed tomography (X-ray micro-CT) parameters. In the consecutive maize growing season, soil physical properties, total mineral nitrogen content and maize above biomass were evaluated additionally between in and out track positions. Immediately after traffic, penetration resistance (PR) was significantly higher (P < 0.05) under moist conditions and at in-track positions compared with dry conditions and out-track positions for the top 10 cm. Tyre pressure did not affect PR at in- or out-track position. At 10 cm depth, bulk density and macro-porosity (d> 30 μm) of soil trafficked under moist conditions was different (P ≤ 0.10) from those under dry conditions. Macro-porosity showed a clear response (P < 0.10) to tyre pressure and all the trafficked treatments. Deeper in the profile, there were no significant differences in these soil physical quality indicators. X-ray micro-CT results agreed well with the soil physical quality indicators, and detected slight changes in degree of compaction more precisely. Terranimo® well predicted the contact area and mean ground pressure (RMSE=0.06 m2). It indicated considerable compaction risk from the tractor’s rear wheels, which seemed to contradict with the relatively minor changes in soil physical properties observed. In the maize growing season, soil physical properties and nitrogen content showed no significant differences (P > 0.05) between in- and out-track positions while above ground dry biomass of maize reduced with ˜7% at in-track positions.

Carbono orgânico e nitrogênio do solo sob alturas de pastejo da Urochloa ruziziensis em sistema agropastoril

A matéria orgânica do solo é essencial dentro do sistema agrícola e seu acúmulo pode ser favorecido pelo aporte de resíduos vegetais sobre o solo. Objetivou-se avaliar o efeito da altura de pastejo de Urochloa ruziziensis nos teores e estoques de carbono orgânico e nitrogênio do solo, em sistema agropastoril, em Latossolo Vermelho Distrófico típico. Para o estudo foram coletadas amostras de solo entre os anos de 2010 e 2012. O delineamento foi em blocos casualizados em parcelas subdivididas no tempo e cinco tratamentos, constituídos pelas alturas de pastejo: 10; 20; 30 e 40 cm e mais uma área não pastejada de Urochloa ruziziensis, e três repetições. Determinou-se nas camadas do solo (0-10, 10-20 e 20-30 cm de profundidade) o teor e estoque de carbono orgânico total, carbono orgânico particulado, carbono orgânico associado aos minerais, teor e estoque de nitrogênio total e o teor de nitrogênio mineral. As variáveis estudadas foram submetidas à análise de variância pelo teste F e as médias foram comparadas pelo teste de Tukey, ambos, ao nível de 5% de probabilidade. Os teores e estoques de carbono orgânico total e suas respectivas frações, os teores de nitrogênio total e mineral do solo, além, dos estoques de nitrogênio total do solo, não foram alterados pelas alturas de pastejo e a área não pastejada. Todavia, na camada 0-10 cm, ocorreu aumento dos teores e estoques de carbono orgânico total, carbono orgânico associado aos minerais e redução do carbono orgânico particulado do solo, e, também, aumento dos teores e estoques de nitrogênio total entre o primeiro e o segundo ano de condução, sob plantio direto. Houve aumento dos teores de nitrogênio mineral após a colheita da soja para todas as camadas do solo.

Short-term changes in chemical and microbial characteristics of paddy soil in response to consecutive addition of organic ameliorants in a rice–rice–vegetable rotation system

ABSTRACT With regard of the problems of soil acidification and soil degradation caused by high intensive planting in south China, a 2-year pot experiment consisting of six harvests under a rice–rice–vegetable rotation cropping system was conducted to assess the effects of NPK+ rice straw (RS) and combined application of RS with peanut bran, biochar, and organic fertilizer on soil chemical and microbial characteristics in paddy soil. The control treatment received chemical fertilizer alone. Results showed that RS and the combination of RS with organic ameliorants, especially NPK+ rice straw + biochar (RSBC) treatment led to the greatest improvement of soil pH, soil organic carbon, microbial biomass carbon, and total nitrogen (TN) content, and urease (UE), acid phosphatase (ACP) and catalase (CAT) activities concurrently without yield sacrificing, which inferred that RSBC treatment could be an effective measure to alleviate soil acidification, boost carbon sequestration and nutrients content as well as soil enzyme activities in rice-rice-vegetable rotation system. Besides, Pearson’s correlation analysis showed that soil mineral nitrogen (Nmin) content was negatively related to pH, and the available potassium (AK) content was positively related to UE and CAT activity but negatively related to ACP activity. Canonical correspondence analysis demonstrated the Nmin and AK explained 27.2% and 13.7% of the variation in microbial species, respectively. Therefore, it is believed that soil Nmin and AK content could be the primary factors of soil microbial properties under the rice-rice-vegetable rotation system.

Moderate grazing increases the abundance of soil methane-oxidizing bacteria and CH4 uptake rate in a typical steppe of Inner Mongolia, China.

Microbial oxidation is the only biological sink of atmospheric methane (CH4). It is essential to understand the variation of CH4 fluxes among different grassland use types for developing low-emission management system. Here, we measured the CH4 flux and the soil methane-oxidizing bacteria abundance in a typical steppe under grazing, mowing and fencing management in central Inner Mongolia, with the aims to determine the effects of these grassland use types on CH4 flux, and to test the hypothesis that pmoA functional gene abundance regulates CH4 fluxes. The measurements were conducted on the experimental grassland that had experienced four grassland use treatments over five years. The treatments were whole growing season grazing from May to September (T1), spring and summer grazing (twice in May and July)(T2), autumn mowing (T3) and enclosure (T0). We measured CH4 flux using static chamber method, and quantified the abundance of pmoA functional genes using molecular techniques. Moreover, we measured plant biomass and soil physicochemical properties. The results showed that moderate grazing significantly enhanced CH4 uptake rate and the methane-oxidizing bacteria abundance (i.e., the pmoA gene copy number per gram of dry soil). The pmoA gene copy number ranged from 6.9×104 to 3.9×105 per gram of dry soil in growing season. The CH4 uptake rate was (68.21±3.01) μg·m-2·h-1 under T1, which was 22.1%, 37.5% and 30.9% higher than that under T2, T3 or T0 , respectively. The CH4 uptake rate was positively correlated with abundance of CH4 oxidizing bacteria and soil sand content, but negatively correlated with soil silt content, soil moisture, NH4+-N and NO3--N content, and plant biomass. These results suggested that the steppe ecosystem is a CH4 sink under all land-use types in central Inner Mongolia, and that moderate grazing would enhance methane-oxidizing bacteria abundance and CH4 uptake by improving soil sand content, reducing soil mineral nitrogen content and plant production in the typical steppe ecosystem. These results were of significance for the development of low-emission grassland management system.

Effects of Reduced Tillage on Weed Pressure, Nitrogen Availability and Winter Wheat Yields under Organic Management

Reduced tillage reduces soil erosion and increases topsoil organic matter compared with conventional tillage. However, yields are often reported to be lower, presumably, due to increased weed pressure and a slower N mineralization under organic farming conditions. The effects of reduced tillage compared with ploughing on weed infestation and winter wheat performance at four different crop stages, i.e., tillering, stem elongation, flowering, and harvest, was monitored for a single season in an eleven-year-old organic long-term tillage trial. To disentangle the effects of weed presence on crop yield and potential crop performance, subplots were cleaned from weeds during the whole cropping season. Weed biomass was consistently higher under reduced tillage. Soil mineral nitrogen contents under reduced tillage management were higher, which could be explained by the earlier ley termination in autumn compared with the conventional tillage system. Nitrogen status of wheat assessed with SPAD measurements was consequently higher under reduced tillage throughout the season. At harvest, wheat biomass and grain yield were similar in both tillage systems in the presence of weeds, but 15–18% higher in the reduced tillage system when weeds were removed. The negative impact of weeds on yields were not found with conventional tillage with a low weed infestation. Results suggest that reduced tillage can provide equivalent and even higher yields to conventional tillage in organically managed winter wheat if weed management is improved and good nutrient supply is assured.

NITROGEN REGIME OF PEAT SOIL IN NORTHERN PART OF TRANS-URALS ZONE

The paper highlights the results of many-year (1982-1992, 2011-2014 гг.) research on the concentration of mineral nitrogen in the arable medium peat soil layer of the forest-steppe of Trans Urals zone. The research was carried out on the experimental-reclamation system Reshetnikovo located in the central part of the Tarman bog on the second lacustrine-alluvial basin of the Tura River in Tyumen region. The soils on the experimental plot have a slightly acidic reaction (5.2 - 5.9), relatively low hydrolytic acidity (28.1 - 40.8 mg-eqv/100 g of soil), relatively low degree of base saturation (61.7 - 75.5%), high gross nitrogen concentration (3.1 - 3.9%), low concentration of phosphorus (0.09 - 0.14%) and potassium (0.02 - 0.05%). The researchers found out that mineralization of peat is slow and almost always fails to provide sufficient and continuous supply of nitrogen, despite its large gross reserves. Due to insufficient number of mobile nitrogen compounds from peat organic matter during the growing season it is necessary to apply nitrogen fertilizers. When peat soils contain low concentrations of phosphorus (0.7 - 3.7 mg/100 g of soil), the highest number of nitrate nitrogen is accumulated in the arable layer under perennial grasses due to its low consumption for the yield. Re-reclaimed peat soil is characterized by negative nitrogen concentration. As perennial grasses require nitrogen, it is fulfilled by means of fertilizers on 41.4 - 72%. The authors observed a tendency of reducing nitrate reserves under perennial grasses even if nitrogen fertilizers are applied. This indicates a decrease in the mineralization rate of peat organic matter. The ammonium nitrogen concentration increases. Discontinuance of nitrogen fertilizers use reduces the nitrate nitrogen concentration on 30-49% in the first year and on 46.7-59.1% by the end of the fourth year of after-effect. The amount of ammonium nitrogen increases in 1.6-3.7 times in 4 years.

Using RapidEye imagery to identify within-field variability of crop growth and yield in Ontario, Canada

Remote sensing has been recognized as a cost-effective way to detect the spatial and temporal variability of crop growth and productivity. In this study, multispectral RapidEye images were used to delineate homogeneous zones of soil and crop development in two fields in Ontario, Canada, one planted with canola (Brassica napus L.) and the other with spring wheat (Triticum aestivum L.). The two fields received different levels of nitrogen (N) treatments during the pre-planting land preparation phase. Soil textures, mineral nitrogen content and crop yield were used to interpret the results of zone delineation. The analysis of variance (ANOVA) tests revealed that the high-resolution RapidEye data, particularly the imagery acquired at peak crop growth stages (i.e. when leaf area index (LAI) is high), provided valuable information for delineating within-field variability of crop growth and yield. Further analysis showed that for both crops, the spatial patterns of crop growth condition varied throughout the growth cycle, revealing different impacts of soil properties and N fertilization on the crops. In particular, during peak growth stage, the within-field variability was most strongly affected by the pre-planting N application and had the strongest correlation with crop yield. These results suggest that high-resolution satellite data (e.g., RapidEye) could assist in making decisions on optimal N fertilization for enhanced crop productivity.

Effects of conventional moldboard and reduced tillage on seasonal variations of direct CO2 and N2O emissions from a loam Haplic Luvisol

Greenhouse gases such as N2O and CO2 are formed in microbiological processes of nitrification and denitrification and also governed by microbial decomposition of soil organic matter (SOM) plant residues. A key factors influencing these processes are temperature and soil moisture. Therefore the objectives of this study were to: (1) evaluate the seasonal variations in SOM content, temperature, water-filled pore space (WFPS) and mineral nitrogen content under conventional tillage (CT) and reduced tillage (RT) system, and (2) assess the direct CO2 and N2O emissions associated with the seasonal variations in the soil properties under both tillage systems. An experiment was carried out in a randomized blocks with two different tillage system: CT and RT in a Haplic Luvisol (loamy) covering the growing season of spring barley. Each block included treatments: no mineral fertilizers; mineral fertilizers; mineral fertilizers plus plant residues. Overall, the SOM content and temperatures were insignificantly higher in the plough layers of RT than CT during the entire period of study. Soil moisture content (SMC) and WFPS were insignificantly higher in CT than RT. The application of mineral fertilizers resulted in a significant increase of mean NO3− concentrations only in the plough layers of CT. SMC was a stronger driving factor of mean daily CO2 emissions in all treatments, while variations in soil temperatures and SMC were jointly responsible for changes in mean daily N2O emissions in all the treatments of CT and RT. The postponed highest peaks of mean daily N2O emissions from RT were observed under aerobic soil conditions several days after the heavy rainstorm. The cumulative CO2 and N2O fluxes were insignificantly higher from CT than RT over the entire period of study.