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951.
Soil organic matter, microbial biomass and enzyme activities in a tropical agroforestry system 总被引:14,自引:0,他引:14
The effects of growing trees in combination with field crops on soil organic matter, microbial biomass C, basal respiration
and dehydrogenase and alkaline phosphatase activities were studied in soils under a 12-year-old Dalbergia sissoo (a N2-fixing tree) plantation intercropped with a wheat (Triticum aestivum) – cowpea (Vigna sinensis) cropping sequence. The inputs of organic matter through D. sissoo leaf litter increased and crop roots decreased with the increase in tree density. Higher organic C and total N, microbial
biomass C, basal soil respiration and activities of dehydrogenase and alkaline phosphatase were observed in treatments with
tree-crop combination than in the treatment without trees. Soil organic matter, microbial biomass C and soil enzyme activities
increased with the decrease in the spacing of the D. sissoo plantation. The results indicate that adoption of the agroforestry practices led to an improved organic matter status of
the soil, which is also reflected in the increased nutrient pool and microbial activities necessary for long-term productivity
of the soil. However, tree spacing should be properly maintained to minimize the effects of shading on the intercrops.
Received: 21 February 1997 相似文献
952.
Soil microbial biomass and nitrogen supply in an irrigated lowland rice soil as affected by crop rotation and residue management 总被引:5,自引:0,他引:5
C. Witt Kenneth G. Cassman Johannes C. G. Ottow Ulrich Biker 《Biology and Fertility of Soils》1998,28(1):71-80
Processes that govern the soil nitrogen (N) supply in irrigated lowland rice systems are poorly understood. The objectives
of this paper were to investigate the effects of crop rotation and management on soil N dynamics, microbial biomass C (CBIO) and microbial biomass N (NBIO) in relation to rice N uptake and yield. A maize-rice (M-R) rotation was compared with a rice-rice (R-R) double-cropping
system over a 2-year period with four cropping seasons. In the M-R system, maize (Zea mays L.) was grown in aerated soil during the dry season (DS) followed by rice (Oryza sativa L.) grown in flooded soil during the wet season (WS). In the R-R system, rice was grown in flooded soil in both the DS and
WS. Three fertilizer N rates (0, 50 or 100 kg urea-N ha–1 in WS) were assigned to subplots within the cropping system main plots. Early versus late crop residue incorporation following
DS maize or rice were established as additional treatments in sub-subplots in the second year. In the R-R system, the time
of residue incorporation had a large effect on NO3
–-N accumulation during the fallow period and also on extractable NH4
+-N, rice N uptake and yield in the subsequent cropping period. In contrast, time of residue incorporation had little influence
on extractable N in both the fallow and rice-cropping periods of the M-R system, and no detectable effects on rice N uptake
or yield. In both cropping systems, CBIO and NBIO were not sensitive to residue incorporation despite differences of 2- to 3-fold increase in the amount of incorporated residue
C and N, and were relatively insensitive to N fertilizer application. Extractable organic N was consistently greater after
mid-tillering in M-R compared to the R-R system across N rate and residue incorporation treatments, and much of this organic
N was α-amino N. We conclude that N mineralization-immobilization dynamics in lowland rice systems are sensitive to soil aeration
as influenced by residue management in the fallow period and crop rotation, and that these factors have agronomically significant
effects on rice N uptake and yield. Microbial biomass measurements, however, were a poor indicator of these dynamics.
Received: 31 October 1997 相似文献
953.
羊草草原群落初级生产力动态研究 总被引:7,自引:0,他引:7
在锡林郭勒盟南部羊草草原对群落初级生产力动态进行11年的定位研究,结果表明:群落地上生物量有着显著的波动,在11年中遇丰年3个、平年7个、欠年1个。群落地上生物量季节积累动态符合Compertz曲线Bt=Bmax·e-ea-kt,其高峰值出现在返青后的125.2~162.7天。制约群落地上生物量波动的限制因素是水分条件。建立了群落地上生物量与水热因子关系的数学模型。根据这些规律作者对畜牧业生产提出了合理建议。 相似文献
954.
中国生物质能的利用状况及展望 总被引:20,自引:2,他引:18
概述了中国生物质能的来源,分析了国内外生物质能的利用现状.根据实际情况,提出中国生物质能的发展方向。 相似文献
955.
Enzyme activities play an important role for the transformation of elements and compounds in soil and, thus, were extensively analyzed for more than 4 decades. The activity of any enzyme in soil may not only be controlled by active organisms. Substantial parts of ‘extracellular’ enzymes may be stabilized by abiotic soil components maintaining their activity. Methods to discriminate the source of enzyme activity were summarized with emphasis on the approach plotting enzyme activity versus a feature integrating the microbial biomass after the addition of glucose and nitrate. Considering the quotient between enzyme activity and microbial biomass content, protease activity will be discussed with reference to nitrogen transformation in soils. 相似文献
956.
该文对桐麦间作系统中小麦各部分生物量进行了研究,结果表明系统内外小麦种子生物量差异显著,系统外的小麦生物量高于系统内;同一间作模式内生物量分布受距树行远近影响,处于模式中央的小麦各部分生物量都是最大的;影响小麦生物量的主要因子为小麦品种和穗密度,间作模式和距树行远近对小麦种子生物量有一定影响,但对小麦总生物量影响较小.桐麦间作系统内外小麦种子单穗生物量的差异较总生物量的差异小;影响小麦种子单穗生物量的主要因子为小麦品种,其次为距树行远近,而间作模式和小麦穗密度对其影响甚小;不同小麦品种对环境条件要求不一致,在桐麦间作系统麦田东边,豫西832各部分生物量都有比西边减小的趋势,秸秆生物量平均减少5%;矮早各部分的生物量都有比西边增大的趋势,秸秆生物量平均增大6.5%,小麦种子生物量平均增大3.5%. 相似文献
957.
The regeneration of natural vegetation (fallowing) is a traditional practice for restoring fertility of agricultural land in many parts in the tropics. As a result of increasing human population and insufficient fertilizer inputs, the ecosystem fertility functions of traditional fallows must now be improved upon via the use of managed fallows. Interactions between vegetation and soil determine nutrient losses and gains in crop—fallow systems and are influenced by fallow species, patterns and rates of biomass allocation, and crop and fallow management. Nutrient losses occur through offtake in crop harvests during the cropping phase and through leaching, runoff, and erosion in the cropping phase and the initial stage of fallows $#x2014; when nutrient availability exceeds nutrient demand by vegetation. Gains in nutrient stocks in later stages of fallow are generally more rapid on soils with high than low base status due to greater quantities of weatherable minerals and lack of constraints to N2 fixation, deep rooting, and retrieval of subsoil nutrients by fallow vegetation. On low base status soils (exchangeable Ca < 1 cmolc kg–1), N2 fixation and atmospheric inputs are likely to be the main sources of nutrient additions. On high base status soils limited by N, gains in N stocks by inputs from N2 fixation and retrieval of subsoil nitrate can occur relatively rapidly; hence short-term fallows can often improve crop performance. Large losses of Ca associated with soil organic matter (SOM) mineralization and soil acidification during cropping and fallow establishment, combined with chemical barriers to root penetration, suggest that long-duration fallows (> 5 yr) are needed for recovery of cation stocks and crop performance on low base status soils. On both soils, however, residual benefits of fallows on crop yields usually last less than three crops.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
958.
Four shrub/tree species, Alchornea cordifolia, Pennisetum purpureum, Chromolaena odorata, and Calliandra calothyrsus were
evaluated for their potential contribution to soil fertility restoration after two years fallow. Standing biomass, root distribution,
nutrient content in the biomass, decomposition and nutrient release patterns, and association with mycorrhizae were the evaluation
parameters. Alchornea and Pennisetum produced thehighest above-ground biomass, 66 t and 54 t/ha respectively. Pennisetum had
more than 19 t/ha of root, 92% of which was in the 20 cm top soil. Alchornea had 74% of it roots in this soil layer, mostly
as coarse roots while Calliandra had a deeper root system. Alchornea fallow accumulated more N and Ca, and Pennisetum fallow,
more K than others, and mycorrhizae were mostly associated with Alchornea roots. The ranking of the different species for
the decomposition rate was: Chromolaena > Pennisetum > Calliandra = Alchornea. Also release of nutrients during decomposition
followed the order K > N > Ca. Alchornea and Pennisetum could be recommended as green manure species especially when high
quantities of material are needed for weed or erosion control. Calliandra and Chromolaena, because of the flush of nutrient
during early mass, loss can be used as mulch when the crop demand of nutrient is high. Alchornea decomposed slowly and therefore
could be used to improve Chromolaena mulch, thus contributing to the build up of soil organic N and providing both short-
and long-term nutrient release.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
959.
960.
L. Leita M. De Nobili C. Mondini G. Muhlbachova L. Marchiol G. Bragato M. Contin 《Biology and Fertility of Soils》1999,28(4):371-376
We studied the long-term effects (12 years) of municipal refuse compost addition on the total organic carbon (TOC), the amount
and activity of the microbial biomass (soil microbial biomass C, BC and metabolic quotient qCO2) and heavy metal bioavaiability in soils as compared to manuring with mineral fertilizers (NPK) and farmyard manure (FYM).
In addition, we studied the relationships between among the available fraction [Diethylenetriaminopentacetic acid (DTPA) extractable]
of heavy metals and their total content, TOC and BC. After 12 years of repeated treatments, the TOC and BC of control and mineral fertilized plots did not differ. Soils treated with FYM and composts showed a significant increase
in TOC and BC in response to the increasing amounts of organic C added. Values of the BC/TOC ratio ranged from 1.4 to 2, without any significative differences among soil treatments. The qCO2 increased in the organic-amended soil and may have indicated microbial stress. The total amounts of metals in treated soils
were lower than the levels permitted by the European Union in agricultural soils. DTPA-extractable metals increased in amended
soils in response to organic C. A multiple regression analysis with stepwise selection of variables was carried out in order
to discriminate between the influence exerted on DTPA-extractable metals by their total content, TOC and BC. Results showed that each metal behaved quite differently, suggesting that different mechanisms might be involved in metal
bioavailability
Received: 31 October 1997 相似文献