Thirteen years of continued application of composted organic wastes in a vineyard modify soil quality characteristics

A solution for environmentally wiser agriculture is the use of composted organic wastes as soil amendments. Just as this alleviates the problem of recycling organic residues, it provides necessary nutrient input for food production. The objective of this work was to study the effect that 13 years of applying three different composted organic wastes or organic amendments have had on soil quality, GHG emissions and the dynamics of its microbial communities 15 days after the annual application. For this purpose, in 1996 a field trial was set up in a Tempranillo vineyard. Since 1998, the applied organic amendments have been as follows: 1. a pelletized organic compost (PEL) made from plant, animal and sewage sludge residues; 2. a compost made from the organic fraction of municipal solid waste (OF-MSW); 3. a compost made of stabilized sheep manure (SMC); 4. a mineral fertilizer (NPK); and 5. an unaltered control. The mean annual doses applied since 1998 have been 3700 kg ha⁻¹ fresh weight (FW) of PEL, 4075 kg ha⁻¹ FW of OF-MSW, 4630 kg ha⁻¹ FW of SMC, and 340 kg ha⁻¹ of NPK treatment. Soil quality was consistently enhanced by amendment application over the 13 years. Total nitrogen was significantly increased in PEL (0.1%), OF-MSW (0.09%) and SMC (0.1%) compared to control (0.06%). Nutrient content was also improved in a similar way, e.g. the most significant increase in P Olsen (80.7 mg kg⁻¹) and K₂O (473.8 mg kg⁻¹) was found on SMC. The overall enzyme activity was also increased 15 days after the annual application and OF-MSW had the highest rate (95.9) compared to control (51.3). This increase in metabolic activity was also recorded in GHG emissions. CO₂ equivalents per hectare were 1745 kg for OF-MSW and it was the only significant difference found. PEL with 1598 kg and SMC with 1591 kg were not different from the Control (1104 kg). Even though GHG emissions in the soil increased because of the application, soil organic matter content increased significantly (at least 35% more in all organic treatments compared to control) and this rise in organic matter was consistent over the years. According to the results, 85% of the sequences corresponded to 5 main phyla: Proteobacteria, Actinobacteria, Bacteroidetes, Acidobacteria and Gemmatimonadetes, with unclassified material making up for 10.9% (average) of the sequences. Bacterial diversity by Shannon and Chao1 indices was not affected 15 days after the application. However, slight changes in the bacterial community were recorded 15 days after application only in OF-MSW treatment. Assessing soil quality using these three factors allows the relevant agronomical capabilities of the soil to be integrated with the potential effect of this practise on global warming.     

半干旱土添加有机改良剂后有机质的化学结构变化

A 9-month incubation experiment using composted and non-composted amendments derived from vine pruning waste and sewage sludge was carried out to study the effects of the nature and stability of organic amendments on the structural composition of organic matter (OM) in a semi-arid soil.The changes of soil OM,both in the whole soil and in the extractable carbon with pyrophosphate,were evaluated by pyrolysis-gas chromatography and chemical analyses.By the end of the experiment,the soils amended with pruning waste exhibited less organic carbon loss than those receiving sewage sludge.The non-composted residues increased the aliphatic-pyrolytic products of the OM,both in the whole soil and also in the pyrophosphate extract,with the products derived from peptides and proteins being significantly higher.After 9 months,in the soils amended with pruning waste the relative abundance of phenolic-pyrolytic products derived from phenolic compounds,lignin and proteins in the whole soil tended to increase more than those in the soils amended with sewage sludge.However,the extractable OM with pyrophosphate in the soils amended with composted residues tended to have higher contents of these phenolic-pyrolytic products than that in non-composted ones.Thus,despite the stability of pruning waste,the composting of this material promoted the incorporation of phenolic compounds to the soil OM.The pyrolytic indices (furfural/pyrrole and aliphatic/aromatic ratios) showed the diminution of aliphatic compounds and the increase of aromatic compounds,indicating the stabilization of the OM in the amended soils after 9 months.In conclusion,the changes of soil OM depend on the nature and stability of the organic amendments,with composted vine pruning waste favouring humification.     

Hydrolase activities, microbial biomass and bacterial community in a soil after long-term amendment with different composts

The use of composts in agricultural soils is a widespread practice and the positive effects on soil and plants are known from numerous studies. However, there have been few attempts to compare the effects of different kinds of composts in one single study. The aim of this paper is to investigate to what extent and to which soil depth four major types of composts would affect the soil and its microbiota.In a crop-rotation field experiment, composts produced from (i) urban organic wastes, (ii) green wastes, (iii) manure and (iv) sewage sludge were applied at a rate equivalent to 175 kg N ha⁻¹ yr⁻¹ for 12 years. General (total organic C (C_org), total N (N_t), microbial biomass C (C_mic), and basal respiration), specific (enzyme activities related to C, N and P cycles), biochemical properties and bacterial genetic diversity (based on DGGE analysis of 16S rDNA) were analyzed at different depths (0-10, 10-20 and 20-30 cm).Compost treatment increased C_org at all depths from 11 g kg⁻¹ for control soil to 16.7 g kg⁻¹ for the case of sewage sludge compost. Total N increased with compost treatment at 0-10 cm and 10-20 cm depths, but not at 20-30 cm. Basal respiration and C_mic declined with depth, and the composts resulted in an increase of C_mic and basal respiration. Enzyme activities were different depend on the enzyme and among compost treatments, but in general, the enzyme activities were higher in the upper layers (0-10 and 10-20 cm) than in the 20-30 cm layer. Diversity of ammonia oxidizers and bacteria was lower in the control than in the compost soils. The type of compost had less influence on the composition of the microbial communities than did soil depth.Some of the properties were sensitive enough to distinguish between different compost, while others were not. This stresses the need of multi-parameter approaches when investigating treatment effects on the soil microbial community. In general, with respect to measures of activity, biomass and community diversity, differences down the soil profile were more pronounced than those due to the compost treatments.     

Changes in soil organic carbon fractions and bacterial community composition under different tillage and organic fertiliser application in a maize−wheat rotation system

ABSTRACT

The objective of this study was to assess the impact of different tillage and organic fertiliser regimes on soil carbon fractions and bacterial community composition within a maize–wheat cropping system. We conducted a six-year experiment on the Huang-Huai-Hai Plain of China. Six treatments were established: deep tillage (DT), shallow tillage (ST), no-tillage (NT), deep tillage with organic fertiliser (DTF), shallow tillage with organic fertiliser (STF), and no-tillage with organic fertiliser (NTF). Results indicated that during the winter wheat growing season, the highest contents of soil organic carbon (SOC) and easily-oxidised organic carbon (EOC) were in the STF treatment. During the summer maizegrowing season, the DTF treatment had the highest SOC and EOC contents. Compared with the other treatments, the NTF treatment had higher Chao1 and Shannon indices for bacteria; however, the relative abundance of Proteobacteria is highest in all treatments. A redundancy analysis (RDA) revealed that bacterial community composition was correlated with variation of the SOC, DOC, EOC, and microbial biomass carbon (MBC). Our results showed that combining the two components of the SOC fractions and bacterial community composition, STF practice in a maize–wheat rotation was a sustainable approach to optimising soil structure and improving soil quality.     

连续五年生物垃圾堆肥施用后地中海蔬菜种植系统中土壤有机碳的变化

Biowaste compost can influence soil organic matter accumulation directly or indirectly. A 5-year experiment was conducted to assess the influence of biowaste compost on the process of soil aggregation and soil organic carbon(SOC) accumulation in a Mediterranean vegetable cropping system. The study involved four treatments: biowaste compost(COM), mineral NPK fertilizers(MIN), biowaste compost with half-dose N fertilizer(COMN), and unfertilized control(CK). The SOC stocks were increased in COM, COMN, and MIN by 20.2, 14.9, and 2.4 Mg ha~(-1)over CK, respectively. The SOC concentration was significantly related to mean weight diameter of aggregates(MWD)(P 0.05, R~2= 0.798 4) when CK was excluded from regression analysis. Compared to CK, COM and COMN increased the SOC amount in macroaggregates( 250 μm) by 2.7 and 0.6 g kg~(-1)soil, respectively, while MIN showed a loss of 0.4g kg~(-1)soil. The SOC amount in free microaggregates(53–250 μm) increased by 0.9, 1.6, and 1.0 g kg~(-1)soil for COM, COMN, and MIN, respectively, while those in the free silt plus clay aggregates( 53 μm) did not vary significantly. However, when separating SOC in particle-size fractions, we found that more stable organic carbon associated with mineral fraction 53 μm(MOM-C) increased significantly by 3.4, 2.2, and 0.7 g kg~(-1)soil for COM, COMN, and MIN, respectively, over CK, while SOC amount in fine particulate organic matter(POM) fraction(53–250 μm) increased only by 0.3 g kg~(-1)soil for both COM and COMN, with no difference in coarse POM 250 μm. Therefore, we consider that biowaste compost could be effective in improving soil structure and long-term C sequestration as more stable MOM-C.     

行间生草对葡萄园土壤肥力和葡萄叶片养分的影响

在赤霞珠葡萄生产园行间播种多年生黑麦草、紫花苜蓿、白三叶草.结果表明与清耕相比,行间生草使土壤全N、全K平均含量升高,但对土壤全P含量影响不大;土壤碱解N、速效P和速效K平均含量均降低,土壤pH值升高.对于土壤中的微量元素,Mn含量升高、Zn含量降低,而且行间生草使叶片N、K、Ca、Mg、Mn、Zn都有升高趋势.豆科植物紫花苜蓿和白三叶草有利于土壤中氮的积累,禾本科多年生黑麦草有利于土壤有机质的提高.     

长期施用有机肥对草甸碱土土壤酶活性及养分特征的影响

依托东北农业大学盐碱土改良长期定位试验站,以松嫩平原草甸碱土为研究对象,探讨不同年限有机培肥措施下草甸碱土酶活性变化趋势、有机质和养分提升状况及其相互关系。结果表明:长期施用有机肥,草甸碱土脲酶、蔗糖酶、磷酸酶活性含量均显著提高,长期施用有机肥对过氧化氢酶活性影响较小。草甸碱土有机质、全氮、全磷及碱解氮、有效磷含量均显著提高,土壤pH值显著降低。施用有机肥5年后,草甸碱土的改良效果显著。经相关分析,土壤脲酶、蔗糖酶、磷酸酶与土壤有机质和养分间呈显著或极显著正相关,过氧化氢酶则无显著相关性。     

Shifts in microbial community and water-extractable organic matter composition with biochar amendment in a temperate forest soil

Biochar amendment in soil has been proposed as a carbon sequestration strategy which may also enhance soil physical and chemical properties such as nutrient and water holding capacity as well as soil fertility and plant productivity. However, biochar may also stimulate microbial activity which may lead to increased soil CO₂ respiration and accelerated soil organic matter (OM) degradation which could partially negate these intended benefits. To investigate short-term soil microbial responses to biochar addition, we conducted a 24 week laboratory incubation study. Biochar produced from the pyrolysis of sugar maple wood at 500 °C was amended at concentrations of 5, 10 and 20 t/ha in a phosphorus-limited forest soil which is under investigation as a site for biochar amendment. The cumulative soil CO₂ respired was higher for biochar-amended samples relative to controls. At 10 and 20 t/ha biochar application rates, the concentration of phospholipid fatty acids (PLFAs) specific to Gram-positive and Gram-negative bacteria as well as actinomycetes were lower than controls for the first 16 weeks, then increased between weeks 16–24, suggesting a gradual microbial adaptation to altered soil conditions. Increases in the ratio of bacteria/fungi and lower ratios of Gram-negative/Gram-positive bacteria suggest a microbial community shift in favour of Gram-positive bacteria. In addition, decreasing ratios of cy17:0/16:1ω7 PLFAs, a proxy used to examine bacterial substrate limitation, suggest that bacteria adapted to the new conditions in biochar-amended soil over time. Concentrations of water-extractable organic matter (WEOM) increased in all samples after 24 weeks and were higher than controls for two of the biochar application rates. Solution-state ¹H NMR analysis of WEOM revealed an increase in microbial-derived short-chain carboxylic acids, lower concentrations of labile carbohydrate and peptide components of soil OM and potential accumulation of more recalcitrant polymethylene carbon during the incubation. Our results collectively suggest that biochar amendment increases the activity of specific microorganisms in soil, leading to increased CO₂ fluxes and degradation of labile soil OM constituents.     

Chemical extractability and availability of heavy metals after seven years application of organic wastes to a citrus soil

Abstract. The chemical extractability of heavy metals introduced into the soil during 7 years application of sewage sludge, composted municipal solid waste and sheep manure, and their availability to citrus plants were studied. The total content of metals in the soil (0-20 cm)was increased by the use of sludges and compost, but only the Ni content in the saturation extracts of soil was significantly increased. Total Cd, Cr, Cu, Ni, Pb, and Zn were sequentially fractionated into water-soluble plus exchangeable, organically bound, carbonate-associated, and residual fractions. Most of the heavy metals were present in carbonate and residual fractions, although substantial amounts of water-soluble plus exchangeable Cd, and organically bound Cu and Ni were found. No significant increases in the metal contents in leaves and orange fruits were observed, with the exception of Pb in leaves. Several statistically significant correlations between metal content in plants, metal content in soil fractions, and chemical characteristics of soil were also found.     

Changes in metabolic and structural diversity of a soil bacterial community in response to cadmium toxicity

Cadmium toxicity reduces the species diversity of soil microbial communities and their ability to metabolize different carbon substrates. However, it is not yet clear whether there is a relationship between loss of species diversity and the metabolic rates at which different substrates are used. In this research, the ability of a soil microbial community to metabolize 31 C substrates was examined using Biolog Ecoplates amended with Cd over a range of concentrations (0, 5, 10, 20, 50 g ml^–1). After 48 h growth, the bacterial communities that were produced on ten of the substrates were characterized in relation to their 16S rDNA profiles by PCR denaturing-gradient gel electrophoresis. Results showed that both the microbial growth rates and the numbers of substrates that were used were reduced with increasing Cd concentration. When examined across all substrates, approximately 30% of the 16S rDNA bands representing different bacterial species were eliminated by 5 g Cd ml^–1. However, there was considerable variation in the bacterial community responses with different C substrates. Both cluster analysis and discriminant analysis indicated that the bacterial community structures could be grouped into sensitive, moderately sensitive, and Cd-resistant communities.     

Effect of organic mulches on soil bacterial communities one year after application

The application of organic mulches as a soil cover is effective in improving the quality of soil. However, very little information is available on the effect of mulches on the soil microbial community. In this study, we investigated the effect of various organic mulches on soil dehydrogenase activity (DHA) and microbial community structures in the top 1 cm and 5 cm below the soil surface 1 year after application of the mulches. DHA was stimulated at both depths in plots mulched with grass clippings (GC), but was not significantly different from the control for the other mulch treatments. Fatty acid methyl ester (FAME) analysis and denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction-amplified 16S rDNA fragments were used to assess changes in the soil microbial community structure. Cluster analysis and principle component analysis of FAME profiles showed that only soil mulched with pine chips distinctively clustered from the other treatments. At the soil surface, bacterial DGGE profiles revealed that distinct shifts in several bacterial populations occurred in soils mulched with GC and eucalyptus yardwaste (EY), while DGGE profiles from soil at the 5 cm depth revealed no distinct changes. Changes in bacterial diversity at the soil surface under different mulches were calculated based on the number of bands in the DGGE profile using the Shannon-Weaver index of diversity ( H). Compared to the control ( H =0.9), the GC- and EY-treated soils showed slightly increased bacterial diversity, with an H of 1.1 and 1.0, respectively. These results indicate that the long-term effect of organic mulches on the soil microbial activity and community structure is highly dependent upon the type of mulch and is mostly exerted in the top few centimeters of the soil profile.     

Persistence of simazine and terbuthylazine in a semiarid soil after organic amendment with urban sewage sludge

The persistence of two herbicides, simazine and terbuthylazine, and appearance of their principal dealkylated chloro-s-triazine metabolites have been studied in agricultural soil after the addition of urban sewage sludge as organic amendment. Both herbicides and metabolites were monitored during long-term laboratory incubation (140 days) and analyzed by gas chromatography with a nitrogen-phosphorus detector (GC-NPD). Residues were confirmed by gas chromatography with a mass selective detector (GC-MSD). A sonication microextraction method was used to extract the compounds. The organic amendments used were urban sewage sludge and the humic fraction of this sludge, to increase the organic matter content of the soil from 1% to 2%. For both compounds, simazine and terbuthylazine, the degradation began earlier in the amended soils. Simazine showed a higher dissipation rate than terbuthylazine, the percentage of the former at the end of the experiment being lower than 2% in all cases, while for terbuthylazine the corresponding percentage ranged from 5% to 46%. Organic amendment, mainly its humic fraction, caused a certain stabilization of terbuthylazine in the soil, but did not greatly influence the residual amount of simazine at the end of the experiment. The periodic aeration of the soil caused a greater degradation in the case of terbuthylazine. Only mono-deethylsimazine and deethylterbuthylazine were isolated from the soil during the time the experiment lasted, while the di-deethylated metabolite of simazine was not found.     

Changes in the chemical composition of soil organic matter after application of compost

Is the composition of soil organic matter changed by adding compost? To find out we incubated biowaste composts with agricultural soils and a humus‐free mineral substrate at 5°C and 14°C for 18 months and examined the products. Organic matter composition was characterized by CuO oxidation of lignin, hydrolysis of cellulosic and non‐cellulosic polysaccharides (CPS and NCPS) and ¹³C cross‐polarization magic angle spinning nuclear magnetic resonance (CPMAS ¹³C‐NMR) spectroscopy. The lignin contents in the compost‐amended soils increased because the composts contained more lignin, which altered little even after prolonged decomposition of the composts in soil. A pronounced decrease in lignin occurred in the soils amended with mature compost only. Polysaccharide C accounted for 14–20% of the organic carbon at the beginning of the experiment for both the compost‐amended soils and the controls. During the incubation, the relative contents of total polysaccharides decreased for 9–20% (controls) and for 20–49% (compost‐amended soils). They contributed preferentially to the decomposition as compared with the bulk soil organic matter, that decreased between < 2% and 20%. In the compost‐amended agricultural soils, cellulosic polysaccharides were decomposed in preference to non‐cellulosic ones. The NMR spectra of the compost‐amended soils had more intense signals of O–alkyl and aromatic C than did those of the controls. Incubation for 18 months resulted mainly in a decline of O–alkyl C for all soils. The composition of the soil organic matter after compost amendment changed mainly by increases in the lignin and aromatic C of the composts, and compost‐derived polysaccharides were mineralized preferentially. The results suggest that decomposition of the added composts in soil is as an ongoing humification process of the composts themselves. The different soil materials affected the changes in soil organic matter composition to only a minor degree.     

Microbial biomass,functional capacity,and community structure after 12 years of soil warming

We examined the effect of chronic soil warming on microbial biomass, functional capacity, and community structure in soil samples collected from the Soil Warming Study located at the Harvard Forest Long-term Ecological Research (LTER) site. Twelve years of chronic soil warming at 5 °C above the ambient temperature resulted in a significant reduction in microbial biomass and the utilization of a suite of C substrates which included amino acids, carbohydrates, and carboxylic acids. Heating significantly reduced the abundance of fungal biomarkers. There was also a shift in the mineral soil microbial community towards gram positive bacteria and actinomycetes.     

长期施用有机肥对红壤旱地土壤线虫群落的影响

基于红壤旱地(玉米)的长期施肥试验,研究长期施用有机肥对土壤线虫分布特征及群落结构的影响。田间试验处理包括:CK(对照)、ON1(低量有机肥)、ON2(高量有机肥)和ON2L(高量改良有机肥)。结果表明,施肥8a后,红壤旱地中共鉴定出15科、29属土壤线虫,包括8属植物寄生线虫、9属食细菌线虫、3属食真菌性线虫和9属捕食杂食性线虫,短体属(Pratylenchus)、小杆属(Rhabditis)和原杆属(Pro-torhabditis)为优势属。不同施肥处理中,土壤线虫总数的大小顺序为ON2>ON1>ON2L>CK。线虫群落生态指数对于施用有机肥有不同的响应:除SI外,其他虫群落生态指数均有显著差异,通过线虫群落结构的变化很好地反映了土壤的肥力变化状况,土壤线虫可以作为施有机肥过程中指示土壤健康质量的一个重要的生物学指标。     

Earthworm activity and soil structure changes due to organic enrichments in vineyard systems

 The effect of organic enrichment on earthworm activity and soil structure was studied in two French vineyards, by comparing control and test plots. In each vineyard the organic matter quantitatively increased the abundance and biomass of the earthworm community. These increases were associated with a higher level of species diversity and a higher evenness corresponding to the development of endogeic community. These earthworm community changes were associated with an increase in granular bioturbated areas and in macroporosity in the top soil layer. The micromorphological approach incorporated an original process of image analysis which appeared to be an appropriate method for characterizing pore morphology in this study. The pores when characterized by their size and shape could be related to ecological groups and growth stages of earthworms. Received: 4 August 1997     

Soil organic carbon and nutrient content in aggregate‐size fractions of a subtropical rice soil under variable tillage

The effects of tillage on soil organic carbon (SOC) and nutrient content of soil aggregates can vary spatially and temporally, and for different soil types and cropping systems. We assessed SOC and nutrient levels within water‐stable aggregates in ridges with no tillage (RNT) and also under conventional tillage (CT) for a subtropical rice soil in order to determine relationships between tillage, cation concentrations and soil organic matter. Surface soil (0–15 cm) was fractionated into aggregate sizes (>4.76 mm, 4.76–2.00 mm, 2.00–1.00 mm, 1.00–0.25 mm, 0.25–0.053 mm, <0.053 mm) under two tillage regimes. Tillage significantly reduced the proportion of macroaggregate fractions (>2.00 mm) and thus aggregate stability was reduced by 35% compared with RNT, indicating that tillage practices led to soil structural change for this subtropical soil. The patterns in SOC, total N, exchangeable Ca²⁺, Mg²⁺ and total exchangeable bases (TEB) were similar between tillage regimes, but concentrations were significantly higher under RNT than CT. This suggests that RNT in subtropical rice soils may be a better way to enhance soil productivity and improve soil C sequestration potential than CT. The highest SOC was in the 1.00–0.25 mm fraction (35.7 and 30.4 mg/kg for RNT and CT, respectively), while the lowest SOC was in microaggregate (<0.025 mm) and silt + clay (<0.053 mm) fractions (19.5 and 15.7 mg/kg for RNT and CT, respectively). Tillage did not influence the patterns in SOC across aggregates but did change the aggregate‐size distribution, indicating that tillage affected soil fertility primarily by changing soil structure.     

Dose-dependent effect of compost amendment on soil bacterial community composition and co-occurrence network patterns in soybean agroecosystem

ABSTRACT

This study aimed to elucidate the effects of various doses of compost amendment on bacterial community compositions and co-occurrence network patterns across the growing season in black soil, Northeast China. Bacterial richness was unaffected by compost addition in seedling and flowering stage, whereas significantly enhanced by high level of compost addition (45,000 kg ha^?1) in mature stage. Non-metric multidimensional scaling analysis revealed distinct bacterial communities in response to compost addition across the growing season. At phylum level, copiotrophic groups of bacteria including Bacteroidetes and Firmicutes gradually increased in relative abundance along with compost rate, while oligotrophic groups (Planctomycetes and Verrucomicrobia) showed opposite tendency. Notably, these enrichment or reduction was most pronounced in seedling stage. Abundant genera including Actinomadura, Aminobacter, Cellvibrio, Devosia, Luteimonas, Microbacterium, Nonomuraea, Promicromonospora were positively and consistently correlated with compost rate, whereas Arthrobacter, Flavisolibacter, Janthinobacterium, Kaistobacter negatively correlated. Network analysis indicated that compost amended soils (40.0, 49.0, and 64.0%) harbored more positive links than control (37.6%). In addition, the soil bacterial network connectivity and connectedness generally increased along with the compost rate, while modularity exhibited opposite trend. Overall, our findings show that compost addition modified the bacterial community compositions and network patterns in soybean agroecosystem in Northeast China.     

不同种植年限葡萄园根区土壤养分变化及对再植葡萄生长的影响

研究了种植葡萄30年重茬3次和种植葡萄3年新建葡萄园的根区土壤养分变化,结合盆栽试验,分析了不同葡萄园根区土壤对再植葡萄生长发育的影响。结果表明,连作葡萄园土壤有机质及大量元素N、P、K、水溶性Ca、Mg含量并未减少,表现出显著增加趋势,而微量元素变化较为复杂,随着葡萄种植时间延长,Fe、Mn含量减少,Zn、Cu含量增加,Zn/Mn、Zn/Fe、N/Fe、P/Fe、Zn/K等比例失调,其中Zn/Mn、Zn/Fe比例失调最为严重。与新植园土盆栽葡萄相比,连作园根区土盆栽葡萄的株高、茎粗、地上鲜重、地下鲜重、叶绿素含量和根系活力均较低,分别比新植园土盆栽葡萄降低39.80%、5.82%、47.97%、30.17%、30.36%和21.22%,表现出明显的重茬障碍症状。连作土壤中Fe含量减少,Zn/Mn、Zn/Fe比例失调可能是葡萄连作障碍产生的重要原因之一。     

Changes in mineral nitrogen, soil organic matter fractions and microbial community level physiological profiles after application of digested pig slurry and compost from municipal organic wastes to burned soils

In this study, mineralization of digested pig slurry and compost from municipal organic wastes in burned soils was followed for 60 days. The effects of amendments on organic matter fractions and microbial community level physiological profiles (CLPP) were also investigated at the end of the incubation period. Soil from a forest 10 days after a fire had a greater basal respiration, and more organic matter that a nearby soil that was not affected by fire, presumably as a consequence of black ash addition following the wildfire. Nitrification was inhibited in soils treated at 105 and 250 °C in the laboratory, but amendment application allowed nitrification to take place in the latter soil, and led to significant flushes of mineralization. Slurry amendment resulted in greater increases in mineral N compared with compost. Soil treated at 250 °C had the greatest content of water-extractable compounds (WE) at the expense of acid-extractable compounds (AE), but during the incubation the variations in these two fractions had an opposite trend, i.e. soil gained AE and lost WE fractions. The variation in N-acetyl-glucosamine-induced respiration was different between compost- and slurry-amended soils, with the greater values in the former. The effect of amendments could be further differentiated by principal component (PCA) and cluster analyses based on the variations in organic matter fractions and CLPP between the beginning and the end of the incubation period. Amendment application led to shifts on the PCA maps that depended both on the amendment and soil treatment. In fresh soil and in that treated at 250 °C, the unamended, compost- and slurry-amended treatments remained relatively close on the PCA maps and had linkage distances <1.0. In contrast, amendment application to other soils led to large shifts on the PCA maps and to linkage distances >1.0. Pig slurry led to the greatest changes in burned soil, while compost induced the greatest shifts in soil treated at 105 °C.This study suggests that an application of organic amendments after a severe fire event may contribute to a faster recovery of soil functions.