Enhancing Soil Quality through Residue Management in a Rice-Wheat System in Fukuoka,Japan

A long-term experiment (LTE) on a rice-wheat system was initiated in 1963 at the Kyushu National Agricultural Experiment Station, in Fukuoka, Japan, to determine the effects of continuous application of rye grass/wheat straw, rice straw and rice straw compost, alone or in combination with inorganic N on crop yields. Increase in rice yields and enhancement of total soil C and N contents with the application of organic residues in this LTE have been reported earlier. However, evaluation of the changes in the soil microbiological properties and the decomposable C fraction of soil organic matter that is needed for soil quality assessment is still lacking. Soil samples were collected after rice harvest in 2003 from the organic residue treatments and unfertilized control, air-dried and incubated for 1 month under aerobic [50% water-filled pore space (WFPS)] and flooded conditions prior to the analysis of the amount of microbial biomass C (MBC), soil respiration and the amount of potential mineralizable N (PMN). The contents of total C (TC), total N (TN), organic C (OC), hot water-extractable C (HWEC) and permanganate-oxidizable C (POC) were determined from air-dried soils. Organic residue incorporation brought about significant increases in the contents of TC, TN, OC, POC, HWEC and PMN. The largest accumulation of total C (23%) and N (72%) in the soil was from rice straw compost, compared with that from rice straw (C, 7% and N, 33%) and rye grass/wheat straw (C, 9% and N, 29%). Incorporation of rice straw compost also increased the amount of MBC under both aerobic and flooded conditions and basal soil respiration under aerobic conditions only. An efficient utilization of C by microorganisms was indicated by a significantly lower metabolic quotient (qCO₂) in the composted and uncomposted rice straw treatments compared with the control in the “-” N treatment under aerobic conditions. Similarly, the flush of CO₂ after rewetting of dry soil per unit of HWEC was lower in the organic matter treatments, indicating a more efficient C utilization and lower C losses per unit of available C. The content of HWEC was significantly correlated with the basal soil respiration (at 50% WFPS), the amounts of MBC, PMN and with the increase in the content of soil organic C in the residuetreated soils. In the treatments without inorganic N fertilizer, grain yield was significantly correlated with the amounts of total organic C, HWEC, MBC (at 50% WFPS), basal soil respiration (at 50% WFPS) and the amount of PMN.     

Decomposition of peat,biogenic municipal waste compost,and shrub/grass compost added in different rates to a silt loam

An incubation experiment was carried out to test the effects of biogenic municipal waste (compost I) and shrub/grass (compost II) composts in comparison to peat on respiration and microbial biomass in soil. The amounts of these three substrates added were linearly increased in the range of field application rates (0.5%, 1.0%, 1.5%, 2.0%). The sum of CO₂ evolved during the incubation was markedly raised by the three substrates and increased with the rate of substrate concentration. However, the percentage of substrate mineralized to CO₂ decreased with the addition rate from 103 to 56% for compost I, from 81 to 56% for compost II, and from 21 to 8% for peat. During the first 25 days of incubation, compost I enlarged the biomass C content, which remained constant until the end. In contrast, compost II did not raise biomass C initially. But at the end of the incubation, the biomass C content of all 4 compost II treatments almost reached the level of the respective compost I treatment. The increase was significantly larger the more of the two composts was added. In contrast to the two composts, the addition of peat did not have any significant effect on microbial biomass C. The average qCO₂ values at day 25 declined in the order compost I > compost II > peat, at day 92 the order was changed to compost II > peat > compost 1. This change in the order was caused by a significant decrease in qCO₂ values of the compost I treatments, a significant increase in qCO₂ values of the peat treatments and constant qCO₂ values in the compost II treatments.     

植茶年龄对茶园土壤微生物特性及酶活性的影响

分析了浙江省两个典型茶区土壤化学、微生物学性质以及酶活性。结果表明,茶园土壤的酸化程度随植茶年龄的增加而加重,土壤有效态N以NO-3 N为主。两茶区高龄茶园的土壤微生物量均很低,表明长期植茶形成的独特生态环境对微生物有抑制作用。两茶园土壤微生物代谢商(Rmic/Cmic)都较非茶园对照土壤低,并且随植茶年龄的增加,两者呈相似的变化趋势。土壤微生物商的变化可能与茶园土壤环境胁迫状况有关,低龄茶园的土壤微生物商(Cmic/Corg)高于非茶园对照土壤,也明显高于高龄茶园。土壤有机碳,全N ,有效P ,NH-4 N ,NO-3 N ,脲酶和酸性磷酸酶活性均随植茶年龄的增加而增加,而与土壤pH值呈相反的变化趋势     

Deforestation and Cultivation with Maize (Zea mays L.) has a Profound Effect on the Bacterial Community Structure in Soil

In this study, the effect of deforestation and cultivation of maize (Zea mays L.) on the physicochemical characteristics and the bacterial community structure in soil were studied at the national park Área de Protección de Flora y Fauna Nevado de Toluca in Mexico. Soil was sampled from three forested areas in the national park, from three deforested areas grazed by animals and from three areas cultivated with maize. The soil was characterized chemically and biologically, whilst the bacterial community structure was investigated through 454 pyrosequencing of the 16S rRNA gene. The pH in the forest soil decreased from 6·1 to 5·3 in the maize‐cultivated soil, whilst the soil organic C content decreased 1·4 times in the arable soil compared with the forest soil. The microbial biomass C decreased 2·9 times in the arable soil compared with the forest soil, but the metabolic quotient qCO₂ (ratio basal respiration to microbial biomass C) nearly doubled. Deforestation and maize cultivation reduced the abundance of Proteobacteria, Actinobacteria and Bacteroidetes, whereas Acidobacteria, Chloroflexi, Gemmatimonadetes and Firmicutes were resistant to these changes. It was found that soil characteristics were affected negatively by deforestation and nearly half of the organic matter was lost, and on these sloped fields, erosion will be high, further decreasing soil fertility. Although the relative abundance of a number of bacterial groups was reduced by deforestation, others were not affected by land‐use change. Copyright © 2014 John Wiley & Sons, Ltd.     

Microbial biomass and soil organic carbon accumulation on a former lakebed near Novosibirsk,Russia

Shrinking of Lake Chany in W Siberia exposed 10,000 km² of former lakebed. On this new land we studied a chronosequence of young soils. The fraction of microbial C in total organic C had stabilized at 3% after 30 to 40 y. Concentration of organic C increased within the first 50 to 100 y to 4–5% in the first 10 cm, and to 2–3% at 10–20 cm depth. The amount of sequestered C is equivalent to about 2.5 d of current anthropogenic CO₂ emissions.     

Effects of Inorganic and Organic Fertilizers on Soil CO2 Efflux and Labile Organic Carbon Pools in an Intensively Managed Moso Bamboo (Phyllostachys pubescens) Plantation in Subtropical China

Impact of combined application of inorganic and organic fertilizers on soil carbon dioxide (CO₂) emission is poorly understood. We investigated the effects of inorganic fertilizer (IF), organic fertilizer (OF), and a mixture of organic and inorganic fertilizers (OIF) applications on the dynamics of soil CO₂ efflux in intensively managed Moso bamboo plantations. Soil CO₂ efflux and concentrations of water soluble organic C (WSOC) and microbial biomass C (MBC) in the IF treatment were higher than those in the control but lower than those in the OF and OIF treatments. Both OF and OIF treatments increased the SOC stock. Strong exponential relationships (p < 0.01) between soil temperature and CO₂ efflux were observed in all treatments. Soil CO₂ efflux in all four treatments was correlated with WSOC (p < 0.05) but not with MBC. We concluded the combined approach can possibly contribute to increasing the level of SOC stock in intensively managed plantations.     

自然培养条件下全球变暖对山毛榉林土壤微生物活性的影响

Microbial activity in soil is known to be controlled by various factors. However, the operating mechanisms have not yet been clearly identified, particularly under climate change conditions, although they are crucial for understanding carbon dynamics in terrestrial ecosystems. In this study, a natural incubation experiment was carried out using intact soil cores transferred from high altitude(1 500 m) to low(900 m) altitude to mimic climate change scenarios in a typical cold-temperate mountainous area in Japan. Soil microbial activities, indicated by substrate-induced respiration(SIR) and metabolic quotient(q CO2), together with soil physicalchemical properties(abiotic factors) and soil functional enzyme and microbial properties(biotic factors), were investigated throughout the growing season in 2013. Results of principal component analysis(PCA) indicated that soil microbial biomass carbon(MBC) andβ-glucosidase activity were the most important factors characterizing the responses of soil microbes to global warming. Although there was a statistical difference of 2.82 ℃ between the two altitudes, such variations in soil physical-chemical properties did not show any remarkable effect on soil microbial activities, suggesting that they might indirectly impact carbon dynamics through biotic factors such as soil functional enzymes. It was also found that the biotic factors mainly controlled soil microbial activities at elevated temperature,which might trigger the inner soil dynamics to respond to the changing environment. Future studies should hence take more biotic variables into account for accurately projecting the responses of soil metabolic activities to climate change.     

不同植被恢复对侵蚀型红壤活性碳库的影响

为了解侵蚀型红壤不同植被恢复后,土壤有机碳的演变状况,采集了持续时间为17年和9年的2个定位试验点土壤样品,分析了土壤总有机碳、微生物量碳、水溶性碳和矿化态碳含量.结果表明侵蚀型红壤植被恢复后,土壤总有机碳和各类活性碳含量均明显增加,并随着恢复时间的延长,土壤各类碳含量显著上升.同样是杉木林,恢复17年的土壤(0～20 cm)总有机碳、微生物量碳、水溶性碳和矿化态碳的含量分别是恢复9年土壤的2.18倍、2.95倍、2.25倍和2.01倍.不同处理比较来看,木荷林土壤各类碳含量明显高于杉木林土壤,黑麦草处理矿化态碳含量明显高于恢复时间相同的杉木和胡柚处理.分析了各处理活性碳占总有机碳的比例发现,植被恢复17年的2个处理,土壤微生物量占总有机碳比例明显高于恢复9年的3个处理;恢复时间分别为17年和9年的2个杉木处理,土壤水溶性碳占总有机碳比例明显较高,而矿化态碳占总有机碳比例明显偏低;黑麦草处理矿化态碳占总有机碳比例明显高于恢复时间相同的杉木和胡柚处理.从相关分析来看,土壤总有机碳、微生物量碳、水溶性碳及矿化态碳两两之间相关性均达极显著水平(P＜0.01);土壤各类碳与土壤全氮、水解氮、有效磷含量之间也具有极显著相关性.     

水稻-小麦轮作系统中土壤活性有机碳库对长期施用化肥，秸秆和粪便的敏感度

Labile soil organic carbon(SOC) pools, estimated through chemical fractionation techniques, are considered sensitive indicators of management-induced changes in quality and composition of soil organic matter. Although the impacts of organic manure and crop residue applications on C sequestration in rice-wheat system are fairly well documented, their influence on labile SOC pools is relatively less known. Impacts of organic manure, rice straw, and inorganic fertilizer nitrogen(N) applications on soil total organic carbon(TOC)and SOC pools including water-extractable organic C(WEOC), hot water-soluble organic C(HWOC), potassium permanganateoxidizable organic C(KMnO 4-C), microbial biomass C(MBC), mineralizable organic C(Cmin), and the oxidizable fractions of decreasing oxidizability(easily-oxidizable, oxidizable, and weakly-oxidizable) were investigated in an 11-year field experiment under rice-wheat system. The field experiment included treatments of different combinations of farmyard manure, rice straw, and fertilizer N application rates, with C inputs estimated to be in the range from 23 to 127 Mg ha-1. After 11 years of experiment, WEOC,HWOC, and KMnO 4-C were 0.32%–0.50%, 2.2%–3.3%, and 15.0%–20.6% of TOC, respectively. The easily-oxidizable, oxidizable,and weakly-oxidizable fractions were 43%–57%, 22%–27%, and 10%–19% of TOC, respectively. The applications of farmyard manure and rice straw improved WEOC, HWOC, KMnO 4-C, easily-oxidizable fraction, Cmin, and MBC, though the rates of change varied considerably from-14% to 145% and-11% to 83% of TOC, respectively. At the C input levels between 29 and 78 Mg C ha-1during the 11-year period, the greatest increase was observed in WEOC and the minimum in KMnO 4-C. Water-extractable organic C exhibited a relatively greater sensitivity to management than TOC, suggesting that it may be used as a sensitive indicator of management-induced changes in soil organic matter under rice-wheat system. All the other labile SOC pools exhibited almost the same sensitivity to management as TOC. Most of the SOC pools investigated were positively correlated to each other though their amounts differed considerably. Long-term applications of farmyard manure and rice straw resulted in build-up of not only the labile but also the recalcitrant pool of SOC, emphasizing the need for continued application of organic amendments for permanence of the accrued C under the experimental conditions.     

有机无机肥配施对麦-稻轮作系统土壤微生物学特性的影响

采用盆栽试验研究了不同比例有机无机肥配施对连续4茬麦-稻轮作后土壤微生物学特性的影响。结果表明,与对照相比,单施化肥处理促进了土壤微生物生物量碳、氮和微生物熵的增加,提高了土壤蔗糖酶、蛋白酶、脲酶活性,降低了过氧化氢酶活性,提高了放线菌的数量,但对土壤细菌、真菌数量的影响不明显;有机无机肥配施处理的土壤微生物生物量碳、微生物生物量氮、微生物熵、土壤酶活性及3大类土壤微生物数量显著高于单施化肥及对照处理;土壤微生物生物量碳、微生物生物量氮、微生物熵和3大类微生物数量随着有机肥配施比例的提高而增加,以配施30%有机肥处理的最高;土壤酶活性综合指数以配施20%有机肥处理的最高。可见,化肥配施有机肥特别是配施中高量有机肥更有利于改善土壤微生物学特性,提高土壤生产能力。     

Evaluation of the Effects of Soil Depth on Microbial Activity in Three Agroecosystems in Venezuela

The objective of this study was to determine the total organic carbon (TOC), basal respiration (BR), microbial biomass carbon (MBC), the metabolic quotient (qCO₂), and ratio of microbial biomass carbon to total organic carbon (MBC/TOC) at different soil depths in three agroecosystems in Fundo Zamorano Independencia, Cojedes State, Venezuela. The types of agroecosystems studied were short-cycle corn and bean cropland, pastureland, and gallery forest, which was used as the control soil. The BR was determined by measuring the carbon dioxide released in a closed system, and the MBC was analyzed by applying the substrate-induced respiration method. The BR and the MBC varied depending on depth and transect position, decreasing between 18% and 38% at a depth of >10 cm with respect to the measurements taken between 0 and 10 cm. Significantly greater BR and MBC values were found at the middle transect position, where the soils with the greatest moisture content are located. No significant differences for BR, MBC, and qCO₂ values were found among the agroecosystems. This was due to the high spatial variability of the physical and chemical properties of the soils in the study site. However, with the application of the Kruskal–Wallis test, significant differences for the TOC and MBC/TOC values were found among the agroecosystems. These results highlight the importance of the type of plant cover over soil in different agroecosystems, mainly on pastureland, which maintains the potential of the inocular mycorrhizal of the soil.     

Effect of Clay Minerals on Immobilization of Heavy Metals and Microbial Activity in a Sewage Sludge-Contaminated Soil (8 pp)

Background   Aims, and Scope. Reducing heavy metal solubility and bioavailability in contaminated area without removing them from the soil is one of the common practices in decreasing the negative impacts on the environment and improving the soil quality. Therefore, our aim was to study the effect of clay minerals: Na-bentonite, Ca-bentonite, and zeolite applied to a contaminated soil on immobilization of heavy metals, as well as on some soil parameters related with microbial activity. Methods   A soil derived from sewage sludge was incubated with clay minerals of either Na-bentonite, Ca-bentonite, or zeolite for 111 days (d). During the incubation experiment, concentrations of water soluble Zn, Cd, Cu, and Ni were measured after extraction of 2 g air-dry soil with 50 ml of H2O for 2 h. After the water extraction, the soil sediment was extracted with 50 ml of 1 M NH4NO3 for 2 h to estimate the exchangeable amounts of heavy metals. Furthermore, soil microbial respiration, microbial biomass C, Corg mineralization, metabolic quotient (qCO2), and inorganic N were also investigated. Results and Discussion   Water extractable and exchangeable forms of heavy metals were changed by incubation and addition of clay minerals. Incubation of soil without addition of clay minerals (control) increased water extractable Cu by 12, 24 and 3.8% of initial content after 21, 62, and 111 d of incubation, respectively. The water extractable Zn decreased by 9% during 62 d of incubation and it tended to increase by 14% at the end of the incubation, as compared with the initial soil. Water extractable Cd decreased by 71, 66 and 33% of initial content, and Ni decreased by 54, 70, and 58%, after 21, 62, and 111 d of incubation, respectively. During the incubation experiment, the exchangeable form of all tested metals was decreased by incubation. The addition of clay minerals led to a significant decrease in water soluble and exchangeable forms of heavy metals during the incubation experiment, resulting in low metal extractability. The reduction in metal extractability was greater due to the addition of Na-bentonite or Ca-bentonite than that due to the addition of zeolite. During the first 3 weeks after addition of clay minerals, the studied biological parameters were not affected. However, as incubation progressed, the addition of Na- or Ca- bentonite led to a significant increase in soil respiration, microbial biomass C, Corg mineralization, and inorganic N; and a significant decrease in qCO2. This result is explained by sorption of heavy metals on Na-bentonite and Ca-bentonite and strong reduction of their toxicity. Conclusions   Our results clearly show that the addition of clay minerals, especially of Na-bentonite and Ca-bentonite, decreased the extractability of four metals during incubation. The decreased metal extractability was accompanied by an increase of soil respiration, Corg mineralization, microbial biomass C, and inorganic N and a decrease of metabolic quotient (qCO2), showing positive effect of clay mineral addition on soil biological parameters. Recommendations and Outlook   The use of Na-bentonite and Ca-bentonite is promising tool for reduction the extractability and possible toxicity of heavy metals in sewage sludge-contaminated soil. Therefore, the soils polluted with heavy metals may be ameliorated by addition of clay minerals, especially Na-bentonite and Ca-bentonite.     

不同处理采伐剩余物对营造杉木幼林土壤胞外酶活性的影响

土壤酶对森林生态系统生物化学过程有重要作用,能快速反映土壤环境(如养分含量和有效性)的变化。采伐剩余物是林地土壤养分的重要来源,其处理方式会对森林土壤的养分含量和有效性产生影响。为探讨采伐剩余物不同处理方式对杉木幼林土壤酶活性的影响,在福建省三明市格氏栲自然保护区40年生的杉木成熟林采伐迹地上对采伐剩余物进行不同处理(保留RR、火烧RB、去除R)并种植杉木幼林,通过采集0-10,10-20 cm土层土壤,对6种胞外酶活性进行研究。结果表明:(1)采伐剩余物处理4年后,相比保留处理,火烧和清除处理的土壤可溶性有机碳、可溶性有机氮、无机氮、硝态氮含量均显著下降。其中火烧处理下硝态氮下降幅度显著高于清除处理,2个土层下降幅度平均分别为88%和51%;(2)相比保留处理,火烧和清除处理土壤微生物生物量碳和微生物生物量磷含量以及6种土壤酶活性,即酸性磷酸酶、β-葡萄糖苷酶、纤维素水解酶、β-N-乙酰氨基葡萄糖苷酶、过氧化酶、酚氧化酶均明显更低,而且火烧处理两土层微生物生物量碳和微生物生物量磷含量显著低于清除处理;(3)冗余分析表明,0-10 cm土层土壤酶活性与微生物生物量磷、微生物生物量碳含量显著相关,而可溶性有机氮、硝态氮、微生物生物量碳是影响10-20 cm土层土壤酶活性变化的关键因子。保留采伐剩余物有利于提高土壤养分和酶活性,是土壤肥力维持和森林生产力提高的有效经营管理措施。     

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。     

Effect of Long-Term Soil Management on the Mutual Interaction Among Soil Organic Matter, Microbial Activity and Aggregate Stability in a Vineyard

Vineyard management practices to enhance soil conservation principally focus on increasing carbon (C) input, whereas mitigating impacts of disturbance through reduced tillage has been rarely considered. Furthermore, information is lacking on the effects of soil management practices adopted in the under-vine zone on soil conservation. In this work, we evaluated the long-term effects (22 years) of alley with a sown cover crop and no-tillage (S + NT), alley with a sown cover crop and tillage (S + T), and under-vine zone with no vegetation and tillage (UV) on soil organic matter (SOM), microbial activity, aggregate stability, and their mutual interactions in a California vineyard in USA. Vegetation biomass, microbial biomass and activity, organic C and nitrogen (N) pools, and SOM size fractionation and aggregate stability were analysed. Soil characteristics only partially reflected the differences in vegetation biomass input. Organic C and N pools and microbial biomass/activity in S + NT were higher than those in S + T, while the values in UV were intermediate between the other two treatments. Furthermore, S + NT also exhibited higher particulate organic matter C in soil. No differences were found in POM C between S + T and UV, but the POM fraction in S + T was characterized by fresher material. Aggregate stability was decreased in the order: S + NT > UV > S + T. Tillage, even if shallow and performed infrequently, had a negative effect on organic C and N pools and aggregate stability. Consequently, the combination of a sown cover crop and reduced tillage still limited SOM accumulation and reduced aggregate stability in the surface soil layer of vineyards, suggesting relatively lower resistance of soils to erosion compared to no-till systems.     

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.     

Soil microbiological properties and its stratification ratios for soil quality assessment under different cover crop management systems in a semiarid vineyard

In vineyards in Spain, tillage and semiarid Mediterranean climatic conditions accelerate organic matter loss from the soil. Cover crops are a conservation management practice that can provoke changes in soil quality which requires evaluation. Stratification ratios of soil properties such as soil organic C and labile C fractions have been proposed for the assessment of soil quality under different soil management systems. Our objective was to study the effect of different cover crop management on various soil parameters and their stratification ratios. We evaluated three different soil managements in a Typic Haploxerept from NE Spain: conventional tillage (CT); 5‐y continuous cover crop of resident vegetation (RV); and 4‐y continuous cover crop of Festuca longifolia Thuill., followed by 1‐y Bromus catharticus L. after resowing (BV). We monitored soil organic C, particulate organic C, water soluble C, potentially mineralizable N, microbial biomass C, β‐glucosidase and urease enzymatic activities, and water stable aggregates at 0–2.5, 2.5–5, 5–15, 15–25, and 25–45 cm soil depths. We calculated soil depth stratification ratios of those soil properties. Resident cover crop increased microbiological properties, labile C fractions, and aggregation with respect to conventional tillage at 0–2.5 and 2.5–5 cm soil depths. However, for Bromus cover crop the same soil properties were lower than for the resident cover crop at 0–2.5 cm depth. Stratification ratios of β‐glucosidase and urease enzymatic activities, and particulate organic C showed a higher sensitivity than other soil properties; therefore, they would be the best indicators for soil quality assessment in semiarid Mediterranean vineyards.     

Long‐Term Tillage and Cropping System Effects on Chemical and Biochemical Characteristics of Soil Organic Matter in a Mediterranean Semiarid Environment

Several studies have reported how tillage and cropping systems affect quantity, quality, and distribution of soil organic matter (SOM) along the profile. However, the effect of soil management on the chemical structure of SOM and on its hydrophobic and hydrophilic components has been little investigated. In this work, the long‐term (19 years) effects of two cropping systems (wheat monoculture and wheat/faba bean rotation) and three tillage managements (conventional, reduced, and no tillage) on some chemical characteristics of SOM and their relationships with labile carbon (C) pools were evaluated. Soil samples were taken from the topsoil (0–15 cm) of a Chromic Haploxerert (central Sicily, Italy). After 19 years of different tillage and cropping systems management, total organic C significantly differed among treatments with the labile organic C pools showing the greater amount in no till and in wheat/faba bean plots. Hydrophobic and hydrophilic components of SOM, determined by diffuse reflectance infrared Fourier transform spectroscopy, were mainly affected by cropping system, whereas aromatic components of SOM by tillage. Soil organic matter components and characteristics showed significant correlations with the soil biochemical parameters, confirming the expected synergism between chemical and biochemical properties. This study demonstrated that (i) no tillage and crop rotation improve the chemical and biochemical properties of SOM of Vertisols under semiarid environment; and (ii) tillage management and cropping systems have affected, after 19 years, more the chemical and biochemical properties of SOM than its quantity. Copyright © 2014 John Wiley & Sons, Ltd.     

黄土区不同类型土壤微生物量碳、氮和可溶性有机碳、氮的含量及其关系

研究了黄土高原南部地区不同土壤类型及不同利用方式下土壤微生物摄碳、氮和可溶性有机碳、氮的含量。结果表明：不同土地利用方式下，土壤微生物量碳、氮和可溶性有机碳、氮含量均为林地〉农田，其中林地枯枝落叶层〉林地O～20cm土层。农田土壤微生物量碳、氮的含量均为红油土〉黑垆土〉淋溶褐土；农田土壤中可溶性有机碳含量为淋溶褐土〉红油土〉黑垆土，而可溶性有机氮含量则为黑垆土〉红油土〉淋溶褐土。方差分析表明，不同土壤类型土壤微生物量氮含量之间的差异达显著水平，而不同土壤类型间土壤微生物量碳、可溶性有机碳、氯含量之间的差异未达显著水平。土壤微生物量碳、氮占土壤有机碳和全氮的比例明显高于可溶性有机碳、氮占土壤有机碳和全氮的比例。相关分析发现，土壤微生物量碳与可溶性有机碳之间以及土壤微生物量氮与可溶性有机氮之间的相关性达显著或极显著水平，说明土壤微生物量碳、氮和土壤可溶性有机碳、氮之间有密切联系。