Contrasting effects of bamboo leaf and its biochar on soil CO2 efflux and labile organic carbon in an intensively managed Chinese chestnut plantation

The effects and associated mechanisms of the application of organic residues or their derived biochar on the dynamics of soil organic C and soil CO₂ efflux in planted soils are poorly understood. This paper investigated the impact of bamboo leaf and the derived biochar applications on soil CO₂ efflux and labile organic C in an intensively managed Chinese chestnut plantation in a 12-month field study. The treatments studied included Control, application of bamboo leaf (Leaf), and application of biochar (Biochar). The Leaf treatment increased (P?2 efflux and concentrations of water-soluble organic C (WSOC) and microbial biomass C (MBC). The Biochar treatment increased soil CO₂ efflux and WSOC and MBC only in the first month after application, but such effects diminished thereafter. The annual cumulative soil CO₂ emission was increased by 16 % by the Leaf treatment as compared to the Control, but there was no difference between the Biochar and Control treatments. The soil organic C (SOC) storage was increased by biochar addition but not by bamboo leaf addition. An exponential relationship between soil temperature and soil CO₂ efflux was observed regardless of the treatment. Soil CO₂ efflux was correlated to soil WSOC (P?Q ₁₀) of soil CO₂ efflux was ranked as Leaf?>?Biochar?>?Control. In comparison with the application of fresh bamboo leaf, pyrolyzed bamboo leaf (biochar) application decreased CO₂ effluxes and increased C sequestration in the soil.     

施肥对板栗林土壤 CH4 吸收通量动态的影响

为了探明无机肥和有机肥施用对板栗林地土壤 CH4 吸收通量动态的影响,探讨板栗林地土壤 CH4 通量与环境因子之间的关系,在浙江省临安市典型板栗林样地布置施肥试验。于2011年6月~2012年6月期间,采用静态箱-气相色谱法测定了不施肥（CK）、 无机肥（IF）、 有机肥（OF）和有机无机混合肥（OIF）处理下土壤CH4 吸收通量的全年动态变化,并测定了土壤温度、 土壤水分、 水溶性有机碳（WSOC）和微生物量碳（MBC）含量。结果表明,板栗林土壤CH4 吸收通量呈现明显的季节性变化,最大值出现在9月,最小值出现在2~3月;施肥处理均显著抑制了土壤 CH4 的吸收,具体表现为 IF、 OF和OIF处理下土壤CH4年吸收量与CK处理［CH4 3.09 kg/(hm2a)］相比分别减少了7.0%、 1.6% 和 4.4%。此外,施肥显著增加了土壤WSOC和MBC含量（P 0.05）,且施肥使土壤碱解氮、 铵态氮、 硝态氮、 全氮和有机质含量均有不同程度的增加。相关性分析表明,土壤CH4 吸收通量与土壤表层5 cm处温度之间呈显著正相关（P 0.05）,但与土壤水分、 MBC含量之间没有显著相关性;土壤CH4 吸收与土壤WSOC含量之间（除CK处理外）均具有显著相关性（P 0.05）。因此,施肥引起土壤理化性质［如 NH+4-N、 NO-3-N、 全氮（TN）、 有机碳（SOC）等］和 WSOC 含量的改变可能是施肥显著抑制了板栗林土壤CH4排放的主要原因。     

施肥对板栗林土壤活性碳库和温室气体排放的影响

在浙江省临安市典型板栗林试验地,利用静态箱-气相色谱法测定了不同施肥条件下板栗林土壤CO2和N2O排放速率,同时测定了土壤水溶性有机碳（WSOC）和微生物量碳（MBC）含量。初步探讨了施肥对板栗林土壤活性碳库与温室气体排放速率的影响,以及土壤温室气体排放速率与活性碳库之间的关系。本试验设置不施肥（CK）、 无机肥（IF）、 有机肥 （OF）和有机无机混合肥（OIF,1/2无机肥和1/2有机肥）4个施肥处理。结果表明, 施肥1个月后,与不施肥（CK）处理相比,无机肥（IF）、 有机肥（OF）和有机无机混合肥（OIF）处理下土壤CO2排放速率分别增加了87%、 38%和61%, N2O排放速率分别增加了101%、 67%和95%; 而施肥6个月后,与CK处理相比,IF、 OF和OIF处理下土壤CO2 排放速率分别增加了51%、 43%和64%,N2O排放速率分别增加了21%、 29%和47%。同时,施肥显著增加板栗林土壤WSOC和MBC含量（P＜0.05）。此外,土壤CO2和N2O排放速率与WSOC含量均呈显著正相关（P0.05）,而与MBC含量没有显著的相关性。因此,施肥引起板栗林地土壤WSOC含量增加可能是导致板栗林地土壤温室气体排放增加的重要原因之一。     

不同经营措施对毛竹林土壤有机碳含量及季节动态的影响

Soil samples for conventional management （CM） and intensive management （IM） practices were taken over a year at 2-month intervals to determine the effect of management practices on soil organic carbon （SOC） and to quantify seasonal dynamics in SOC for bamboo （Phyllostachys pubescens Mazel ex H. de Lehaie） stands. The results with IM compared to CM showed large decreases in total organic carbon （TOC）, microbial biomass carbon （MBC）, water-soluble organic carbon （WSOC）, and the MBC/TOC ratio in the soils. With all IM plots in the 0-20 cm depth across sampling periods, average decreases compared with CM were： TOC, 12.1%; MBC, 26.1%; WSOC, 29.3%; the MBC/TOC ratio, 16.1%; and the WSOC/TOC ratio, 20.0%. Due to seasonal changes of climate, seasonal variations were observed in MBC and WSOC. Soil MBC in the 0-20 cm depth in September compared to May were 122.9% greater for CM and 57.6% greater for IM. However, due primarily to soil temperature, soil MBC was higher during the July to November period, whereas because of soil moisture, WSOC was lower in July and January. This study revealed that intensive management in bamboo plantations depleted the soil C pool; therefore, soil quality with IM should be improved through application of organic manures.     

Effect of organic and inorganic sources of nutrients on soil microbial activity and soil organic carbon build-up under rice in west coast of India

The effect of medium-term (5 years) application of organic and inorganic sources of nutrients (as mineral or inorganic fertilizers) on soil organic carbon (SOC), SOC stock, carbon (C) build-up rate, microbial and enzyme activities in flooded rice soils was tested in west coast of India. Compared to the application of vermicompost, glyricidia (Glyricidia maculate) (fresh) and eupatorium (Chromolaena adenophorum) (fresh) and dhaincha (Sesbania rostrata) (fresh), the application of farmyard manure (FYM) and combined application of paddy straw (dry) and water hyacinth (PsWh) (fresh) improved the SOC content significantly (p < 0.05). The lowest (p < 0.05) SOC content (0.81%) was observed in untreated control. The highest (p < 0.05) SOC stock (23.7 Mg C ha^?1) was observed in FYM-treated plots followed by recommended dose of mineral fertilizer (RDF) (23.2 Mg C ha^?1) and it was lowest (16.5 Mg C ha^?1) in untreated control. Soil microbial biomass carbon (C_mb) (246 µg g^?1 soil) and C_mb/SOC (1.92%) were highest (p < 0.05) in FYM-treated plot. The highest (p < 0.05) value of metabolic quotient (qCO₂) was recorded under RDF (19.7 µg CO₂-C g^?1 C_mb h^?1) and untreated control (19.6 µg CO₂-C g^?1 C_mb h^?1). Application of organic and inorganic sources of nutrients impacted soil enzyme activities significantly (p < 0.05) with FYM causing highest dehydrogenase (20.5 µg TPF g^?1 day^?1), phosphatase (659 µg PNP g^?1 h^?1) and urease (0.29 µg urea g^?1 h^?1) activities. Application of organic source of nutrients especially FYM improved the microbial and enzyme activities in flooded and transplanted rice soils. Although the grain yield was higher with the application of RDF, but the use of FYM as an organic agricultural practice is more useful when efforts are intended to conserve more SOC and improved microbial activity.     

Organic Farming Affects C and N in Soils Under Olive Groves in Mediterranean Areas

Under semiarid climatic conditions, intensive tillage increases soil organic matter losses, reduces soil quality, and contributes to climate change due to increased CO₂ emissions. There is a need for an agricultural management increasing soil organic matter. This paper presents the organic carbon (OC) and nitrogen (N) stocks, C:N ratio and stratification ratios (SRs) of these properties for olive groves soils under long‐term organic farming (OF), and conventional tillage (CT) in Los Pedroches valley, southern Spain. The results show that OF increased C and N stocks. The soil organic carbon (SOC) stock was 73·6 Mg ha⁻¹ in OF and 54·4 Mg ha⁻¹ in CT; and the total nitrogen (TN) stock was 7·1 Mg ha⁻¹ and 5·8 Mg ha⁻¹ for OF and CT, respectively. In the surface horizon (A: 0–16·9 cm in OF and Ap: 0–21·8 cm in CT) and Bw horizon (16·9–49·6 cm in OF and 21·8–56 cm in CT), SOC and TN concentrations and C:N ratios were higher in OF than in CT. Soil properties stratification in depth, expressed as a ratio, indicates the soil quality under different soil management systems. The SR of SOC ranged from 2·2 to 3·1 in OF and from 2·1 to 2·2 in CT. However, only SR2 (defined by Ap‐A/C) showed significant differences between CT and OF. The SR of TN showed similar trends to that of the SR of SOC. Organic farming contributes to a better soil quality and to increased carbon sequestration. Copyright © 2013 John Wiley & Sons, Ltd.     

Changes in the soil C and N contents,C decomposition and N mineralization potentials in a rice paddy after long-term application of inorganic fertilizers and organic matter

A long-term experiment on combined inorganic fertilizers and organic matter in paddy rice (Oryza sativa L.) cultivation began in May 1982 in Yamagata, northeastern Japan. In 2012, after the 31^st harvest, soil samples were collected from five fertilizer treatments [(1) PK, (2) NPK, (3) NPK + 6 Mg ha^?1 rice straw (RS), (4) NPK + 10 Mg ha^?1 rice straw compost (CM1), and (5) NPK + 30 Mg ha^?1 rice straw compost (CM3)], at five soil depths (0–5, 5–10, 10–15, 15–20 and 20–25 cm), to assess the changes in soil organic carbon (SOC) content and carbon (C) decomposition potential, total nitrogen (TN) content and nitrogen (N) mineralization potential resulting from long-term organic matter addition. The C decomposition potential was assessed based on the methane (CH₄) and carbon dioxide (CO₂) produced, while the N mineralization potential was determined from the potassium chloride (KCl)-extractable ammonium-nitrogen (NH₄⁺-N), after 2, 4, 6 and 8 weeks of anaerobic incubation at 30°C in the laboratory. Compared to NPK treatment, SOC in the total 0–25 cm layer increased by 67.3, 21.0 and10.8%, and TN increased by 64.2, 19.7 and 10.6%, in CM3, RS and CM1, respectively, and SOC and TN showed a slight reduction in the PK treatment by 5.2 and 5.7%, respectively. Applying rice straw compost (10 Mg ha^?1) instead of rice straw (6 Mg ha^?1) to rice paddies reduced methane production by about 19% after the soils were measured under 8 weeks of anaerobic incubation at 30°C. Soil carbon decomposition potential (Co) and nitrogen mineralization potential (No) were highly correlated with the SOC and TN contents. The mean ratio of Co/No was 4.49, lower than the mean ratio of SOC/TN (13.49) for all treatments, which indicated that the easily decomposed organic matter was from soil microbial biomass and soil proteins.     

施肥对山核桃林地土壤N2O排放的影响

【目的】N2O是重要的温室气体,其增温潜势是CO2的298倍,而且破坏臭氧层。森林生态系统是陆地生态系统的重要组成部分,占全球陆地面积的33%,森林土壤N2O排放对全球气候变化有重大的影响。山核桃（Carya cathayensis）是非常重要的经济林,是山核桃主产区农民的主要经济来源。近年来,农民采取施用无机肥和有机肥等措施来提高山核桃产量,但施肥对山核桃林地土壤N2O排放的影响尚不清楚,本文以不施肥作为对照（CK）,研究单施有机肥(Organic fertilizer, OF)、单施化肥(Inorgnaic fertilizer, IF)、 有机无机肥配施(Organic fertilizer and Inorgnaic fertilizer, OIF)对山核桃林地土壤N2O气体排放的影响。【方法】 利用静态箱-气相色谱法对山核桃林地土壤N2O排放通量进行了为期1年的测定。采样箱为组合式,即由底座、顶箱组成,均用PVC板做成,面积为30 cm30 cm,高度为30 cm。气体样品采集频率基本为每月1次,采集气体时,将采集箱插入底座凹槽（凹槽内径和深度均为5 cm）中,用蒸馏水密封,分别于关箱后0、 10、 20、 30 min采集,用注射器抽样60 mL置于气袋,带回实验室用岛津GC-2014气相色谱仪进行测定,检测器为电子捕获检测器（ECD）,检测器温度为250℃。【结果】 山核桃林地不同施肥土壤N2O排放通量均呈现明显的季节性变化,以夏季最高、冬季最低。土壤N2O的排放通量在N -0.021~ 0.161 mg/(m2 h)之间变化,不同处理土壤N2O年累积排放量依次为单施有机肥单施化肥有机无机肥配施对照,对应值分别为N 2.17、 2.01、 1.94和0.94 kg/（hm2a）。与对照相比,施肥处理显著增加N2O的排放（P0.05）,但是各施肥处理N2O排放量之间的差异不显著。单施有机肥和有机无机肥配施处理土壤N2O排放通量与土壤水溶性有机碳含量和微生物量碳呈显著相关关系（P0.05）,而单施化肥和对照则无显著相关性。土壤N2O排放通量与地下5 cm处土壤温度均显著相关（P0.05）,而土壤N2O排放与土壤含水量间没有显著相关性。【结论】 施肥显著促进了山核桃林地土壤N2O排放,不同施肥处理之间山核桃林地土壤N2O排放无显著差异。添加有机肥引起土壤水溶性有机碳和微生物碳的增加可能是有机肥增加山核桃林地土壤N2O排放速率的主要原因之一。     

Converting natural evergreen broadleaf forests to intensively managed moso bamboo plantations affects the pool size and stability of soil organic carbon and enzyme activities

Land-use change significantly affects the soil organic C (SOC) dynamics and microbial activities. However, the roles of chemical composition of SOC and enzyme activity in the change in the SOC mineralization rate caused by land-use change are poorly understood. This study aimed to investigate the impact of land-use conversion from natural evergreen broadleaf forests to intensively managed moso bamboo (Phyllostachys edulis) plantations on the pool size and mineralization rate of SOC, as well as the activities of C-cycling enzymes (invertase, β-glucosidase, and cellobiohydrolase) and dehydrogenase. Four paired soil samples in two layers (0–20 and 20–40 cm) were taken from adjacent evergreen broadleaf forest-moso bamboo plantation sites in Lin’an County, Zhejiang Province, China. Soil water-soluble organic C (WSOC), hot-water-soluble organic C (HWSOC), microbial biomass C (MBC), readily oxidizable C (ROC), the activities of C-cycling enzymes and dehydrogenase, and mineralization rates of SOC were measured. The chemical composition of SOC was also determined with ¹³C-nuclear magnetic resonance spectroscopy. The conversion of broadleaf forests to bamboo plantations reduced SOC stock as well as WSOC, HWOC, MBC, and ROC concentrations (P?<?0.05), decreased O-alkyl, aromatic, and carbonyl C contents, but increased alkyl C content and the alkyl C to O-alkyl (A/O-A) ratio, suggesting that the land-use conversion significantly altered the chemical structure of SOC. Further, such land-use change lowered (P?<?0.05) the SOC mineralization rate and activities of the four enzymes in the 0–20-cm soil. The decreased SOC mineralization rate associated with the land-use conversion was closely linked to the decreased labile organic C concentration and soil enzyme activities. The results demonstrate that converting broadleaf forests to moso bamboo plantations markedly decreased the total and labile SOC stocks and reveal that this conversion decreased the mineralization rate of SOC via changing the chemical composition of SOC and decreasing activities of C-cycling enzymes. Management practices that enhance C input into the soil are recommended to mitigate the depletion of SOC associated with land-use conversion to moso bamboo plantations.     

长期施肥下黑土活性有机碳变化特征

观测分析了黑土长期不同施肥30年后不同形态的活性有机碳含量(易氧化有机碳>轻组有机碳>微生物量碳>水溶性有机碳)的变化特征。结果表明,长期施用氮、氮磷和氮磷钾化肥对土壤活性有机碳无显著影响;长期施用有机肥以及有机肥配施化肥均显著提高了土壤活性有机碳含量,与不施有机肥相比,有机肥区组中土壤轻组有机碳和水溶性有机碳含量增幅较大,分别在122%～258%和237%～351%之间,而土壤易氧化有机碳和微生物量碳含量增幅分别在72%～98%和83%～112%。黑土不同形态活性有机碳对施肥的响应灵敏度为,轻组有机碳>水溶性有机碳>微生物量碳≈易氧化有机碳。因此,轻组有机碳是指示土壤有机碳变化的较好指标。     

Comparative Effects of Organic and Inorganic Fertilizers on Soil Organic Carbon and Wheat Productivity under Arid Region

ABSTRACT

Organic amendments in the soil perform better than synthetic fertilizers in regards to soil fertility and sustainable crop productivity. Experiments were conducted to compare the effects of organic and synthetic fertilizers on soil fertility and wheat (Triticum aestivum L.) productivity. Soil fertility and protein contents of wheat grains (13.2% and 13.3% during 2005–06 and 2006–07, respectively) were improved by organic amendments. However, synthetic fertilizer (at the rate of 150, 100, and 60 kg ha^?1 N, P₂O₅, and K₂O, respectively) applications resulted in the maximum grain yield (4.05 and 4.46 t ha^?1 during 2005–06 and 2006–07, respectively). The observed and simulated soil organic carbon (SOC) reasonably agreed during RothC model validation (R ² = 0.99). Economic analysis showed the maximum net profit and relative increase in income ($729 US ha^?1 and 309%, respectively) from inorganic treatment. Application of synthetic fertilizers increased grain yield and farm profit while organic manure enhanced grain quality. The RothC model had potential for determining the SOC in organic farming under arid environment.     

Influence of vegetation types and soil properties on microbial biomass carbon and metabolic quotients in temperate volcanic and tropical forest soils

Abstract

There is limited knowledge about the differences in carbon availability and metabolic quotients in temperate volcanic and tropical forest soils, and associated key influencing factors. Forest soils at various depths were sampled under a tropical rainforest and adjacent tea garden after clear-cutting, and under three temperate forests developed on a volcanic soil (e.g. Betula ermanii and Picea jezoensis, and Pinus koraiensis mainly mixed with Tilia amurensis, Fraxinus mandshurica and Quercus mongolica), to study soil microbial biomass carbon (MBC) concentration and metabolic quotients (qCO₂, CO₂-C/biomass-C). Soil MBC concentration and CO₂ evolution were measured over 7-day and 21-day incubation periods, respectively, along with the main properties of the soils. On the basis of soil total C, both CO₂ evolution and MBC concentrations appeared to decrease with increasing soil depth. There was a maximal qCO₂ in the 0–2.5 cm soil under each forest stand. Neither incubation period affected the CO₂ evolution rates, but incubation period did induce a significant difference in MBC concentration and qCO₂ in tea soil and Picea jezoensis forest soil. The conversion of a tropical rainforest to a tea garden reduced the CO₂ evolution and increased the qCO₂ in soil. Comparing temperate and tropical forests, the results show that both Pinus koraiensis mixed with hardwoods and rainforest soil at less than 20 cm depth had a larger MBC concentration relative to soil total C and a lower qCO₂ during both incubation periods, suggesting that microbial communities in both soils were more efficient in carbon use than communities in the other soils. Factor and regression analysis indicated that the 85% variation of the qCO₂ in forest soils could be explained by soil properties such as the C:N ratio and the concentration of water soluble organic C and exchangeable Al (P < 0.001). The qCO₂ values in forest soils, particularly in temperate volcanic forest soils, decreased with an increasing Al/C ratio in water-soluble organic matter. Soil properties, such as exchangeable Ca, Mg and Al and water-soluble organic C:N ratio, were associated with the variation of MBC. Thus, MBC concentrations and qCO₂ of the soils are useful soil parameters for studying soil C availability and microbial utilization efficiency under temperate and tropical forests.     

Nitrogen Management for Sustainable Soil Organic Carbon Increase in Inceptisols Under Wheat Cultivation

Application of nitrogen (N) fertilizers to increase crop yield is a worldwide practice, which also has a positive influence on the soil organic carbon (SOC) increase. This study was carried out to investigate the dynamics of SOC and its fractions under different levels of N fertilization in wheat grown inceptisols of Northeast India over a period of 2 years. For the purpose of this study, fertilizer treatments with five N levels (40, 60, 72, 80, and 100 kg N ha^?1) were applied in randomized block design. Increased SOC particulate organic carbon (POC), humic acid carbon, and fulvic acid carbon were recorded under application of higher N. Stability of SOC as indicated by E4/E6 ratio and microbial biomass carbon (MBC) was higher on application of 72 kg N ha^?1. Among the SOC fractions, POC and MBC respond rapidly to different N fertilization rates. Available N and phosphatase activity increased while pH and urease activity (UA) decreased as a function of applied N fertilizer levels. Nitrogen fertilization increased wheat yield and biomass with insignificant differences among 100, 80, and 72 kg N ha^?1. Thus, under the present experimental conditions, application of 72 kg N ha^?1 can sustain SOC and soil health without compromising wheat yield in the inceptisols of Northeast India.     

不同有机替代方式下稻田土壤胶体磷流失潜力研究

土壤胶体因具有较大的比表面积及较强的吸附与迁移能力，其所携带的磷（胶体磷）已成为农田磷流失过程中的重要形态。为评估不同有机替代方式下稻田土壤胶体磷（P_coll）的活性和流失潜力，本文依托两种有机肥部分替代化肥（控氮控磷与控氮不控磷）方式下稻麦轮作长期定位试验，探讨了P_coll含量变化、流失风险及其与不同土壤活性磷组分之间的关系。控氮控磷试验（4 a）设有3个处理：不施磷肥（CK）、单施化肥（CF）、猪粪有机肥替代30%化学磷肥（OF）；控氮不控磷试验（24 a）设有3个处理：不施肥（CK）、单施化肥（CF）、猪粪有机肥替代40%化学氮肥（OF）。结果表明：在控氮控磷条件下，有机替代处理较单施化肥处理，土壤有机碳（SOC）、P_coll含量及其流失潜力（LPP）均无显著性差异，胶体钼蓝反应磷占比（R_MRP，MRP_coll/P_coll）显著降低1.76%（P < 0.05）。在控氮不控磷条件下，有机替代处理的土壤P_coll和SOC含量分别为13.08 mg/kg和20.19 g/kg，显著高于单施化肥78%和212.6%（P < 0.05）；较单施化肥，土壤LPP和R_MRP分别显著升高了1.89%和16.05%（P < 0.05）。两种有机替代方式下土壤P_coll与土壤全磷（TP）、真溶解态磷（TSP）、Olsen-P、CaCl₂-P等均呈极显著正相关（P < 0.01）；与土壤有机碳（SOC）在控氮不控磷条件下呈极显著正相关（P < 0.01），在控氮控磷条件下无显著相关性。以上结果表明，较控氮控磷有机替代方式，长期仅控氮的有机肥施用显著增加了土壤有机碳、胶体磷和不同活性磷组分含量，磷流失风险升高。因此，有机肥部分替代化肥养分等量控制是改善农田磷流失可行的施肥方式。     

Plant and Soil Responses to the Combined Application of Organic Amendments and Inorganic Fertilizers in Degraded Sodic Soils of Indo-Gangetic Plains

ABSTRACT

Soil degradation due to salinization and sodication is the paramount threat in Indo-Gangetic plains. The studies on reclamation and management of such soils can provide a pragmatic solution for improving fertility and productivity of these soils. Lack of organic matter and poor availability of nutrients are the major factors for low productivity of sodic soils. Rice-wheat is a major cropping system in Indo-Gangetic alluvial plain region even in reclaimed sodic soils and farmers used inorganic fertilizers only to get higher yields. In this study, we used different organic sources of amendments in conjunction with different nitrogen (N) doses supplied through inorganic fertilizers to investigate the combined effect of organic and inorganic amendments on soil fertility and the productivity of rice- wheat system in sodic soils. Salt tolerant varieties of rice and wheat were grown in sodic soil (pH: 9.30, EC: 1.12 dSm^?1 and exchangeable sodium percentage, ESP: 52) during 2014–15 to 2016–17 in a field experiment with 13 treatment combinations of organic and inorganic amendments (T₁- (control) 100% of recommended dose of N (RDN), T₂-municipal solid waste compost (MSWC) @10 t ha^?1 + 50%RDN, T₃- MSWC @10 t ha^?1 + 75% RDN,T₄- MSWC @10 t ha^?1 + 100%RDN, T₅-Vermicompost (VC) @10 t ha^?1 + 50% RDN, T₆- VC @10 t ha^?1 + 75% RDN, T₇-VC@10 t ha^?1 + 100% RDN, T₈- Farm yard manure (FYM) @ 10 t ha^?1 + 50% RDN,T₉- FYM@10 t ha^?1 + 75%RDN, T₁₀- FYM@10 t ha^?1 + 100% RDN, T₁₁-Pressmud (PM) @10 t ha^?1 + 50% RDN, T₁₂-PM@10 t ha^?1 + 75%RDN, and T₁₃- PM @ 10 t ha^?1 + 100% RDN). Use of organic amendments supplemented with reduced dose of N through inorganic fertilizer has significantly improved soil bio-physical and chemical properties. Application of VC@10 t ha^?1 + 100% RDN (T₇) decreased soil bulk density, pH, EC, ESP and Na content to 2.0, 4.2, 26.5, 42.8, and 56.6% respectively and increased soil organic carbon by 34.6% over control (T₁). Soil fertility in terms of available N, P, K, Ca, and Mg increased by 20.5, 33.0, 36.4, and 44%, respectively, over control (T₁). Soil microbial biomass carbon, nitrogen, and phosphorus also improved significantly due to combined use of organic amendments and inorganic fertilizers over the only use of inorganic fertilizers. Decreasing in soil sodicity and increasing soil fertility showed significant increase (P < 0.05) in crop growth, growth indices, and grain yields of rice and wheat. The study revealed that combined use of VC or MSW compost @10 t ha^?1 in conjunction with 75% RDN through inorganic fertilizers in sodic soils proved sustainable technology for restoration of degraded sodic soils and improving crop productivity.     

不同措施对滨海盐渍土壤呼吸、电导率和有机碳的影响

在苏北滩涂围垦区的轻度和中度盐渍土上,通过田间试验,研究了不同农田管理措施(传统耕作、施用有机肥、氮肥增施、秸秆还田和免耕)对土壤盐分、呼吸和有机碳等的影响。结果表明,0~40cm土层平均电导率在玉米种植季明显升高,小麦种植季出现小幅降低,轻度盐渍土的电导率为4.57~8.20 d S m~(~(-1)) ,中度盐渍土为4.89~10.13 d S m~(~(-1)) ,处理之间秸秆还田最低,免耕最高,秸秆还田和施用有机肥有效减少了土壤盐分含量。与中度盐渍土相比,轻度盐渍土的呼吸强度较高,在夏玉米和冬小麦种植季节分别高约16%和18%。有机肥、氮肥增施、秸秆还田处理的土壤呼吸均高于对照,而免耕较低。两组试验的土壤有机碳和微生物生物量碳均有缓慢增加,其中施用有机肥和秸秆还田可以大幅提高其含量。轻度盐渍土壤代谢熵高于中度盐渍土,总体上对照最高,免耕最低。     

长期施肥对黑土水溶性碳含量和碳矿化的影响

以农业部哈尔滨黑土生态环境重点野外科学观测试验站长期定位试验为平台,研究了长期施肥对黑土水溶性碳（WSOC）和矿化碳的影响。结果表明,施肥对土壤WSOC的含量有很大影响,比较而言,单施化肥对WSOC含量无明显影响,而施加有机肥可使黑土WSOC含量增加。土壤对水溶性有机碳的吸附量与平衡前水溶性有机碳的浓度显著相关。有机肥与无机肥料配施可以提高土壤矿化碳含量。     

Content of organic carbon and total nitrogen inStagnic Albeluvisols depending on fertilization

Abstract

The content of soil organic carbon (SOC) and total nitrogen (N_tot) was studied in a long-term field experiment with a three-field crop rotation (potato – spring wheat – spring barley) set up on arable sandy loam Stagnic Albeluvisol at Eerika, Tartu, Estonia. The studied factors were: (A) organic fertilizers with three treatments: (i) without organic fertilizer, (ii) farmyard manure (60 t ha^?1) used in every third year, and (iii) different organic (alternative) fertilizers (beet leaves + straw; pure beet leaves; slurry + straw; cereal straw) and (B) mineral nitrogen fertilizer with the rates: N-0; N-40; N-80; N-120 and N-160 kg ha^?1. The study years were 1993, 1996 and 1999. The average content of SOC (1.03%) was significantly influenced by the use of organic fertilizers. Only N_tot (mean value 0.110%) was influenced also by fertilization with mineral nitrogen. The C/N ratio (mean value 9.5) reflected changes in the content of SOC and N_tot     

Carbon pools and soil biochemical properties in manure‐based organic farming systems of semi‐arid New Mexico

The economic benefits of organic agriculture and its wide adoption are well documented, but the impact of that practice on soil C dynamics in irrigated croplands of semi‐arid regions is less well understood. In manure‐based organic production systems, land applications of animal wastes not only provide nutrients but could also contribute to soil carbon sequestration. A study was conducted in irrigated cotton (Gossypium arboreum L) agro‐ecosystems of New Mexico (USA) under conventional (CONV; 100 kg N/ha as urea and NH₄NO₃) and organic farming practices (OF for 3–9 yr; 50 Mg dry manure/ha) to assess the effect of OF on soil C stocks (organic, inorganic) and biochemical indices [microbial biomass C (MBC); respiration; metabolic quotient (qCO₂)]. In the plough layer (0–30 cm), soil organic carbon (SOC) stocks tended to be higher (although not statistically) under OF (35.9 Mg C/ha) than CONV (33.5 Mg C/ha). However, when the entire 100‐cm soil profile was considered, the total SOC under CONV exceeded that under OF by 39.8 Mg C/ha, but this may be influenced by other factors. Accounting for 52% of the total C stock, inorganic C was significantly higher under CONV than OF and was positively correlated with soil respiration and the H/C ratio of soil organic matter. While OF duration had no consistent effect on soil biochemical properties, MBC was significantly higher (1.5 times) and the qCO₂ (3–6 times) was lower in the organically fertilized soils than under CONV. These results suggest the development, under OF, of a soil microbial community that is larger and processes added C substrates more efficiently compared with the community present in CONV practices.     

Fate of 15N after combined application of rabbit manure and inorganic N fertilizers in a rice–wheat rotation system

The present study was carried out on pot experiments with rice (Oryza sativa L. cv. Wuyujing 7) and winter wheat (Triticum aestivum L. cv. Yangmai 6) rotation in a sandy and a clayey soil fertilized with ¹⁵N-labeled ammonium sulfate (AS) and ¹⁵N-labeled rabbit feces so as to study the mechanisms of reduction of fertilizer N loss by organic fertilizers. The treatments included: (1) control without any N fertilizer application; (2) fertilization with ¹⁵N-labeled AS (IF); (3) fertilization with labeled rabbit feces (OF); (4) fertilization with either 40% ¹⁵N-labeled rabbit feces and 60% unlabeled AS (IOF1) or (5) 40% unlabeled rabbit feces and 60% ¹⁵N-labeled AS (IOF2). In the rice season, the IOF treatments compared to the IF treatment decreased the percentage of lost fertilizer N from the sandy and clayey soils, whereas it increased the percentage of fertilizer N, present as mineral N and microbial biomass N (MBN). During the second season, when soils were cropped to winter wheat, the IOF treatments in comparison with the IF or OF treatment increased mineral N and MBN contents of soils sampled at tillering, jointing, and heading stages, and such increases were derived from the organic N fertilizer in the sandy soil and from the inorganic N fertilizer in the clayey soil. The increased MBN in the IOF treatments was derived from inorganic fertilizers applied both soils. Therefore, in the IOF treatment, during the rice season, the organic N increased the immobilization of inorganic N in MBN, while the inorganic N fertilizer applied to both soils stimulated the uptake of organic N and the organic N fertilizer increased the uptake of inorganic N by winter wheat; the inorganic N increased the recovery of organic N in the plant-soil system after harvesting the winter wheat.