长期施肥对黑土有机质及其组成的影响

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有机质的影响.结果表明,长期施用不同肥料对土壤有机质含量的影响有较大差异,有机无机肥配合处理＞有机肥处理＞无机肥处理＞无肥处理.长期施肥对深层土壤有机质含量也有影响,施用有机肥作用尤其明显,并随着土层的加深施肥对土壤有机质含量的影响呈下降趋势.施用有机肥对有机质不同密度组分影响很大,对有机质含量增加最有效,而施用无机肥则有机质含量有所降低.     

Long‐term effects of cropped vs. fallow and fertilizer amendments on soil organic matter I. Organic carbon

A long‐term field experiment, conducted since 1962 in Gumpenstein (Austria) on a Dystric Cambisol, was used for the present investigation. We combined a physical fractionation procedure with the determination of natural abundance of ¹³C and FT‐IR spectroscopy to study the influence of fertilizer amendments (organic manure and mineral fertilizers) and management practices (fallow vs. cropped) on changes in organic carbon (OC) associated with different particle‐size fractions. The OC content in bulk soil decreased or was not affected by slurry+straw, PK, and NPK treatments in both fallow and cropped plots after 28 and 38 yr of treatment. However, OC in plots receiving organic manures increased depending on the quality of the organic manures applied. The ranking among the different treatments under both fallow and cropped plots was: animal manure (liquid) > animal manure (solid) > cattle slurry = slurry+straw = PK = NPK. Results showed that the two types of management practices, fallow (non‐tilled) vs. cropped (tilled) had effects on OC concentrations. Comparing the OC contribution of particle‐size fractions to the total OC amount revealed the following ranking: silt > clay > fine sand > coarse sand except in the plots receiving solid or liquid animal manure. Size fractions within treatments showed larger variations of ¹³C abundances than bulk samples between treatments. The natural abundances of ¹³C increased especially in cropped (and tilled) plots. It was shown by cluster analysis that FT‐IR spectra differentiated between the different treatments originating from different land management practices. The present study revealed that below‐ground C deposition by agricultural plants can hardly compensate the C losses due to tillage.     

Improving minimum detectable differences in the assessment of soil organic matter change in short‐term field experiments

The demand for information on cropping system impact on soil organic matter (SOM) calls for efforts to improve the utilization of short‐term field experiments (e.g., to evaluate the parameterization of cropping systems in models). Those approaches have coped with the problem of determining small SOM changes within a large background mass. Thus, objectives of this survey are (1) the improvement of the minimum detectable difference (MDD) in SOM in the hudycrop short‐term field experiment by methods of sampling design and data treatment, (2) the verification to what extend the hudycrop short‐term field experiment allows for the determination of management induced effects on SOM, and (3) the investigation to what extent the obtained results may be suitable to evaluate the parameterization of a SOM balance model. The design of the hudycrop is suitable for excluding outliers plotwise. The estimation of plot means can be improved by the sampling design. Instead of determining a single plot mean in a mixed sampling procedure, the design provides multiple values for each plot, allowing for the identification of extreme values before calculating plot means. In consequence, minimum detectable differences decrease by a factor of 0.53 for soil organic C (SOC) and 0.63 for soil total N (STN) masses, allowing for detection of changes in the magnitude of 3.7 and 2.6% of background SOC and STN levels, respectively. Differences between treatments, however, are significant with corrected values (after outlier exclusion) for the crop production systems with the highest impact (potatoes and mulched red clover). Determining outliers based on Student's t‐test gives the lowest MDD and is therefore considered to be the most suitable method in this case. Correlations between apparent changes and SOM balances according to the HU‐MOD–2 model, used in this survey, indicate that the experimental design, in principal, is suitable for the evaluation of the parameterization of crop production systems in models. Still, an improved precision in SOM change detection is necessary. Reasonable options for that purpose are discussed in the paper.     

Contribution of organic amendments to soil organic matter detected by thermogravimetry

Sustainable soil management requires reliable and accurate monitoring of changes in soil organic matter (SOM). However, despite the development of improved analytical techniques during the last decades, there are still limits in the detection of small changes in soil organic carbon content and SOM composition. This study focused on the detection of such changes under laboratory conditions by adding different organic amendments to soils. The model experiments consisted of artificially mixing soil samples from non‐fertilized plots of three German long‐term agricultural experiments in Bad Lauchstädt (silty loam), Grossbeeren (silty sand), and Müncheberg (loamy sand) with straw, farmyard manure, sheep faeces, and charcoal in quantities from 3 to 180 t ha^?1 each. In these mixtures we determined the organic carbon contents by elemental analysis and by thermal mass losses (TML) determined by thermogravimetry. The results confirmed the higher reliability of elemental analysis compared to TML for organic carbon content determination. The sensitivity of both methods was not sufficient to detect the changes in organic carbon content caused by small quantities of organic amendments (3 t ha^?1 or 0.1–0.4 g C kg^?1 soil). In the case of elemental analysis, the detectability of changes in carbon content increased with quantities of added amendments, but the method could not distinguish different types of organic amendments. On the contrary, the based on analysis of degradation temperatures, the TML allowed this discrimination together with their quantitative analysis. For example, added charcoal was not visible in TML from 320 to 330°C, which is used for carbon content determination. However, increasing quantities of charcoal were reflected in a higher TML around 520°C. Furthermore, differences between measured (with TML_110–550) and predicted mass loss on ignition using both organic carbon (with TML₃₃₀) and clay contents (with TML₁₄₀) were confirmed as a suitable indicator for detection of organic amendments in different types of soils. We conclude that thermogravimetry enables the sensitive detection of organic fertilizers and organic amendments in soils under arable land use.     

Assessing the impact of interfering organic matter on soil metaproteomic workflow

Soil organic matter (SOM) is biologically, chemically, and physically complex. As a major store of nutrients within the soil, it plays an important role in nutrient provision to plants. An enhanced understanding of SOM utilisation processes could underpin better fertiliser management for plant growth, with reduced environmental losses. Metaproteomics can allow the characterisation of protein profiles and could help gain insights into SOM microbial decomposition mechanisms. Here, we applied three different extraction methods to two soil types to recover SOM with different characteristics. Specifically, water-extractable organic matter, mineral-associated organic matter and protein-bound organic matter were targeted with the aim to investigate the metaproteome enriched in those extractions. As a proof-of-concept, replicated extracts from one soil were further analysed for peptide identification using liquid chromatography followed by tandem mass spectrometry. We employed a framework for mining mass spectra for both peptide assignment and fragmentation pattern characterisation. Different extracts were found to exhibit contrasting total protein and humic substance content for the two soils investigated. Overall, water extracts displayed the lowest humic substance content (in both soils) and the highest number of peptide identifications (in the soil investigated) with the most frequent peptide hits associated with diverse substrate/ligand binding proteins of Proteobacteria and derived taxa. Our framework also highlighted a strong peptidic signal in unassigned and unmatched spectra, information that is currently not captured by the pipelines employed in this study. Taken together, this work points to specific areas for optimisation in chromatography and mass spectrometry to adequately characterise SOM-associated metaproteomes.     

Long‐term fertilization impacts on corn yields and soil organic matter on a clay‐loam soil in Northeast China

A long‐term fertilization experiment with monoculture corn (Zea mays L.) was established in 1980 on a clay‐loam soil (Black Soil in Chinese Soil Classification and Typic Halpudoll in USDA Soil Taxonomy) at Gongzhuling, Jilin Province, China. The experiment aimed to study the sustainability of grain‐corn production on this soil type with eight different nitrogen (N)‐, phosphorus (P)‐, and potassium (K)–mineral fertilizer combinations and three levels (0, 30, and 60 Mg ha^–1 y^–1) of farmyard manure (FYM). On average, FYM additions produced higher grain yields (7.78 and 8.03 Mg ha^–1) compared to the FYM0 (no farmyard application) treatments (5.67 Mg ha^–1). The application of N fertilizer (solely or in various combinations with P and K) in the FYM0 treatment resulted in substantial grain‐yield increases compared to the FYM0 control treatment (3.56 Mg ha^–1). However, the use of NP or NK did not yield in any significant additional effect on the corn yield compared to the use of N alone. The treatments involving P, K, and PK fertilizers resulted in an average 24% increase in yield over the FYM0 control. Over all FYM treatments, the effect of fertilization on corn yield was NPK > NP = NK = N > PK = P > K = control. Farmyard‐manure additions for 25 y increased soil organic‐matter (SOM) content by 3.8 g kg^–1 (13.6%) in the FYM1 treatments and by 7.8 g kg^–1 (27.8%) in the FYM2 treatments, compared to a 3.2 g kg^–1 decrease (11.4%) in the FYM0 treatments. Overall, the results suggest that mineral fertilizers can maintain high yields, but a combination of mineral fertilizers plus farmyard manure are needed to enhance soil organic‐matter levels in this soil type.     

Long‐term effects of manure and fertilization on soil organic matter and quality parameters of a calcareous soil in NW China

Long‐term applications of inorganic fertilizers and farmyard manure influence organic matter as well as other soil‐quality parameters, but the magnitude of change depends on soil‐climatic conditions. Effects of 22 annual applications (1982–2003) of N, P, and K inorganic fertilizers and farmyard manure (M) on total organic carbon (TOC) and nitrogen (TON), light‐fraction organic C (LFOC) and N (LFON), microbial‐biomass C (MB‐C) and N (MB‐N), total and extractable P, total and exchangeable K, and pH in 0–20 cm soil, nitrate‐N (NO ‐N) in 0–210 cm soil, and N, P, and K balance sheets were determined using a field experiment established in 1982 on a calcareous desert soil (Orthic Anthrosol) at Zhangye, Gansu, China. A rotation of irrigated wheat (Triticum aestivum L.)‐wheat‐corn (Zea mays L.) was used to compare the control, N, NP, NPK, M, MN, MNP, and MNPK treatments. Annual additions of inorganic fertilizers for 22 y increased mass of LFON, MB‐N, total P, extractable P, and exchangeable K in topsoil. This effect was generally enhanced with manure application. Application of manure also increased mass of TOC and MB‐C in soil, and tended to increase LFOC, TON, and MB‐N. There was no noticeable effect of fertilizer and manure application on soil pH. There was a close relationship between some soil‐quality parameters and the amount of C or N in straw that was returned to the soil. The N fertilizer alone resulted in accumulation of large amounts of NO ‐N at the 0–210 cm soil depth, accounting for 6% of the total applied N, but had the lowest recovery of applied N in the crop (34%). Manure alone resulted in higher NO ‐N in the soil profile compared with the control, and the MN treatment had the highest amount of NO ‐N in the soil profile. Application of N in combination with P and/or K fertilizers in both manured and unmanured treatments usually reduced NO ‐N accumulation in the soil profile compared with N alone and increased the N recovery in the crop as much as 66%. The N that was unaccounted for, as a percentage of applied N, was highest in the N‐alone treatment (60%) and lowest in the NPK treatment (30%). In the manure + chemical fertilizer treatments, the unaccounted N ranged from 35% to 43%. Long‐term P fertilization resulted in accumulation of extractable P in the surface soil. Compared to the control, the amount of P in soil‐plant system was surplus in plots that received P as fertilizer and/or manure, and the unaccounted P as percentage of applied P ranged from 64% to 80%. In the no‐manure plots, the unaccounted P decreased from 72% in NP to 64% in NPK treatment from increased P uptake due to balanced fertilization. Compared to the control, the amount of K in soil‐plant system was deficit in NPK treatment, i.e., the recovery of K in soil + plant was more than the amount of applied K. In manure treatments, the recovery of applied K in crop increased from 26% in M to 61% in MNPK treatment, but the unaccounted K decreased from 72% in M to 37% in MNPK treatment. The findings indicated that integrated application of N, P, and K fertilizers and manure is an important strategy to maintain or increase soil organic C and N, improve soil fertility, maintain nutrients balance, and minimize damage to the environment, while also improving crop yield.     

Long‐term effects of cropped vs. fallow and fertilizer amendments on soil organic matter II. Nitrogen

The present study evaluated the effect of fertilizer amendments (organic manure and mineral fertilizers), management practices (fallow and untilled vs. cropped and tilled) on changes of N in bulk soil and N associated with different particle‐size fractions. The long‐term field experiment was conducted since 1962 in Gumpenstein, Austria, on a Dystric Cambisol. The N content of the topsoils changed distinctively during 28 and 38 yr of treatments under both fallow and cropped management practices. Highest increase in total N content was found in animal‐manure (liquid)‐treated plots. The remaining ranking was: animal manure (solid) > cattle slurry > half cattle slurry + straw = PK = NPK. Quite short N‐half‐life values of around 2 yr were found for the cattle‐slurry application, while animal manure exhibited longer N‐half‐lives of around 8 yr. Crop removal of N and mineralization losses in cropped plots obviously were higher than N losses from the bare soil plots lacking a plant cover to keep N in the system. This was confirmed by a consistent shift in the natural ¹⁵N abundances. Comparing the mean N contribution of particle‐size fractions to the total N amounts revealed the following ranking after 28 and 38 yr of different treatments: silt > clay > fine sand > coarse sand, with small exceptions. Particle‐size separates showed more significant responses to changes in the N dynamics of the system due to the various treatments than the bulk soil and can be regarded as the better indicators in this respect.     

Near‐infrared spectroscopy can predict the composition of organic matter in soil and litter

The usefulness and limitations of near‐infrared reflectance spectroscopy (NIRS) for the assessment of several soil characteristics are still not sufficiently explored. The objective of this study was to evaluate the ability of visible and near‐infrared reflectance (VIS‐NIR) spectroscopy to predict the composition of organic matter in soils and litter. Reflectance spectra of the VIS‐NIR region (400–2500 nm) were recorded for 56 soil and litter samples from agricultural and forest sites. Spectra were used to predict general and biological characteristics of the samples as well as the C composition which was measured by ¹³C‐CPMAS‐NMR spectroscopy. A modified partial least‐square method and cross‐validation were used to develop equations for the different constituents over the whole spectrum (1st to 3rd derivation). Near‐infrared spectroscopy predicted well the C : N ratios, the percentages of O‐alkyl C and alkyl C, the ratio of alkyl C to O‐alkyl C, and the sum of phenolic oxidation products: the ratios of standard deviation of the laboratory results to standard error of cross‐validation (RSC) were greater than 2, the regression coefficients (a) of a linear regression (measured against predicted values) ranged from 0.9 to 1.1, and the correlation coefficients (r) were greater than 0.9. Satisfactorily (0.8 ≤ a ≤ 1.2, r ≥ 0.8, and 1.4 ≤ RSC ≤ 2.0) assessed were the contents of C, N, and production of DOC, the percentages of carbonyl C and aromatic C and the ratio of alkyl C to aromatic C. However, the N‐mineralization rate and the microbial biomass were predicted unsatisfactorily (RSC < 1.4). The good and satisfactory predictions reported above indicate a marked usefulness of NIRS in the assessment of biological and chemical characteristics of soils and litter.     

Managing soil organic matter – implications for soil structure on organic farms

Abstract. This paper reviews current understanding of soil structure, the role of soil organic matter (SOM) in soil structure and evidence for or against better soil physical condition under organic farming. It also includes new data from farm case studies in the UK. Young SOM is especially important for soil structural development, improving ephemeral stability through fungal hyphae, extracellular polysaccharides, etc. Thus, to achieve aggregate stability and the advantages that this conveys, frequent input of fresh organic matter is required. Practices that add organic material are routinely a feature of organically farmed soils and the literature generally shows that, comparing like with like, organic farms had at least as good and sometimes better soil structure than conventionally managed farms. Our case studies confirmed this. In the reviewed papers, SOM was generally larger on the biodynamic/organic farms because of the organic additions and/or leys in the rotation. We can therefore hypothesize that, because it is especially the light fraction of SOM that is involved in soil structural development, soil structure will improve in a soil to which fresh organic residues are added regularly. Thus, we argue it is not the farming system per se that is important in promoting better physical condition, but the amount and quality of organic matter returned to a soil.     

长期定位试验条件下的水稻田土壤有机质含量变化研究

依托湖北武汉、重庆北碚、湖南望城、湖南祁阳、江西南昌、浙江杭州6个水稻土壤肥力长期定位试验历史样品及数据,分析和讨论了土壤有机质含量变化趋势及对施化肥和有机肥的响应差异。施有机肥提升土壤有机质含量显著高于施化肥的效果。施化肥NPK处理,6个试验点土壤有机质含量都呈现提升趋势;但是,有机质平均年增量、有机质累计增量与累计有机肥施用量的比值都是逐年下降的,固定施肥方法提高土壤有机质含量是有限的,最高达到平衡点,施化肥的有机质含量的平衡点低于施有机肥的,土壤有机质含量提升不仅对施有机肥有响应,而且与累积产量也有一定的相关关系。     

Tillage effects on soil aggregation and soil organic carbon profile distribution under Mediterranean semi‐arid conditions

In rainfed semi‐arid agroecosystems, soil organic carbon (SOC) may increase with the adoption of alternative tillage systems (e.g. no‐tillage, NT). This study evaluated the effect of two tillage systems (conventional tillage, CT vs. NT) on total SOC content, SOC concentration, water stable aggregate‐size distribution and aggregate carbon concentration from 0 to 40 cm soil depth. Three tillage experiments were chosen, all located in northeast Spain and using contrasting tillage types but with different lengths of time since their establishment (20, 17, and 1‐yr). In the two fields with mouldboard ploughing as CT, NT sequestered more SOC in the 0–5 cm layer compared with CT. However, despite there being no significant differences, SOC tended to accumulate under CT compared with NT in the 20–30 and 30–40 cm depths in the AG‐17 field with 25–50% higher SOC content in CT compared with NT. Greater amounts of large and small macroaggregates under NT compared with CT were measured at 0–5 cm depth in AG‐17 and at 5–10 cm in both AG‐1 and AG‐17. Differences in macroaggregate C concentration between tillage treatments were only found in the AG‐17 field at the soil surface with 19.5 and 11.6 g C/kg macroaggregates in NT and CT, respectively. After 17 yr of experiment, CT with mouldboard ploughing resulted in a greater total SOC concentration and macroaggregate C concentration below 20 cm depth, but similar macroaggregate content compared with NT. This study emphasizes the need for adopting whole‐soil profile approaches when studying the suitability of NT versus CT for SOC sequestration and CO₂ offsetting.     

Effect of ultrasonic power on soil organic carbon fractions

Ultrasonic dispersion is a prevalent tool for soil fractionation. It is widely ignored that variation in ultrasonic power might lead to significantly different dispersion. We evaluated the effect of power variation with constant energy on the fine fraction mass, its organic C content and quality. All parameters increased significantly with power. The term “stable aggregates” as used in fractionation schemes cannot be defined by ultrasonic energy alone but power needs to be standardized, too.     

Long‐term no‐tillage effects on particulate and mineral‐associated soil organic matter under rainfed Mediterranean conditions

Soil organic carbon (SOC) plays an essential role in the sustainability of natural and agricultural systems. The identification of sensitive SOC fractions can be crucial for an understanding of SOC dynamics and stabilization. The objective of this study was to assess the effect of long‐term no‐tillage (NT) on SOC content and its distribution between particulate organic matter (POM) and mineral‐associated organic matter (Min) fractions in five different cereal production areas of Aragon (north‐east Spain). The study was conducted under on‐farm conditions where pairs of adjacent fields under NT and conventional tillage (CT) were compared. An undisturbed soil nearby under native vegetation (NAT) was included. The results indicate that SOC was significantly affected by tillage in the first 5 cm with the greatest concentrations found in NT (1.5–43% more than in CT). Below 40 cm, SOC under NT decreased (20–40%) to values similar or less than those under CT. However, the stratification ratio (SR) never reached the threshold value of 2. The POM‐C fraction, disproportionate to its small contribution to total SOC (10–30%), was greatly affected by soil management. The pronounced stratification in this fraction (SR>2 in NT) and its usefulness for differentiating the study sites in terms of response to NT make POM‐C a good indicator of changes in soil management under the study conditions. Results from this on‐farm study indicate that NT can be recommended as an alternative strategy to increase organic carbon at the soil surface in the cereal production areas of Aragon and in other analogous areas.     

Soil organic matter composition and soil lightness

Relationships between soil lightness, soil organic matter (SOM) composition, content of organic C, CaCO₃, and texture were studied using 42 top‐soil horizons from different soil types located in southern Germany. SOM composition was determined by CPMAS ¹³C NMR spectroscopy, soil color was measured by diffuse‐reflectance spectrophotometry and given in the CIE L*a*b* color coordination system (Commission Internationale de l'Eclairage, 1978). Multiple‐regression analysis showed, that soil lightness of top‐soil horizons is principally determined by OC concentration, but CaCO₃ and soil texture are also major variables. Soil lightness decreased with increasing OC content. Carbonate content had an important effect on soil lightness even at low concentrations due to its lightening property. Regressions between soil lightness and organic C content were strongly linear, when the soils were differentiated according to texture and CaCO₃ content. The aryl‐C content was the only SOM component which correlated significantly with soil lightness (r_S = –0.87). In the linear regressions carried out on the different soil groups, soil aryl‐C content was a more significant predictor for soil lightness than total OC content.     

Effect of conservation agriculture on stratification of soil organic matter under cereal-based cropping systems

ABSTRACT

Degradation of soil quality caused by conventional tillage practices is a major concern for the sustainability of rice-wheat cropping systems in South Asian region. Therefore, suitable conservation agriculture (CA) practices are required. This study investigates the stratification and storage of soil organic carbon (SOC) and total nitrogen (TN) as affected by eight years of different CA practices in the North-West Indo-Gangetic Plains of India. There were four treatments: (1) conventionally tilled rice-wheat cropping system, (2) reduced-till CA-based rice-wheat-mungbean system, (3) no-till CA-based rice-wheat-mungbean system, and (4) no-till CA-based maize-wheat-mungbean system. The mean stratification ratio (SR) (i.e. a ratio of the concentrations of SOC and TN in the soil surface to those in a deeper layer) of SOC and TN for 0–5:5–10, 10–15, 15–20, 20–25 and 25–30 cm were found higher (> 2) under CA practices compared to intensive tillage-based conventional agricultural practice (< 2). No-till CA-based rice-wheat-mungbean system stored the highest amount of SOC (25.32 Mg ha^?1) whereas reduced till CA-based rice-wheat-mungbean system stored highest amount of TN (3.21 Mg ha^?1) at 0–30 cm soil depth. This study shows that CA stratifies SOC and TN and helps to enhance SOC sequestration and soil quality.     

Trends in grain yields and soil organic C in a long‐term fertilization experiment in the China Loess Plateau

Changes in grain yields and soil organic carbon (SOC) from a 26 y dryland fertilization trial in Pingliang, Gansu, China, were recorded. Cumulative C inputs from straw and root and manure for fertilizer treatments were estimated. Mean wheat (Triticum aestivum L.) yields for the 18 y ranged from 1.72 t ha^–1 for the unfertilized plots (CK) to 4.65 t ha^–1 for the plots that received manure (M) annually with inorganic N and P fertilizers (MNP). Corn (Zea mays L.) yields for the 6 y averaged 2.43 and 5.35 t ha^–1 in the same treatments. Yields declined with year except in the CK for wheat. Wheat yields for N only declined with time by 117.8 kg ha^–1 y^–1 that was the highest decrease among all treatments, and that for NP declined by 84.7 kg ha^–1 y^–1, similar to the declines of 77.4 kg ha^–1 y^–1 for the treatment receiving straw and N annually and P every second year (SNP). Likewise, the corn yields declined highly for all treatments, and the declined amounts ranged from 108 to 258 kg ha^–1 y^–1 which was much higher than in wheat. These declined yields were mostly linked to both gradual dry weather and nutrients depletion of the soil. The N only resulted in both P and K deficiency in the soil, and soil N and K negative balances in the NP and MNP were obvious. Soil organic carbon (SOC) in the 0–20 cm soil layer increased with time except in the CK and N treatments, in which SOC remained almost stable. In the MNP and M treatments, 24.7% and 24.0% of the amount of cumulative C input from organic sources remained in the soil as SOC, but 13.7% of the C input from straw and root in the SNP, suggesting manure is more effective in building soil C than straw. Across the 26 y cropping and fertilization, annual soil‐C sequestration rates ranged from 0.014 t C ha^–1 y^–1 for the CK to 0.372 t C ha^–1 y^–1 for the MNP. We found a strong linear relationship (R² = 0.74, p = 0.025) between SOC sequestration and cumulative C input, with C conversion–to–SOC rate of 16.9%, suggesting these dryland soils have not reached an upper limit of C sequestration.     

长期不同施肥下我国4种典型土壤活性有机碳及碳库管理指数的变化特征

研究长期不同施肥处理对3种旱作土壤(黑土、潮土和红壤)及1种水田土壤(水稻土)活性有机碳含量(LOC)及碳库管理指数(CMI)的影响,为优化施肥管理措施提供科学依据。结果表明:水田土壤总有机碳含量(TOC)和LOC含量高于旱作土壤。单施化肥(NPK),旱作3种土壤TOC、LOC较不施肥对照(CK)显著增加,而水田较CK无显著差异。化肥配施秸秆处理(NPKS),旱作和水田土壤TOC、LOC、活性有机碳占总有机碳的比例(LOC/TOC)及CMI均显著增加,潮土TOC和LOC含量增加最多,增加比例分别为37.6%和66.9%。化肥配施有机肥处理(NPKM),旱作和水田土壤的TOC、LOC、LOC/TOC及CMI均显著增加,其中黑土增加比例最大,分别为90.3%、140.9%、5.1%及277%。旱作和水田土壤的活性有机碳及碳库管理指数均对施肥响应敏感,具有相对一致的响应特征,即长期有机无机肥配施能显著提高土壤活性有机碳含量及碳库管理指数,且效果优于化肥配施秸秆和单施化肥处理。     

Tillage and fertilizing effects on sandy soils. Review and selected results of long‐term experiments at Humboldt‐University Berlin

The Humboldt‐University of Berlin conducts several long‐term field trials designed to assess the effects of tillage methods, crop rotations, organic fertilization, mineral nitrogen, phosphorus, and potassium fertilizers, liming, irrigation, and weather conditions. On silty sand soils shallow ploughing resulted in a distinct accumulation of soil organic matter and phosphorus in the tilled soil layer while potassium and pH values were unaffected. On average shallow ploughing increased yields, with a tendency for higher yields in spring crops and lower yields in winter cereals. Different amounts of organic and mineral fertilizers applied over 30 years resulted in a great differentiation in soil organic matter content. In the following 32 years this variation stayed more or less unchanged, but with an overall reduction in the carbon content. In variants in which phosphate and potassic fertilizers were omitted, 16 kg ha^—1 P and 15 kg ha^—1 K per year were still being mobilized in the soil after 60 years. In treatments with mineral fertilization, the phosphorus is nearly balanced whilst only 60 % of the potassium is withdrawn from the soil. Additional organic fertilizers, given as farm yard manure, led to a nutrient surplus of 19 kg ha^—1 a^—1 P and 99 kg ha^—1 a^—1 K. Omitted liming caused an acidification of the soil to such an extent that crop production became impossible.