Cm Layer Of Soil Research Articles

POTENTIAL CONTAMINATION OF SOYBEAN AGROPHYTOCENOSIS DEPENDING ON THE SYSTEM OF FARMING AND SOIL TILLAGE

This work presents the results of the study of changes of the potential contamination of soybean agrophytocenosis in grain-row crop rotation by using different systems of farming and typical black soil tillage. It was established that in the upper 0–5 cm layer of soil there are on average 393–671 million pieces of weed seeds. which is 33.6–43.0% of the total number in the layer of soil 0–20 cm. It was established that the use of periodical moldboard and superficial basic soil tillage had no impact on reducing the potential contamination of typical black soil compared to the variant of differentiated tillage. During subsurface plowing the total number of seeds in the soil layer 0–20 cm increased by 13.5–25.8% compared to differentiated tillage. In the variants of ecological and biological farming systems the number of weed seeds in the layer 0–5 cm was 11.3–19.6% higher compared to the intensive farming system. Based on monitoring of the species composition of the weed seeds bank it was established that in the arable layer of the soil the largest share are annual dicotyledonous – 48–62%. annual monocotyledonous – 30.2–44.6%. perennial – 0.9–3.3% of the total number. It was proved that under the intensive system of farming the yield of soybean variety Silesia increased on average from 10.2 to 147% compared to the ecological and biological system of farming. During the biological system of farming soybean yield did not exceed 1.0–1.8 t/ha. Therefore. the industrial and ecological system of farming had the greatest impact on reducing the potential weediness of the soybean agrocenosis during the growing season. During the biological system of farming crop yields decrease due to the accumulation of weed seeds in the topsoil and formation of high actual weediness of the soybean agrocenosis.

Nutritional regime of gray forest soil аt different anthropogenic loads

The aim of the research is to establish the peculiarities of the formation of the nutrient regime of gray forest soil with different systems of basic cultivation, fertilization and sealing of by-products of crops in short-rotation 4-field grain crop rotation – winter wheat–corn for grain–barley–soybean. Evaluate the quantitative inflow of biomass, participation in the formation of the nutrient regime of gray forest soil, especially the differentiation of 0–40 cm of soil layer depending on the distribution of nutrients in different tillage soil systems. The studies were carried out in a long-term stationary experiment of the department of soil cultivation and weed control of the NSC «Institute of Agriculture of the NAAS», founded in 1969. The fertilization system consisted of the application of mineral fertilizers N65Р58К68 kg acting things per 1 ha of crop rotation area. As an organic fertilizer, we used by-products of crop rotation, where during 2009–2013 received an average of 5,17–5,50 t/ha, and 2014–2017 – 6,65–7,76 t/ha of crop rotation. The existing yield of the main product significantly influenced the volume of the non-commodity part, with the growth of the main product, the growth of by-products also took place in direct proportion. Nitrogen removal averaged 105 kg/ha, and with biomass it returned on average 55,4 kg/ ha, nitrogen with a full mineralization cycle, in general, this corresponds to 45–47 % of the share of costs. In general, the return of phosphorus from by-products for the rotation of 5 received an average of 12,0–16,7 kg/ha and 4-field crop 26 rotation 19,5–22,0 kg/ha, which was 35–40 % of the total removal harvest. The soil received many times more potassium from the biomass of agricultural crops than part of the cost of the main product, due to the attraction of the maize leaf mass, from which an average of 177–253 kg/ha enters the soil, and for crop rotation – 61,4–95,4 kg/ha per hectare of sown area. Key words: gray forest soil, soil nutrient regime, recycling of nutrients, main and by-products of crops.

Forms and balance of soil potassium from a long-term integrated crop-livestock system in a subtropical Oxisol

The presence of animal grazing at different intensities in integrated crop livestock systems (ICLS) may affect the forms and the balance of K in the soil, especially after many years. The objective of this study was to evaluate different K forms and their balance for 17 years with ICLS. ICLS experimental area used no-till practices with different grazing intensities of cattle in winter pasture (black oat + annual ryegrass) and soybean production in the summer season. The experiment started in May 2001 at a location with a Rhodic Hapludox (Oxisol). The treatments consisted of varied grazing intensities: intensive grazing (IG) at 10 cm of pasture height, moderate grazing (MG) at 20 cm of pasture height, and a no grazing (NG) treatment. The experimental design was a randomized block design with three replicates. Soil samples were collected in 2001, 2007, 2012 and 2017 in 0−5, 5−10, 10−15 and 15−20 cm of soil layers. Desorption of K was measured using the Mehlich-1 method and the results were fitted to first-order kinetic equations to obtain readily and potentially available K content. Total K was determined by X-ray fluorescence, and the unavailable K by the difference between the total K and potentially available K. Long-term no-till ICLS resulted in an increase in more readily available K forms in the soil surface. The increase was especially prominent in the no-grazing treatment due to the greater amount of K left in the plant residues. Regardless of grazing intensity, soybean cultivation was the controlling component of the soil nutrient budget, representing 98.6 % of the total amount of K exported. Animal outputs represent only 1.4 % of total K exported and are therefore the recycling component of the system. Although meat production in ICLS represents only a very small fraction of the amount of K exported from the system, K tends to become less available in the grazed treatments in the long-term.

Liquid swine manure as a sidedressed nitrogen source for corn

AbstractSidedressing liquid swine (Sus scrofa) manure (LSM) on corn (Zea mays L.) may provide additional time to apply manure and help better match crop‐nutrient demand with nutrient supply. A 2‐yr, on‐farm study was conducted in Minnesota to assess three sidedress nutrient sources—injected LSM via dragline hose, anhydrous ammonia (AA), and urea ammonia nitrate (UAN)—against a non‐sidedressed control. At planting, all treatments (including the control) received 46 kg N ha−1 as starter fertilizer. At sidedressing, 157 kg N ha−1 of available N was targeted for application with the different N sources at the fourth leaf collar stage of corn (V4). Sidedressing did not affect plant population compared with the non‐sidedressed control in 2018, but sidedressed LSM reduced plant population by 6% relative to the control in 2019, likely due to wet soil conditions and manure injection settings that partially buried plants. In 2018, LSM produced comparable grain yield and net return to sidedressing costs as AA and UAN, despite lower soil ammonium and nitrate levels in the 0‐ to 15‐cm soil layer approximately 12 d after application. In 2019, LSM led to 18–25% lower grain yield than AA and UAN and lower net returns because of a combined plant population reduction and an application of 50 kg plant available N ha−1 less than expected. Sidedressing corn with LSM is a viable alternative to commercial fertilizers, although to realize consistent results, better fine‐tuning of application rate, depth, and speed under different soil moisture conditions may be needed.

Soil carbon and associated bacterial community shifts driven by fine root traits along a chronosequence of Moso bamboo (Phyllostachys edulis) plantations in subtropical China

Moso bamboo (Phyllostachys edulis) is widely considered to be effective in capturing and sequestering atmospheric C, but the long-term effects of extensive management strategies on soil organic carbon (SOC), bacterial communities, fine root (FR, ø ≤ 2 mm) traits, and their inherent connection remain unclear. In this study, we simultaneously measured the SOC content of the bulk and rhizosphere soil fractions, the aggregate stability, the chemical composition of SOC (solid-state 13C nuclear magnetic resonance [NMR]), the bacterial community structure in the rhizosphere, and the FR morphological traits including biomass, specific root length (SRL), and root length density (RLD) along a chronosequence (stand age of 19, 37, and 64 years) of extensively managed Moso bamboo plantations and in an adjacent secondary forest as a control. The organic C content in both the rhizosphere and bulk soil increased rapidly with plantation age in the 0–20- and 20–40-cm soil layers, accompanied by an increase in the aggregate stability. FR traits including biomass, SRL, and RLD also increased continuously in response to soil C:N:P stoichiometry. All of these traits were significantly correlated with SOC, occluded particulate organic C (oPOC), and mineral-associated organic C (MOC), suggesting that FR traits could drive the soil C sequestration with the plantation age. Further analysis indicated that the microbial biomass C (MBC) content, MBC/total organic carbon (TOC) ratio, and bacterial abundance decreased with the plantation age, and the shift from soil oligotrophy to copiotrophy bacteria were mainly driven by changes in FR traits and SOC properties. Such a reassembly of bacterial communities combined with an increase in root biomass is favorable for the accumulation of stable C functional groups (alkyl C or aromatic C). Our findings indicate that extensive management regimes of Moso bamboo plantations could promote long-term soil C sequestration especially in the rhizosphere by promoting the formation of soil aggregates and organic-mineral complexes and by shifting bacterial community composition, and that these changes can be inferred through changes in the FR traits.

Effects of manure on topsoil and subsoil organic carbon depend on irrigation regimes in a 9-year wheat-maize rotation

On the North China Plain, low soil organic carbon (SOC) content and a consistently dropping underground water level are seriously threatening food production security. To date, the interactive effect of fertilization types and irrigation regimes on surface and subsurface SOC contents has rarely been quantified. Here, we conducted a field study of three irrigation regimes with two fertilization types between 2009 and 2018. The three irrigation regimes included presowing irrigation (W0); presowing and jointing irrigation (W1); and presowing, jointing and anthesis irrigation (W2). The two fertilization types were mineral fertilizer only (CF) and mineral fertilizer plus composted chicken manure (CFM). Soil samples were collected from a depth of 0−100 cm in 20-cm increments to measure SOC and its composition, including labile pool I (LPI) (polysaccharides), labile pool Ⅱ (LPⅡ) (cellulose), and recalcitrant pool (RCP). Four SOC-related enzymes were determined, i.e., α-glucosidase, β-glucosidase, peroxidase and polyphenol oxidase. Stable carbon isotopic (13C) analysis was determined to distinguish the contributions of wheat- and maize-derived SOC in a wheat-maize rotation. The results showed that the 0−20-cm SOC content was highest in the W0 + CFM treatment. In the 0−20-cm layer, SOC decreased from W2 to W1 or W0 under CF, which is attributed to a reduction in the labile pool and maize-derived C and higher polyphenol oxidase. Conversely, under CFM, the 0−20-cm SOC content increased following decreased irrigation from W2 to W1 and from W1 to W0, mainly due to the increased LPⅡ and RCP. Compared with CF at W0 and W1, the 0−20-cm SOC content increased by 30.5 % and 21.8 % under CFM, respectively. Relative to the 0−20-cm soil layer, the SOC stock was larger in the 20−100-cm layer, which of the treatments had a variation manner similar to the 0−20-cm soil layer. Our results suggest that reduced irrigation regimes have significantly reduced the SOC stock and altered its composition in the 0−100-cm soil layer under CF and that CFM can increase the SOC stock in this layer when reducing the irrigation regime.

A long-term study on the soil reconstruction process of reclaimed land by coal gangue filling

The main problem hindering the land reclamation process is the lower quality and long recovery period of reclaimed soil. Soil is a complex ecosystem and it is difficult to describe the state of soil reconstruction state. In this paper, we applied complex network theory to characterize the development and the mutual influence of soil quality variables in the 0–20-cm soil layer at 1, 3, 5, and 10 years after reclamation. In each study period, five samples were collected from the area reclaimed with coal-gangue fill and from the neighbour undamaged land. Fifteen soil quality-related variables of each sample, including soil physical, chemical, and biological parameters were determined. Five networks were constructed for 1-, 3-, 5-, and 10-year reconstructed soil and the control group. Each network had 15 soil quality-related variables as nodes, correlation coefficients of the variables as the criterion of the edge, and absolute values of the coefficients as the edge weight. The topological parameters were calculated and compared among these five networks. Compaction is the key indicator that can be used as a sensitive indicator for evaluating the quality of reclaimed soil. After 10 years of reconstruction, the soil variables have almost returned to the undamaged state, but the reclaimed soil is more fragile due to the stronger correlation between variables. The variables that have the greatest direct, indirect, and most rapid impact on soil quality varied with the reconstruction process, but the soil organic matter is the major direct impact indicator, soil texture (sand and clay) is the major indirect impact indicator, and silt content and soil nutrients (available phosphorus and nitrogen) are the major rapid impact indicators. The results of this study may help to provide an improved understanding of the soil reconstruction mechanism and provide a scientific basis for appropriate artificial interventions to accelerate the recovery process.

The Effects of Mesquite (Prosopis juliflora) on Soils and Plant Communities in the Deserted Rangelands of Bahrain

The influence of mesquite trees (Prosopis juliflora (Swartz) D.C.) on the physicochemical properties of soils and annual understory plants was investigated in the deserted rangelands of Bahrain. Soil properties were measured in the understory and the uncanopied adjacent areas of mesquite trees. Likewise, the number of plant species was assessed in four 1 × 1 m randomly distributed quadrates in the understory and the uncanopied adjacent areas. The results showed that sand particles exceed 96% of soil composition. Soil bulk density at the 0–5 cm soil depth was significantly higher in the understory of trees compared to the uncanopied adjacent areas. However, moisture at a depth of 40–60 cm was significantly higher in the uncanopied adjacent areas. No differences in the pH, EC, K, Na, and Ca were found between understory and the uncanopied areas in all soil depths. Levels of N, P, Mg, and organic matter were significantly higher in the understory of trees compared to the uncanopied adjacent areas. Organic matter was twice the amount in the upper 20 cm of soil layers in the understory of mesquite trees. Species richness did not differ between the understory and the uncanopied areas. Nevertheless, the density of ephemerals in the understory of mesquite trees was higher than the uncanopied areas by 18%. The Shannon-Weaver index of diversity was higher in the uncanopied areas compared to the understory. The study concluded that the canopy effects of mesquite trees on soil vary with depth. Nonetheless, the influence of mesquite on flora could be beneficial for annual understory plants but subject to many operating factors, including density and cover of mesquite trees.

Nitrate leaching losses mitigated with intercropping of deep-rooted and shallow-rooted plants

Nitrate (NO3−) leaching has been recognized as a worldwide problem, and NO3− is a major pollutant in ground and surface waters. The gradual leaching of residual NO3− into soil layers below the root zone is the main way of nitrogen (N) loss in cropping systems. The interception of NO3− by subsurface roots is crucial for crops or vegetables to utilize N. However, few studies were focused on the mechanisms of NO3− leaching under intercropping of deep-rooted and shallow-rooted plants. In a greenhouse production system, we selected deep-rooted and shallow-rooted plants for single-season intercropping planting experiments (MP, monoculture of pepper; IPA, intercropping of pepper and alfalfa; IPM, intercropping of pepper and maize). Plants were grown in core drainage lysimeters for 4 months, and leachate was collected by soil solution samplers. The results revealed N transformations between monoculture and intercropping systems by comparing NO3− leaching, N use efficiency, and microbes involved in nitrification. NO3− accumulation mainly occurred in 25–40-cm soil layer, which was affected by root morphology. Compared with monoculture, intercropping reduced NO3− leaching, in particular, pepper/maize intercropping significantly reduced NO3− leaching losses. In deep soil layers, roots of alfalfa and maize were more developed than those of the other crops, which made this corresponding intercropping system more effective in absorbing N in the subsoil. N uptakes of pepper/alfalfa intercropping and pepper/maize intercropping were 19% and 28% higher than that from the monoculture, respectively. Ammonia oxidizing bacteria (AOB) were significantly stimulated with planting especial in the topsoil, while ammonia oxidizing archaea (AOA) decreased with planting along the soil profile. These results indicated that lush plant roots immobilized N from the deep soil and thus improved N use efficiency and reduced NO3− leaching in the deep-rooted and shallow-rooted intercropping system. Intercropping of shallow-rooted pepper with deep-rooted alfalfa can enhance root nutrient absorption in deep soil layers, increasing N use efficiency and thus reducing NO3− leaching. The nitrification process in the intercropped soil was mainly regulated by AOB.

ВПЛИВ АГРОХІМІЧНОГО НАВАНТАЖЕННЯ НА ЗАБЕЗПЕЧЕНІСТЬ РОСЛИН ЕЛЕМЕНТАМИ ЖИВЛЕННЯ ТА ВРОЖАЙНІСТЬ КУКУРУДЗИ В ЛІСОСТЕПУ

У статті представлено результати досліджень з питань оптимізації забезпеченості рослин кукурудзи основними елементами живлення за різного агрохімічного навантаження в умовах Лісостепу. Метою досліджень було встановлення впливу різних норм мінеральних добрив та побічної продукції попередника як добрива на забезпеченість рослин азотом, фосфором і калієм та врожайність кукурудзи. Дослідження проводили впродовж 2016-2019 рр. на темно-сірому опідзоленому крупнопилувато-легкосуглинковому ґрунті Лісостепу із застосуванням польового, хімічного, розрахунково-вагового та математико-статистичного методів. Виявлено, що тривале вирощування сільськогосподарських культур впродовж 30 років за різного агрохімічного навантаження у сівозміні на темно-сірому опідзоленому крупнопилувато-легкосуглинковому ґрунті Лісостепу зумовило створення різних агрохімічних фонів. За результатами ґрунтової та рослинної діагностики встановлено, що азот є лімітуючим елементом живлення за вирощування кукурудзи. У варіантах з унесенням підвищених (N180P120K180) та високих (N240P120K240) норм мінеральних добрив на фоні побічної продукції попередника (соломи пшениці озимої), де сформована найвища врожайність кукурудзи – 11,21-12,10 т/га, вміст рухомого фосфору в 0-20 см шарі ґрунту був дуже високим, рухомого калію – високим, азоту, що легко гідролізується – дуже низьким. У цих варіантах рослини кукурудзи за стадіями ВВСН 16, 19 і 65 накопичували оптимальну кількість азоту, а за вмістом фосфору та калію виявлено оптимальну та високу їх забезпеченість впродовж вегетації за внесення мінеральних добрив у нормах понад N60P45K60. За результатами кореляційного та регресійного аналізу підтверджено визначальну роль азоту та калію у формуванні продуктивності кукурудзи. Побудовано математичні моделі, що дають можливість прогнозувати рівень врожайності кукурудзи залежно від вмісту хімічних елементів у ґрунті та рослинах вже на ранніх стадіях розвитку ВВСН.

Рroductivity of soybean varieties in the inoculation of seeds by nodule and endophytic bacteria in the conditions of irrigation of South of Ukraine

Formulation of the problem. Soybeans as leguminous crops in the structure of Ukrainian cultivated area, has started to occupy one of the leading places in recent years due to the high content of protein - up to 38-42%, fat - up to 18-23% and carbohydrates - up to 25- 30% in its seeds. One of the most effective ways to increase the soybean seed productivity is the use of environmentally friendly inoculants created on the basis of nodules bacteria.
 Analysis of the recent researches and publications. According to the results of scientific researches, conducted in different natural and climatic zones of Ukraine, inoculation of soybean seeds with nodules bacteria significantly increases the symbiotic fixation of molecular nitrogen from air and, consequently the crop yield. It was established that endophytic bacteria along with the nodules bacteria are able to form a powerful symbiotic apparatus on the roots, synthesize biologically active metabolites characterized by antimicrobial action on phytopathogens, or are inducers of systemic plant resistance preventing them from the disease development.
 Tasks and methods of the research. The aim of the scientific research was to establish the effect of complex seed inoculation with the new endophytic bacteria strains along with the nodules bacteria on the formation of crops and the quality of soybean in different varieties of maturing under irrigation conditions in the south of Ukraine. The two-factor field experiment was carried out using the method of split plots, where the main plots (first-order plots, factor A) were the ultra-maturing (Diona) and mid-early (Aratta) soybean varieties. Second-order plots (subdivisions, factor B) were the options for pre-sowing seed treatment: 1 - Check 1 (without seed treatment); 2 - Check 2 (treatment of seeds with water); 3 - RizobinK (association of 3 strains of Bradyrhizobium japonicum UKM B-6018, UKM B-6023, UKM B-6035); 4 - RizobinK + Paenibacillus sp.1; 5 - RisobinK + Bacillus sp.4; 6 - RizobinK + Brevibacillus sp.5; 7 - RhizobinK + Pseudomonas brassicacearum 6; 8 - RizobinK + B. megaterium UKM B-5724.
 Presentation of the main material. The total evaporation and total water consumption of soybean varieties different in maturing were determined by a water balance method based on the moisture content of the soil at the beginning and at the end of growing season, use of water for crop formation in the interphase periods and during the whole growing season, taking into account rainfall and irrigation. Generally, the total water consumption of the ultra-maturing soybean variety Diona reached 5102 m3/ha from 0-70 cm of soil layer, and respectively, of the Aratta variety – 5832 m3/ha during the growing season. Pre-sowing inoculation of soybean seeds of different maturing varieties with nodules and endophytic bacteria contributed to the formation of more number of beans on plants and seeds in one bean. The maximum yield of the Diona variety that was obtained by pre-sowing inoculation of seeds with RizobinK + Bacillus sp.4 was 3.19 t/ha, and respectively, of the Aratta variety – 2.75 t/ha. The maximum protein content of 39.06-39.28% was in the seeds of Diona soybean in the variants where pre-sowing inoculation was carried out with the compositions RizobinK + Brevibacillus sp.5 and RizobinK + P. brassicacearum 6, which exceeded the parameters of Check 1 and Check 2 in 1.45-1.67 and 1.66-1.88 times, respectively. The high fat content was obtained in the seeds of the Diona variety by complex inoculation with the compositions RizobinK + Brevibacillus sp.5 and RizobinK + P.brassicacearum 6 (17.65 and 17.83%, respectively) and in the seeds of Aratta for the treatment with the complex inoculants RizobinK + Bacill. sp.4 and RizobinK + Brevibacillus sp.5 (18.62 and 18.84%) against 15.67–15.90% and 15.21–15.38% in the check variants of the respective varieties.
 Conclusions and prospects for further research. Pre-sowing inoculation of soybean seed varieties with nodules and endophytic bacteria, in comparison with the check variants, significantly influenced on the formation of the total number of beans on plants and seeds in one bean, which increased the yield of the Diona variety by 0.57–0.87 t/ha and the Aratta variety by 0.32–0.48 t/ha.

Dynamics of the availability of available moisture in soil by optimization of sowing time and density of statement of sunflower plants in the Right-Bank Steppe of Ukraine

Abstract. The article presents the results of scientific researches on the influence of sowing time and density of standing of sunflower plants on the dynamics of the content of available moisture in soil in the conditions of the Right-bank Steppe of Ukraine.
 One of the decisive factors for the achievement of high and sustainable crop yields in the conditions of unstable moistening of the Right-Bank Steppe of Ukraine is the accumulation and rational use of moisture, which is one of the most important unregulated factors limiting the yield.
 On average, during the years of research, the most available moisture in the 0-10 cm soil layer was in the first sowing period - when it was heated to a depth of seed 5 - 60C and was 25.0 mm. It was found that the moisture available to plants in the meter layer of soil at the time of sowing remained high and significantly influenced the dynamics of emergence of seedlings. On average, during the years of research, the most available moisture in the 0-100 cm soil layer was during the first sowing period - for warming it to a depth of seed 5 - 60C - 178.6 mm. In such conditions, quite favorable conditions of moistening of the sowing layer of soil are created in order to receive friendly and complete seedlings when sowing in the first - second decade of April. However, at the end of the third decade of April, there is a significant decrease in gross moisture reserves in the sowing and deeper layers of soil, which limits the productivity of crops.
 Of particular importance for sunflower plants is the content of available moisture in the 0 - 100 cm layer of soil after the formation of baskets. During this period, the sunflower intensively consumes the available moisture from the deeper layers of soil. Analyzing the results of the research, it should be noted that in most cases, a higher seed yield in sunflower hybrids was formed in those variants where the period from the formation of the basket to flowering occurred in June or the first decade of July, regardless of the year of fall medium long-term indicators.
 It was also found that the moisture available to plants in the meter layer of soil in the flowering phase was different during the years of research and varied in terms of sowing and depended on the density of plants. The highest moisture reserves available to the plants in the soil layer were 0-100 cm, in the crops of Forward hybrids, LG 56.32, LG 54.85, LG 55.82 were at planting densities of 60 thousand hectares, at the first sowing period - in the flowering phase - 127 mm. 
 The optimal sunflower sowing period for LG 55.82 and LG 54.85 hybrids in the Right Bank steppe is soil warming up to a depth of seed 5-60C, for Forward and LG 56.32 hybrids is warming up to, a depth of seed 9-100C, optimal density - 60 thousand on ha. Under these conditions, the LG 55.82 hybrid produced a yield of 3.85 t / ha, the LG hybrid 54.85 - 3.64 t / ha, the Forward - 3.09 t / ha, the LG hybrid 56.32 - 3.62 t / ha.
 Taking into account the annual variation of weather conditions of spring sowing, it should be differentiated with regard to water and heat regimes.
 

In-Situ Monitoring and Characteristic Analysis of Freezing-Thawing Cycles in a Deep Vadose Zone

Freeze-thaw cycles play a critical role in affecting ecosystem services in arid regions. Monitoring studies of soil temperature and moisture during a freeze-thaw process can generate data for research on the coupled movement of water, vapor, and heat during the freezing-thawing period which can, in turn, provide theoretical guidance for rational irrigation practices and ecological protection. In this study, the soil temperature and moisture changes in the deep vadose zone were observed by in-situ monitoring from November 2017 to March 2018 in the Mu Us Desert. The results showed that changes in soil temperatures and temperature gradients were largest in soil layers above the 100-cm depth, and variations decreased with soil depth. The relationship between soil temperature and unfrozen water content can be depicted well by both theoretical and empirical models. Due to gradients of the matric potential and temperature, soil water flowed from deeper soil layers towards the frozen soil, increasing the total water content at the freezing front. The vapor flux, which was affected mainly by temperature, showed diurnal variations in the shallow 20-cm soil layer, and its rate and variations decreased gradually with increasing soil depths. The freeze-thaw process can be divided into three stages: the initial freezing stage, the downward freezing stage, and the thawing stage. The upward vapor flux contributed to the formation of the frozen layer during the freezing process.

ROTAÇÃO DE CULTURAS E PREPARO DO SOLO SOBRE O BANCO DE SEMENTES DE PLANTAS DANINHAS EM TERRAS BAIXAS

No monocultivo de arroz, as espécies daninhas mais adaptadas a este sistema de produção aparecem em maior incidência na área. A rotação de culturas pode ser uma alternativa para auxiliar na redução do banco de sementes de plantas daninhas. Nesse sentido o objetivo do trabalho foi avaliar a dinâmica do banco de sementes de capim-arroz (Echinochloa spp.) e papuã (Urochloa plantaginea) em terras baixas, em combinações de rotação de culturas e do manejo de solo. Foram utilizadas as culturas de arroz, soja e sorgo, sob o manejo de preparo do solo convencional e sistema de semeadura direta, cultivado em faixas. Foi avaliado o banco de sementes de capim-arroz e papuã após dois anos de cultivo, na camada de 0-5 e 5-10 cm de profundidade. A densidade do banco de sementes de capimarroz e papuã foi superior no monocultivo de sorgo em relação ao cultivo de arroz. Não houve diferença do banco de sementes de plantas daninhas entre diferentes camadas de solo, exceto para o papuã no monocultivo de sorgo. O monocultivo de sorgo, sem aplicação de herbicidas em pós-emergência, em terras baixas incrementa o banco de sementes de capim-arroz e papuã.

Toward P-Band Passive Microwave Sensing of Soil Moisture

Currently, near-surface soil moisture at a global scale is being provided using National Aeronautics and Space Administration’s (NASA’s) Soil Moisture Active Passive (SMAP) and European Space Agency’s (ESA’s) Soil Moisture and Ocean Salinity (SMOS) satellites, both of which utilize L-band (1.4 GHz; 21 cm wavelength) passive microwave remote sensing techniques. However, a fundamental limitation of this technology is that the water content can only be measured for approximately the top 5-cm layer of soil moisture, and only over low-to-moderate vegetation covered areas in order to meet the 0.04 $\text{m}^{3}/\text{m}^{3}$ target accuracy, limiting its applicability. Consequently, a longer wavelength radiometer is being explored as a potential solution for measuring soil moisture in a deeper surface layer of soil and under denser vegetation. It is expected that P-band (wavelength of 40 cm and frequency of 750 MHz) could potentially provide soil moisture information for the top $\sim 10$ -cm layer of soil, being one-tenth to one-quarter of the wavelength. In addition, P-band is expected to have higher soil moisture retrieval accuracy due to its reduced sensitivity to vegetation water content and surface roughness. To demonstrate the potential of P-band passive microwave soil moisture remote sensing, a short-term airborne field experiment was conducted over a center pivot irrigated farm at Cressy in Tasmania, Australia, in January 2017. First results showing a comparison of airborne P-band brightness temperature observations against airborne L-band brightness temperature observations and ground soil moisture measurements are presented. The P-band brightness temperature was found to have a similar but stronger response to soil moisture compared to L-band.

Pasture degradation impact on soil carbon and nitrogen fractions of alpine meadow in a Tibetan permafrost region

Knowledge of the effects of pasture degradation on soil organic carbon (SOC) and nitrogen (N) fractions in permafrost soils on the Tibetan Plateau is limited. The aims of this study were (1) to evaluate the changes in SOC and N contents in density fractions under Kobresia pasture due to degradation and (2) to explore the contributions of the changes of SOC and N in density fractions to the changes of SOC and N in whole soil. The impact of Kobresia pasture degradation on SOC and N fractions was investigated in the permafrost region of the Tibetan Plateau. A continuously degraded pasture was identified and classified into three categories of vegetation cover according to their degrees of degradation (i.e., vegetation cover decline from 90% ± 6.6% to 70% ± 8.3% and 45% ± 8.7%). The SOC and N fractions were separated by using the density separation method. The Kobresia pasture degradation significantly decreases SOC and N contents and stocks in soils. The SOC and N contents in the whole soil were positively correlated with the SOC and N contents in the light and heavy fractions (p 0.05). When pasture degraded from vegetation covers 90% to 45%, SOC stock at 0–40-cm soil layer decreased by 28.7% and N stock decreased by 39.2% in the whole soil; 56.6% and 47.6%, respectively, in the light fractions and 14.3% and 40.6%, respectively, in the heavy fractions. The depletion rates of N were higher than those of SOC in the heavy fractions and whole soil. At all sites, more than 80% of the SOC and N stocks were protected in heavy fractions. These results indicate that a decoupling depletion of SOC and soil N appeared with the Kobresia pasture degradation in the permafrost region of the Tibetan Plateau. The Kobresia pasture degradation affects the SOC and N fractions differently and thus regulates soil carbon and N cycling in the permafrost soils on the Tibetan Plateau.

A 10-Yr Global Land Surface Reanalysis Interim Dataset (CRA-Interim/Land): Implementation and Preliminary Evaluation

A land surface reanalysis dataset covering the most recent decades is able to provide temporally consistent initial conditions for weather and climate models, and thus is crucial to verifying/improving numerical weather/climate forecasts/predictions. In this paper, we report the development of a 10-yr China Meteorological Administration (CMA) global Land surface ReAnalysis Interim dataset (CRA-Interim/Land; 2007–2016, 6-h intervals, approximately 34-km horizontal resolution). The dataset was produced and evaluated by using the Global Land Data Assimilation System (GLDAS) and NCEP Climate Forecast System Reanalysis (CFSR) global land surface reanalysis datasets, as well as in situ observations in China. The results show that the global spatial patterns and monthly variations of the CRA-Interim/Land, GLDAS, and CFSR climatology are highly consistent, while the soil moisture and temperature values of the CRA-Interim/Land dataset are in between those of the GLDAS and CFSR datasets. Compared with ground observations in China, CRA-Interim/Land soil moisture is comparable to or better than that of GLDAS and CFSR datasets for the 0–10-cm soil layer and has higher correlations and slightly lower root mean square errors (RMSE) for the 10–40-cm soil layer. However, CRA-Interim/Land shows negative biases in 10–40-cm soil moisture in Northeast China and north of central China. For ground temperature and the soil temperature in different layers, CRA-Interim/Land behaves better than the CFSR, especially in East and central China. CRA-Interim/Land has added value over the land components of CRA-Interim due to the introduction of global precipitation observations and improved soil/vegetation parameters. Therefore, this dataset is potentially a critical supplement to the CRA-Interim. Further evaluation of the CRA-Interim/Land, assimilation of near-surface atmospheric forcing variables, and extension of the current dataset to 40 yr (1979–2018) are in progress.

Потенційна забур’яненість ґрунту залежно від його обробітку за вирощування гречки посівної в Прикарпатті України

An actual problem in modern agriculture is the development of weed control measures in crops. The number of weeds, in turn, depends on the number of viable seeds in the soil. Therefore, the purpose of the study was to determine the effect of different variants of primary and pre-sowing tillage on the content and distribution of physically complete weed seeds in the 0–30 cm layer of soil, as well as its germination and productivity of sowing buckwheat. The research was conducted in the conditions of the Carpathian State Agricultural Research Station of NAAS and the Laboratory of the Department of Agriculture and Herbology of NULES of Ukraine during 2015–2017. According to the results of both experiments, variants of chiseling by 20–22 cm, disking by 10–12 cm and 6–8 cm led to the placement of the bulk of weed seeds – 43–56 % in the upper 0–10 cm soil layer, which subsequently allows you to choose the optimal system of pre-sowing tillage. These variants of basic tillage in combination with the second variant of pre-sowing provided the highest level of germination of weed seeds (+ 250–288 % to control). The highest crop yield (3.61 t/ha) in both experiments was recorded for the combination chiseling of soil on 20–22 cm and pre-sowing, which included of early spring harrowing, harrowing with heavy tooth-boring harrows (as weed germination) and pre-sowing cultivation to the depth of sowing.

Snow pollution by nitrogen-containing substances as a consequence of rocket launches from the Baikonur Cosmodrome

In this paper, we assessed snow pollution by nitrogen-containing substances including rocket propellants – UDMH (unsymmetrical dimethylhydrazine, (СН3)2NNH2) and NT (nitrogen tetroxide, N2O4) – and their transformation products (NDMA (nitrosodimethylamine, (CH3)2NNO), NO3−, NO2− and NH4+) within the falling regions (FRs) of the first and second stages of Proton-M rockets launched from the Baikonur Cosmodrome. At the first stage FR in Central Kazakhstan, snow with a pH range from 1.7 to 9.0 was contaminated by N-containing substances (maximal value in g/L): UDMH – 0.27, NDMA – 0.04, NO3− – 19, NH4+ – 0.04 and NO2− – 0.13. The first stage landing resulted in snow contamination by soil dust particles and N-containing substances at a rate of 13 g/m2 and 82 mg/m2/day, respectively. The maximal permissible addition (MPA) for UDMH, NDMA and NO3− to the 0–5 cm layer of soil was estimated at 0.06, 0.006 and 70.2 mg/m2, respectively. At the second stage FR in the NE Altai, substances released by space transportation were absent and the concentration of NO3− and NH4+ corresponded to the natural background level. The index of contamination (IC) was used for characterizing the degree of snow contamination by N-containing substances. A simulation model was developed for analysing the dependence of snow contamination by rocket propellant components on the weather parameters.

The Sensitivity of North American Terrestrial Carbon Fluxes to Spatial and Temporal Variation in Soil Moisture: An Analysis Using Radar‐Derived Estimates of Root‐Zone Soil Moisture

AbstractThis study examines the impact of variation in root‐zone soil moisture (RZSM), a key component of the Earth's hydrologic cycle and climate system, on regional carbon fluxes across seven North American ecosystems. P‐band synthetic aperture radar‐derived RZSM estimates were incorporated into the ecosystem demography (ED2) terrestrial biosphere model through a model‐data blending approach. Analysis shows that the model qualitatively captures inter‐daily and seasonal variability of observed RZSM at seven flux tower sites (r = 0.59 ± 0.26 and r = 0.70 ± 0.22 for 0–10 and 10–40 cm of soil layers, respectively; P < 0.001). Incorporating the remotely sensed RSZM estimates increases the accuracy (root‐mean‐square deviations decrease from 0.10 ± 0.07 and 0.09 ± 0.06 m3·m−3 to 0.08 ± 0.05 and 0.07 ± 0.03 m3 ·m−3 for 0–10 and 10–40 cm of soil layers, respectively) of the model's RZSM predictions. The regional carbon fluxes predicted by the native and RZSM‐constrained model were used to quantify sensitivities of gross primary productivity, autotrophic respiration (Ra), heterotrophic respiration (Rh), and net ecosystem exchange to variation in RZSM. Gross primary productivity exhibited the largest sensitivity (6.6 ± 10.7 kg·cm−2·year·θ−1) followed by Ra (2.9 ± 7.3 kg·cm−2·year−1·θ−1), Rh (2.6 ± 3.1 kg·cm−2·year−1·θ−1), and net ecosystem exchange (−1.7 ± 7.8 kg·cm−2·year−1·θ−1). Analysis shows that these carbon flux sensitivities varied considerably across regions, reflecting influences of canopy structure, soil properties, and the ecophysiological properties of different plant functional types. This study highlights (1) the importance of improved terrestrial biosphere model predictions of RZSM to improve predictions of terrestrial carbon fluxes, (2) a need for improved pedotransfer functions, and (3) improved understanding of how soil characteristics, climate, and vegetation composition interact to govern the responses of different ecosystems to changing hydrological conditions.