The humus status of brown forest soils and its changes upon intensive tea growing in the subtropical zone of Russia

Changes in the humus status of acid brown forest soils used for tea growing have been studied in a long-term stationary experiment after 20 years of the application of mineral fertilizers in increasing doses. It is shown that long-term tea growing has resulted in a reliable increase in the humus content within the upper cultivated horizon (Ap, 0–40 cm) at the expense of the nonhydrolyzable fraction of humus (humin) and the first fractions of humic and fulvic acids. The fractional composition of humus has changed against the background of a stable fulvate type of humus (Cha/Cfa < 0.5). The portion of the first fraction of humic and fulvic acids in the total amount of humus has increased, as well as the portion of the first fraction of humic acids in the total amount of humic acids. These changes are due to the enhanced humification of plant residues with a parallel decrease in the contents of the second (Ca-bound) and third (bound with clay and stable sesquioxides) fractions of humic substances.     

Changes in the content and composition of humus in the sandy loamy soddy-podzolic soil in a long-term liming experiment

The effect of liming on organic matter in sandy loamy soddy-podzolic soil was studied. The study was performed on samples taken from the 50-year-long experiment established by Prof. Kornilov in 1957. It was shown that liming had almost no effect on the total humus content in the soil. The humus composition was studied using two fractionation methods of the humus substances by the Ponomareva-Plotnikova procedure. The regrouping of the humus fractions occurred due to the changes in the mobility of soil mineral components, which involved a regular increase in the content of the Ca-bound fraction of humic acids (HA-2) at the expense of the HA-1 fraction bound to the mobile forms of R₂O₃ reliable at the lime rates equivalent to the total acidity and higher. The levels of the stabilization of the different HA fractions were considered, as well as the stability of the changes in the humus composition during 50 years.     

Changes in the content and quality of humus in leached chernozems of the Trans-Ural forest-steppe zone under the impact of their agricultural use

The results of long-term studies of changes in the content and fractional-group composition of humus in leached chernozems (Luvic Voronic Chernozems, WRB 2006) of the Trans-Ural forest-steppe since the beginning of their plowing are considered. These soils are characterized by the high humus pool (up to 500 t/ha in the virgin state and up to 430 t/ha in the plowed state) and the high degree of the organic matter humification. Humus is of the fulvate–humate type in the upper 30 cm and of the humate–fulvate type in the deeper layers. From 1968 to 2006, the total pool of humus in the 1-m-deep soil layer of the plowed chernozems decreased by 8.5% in comparison with the initial virgin soils. The rate of dehumification reached 1.0–1.4 t/ha per year. The long-term plowing of leached chernozems also led to a smaller content of nitrogen in the organic matter (the C/N ratio increased from 11.5 to 13.6). The relative content of free humic acids (HA-1) and humic acids bound to clay minerals (HA-3) increased, whereas the content of calcium humates (HA-2) decreased. The composition of fulvic acids in the plow horizon was characterized by the rise in the content of aggressive (FA-1a) and mobile (FA-1) fractions, while the amount of fulvates bound to calcium (FA-2) decreased.     

Humic substances in agro-stratozems of Leningrad oblast

Chemical properties and some parameters of the humus status of agro-stratozems developed in Leningrad oblast from different parent materials and with different histories of agricultural use were studied. The stability of the elemental composition of humus in the studied soils was found. The group and fractional composition of humus was more sensitive to agricultural impacts. In response to the application of manure, lime, and mineral fertilizers, humate-fulvate humus changed into fulvate-humate humus and the content of the agronomically most valuable HA-2 fraction increased, in some cases, to predominance. Exclusion from land use for 15 years decreased the humus content and changed its composition; it became more similar to that in zonal soddy-podzolic soils, which are the natural analogues of the agro-stratozems studied.     

Transformation of the humus composition in light-textured soddy-podzolic soils as affected by increasing lime doses and in the postagrogenic period

The fractional-group composition of humus in a loamy-sandy soddy-podzolic soil limed using different doses of chalk was studied. The transformation of the humus composition is related to the dose of the lime fertilizer and terminates after the complete dissolution of the ameliorant applied. The full dissolution of the chalk applied in high doses ends within three years after the liming. The humus composition of the cultivated sandy soddy-podzolic soil was investigated at different stages of the postagrogenic successions. The changes in the humus composition due to the neutralization of the soil’s acidity and cultivation are rather stable in time. Sixty years after the termination of the anthropogenic impact, in the humus composition of the sandy soddy-podzolic soil, humic acids bound with calcium were found. One hundred years after the end of the soil cultivation, its humus composition approaches the humus composition of the virgin soil. However, no complete restoration of the humus composition has occurred. Data on the optical density of the humic acids are presented.     

稻草不同途径还田对土壤结构及有机质特征的影响

通过3年的田间定位试验,系统的研究了稻草不同途径还田对稻田土壤容重、孔隙度、团聚体、有机碳总量、腐殖质组成及腐殖质结合形态的影响。结果表明,与无肥(CK)及纯施化肥(NPK)对照相比,稻草直接深埋还田(NPK+S)及利用后的菌渣、牛粪、沼渣深埋还田(NPK+FD、NPK+CD、NPK+BD)均能一定程度的降低土壤容重、增加孔隙度、增加>0.25 mm水稳性团聚体的数量和提高土壤团聚体的稳定性,有利于形成和保持良好的土壤结构;同时能提高土壤腐殖质中胡敏酸含量和HA/FA比值,增加松结态腐殖质含量和提高松/紧腐殖质比值,能一定程度的改善土壤腐殖质的组成、性质及结合形态,提高腐殖质品质,不过这4个处理间的差异不明显。稻草焚烧还田(NPK+S′)在以上方面效果均不显著,且带来严重的大气污染,并不可取。     

不同种类有机肥施用对黑土团聚体有机碳及腐殖质组成的影响

以吉林省农业科学院黑土有机培肥定位试验基地为平台,研究了不同种类有机肥(堆腐肥、鸡粪、牛粪和猪粪)施用对土壤及不同粒级团聚体中有机碳和腐殖质组成的影响。结果表明:与不施肥(CK)和单施化肥(NPK)相比,有机肥配施化肥显著(P0.05)增加了土壤有机碳、胡敏酸碳(HAC)和胡敏素碳(HUC)含量;同时,有机肥配施化肥也增加了不同粒级团聚体中有机碳和腐殖质碳含量,其中施用堆腐肥显著增加了各粒级团聚体中有机碳、HAC和HUC含量。不同种类有机肥相比,施用堆腐肥处理的土壤有机碳、HAC和HUC含量均高于其他有机肥处理,并与牛粪处理之间差异显著;施用堆腐肥和牛粪后,0.25mm粒级团聚体有机碳含量高于其他有机肥处理,且2~0.25mm粒级团聚体有机碳含量显著高于鸡粪处理;从不同粒级团聚体中腐殖质组分的分布来看,施用堆腐肥后,2~0.25mm粒级团聚体中HAC和HUC含量显著高于猪粪处理,而0.25~0.053,0.053mm粒级团聚体中HAC含量显著低于鸡粪处理。上述结果说明,有机肥配施化肥提高了土壤团聚体中有机碳和腐殖质碳含量,但不同有机肥的效应不同。     

Effect of humic preparation on winter wheat productivity and rhizosphere microbial community under herbicide-induced stress

Purpose

The aim of the present work was to study the effect of humic preparation on the yielding capacity of winter wheat, the dynamics of mineral nutrients in the rhizosphere, and the activity of rhizosphere microbial community, as well as the protective properties of humate treatment under the stress caused by the application of a sulfonylurea herbicide.

Materials and methods

The humic preparation BIO-Don is prepared from vermicompost by alkaline extraction. The effect of humic preparation was estimated in a field experiment. The contents of the mobile ammonium and nitrate, exchangeable potassium, phosphorus, and humus were determined. Sampling and nutrient determination were performed in the tillering, booting, and grain maturing stages. Production experiments on the study of the combined effect of the humic preparation and the sunfonylurea pesticide Granstar Pro were performed in 2015 and 2017. The dynamics of mobile phosphorus in soil was studied. The abundance of culturable bacteria in the rhizosphere and bacterial species with different ecological strategies was determined. The dominant bacterial species were identified by MALDI-TOF mass spectrometry.

Results and discussion

The results of a small-plot experiment showed that at the tillering stage, the use of humic preparation has led to significantly higher supply of soil with mobile phosphorus. The winter wheat yield was 32.0 dt/ha in the control and 39.2 dt/ha with humic preparation or 22.5% gain in yield. The results of production experiment show that the application of sulfonylurea herbicide induced a chemical stress on winter wheat plants, but the use of humic preparation reduced this effect and increased the availability of phosphorus compounds. The treatment of plants with pesticides caused the general decrease in abundance of bacteria in the rhizosphere. The effect on quickly growing bacteria is more pronounced, while slowly growing bacteria and fungi are more resistant to this impact.

Conclusions

The application of humic preparation to winter wheat plantations allows to decrease the toxic effect of sulfonylurea herbicide, improve the supply of soil with mineral nutrients, and increase the crop yield. The favorable effects of humic preparation can be related to the active regulation of phosphorus mobilization by plants through the mechanism of root exudates due to the activation of root microbiota.

     

Agronomic Evaluation of Liquid Humus Derived From Earthworm Humic Substances

Carbon (C), commonly expressed as organic matter (OM), is of vital importance in soil productivity. Liquid humus is an alkaline suspension containing humic and fulvic acids, which can facilitate C addition to the soil through the irrigation system to increase OM and soil fertility levels. Two liquid humus products were formulated from earthworm humic substances and the effects of these and other commercial products derived from leonardite, on soil and ryegrass were evaluated in a pot experiment under greenhouse conditions. On average, C application, regardless of source, increased the aerial and root dry matter, plant greenness, nitrogen (N), phosphorus (P), and potassium (K) uptake, and nutrient use efficiency. Carbon effects on plant production were larger when added over fertilized plants. Residual soil N was lowered by the application of liquid humus. No significant effect of C rate was observed on soil pH or electrical conductivity (EC) at the end of the experiment. Optimal C rates found in this study were higher than the recommended commercial ones. No major differences among earthworm liquid humus and leonardite-based products were observed; therefore the former would constitute a more sustainable alternative for organic matter additions as they are made from a renewable resource.     

Studies on the humus forms of forest soils

The results of humus composition analysis of each fraction separated physically from each horizon of the five forest soils used in the last paper (3) were presented.

Regular changes in humus composition were observed with the gradation of horizons and With the decrease in particle size. Most of the humic acids from plant residual fractions belonged to the Rp type; hurnic acids from the L layers showed a tannin-like character which disappeared with the progress of decomposition, and humic acids from the smaller particle fractions of the layers contained a Pg fraction.

As for humic acids from the A horizon, they all belonged to the P or B type and contained a Pg fraction. In addition, it was concluded that the humification process in the mineral layer Was clearly different from that in the organic layer.     

Effect of continuous compost application on humus composition and nitrogen fertility of soils in a field subjected to double cropping

We investigated the effect of continuous compost application on humus composition and N fertility of soils in a field subjected to double cropping (paddy rice and barley) for 25 years. Soil samples were collected from three different plots: (a) No-NF, fertilizer containing P and K but no N; (b) F, fertilizer containing N, P, and K; and (c) F+C, fertilizer plus compost. The amounts of total humus, extracted humus, and humic and fulvic acids increased in the order No-NF<F≪F+C. The amounts of humic and fulvic acids were 2.7 and 1.7 times larger in the F+C plot than in the F plot, respectively. The degree of humification of the humic acids decreased in the order No-NF<F<F+C. The absorption curves and ¹³C-NMR spectra (TOSS method) of the humic acids indicated the presence of lignin-like structure, and its degree was the strongest in the F+C plot. The ¹³C-NMR spectra showed distinct differences in the distribution of carbon species between humic and fulvic acids. In humic acids, the content of aromatic-C, ranging from 37 to 44%, was the highest among carbon species. In fulvic acids, the content of O-alkyl-C, ranging from 45 to 51%, was the highest. The amounts of phosphate buffer-extractable N (PEON) and total N (TN) increased in the order No-NF<F<F+C. The amounts of PEON and TN were 1.2 and 1.7 times larger in the F+C plot than in the F plot, respectively. Present and previous findings indicated that continuous compost application could improve various properties of soils in a field subjected to long-term double cropping.     

Combination reaction between humic acid and calcium ions

In the previous paper (1), liming an acid humus volcanic ash soil resulted in the formation of humic acids combined with calcium, but had no significant effect on acid brown forest soils containing humic acids of a lower degree of humification. Subsequently, the authors examined the humus composition of the soils treated with calcium acetate, and conducted some experiments on the combination reaction between humic acid and calcium ions. The results obtained are presented in this paper.     

化肥配施不同剂量有机肥对黑土团聚体中有机碳与腐殖酸分布的影响

【目的】 团聚体的形成为土壤有机碳的稳定提供了重要的物理保护,施用有机肥影响着土壤团聚体的形成,量化有机肥施用剂量与团聚体有机碳稳定性之间的关系对于阐明农田土壤有机碳的固碳机制具有重要意义。 【方法】 以黑龙江省海伦市国家野外科学观测研究站为平台,选择连续10年进行化肥配施不同剂量有机肥处理[0、7.5、15、22.5 t/(hm2·a)]的黑土为研究对象,将团聚体分组与腐殖酸提取相结合,分析了不同粒径团聚体中有机碳和腐殖酸的含量与光学特性。 【结果】 1)与单施化肥相比,化肥配施有机肥增加了大团聚体( > 0.25 mm)的分配比例与团聚体的平均重量直径,二者均随着有机肥剂量的增加而逐渐升高,回归拟合分析表明,团聚体的平均重量直径与有机肥剂量之间呈现显著的正相关关系(P=0.03)。2) 2~0.25 mm团聚体是黑土有机碳的主要贮存场所,约占有机碳总量的64.8%~68.8%,大团聚体中有机碳的含量与储量均随着有机肥剂量的增加而逐渐升高, < 0.053 mm团聚体中有机碳含量与储量则维持在较稳定的水平。3)各粒级团聚体中腐殖酸碳含量以0.25~0.053 mm团聚体最高,各粒级团聚体中腐殖酸碳占有机碳百分比之间的差异不显著。化肥配施有机肥提高了各粒级团聚体中腐殖酸碳的含量,使团聚体对有机碳的固持能力增加,且各粒级团聚体中腐殖酸碳的含量随着有机肥剂量的增加逐渐升高。4)化肥配施有机肥增加了各粒级团聚体中腐殖酸的E4/E6比值,表明其分子结构简单化,且以 > 2 mm和0.25~0.053 mm团聚体中腐殖酸E4/E6比值的增加最显著。 【结论】 在黑土中,长期连续进行化肥配施有机肥,促进了团聚体的形成,改善了耕层土壤结构,增加了团聚体中有机碳的积累与固持能力,并使各粒级团聚体中腐殖酸的结构“年轻化”,这种促进作用在高剂量有机肥施用下更为显著。实际生产中,在短期内可通过适当提高有机肥的施用量以提高黑土肥力及其固碳能力。     

The humus state of the soils of locally hydromorphic landscapes in the lower reaches of the don river

The humus state of rainfed chernozems affected by local waterlogging was studied. The total humus content in the hydromorphic chernozems increases, as well as the content of fulvic acids, whereas the content of nonhydrolyzable residue (humin) decreases. A significant increase in the portions of the third fractions of humic and fulvic acids is observed. The role of the fine silt and clay fractions in the binding of humic substances increases in the lower horizons of locally hydromorphic soils. The increase in the content of fulvic acids (fulvatization) is mainly due to their predominance in the clay fraction. The latter is specified by the significant narrowing of the C_ha-to-C_fa ratio, the lower content of the nonhydrolyzable residue, and the increased content of the clay-bound (3rd fraction) fulvic and humic acids. The composition of the humus in the fine silt fraction of the studied soils is characterized by an increased amount of humic acids of the second fraction with a decrease in the relative content of fulvic acids.     

有机肥料氮替代部分无机氮对水稻产量的影响及替代率研究

通过田间试验,研究了不同氮用量下有机肥料氮替代部分无机氮对水稻产量、氮肥利用率和土壤矿质态氮的影响,试图探索出有机肥料氮替代无机氮的最适替代率,并对有机肥与化肥配施的经济效益进行评价。结果表明:1）有机肥与化肥配施处理（8381~9810 kg/hm2）能获得与单施化肥处理（8381~10124 kg/hm2）更高或持平的产量;2）与单施化肥相比,氮用量在N 240 kg/hm2内,有机肥料氮替代无机肥料氮的最适替代率为10%~20%（相当于施用1500~3000 kg/hm2商品有机肥）,此时水稻产量、氮肥利用率和经济效益都达到最佳水平;3）与单施化肥相比,氮用量在N 240 kg/hm2以内并且有机肥料氮占氮总量的10%~20%时可以获得较为平稳的氮素供应过程,改善了土壤供氮能力。上述结果可为研制有机无机复合肥提供理论基础。     

Systems of solutions,minerals, and humic substances in soils

The equilibrium composition of solutions, minerals, and humic substances of the humus-clay plasma from the humus horizon of a leached chernozem was calculated using the method of computerized physicochemical simulation based on Gibbs’ principle of minimum free energy in the equilibrium state of the system. It was shown that the plasma from the humus horizons of chernozems and soddy-deeply podzolic soil mainly consists of oxides, hydroxides, humic substances, kaolinite, and 2: 1 illite-smectite minerals. The stoichiometry of the humic substances corresponds to calcium-saturated humus acids with appreciable contents of iron and aluminum. The crystallochemical composition of the 2: 1 layered minerals classifies them among ferruginated mixed-layered illite-montmorillonites. Simulation at an increased concentration of carbon dioxide indicated the degradation of the humus-clay plasma in a leached chernozem under extensive soil use, which can be restored by application of potassium at rates 1-to ?1.5-fold its removal.     

Changes in the Content,Composition, and Properties of Humic Substances in Particle-Size Fractions of Soddy-Podzolic Soils under the Impact of Long-Term Drainage

Specific features of the transformation of humic substances in particle-size fractions of drained soddy-podzolic soils were studied on a field (12 ha) of the Experimental and Educational Center of Lomonosov Moscow State University in Moscow oblast. The field had a clearly pronounced microtopography. Surface-gleyed soddy-podzolic soils (Albic Stagnic Glossic Retisols (Loamic, Aric, Ochric)) of microdepressions with excessive surface moistening and nongleyed soddy-podzolic soils (Albic Glossic Retisols (Loamic, Aric, Ochric)) of elevated positions were examined. These soils were studied before the field drainage and during 25 years after drainage works in the periods differing in conditions of humification and with due account for not only drainage works but also other factors, such as topography and agrotechnology and their joint action. The specificity of transformation of humic substances in the soils and their particle-size fractions was analyzed in the basis of data on the organic carbon content, group and fractional composition of humus, the intensity of individual stages of humification (the neoformation of humic acids and the formation of humates), and the optical density of the fractions of humic acids. The results of the study of these properties in the fine soil fractions (<50 μm) made it possible to assess the response of the clay (<1 μm) and silt (1–5, 5–10, 10–50 μm) fractions to changes in the ecological situation and the role of separate particle-size fractions in the degradation of humus under adverse impacts. Overall, a clear tendency toward worsening of the humus quality was observed in both soils during the 25-year-long period, which is related to the long-term (20 years) agricultural use of the reclaimed field without application of agrochemicals. The features of humus degradation were mainly manifested in the finest (<10 μm) fractions with a general decrease in the humus content, slowing down of the formation of humic acids and humates, and considerable loss of humic acids, including their agronomically valuable fractions HA1 and HA2. The degradation of humus quality in the clay fraction was largely due to the impact of the reclamation (drainage) factor; the degradation of humus quality in the fine and medium silt fractions was mainly due to the negative changes in the agricultural background. Among negative consequences of the worsening humus quality, the lowering of soil fertility, ecological sustainability, and productivity of agrocenoses should be noted.     

长期施肥对小麦-玉米作物系统土壤腐殖质组分碳和氮的影响

通过对华北平原小麦–玉米轮作农田生态系统18年田间施肥试验,研究了长期不同施肥处理对耕层（0—20 cm）土壤腐殖质及活性腐殖质组分碳和氮的影响。试验设化肥NPK不同组合（NPK、NP、NK、PK）,全部施用有机肥（OM）,一半有机肥+化肥NPK（1/2OMN）及不施肥（CK）共7个处理。结果表明,各施肥处理均能在不同程度上增加土壤腐殖质（胡敏酸、富里酸和胡敏素）及活性腐殖质（活性胡敏酸和活性富里酸）组分碳和氮含量,提高可浸提腐殖质（胡敏酸和富里酸）及活性腐殖质组分碳和氮分配比例;但施肥对土壤活性腐殖质组分碳和氮含量的增加率均分别高于腐殖质组分碳和氮。各处理土壤腐殖质及活性腐殖质组分碳和氮含量均为OM处理最高,且有机肥与化肥NPK配施高于单施化肥各处理;而化肥处理中NPK均衡施用效果最好。说明施用有机肥、有机肥与化肥NPK配施及化肥NPK均衡施用是增加土壤腐殖质及活性腐殖质组分碳和氮的关键;活性腐殖质组分碳和氮较腐殖质组分碳和氮对施肥措施的响应更灵敏。     

长期施肥条件下土壤养分的动态和平衡——Ⅱ.对土壤氮的有效性和腐殖质氮组成的影响

长期施用有机肥、化肥或二者配合施用均增加了土壤全氮、碱解氮、酸解氮和植物吸收氮量,提高了土壤氮的有效性,其后效可保持至第3年;土壤腐殖质的胡敏酸氮减少,富里酸氮增加。富里酸氮易被6mol/L HCl水解,水解氮占71.4％～74.2％;胡敏酸氮比较稳定,水解氮占40％～45％。在水解氮中,氨基氮的比例为2/3～3/4,铵态氮为1/4～1/3。胡敏酸中非水解氦的主要成分是杂环化合物氮(37.5％～52.5％),其次是苯系化合物氮(31％～35.2％)和非苯系化合物氮(10.6％～26.7％)。长期施用有机肥和化肥,杂环氮比例减少,苯系和非苯系化合物氮比例增加。胡敏酸表层氮占1/3左右,核心氮占2/3左右,施用有机肥和化肥,胡敏酸表层氮增加,核心氮降低。     

长期施肥条件下土壤养分的动态和平衡——Ⅱ.对土壤氮的有效性和腐殖质氮组成的影响

长期施用有机肥、化肥或二者配合施用均增加了土壤全氮、碱解氮、酸解氮和植物吸收氮量,提高了土壤氮的有效性,其后效可保持至第3年;土壤腐殖质的胡敏酸氮减少,富里酸氮增加。富里酸氮易被6mol/L HCl水解,水解氮占71.4％～74.2％;胡敏酸氮比较稳定,水解氮占40％～45％。在水解氮中,氨基氮的比例为2/3～3/4,铵态氮为1/4～1/3。胡敏酸中非水解氦的主要成分是杂环化合物氮(37.5％～52.5％),其次是苯系化合物氮(31％～35.2％)和非苯系化合物氮(10.6％～26.7％)。长期施用有机肥和化肥,杂环氮比例减少,苯系和非苯系化合物氮比例增加。胡敏酸表层氮占1/3左右,核心氮占2/3左右,施用有机肥和化肥,胡敏酸表层氮增加,核心氮降低。