提高农产品品质与减少硝酸盐污染的施肥技术研究

6年试验研究结果表明,农业生产采用N、P、K平衡施肥,增施优质微生物肥料,微生物肥与无机肥、有机肥配施,适当减少化肥用量等施肥技术均提高作物产量和产值,尤其对改善农产品品质、减少硝酸盐污染效果明显,增施微生物肥和有机肥,减少N素化肥用量10％、50％,蔬菜可食部硝酸盐降低17.04％～24.86％。     

黑碳在土壤有机碳生物地球化学循环中的作用

黑碳是化石燃料或生物有机体不完全燃烧形成的一种含有芳香环的高聚物,碳元素含量在60%以上,另含有氢、氧、氮、硫等元素。新近的研究证实,黑碳通过在缓慢的土壤有机碳库中的循环,对全球碳和氧的地球生物化学循环起到极其重要的作用。本文对黑碳的基本概念、理化性质、在土壤中的作用及测定方法进行了综合评述,提出了开展土壤黑碳研究的重要性和必要性。以期为我国开展土壤黑碳的相关研究提供理论参考。     

土壤溶解性有机碳(DOC)的影响因子及生态效应

土壤溶解性有机碳(DOC)是陆地生态系统中极为活跃的有机组分,是土壤圈层与相关圈层(如生物圈、大气圈、水圈和岩石圈等)发生物质交换的重要形式。影响土壤中物质的溶解、吸附、解吸、吸收、迁移乃至生物毒性等行为之外,对温室气体CH4的排放、水体水质的污染、岩石圈的风化等的影响也不可忽视。本文以陆地生态系统的中的DOC为主体,探讨了DOC的生态环境意义及其对大气、水体和岩石圈的影响以及DOC对土壤管理措施的响应。     

Comparison of approaches for estimating carbon sequestration at the regional scale

Abstract. Many former estimates of regional scale C sequestration potential have made use of linear regressions based on long-term experimental data, whilst some have used dynamic soil organic matter (SOM) models linked to spatial databases. Few studies have compared the two methods. We present a case study in which the potential of different land management practices to sequester carbon in soil in arable land is estimated by different methods. Two dynamic SOM models were chosen for this study, RothC (a soil process model) and CENTURY (a whole ecosystem model with a SOM module). RothC and CENTURY are the two most widely used and validated SOM models worldwide. A Geographic Information System (GIS) containing soil, land use and climate layers, was assembled for a case study in central Hungary. GIS interfaces were developed for the RothC and CENTURY models, thus linking them to the spatial datasets at the regional level. This allowed a comparison of estimates of the C sequestration potential of different land management practices obtained using the two models and using regression based approaches. Although estimates obtained by the different approaches were of the same order of magnitude, differences were observed. Some of the land management scenarios studied here showed sufficient C mitigation potential to meet Hungarian CO₂ reduction commitments. For example, afforestation of 12% current arable land could sequester 0.042–0.092 Tg yr^–1 in the soil alone, or 0.285–0.588 Tg C yr^–1 in both soil and biomass; 1990 level CO₂ emissions for the study area were 4.7 Tg C with a corresponding reduction commitment of 0.282 Tg C. It is not, however, suggested that this is the only, or the most favourable way, in which to meet the commitments.     

有机污染物根际胁迫及根际修复研究进展

根际环境及根际微生物是植物降解有毒有害有机污染物的基础。污染土壤植物修复的纵深研究产生了根际修复新技术。通过总结近20年来有机污染物胁迫的根际效应的研究,探讨了有机物污染士壤根际修复的可能性,为加强有机污染物在环境中的迁移、调控研究及土壤有机物污染的原位修复提供有利信息。     

Seasonal patterns of cellulase concentration in desert soil

The concentration of cellulose in plant material greatly affects the decomposition rate of plant-derived litter and hence carbon availability. The disappearance of pure cellulose in soil was studied as a measure of plant decomposition and carbon turnover. Our objective was to understand the effect of various cellulose concentrations and plant material added to soil and collected during different seasons, on cellulase concentrations under laboratory conditions (e.g. constant soil moisture and incubation temperature). The percentage of recovery of the enzyme in the control soil and in samples amended with known amounts of cellulose powder was estimated. Several methods for estimating soil cellulase concentrations/activity are available, most based on the determination of released reducing sugars. The method used in this study is based on the cleavage of a cellulose-azure substrate by cellulase to spectrophotometrically detectable fragments. Our results showed a significant correlation (p<0.05) between cellulose concentration and cellulase levels in soil, which varied along the study period. When pure cellulose was added to the soil, cellulase was detected after 7 days of incubation, whereas when plant material was added to the soil, cellulase was detected after 14 days. The recovery of cellulase from soil was also found to be seasonally dependent. The method of cellulase determination used in this study was simple, safe and rapid. From the results presented in this study, it can be assumed that there are seasonally dependent factors that affect the existence and concentration of cellulase in soils of the arid Negev Desert, in addition to organic matter, water and temperature.     

Decomposition and distribution of N labelled mustard litter (Sinapis alba) in physical soil fractions of a cropland with high- and low-yield field areas

High-yield (HY) areas of an agricultural cropland were characterized by different positions on a slope and lower silt and clay contents, compared to low-yield (LY) areas, and this was associated with differences in water regime and C and N turnover. To understand differences in N flows of HY and LY areas, a combination of ¹⁵N tracer techniques and physical fractionation procedures was applied. Within 570 d after application of ¹⁵N labelled mustard litter to an agricultural cropland, the distribution of ¹⁵N was measured in particulate organic matter (POM) fractions and in fine mineral fractions (fine silt- and clay-sized fractions). After 570 d, only 2.5% of the initial ¹⁵N amount was found in POM fractions, with higher amounts in POM occluded in aggregates than in free POM. After this period, stabilization of the initial ¹⁵N in fine silt- and clay-sized fractions amounts to 10% in HY, but 20% in LY soils. 70% to 85% of the added ¹⁵N were lost. Initial decomposition of labelled material was faster in HY than in LY areas during the first year, but the remaining ¹⁵N amounts in POM fractions of the different areas were similar after 570 d. ¹⁵N amounts and concentrations in mineral-associated fractions increased within 160 d after application. From 160 to 570 d, HY and LY areas showed different ¹⁵N dynamics, resulting in a decline of ¹⁵N amounts in HY, but constant ¹⁵N amounts in LY soils. The results indicate faster decomposition processes in HY than in LY areas, due to different soil conditions, such as soil texture and water regime. The higher silt and clay contents of LY areas seem to promote N stabilization in fine mineral fractions. As a whole, N flows were higher in HY compared to LY areas, thus supporting higher yields and accelerated organic matter degradation due to higher N supply.     

Regional variability of volcanic ash soils in south Ecuador: The relation with parent material,climate and land use

The high Andes region of south Ecuador is characterised by intense land use changes. These changes affect particularly the páramo, which is a collection of high altitudinal grassland ecosystems. In this region, the interaction between airborne volcanic ashes and the cold and wet climate results in very typical soils, with an elevated organic C contents. The physical soil properties are closely related to the high and reliable base flow in rivers descending from the páramo, which makes them important for the socio-economic development of the region. In this study, we analyse the regional variability of the soils in the south Ecuadorian rio Paute basin. In a first part of the study, data from soil profiles along north–south transects are used to determine the soil properties, and to relate the spatial variability of these properties to the major trends in parent material, volcanic ash deposits and climate. The profiles are Histic Andosols and Dystric Histosols devoid of allophane, with very high amounts of organic matter. Significant differences between the western and central mountain range are observed, as well as a general decrease in Andic properties from north to south, coinciding with the decrease in volcanic influence. Finally, the impact of human activities on the soil properties is assessed in a case study in the Machangara valley. Data from 5 profiles, located in an area with natural grass vegetation and a low degree of human impact are compared with 4 profiles in a heavily disturbed, intensively drained cultivated area. Despite the intensity of the land use, very few significant differences are found.     

Organic resources and earthworms affect phosphorus availability to sorghum after phosphate rock addition in semi-arid West Africa

A field experiment was laid out in Burkina Faso (West Africa) on an Eutric Cambisol to investigate the interaction of organic resource quality and phosphate rock on crop yield and to assess the contribution of earthworms (Millsonia inermis Michaelsen) to P availability after phosphate rock application. Organic resources of different quality were applied at a dose equivalent to 40 kg N ha^–1 with or without phosphate rock from Kodjari (Burkina Faso) at a dose equivalent to 25 kg P ha^–1, and were compared with control and single phosphate rock treatments in a factorial complete block design with four replicates. Sorghum (Sorghum bicolor L. Moench) variety SARIASSO 14 was grown. Sheep dung had the highest impact on earthworm casting intensity followed by maize straw. Combining organic resources with phosphate rock reduced earthworm casting activities compared to a single application of organic resources or phosphate rock. Addition of phosphate rock to maize straw reduced P availability in earthworm casts whereas combining sheep dung or compost with phosphate rock increased P availability. The contribution of earthworms to Kodjari phosphate rock solubilisation mainly occurred through their casts, as the available P content of casts was 4 times higher than that of the surrounding soil.