首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Increasing importance has been placed on the use of agricultural soils for the mitigation of atmospheric CO2 through sequestration of soil C. Although crop productivity is sustained mainly through the application of organic manure in the Indian Himalayas, little information is available on C sequestration, C content in different aggregate size fractions and soil water transmission properties (infiltration and saturated hydraulic conductivity) as affected by long-term manure addition. We analyzed results of an 8-year experiment, initiated in 1995–1996 on a silty clay loam soil, to determine the influence of fertilizer and fertilizer + farmyard manure (FYM) application on those important soil properties. The overall increase in soil organic C (SOC) content in the 0–45 cm soil depth in NPK + FYM treatment as compared to NPK and control treatments was 11.0 and 13.9 Mg C ha−1 at the end of 8 years, respectively. Application of FYM significantly reduced soil bulk density and increased mean weight diameter (MWD) and SOC contents in different aggregate size fractions. Soil organic C content in macroaggregates was greater than in microaggregates. The response of SOC content to FYM application was dependent upon inorganic fertilization and more upon balanced application of NPK than N only. Steady state infiltration rate under NPK + FYM (1.98 cm h−1) was higher than under unfertilized (0.72 cm h−1) and NPK (1.2 cm h−1). Soil water sorptivity (calculated from Philip's equation) under NPK + FYM (1.06 cm min−0.5) was higher than under NPK (0.61 cm min−0.5). We conclude that hill farmers in northern India should be encouraged to use FYM along with chemical fertilizers to increase SOC content and improve soil physical properties.  相似文献   

2.
Yield decline or stagnation and its relationship with soil organic matter fractions in soybean (Glycine max L.)–wheat (Triticum aestivum L.) cropping system under long-term fertilizer use are not well understood. To understand this phenomenon, soil organic matter fractions and soil aggregate size distribution were studied in an Alfisol (Typic Haplustalf) at a long-term experiment at Birsa Agricultural University, Ranchi, India. For 30 years, the following fertilizer treatments were compared with undisturbed fallow plots (without crop and fertilizer management): unfertilized (control), 100% recommended rate of N, NP, NPK, NPK+ farmyard manure (FYM) and NPK + lime. Yield declined with time for soybean in control (30 kg ha−1 yr−1) and NP (21 kg ha−1 yr−1) treatments and for wheat in control (46 kg ha−1 yr−1) and N (25 kg ha−1 yr−1) treatments. However, yield increased with time for NPK + FYM and NPK + lime treatments in wheat. At a depth of 0–15 cm, small macroaggregates (0.25–2 mm) dominated soil (43–61%) followed by microaggregates (0.053–0.25 mm) with 13–28%. Soil microbial biomass carbon (SMBC), nitrogen (SMBN) and acid hydrolysable carbohydrates (HCH) were greater in NPK + FYM and NPK + lime as compared to other treatments. With three decades of cultivation, C and N mineralization were greater in microaggregates than in small macroaggregates and relatively resistant mineral associated organic matter (silt + clay fraction). Particulate organic carbon (POC) and nitrogen (PON) decreased significantly in control, N and NP application over fallow. Results suggest that continuous use of NPK + FYM or NPK + lime would sustain yield in a soybean–wheat system without deteriorating soil quality.  相似文献   

3.
The mobilization of organic carbon (C) by water erosion could impact the terrestrial C budget, but the magnitude and direction of that impact remain uncertain due to a lack of data regarding the fates and quality of eroded C. A study was conducted to monitor total organic C and mineralizable C (MinC) in eroded materials from watersheds under no till (NT), chisel till (CT), disk till low input (DT-LI), pasture and forest. The DT-LI treatment relies on manure application and legume cover crops to partly supply the N needed when corn is grown, and on cultivation to reduce the use of herbicides. Each watershed was instrumented with a flume and a Coshocton wheel sampler for runoff measurement. Carbon dioxide (CO2) evolved during incubation (115 days) of runoff samples was fitted to a first-order decomposition model to derive MinC. Annual soil (6.2 Mg ha−1) and organic C (113.8 kg C ha−1) losses were twice as much in the DT-LI than in the other watersheds (<2.7 Mg soil ha−1, <60 kg C ha−1). More than management practices, rainfall class (based on intensity and energy) was a better controller of sediment C concentration and biodegradability. Sediment collected during the low-intensity (fall/winter) storms contained more organic C (37 g C kg−1) and MinC (30–40% of sediment C) than materials displaced during the high-intensity summer storms (22.1 g C kg−1 and 13%, respectively). These results suggest a more selective detachment and sorting of labile C fractions during low-intensity storms. However, despite the control of low-intensity storm on sediment C concentration and quality, increased soil loss with high-energy rainfall suggests that a few infrequent but high-energy storms could determine the overall impact of erosional events on terrestrial C cycling.  相似文献   

4.
Crop management practices have potential to enhance subsoil C and N sequestration in the southern U.S., but effects may vary with tillage regime and cropping sequence. The objective of this study was to determine the impacts of tillage and soybean cropping sequence on the depth distribution of soil organic C (SOC), dissolved organic C (DOC), and total N after 20 years of treatment imposition for a silty clay loam soil in central Texas. A continuous soybean monoculture, a wheat–soybean doublecrop, and a sorghum–wheat–soybean rotation were established under both conventional (CT) and no tillage (NT). Soil was sampled after soybean harvest and sectioned into 0–5, 5–15, 15–30, 30–55, 55–80, and 80–105 cm depth intervals. Both tillage and cropping intensity influenced C and N dynamics in surface and subsurface soils. No tillage increased SOC, DOC, and total N compared to CT to a 30 cm depth for continuous soybean, but to 55 cm depths for the more intensive sorghum–wheat–soybean rotation and wheat–soybean doublecrop. Averaged from 0 to 105 cm, NT increased SOC, DOC, and total N by 32, 22, and 34%, respectively, compared to CT. Intensive cropping increased SOC and total N at depths to 55 cm compared to continuous soybean, regardless of tillage regime. Continuous soybean had significantly lower SOC (5.3 g kg−1) than sorghum–wheat–soybean (6.4 g kg−1) and wheat–soybean (6.1 g kg−1), and 19% lower total N than other cropping sequences. Dissolved organic C was also significantly higher for sorghum–wheat–soybean (139 mg C kg−1) than wheat–soybean (92 mg C kg−1) and continuous soybean (100 mg C kg−1). The depth distribution of SOC, DOC, and total N indicated treatment effects below the maximum tillage depth (25 cm), suggesting that roots, or translocation of dissolved organic matter from surface soils, contributed to higher soil organic matter levels under NT than CT in subsurface soils. High-intensity cropping sequences, coupled with NT, resulted in the highest soil organic matter levels, demonstrating potential for C and N sequestration for subsurface soils in the southern U.S.  相似文献   

5.
A 3-year field study was conducted to evaluate the effect of three tillage practices (conventional, zero and reduced/strip) with two nitrogen levels (120 and 150 kg N ha−1) applied in primary strips and three crop residue management practices (removal, burning and incorporation) in secondary strips in wheat after rice. Reduced tillage resulted in significantly higher overall mean wheat yield (5.10 Mg ha−1) compared to conventional (4.60 Mg ha−1) and zero tillage (4.75 Mg ha−1). Residue incorporation resulted in highest mean yield (5.86 Mg ha−1) during third year. Maximum mean yield (6.1 Mg ha−1) was obtained in reduced tillage followed by conventional tillage (5.8 Mg ha−1) under residue incorporation in third year. The weed dry weight recorded at 30 days after sowing was highest (0.3 Mg ha−1) under zero tillage and lowest under conventional tillage (0.16 Mg ha−1). Among crop residue management practices, the highest dry weight of weeds (0.22 Mg ha−1) was recorded under residue incorporation. The highest infiltration rate (1.50 cm h−1) was recorded in residue incorporation followed by residue burning (1.44 cm h−1) whereas; the lowest (0.75 cm h−1) in zero tillage. Soil bulk density was the highest (1.69 Mg m−3) under zero tillage and the lowest in residue incorporation (1.59 Mg m−3). There were no changes in soil available P and K after each crop sequence in relation to tillage practices during first 2 years. Higher organic carbon (5.1–5.4 g kg−1) was measured under zero tillage compared to other treatments. Residue incorporation increased soil organic carbon and available P while higher available K was monitored in burning treatment during the third year. These results suggest that reduced tillage and in situ incorporation of crop residues at 5 Mg ha−1 along with 150 kg N ha−1 were optimum to achieve higher yield of wheat after rice in sandy loam soils of Indo-Gangetic plains of India.  相似文献   

6.
Soil erosion and depositional processes in relation to land use and soil management need to be quantified to better understand the soil organic carbon (SOC) dynamics. This study was undertaken on a Miamian soil (Oxyaquic Hapludalfs) under on-farm conditions in western Ohio with the objectives of evaluating the effects of degree of erosion on SOC stock under a range of tillage systems. Six farms selected for this study were under: no-till (NT) for 15, 10, 6 and 1.5 years; chisel till every alternate year with annual manure application (MCT); and annual chisel till (ACT). A nearby forest (F) site on the same soil was chosen as control. Using the depth of A horizon as an indicator of the degree of erosion, four erosion phases identified were: uneroded (flat fields under F, NT15, and on the summit of sloping fields under NT10, NT6, NT1.5 and MCT); deposition (NT10, NT6, NT1.5 and ACT); slight (NT10, MCT and ACT); and moderate erosion (NT10 and ACT). Core and bulk soil samples were collected in triplicate from four depths (i.e., 0–10, 10–20, 20–30 and 30–50 cm) for each erosional phase in each field for the determination of bulk density, and SOC concentrations and stocks. SOC concentration in NT fields increased at a rate of 5% year−1 for 0–10 cm and 2.5% year−1 for 10–20 cm layer with increasing duration under NT. High SOC concentration for NT15 is indicative of SOC-sequestration potential upon conversion from plow till to NT. SOC concentration declined by 19.0–14.5 g kg−1 in MCT and 11.3–9.7 g kg−1 in NT10 between uneroded and slight erosion, and 12.0–11.2 g kg−1 between slight and moderate erosion in ACT. Overall SOC stock was greatest in the forest for each of the four depths. Total SOC stock for the 50 cm soil layer varied in the order F (71.99 Mg ha−1) > NT15 (56.10 Mg ha−1) > NT10 (37.89 Mg ha−1) = NT6 (36.58 Mg ha−1) for uneroded phase (P < 0.05). The lack of uneroded phase in ACT indicated high erosion risks of tillage, as also indicated by the high SOC stock for deposition phase from 0 to 50 cm soil layer (ACT (56.56 Mg ha−1) > NT1.5 (42.70 Mg ha−1) > NT10 (30.97 Mg ha−1)). Tillage increased soil erosion and decreased SOC stock for top 10 cm layer for all erosional phases except deposition.  相似文献   

7.
Soil organic matter is strongly related to soil type, landscape morphology, and soil and crop management practices. Therefore, long-term (15–36-years) effects of six cropland management systems on soil organic carbon (SOC) pool in 0–30 cm depth were studied for the period of 1939–1999 at the North Appalachian Experimental Watersheds (<3 ha, Dystric Cambisol, Haplic Luvisol, and Haplic Alisol) near Coshocton, OH, USA. Six management treatments were: (1) no tillage continuous corn with NPK (NC); (2) no tillage continuous corn with NPK and manure (NTC-M); (3) no tillage corn–soybean rotation (NTR); (4) chisel tillage corn–soybean rotation (CTR); (5) moldboard tillage with corn–wheat–meadow–meadow rotation with improved practices (MTR-I); (6) moldboard tillage with corn–wheat–meadow–meadow rotation with prevalent practices (MTR-P). The SOC pool ranged from 24.5 Mg ha−1 in the 32-years moldboard tillage corn (Zea mays L.)–wheat (Triticum aestivum L.)–meadow–meadow rotation with straight row farming and annual application of fertilizer (N:P:K=5:9:17) of 56–112 kg ha−1 and cattle (Bos taurus) manure of 9 Mg ha−1 as the prevalent system (MTR-P) to 65.5 Mg ha−1 in the 36-years no tillage continuous corn with contour row farming and annual application of 170–225 kg N ha−1 and appropriate amounts of P and K, and 6–11 Mg ha−1 of cattle manure as the improved system (NTC-M). The difference in SOC pool among management systems ranged from 2.4 to 41 Mg ha−1 and was greater than 25 Mg ha−1 between NTC-M and the other five management systems. The difference in the SOC pool of NTC-M and that of no tillage continuous corn (NTC) were 16–21 Mg ha−1 higher at the lower slope position than at the middle and upper slope positions. The effect of slope positions on SOC pools of the other management systems was significantly less (<5 Mg ha−1). The effects of manure application, tillage, crop rotation, fertilizer rate, and soil and water conservation farming on SOC pool were accumulative. The NTC-M treatment with application of NPK fertilizer, lime, and cattle manure is an effective cropland management system for SOC sequestration.  相似文献   

8.
Cover crops may influence soil carbon (C) sequestration and microbial biomass and activities by providing additional residue C to soil. We examined the influence of legume [crimson clover (Trifolium incarnatum L.)], nonlegume [rye (Secale cereale L.)], blend [a mixture of legumes containing balansa clover (Trifolium michelianum Savi), hairy vetch (Vicia villosa Roth), and crimson clover], and rye + blend mixture cover crops on soil C fractions at the 0–150 mm depth from 2001 to 2003. Active fractions of soil C included potential C mineralization (PCM) and microbial biomass C (MBC) and slow fraction as soil organic C (SOC). Experiments were conducted in Dothan sandy loam (fine-loamy, kaolinitic, thermic, Plinthic Kandiudults) under dryland cotton (Gossypium hirsutum L.) in central Georgia and in Tifton loamy sand (fine-loamy, siliceous, thermic, Plinthic Kandiudults) under irrigated cotton in southern Georgia, USA. Both dryland and irrigated cotton were planted in strip tillage system where planting rows were tilled, thereby leaving the areas between rows untilled. Total aboveground cover crop and cotton C in dryland and irrigated conditions were 0.72–2.90 Mg C ha−1 greater in rye + blend than in other cover crops in 2001 but was 1.15–2.24 Mg C ha−1 greater in rye than in blend and rye + blend in 2002. In dryland cotton, PCM at 50–150 mm was greater in June 2001 and 2002 than in January 2003 but MBC at 0–150 mm was greater in January 2003 than in June 2001. In irrigated cotton, SOC at 0–150 mm was greater with rye + blend than with crimson clover and at 0–50 mm was greater in March than in December 2002. The PCM at 0–50 and 0–150 mm was greater with blend and crimson clover than with rye in April 2001 and was greater with crimson clover than with rye and rye + blend in March 2002. The MBC at 0–50 mm was greater with rye than with blend and crimson clover in April 2001 and was greater with rye, blend, and rye + blend than with crimson clover in March 2002. As a result, PCM decreased by 21–24 g CO2–C ha−1 d−1 but MBC increased by 90–224 g CO2–C ha−1 d−1 from June 2001 to January 2003 in dryland cotton. In irrigated cotton, SOC decreased by 0.1–1.1 kg C ha−1 d−1, and PCM decreased by 10 g CO2–C ha−1 d−1 with rye to 79 g CO2–C ha−1 d−1 with blend, but MBC increased by 13 g CO2–C ha−1 d−1 with blend to 120 g CO2–C ha−1 d−1 with crimson clover from April 2001 to December 2002. Soil active C fractions varied between seasons due to differences in temperature, water content, and substrate availability in dryland cotton, regardless of cover crops. In irrigated cotton, increase in crop C input with legume + nonlegume treatment increased soil C storage and microbial biomass but lower C/N ratio of legume cover crops increased C mineralization and microbial activities in the spring.  相似文献   

9.
Increased use of conservation tillage is being considered as a way to sequester atmospheric C in the soil. However, little information exists on the effect of rotation and its interaction with tillage on soil organic carbon (SOC). A research trial with combinations of rotations and tillage treatments was sampled 20 years after its establishment to assess the effects on SOC sequestration in a typic Hapludalf in southern Ontario, Canada. The cropping treatments included continuous corn (zea mays L.), six rotations comprised of 2 years of corn following 2 years of another crop or crop sequence, and continuous alfalfa (Medicago sativa L.). Each rotation was split into either fall moldboard plow (MP) or fall chisel plow (CP) treatments. Continuous alfalfa was plowed and replanted every 4 years. Soil samples were taken incrementally to a depth of 40 cm and SOC and bulk density determined. The average SOC concentration (0–40 cm) was greatest in continuous alfalfa (18.0 g C kg−1). The treatments of soybean (Glycine max L.Merr.)+winterwheat (Triticum aestivum L.) or barley+barley (Trifolium pratense L.) (interseeded with red clover) followed by 2 years of corn had higher SOC concentrations (17.2–17.3 g C kg−1) than continuous corn and the treatments of 2 years of corn following 2 years of alfalfa or soybean (16.4–16.5 g C kg−1). The rotation of 2 years of barley followed by 2 years of corn had the lowest SOC concentrations (15.2 g C kg−1). On an equivalent mass basis, the rotations of soybean+winterwheat or barley+barley (underseeded with red clover) followed by 2 years of corn, had 2–9 Mg ha−1 more C than the other corn-based rotations. Including red clover in the winter wheat seemed to accelerate the rate of C mineralization compared to winter wheat without red clover; whereas interseeding red clover with barley increased SOC contents compared to excluding red clover in the barley rotation. More SOC was found in the top 10 cm and less in the 10–20 cm depth of the CP than in the MP soils. However, the CP did not increase the SOC content (0–20 cm) above that of MP indicating that this form of reduced tillage did not increase C sequestration in any of the rotations on this soil.  相似文献   

10.
An experiment to evaluate the impact of water erosion and cultivation on the soil carbon dynamic and carbon stock in a semiarid area of South-East Spain was carried out. The study was performed under three different land use scenarios: (1) forest; (2) abandoned agricultural field; and (3) non-irrigated olive grove. Experimental erosion plots (in olive grove and forest) and sediment traps (in the abandoned area) were used to determine the carbon pools associated with sediments and runoff after each event occurring between September 2005 and November 2006.

Change in land use from forest to cultivated enhanced the risk of erosion (total soil loss in olive cropland seven-fold higher than in the forest area) and reduced the soil carbon stock (in the top 5 cm) by about 50%. Mineral-associated organic carbon (MOC) represented the main C pool in the three study areas although its contribution to soil organic carbon (SOC) was significantly higher in the disturbed areas (78.91 ± 1.81% and 77.29 ± 1.21% for abandoned and olive area, respectively) than in the forest area (66.05 ± 3.11%). In both, the olive and abandoned soils, the reduction in particulate organic carbon (POC) was proportionally greater than the decline in MOC.

The higher degree of sediment production in the olive cropland had an important consequence in terms of the carbon losses induced by erosion compared to the abandoned and forest plots. Thus, the total OC lost by erosion in the sediments was around three times higher in the cultivated (5.12 g C m−2) than the forest plot (1.77 g C m−2). The abandoned area displayed similar OC losses as a result of erosion as the forest plot (in the measurement period: 2.07 g C m−2, 0.63 g C m−2 and 0.65 g C m−2 for olive, forest and abandoned area, respectively). MOC represented the highest percentage of contribution to total sediment OC for all the events analysed and in all uses being, in general these values higher in Olive (74–90%) than in the other two areas (55–80%). The organic carbon lost was basically linked to the solid phase in the three land uses, although the contribution of DOC to total carbon loss by erosion varied widely with each event.

Data from this study show that the more labile OC fraction (POC) lost in soil in the cultivated area was mainly due to the effect of cultivation (low overall biomass production and residue return together with high C mineralization) rather than to water erosion, given that the major part of the OC lost in sediments was in the form of MOC.  相似文献   


11.
Chinese grasslands have undergone great changes in land use in recent decades. Approximately 18.2% of the present arable land in China originated from the cultivation of grassland, but its impact on the carbon cycle has not been fully understood. This study was conducted in situ for 3 years to assess the comprehensive effects of cultivation of temperate steppe on soil organic carbon (SOC) and soil respiration rates as well as ecosystem respiration. As compared with those in the Stipa baicalensis steppe, the SOC concentrations at depths of 0–10 and 10–20 cm in the spring wheat field were found to have decreased by 38.3 and 17.4% respectively from 29.5 and 21.9 g kg−1 to 18.2 and 18.1 g kg−1 after a cultivation period of 30 years. Accordingly, the total amounts of soil respiration through the growing season (from April to September) in 2002, 2003 and 2004 were 265.2, 282.2 and 237.4 g C m−2 respectively in the spring wheat field, which were slightly lower than the values of 342.2, 412.0 and 312.1 g C m−2 in the S. baicalensis steppe, while ecosystem respiration of 690.9, 991.2 and 569.6 g C m−2 respectively in the spring wheat field were markedly higher than those of 447.0, 470.9 and 429.7 g C m−2 in the steppe plot. Similar seasonal variations of ecosystem respiration and soil respiration existed in both sample sites. Respiration rates were higher and greater differences existed in both ecosystem respiration and soil respiration during the exuberant growth stage of plants (from mid-June to mid-August). However, in the slower-growth period of the growing season (before late May and after late August), the CO2 effluxes of the two sample sites were similar and remained at a relatively low level. The results also showed that ecosystem respiration and soil respiration were under similar environmental controls in both sample sites. Soil water content at a depth of 0–10 cm and soil temperatures at 5 and 10 cm were the main factors affecting the variations in ecosystem respiration and soil respiration rates in droughty years of 2002 and 2004 and in the rainy 2003, respectively. This study suggests that the conversion of the grassland to the spring wheat field has increased the carbon loss of the whole ecosystem due to the change of vegetation cover type and significantly reduced the carbon storage of surface soil. In addition, the tillage of grassland had different effects on ecosystem respiration and soil respiration. The effects were also dissimilar in different growth stages, which should be fully considered when assessing and predicting the effects of cultivation on the net CO2 balance of grassland ecosystems.  相似文献   

12.
An 8-yr (1998–2005) field experiment was conducted on a Gray Luvisol (Boralf) soil near Star City, Saskatchewan, Canada, to determine the effects of tillage (no-tillage – NT and conventional tillage – CT), straw management (straw retained – R and straw not retained – NR) and N fertilizer (0, 40, 80 and 120 kg N ha−1, except no N to pea (Pisum sativum L.) phase of the rotation) on seed and straw yield, mass of N and C in crop, organic C and N, inorganic N and aggregation in soil, and nitrous oxide (N2O) emissions for a second 4-yr rotation cycle (2002–2005). The plots were seeded to barley (Hordeum vulgare L.) in 2002, pea in 2003, wheat (Triticum aestivum L.) in 2004 and canola (Brassica napus L.) in 2005. Seed, straw and chaff yield, root mass, and mass of N and C in crop increased with increasing N rate for barley in 2002, wheat in 2004 and canola in 2005. No-till produced greater seed (by 51%), straw (23%) and chaff (13%) yield of barley than CT in 2002, but seed yield for wheat in 2004, and seed and straw yield for canola in 2005 were greater under CT than NT. Straw retention increased seed (by 62%), straw (by 43%) and chaff (by 12%) yield, and root mass (by 11%) compared to straw removal for barley in 2002, wheat in 2004, and seed and straw yield for pea in 2003. No-till resulted in greater mass of N in seed, and mass of C in seed, straw, chaff and root than CT for barley in 2002, but mass of N and C were greater under CT than NT for wheat in 2004 and for canola in 2005 in many cases. Straw retention had greater mass of N and C in seed, straw, chaff and root in most cases compared to straw removal for barley in 2002, pea in 2003 and wheat in 2004. Soil moisture content in spring was higher under NT than CT and with R than NR in the 0–15 cm depth, with the highest moisture content in the NT + R treatment in many cases. After eight crop seasons, tillage and straw management had no effect on total organic C (TOC) and N (TON) in the 0–15 cm soil, but light fraction organic C (LFOC) and N (LFON), respectively, were greater by 1.275 Mg C ha−1 and 0.031 Mg N ha−1 with R than NR, and also greater by 0.563 Mg C ha−1 and 0.044 Mg N ha−1 under NT than CT. There was no effect of tillage, straw and N fertilization on the NH4-N in soil in most cases, but R treatment had higher NO3-N concentration in the 0–15 cm soil than NR. The NO3-N concentration in the 0–15, 15–30 and 30–60 cm soil layers increased (though small) with increasing N rate. The R treatment had 6.7% lower proportion of fine (<0.83 mm diameter) and 8.6% greater proportion of large (>38.0 mm) dry aggregates, and 4.5 mm larger mean weight diameter (MWD) compared to NR treatment. This suggests a lower potential for soil erosion when crop residues are retained. There was no beneficial effect of elimination of tillage on soil aggregation. The amount of N lost as N2O was higher from N-fertilized (580 g N ha−1) than from zero-N (155 g N ha−1) plots, and also higher in CT (398 g N ha−1) than NT (340 g N ha−1) in some cases. In conclusion, retaining crop residues along with no-tillage improved some soil properties and may also be better for the environment and the sustainability of high crop production. Nitrogen fertilization improved crop production and some soil quality attributes, but also increased the potential for NO3-N leaching and N2O-N emissions, especially when applied in excess of crop requirements.  相似文献   

13.
Soil erosion is a major threat for Ferralsols in Cameroon. The influence of traditional intercropping (TI), disk-harrow ploughing (DH), no-tillage (NT), and Wischmeier bare fallow (BF) on runoff coefficient, soil loss, organic carbon (OC) content and bulk density was evaluated in topsoils of a forest Ferralsol in Yaoundé region, Central Cameroon, using erosion plots. This was to ensure the best conditions for the determination of the soil properties to be assessed. After two years of cropping, the mean runoff coefficient remained very low for TI (<2% of the rain) as compared with NT (14%) and DH (15%). The same held true for soil loss which was in the order of 2, 68 and 109 Mg ha−1 for TI, NT, and DH respectively, and bulk density which was 1.06, 1.18 and 1.21 Mg m−3 respectively. Comparing the latter with the measurements obtained from BF (1.23 Mg m−3) and the adjacent secondary forest (SF) (1.04 Mg m−3) showed that the disk-harrow treatment was the most degraded among the three. The same comparison was made for the OC content. It was found that while in SF, OC was as high as 30 g kg−1, it was only 11, 13, 15 and 18 g kg−1 in BF, DH, TI, and NT respectively. On the average and for the time frame considered, TI adversely affected topsoil properties less than NT, DH and BF in this order. Based on the above, it can be concluded that TI is more conservative than the three other land management techniques investigated.  相似文献   

14.
The effect of soil incorporations of lantana (Lantana spp.) biomass, an obnoxious weed, on physical environment of a silty clay loam soil (Typic Hapludalf) under rice (Oryza sativa L.)–wheat (Triticum aestivum L.) cropping was studied in a long-term field experiment conducted in a wet temperate region of north India. Fresh lantana biomass was incorporated into the plough layer at 10, 20 and 30 Mg ha−1 annually, 7–10 days before puddling. Plant-available water capacity (PAWC), non-limiting water range (NLWR) and NLWR:PAWC ratio were determined to characterize soil physical environment during wheat crop in the tenth cropping cycle.

Ten annual applications of lantana at 10, 20 and 30 Mg ha−1, increased organic carbon (OC) content over control by 12.6, 17.6 and 27.9% in 0–15 cm soil layer, and 17.1, 26.3 and 39.5% in 15–30 cm soil layer, respectively. The OC content in 0–15 and 15–30 cm soil layer of control plots was 11.1 and 7.6 g kg−1 soil. Bulk density decreased by 3–14% in 7.5–10.5 cm layer and 1–6% in 15–18 cm layer. Volumetric moisture contents at 10% air-filled porosity were 38.4, 40.0, 54.5 and 55.7% at 7.5–10.5 cm depth, and 31.4, 32.2, 33.9 and 34.6% at 15–18 cm depth corresponding to 0, 10, 20 and 30 Mg ha−1 lantana treatment, respectively. At 15–18 cm soil depth, volumetric moisture contents at 2 MPa soil penetration resistance were 26.9, 24.8, 23.0 and 19.6% in zero, 10, 20 and 30 Mg ha−1 lantana-treated plots, respectively. Lower soil water contents associated with 10% air-filled porosity and greater soil water contents associated with a limiting penetration resistance of 2 MPa resulted in a lower NLWR (4.3%) for control as compared to lantana-treated soil (7.4–15.1%). The PAWC showed slight increase from 12.9 to 13.4–14.9% due to lantana additions. The NLWR:PAWC ratio was also lower in control (0.33) as compared to lantana-treated soil (0.55–1.01). The NLWR was significantly and positively correlated with wheat grain yield (r=0.858**).  相似文献   


15.
Soil organic matter (SOM) and its different pools have key importance in optimizing crop production, minimizing negative environmental impacts, and thus improving soil quality. The objective of this study was to evaluate the soil C and N contents in bulk soil and in different SOM pools (light and heavy fractions) of a clayey Rhodic Ferralsol after 13 years of different tillage and crop rotations in Passo Fundo, State of Rio Grande do Sul, Brazil. Soil samples were collected from no-tillage (no soil disturbance except for sowing; NT) and conventional tillage (disc plough followed by light disc harrowings; CT) applied to wheat/soybean (W/S) and wheat/soybean–vetch/maize (W/S–V/M) rotations. As reference, soil was sampled from a non-cultivated area adjacent to the field experiment. The greatest soil C and N contents were found in non-cultivated soils in the 0–5 cm depth (45 g C kg−1 soil and 3.6 g N kg−1 soil). Crop cultivation led to a decrease in SOM content which was higher for CT soils (approx. 60% decrease in C and N contents) than NT soils (approx. 43% decrease in C and N contents) at 0–5 cm. Tillage had the greatest impact on soil C and N storage. Soils under NT did not contain higher C and N storage than CT soils below 5 cm depth. Significantly, higher amounts of organic carbon of FLF in CT (0.5–0.7 g C kg−1 soil) than in NT soils (0.2 g C kg−1 soil) at 10–20 cm depth were also observed and the differences in C and N storage between CT and NT soils in the 0–30 cm layer were not significant. Silt and clay fractions contained the largest amount of organic carbon (60–95% of total organic carbon), and free light fraction was the most sensitive pool of organic carbon to detect changes in SOM due to soil tillage and crop rotations.  相似文献   

16.
Under semiarid Mediterranean climatic conditions, soils typically have low organic matter content and weak structure resulting in low infiltration rates. Aggregate stability is a quality indicator directly related to soil organic matter, which can be redistributed within soil by tillage. Long-term effects (1983–1996) of tillage systems on water stability of pre-wetted and air dried aggregates, soil organic carbon (SOC) stratification and crop production were studied in a Vertic Luvisol with a loam texture. Tillage treatments included conventional tillage (CT), minimum tillage (MT) and zero tillage (ZT) under winter wheat (Triticum aestivum L.) and vetch (Vicia sativa L.) rotation (W–V), and under continuous monoculture of winter wheat or winter barley (Hordeum vulgare L.) (CM). Aggregate stability of soil at a depth of 0–5 cm was much greater when 1–2 mm aggregates were vacuum wetted prior to sieving (83%) than when slaked (6%). However, slaking resulted in tillage effects that were consistent with changes in SOC. Aggregate stability of slaked aggregates was greater under ZT than under CT or MT in both crop rotations (i.e., 11% vs. 3%, respectively).

SOC under ZT tended to accumulate in the surface soil layer (0–5 and 5–10 cm) at the expense of deeper ones. At depths of 10–20 and 20–30 cm no differences in SOC were encountered among tillage systems, but CT exhibited the highest concentration at 30–40 cm depth. Nevertheless, when comparisons were made on mass basis (Mg ha−1), significant differences in stocked SOC were observed at depths of 0–10 and 0–20 cm, where ZT had the highest SOC content in both rotations. The stock of SOC to a depth of 40 cm, averaged across crop rotations, was greater under ZT (43 Mg ha−1) than under CT (41 Mg ha−1) and MT (40 Mg ha−1) although these figures were not significantly different. Likewise, no significant differences were encountered in the stock of SOC to a depth of 40 cm among crop rotations (i.e., 42 Mg ha−1 for W–V vs. 40 Mg ha−1 for CM).

Crop production with wheat–vetch and continuous cereal showed no differences among tillage systems. Yields were strongly limited by the environmental conditions, particularly the amount of rainfall received in the crop growth season and its distribution. Similar yield and improved soil properties under ZT suggests that it is a more sustainable system for the semiarid Mediterranean region of Spain.  相似文献   


17.
Carbon sequestration in two Brazilian Cerrado soils under no-till   总被引：2，自引：0，他引：2  
A considerable proportion of the 200 million hectares of the Brazilian Cerrado is suitable for annual crops but little is known about the effects of tillage on the C dynamics of Cerrado soils. We evaluated the role of two representative Cerrado Oxisols (350 and 650 g clay kg−1) as sources or sinks of atmospheric C when managed under three tillage systems (conventional tillage (CT), reduced tillage (RT), and no-till (NT)) in 8- and 5-year long-term experiments. A literature review was also carried out and the mean C sequestration rates in no-till soils of tropical and subtropical regions of Brazil were calculated and compared with values for soils from temperate regions of the world. The original C stocks in 0–20 cm layer of soils under native Cerrado were higher in the clayey (54.0 Mg ha−1) than in the sandy clay loam soil (35.4 Mg ha−1), suggesting a higher physical stability of organic matter associated with variable clay minerals in the clayey Oxisol. The original C stocks of the native Cerrado soils appear not to have decreased after 23 years of conventional tillage in the sandy clay loam Oxisol, except when the soil had been subjected to erosion (15% loss of C), or after 25 years in the clayey Oxisol. Compared to conventionally tilled soil, the C stocks in no-till sandy clay loam Oxisol increased by 2.4 Mg ha−1 (C sequestration rate = 0.30 Mg ha−1 year−1) and in the clayey Oxisol by 3.0 Mg ha−1 (C sequestration rate = 0.60 Mg ha−1 year−1). The mean rate of C sequestration in the no-till Brazilian tropical soils was estimated to be 0.35 Mg ha−1 year−1, similar to the 0.34 Mg ha−1 year−1 reported for soils from temperate regions but lower than the 0.48 Mg ha−1 year−1 estimated for southern Brazilian subtropical soils. Considering the large area (about 70 million hectares) of the Cerrado which is currently used and potentially available for cropland, the adoption of no-till systems could turn the Cerrado soils into a significant sink for atmospheric C and contribute to the mitigation of global climate change.  相似文献   

18.
Woody plant proliferation in grasslands and savannas has been documented worldwide in recent history. To better understand the consequences of this vegetation change for the C-cycle, we measured soil microbial biomass carbon (Cmic) in remnant grasslands (time 0) and woody plant stands ranging in age from 10 to 130 years in a subtropical ecosystem undergoing succession from grassland to woodlands dominated by N-fixing trees. We also determined the ratio of SMB-C to soil organic carbon (Cmic/Corg) as an indicator of soil organic matter quality or availability, and the metabolic quotient (qCO2) as a measure of microbial efficiency. Soil organic carbon (Corg) and soil total nitrogen (STN) increased up to 200% in the 0–15 cm depth increment following woody plant invasion of grassland, but changed little at 15–30 cm. Cmic at 0–15 cm increased linearly with time following woody plant encroachment and ranged from 400 mg C kg−1 soil in remnant grasslands up to 600–1000 mg C kg−1 soil in older (>60 years) woody plant stands. Cmic at 15–30 cm also increased linearly with time, ranging from 100 mg C kg−1 soil in remnant grasslands to 400–700 mg C kg−1 soil in older wooded areas. These changes in Cmic in wooded areas were correlated with concurrent changes in stores of C and N in soils, roots, and litter. The Cmic/Corg ratio at 0–15 cm decreased with increasing woody plant stand age from 6% in grasslands to <4% in older woodlands suggesting that woody litter may be less suitable as a microbial substrate compared with grassland litter. In addition, higher qCO2 values in woodlands (0.8 mg CO2-C g−1 Cmic h−1) relative to remnant grasslands (0.4 mg CO2-C g−1 Cmic h−1) indicated that more respiration was required per unit of Cmic in wooded areas than in grasslands. Observed increases in Corg and STN following woody plant encroachment in this ecosystem may be a function of both greater inputs of poor quality C that is relatively resistant to decay, and the decreased ability of soil microbes to decompose this organic matter. We suggest that increases in the size and activity of Cmic following woody plant encroachment may result in: (a) alterations in competitive interactions and successional processes due to changes in nutrient dynamics, (b) enhanced formation and maintenance of soil physical structures that promote Corg sequestration, and/or (c) increased trace gas fluxes that have the potential to influence atmospheric chemistry and the climate system at regional to global scales.  相似文献   

19.
Spatial distribution of carbon (C) within a soil profile and across a landscape is influenced by many factors including vegetation, soil erosion, water infiltration, and drainage. For this reason, we attempted to determine the soil C distribution of an eroded soil. A three-dimensional (3D) map of a 0.72 ha field with a Dubuque silt loam soil which has three levels of erosion (slight, moderate, and severe) was developed using soil distribution and profile data collected using a profile cone penetrometer (PCP). This map displays the distribution of the total depth of the Ap and Bt1 horizons and the upper part of the 2Bt2 horizon. A map of soil C distribution was created for this landscape using C content information obtained from soil samples. Based on the C distribution in the upper two horizons, a 3D viewing was developed of soil C distribution for this eroded landscape. The 3D assessment of C distribution provides a better means of assessing the impact of soil erosion on C fate. It was estimated that there were 52 Mg ha−1 of total C in the surface (Ap) horizon and 61 Mg ha−1 in the Bt1 horizon for the 0.72 ha area. This increase in C with depth in the soil can be attributed to an increase in clay content and C leaching resulting in stable carbon–clay complexes. The C content was 16.0, 17.5, and 19.0 g kg−1 for the Ap horizon in the slight, moderate, and severe erosion levels, respectively. However, it was estimated that the total C amount in the respective Ap horizons was 28, 14, and 10 Mg ha−1 for the slight, moderate, and severe areas. The Bt1 horizon had 31, 19, and 11 Mg ha−1 of C in the slight, moderate, and severe areas, respectively. For the 0.72 ha area, 25% was severely eroded with 31 and 44% being moderate and slight, respectively. Soil C distribution information, such as that presented here, can be very valuable for soil management and could be used to determine possible C storage credits.  相似文献   

20.
The type of conservation-tillage management employed could impact surface-soil properties, which could subsequently affect relationships between soil and water quality, as well as with soil C sequestration and greenhouse gas emissions. We determined soil bulk density, organic C and N fractions, plant-available N, and extractable P on Typic Kanhapludults throughout a 7-year period, in which four long-term (>10 years), no-tillage (NT) water catchments (1.3–2.7 ha each) were divided into two treatments: (1) continuation of NT and (2) paraplowing (PP) in autumn (a form of non-inversion deep ripping) with NT planting. Both summer [cotton (Gossypium hirsutum L.), maize (Zea mays L.), sorghum (Sorghum bicolor L. Moench), soybean (Glycine max L. Merr.)] and winter [wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.)] crops were NT planted throughout the study under each management system. Soil bulk density was reduced with PP compared with NT by as much as 0.15 Mg m−3, but the extent of reduction was inversely related to the time lag between PP operation and sampling event. Soil organic C became significantly enriched with time during this study under NT (0.49 Mg C ha−1 year−1), but not under PP, in which poultry litter was applied equivalent to 5.7 Mg ha−1 year−1 to all water catchments. Soil maintained a highly stratified depth distribution of organic C and N fractions and extractable P under both NT and PP. Inability to perform the PP operation in the last year of this study resulted in rapid convergence of soil bulk density between tillage systems, suggesting that PP had <1-year effectiveness on soil loosening. The high energy cost of PP (ca. 30 kW shank−1) and the lack of sustained improvement in surface-soil properties put into question the value of PP for improving upon long-term NT management in sandy loam and sandy clay loam Ultisols of the Southern Piedmont USA, unless large effects on crop yield, water quality, or other ecosystem processes warrant its use.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号