Permanent–soil monitoring sites for documentation of soil‐fertility development after changing from conventional to organic farming

For monitoring soil fertility after changing farm management from highly conventional to organic farming on the newly established research farm of Kassel University, two permanent–soil monitoring sites were installed in 1999. Representative locations for installing the permanent–soil monitoring sites were selected using geographical information systems (GIS), based on available data from geology, topography, soil taxation, land use, and intensive auger‐borehole records and analysis with a very high spatial resolution of data. The soils are represented by a Luvisol derived from loess and a Vertisol developed from claystone. The soil properties of the two monitoring sites measured immediately after changing to organic farming showed high contents of extractable nutrients as a result of the former intensive fertilization practice during conventional farm management. The microbial soil properties of the two monitoring sites were in the medium range of regional soils. A first evaluation of the development of soil properties was done after 5 y of monitoring. The soil organic‐matter content increased slightly after grass‐clover and after application of farmyard manure. The amounts of K and P decreased clearly at the loess site without application of farmyard manure. At the clay site, the unique application of farmyard manure led to increasing contents of extractable K and P in the top soil. The variation of soil properties increased clearly after perennial crops like grass‐clover and in years after application of farmyard manure.     

Influence of inorganic fertilizers and organic amendments on soil organic matter and soil microbial properties under tropical conditions

 Soil organic matter level, mineralizable C and N, microbial biomass C and dehydrogenase, urease and alkaline phosphatase activities were studied in soils from a field experiment under a pearl millet-wheat cropping sequence receiving inorganic fertilizers and a combination of inorganic fertilizers and organic amendments for the last 11 years. The amounts of soil organic matter and mineralizable C and N increased with the application of inorganic fertilizers. However, there were greater increases of these parameters when farmyard manure, wheat straw or Sesbania bispinosa green manure was applied along with inorganic fertilizers. Microbial biomass C increased from 147 mg kg^–1 soil in unfertilized soil to 423 mg kg^–1 soil in soil amended with wheat straw and inorganic fertilizers. The urease and alkaline phosphatase activities of soils increased significantly with a combination of inorganic fertilizers and organic amendments. The results indicate that soil organic matter level and soil microbial activities, vital for the nutrient turnover and long-term productivity of the soil, are enhanced by use of organic amendments along with inorganic fertilizers. Received: 6 May 1998     

Assessment of plant nutrients’ dynamics in organically and conventionally managed soils by means of different extraction methods

The aim of this study was to investigate what kind changes in the soil fertility parameters occur depending on different farming methods. The field experiment was performed on sandy loam Luvisol during 2008–2014. The following treatments were carried out: organic (ORG), organic with farmyard cattle manure (ORGFYM) and conventional with farmyard cattle manure and mineral fertilizers (CONFYM). Soil samples were collected yearly in September and analyzed for P, K, Mg and Ca by the Mehlich III method. In parallel, ammonium lactate extractable P and K (AL method), and ammonium acetate extractable Mg and Ca (NH₄OAc-method) were determined. The Pearson correlation coefficients between the analysis results achieved by the Mehlich III method and alternative methods were calculated. In all the treatments, no significant changes in soil Corg content were established over seven years. A significant (p?AL in the soil but considerable decrease in the soil K_AL content was revealed. The application of cattle manure (60?t?ha^?1 for the 5-year crop rotation) in both organic and conventional treatments sustained the status of available nutrients in the soil. The Pearson correlation coefficients between Mehlich III and AL methods for P (r?=?0.770, p?r?=?0.922, p?4OAc-methods was found in the case of Mg (r?=?0.951, p?r?=?0.841, p?Mehlich III/P_AL quotient was inversely proportional with the Ca_{Mehlich III} values.     

Soil enzyme activities and abundance of microbial functional genes involved in nitrogen transformations in an organic farming system

Organic farming systems receive organic amendments to maintain soil fertility and supply nutrients for plant growth. This study investigated the effect of organic fertilizers (no amendment as control, compost, and manure), and their interaction with cover crops (millet, buckwheat, and black turtle bean) on soil enzyme activities, N transformation rates, and functional gene abundances under an organic production system. Organic N fertilizers had a stronger effect than cover crop type on soil function and functional gene abundances. Soil enzyme activities were increased by both compost and manure, but there were few differences between these treatments. Nitrification potential, nitrite oxidation potential, and denitrification potential were significantly higher in manure-treated than in control and compost-treated soils, indicating application of manure had a higher N loss potential than compost application in this organic farming system. Organic N fertilizers significantly increased the abundance of some genes involved in N mineralization, ammonification, and nitrification (sub, ureC, bacterial amoA and nxrB). The activity of ammonia-oxidizing bacteria and archaea were both increased by organic N fertilizers, and their activities were higher in manure-treated than in compost-treated soils. Overall, the abundance of functional genes was significantly correlated with their corresponding enzyme activity. However, functional gene abundance was less important than soil chemical and microbiological properties in explaining the variation in the corresponding enzyme activity.     

Microbial biomass turnover and enzyme activities following the application of farmyard manure to field soils with and without previous long-term applications

Summary We studied the build-up and turnover of microbial biomass following the addition of farmyard manure to an unmanured soil and to soils from a long-term experiment in which different levels of farmyard manure had been applied for the last 23 years. The application of farmyard manure at 15–90 t ha^-1 to previously unmanured soil increased the microbial biomass during the first 3 months of incubation but a gradual decline occurred with further incubation for up to 12 months. Microbial biomass C was positively correlated with soil organic C and ranged from 1.8% to 2.2% of organic C after 12 months of farmyard manure applications. Biomass turnover increased with the application of farmyard manure, ranging from 0.81 to 0.87 year^-1 with various levels of manure. Amendment of soils from the long-term manure experiment with various levels of farmyard manure led to a build-up and decline in biomass C as seen in the unmanured soils, but biomass C was higher in all treatments compared to the corresponding unmanured soil treatments. Biomass turnover was greater compared to the unmanured soil treatments and it decreased with increasing levels of farmyard manure. The average soil respiratory activity increased with increasing levels of farmyard manure, but respiratory activity per unit of biomass C decreased with increasing levels of manure. Enzyme activities were greater in long-term manured soils compared to unmanured soils amended with various levels of manure. There was a significant correlation between biomass C and enzyme activities.     

Effect of Integrated Nutrient Management on Soil Physical Properties and Crop Productivity under a Maize (Zea mays)–Mustard (Brassica campestris) Cropping Sequence in Acidic Soils of Northeast India

A five-year (2001/02–2006/07) field experiment was carried out on acidic clay loam soil classified as Typic Hapludalf with a maize–mustard crop sequence to study the effect of continuous application of nitrogen, phosphorus, and potassium (NPK) fertilizers alone and in combination with lime, farmyard manure (FYM), and biofertilizers on soil physical properties, soil organic carbon (SOC), soil microbial biomass carbon (SMBC), and crop yields on the hilly ecosystem of Meghalaya. Significant improvement in the soil physical conditions of the soil was observed under integrated application of organic manure and inorganic fertilizers. Addition of NPK fertilizers along with organic manure, lime, and biofertilizers increased soil organic carbon (SOC) content, aggregate stability, moisture-retention capacity, and infiltration rate of the soil while reducing bulk density. The SOC content under the treatment of 100% NPK + lime + biofertilizer + FYM was significantly greater (68.58%) than in control plots. Maize and mustard crop yields also significantly increased (4.73- and 21.09-folds, respectively) with continuous application of balanced inorganic (100% NPK) + lime + biofertilizer + FYM as compared to the control plots. However, crop yields drastically reduced under application of integrated nutrients without FYM as compared to the treatment with FYM application. Thus, the results suggest that integrated use of a balanced inorganic fertilizer in combination with lime and organic manure sustains a soil physical environment that is better for achieving higher crop productivity under intensive cropping systems in the hilly ecosystem of northeastern India.     

Impact of organic manures with and without mineral fertilizers on soil chemical and biological properties under tropical conditions

Soils receiving organic manures with and without chemical fertilizers for the last 7 yr with pearlmillet–wheat cropping sequence were compared for soil chemical and biological properties. The application of farmyard manure, poultry manure, and sugarcane filter cake alone or in combination with chemical fertilizers improved the soil organic C, total N, P, and K status. The increase in soil microbial‐biomass C and N was observed in soils receiving organic manures only or with the combined application of organic manures and chemical fertilizers compared to soils receiving chemical fertilizers only. Basal and glucose‐induced respiration, potentially mineralizable N, and arginine ammonification were higher in soils amended with organic manures with or without chemical fertilizers, indicating that more active microflora is associated with organic and integrated system using organic manures and chemical fertilizers together which is important for nutrient cycling.     

Effects of different potassium fertilizers suitable for use in organic farming systems on grass/clover yields and nutrient offtakes and interactions with nitrogen supply

Abstract. In organic farming systems, fertilizing materials can be used when potassium (K) deficiency is shown, but such systems are dominantly nitrogen (N) limited and this is likely to affect crop utilization of K. The supply of K to grass/clover from a range of mineral and organically based K fertilizers and its interaction with N supply were studied in a greenhouse experiment. Sequential plant cuts were taken for yield and nutrient content determinations in crop and soil. Crop yields were limited by N: where N supply was increased either through the mineralization of N from organic materials (rapemeal, farmyard manure) or inorganic fertilizer, plant yields increased significantly. Grass/clover responded better to additional K where sufficient N was available. However, yield responses to K were generally small, even in the presence of adequate N. Of the different fertilizers, kali and MSL-K increased yields above those of the control by less than 5%, sylvinite, DKSI and farmyard manure by 10–20%, and rapemeal and potassium sulphate by more than 25%. In all treatments, K offtakes in the grass/clover were considerably greater than fertilizer K inputs. The grass/clover showed an increased uptake of Na where insufficient K was available. However, the Mg content of the grass/clover was not adversely affected by K fertilizer application. Organic farmers need to consider the soil K status, the rotational nutrient budget, the supply of all nutrients in fertilizing materials and nutrient interactions to achieve effective K management in organic farming systems.     

The influence of mineral and organic fertilisers on the growth of the endogeic earthworm Octolasion tyrtaeum (Savigny)

Endogeic earthworms play an important role in mobilisation and stabilisation of carbon and nitrogen in forest and arable soils. Soil organic matter is the major food resource for endogeic earthworms, but little is known about the size and origin of the organic matter pool on which the earthworms actually live. We measured changes in body mass of juvenile endogeic earthworms, Octolasion tyrtaeum (Savigny), in soils with different C and N contents resulting from different fertiliser treatments. The soil was taken from a long-term experiment (Statischer Düngungsversuch, Bad Lauchstädt, Germany). The treatments included (1) non-fertilised soil, (2) NPK fertilised soil, (3) farmyard manure fertilised soil and (4) NPK + farmyard manure fertilised soil. The soil was incubated in microcosms with and without one juvenile O. tyrtaeum for 80 days.Earthworm biomass decreased in non-fertilised soil by 48.6%, in NPK soil by 9.4%, but increased in farmyard manure soil by 19.7% and 42.8% (soil with additional NPK application). In farmyard manure treatments the biomass of bigger individuals decreased, but in smaller individuals it increased. In NPK fertilised soil without farmyard manure only small O. tyrtaeum increased in body mass, whereas in the non-fertilised soil all individuals decreased in body mass. Generally, soil respiration correlated positively with soil carbon content. Earthworms significantly increased soil respiration and nitrogen leaching and this was most pronounced in farmyard manure treatments. Microbial activity was generally higher in farmyard manure soil indicating that farmyard manure increases labile organic matter pools in soil. Also, biomass of earthworms and microorganisms was increased in farmyard manure soil. The presence of earthworms reduced microbial biomass, suggesting that earthworms feed on microorganisms or/and that earthworms and soil microorganisms competed for similar organic matter pools in soil. The results demonstrate that NPK fertilisation only is insufficient to sustain O. tyrtaeum, whereas long-term fertilisation with farmyard manure enables survival of endogeic species due to an increased pool of utilisable soil organic matter in arable soil.     

Soil microbial response to tillage systems and fertilization in a sunflower rhizosphere

Tillage systems and fertilization have important effects on soil microorganism activity. Information regarding the simultaneous evaluation of long-term tillage and fertilization on soil microbial traits in sunflower fields is not available. Therefore, this study was conducted to determine the best tillage and fertilization system for soil microbial parameters. The experimental design was a split plot based on a randomized complete block design with three replications. Main plots consisted of the long-term tillage systems (1999–2011) including: no tillage (NT), minimum tillage (MT) and conventional tillage (CT). Six methods of fertilization, including farmyard manure (N1), compost (N2), chemical fertilizers (N3), farmyard manure + compost (N4); farmyard manure + compost + chemical fertilizers (N5), and control (N6) were arranged in subplots. Results showed that the highest amount of microbial biomass was observed in treatment NTN4. The highest and lowest values of enzyme activities (acid, alkaline phosphatase, urease, dehydrogenase and protease) were found in organic fertilizers + NT and chemical fertilizers + CT plots, respectively. Highest basal and induced respiration values were found for NTN4 treatment. Correlation coefficients between enzyme activity, respiration and microbial biomass carbon were significant.     

Combined effect of fertilizer and herbicide applications on the abundance, community structure and performance of the soil methanotrophic community

The use of agrochemicals, such as mineral fertilizers and herbicides in agricultural systems, may affect the potential of soils to act as a sink for methane. Typically, the effect of each agrochemical on soil methane oxidation is investigated separately whereas in the field these agrochemicals are used together to form one comprehensive land management system. Here we report the results of field experiments that assessed the combined effect of multiple fertilizer and herbicide (nicosulfuron, dimethenamide and atrazine) applications on the soil methanotrophic community. Soils treated with organic fertilizer had three times higher methane oxidation rates compared to soils receiving mineral fertilizers. These higher oxidation rates were positively reflected in a significantly enhanced abundance of methanotrophs for the organic fertilized soils. In contrast, herbicide application did not alter significantly the soil methane oxidation rate or the methane-oxidizing population abundance. Subsequently, the methanotrophic community structure was analyzed with group-specific DGGE of 16S rRNA genes. Cluster analysis of the methanotrophic patterns clearly separated the mineral from organically fertilized soils. Less pronounced clustering differentiated between chemical and manual weed control. Furthermore, cluster analysis of the methanotrophic community revealed that soil type was the primary determinant of the community structure. Our results indicate that fertilizer type had the greatest influence on methane oxidizer activity and abundance. Soil type had the most pronounced effect on the microbial community structure.     

华北地区有机种植和常规种植模式下土壤重金属含量及污染评价

为探讨有机种植与常规种植两种不同种植方式对土壤重金属含量和污染特性的影响,本文在华北5个地区选取典型的有机蔬菜和有机小麦种植基地及附近相似条件的常规种植地块,比较了土壤中Cu、Zn、Pb、Cr、Cd、As共6种重金属含量的差异,并采用不同评价方法对不同种植方式下土壤中重金属的污染程度进行了评价。结果表明:与常规种植相比,有机种植减轻了土壤酸化和盐渍化,提高了土壤有机质含量和阳离子交换量,在一定程度上有利于降低土壤中重金属的生物有效性。与土壤背景值相比,所有调查地区的土壤重金属均有不同程度的增加和积累。与常规种植相比,有机种植模式能有效降低土壤中Cd、Cr含量,有机小麦种植地块因长期施用大量有机肥导致土壤中Cu、Zn、As大量富集;而常规温室菜田同时施用大量的有机肥、化肥及农药,土壤中Cu、Zn、As富集的风险比有机种植模式高;露天蔬菜有机种植地块土壤中Cu、Zn、As含量与常规地块差异不明显。综合污染指数评价结果显示,调查地区土壤均属于轻污染程度,主要贡献因子为Cd、Cu、Zn,有机种植降低了土壤中重金属的综合污染水平;地累积指数法评价结果表明,调查地区处于无污染到中等污染水平,最明显的污染元素是Cd,有机种植降低了土壤中重金属污染的程度和风险;潜在生态危害指数评价结果表明,所调查地块存在轻微潜在生态风险,其中产生较大生态危害的是Cd,表现出轻微生态危害程度。本研究表明,有机种植减轻了土壤中重金属综合污染水平和污染风险,并减轻了土壤重金属的潜在生态危害。     

Selected Soil Enzyme Activities,Soil Microbial Biomass Carbon,and Root Yield as Influenced by Organic Production Systems in Sweet Potato

A field experiment was conducted on Typic Rhedustalfs to determine the effects of various organic production systems. Results revealed that the soil microbial biomass carbon (SMBC) content was greatest with the application of 100% N through farmyard manure. The ratio index value of biofertilizer along with 50% N through any one of the organic sources were greater than 100% N through green leaf manure?/?vermicompost, integrated use of manure and fertilizer (conventional production system), and control (traditional system of production). Soil enzymes varied with the production systems. The urease, phosphatase, and β-glucosidase activities were more with greater nitrogen, phosphorus, and organic-matter treatments, respectively. The SMBC, soil enzymes, and microbial activity were very responsive to organic production systems, but their levels and activities were not reflected in sweet potato root yield.     

Soil biological quality of grassland fertilized with adjusted cattle manure slurries in comparison with organic and inorganic fertilizers

We studied the effect of five fertilizers (including two adjusted manure slurries) and an untreated control on soil biota and explored the effect on the ecosystem services they provided. Our results suggest that the available N (NO₃⁻ and NH₄⁺) in the soil plays a central role in the effect of fertilizers on nematodes and microorganisms. Microorganisms are affected directly through nutrient availability and indirectly through grass root mass. Nematodes are affected indirectly through microbial biomass and grass root mass. A lower amount of available N in the treatment with inorganic fertilizer was linked to a higher root mass and a higher abundance and proportion of herbivorous nematodes. A higher amount of available N in the organic fertilizer treatments resulted in a twofold higher bacterial activity (measured as bacterial growth rate, viz. thymidine incorporation), a higher proportion of bacterivorous nematodes, a 30% higher potential N mineralization (aerobic incubation), and 25–50% more potentially mineralizable N (anaerobic incubation). Compared to inorganic fertilizer, organic fertilization increased the C total, the N total, the activity of decomposers, and the supply of nutrients via the soil food web. Within the group of organic fertilizers, there was no significant difference in C total, abundances of soil biota, and the potential N mineralization rate. There were no indications that farmyard manure or the adjusted manure slurries provided the ecosystem service “supply of nutrients” better than normal manure slurry. Normal manure slurry provided the highest bacterial activity and the highest amount of mineralizable N and it was the only fertilizer resulting in a positive trend in grass yield over the years 2000–2005. The number of earthworm burrows was higher in the treatments with organic fertilizers compared to the one with the inorganic fertilizer, which suggests that organic fertilizers stimulate the ecosystem service of water regulation more than inorganic fertilizer. The trend towards higher epigeic earthworm numbers with application of farmyard manure and one of the adjusted manure slurries, combined with the negative relation between epigeic earthworms and bulk density and a significantly lower penetration resistance in the same fertilizer types, is preliminary evidence that these two organic fertilizer types contribute more to the service of soil structure maintenance than inorganic fertilizer.     

Influence of long-term fertilization with farmyard manure on soil organic matter: Characteristics of particle-size fractions

Summary The influence of more than 100 years of fertilization with farmyard manure on soil organic matter in comparison to unfertilized soil was studied in particle-size fractions using elemental (C and N) analyses and pyrolysis-field ionization mass spectrometry. Distinct differences in C and N concentrations and distribution and in the quality of organic matter between the size fractions and the fertilization treatments were observed. Clay-associated C and N were relatively higher in the unfertilized treatment, whereas the application of farmyard manure preferentially increased soil organic matter associated with the fine and medium silt fractions. Pyrolysis-field ionization mass spectrometry of soil fractions <20 m showed increasing values for lignin monomers and dimers and fatty acids with larger equivalent diameters, whereas the proportion of N compounds, mono- and polysaccharides and phenolics decreased in the larger size fractions. Sand fractions were particularly rich in lignin fragments, mono- and polysaccharides, and alkanes/alkenes. These relationships seemed to be independent of management practices. In the same size fractions of the different treatments, however, a higher relative abundance of N-compounds, mono- and polysaccharides, phenolics, lignin monomers, and alkanes/alkenes was observed in the unfertilized variant. Lignin dimers and fatty acids were more abundant in the farmyard manure treatment. Both trends together imply that soil enrichment in organic matter due to the application of farmyard manure largely reflects an increase in lignin building blocks and partly reflects an increase in lipids such as fatty acids in the silt fractions. Therefore these constituents are of particular importance in assessing the positive effects of farmyard manure on soil fertility.     

长期有机–无机肥配施对农田杂草土壤种子库的影响

为揭示长期有机-无机肥配施处理下农田杂草土壤种子库的特征变化规律,本研究通过田间长期定位施肥模式试验,运用群落生态学方法研究了小麦-大豆轮作制度下大豆种植季7种施肥处理区杂草土壤种子库的结构及其生物多样性特征。结果表明,土壤样品中共检出杂草种子16种,隶属于10科; 土壤种子库总密度分布在15995~106300 grain/m2范围。长期有机-无机肥配施处理区的杂草土壤种子库优势物种组成较为简单,优势种为12种,配施麦秸处理区主要以栗米草为主,配施粪肥处理区主要以水苋菜为主; 土壤种子库的密度显著降低至15995~41900 grain/m2范围; 物种丰富度降低至7.67~9.33范围,并且将物种多样性和均匀度指数维持在休闲与纯化肥处理区之间（1.5~2.0和0.6~0.8）。长期配施麦秸、 粪肥均显著影响土壤杂草土壤种子库的结构特征,且麦秸与粪肥品种间差异的影响大于麦秸施用量差异的影响。因此,本研究认为有机-无机肥配施既有利于作物的优质高产,也可以通过调整有机肥种类以及与施用量来调控杂草土壤种子库,实现经济效益和生态效益的双赢。     

Effects of Long-term Organic and Mineral N-fertilisation on Soil Microarthropods in Berlin (Germany), Madrid (Spain) and Tartu (Estonia)

Soil micro-arthropods play an important role in the nutrient cycle of agro-ecosystems and are considered to have a strong impact on microbial activity. The occurance of soil microarthropods was investigated in the International Organic Long-Term Field Experiment (IOSDV). The investigation took place in the experimental fields of Berlin/Germany, Madrid/Spain and Tartu/Estonia. Field plots "without organic fertisation", "farmyard manure" and "straw-beet-leaves-green manure" without mineral N-fertilisation and with 120kg/ha mineral N-fertilisation respectively have been investigated. Data shows that the effects of organic manure and mineral N-fertilisation are considerably influenced by specific site characteristics. The highest abundances were found in the experimental field of Madrid. In the two nothern sites soil microarthropods were found only in very low quantities. Data indicates that not only organic manure but also mineral N-fertilisation may influence the abundance of soil micro-arthropods positively.     

Long-term effects of organic farming on fungal and bacterial residues in relation to microbial energy metabolism

Samples from the bio-dynamic, bio-organic, and conventional trial, Therwil, Switzerland, were analyzed with the aim of determining the effects of organic land use management on the energy metabolism of the soil microbial biomass and on the fraction of microbial residues. The contents of adenylates, adenosine triphosphate (ATP), glucosamine, muramic acid, and galactosamine were significantly largest in the biodynamic organic farming (BYODIN) treatment and significantly lowest in the conventional farming treatment with inorganic fertilization (CONMIN). In contrast, the ergosterol-to-ATP ratio and fungal C-to-bacterial C ratios were significantly lowest in the BYODIN treatment and significantly largest in the CONMIN treatment. No clear treatment effects were observed for the ergosterol content and the adenylate energy charge (AEC), the ATP-to-microbial biomass C ratio and the ergosterol-to-fungal C ratio. Ergosterol, an indicator for saprotrophic fungal biomass, and fungal residues were significantly correlated. The microbial biomass carbon-to-nitrogen ratio showed a negative relationship with the AEC and strong positive relationships with the ratios ergosterol-to-microbial biomass C, ergosterol-to-ATP and fungal C-to-bacterial C. In conclusion, the long-term application of farmyard manure in combination with organic farming practices led to an increased accumulation of bacterial residues.     

长期施用有机肥对瘠薄红壤有效碳库及碳库管理指数的影响

主要分析了长期施用有机肥对瘠薄红壤有效碳库(微生物量碳,易氧化碳,矿化碳)及碳库管理指数(CPMI)的影响.结果表明:长期施用有机肥对土壤有效碳库和碳素有效率有很大影响,绿肥,稻草秸秆肥和厩肥处理的土壤有机碳,微生物量碳、易氧化碳、矿化碳的数量、碳素有效率明显高于对照处理的土壤。施肥对全碳、矿化碳的影响为:厩肥>绿肥>秸秆稻草肥>本田还田>对照,对微生物量碳的影响为:绿肥>厩肥>稻草秸秆肥>本田还田>对照,对活性碳(CA)、CPMI,碳素有效率A、B、C的影响为:绿肥>稻草秸秆肥>厩肥>本田还田>对照。在提高CA、CPMI方面,绿肥和稻草秸秆肥优于厩肥。相关分析表明:土壤有效碳库和碳素有效率与土壤化学性质相关或极相关,CPMI与土壤养分因子相关或极相关,反映了农业生产措施对土壤碳库的影响,可以运用CPMI来评估土壤碳库的变化。     

Long-Term Effect of Fertilizers and Amendments on Different Fractions of Organic Matter in an Acid Alfisol

The effect of fertilizers and amendments on organic matter dynamics in an acid Alfisol was studied in a long-term field experiment initiated during 1972 at experimental farm of Department of Soil Science, CSK HPKV, Palampur (India). Continuous application of chemical fertilizers either alone or in combination with farmyard manure (FYM) or lime for 42 years significantly influenced water-soluble organic carbon (WS-OC), water-soluble carbohydrate (WS-CHO), soil microbial biomass carbon, soil microbial biomass nitrogen, soil microbial biomass phosphorus, soil microbial biomass sulfur, humic acid (HA), and fulvic acid (FA). Continuous cropping without fertilization resulted in depletion to the order of 17, 21, 24, 23, 22, 26, 12, and 18% in WS-OC, WS-CHO, microbial biomass carbon, microbial biomass nitrogen, microbial biomass phosphorus, microbial biomass sulfur, HA, and FA, respectively. Different fractions of soil organic matter were found to be positively and significantly correlated with grain and straw/stover yield of wheat and maize crops.