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1.
This study investigated long‐term effects of soil management on size distribution of dry‐sieved aggregates in a loess soil together with their organic carbon (OC) and their respiratory activity. Soil management regimes were cropland, which was either abandoned, left bare fallow or cropped for 21 yr. Abandonment increased the abundance of macroaggregates (>2 mm) in the surface soil layer (0–10 cm) and reduced that of microaggregates (<0.25 mm) relative to Cropping, whereas the Fallow treatment reduced the abundance of macroaggregates at depths of 0–10 and 10–20 cm. All treatments yielded similar aggregate size distributions at a depth of 20–30 cm. The SOC content of aggregate size fractions in the surface soil from the Abandoned plots was greater (by 1.2–4.8 g/kg) than that of the corresponding fractions from the Cropped plots, but the opposite trend was observed in the subsurface soils. Conversely, the Fallow treatment reduced the SOC content of every aggregate size fraction. Smaller aggregates generally exhibited greater cumulative levels of C mineralization than larger ones. However, the bulk of the SOC losses from the soils via mineralization was associated with aggregates of >2 mm. Abandonment significantly increased the relative contribution of macroaggregates (>2 mm) to the overall rate of SOC loss, whereas the Fallow treatment significantly reduced the contribution of 0.25–2 mm aggregates to total SOC loss in the surface soil while substantially increasing their contribution in the subsurface soil.  相似文献   

2.
Conservation tillage has been applied in vast semi‐arid regions of the Guanzhong Plain, Northwest China. The tillage effects on soil aggregation, organic carbon (OC) stabilization and grain yield on this plain have not been fully elucidated. A 9‐year field experiment was established from 2002 on a silty clay loam soil (Eum‐Orthic Anthrosol) growing winter wheat–maize in a double‐cropping system. Six conservation tillage treatments were applied by different combinations of rotary tillage (RT), subsoiling (SS) and no‐till (NT), with or without finely chopped straw retention. Conventional tillage (CT) acted as the control. Results showed that in the surface (0–10 cm) soil, the proportion of water‐stable aggregates (WSA) <0.05 mm was 18% less while that for WSA >2 mm was 98% more under NT treatments compared with CT. Additionally, the oxidizable OC content in WSA 0.25–2 mm was 27% greater under NT treatments compared with CT. The OC stocks increased under SS by 17%, RT by 16% and NT by 15% relative to CT. Grain yield (wheat + maize) showed similar increasing trends in all the tillage treatments compared with CT. Both OC stocks and grain yield were larger in treatments with than without straw retentions. These results indicate that NT is beneficial for OC accumulation in WSA but is limited in its ability to improve soil structure in this region. SS plus straw retention (fine‐chopped or as a mulch) is an effective practice to improve soil structural stability, OC accumulation and soil productivity of Eum‐Orthic Anthrosols in Northwest China.  相似文献   

3.
Drought has significant effects on soil physicochemical properties and thereby crop productivity. Intercropping is a traditional agricultural practice with a good ecological effect and can improve soil structure. However, the effects of intercropping on soil aggregate distribution and associated organic carbon (OC) and nitrogen (N) compared with monoculture under drought remains unclear. Therefore, a two-year controlled rainfall field (i.e., 30–40 days of 100% rainfall reduction during crop growth) was carried out to examine the effects of intercropping and short-term drought on soil aggregate stability and associated OC and N in Northeast China. Results showed that soil OC and N were predominant in macroaggregates (2–0.25 mm), accounting for 39%–51% of SOC, 36%–51% of N at 0–10 cm depth, and 44%–67% of SOC, 43%–66% of N at 10–20 cm depth. After 2 years of a rainfall reduction treatment, large macroaggregates (>2 mm) increased by 84.7% at 0–10 cm and the aggregate stability improved. There was no difference in the mass of aggregates between monoculture and intercropping, but short-term drought increased >0.25 mm aggregates and stability in intercropping soil at 0–10 cm depth. Moreover, drought significantly increased bulk soil OC in 10–20 cm but decreased the OC and N concentrations in large macroaggregates and silt + clay fractions (<0.053 mm) in 0–10 cm. Compared with the monoculture, intercropping enhanced OC and N concentrations in aggregates, and decreased soil C/N ratio. Therefore, these findings provide insights into how intercropping and short-term drought interactively influence soil aggregation, and C and N processes.  相似文献   

4.
Effects of two tillage treatments, tillage (T) with chisel plough and no-till (NT), were studied under un-drained and drained soil conditions. Soil physical properties measured were bulk density (ρb), total porosity (ƒt), water stable aggregates (WSA), geometric mean diameter (GMD), mean weight diameter (MWD), organic carbon (OC) and total N concentrations in different aggregate size fractions, and total OC and N pools. The experiment was established in 1994 on a poorly drained Crosby silt loam soil (fine mixed, mesic, Aeric Ochraqualf) near Columbus, Ohio. In 2007, soil samples were collected (0–10, 10–20, and 20–30 cm) from all treatments and separated into six aggregate size classes for assessing proportions of macro (5–8, 2–5, 1–2, 0.5–1, 0.25–0.5) and micro (<0.25 mm) aggregates by wet sieving. Tillage treatments significantly (P ≤ 0.05) influenced WSA, MWD, and GMD. Higher total WSA (78.53 vs. 58.27%), GMD (0.99 vs. 0.68 mm), and MWD (2.23 vs. 0.99 mm) were observed for 0–10 cm depth for NT than T treatments. Relative proportion of macro-aggregates (>0.25-mm) was also more in NT than T treatment for un-drained plots. Conversely, micro-aggregates (<0.25-mm) were more in T plots for both drained and un-drained treatments. The WSA, MWD and GMD decreased with increase in soil depth. The OC concentration was significantly higher (P ≤ 0.05) in NT for un-drained (P ≤ 0.01) treatment for all soil depths. Within macro-aggregates, the maximum OC concentrations of 1.91 and 1.75 g kg−1 in 1–2 mm size fraction were observed in NT for un-drained and drained treatments, respectively. Tillage treatments significantly (P < 0.01) affected bulk density (ρb), and total porosity (ft) for all soil depths, whereas tillage × drainage interaction was significant (P < 0.01) for 10–20 and 20–30 cm depths. Soil ρb was negatively correlated (r = −0.47; n = 12) with OC concentration. Tillage treatments significantly affected (P ≤ 0.05) OC pools at 10–20 cm depth; whereas drainage, and tillage × drainage significantly (P ≤ 0.05) influenced OC pools for 0–10 cm soil layer. The OC pool in 0–10 cm layer was 31.8 Mg ha−1 for NT compared with 25.9 Mg kg−1 for T for un-drained treatment. In comparison, the OC pool was 23.1 Mg ha−1 for NT compared with 25.2 Mg ha−1 for T for the drained plots. In general, the OC pool was higher in NT system, coupled with un-drained treatment than in drained T plots. The data indicate the importance of NT in improving the OC pool.  相似文献   

5.
Paddy soils in subtropical China are usually deficient in phosphorus (P) and require regular application of chemical fertilizers. This study evaluated the effects of chemical fertilizers on the distribution of soil organic carbon (SOC), total nitrogen (N) and available P, and on the activity of the associated enzymes in bulk soil and aggregates. Surface soils (0–20 cm) were collected from a 24‐yr‐old field experiment with five treatments: unfertilized control (CK), N only (N), N and potassium (NK), N and P (NP), and N, P and K (NPK). Undisturbed bulk soils were separated into >2, 1–2, 0.25–1, 0.053–0.25 and <0.053 mm aggregate classes using wet sieving. Results showed that both NP‐ and NPK‐treated soils significantly increased mean weight diameter of aggregates, SOC, available P in bulk soil and aggregates, as compared to CK. Most SOC and total N adhered to macro‐aggregates (>0.25 mm), which accounted for 64–81% of SOC and 54–82% of total N in bulk soil. The activities of invertase and acid phosphatase in the 1–2 mm fraction were the highest under NPK treatment. The highest activity of urease was observed in the <0.053 mm fraction under NP treatment. Soil organic carbon and available P were major contributors to variation of enzyme activities at the aggregate scale. In conclusion, application of NP or NPK fertilizers promoted the formation of soil aggregates, nutrient contents and activities of associated enzymes in P‐limited paddy soils, and thus enhanced soil quality.  相似文献   

6.
Abstract

The effect of organic manure and inorganic fertilizer on soil aggregate size distribution and stability, and associated carbon (C) within aggregates varies greatly in previous studies because of the differences in soil conditions, cropping systems, and management practices. This study was conducted as two field fertilization experiments, with different cropping systems, under a subtropical climate in China. The two field experiment sites were located in Jinhua (established in April 2011) in the Jinqu basin in Zhejiang province and Jintan (established in October 2010) in the low-middle Yangtze River plain in Jiangsu province. Both experiments consisted of four treatments, including unfertilized (CK), mineral fertilizer nitrogen (N)–phosphorus (P)–potassium (K) (NPK), NPK plus straw (NPK?+?SR), and NPK plus cattle manure (NPK?+?FYM) or half NPK plus cattle manure (1/2NPK?+?FYM). Water stable aggregate size classes (>5, 2–5, 1–2, 0.5–1, 0.25–0.5, and <0.25?mm) and associated soil organic C (SOC) at 0–15?cm depth were measured. The mean weight diameter (MWD), geometric mean diameter (GMD), and water stable aggregates (WSA)?>?0.25?mm were also determined. The results showed that aggregate-size distribution varied with soil types. Combined application of NPK and organic matter (straw residue or cattle manure), unlike the CK and NPK treatments, significantly increased the WSA >0.25?mm, MWD, and GMD, while obviously reducing the proportion of <0.25?mm aggregates. However, no differences in WSA >0.25?mm, MWD, GMD, and associated C were observed between CK and NPK at both sites. The addition of FYM to the NPK treatment yielded the highest SOC contents in bulk soil, and showed significantly higher associations of C within all size aggregates at both sites. In contrast, NPK?+?SR significantly increased SOC within aggregate classes (2–5?mm, 0.5–1?mm, 0.25–0.5?mm, and <0.25?mm) at Jinhua and (>5?mm and 1–2?mm) at Jintan compared to the CK and NPK treatments. Overall, the combined application of FYM and mineral NPK was the best sustainable management practice for the improvement of aggregate stability and SOC sequestration.  相似文献   

7.
The association of organic carbon with secondary particles (aggregates) results in its storage and retention in soil. A study was carried out at a catchment covering about 92 km2 to predict spatial variability of soil water-stable aggregates (WSA), mean weight diameter (MWD) of aggregates and organic carbon (OC) content in macro- (> 2 mm), meso- (1-2 mm), and micro-aggregate (< 1 mm) fractions, using geostatistical methods. One hundred and eleven soil samples were collected at the 0-10 cm depth and fractionated into macro-, meso-, and micro-aggregates by wet sieving. The OC content was determined for each fraction. A greater percentage of water-stable aggregates was found for micro-aggregates, followed by meso-aggregates. Aggregate OC content was greatest in meso-aggregates (9 g kg?1), followed by micro-aggregates (7 g kg?1), while the least OC content was found in macro-aggregates (3 g kg?1). Although a significant e?ect (P = 0.000) of aggregate size on aggregate OC content was found, however, our findings did not support the model of aggregate hierarchy. Land use had a significant e?ect (P = 0.073) on aggregate OC content. The coe?cients of variation (CVs) for OC contents associated with each aggregate fraction indicated macro-aggregates as the most variable (CV = 71%). Among the aggregate fractions, the micro-aggregate fraction had a lower CV value of 27%. The mean content of WSA ranged from 15% for macro-aggregates to 84% for micro-aggregates. Geostatistical analysis showed that the measured soil variables exhibited di?erences in their spatial patterns in both magnitude and space at each aggregate size fraction. The relative nugget variance for most aggregate-associated properties was lower than 45%. The range value for the variogram of water-stable aggregates was almost similar (about 3 km) for the three studied aggregate size classes. The range value for the variogram of aggregate-associated OC contents ranged from about 3 km for macro-aggregates to about 6.5 km for meso-aggregates. Kriged maps of predicted WSA, OC and MWD for the three studied aggregate size fractions showed clear spatial patterns. However, a close spatial similarity (co-regionalization) was observed between WSA and MWD.  相似文献   

8.
ABSTRACT

Field experiment was conducted to evaluate the effect of corn straw derived-biochar (700 °C) applied at 0 (control), 10 (B1), 20 (B2) and 30 t ha?1 (B3) on water stable aggregate (WSA), mean weight diameter (MWD), total organic carbon (TOC) and total nitrogen (TN) in WSA fractions of Albic soil. Compared with control, WSA in > 2 mm fraction increased, by 40.8% and 51.5% (0–10 cm depth) in B1 and B3, respectively. B1, B2 and B3 (10–20 cm depth) increased by 55.2%, 69.6% and 62.4%, respectively. MWD increased by 34.4%, 21.6%, and 17.6% with B3 at 0–10 cm, 10–20 cm and 20–30 cm depths, respectively. TOC in the > 2 mm fraction increased by 28.6%, 22.1%, and 23.2% (0–10 cm depth) in B1, B2, and B3, respectively, TN in 2–0.5 mm fractions increased by 32.4%, 23.4% and 33.6% (0–10 cm depth); and in the 0.25–0.05 mm fractions increased by 14.8%, 19.8% and 18.7% (10–20 cm depth), in B1, B2 and B3, respectively. Our findings suggest biochar application at 30 t ha?1 could improve structural stability and sequestration of TOC and TN in Albic soils.  相似文献   

9.
The 4‐year application of pig‐manure compost (PMC) to crop fields in Jiangsu significantly increased organic‐C and total N concentrations compared to chemical fertilization and control treatment. To identify the soil processes that led to these changes, 13C cross‐polarization magic‐angle spinning nuclear‐magnetic resonance (13C CPMAS NMR) and dipolar‐dephasing nuclear‐magnetic‐resonance spectroscopy (DD NMR) were conducted on soil organic matter (SOM) fractions separated by wet‐sieving and density fractionation procedures. This allowed characterization of the SOM quality under three contrasting fertilizer regimes. The results indicate that PMC application can alter the distribution of functional groups and improve alkyl C‐to‐O‐alkyl C ratios compared to chemical‐fertilizer treatment (CF). Alkyl C contents were increased from macroaggregate fractions (> 2 mm) to microaggregate fractions (0.05–0.25 mm) for all treatments, suggesting that recalcitrant material accumulates in the microaggregate fractions. The O‐alkyl C contents were decreased from macroaggregate fractions (> 2 mm) to microaggregate fractions (0.05–0.25 mm) under CF and PMC treatments, while no consistent trend was found for the control (NF) treatment. The alkyl C‐to‐O‐alkyl C ratios in macroaggregates were lower than those in microaggregates, indicating that the degrees of SOM decomposition were lower in macroaggregates compared to microaggregates. In all aggregate‐size classes, the amount of organic matter appeared to depend on the fertilization regime. This study provides useful information regarding the buildup of organic material in soil from long‐term manure‐compost enrichment.  相似文献   

10.
This study evaluated carbon and nutrient distributions within water-stable aggregates (WSA) of soils of two contrasting ecosystems under different land uses. Surface soil samples were collected from uncultivated and cultivated land in rainforest and savannah agro-ecological areas and separated by wet-sieving technique into 4.76–2.0, 2.0–1.0, 1.0–0.50, 0.50–0.25 and <0.25 mm aggregate fractions. The results show that irrespective of the agro-ecological area, cultivation significantly (p < 0.05) reduced the macroaggregate fractions (>0.25 mm) to smaller diameters. Distribution of organic carbon (C), total nitrogen (N) and available phosphorus (P) within the WSA showed preferential enrichment of these elements in the large macroaggregate fraction (4.76–2.0 mm) for the uncultivated soils and microaggregate fraction (<0.25 mm) for the cultivated soils. The overall pattern indicates higher accumulation of C, N and P in the WSA of the uncultivated soils over the cultivated soils. Average distribution of total exchangeable bases (TEB), i.e., sum of Ca2+, Mg2+, K+ and Na+, within WSA of the uncultivated soils of the rainforest region were 7.35 and 7.39 cmol/kg for 4.76–2.0 and <0.25 mm fractions, respectively. The distributions of TEB for cultivated soils of the rainforest region were 2.76 cmol/kg (4.76–2.0 mm fraction) and 7.73 cmol/kg for <0.25 mm fraction. This showed that cultivation significantly (p < 0.05) led to 62% reduction in these nutrients in the 4.76–2.0 mm fraction and 5% increase in concentrations of these cations in <0.25 mm fraction. For savannah soils, distributions of TEB were 7.44 and 6.77 cmol/kg for 4.76–2.0 and <0.25 mm fractions, respectively, in uncultivated sites, whereas TEB were 2.19 cmol/kg (4.76–2.0 mm) and 6.35 cmol/kg (<0.25 mm) for cultivated savannah. This indicated that cultivation significantly (p < 0.05) led to 71% and 6% reductions in Ca2+, Mg2+, K+ and Na+ concentrations within the 4.76–2.0 and <0.25 mm aggregate fractions, respectively. However, there were 18% and 50% increase in these elements in the 2.0–1.0 and 1.0–0.50 mm fractions of the cultivated soils of the savannah region, respectively. The general trend showed that in uncultivated soils, the 4.76–2.0 and <0.25 mm fractions were preferentially enriched with Ca2+, Mg2+, K+ and Na +; whereas, cultivation led to redistribution of these elements into the smaller aggregates. Since smaller aggregates are preferentially removed by erosion, this study underscores the need for sustainable soil management practices that would minimize nutrient loss when forest or fallow lands are converted to cropland.  相似文献   

11.
生物炭和氮肥配施提高土团聚体稳定性及作物产量   总被引：1，自引：1，他引：0  
【目的】通过田间定位试验,探讨生物炭和氮肥配施对土耕层土壤水稳性团聚体组成、稳定性、有机碳土层分布及冬小麦–夏玉米轮作体系下产量的影响,为生物炭在关中地区农业生产中的应用提供科学依据。【方法】本试验设置4个生物炭水平和2个氮肥水平,生物炭水平分别为0、1000、5000、10000 kg/hm2,依次记为B0、B1、B2、B3;氮肥水平包括两季总氮量480 kg/hm2(NT) 和两季总氮量减半240 kg/hm2(NH),共组成8个处理。采集0—10 cm、10—20 cm土层土壤样品,利用TTF-100土壤团聚体分析仪湿筛获得5种粒级的团聚体 (> 2 mm、1～2 mm、0.5～1 mm、0.25～0.5 mm、< 0.25 mm),用 > 0.25 mm团聚体含量 (R0.25)、平均重量直径 (MWD)、几何重量直径 (GMD) 表示水稳性团聚体的的稳定性,并测定了不同粒级团聚体中有机碳的含量及小麦–玉米两季作物总产量。【结果】与不施生物炭 (B0NT、B0NH) 相比,施用生物炭的处理显著增加了 > 2 mm、1～2 mm粒级水稳性大团聚体的百分含量 (P < 0.05),两粒级增幅范围分别为3.5%～180.3%、9.4%～98.9%。施用生物炭10000 kg/hm2(B3NT、B3NH) 时,MWD、GMD和R0.25增幅最高,分别增加了12.5%～112.5%、25.0%～65.7%、20.0%～65.0%。施用生物炭显著提高了土壤各粒级水稳性团聚体有机碳含量,与不施生物炭处理相比,> 2 mm、1～2 mm、0.5～1 mm 和0.25～0.5 mm粒级团聚体有机碳含量增幅分别为6.3%～30.5%、0.2%～28.2%、0.2%～41.6%和4.6%～39.1%。与0—10 cm土层相比,10—20 cm土层氮肥减量降低了土壤团聚体的稳定性,而施用生物炭10000 kg/hm2(B3NH) 可改善土壤团聚体的稳定性,改变有机碳分布。在10—20 cm土层,与B0NT处理相比,B0NH处理土壤水稳性团聚体的R0.25、MWD、GMD显著下降,三者分别降低了79.2%、25.7%、30.0%,而B3NH与B3NT处理之间无显著差异。与B0NT相比,B0NH处理 < 0.25 mm粒级微团聚体对土壤有机碳分配比例显著增加了17.4%,而B3NH处理与B3NT相比,< 0.25 mm粒级微团聚体对土壤有机碳分配比例无显著差异。此外,施用生物炭显著提高作物总产量,B2NT、B3NT和B3NH处理下两季作物总产量较高,分别较B0NT提高了27.0%、23.6%、27.9%,且三个处理之间无显著差异。从各指标相关分析可知,水稳定大团聚体的GMD与土壤全土有机碳以及两季作物总产量之间有着显著的正相关关系。【结论】生物炭配施氮肥显著提高了土壤水稳性大团聚体含量和团聚体稳定性,且提高小麦—玉米两季作物总产量。减施氮肥有利于有机碳向大团聚体中分配,供试条件下,生物炭10000 kg/hm2配施氮肥240 kg/hm2对提高土耕层团聚体稳定性、土壤有机碳及两季作物总产量效果最佳。  相似文献   

12.
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.  相似文献   

13.
Purpose

Characterizations of soil aggregates and soil organic carbon (SOC) losses affected by different water erosion patterns at the hillslope scale are poorly understood. Therefore, the objective of this study was to quantify how sheet and rill erosion affect soil aggregates and soil organic carbon losses for a Mollisol hillslope in Northeast China under indoor simulated rainfall.

Materials and methods

The soil used in this study was a Mollisol (USDA Taxonomy), collected from a maize field (0–20 cm depth) in Northeast China. A soil pan with dimensions 8 m long, 1.5 m wide and 0.6 m deep was subjected to rainfall intensities of 50 and 100 mm h?1. The experimental treatments included sheet erosion dominated (SED) and rill erosion dominated (RED) treatments. Runoff with sediment samples was collected during each experimental run, and then the samples were separated into six aggregate fractions (0–0.25, 0.25–0.5, 0.5–1, 1–2, 2–5, >?5 mm) to determine the soil aggregate and SOC losses.

Results and discussion

At rainfall intensities of 50 and 100 mm h?1, soil losses from the RED treatment were 1.4 and 3.5 times higher than those from the SED treatment, and SOC losses were 1.7 and 3.8 times greater than those from the SED treatment, respectively. However, the SOC enrichment ratio in sediment from the SED treatment was 1.15 on average and higher than that from the RED treatment. Furthermore, the loss of <?0.25 mm aggregates occupied 41.1 to 73.1% of the total sediment aggregates for the SED treatment, whereas the loss of >?0.25 mm aggregates occupied 53.2 to 67.3% of the total sediment aggregates for the RED treatment. For the organic carbon loss among the six aggregate fractions, the loss of 0–0.25 mm aggregate organic carbon dominated for both treatments. When rainfall intensity increased from 50 to 100 mm h?1, aggregate organic carbon loss increased from 1.04 to 5.87 times for six aggregate fractions under the SED treatment, whereas the loss increased from 3.82 to 27.84 times for six aggregate fractions under the RED treatment.

Conclusions

This study highlights the effects of sheet and rill erosion on soil and carbon losses at the hillslope scale, and further study should quantify the effects of erosion patterns on SOC loss at a larger scale to accurately estimate agricultural ecosystem carbon flux.

  相似文献   

14.
The quantification of phosphorus(P) in bulk soil and P distribution in different size fractions of water-stable aggregates(WSAs)are important for assessing potential P loss through runoff. We evaluated available and total P distribution within WSAs of a sitty clay to clay soil in a long-term fertility experiment of a rice-wheat cropping system in India. Surface soil samples were collected from seven plots amended with NPK fertilizers in combination with or without organic amendments, farmyard manure(FYM), green manure(GM), and paddy straw(PS). The plot with no NPK fertilizers or organic amendments was set as a control. The soil samples were separated by wet sieving into four soil aggregate size fractions: large macroaggregates( 2.0 mm), small macroaggregates(0.25–2.0 mm), fine microaggregates(0.05–0.25 mm), and a silt + clay-sized fraction( 0.05 mm). Structural indices were higher in the soil receiving organic amendments than in the soil receiving inorganic fertilizer alone. Organically amended soil had a higher proportion of stable macroaggregates than the control and the soil receiving inorganic fertilizer alone, which were rich in microaggregates. Total and available P contents within WSAs were inversely related to the aggregate size, irrespective of treatment. The distribution of available and total P in the soil aggregate size fraction was as follows: silt + clay-size fraction small macroaggregates fine microaggregates large macroaggregates. Within a size class, aggregate-associated available and total P contents in the organically amended soil were in the following order: FYM PS ≥ GM. The available P content of the microaggregates( 0.25 mm) was 8-to 10-times higher than that of the macroaggregates( 0.25 mm), and the total P content of the microaggregates was 4-to 5-times higher than that of the macroaggregates. Cultivation without organic amendments resulted in more microaggregates that could be checked by the application of organic amendments such as FYM and GM, which increased the proportion of water-stable macroaggregates by consolidating microaggregates into macroaggregates.  相似文献   

15.
The effects of tillage on the interaction between soil structure and microbial biomass vary spatially and temporally for different soil types and cropping systems. We assessed the relationship between soil structure induced by tillage and soil microbial activity at the level of soil aggregates. To this aim, organic C (OC), microbial biomass C (MBC) and soil respiration were measured in water-stable aggregates (WSA) of different sizes from a subtropical rice soil under two tillage systems: conventional tillage (CT) and a combination of ridge with no-tillage (RNT). Soil (0–20 cm) was fractionated into six different aggregate sizes (> 4.76, 4.76–2.0, 2.0–1.0, 1.0–0.25, 0.25–0.053, and < 0.053 mm in diameter). Soil OC, MBC, respiration rate, and metabolic quotient were heterogeneously distributed among soil aggregates while the patterns of aggregate-size distribution were similar among properties, regardless of tillage system. The content of OC within WSA followed the sequence: medium-aggregates (1.0–0.25 mm and 1.0–2.0 mm) > macro-aggregates (4.76–2.0 mm) > micro-aggregates (0.25–0.053 mm) > large aggregates (> 4.76 mm) > silt + clay fractions (< 0.053 mm). The highest levels of MBC were associated with the 1.0–2.0 mm aggregate size class. Significant differences in respiration rates were also observed among different sizes of WSA, and the highest respiration rate was associated with 1.0–2.0 mm aggregates. The Cmic/Corg was greatest for the large-macroaggregates regardless of tillage regimes. This ratio decreased with aggregate size to 1.0–0.25 mm. Soil metabolic quotient (qCO2) ranged from 3.6 to 17.7 mg CO2 g− 1 MBC h− 1. The distribution pattern of soil microbial biomass and activity was governed by aggregate size, whereas the tillage effect was not significant at the aggregate scale. Tillage regimes that contribute to greater aggregation, such as RNT, also improved soil microbial activity. Soil OC, MBC and respiration rate were at their highest levels for 1.0–2.0 mm aggregates, suggesting a higher biological activity at this aggregate size for the present ecosystem.  相似文献   

16.
Soil aggregate stability (SAS) is an indicator for soil condition and is greatly influenced by land use or land cover (LULC) type and other soil and environmental attributes. This study investigated the soil aggregate-size distribution, SAS, aggregate-associated organic carbon (AAOC) and the relative importance of factors affecting SAS and AAOC. Based on conditioned Latin hypercube sampling, soil aggregate samples were collected from the “A” horizon and wet sieved into large macroaggregates (>2.0 mm), small macroaggregates (0.25–2.0 mm), microaggregates (0.053–0.25 mm) and mineral fraction (<0.053 mm). The large macroaggregates accounted for 86% to 93% of the total aggregates under all LULC types except under dry land (64%) and paddy land (35%). The SAS under different LULC decreased in the order fir > shrubland > natural grassland > orchard > blue pine > broadleaf > mixed conifer > dry land > paddy land. The AAOC of the large macroaggregates constituted for 76%–90% of the total AAOC under all LULC types except under dry land (65%) and paddy land (38%). While SAS was largely influenced by the AAOC of small macroaggregates, microaggregates and large macroaggregates and LULC type, the AAOC of different aggregate fractions was mostly affected by LULC type, altitude and slope. SAS did not exhibit any significant relationship with the AAOC of different aggregate fractions under the natural LULC types but showed a strong relationship under the agricultural land indicating that AAOC is more critical for SAS under the agricultural land than under the natural LULC.  相似文献   

17.
An essential prerequisite for a sustainable soil use is to maintain a satisfactory soil organic‐matter (OM) level. This might be achieved by sound fertilization management, though impacts of fertilization on OM have been rarely investigated with the aid of physical fractionation techniques in semiarid regions. This study aimed at examining changes in organic C (OC) and N concentrations of physically separated soil OM pools after 26 y of fertilization at a site of the semiarid Loess Plateau in China. To separate sensitive OM pools, total macro‐OM (> 0.05 mm) was obtained from bulk soil by wet‐sieving and then separated into light macro‐OM (< 1.8 g cm–3) and heavy macro‐OM (> 1.8 g cm–3) subfractions; bulk soil was also differentiated into light OM (< 1.8 g cm–3) and mineral‐associated OM (> 1.8 g cm–3). Farmyard manure increased concentrations of total macro‐OC and N by 19% and 25%, and those of light fraction OC and N by 36% and 46%, compared to no manuring; both light OC and N concentrations but only total macro‐OC concentration responded positively to mineral fertilizations compared to no mineral fertilization. This demonstrated that the light‐fraction OM was more sensitive to organic or inorganic fertilization than the total macro‐OM. Mineral‐associated OC and N concentrations also increased by manuring or mineral fertilizations, indicating an increase of stable OM relative to no fertilization treatment, however, their shares on bulk soil OC and N decreased. Mineral fertilizations improved soil OM quality by decreasing C : N ratio in the light OM fraction whereas manuring led to a decline of the C : N ratio in the total macro‐OM fraction, with respect to nil treatment. Further fractionation of the total macro‐OM according to density clarified that across treatments about 3/4 of total macro‐OM was associated with minerals. Thus, by simultaneously applying particle‐size and density separation procedures, we clearly demonstrated that the macro‐OM differed from the light OM fraction not only in its chemical composition but also in associations with minerals. The proportion of the 0.5–0.25 mm water‐stable aggregates of soil was higher under organic or inorganic fertilizations than under no manure or no mineral fertilization, and increases in OC and N concentrations of water‐stable aggregates as affected by fertilization were greater for 1–0.5 and 0.5–0.25 mm classes than for the other classes. Results indicate that OM stocks in different soil pools can be increased and the loose aggregation of these strongly eroded loess soils can be improved by organic or inorganic fertilization.  相似文献   

18.
孟祥天  蒋瑀霁  王晓玥  孙波 《土壤》2018,50(2):326-332
生物质炭和秸秆还田是提高土壤有机碳含量和改良土壤团聚体结构的有效方法,但在长期尺度上生物质炭与秸秆还田改良土壤的效率仍不清楚。本研究针对中亚热带第四纪红黏土发育的红壤,基于等碳量不同碳源投入的5 a田间定位试验,包括对照、单施化肥、秸秆还田、秸秆–猪粪配施和生物质炭还田5个处理,采用干筛和湿筛法分析了不同施肥处理对土壤团聚体组成、稳定性和有机碳分布的影响。研究表明:施用等碳量的不同有机碳源5 a后显著增加了土壤有机碳含量,其增幅顺序为:生物质炭还田秸秆–猪粪配施秸秆还田。干筛法分析结果表明:与单施化肥处理相比,秸秆–猪粪配施和生物质炭还田处理显著增加0.25 mm机械稳定性团聚体含量(R0.25)和平均重量直径(mean weight diameter,MWD);秸秆还田和生物质炭还田处理显著增加了0.25~2 mm团聚体对土壤有机碳的贡献率。湿筛法分析结果表明:与单施化肥处理相比,秸秆还田和秸秆–猪粪配施处理显著增加R_(0.25)和MWD,但生物质炭还田处理和单施化肥处理相比差异不显著;秸秆还田和秸秆–猪粪配施处理显著降低团聚体破坏率(PAD),生物质炭还田处理显著增加了PAD;秸秆配施猪粪处理和秸秆还田处理显著增加了2 mm团聚体对土壤有机碳的贡献率。总体上,秸秆配施猪粪协同提高团聚体有机碳含量和团聚体稳定性的作用比秸秆还田和生物质炭还田要强。  相似文献   

19.
复种模式对豫西褐土团聚体稳定性及其碳、氮分布的影响   总被引：1，自引：0，他引：1  
  【目的】  长期单一的玉米–小麦复种模式会引起土壤结构破坏、农田生产力下降。探究不同复种模式对农田土壤团聚体稳定性及其碳、氮分布的影响,为维持土壤结构稳定,实现农业可持续发展提供科学依据。  【方法】  定位试验在河南洛阳褐土上进行。设置冬小麦–夏玉米 (T1)、冬小麦–夏花生 (T2)、冬小麦–夏玉米||花生间作 (2行玉米间作4行花生,T3) 3个复种模式处理。试验始于2014年6月,2019年10月夏季作物收获后 (共11茬作物),采集0—20和20—40 cm土层土壤样品,利用湿筛法和干筛法分析土壤团聚体组成、团聚体稳定性、有机碳和全氮在不同粒级团聚体中的含量及分配比例。  【结果】  与T1相比,在0—20 cm土层中,T2和T3处理土壤中 > 0.25 mm粒级的机械性团聚体 (DR0.25) 占比分别增加了5.9%和9.9%,> 0.25 mm粒级的水稳性团聚体 (WR0.25) 占比分别增加了50.3%和57.9%,不稳定性团粒指数 (ELT) 分别较T1减少了33.2%和50.6%,土壤团聚体破坏率 (PAD) 分别较T1减少49.3%和51.4%,土壤团聚体平均质量直径 (MWD) 分别较T1增加36.4%和47.0%,几何平均直径 (GMD) 分别较T1增加100.0%和120.0%。在20—40 cm土层中,T2和T3处理土壤中不稳定性团粒指数 (ELT) 分别较T1减少了13.2%和18.0%,土壤团聚体破坏率 (PAD) 分别较T1减少21.4%和28.8%,土壤团聚体平均质量直径 (MWD) 分别较T1增加4.8%和6.0%,几何平均直径 (GMD) 分别较T1增加11.5%和7.7%。各粒级的有机碳和全氮含量均以2～0.25 mm粒级最高,且0—20 cm土层的有机碳和全氮含量高于20—40 cm土层。与T1处理相比,T3处理显著提高了0—20 cm土层各粒级土壤全氮的贡献率和 > 0.25 mm粒级土壤有机碳的贡献率,降低了 < 0.25 mm粒级土壤有机碳的贡献率;T2处理显著提高了0—20 cm土层除 >2和<0.053 mm粒级外的土壤全氮的贡献率和 > 0.25 mm粒级土壤有机碳的贡献率,降低了0.25～0.053 mm粒级土壤有机碳的贡献率。与T1处理相比,T2和T3处理提升了0—20和20—40 cm土层土壤总有机碳、全氮、有效磷和速效钾的含量,3个处理的土壤容重和pH无显著差异。  【结论】  冬小麦–夏花生、冬小麦–夏玉米||花生复种模式较传统冬小麦–夏玉米复种模式明显增加了土壤大团聚体含量,增强了团聚体的机械稳定性和水稳定性,还可显著提高土壤团聚体 (特别是 > 0.25 mm粒级团聚体) 的碳、氮含量,提高土壤有效磷和速效钾含量,更有利于豫西褐土区农田土壤肥力保持。且冬小麦–夏玉米||花生复种的效果优于冬小麦–夏花生复种。  相似文献   

20.
黄土区不同施肥对土壤颗粒及微团聚体组成的影响   总被引：5，自引：0，他引：5  
采用野外采样与室内分析方法,运用颗粒体积分形理论,研究了15年长期不同施肥处理对黄土区农田土壤颗粒组成、 微团聚体分布及有机碳的影响。结果表明,施肥处理对020 cm土层影响较大,不同施肥处理土壤颗粒及微团聚体的优势粒级均为0.02~0.05 mm。有机肥（M）、 磷肥（P）、 有机肥和氮肥配施（MN）、 有机肥、 氮肥和磷肥配施（MNP）处理可显著提高020 cm土层0.1~0.2 mm土壤颗粒的百分含量,有机肥和磷肥配施（MP）以及MNP处理有利于该土层大粒径土壤微团聚体的形成。氮肥和磷肥配施（NP）处理的土壤分散率最大,M处理最小。不同施肥处理土壤颗粒体积分形维数差异不显著。相关性分析表明, 020 cm及2040 cm土层土壤颗粒体积分形维数与粘粒（0.002 mm）和细粉粒 （0.002~0.02 mm） 呈极显著正相关,与粗粉粒 （0.02~0.05 mm） 和细砂粒 （0.05~0.2 mm）极显著负相关; 土壤团聚度与0.05 mm各粒径土壤团聚体显著或极显著负相关,与 0.05 mm各粒径土壤团聚体显著或极显著正相关。020 cm土层土壤有机碳与0.01~0.05 mm各粒径土壤团聚体显著或极显著负相关,与0.1~0.5 mm各粒径土壤团聚体极显著正相关。  相似文献   

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