Organic carbon stocks and soil erodibility in Canary Islands Andosols   总被引：3，自引：0，他引：3  

A. Rodríguez Rodríguez  C.D. Arbelo  J.A. Guerra  J.L. Mora  J.S. Notario  C.M. Armas 《CATENA》2006,66(3):228-235

Soil organic carbon (SOC) plays a key role in the structural stability of soils and in their resistance against erosion. However, and as far as andic soils are concerned, these mechanisms and processes, as well as the influence of the different types of SOC on aggregate stability, are not fully understood. The targets of this paper are: (i) to determine the content and forms of SOC in Andosols under evergreen forest vegetation [laurel (Laurus) and heather (Erica) forest] and (ii) to find out the role of soil organic matter (SOM) in the aggregate stability and in the resistance of Andosols to water erosion. Soil samples have been collected in 80 sites in a 40 km² area under udic soil moisture regime. In them, fulvic and humic acids, Walkley–Black SOC, pyrophosphate-extractable SOC, Fe and Al, potassium sulphate extractable SOC, dissolved SOC, acid oxalate-extractable Fe, Al and Si, USLE K-factor and aggregate stability have been determined. The Andosols over volcanic ash are Aluandic Andosols (non-allophanic Andosols), whereas over basaltic lava flows are Silandic Andosols (allophanic Andosols). The surface (0–30 cm) samples analyzed contain 9.5–30 kg C m^− 2 being significantly higher in allophanic Andosols (p < 0.5). Organic carbon adsorbed onto the mineral fraction (extractable pyrophosphate, C_p) accounts for 35–55% of the total SOC. All samples show a high stability to slaking and raindrop impact, being the first one highly correlated (r = 0.6) with pyrophosphate extractable C (C_p), Fe (Fe_p), and Al (Al_p) in allophanic Andosols, unlike non-allophanic ones. The stability to raindrop impact correlates with pyrophosphate extractable C (C_p) and Fe (Fe_p) in both types of soils (r = 0.3–0.6, p < 0.05). These findings suggest that the high stability to both slaking and water-drop impact is due to the occurrence of allophane–Fe–OC complexes, rather than to the total OC, and the active Fe and Al forms, generated by the weathering of volcanic materials, constitute an essential constituent responsible for C sequestration and resistance to degradation in these soils.  相似文献   

SOCRATES—A simple model for predicting long-term changes in soil organic carbon in terrestrial ecosystems     

Peter R. Grace  Jeffrey N. Ladd  Stuart H. Gage 《Soil biology & biochemistry》2006,38(5):1172-1176

The maintenance of soil organic carbon (SOC) in terrestrial ecosystems is critical for long-term productivity. Simulation models of SOC dynamics are valuable tools in predicting the impacts of climate on carbon storage and developing management strategies for the mitigation of greenhouse gas emissions, however, their utility is generally reduced due to need for specific data. The SOCRATES model is a simple process based representation of soil SOC dynamics in terrestrial ecosystems, which requires minimal data inputs and specifically designed to examine the impact of land use and land use change on soil carbon storage. SOCRATES was successful in predicting SOC change at eighteen long-term crop, pasture and forestry trials from North America, Europe and Australasia. These trials ranged from 8 to 86 years in duration, over a wide range of climates and soil types with annual changes in SOC ranging from −3.0 to 4.2%.  相似文献   

Influence of repeated prescribed burning on the soil fungal community in an eastern Australian wet sclerophyll forest     

Brigitte A. Bastias  Tim Blumfield  John W.G. Cairney 《Soil biology & biochemistry》2006,38(12):3492-3501

A long-term prescribed burning experiment, incorporating replicated plots that receive burning biennially (2 yr burn) or quadrennially (4 yr burn) and unburned controls, has been maintained in a wet sclerophyll forest at Peachester, Queensland, Australia since 1972. In 2003 we extracted DNA from soil collected from the experimental plots and investigated the influence of the burning on the soil fungal community by comparing denaturing gradient gel electrophoresis (DGGE) profiles of PCR-amplified partial rDNA internal transcribed spacer regions (ITS1). Canonical analysis of principal coordinates (CAP) of the DGGE profiles of the upper 10 cm of the soil profile grouped the data strongly according to treatment, indicating that both burning regimes significantly altered fungal community structure compared to the unburned controls. In contrast, no obvious trend was observed for soil from a depth of 10-20 cm of the profile. Sequencing of selected DGGE bands found no obvious patterns of presence/absence of taxonomic groups between the treatments. Analysis of soil nitrogen and carbon by mass spectrometry indicated that total soil C and N, along with both gross and net N mineralisation, were significantly lower in 2 yr plots compared to control and 4 yr plots.  相似文献   

土壤有机质空间变异与农用地自然质量关系研究   总被引：1，自引：0，他引：1  

包世泰  赵寒冰  胡月明  李勇  王建芳 《农业工程学报》2007,23(8):95-101

该文以广州市花都区赤坭镇为试验区，根据典型农用地类型的土壤采样基于Cokriging方法进行土壤有机质精确插值与空间变异分析，并将结果与农用地分等成果进行相关分析。结果表明，以土壤有机质和农用地类型为协因子的球状模型Cokriging总体插值精度最高，试验区内土壤有机质分布格局是四周丘陵和水库区含量较低，巴江河两岸的平原地区、西南角的山前冲积平原含量较高，这也是灌溉水田密集的区域；试验区内土壤有机质含量菜地分布比较均匀、空间相关性很强，而水浇地分布差异较大、空间变异性较高；土壤有机质分布在南北、东北-西南两个方向相关性较强具有各向同性特征，在东南-西北、东西方向具有各向异性特征，受到随机因素的影响变异性较大。土壤有机质Cokriging插值结果与试验区内农用地自然质量等指数的相关性很显著，菜地与农用地自然质量等指数相关性最强，灌溉水田其次，旱地最差。  相似文献   

A comparison of two methods for the isolation of free and occluded particulate organic matter     

Angelika Klbl  Jens Leifeld  Ingrid Kgel‐Knabner 《植物养料与土壤学杂志》2005,168(5):660-667

Various methods exist for the isolation of particulate organic matter (POM), one of the soil‐organic‐matter (SOM) fractions reacting most sensitive on land‐use or soil‐management changes. A combination of density separation and ultrasonic treatment allows to isolate two types of POM: (1) free POM and (2) POM occluded in soil aggregates. POM fractions are closely linked to their biochemical function for the formation and stabilization of aggregates, therefore methods using different aggregate sizes may result in different POM fractions isolated. We evaluated two physical fractionation procedures to reveal whether they yield different POM fractions with respect to amount and composition, using grassland and arable soils with sandy‐loam to sandy–clay‐loam texture and thus low macroaggregate stability. Method I used air‐dried aggregates of <2.0 mm size and a low‐energy sonication for aggregate disruption, method II used field‐moist aggregates <6.3 mm and a high‐energy–sonication procedure for aggregate disruption. POM fractions were analyzed by elemental analysis (C, N) and CPMAS ¹³C‐NMR spectroscopy. With both methods, about similar proportions of the SOM are isolated as free or occluded POM, respectively. The free‐ and occluded‐POM fractions obtained with method I are also rather similar in C and N concentration and composition as shown by ¹³C‐NMR spectroscopy. Method II isolates a free‐ and occluded‐POM fraction with significantly different C and N concentrations. NMR spectra revealed significant differences in the chemical composition of both fractions from method II, with the occluded POM having lower amounts of O‐alkyl C and higher amounts of aryl C and alkyl C than the free POM. Due to the use of larger, field‐moist aggregates with minimized sample pretreatment, two distinctly different POM fractions are isolated with method II, likely to be more closely linked to their biochemical function for the formation and stabilization of aggregates. High‐energy sonication as in method II also disrupts small microaggregates <63 µm and releases fine intraaggregate POM. This fraction seems to be a significant component of occluded POM, that allows a differentiation between free and occluded POM in sandy soils with significant microaggregation. It can be concluded, that microaggregation in arable soils with sandy texture is responsible for the storage of a more degraded occluded POM, that conversely supports the stabilization of fine microaggregates.  相似文献   

Comparative effects of annual and permanent dairy pastures on soil physical properties in the Tsitsikamma region of South Africa   总被引：1，自引：0，他引：1  

R.M. Milne  R.J. Haynes 《Soil Use and Management》2004,20(1):81-88

Abstract. The effects of grazed, annual ryegrass pasture (annually tilled with a rotary cultivator) and permanent kikuyu pasture were compared with that of undisturbed native vegetation at four sites in the Tsitsikamma region, South Africa. Soil organic carbon content, aggregate stability, saturated hydraulic conductivity, air permeability, root length density and rooting depth were all less under ryegrass than kikuyu pasture. There was, however, no consistent effect of pasture-type on pore size distribution or penetrometer resistance. Differences in penetrometer resistance were most obvious in the 10–30 cm layer with subsurface compaction being evident at some sites under both types of pasture. This was attributed to the treading effects of grazing cattle plus formation of a compacted layer at the depth of tillage under ryegrass pastures. Subsoil tillage of a ryegrass pasture resulted in a substantial reduction in penetrometer resistance in the compacted 10–20 cm layer and increases in hydraulic conductivity, air permeability, root length density and rooting depth. We conclude that conversion from conventional to zero tillage is a potential way of improving the sustainability of annual pasture production and that the extent of subsoil compaction under both pasture types needs further investigation.  相似文献   

Controls on soil respiration in semiarid soils   总被引：2，自引：0，他引：2  

Richard T Conant  Peter Dalla-Betta  Jeffrey M Klopatek 《Soil biology & biochemistry》2004,36(6):945-951

Soil respiration in semiarid ecosystems responds positively to temperature, but temperature is just one of many factors controlling soil respiration. Soil moisture can have an overriding influence, particularly during the dry/warm portions of the year. The purpose of this project was to evaluate the influence of soil moisture on the relationship between temperature and soil respiration. Soil samples collected from a range of sites arrayed across a climatic gradient were incubated under varying temperature and moisture conditions. Additionally, we evaluated the impact of substrate quality on short-term soil respiration responses by carrying out substrate-induced respiration assessments for each soil at nine different temperatures. Within all soil moisture regimes, respiration rates always increased with increase in temperature. For a given temperature, soil respiration increased by half (on average) across moisture regimes; Q₁₀ values declined with soil moisture from 3.2 (at −0.03 MPa) to 2.1 (−1.5 MPa). In summary, soil respiration was generally directly related to temperature, but responses were ameliorated with decrease in soil moisture.  相似文献   

Impact of organic fertilisation on lettuce biomass production according to the cultivation duration in tropical soils     

Falilou Diallo  Dominique Masse  Karamoko Diarra  Frédéric Feder 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2020,70(3):215-223

ABSTRACT

The productivity levels of two arenosol (Ar40) and fluvisol (FL40) fields that had been cultivated for over 40 years were compared to that of fields with the same soils located nearby but never previously cultivated, i.e. Ar0 and FL0, respectively. Application of poultry manure (PM) and sewage sludge (SS) were compared to a mineral fertilizer (T100), corresponding to 100 kg/ha of nitrogen, over three lettuce (Lactuca sativa L.) crop cycles. PM and SS were applied at 50 and 150 kg/ha nitrogen equivalent fertilizer doses. Biomass production levels in the organic and mineral treatments were similar, except for the SS-50 for FL0 and the PM-150 for Ar40, FL40 and FL0. Biomass production levels of Ar40 were higher than those of Ar0 for the first cycle. In the initial state, the soil P content in Ar40 was higher than that of the Ar0 soil. With the treatment repetition, Ar0 showed the same production level as Ar40. For the fluvisols, biomass production levels of FL40 were lower than those of FL0 for the first cycle. Indeed, the initial nitrate content in FL40 was lower than in FL0. The biomass production levels of FL40 were higher than those of FL0 for the following cycles.  相似文献   

Status and distribution of soil sulphur fractions,total nitrogen and organic carbon in camp and non-camp soils of grazed pastures supplied with long-term superphosphate     

M. L. Nguyen  K. M. Goh 《Biology and Fertility of Soils》1992,14(3):181-190

Summary Topsoils (0–75 mm) from four different soil types were collected from stock camp and non-camp (main grazing area) areas of grazed pastures in New Zealand, which had been fertilised annually with superphosphate for more than 15 years, in order to assess the effects of grazing animals on the status and distribution of soil S fractions and organic matter. These soils were analysed for organic C, total N, total S, C-bonded S, hydriodic acid-reducible S, 0.01 M CaCl₂, and 0.04 M Ca(H₂PO₄)₂-extractable S fractions, and soil pH. Soil inorganic and organic S fractions extracted by NaHCO₃ and NaOH extractants were also determined. The results obtained showed that camp soils contain higher soil pH, organic C, total N, total S, organic (C-bonded S and hydriodic acid-reducible S) and inorganic S fractions, NaHCO₃-and NaOH-extractable soil S fractions but a lower anion retention capacity than non-camp soils, attributed to a higher return of plant litter and animal excreta to camp soils. In both soils, total S, organic S, C-bonded S, and hydriodic acid-reducible S were significantly correlated with organic C (r0.90***, ***P0.001) and total N (r0.95***), suggesting that C, N, and S are integral components of soil organic matter. However, C: N : S ratios tended to be lower in camp (60: 5.6: 1–103: 7.2: 1) than in non-camp soils (60:6.1:1–117:8.3:1). Most (>95%) of the total soil S in camp and non-camp soils is present as organic S, while the remainder is readily soluble and adsorbed S (i.e. Ca(H₂PO₄)₂-extractable S). C-bonded S and hydriodic acid-reducible S constituted 55%–74% and 26%–45% of total S, respectively, reflecting a regular return of plant litter and animal excreta to the grazed pastures. NaHCO₃, and especially NaOH, extracted significantly higher amounts of total soil S (13%–22% and 49%–75%, respectively) than Ca(H₂PO₄)₂ or CaCl₂ (<5%). In addition, NaHCO₃ and NaOH-extractable soil S fractions were significantly rorrelated with soil organic S (r0.94***), C-bonded S (r0.90***) and hydriodic acid-reducible soil S (r0.93***). Differences between soils in either camp or non-camp areas were related to their sulphate retention capacities, as soils with high sulphate retention capacities (>45%) contain higher levels of C-bonded and hydriodic acid-reducible S fractions than those of low sulphate retention soils (<10%). Long-term annual superphosphate applications significantly increased the accumulation of soil organic and inorganic S fractions, and organic C and total N in the topsoil, although this accumulation did not occur when the superphosphate application rates were increased from 188 to 376 kg ha^-1 year^-1.  相似文献   

蜡梅花茶窨制工艺流程的初步研究   总被引：3，自引：0，他引：3  

李永菊  司辉清  庞晓莉  朱成科 《南方农业》2007,1(2):21-24

采用2因素完全随机试验设计对蜡梅花茶窨制工艺进行试验研究,对所得数据利用DPS统计软件进行结果分析,得出配花总量、窨次以及它们的交互作用对蜡梅花茶品质都有显著的影响;多重比较(LSD法)得出配花总量为76kg/100kg、2窨次的花茶感官审评得分最高,与其他处理的差异达到极显著。  相似文献