Carbon budget in agroecosystems on gray forest soils in the Lake Baikal region

The carbon budget in agroecosystems with spring wheat was studied in long-term (1997–2004) field experiments on gray forest soils in the forest-steppe of the Lake Baikal region, including soils polluted with the fluorides emitted by an aluminum plant. Pollution was revealed to increase the deficit in the carbon budget due to the more intense mineralization of organic matter and CO₂ emission from the soils. Raising of the crops’ productivity upon permanent application of fertilizers may provide maintenance of a positive carbon budget.     

Carbon budget in arable gray forest soils under different land use conditions

The effect of different land-use practices on the carbon budget in old arable gray forest soils of Russia was studied in field experiments. A short-term (for 6–7 years) cessation of mineral fertilization had no negative effects on the carbon budget in the agrocenoses studied. Only the combination of zero fertilization with the return to monoculture and the introduction of black fallows created a negative budget of humus in the soil. The regrassing of the eroded arable soil for 24 years increased the humus reserve in the 0- to 60-cm layer by a factor of 1.6–1.7. The average annual accumulation of carbon and nitrogen after the restoration of the perennial vegetation was 106–128 g C/m² and 11–16 g N/m², respectively.     

Phosphorus in agroecosystems on gray forest soils in the opolie regions of Central Russia

Long-term stationary field experiments revealed a poor supply of gray forest soils with available phosphorus, which provides no more than half the amount necessary for optimum nutrition of plants. It was found that agricultural crops with different capacities to assimilate phosphates from the soil and fertilizers have strong requirements for phosphorus fertilizers and abruptly increase their utilization in the production process with increasing level of nitrogen nutrition. Crops with the optimum level of nitrogen nutrition uptake a double amount of phosphorus compared to crops depleted in nitrogen. Clover and barley have an increased capacity to mobilize soil phosphates from the lower horizons at an extremely low content of available forms of them in the plow layer. Winter wheat and corn are characterized by an active uptake of phosphorus applied with fertilizer and its efficient utilization in the production process if the nitrogen supply is not a limiting factor. The level of phosphorus nutrition of subsequent rotation crops increases due to the enrichment of the root-inhabited soil layer with phosphorus from clover root and harvest residues. Based on the data about the unacceptably abrupt decrease in the application of mineral fertilizers in Russian agriculture (90% of fertilizers are exported now), it is shown that the export of fertilizers should be limited at the state level, because chemicals, and primarily phosphorus fertilizers, should be considered strategic resources for internal use only.     

Iron in hydromorphic gray forest soils

The amorphous iron content in the upper soil horizons, the profile distribution of iron oxides and hydroxides, and the Schwertmann (Fe_o/Fe_d) ratio can be used as diagnostic criteria for the degree of gleyization in the classification of hydromorphic soils. Drainage removes chemical elements, e.g., nonsilicate Fe, from soils.     

Short- and long-term effects of nitrogen fertilization on methane oxidation in three Swedish forest soils

 Under normal conditions, CH₄, one of the most important greenhouse gases, is subject to biological oxidation in forest soils. However, this process can be negatively affected by N amendment. The reported experiment was conducted in order to study the short- and long-term effects of N amendment on CH₄ oxidation in pine (Pinus sylvestris L.) forest soils. Soil samples were taken from three experimental sites, two of which had been amended with N once, over 20 years earlier, while the third had been amended 3 weeks earlier. The soil samples were incubated fresh at 15  °C at ambient CH₄ concentrations (ca. 1.8 ppmv CH₄). The variation in CH₄-turnover rates was high within the treatments: CH₄ was produced [up to 22.6 pmol CH₄ g dry wt. soil^–1 h^–1] in samples from the recently amended site, whereas it was consumed at high rates (up to 431 pmol CH₄ g dry wt. soil^–1 h^–1) in samples from the plot that had received the highest N amendment 27 years before sampling. Although no significant differences were found between N treatments, in the oldest plots there was a correlation between consumption of atmospheric CH₄ and the total C content at a depth of 7.5–15 cm in the mineral soil (r ²=0.74). This indicates that in the long-term, increased C retention in forest soils following N amendment could lead to increased CH₄ oxidation. Received: 3 September 1997     

长期施肥下黑土有机肥替代率变化特征

探索长期施肥下黑土有机肥替代率与土壤肥力提升的关系,可为农田土壤培肥和有机替代提供理论依据。对吉林省公主岭黑土32年的长期肥力试验定位观测数据进行系统分析,基于作物氮素吸收量和土壤氮素供需方程探讨高产条件下施用不同量有机肥的黑土有机肥替代率的变化特征。研究表明,作物产量随着有机肥施用年限增加逐渐提高,32年的持续施肥,施用有机肥的作物产量趋同甚至高于NPK化肥处理的作物产量。基于作物氮素吸收量,高产条件下有机肥替代率与施肥年限呈极显著线性正相关(P0.01),高量有机肥处理(M2)的有机肥替代率高于常量有机肥处理(M1);且有机肥施用29年后,高量有机肥处理(M2)的有机肥替代率达到100%,并保持稳定不变。基于土壤氮素供需方程估测的常量和高量有机肥处理(M1和M2)的有机肥替代率与基于作物氮素吸收量得到的有机肥替代率相关系数(R2)达到0.78和0.84(P0.01),相对均方根误差(RMSE)均小于15%(分别为10.4%和14.6%),表明土壤氮素供需方程可以较好地估测土壤有机肥替代率。基于作物氮素吸收量和土壤氮素供需方程能够准确反映长期有机培肥下黑土有机肥替代率的变化规律。本研究结果表明,基于作物氮素吸收量和土壤氮素供需方程两种方法验证,高产条件下有机肥替代率是土壤肥力的函数;随着有机肥施肥年限的增加,土壤肥力提升,有机肥替代率逐渐增加。     

长期施肥下灰漠土有机碳组分含量及其演变特征

采用湿筛和重液悬浮的物理分组方法分析了18年不同施肥模式下灰漠土有机碳组分含量差异及其演变特征。结果表明:与不施肥相比,长期有机无机肥配施(NPKM和1.5 NPKM)增加各有机碳组分的效果最显著,且粗和细自由颗粒有机碳、物理保护有机碳、矿物结合有机碳增加速率最高,平均分别达到0.12、0.06、0.08及0.17g/(kg.a);秸秆还田使粗和细自由颗粒有机碳分别以0.05和0.03 g/(kg.a)的速率增加,而撂荒和施化肥维持着各有机碳组分的含量。不同有机碳组分间存在显著的相关性,其中以粗自由颗粒有机碳含量增幅最高,不同施肥模式下平均增幅是其它有机碳组分的2.18~.0倍;以矿物结合有机碳所占比例最高,达到56.9%7~7.8%,说明粗自由颗粒有机碳对施肥较敏感,而矿物结合有机碳是灰漠土固存有机碳的主要形式。综上分析,长期有机无机肥配施是提高灰漠土有机碳组分含量和培肥土壤的有效模式。     

长期施肥条件下灰漠土磷的吸附与解吸特征

通过等温吸附与解吸试验,研究了长期施肥条件下不同磷素含量水平的灰漠土耕层0~20 cm土壤磷素吸附与解吸特征。结果表明,在实验浓度范围内,不同Olsen-P水平的灰漠土土壤,随外源磷量的增加,磷的吸附量、解吸量及解吸率均逐渐增大,吸附率逐渐减小。土壤Olsen-P含量水平与土壤磷素吸附饱和度（DPS）的大小呈正相关关系。处理间比较,土壤最大吸附量（Xm）值为CK>NPK≈NPKM>PK≈NPKS、且处理间达到极显著差异水平;NPK处理的吸附常数（K）值与土壤最大缓冲容量（MBC）值均极显著地大于CK、PK、NPKM和NPKS处理。该4个处理间比较：K值无显著差异,MBC值CK极显著大于PK和NPKS处理、CK与NPKM、PK与NPKS处理间差异不显著。化肥配施有机肥或秸秆的处理土壤易解吸磷（RDP）值极显著大于单施化肥的处理,释磷效果以化肥有机肥配施为最优。     

长期施肥条件下灰漠土磷的吸附与解吸特征

通过等温吸附与解吸试验,研究了长期施肥条件下不同水平的灰漠土耕层0～ 20 cm土壤磷素吸附与解吸特征.结果表明,在实验浓度范围内,不同Olsen-P水平的灰漠土土壤,随外源磷量的增加,磷的吸附量、解吸量及解吸率均逐渐增大,吸附率逐渐减小.土壤Olsen-P含最水平与土壤磷素吸附饱和度(DPS)的大小呈正相关关系.处理间比较,土壤最大吸附量(Xm)值为CK＞ NPK≈NPKM＞ PK≈NPKS、且处理间达到极显著差异水平;NPK处理的吸附常数(K)值与土壤最大缓冲容量(MBC)值均极显著地大于CK、PK、NPKM和NPKS处理.该4个处理间比较:K值无显著差异,MBC值CK极显著大于PK和NPKS处理、CK与NPKM、PK与NPKS处理间差异不显著.化肥配施有机肥或秸秆的处理土壤易解吸磷(RDP)值极显著大于单施化肥的处理,释磷效果以化肥有机肥配施为最优.     

Electrical resistivity of arable gray forest soils

The electrical resistivity of gray forest soils and gray forest soils with a second humus horizon was studied in the Bryansk Opol’e region. The dependence of electrical resistivity on the soil’s organic content, moisture, and bulk density was found. It was concluded that the supply of organic matter in the upper layer (50 cm) can be estimated in wet conditions using the equation C_supply = 2.7ER + 34.3 (t/ha).     

Nitrogen sequestration under long-term paddy management in soils developed on contrasting parent material

Long-term paddy management promotes nitrogen (N) sequestration, but it is unknown to what extent the properties of the parent soil modify the management-induced N sequestration in peptide-bound amino acids (AA-N). We hypothesized that paddy management effects on the storage of AA-N relate to the mineral assembly. Hence, we determined contents and chirality of peptide-bound amino acids in paddy soils developed on contrasting parent material (Vertisols, Andosols, Alisols in Indonesia, Alisols in China, and Gleysol/Fluvisol in Italy). Adjacent non-paddy soils served as references. Selected samples were pre-extracted with dithionite–citrate–bicarbonate (DCB) to better understand the role of reactive oxide phases in AA-N storage, origin, and composition. The results showed that topsoil N and AA-N stocks were significantly larger in paddy-managed Andosols and Chinese Alisols than in their non-paddy counterparts. In other soils, however, paddy management did not cause higher proportions of N and AA-N, possibly because N fixing intercrops masked the paddy management effects on N sequestration processes. Among the different soils developed on contrasting parent material, AA-N stocks were largest in Andosols, followed by Alisols and Fluvisols, and lowest in Vertisols. The N storage in amino acid forms went along with elevated d-contents of bacteria-derived alanine and glutamic acid, as well as with increasing stocks of DCB-extractable Fe, Mn, and Al. Other d-amino acids, likely formed by racemization processes, did not vary systematically between paddy and non-paddy managed soils. Our data suggest that the presence of oxides increase the N sequestration in peptide-bound amino acids after microbial N transformations.     

长期不同施肥模式下碱性土有效磷对磷盈亏的响应

[目的]磷素易于在土壤中固定,碱性土壤更甚,影响着磷肥的肥效和利用效率.研究长期施用磷肥对我国北方碱性土有效磷与磷盈亏的影响,为碱性土地区合理施用磷肥提供理论依据.[方法]本研究是基于河北、北京、山东、天津、河南和山西的6个冬小麦-夏玉米轮作长期定位施肥试验,试验周期为1991-2011年.所有定位施肥试验均设有不施磷...     

长期施肥红壤钾素在有机无机复合体中的分布

【目的】土壤中的有机无机复合体是承载土壤养分的重要结构单元,土壤钾素含量的变化反映在不同粒级有机无机复合体中。本研究选用始于1990年(祁阳)和1986年(进贤)的旱地红壤长期定位试验,研究长期不同施肥对土壤交换性钾、非交换性钾、全钾在不同粒级有机无机复合体中分布的影响。【方法】祁阳和进贤试验点均选择不施肥(CK)化学氮、磷肥配施(NP)、NP基础上施用化学钾肥(NPK)及NPK基础上配施有机肥(NPKM)四个处理,采集0-20 cm深度的土壤样品通过Stokes定律计算各粒级复合体沉降速率,采用虹吸管法分离出不同粒级有机无机复合体。采用1.0 mol/L中性醋酸铵浸提土壤交换性钾,1.0 mol/L沸硝酸浸提土壤非交换性钾,氢氧化钠710℃提取土壤全钾钾离子浓度采用火焰光度计测定。【结果】两试验点土壤96.4%~98.9%的交换性钾、87.9%~96.7%的非交换性钾和95.1%~96.7%的全钾存在0~50μm粒级复合体中,尤其2μm粒级复合体是三种形态钾素的主要贮存库76.3%~92.3%的交换性钾、45.8%~73.7%的非交换性钾和49.4%~70.6%的全钾集中在该粒级。两试验点NP处理与CK相比,2μm粒级复合体中非交换性钾含量降低5.4~8.3 mg/kg.降低幅度为8.2%~16.3%。施钾肥主要改变2 m粒级复合体中交换性钾和非交换性钾含量进贤NPK与NP处理相比分别增加36.7和9.5 mg/kg,增加幅度分别为64.5%和15.7%;而NPKM处理则较NP处理分别增加147.4和91.2 mg/kg增幅分别为258.9%和151.1%。祁阳NPK与NP处理相比,2μm粒级复合体中交换性钾和非交换性钾含量分别增加52.9和20.3 mg/kg增加幅度分别为104.9%和47.6%;NPKM与NP处理相比分别增加219.5和41.3 mg/kg增幅分别为435.9%和96.9%。长期施肥对两试验点各粒级复合体中全钾含量的影响不大。2、2~10及10~50μm粒级复合体三种形态钾素含量较高,是供给植物生长的主要钾源,其中2μm粒级复合体中交换性钾、非交换性钾含量与产量之间均存在显著正相关关系(P0.05)。【结论】2μm粒级复合体是土壤钾素的主要贮存库。在长期不施钾肥条件下土壤2μm粒级复合体中交换性钾和非交换性钾含量降低,施钾有利于该粒级复合体中交换性钾和非交换性钾积累。旱地红壤2、2~10及10~50μm粒级复合体钾素含量高且与产量之间存在显著的正相关关系是植物钾素主要供源。     

长期施肥下我国灌淤土粮食产量和土壤养分的变化

【目的】 灌淤土是我国西北地区重要的粮食和经济作物土壤。了解灌淤土上作物产量的变化,及其对长期施肥的响应,以及灌淤土生产力的变化与其氮磷钾含量的关系,为西北地区作物增产和灌淤土培肥与可持续利用提供理论依据。 【方法】 1988到2004年间,在宁夏银川市、吴忠市、石嘴山市和新疆和田市典型灌淤土区域陆续建立了7个国家耕地质量监测点。2016年,利用时间趋势分析法,探讨了作物产量随时间的变化趋势,分析了长期不施肥和常规施肥条件下,玉米、小麦和水稻产量、产量变异系数、可持续性指数、增产率及地力贡献指数的变化特征,并进一步探讨了增产率与土壤养分的关系。 【结果】 灌淤土上小麦产量随时间呈现递增的趋势,在2004年达到最高 (7.58 t/hm2),之后保持稳定,2016年约为初始年产量的3倍;玉米产量随时间一直呈递增趋势,2016年平均产量为9.8 t/hm2,约为初始年的两倍;水稻产量近年来变化不大。与不施肥相比,常规施肥下小麦、玉米 (28年间) 和水稻 (8年间) 分别平均增产3.43倍、3.20倍和1.21倍,产量可持续性指数分别提高了18.8%、148%和13.9%。监测以来,小麦和玉米农田的地力贡献指数略有下降,但变化不显著。水田的地力贡献指数以每年0.0125的速率增加。28年间,常规施肥使土壤全氮含量从0.4 g/kg提高到1.1 g/kg,有效磷和速效钾含量变化不大。小麦与玉米的增产率与土壤全氮含量呈显著直线正相关关系,小麦、玉米和水稻的平均氮肥农学效率分别为9.8、16.8和27.4 kg/kg。 【结论】 灌淤土上常规施肥 (主要是氮肥)有效提高了玉米、小麦和水稻的产量。土壤全氮含量呈增加趋势,有效磷和有效钾含量基本平稳。土壤肥力对玉米和小麦产量的贡献呈下降趋势,对水稻产量的贡献高且平稳。因此,灌淤土应在合理施用氮肥的同时,注重采取提升地力,实现作物的高产和高效。      

长期定位施肥对土壤有机无机复合状况的影响

长期施用化肥、有机肥或有机无机肥配施均能提高潮土和旱地红壤的原土复合量 ,有机无机肥配施还可以提高红壤性水稻土耕层的原土复合量 ,单施化肥对红壤性水稻土的原土复合量影响不大 ;长期施肥降低 3种土壤的原土复合度 ,但提高了土壤的增值复合量和增值复合度。施有机肥或有机无机肥配施土壤的增值复合量高于施化肥的土壤 ,但其增值复合度却低于施化肥的土壤。长期施肥还影响土壤有机无机复合体的粒径分级 ,施肥一般都可提高土壤中粘粒级和粉砂级复合体含量 ,降低细砂级复合体含量。长期施用有机肥或有机无机肥配施还可以提高 3种土壤中的G0、G1和G2等 3组复合体含量 ,并且有机无机肥配施可以促使G0和G1组复合体向水稳性强的G2组复合体转化。     

长期不同施肥下黑土与灰漠土有机碳储量的变化

采用长期试验,研究了20年不同施肥下1 m深黑土与灰漠土有机碳含量与碳储量的剖面变化。结果表明,单施化肥和不施肥对黑土1 m土层有机碳储量没有显著影响,但灰漠土略有降低。有机肥配施化肥能显著提高土壤有机碳含量和储量。高量有机肥配施化肥（NPKM2）能提高020 cm和2040 cm土层土壤有机碳含量,黑土分别提高56.6%和49.6%、灰漠土提高143.1%和46.9%;常量有机无机配施（NPKM）效果较差,增幅分别为黑土35.1%和35.3%,灰漠土80.2%和4.1%。两种土壤1 m土体的有机碳储量,NPKM2处理分别提高了C 30.7 t/hm2与C 40.6 t/hm2。显然,有机无机肥配施可以显著提高1 m深土体中有机碳储量,主要是由于提高了040 cm土层土壤有机碳含量。     

长期施肥红壤性稻田和旱地土壤有机碳积累差异

  【目的】  提高土壤有机碳水平对提升农田生产力有重要意义。基于长期定位施肥试验,比较施肥影响下相同成土母质发育的红壤性稻田和旱地土壤的总有机碳 (TOC) 及其组分的积累差异,以深入理解红壤有机碳的固持及稳定机制。  【方法】  稻田和旱地长期施肥试验分别始于1981和1986年,包含CK (不施肥对照)、NPK (施氮磷钾化肥) 和NPKM (有机无机肥配施) 3个处理,在2017年晚稻和晚玉米收获后,采集两个试验上述处理的耕层 (0—20 cm) 土样,通过硫酸水解法分离土壤活性与惰性有机碳,测定并计算土壤中TOC及其组分的含量及储量,并利用Jenny模型拟合试验期间耕层土壤TOC含量的变化动态,估算土壤固碳潜力。  【结果】  与CK相比,长期施肥可提高稻田和旱地土壤各有机碳组分的含量,且NPKM处理的效果优于NPK处理。相比于稻田土壤,施肥对旱地土壤各有机碳组分含量的提升更加明显。NPK和NPKM处理下,旱地土壤活性有机碳组分Ⅰ、活性有机碳组分Ⅱ、惰性有机碳含量的增幅分别是稻田土壤的2.7、2.7、5.8倍和2.0、1.4和2.5倍。不论施肥与否,稻田土壤TOC的固存量和固存潜力均显著高于旱地土壤。施肥促进土壤固碳,在稻田和旱地土壤上,NPKM处理的TOC固存量分别是NPK处理的1.7和25.5倍,TOC固存潜力则分别是NPK处理的1.4和5.8倍。长期不同施肥均显著提高稻田和旱地土壤年均碳投入量,线性拟合方程表明,随碳投入量增加,土壤活性有机碳储量的累积对稻田、旱地土壤TOC储量累积的贡献率分别达64.7%、44.6%。不同处理间稻田与旱地土壤活性有机碳 (包括活性有机碳组分Ⅰ与活性有机碳组分Ⅱ) 含量的差异可解释其TOC含量差异的52.9%～60.0%。  【结论】  与施氮磷钾化肥相比,有机无机肥配施可更好的促进土壤固碳,且在旱地土壤上的促进作用比在稻田土壤上更为明显。与稻田土壤相比,旱地土壤各有机碳组分含量的变化对长期施肥的响应更敏感,且在施氮磷钾化肥条件下表现更为明显。红壤性稻田和旱地土壤TOC积累的主要贡献组分分别为活性有机碳和惰性有机碳。红壤植稻虽有利于有机碳固持,但红壤性稻田土壤的活性碳占比较高,可能易因不当管理而发生损失。     

Carbon fluxes and the carbon budget in agroecosystems on agro-gray soils of the forest-steppe in the Baikal region

Field studies devoted to the transformation of the carbon cycle in agroecosystems on agro-gray soils (including soils contaminated with fluorides from aluminum smelters) in dependence on the changes in the hydrothermic conditions were performed for the first time within the framework of the long-term (1996–2010) soil monitoring in the forest-steppe zone of the Baikal region. The major attention was paid to the impact of the environmental factors on the synthesis and microbial destruction of organic carbon compounds. Certain differences in the fluxes and budget of carbon were found for the plots with cereal and row crops and for the permanent and annual fallow plots. The adverse effect of fluorides manifested itself in the enhanced C-CO₂ emission under unfavorable water and temperature conditions. The long-term average C-CO₂ emission from the soils contaminated with fluorides in agroecosystems with wheat after fallow was higher than that from the uncontaminated soil (179 and 198 g of C/m², respectively) and higher than that in the agroecosystems with a potato monoculture (129 and 141 g of C/m², respectively). At the same time, no significant variations in the content of the carbon of the microbial biomass (C_micr) in dependence on the environmental factors were found. The utilization of carbon for respiration and for growth of the soil microorganisms on the contaminated soil were unbalanced in particular years and for the entire period of the observations. The ratio between the fluxes of the net mineralized and re-immobilized carbon was used for the integral assessment of the functioning regime of the agroecosystems and the loads on them. Independently from the soil contamination with fluorides, the loads on the agroecosystems with wheat were close to the maximum permissible value, and the loads on the agroecosystems with potatoes were permissible. It was shown that the carbon deficit in the uncontaminated soils was similar under the wheat and potatoes (?30 and ?28 g of C/m², respectively). In the contaminated soils, it was higher under the potato monoculture and reached ?41 g of C/m².     

Phosphorus adsorption and desorption characteristics of different textural fluvo-aquic soils under long-term fertilization

Journal of Soils and Sediments - Phosphorus (P) fertilizer has been widely applied to improve crop yields in the North China Plain; however, most of applied P fertilizer is disabled due to the...