Soil degradation and management under intensive sugarcane cultivation in North Queensland

Abstract. Sugarcane yields in the Herbert Valley in North Queensland have been declining over the past 15 years. Better yields are obtained where crops are grown on previously unused land. Soils under cane are more compacted, more acid, contain less organic matter and are lower in cation exchange capacity and exchangeable cations. These differences reflect soil degradation caused by intensive cultivation.
Contributing factors to the degradation of soils include soil compaction and structural breakdown occurring during harvest and cultivation operations, losses of organic matter due to burning of crop residues and acidification of soils due to large applications of nitrogen fertilizers.
Soil management practices should aim to increase soil organic matter levels, provide a more favourable biological environment, reduce physical damage to soils during harvesting and cultivation, reduce soil acidity and improve the effectiveness of fertilizing practices.     

Soil chemical properties of an Indonesian red acid soil as affected by land use and crop management

In the middle terrace area of south Sumatra, Indonesia, where red acid soils poor in crop productivity are widely distributed, the effects of cropping pattern and cultivation techniques on physico-chemical properties of soil were investigated. Five patterns for cassava cropping, including monoculture, a rotation with annual food crops, and three intercroppings with differences in the combination with annual crops and in the planting density, were evaluated in Experiment I. In Experiment II, eight plots composed of the combinations of two tillage methods (no-tillage or conventional tillage), the presence or absence of surface mulch from crop residues, and two rates of chemical fertilizers were established for a maize–soybean–cowpea sequential cropping pattern. At the end of 3 years, there was no difference in total C and total N concentrations among the plots in Experiment I irrespective of the mulch treatment using crop residues. Soil organic matter (SOM) concentration was not affected even in the no-tillage plot where the maximum crop residues (20 t ha⁻¹) was given as surface mulch with the increased root residues due to higher rates of fertilizers (Experiment II). In Experiment I, available P concentration was highest in an intercropping with higher fertilizer rates and lowest cassava planting density. In Experiment II, an increase in available P was attained by mulching and the higher rate of fertilizers, and a minor positive effect of fertilizer was also observed in exchangeable Mg and K concentrations. Surface mulch resulted in less clay fraction compared with the non-mulch plots in both the experiments, suggesting its effect on the maintenance of soil particle distribution. An additional finding suggested no prominent influence of cassava monoculture on the level of SOM in this area based on the comparison with other major land uses, including secondary forest, rubber plantation, and mixed cultivation of fruits with crops. Nevertheless, the introduction of crop residue mulch and higher rates of fertilizers are recommended for sustaining soil quality and achieving higher crop yields.     

不同草田轮作模式对土壤养分动态的影响

在宁南旱区10年生苜蓿草地上进行了为期3a的27种不同草田轮作模式试验,研究了土壤有机质、氮、磷的动态变化特征。结果表明,与保持生长的对照苜蓿草地相比,苜蓿草地实行草田轮作后,有机质持续下降,轮作第1,3a的马铃薯,第2a的春小麦对土壤有机质有明显影响,马铃薯连作模式使土壤有机质降幅最大;不同轮作模式的土壤全氮变化有较大差异,谷子和春小麦等禾本科作物单一连作模式对土壤氮素造成偏耗;不同轮作模式碱解氮总体上呈下降趋势,轮作作物产量水平直接影响土壤碱解氮含量的高低。全磷呈先降后升又降趋势。作物轮作能够提高苜蓿草地土壤氮、磷有效性。为了高效、协调和可持续地利用水肥,应选择合理的草田轮作模式。     

盐化和有机质对土壤结构稳定性及阿特伯格极限的影响

对甘肃景电灌区盐化和有机质对土壤团聚体的稳定性、黏粒的分散性及阿特伯格极限进行了调查研究。研究结果表明该灌区盐化土壤中水溶性盐以钠盐为主,土壤具有钠质现象。随含盐量和交换性钠离子百分率（ESP）的增加土壤团聚体的稳定性显著降低,黏粒的分散性显著增加,阿特伯格极限具有降低的趋势,明确地说明盐化和伴随着的钠质化是土壤结构性能退化的主要原因。随有机质含量的增加,土壤团聚体的稳定性显著增加,黏粒的分散性显著降低,阿特伯格极限显著增加,说明增加有机质含量可以显著改善盐化土壤的结构性能。可以根据如下公式利用有机质含量（OM）和ESP预测团聚体的稳定性:WSAR=19.4 0.98OM-1.43 ESP（R2=0.5741,n=67）。团聚体稳定性、黏粒分散性、流限和塑限互相之间显著相关,说明流限和塑限可以作为反映盐化土壤结构状况的指标。     

Contributions from carbon and nitrogen in roots to closing the yield gap between conventional and organic cropping systems

This study investigates the effect of different crop rotation systems on carbon (C) and nitrogen (N) in root biomass as well as on soil organic carbon (SOC ). Soils under spring barley and spring barley/pea mixture were sampled both in organic and conventional crop rotations. The amounts of root biomass and SOC in fine (250–253 μ m), medium (425–250 μ m) and coarse (>425 μ m) soil particulate organic matter (POM ) were determined. Grain dry matter (DM ) and the amount of N in harvested grain were also quantified. Organic systems with varying use of manure and catch crops had lower spring barley grain DM yield compared to those in conventional systems, whereas barley/pea showed no differences. The largest benefits were observed for grain N yields and grain DM yields for spring barley, where grain N yield was positively correlated with root N. The inclusion of catch crops in organic rotations resulted in higher root N and SOC (g C/m²) in fine POM in soils under barley/pea. Our results suggest that manure application and inclusion of catch crops improve crop N supply and reduce the yield gap between conventional and organic rotations. The observed positive correlation between root N and grain N imply that management practices aimed at increasing grain N could also increase root N and thus enhance N supply for subsequent crops.     

Arbuscular mycorrhizal fungi and soil aggregation in a no‐tillage system with crop rotation

Crop rotation adoption in no‐tillage systems (NTS) has been recommended to increase the biological activity and soil aggregation, suppress soil and plant pathogens, and increase the productivity aiming at the sustainability of agricultural areas. In this context, this study aimed to assess the effect of crop rotation on the arbuscular mycorrhizal fungi (AMF) community and soil aggregation in a soil cultivated for nine years under NTS. Treatments consisted of combinations of three summer crop sequences and seven winter crops. Summer crop sequences consisted of corn (Zea mays L.) monoculture, soybean (Glycine max L. Merrill) monoculture, and soybean–corn rotation. Winter crops consisted of corn, sorghum (Sorghum bicolor (L.) Moench), sunflower (Helianthus annuus L.), sunn hemp (Crotalaria juncea L.), pigeon pea (Cajanus cajan (L.) Millsp.), oilseed radish (Raphanus sativus L.), and millet (Pennisetum americanum (L.) Leeke). Soil samples were collected at a depth of 0–0.10 m for analyses of soil chemical, physical, and biological attributes. Spore abundance, total glomalin, and soil aggregate stability index were higher in the soil under corn monoculture. The highest values of aggregate mean weight diameter were observed in the soybean–corn rotation (3.78 mm) and corn monoculture (3.70 mm), both differing from soybean monoculture (3.15 mm), while winter crops showed significant differences only between sorghum (3.96 mm) and pigeon pea (3.25 mm). Two processes were identified in the soil under summer crop sequences. The first process was observed in PC1 (spore abundance, total glomalin, easily extractable glomalin, pH, P, and Mg²⁺) and was related to AMF; the second process occurred in PC2 (aggregate mean weight diameter, soil aggregate stability index, K⁺, and organic matter) and was related to soil aggregation. The nine‐year no‐tillage system under the same crop rotation adoption influenced AMF abundance in the soil, especially with corn cultivation in the summer crop sequence, which promoted an increased total external mycelium length and number of spores of AMF. In addition, it favored an increased soil organic matter content, which is directly related to the formation and stability of soil aggregates in these managements.     

Inhibition of nitrogen mineralization in young humic fractions by anaerobic decomposition of rice crop residues

Field observations indicate a long‐term decrease in crop uptake of N derived from soil organic matter under continuous production of irrigated lowland rice (Oryza sativa L.). Decreased availability has been associated with an accumulation of phenolic lignin residues in soil organic matter, which can chemically bind N. To evaluate the hypothesis that the decrease in N availability results primarily from anaerobic decomposition of incorporated crop residues, ¹⁵N‐labelled fertilizer was applied three times during one growing season in a field study that compared anaerobic decomposition with aerobic decomposition for annual rotations of rice (Oryza sativa L.)–rice and rice–maize (Zea mays L.). Contents of ¹⁵N and total N during the growing season were measured in humic fractions and total soil organic matter. Results indicated an inhibition of N mineralization for the rice–rice rotation with anaerobic decomposition of crop residues, both for ¹⁵N that was immobilized after application and for total N. The inhibition was strongest for ¹⁵N that was applied at planting. It became more evident as the season progressed and reached significant levels during mid‐season stages of plant growth when crop demand for N peaks. These results were clearest for a young, phenolic‐rich humic fraction that was active in ¹⁵N immobilization and remineralization. Comparable but less significant trends were evident for a more recalcitrant humic fraction and for soil organic matter. Trends in crop‐N uptake associated the combination of rice–rice rotation and anaerobic decomposition with inhibited uptake of soil organic N but uninhibited uptake of fertilizer N. Increased aeration of rice soils through aerobic decomposition of crop residues or crop rotation is a promising management technique for improving soil N supply in lowland rice cropping.     

长期种植苜蓿对土壤氮素营养的作用

13年长期施肥和轮作试验结果表明，连续种植苜蓿时N肥、P肥、有机肥的配合施用(NPM)较单施P肥对提高土壤硝态氮(NO^-₃-N)含量水平有较好效果；而无论施肥与否，种植苜蓿对土壤深层NO^-₃-N均造成不同程度的亏缺。苜蓿(NPM)连作较小麦(NPM)连作土壤NO^-₃-N利用率高；种植苜蓿对土壤铵态氮(NH⁺₄-N)分布影响与NO^-₃-N不同，深层土壤CK、NPM配施处理NH⁺₄-N含量明显高于施P和裸地处理，不同作物种植系统中以苜蓿连作土壤剖面中NH⁺₄-N含量最高。与其他轮作相比，苜蓿连作在提高土壤剖面供N能力方面有较好作用。     

不同种植作物对污灌区土壤铜形态的影响

为弄清在污灌区农田种植玉米、大豆、高粱、向日葵、菊花5种作物对土壤中铜形态的影响,采用Tessier五步连续提取法对种植前后不同形态铜含量进行测定。结果表明:种植5种作物后土壤可交换态铜的含量均有增加,玉米土壤增加率最高,达到25.67%;碳酸盐结合态铜、有机结合态铜含量大致都呈降低趋势,菊花土壤降低率最高,分别达到57.95%和58.6%;铁锰氧化物结合态铜的含量在种植玉米、大豆、向日葵后均有所增加,而种植高粱和菊花后有所降低;残留态铜的含量总体呈降低的趋势。在垂直深度上,可交换态铜的含量在不同土层均表现为增加,其中种植玉米后增加最明显;碳酸盐结合态铜和残留态铜在种植作物后均表现为降低,降低率随土层加深而增加;铁锰氧化物结合态铜和有机结合态铜的变化率在不同土层没有明显的规律性。     

Sources and composition of soil organic matter fractions between and within soil aggregates

It is generally accepted that particulate organic matter derives from plants. In contrast, the enriched labile fraction is thought by many to derive from microbes, especially fungi. However, no detailed chemical characterization of these fractions has been done. In this study, we wanted to assess the sources (plants or microbes; fungi or bacteria) and degree of microbial alteration of (i) three particulate organic matter fractions – namely the free light fraction (1.85 g cm^?3), the coarse (250–2000 μm) and the fine (53–250 μm) intra‐aggregate particulate organic matter fractions – and of (ii) three density fractions of fine‐silt associated carbon – namely < 2.0, 2.0–2.2 (i.e. enriched labile fraction) and > 2.2 g cm^?3– by analysing the amino sugars, by CuO oxidation analyses, and by ¹³C‐, ¹H‐ and ³¹P‐NMR analyses. Macroaggregates (250–2000 μm) were separated by wet‐sieving from a former grassland soil now under a no‐tillage arable regime. The three particulate organic matter fractions and the three density fractions were isolated from the macroaggregates by a combination of density flotation, sonication and sieving techniques. Proton NMR spectroscopy on alkaline extracts showed that the enriched labile fraction is not of microbial origin but is strongly degraded plant material that is enriched in aliphatic moieties partly bound to aromatics. In addition, the enriched labile fraction had a glucosamine content less than the whole soil, indicating that it is not enriched in carbon derived from fungi. Decreasing yields of phenolic CuO oxidation products and increasing side‐chain oxidation in the order coarse intra‐aggregate particulate organic matter < fine inter‐aggregate particulate organic matter < fine‐silt fractions indicate progressive alteration of lignin as particle size decreases. The light fraction was more decomposed than the coarse inter‐aggregate particulate organic matter, as indicated by (i) its larger ratio of acid‐to‐aldehyde of the vanillyl units released by CuO oxidation, (ii) the smaller contribution of H in carbohydrates to total extractable H as estimated by ¹H‐NMR spectroscopy, and (iii) a larger contribution of monoester P to total extractable P in the ³¹P‐NMR spectra. In conclusion, the four fractions are derived predominantly from plants, but microbial alteration increased as follows: coarse inter‐aggregate particulate organic matter < light fraction ≈ fine inter‐aggregate particulate organic matter < enriched labile fraction.     

Soil organic carbon and nitrogen fractions and water‐stable aggregation as affected by cropping and grassland reclamation in an arid sub‐alpine soil

This paper investigates effects of cropping abandonment and perennial grass growing on soil organic C and N pools and aggregate stability, by comparing soils under native grassland, crop cultivation, perennial grass growing and cropping abandonment, in degraded cropland at a sub‐alpine site in north‐western China. The pools of total and particulate organic C (115 and 37 Mg ha⁻¹) in the 0–30 cm soil layer of native grassland were reduced by 31 and 54% after 30 years of crop cultivation. After 4 years of conversion from cropland to perennial grass growing total and particulate organic C pools were increased by 29 and 56%, whereas 4 year cropping abandonment increased particulate organic C by 36%. Rapid increases in total and particulate N were also found in perennial grass growing and cropping abandonment soils. The native grassland soil and soils of cropping abandonment and perennial grass growing had higher carbohydrate C concentrations in the 0–10 cm layer than the cropped soil. The rapid recovery of particulate organic fraction and carbohydrates in the re‐vegetated soils were probably due to higher plant biomass inputs and lower organic matter decomposition compared with those in the cropped soil. Aggregate stability of the 0–30 cm soil layer was significantly decreased by crop cultivation but showed a good recovery after 4 year re‐vegetations. This study suggests that reduction of soil organic matter and aggregate stability under crop cultivation may be remedied by cropping abandonment or perennial grass growing. Copyright © 2008 John Wiley & Sons, Ltd.     

长期不同施肥对旱地红壤性质和作物生长的影响

通过对红壤旱地连续13年定位监测研究,发现在红壤旱地长期坚持有机肥料与无机肥料配合施用,土壤有机质含量逐步提高,土壤有机质从开始的11.5g/kg上升到24.3g/kg,增加的有机质以易氧化的有机质为主,稳定性高的有机质较少。红壤长期施用化学磷,明显提高土壤有效磷含量,土壤供磷性能大为改善,施用有机肥料能减少土壤对磷的固定,提高磷肥的有效性和利用率。红壤长期施用单一化学肥料,土壤明显酸化,土壤交换性氢铝显著增加,作物生长变差,产量降低。施用有机肥料,明显降低土壤交换性氢铝含量,增加土壤养分,保持作物的稳产和高产。     

Influence of current and previous crops on soil basal and potential denitrification rates

Soil and crop management including crop rotation influences available organic carbon and soil nitrate levels, which may in turn affect denitrification losses from soils. The objective of this paper was to determine how the current and previous crop affect denitrification by comparing the basal denitrification rate (BDR), denitrification rate with added nitrate (DAN), and potential denitrification rate (PDR) (amended with glucose and nitrate) of a clay loam soil under monoculture corn (C), soybean (S), and winter wheat (WW) with or without underseeded red clover (RC) and under each phase of a 2-year crop rotation (C-S) and two 3-year crop rotations (C-S-WW, C-S-WW+RC). The BDRs were greater in the 3-year C-S-WW rotation treatments than in the 2-year C-S rotation and monoculture C, S, and WW treatments. The WW+RC phase of the C-S-WW+RC treatment was found to have a greater BDR and DAN than the corn phase of the rotation. Available organic carbon was found to limit denitrification in the BDR and DAN incubations as evidenced by the 2- to 21-fold increase in denitrification when glucose was added in the PDR assay. Further, the significant relationship between soil respiration and BDR suggests that available carbon was a limiting factor. This study found that both the current crop and previous crops in a rotation affected soil denitrification rates substantially; and that denitrification rate was increased when a mixture of crop residues were added to soil (i.e., from growing crops in rotation) relative to when only a single residue was added (i.e., monoculture cropping).     

Soil carbon as affected by cover crops under no‐till under tropical climate

In tropical, low‐fertility soils, crop yields are dependent on soil carbon, and cropping systems under no‐till can increase soil C stocks. Plant residues supplied by cover crops in no‐till systems may improve aggregate stability and soil carbon, which may be further increased with the introduction of a legume in the cropping system. This research studied the effects of cover crops in rotation with soybean under no‐till on soil carbon and nitrogen, in Botucatu, Brazil, for 3 yr. The cover crops were millet (Penninsetum americanum Leek), cober crop (Sorghum bicolor × Sorghum sudanense) and sunn hemp (Crotalaria juncea L.), grown in the spring. Fallow without cover crops was used as a control. Grain sorghum (Sorghum bicolor L. Moench) and soybean (Glycine max (L.) Merril) were grown in fall–winter and summer, respectively. Generally, cover crops increased soil carbon contents, but soil N was only increased by sunn hemp in the particulate organic C fraction. An increase in the labile carbon fraction in the topsoil layers was closely related to cover crop root development. Fallow in spring should not be recommended in degraded soils with lowcarbon stock. Labile‐fractioned soil organic carbon and total carbon levels are more efficiently increased by grasses than by legumes in the short term, and grasses cropped in spring increase soil C/N ratio. Conversely, the introduction of a legume (sunn hemp) maintained a more stable C/N ratio, that is around 10, which would be more effective in increasing soil C in the long term.     

Increased rice yield in long-term crop rotation regimes through improved soil structure,rhizosphere microbial communities,and nutrient bioavailability in paddy soil

Soil in short-term crop rotation systems (STCR) is still in the initial development stage of farmland soil, whereas after long-term crop rotation treatment (LTCR), soil properties are significantly different. This study compares STCR (4 years) and LTCR (30 years) rice-rice-fallow, rice-rice-rape rotation practices under the same soil type background and management system. To reveal ecosystem mechanisms within soils and their effects on rice yield following LTCR, we analyzed the physical, chemical, and microbiological properties of soils with different rotations and rotation times. Relative to STCR, LTCR significantly reduced soil water-stable aggregate (WSA) content in the <?0.053-mm range, while >?2 mm WSA content significantly increased. Soil organic matter increased in fields under LTCR, mainly in >?2 mm, 2–0.25 mm, and <?0.053 mm soil WSA in 0–10 cm soil layer. LTCR was associated with significantly increased total soil organic matter, at the same time being associated with increasing the amount of active organic matter in the 0–20 cm soil layer. The two crop rotation regimes significantly differed in soil aggregate composition as well as in soil N and P, microbial biomass, and community composition. Relative to STCR, LTCR field soils had significantly higher soil organic matter, active organic matter content, soil enzyme activities, and overall microbial biomass, while soil WSA and microbial community composition was significantly different. Our results demonstrate that LTCR could significantly improve soil quality and rice yield and suggest that length of rotation time and rice-rice-rape rotation are critical factors for the development of green agriculture.     

Impact of sugarcane cultivation on soil carbon fractions, consistence limits and aggregate stability of a Yellow Latosol in Northeast Brazil

The effects of continuous sugarcane (Saccharum officinarum) cropping on the properties of a cohesive Yellow Latosol were studied in the region of the Coastal Tablelands, Northeast Brazil. Four areas were studied at Caeté mill, municipality of São Miguel dos Campos, Alagoas State, involving a native forest (Tn), and sugarcane fields cultivated for periods of 2 years (T2), 18 years (T18) and 25 years (T25). Samples were collected from each area at 0–0.2 and 0.2–0.4 m depth, to determine total organic C, physical fractionation of soil organic matter and consistence limits. Undisturbed samples were collected to determine wet aggregate mean weight–diameter, dry mean weight diameter and aggregate stability. In relation to the soil under native forest, total organic C and particulate organic matter contents were reduced after 2 years of cultivation. Sugarcane cropping for a longer period promoted a recuperation of soil organic matter content. The decrease of total organic C and reduction in aggregate stability and plastic limit after 2 years of sugarcane cultivation rendered the soil more susceptible to compaction.     

N-utilization by maize (Zea mays L.) as influenced by crop rotation and field pea (Pisum sativum L.) residue management

Abstract. A five year field experiment was conducted to assess the influence of crop rotation and field pea residue incorporation into the soil on maize yield. The data indicated a 30% increase in maize yield grown in rotation with field pea compared to when it was grown after wheat and a further increase of 35% when field pea residues were incorporated into the soil. The effect of field pea and residue incorporation was greater in the presence of fertilizer nitrogen indicating the enhanced capacity of the crop to utilize N from the residue. Legume residue management in sub-tropical regions of the world, having coarse textured soils low in organic matter, could help to increase the yield of cereals besides saving some of the expensive fertilizer input.     

Soil physical fertility, soil structure and rooting conditions after ploughing organically managed grass/clover swards

Effective management of soil structure and organic matter are essential in organic cropping to ensure good rooting conditions and to optimize the production of mineralized N and thus minimize greenhouse gas emissions. We investigated how mid‐winter or early spring ploughing and three grazing duration treatments prior to ploughing influenced soil structure, soil organic matter and plant root growth under the first spring barley crop after a grass–clover ley. The experiment was carried out over two seasons. We also studied the soil under first‐year oats in a long‐term rotations experiment where 2 or 3 years of arable crops followed 3 or 4 years of grass. Pore size distribution and pore continuity, bulk density, particulate (light fraction) organic matter, readily oxidizable organic matter (ROM), aggregate size distribution and root length densities were measured. Macroporosity appeared to be the best indicator of soil physical fertility; it was sensitive to changes in soil structure arising from compaction and root growth. This, along with visual examination, revealed the loosening resulting from ploughing. The generally favourable macroporosity amongst small, stable aggregates reduced the likelihood of development of anaerobism. Macroporosity and aggregate size can be estimated from visual examination of the soil, a method that offers the advantage of being quick and of sampling a large volume. The content of ROM was high 6.1–6.4 g 100 g^?1 whole soil. However, particulates formed only a small fraction (6–9%) of the ROM. Despite the favourable ROM and structure, the soil was susceptible to compaction damage during seedbed preparation in wet soil after ploughing which reduced grain yield in some plots. Grazing by sheep before ploughing and date of ploughing had minor effects on soil quality. Grazing for 2 months prior to ploughing increased root length density in the upper topsoil in the following arable crop, possibly because of the higher quality of the animal and grass–clover residues. Conservation of soil quality was related more to secondary tillage and sowing operations after ploughing than to duration and timing of grazing.     

黑土颗粒有机碳和氮含量对有机肥剂量响应的定量关系

黑土是一种非常重要的耕种土壤,但是由于过度地开发利用和水土流失导致土壤有机质含量迅速下降,严重影响了耕地生产力和作物产量。为了能够快速恢复黑土肥力,利用海伦国家野外科学观测研究站内的长期定位试验,定量分析了黑土颗粒有机碳和氮含量对有机肥剂量的响应。田间试验开始于2001年,设置了4个施肥处理,分别为:1单施化肥(OM0);2低剂量有机肥与化肥配施(OM1);3中剂量有机肥与化肥配施(OM2);4高剂量有机肥与化肥配施(OM3)。在2011年播种前,采集各处理0~20 cm耕层土壤样品。应用有机碳物理分组方法,测定分析了土壤有机碳、氮及各组分的含量。研究结果表明长期不同剂量有机肥输入能够显著增加黑土总有机碳和全氮含量(P0.05),每增施1 t有机肥,土壤有机碳含量增加0.186 kg,土壤全氮含量增加0.02 kg,表明增加有机肥投入量是提高黑土有机碳含量的有效措施。有机肥的施用增加了土壤中粗颗粒和细颗粒组分,不同剂量有机肥处理表现为OM3OM2OM1OM0,而减小了土壤中矿质结合态组分的含量;随着有机肥施入量的增加,粗颗粒和细颗粒土壤有机碳和氮的含量呈增加的趋势,而矿质结合态中的有机碳含量则略有下降,表明粗颗粒和细颗粒有机碳和氮是黑土有机碳和氮的主要储存库,有机无机配施对土壤有机碳、氮的提升作用主要集中于对活性组分颗粒有机质的形成和积累。与OM0处理相比,有机肥的施入显著降低了颗粒有机质和矿质结合态有机质的C/N,并且随着有机肥施入量的增加而逐渐降低。与单施化肥相比,化肥有机肥配施能够显著增加土壤的总有机碳,全氮,颗粒有机碳、氮含量,其中以化肥配施高剂量有机肥效果最佳,有利于黑土土壤肥力的快速提升,改善黑土的土壤质量。     

崩岗红土层土壤液塑限特性及影响因素研究

土壤液塑限可以反映土壤的入渗、抗冲、抗蚀和抗剪等情况,对崩岗的水土流失研究有重要的意义。通过对崩岗红土层土壤的液塑限研究以及颗粒分析和有机质测定,分析土壤有机质含量和土壤颗粒分布对土壤液塑限的影响。结果表明:崩岗红土层土壤为高液限黏土,土壤状态为坚硬;土壤液塑限值与粗砂粒、细砂粒和粉粒含量相关性不明显,与极细砂粒和黏粒含量呈二项式关系,其中极细砂粒含量与土壤液塑限呈负相关;黏粒含量与土壤液塑限均呈显著正相关关系,且模拟的方程可以较准确地描述土壤液塑限和各因素的相关关系。研究结果有利于丰富崩岗侵蚀机理的研究。