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1.
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   

2.
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   

3.
This study examined the variations in soil physical, chemical and biological properties from Agave angustifolia fields in three sites with different topographic conditions (valley, hill and mountain), in Oaxaca, Mexico, associated with the tillage systems, disk ploughing (DP), animal drawn ploughing (ADP) and minimum tillage (MT), respectively. Plant ages were 1.5–3.5 years (class 1), 3.6–5.5 years (class 2) and 5.6–7.5 years (class 3). Soil samples were taken at two soil depths (0–20 and 21–40 cm) from plots of 4000 m2 within each site and plant age classes, during the spring of 2005. The main changes in soil properties were found in the mountain site. Soil bulk density (2.0 g cm−3), cone penetration resistance (CPR) (3.96 MPa), 0.7 and 1.0 mm water stable aggregates (WSA) (28.3 g kg−1 and 102.2 g kg−1, respectively) were higher in the mountain site than in the hill and valley fields. This result is consistent with the rocky substrate beneath the shallow soil. Soil organic carbon (SOC) (23.9 g kg−1), available N (23.1 mg kg−1) and soil microbial biomass carbon (SMBC) (969.6 μg g−1) at the mountain site showed the highest values, suggesting that MT practiced in this topographic condition favours the organic matter accumulation and biological activity. Soil microbial biomass carbon and SOC seem to be the soil properties that were mainly affected by the sites and soil management associated with them. For the three sites, SOC, POlsen, available N, exchangeable Na+ and SMBC were higher at 0–20 cm depth than at 21–40 cm depth within each site. Exchangeable Ca2+ and K+, POlsen and CPR increased with plant age. In contrast, available N decreased. Soil chemical properties were more affected by the age of the plant than physical and biological properties. Results reported here represent a reference of the fertility properties of soils cultivated with A. angustifolia, which could be used in further studies focused on management and tillage systems.  相似文献   

4.
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   

5.
Soil is a potential C sink and could offset rising atmospheric CO2. The capacity of soils to store and sequester C will depend on the rate of C inputs from plant productivity relative to C exports controlled by microbial decomposition. Management practices, such as no-tillage and high intensity cropping sequences, have the potential to enhance C and N sequestration in agricultural soils. An investigation was carried out to study the influence of long-term applications of fertilizers and manures on different organic C fractions in a Typic Haplustept under intensive sequence of cropping with maize–wheat–cowpea in a semi-arid sub-tropic of India. In 0–15 cm, the bulk density was lowest (1.52 Mg m−3) in plots treated with 100% NPK + FYM, while the control treatment showed the highest value (1.67 Mg m−3). Balanced application of NPK (100% NPK) showed significantly lower bulk density (1.56 Mg m−3) over either 100% N (1.67 Mg m−3) or 100% NP (1.61 Mg m−3) in surface soils. The application of super-optimal dose of NPK (150% NPK) showed higher total organic C (TOC) (12.9 g C kg−1) over either 50% NPK (9.3 g C kg−1) or 100% NPK (10.0 g C kg−1) in 0–15 cm soil layer. There was an improvement in TOC in 100% NPK or 100% NP (9.3 g C kg−1) over 100% N (8.7 g C kg−1) in the same depth. The application of FYM with 100% NPK showed 15.2, 9.9 and 5.2 g C kg−1 in 0–15, 15–30 and 30–45 cm, respectively. Application of graded doses of NPK from 50 to 150% of recommendation NPK significantly enhanced other organic C fractions like, microbial biomass C (MBC), particulate organic C (POC) and KMnO4 oxidizable C (KMnO4–C) in all the three soil depths. The TOC in 0–45 cm soil depth in 150% NPK (63.5 Mg C ha−1) was increased by 39% over that in 50% NPK treatment (51.5 Mg C ha−1) and 29% over that in 100% NPK treatment (54.1 Mg C ha−1). Integrated use of farmyard manure with 100% NPK (100% NPK + FYM) emerged as the most efficient management system in accumulating largest amount of organic C (72.1 Mg C ha−1) in soil. Nevertheless, this treatment also sequestered highest amount of organic C (731 kg C ha−1 year−1). Particulate organic carbon, a physically protected carbon pool in soil, could well be protected in sub-surface soil layers than in surface soil layer as a means of carbon aggradations. Microbial metabolic quotient (qCO2) was significantly lower in 100% NPK + FYM over other treatments to indicate this to be the most efficient manuring practice to preserve organic carbon in soil where it facilitates aggradations of more recalcitrant organic C in soil. As compared to POC, total TOC proved to be a better predictor of MBC as it strongly correlated with total carbon mineralized from soil.  相似文献   

6.
Soil organic carbon (SOC) pool is the largest among terrestrial pools. The restoration of SOC pool in arable lands represents a potential sink for atmospheric CO2. Restorative management of SOC includes using organic manures, adopting legume-based crop rotations, and converting plow till to a conservation till system. A field study was conducted to analyze soil properties on two farms located in Geauga and Stark Counties in northeastern Ohio, USA. Soil bulk density decreased with increase in SOC pool for a wide range of management systems. In comparison with wooded control, agricultural fields had a lower SOC pool in the 0–30 cm depth. In Geauga County, the SOC pool decreased by 34% in alfalfa (Medicago sativa L.) grown in a complex rotation with manuring and 51% in unmanured continuous corn (Zea mays L.). In Stark County, the SOC pool decreased by 32% in a field systematically amended with poultry manure and 40% in the field receiving only chemical fertilizers. In comparison with continuous corn, the rate of SOC sequestration in Geauga County was 379 kg C ha−1 year−1 in no-till corn (2 years) previously in hay (12 years), 760 kg C ha−1 year−1 in a complex crop rotation receiving manure and chemical fertilizers, and 355 kg C ha−1 year−1 without manuring. The rate of SOC sequestration was 392 kg C ha−1 year−1 on manured field in Stark County.  相似文献   

7.
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   

8.
Cultivation machinery applies large amounts of mechanical energy to the soil and often brings about a decrease in soil organic carbon (SOC). New experiments on the effects of mechanical energy inputs on soil respiration are reported and the results discussed. In the laboratory, a specific energy, K, of 150 J kg−1, similar to that experienced during typical cultivation operations, was applied to soil aggregates using a falling weight. Respiration (carbon dioxide, CO2 emission) of the samples was then measured by an electrical conductimetric method. Basal respiration (when K=0) measured on Chromic Luvisol aggregates, was found to increase with increasing SOC, from 1.88 μg CO2 g−1 h−1 for a permanent fallow soil (SOC=11 g kg−1) to 8.25 μg CO2 g−1 h−1 for a permanent grassland soil (SOC=32 g kg−1). Basal respiration of a Calcic Cambisol, more than doubled (2.0–5.2 μg CO2 g−1 h−1) with increasing gravimetric soil water contents. Mechanical energy inputs caused an initial burst of increased respiration, which lasted up to 4 h. Over the following 4–24 h period, arable soils with lower SOC contents, (11–21 g kg−1), respiration rates dropped back to a level, approximately 1.14 times higher than the basal value. However, grassland soils with higher SOC contents (28–32 g kg−1), increases in this longer-term respiration rate following 150 J kg−1 of energy, were negligible. A field experiment, in which CO2 was measured by infra-red absorption, also showed that tillage stimulated increased levels of soil respiration for periods ranging from 12 h to more than one week. The highest respiration rates, 80 mg CO2 m−2 h−1 were associated with high energy, powered tillage on clay soils. On the same soil, low energy draught tillage resulted in a respiration rate of approximately half this value. The results of these experiments are discussed in relation to equilibrium levels of soil organic matter. The application of known quantities of mechanical energy to soil aggregates under laboratory conditions, in order to simulate the effect of different cultivation practices, when combined with the subsequent measurement of soil respiration, can provide useful indication of the likely consequences of soil management on SOC.  相似文献   

9.
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   


10.
Residue retention and reduced tillage are both conservation agricultural management options that may enhance soil organic carbon (SOC) stabilization in tropical soils. Therefore, we evaluated the effects of long-term tillage and residue management on SOC dynamics in a Chromic Luvisol (red clay soil) and Areni-Gleyic Luvisol (sandy soil) in Zimbabwe. At the time of sampling the soils had been under conventional tillage (CT), mulch ripping (MR), clean ripping (CR) and tied ridging (TR) for 9 years. Soil was fully dispersed and separated into 212–2000 μm (coarse sand), 53–212 μm (fine sand), 20–53 μm (coarse silt), 5–20 μm (fine silt) and 0–5 μm (clay) size fractions. The whole soil and size fractions were analyzed for C content. Conventional tillage treatments had the least amount of SOC, with 14.9 mg C g−1 soil and 4.2 mg C g−1 soil for the red clay and sandy soils, respectively. The highest SOC content was 6.8 mg C g−1 soil in the sandy soil under MR, whereas for the red clay soil, TR had the highest SOC content of 20.4 mg C g−1 soil. Organic C in the size fractions increased with decreasing size of the fractions. In both soils, the smallest response to management was observed in the clay size fractions, confirming that this size fraction is the most stable. The coarse sand-size fraction was most responsive to management in the sandy soil where MR had 42% more organic C than CR, suggesting that SOC contents of this fraction are predominantly controlled by amounts of C input. In contrast, the fine sand fraction was the most responsive fraction in the red clay soil with a 66% greater C content in the TR than CT. This result suggests that tillage disturbance is the dominant factor reducing C stabilization in a clayey soil, probably by reducing C stabilization within microaggregates. In conclusion, developing viable conservation agriculture practices to optimize SOC contents and long-term agroecosystem sustainability should prioritize the maintenance of C inputs (e.g. residue retention) to coarse textured soils, but should focus on the reduction of SOC decomposition (e.g. through reduced tillage) in fine textured soils.  相似文献   

11.
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   

12.
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   

13.
In view of their potential benefits, reduced or no tillage (NT) systems are being advocated worldwide. Concerns about impairment of some soil conditions, however, cast doubt on their unqualified acceptance. We evaluated the effects of 6 years of tillage and residue management on bulk density, penetration resistance, aggregation and infiltration rate of a Black Chernozem at Innisfail (loam, 65 g kg−1 organic matter, Udic Boroll) and a Gray Luvisol at Rimbey (loam, 31 g kg−1 organic matter, Boralf) cropped to monoculture spring barley (Hordeum vulgare L.) in a cool temperate climate in Alberta, Canada. Tillage systems were no tillage and tillage with rototilling (T), and two residue levels were straw removed (−S) and straw retained (+S). Bulk density (BD) of the 0–7.5 and 7.5–15 cm depths was significantly greater under NT (1.13–1.58 Mg m−3) than under T (0.99–1.41 Mg m−3) in both soils, irrespective of residue management. In both soils, penetration resistance (PR) was greater under NT than under T to 15 cm depth. Residue retention significantly reduced PR of the 0–10 cm soil in NT, but not in T. In the 0–5 cm depth of the Black Chernozem, the >2 mm fraction of dry aggregates was highest under NT + S (72%), and lowest under T − S (50%). The wind-erodible fraction (dry aggregates <1 mm size) was smallest (18%) under NT + S and largest (39%) under T − S. Soil aggregation benefited more from NT than from residue retention. Proportion of wind-erodible aggregates was generally greater in the Gray Luvisol than in the Black Chernozem. In the Black Chernozem, steady-state infiltration rate (IR) was significantly lower (33%) under NT than under T. Residue retention improved IR in both NT and T. In the Gray Luvisol, IR was not significantly affected by tillage and residue management. Despite firmer soil, NT and residue retention are recommended to improve aggregation in the cool temperate region of Western Canada.  相似文献   

14.
Improved-fallow agroforestry systems are increasingly being adopted in the humid tropics for soil fertility management. However, there is little information on trace gas emissions after residue application in these systems, or on the effect of tillage practice on emissions from tropical agricultural systems. Here, we report a short-term experiment in which the effects of tillage practice (no-tillage versus tillage to 15 cm depth) and residue quality on emissions of N2O, CO2 and CH4 were determined in an improved-fallow agroforestry system in western Kenya. Emissions were increased following tillage of Tephrosia candida (2.1 g N2O-N ha−1 kg N applied−1; 759 kg CO2-C ha−1 t C applied−1; 30 g CH4-C ha−1 t C applied−1) and Crotalaria paulina residues (2.8 g N2O-N ha−1 kg N applied−1; 967 kg CO2-C ha−1 t C applied−1; 146 g CH4-C ha−1 t C applied−1) and were higher than from tillage of natural-fallow residues (1.0 g N2O-N ha−1 kg N applied−1; 432 kg CO2-C ha−1 t C applied−1; 14.7 g CH4-C ha−1 t C applied−1) or from continuous maize cropping systems. Emissions from these fallow treatments were positively correlated with residue N content (r = 0.62–0.97; P < 0.05) and negatively correlated with residue lignin content (r = −0.56, N2O; r = −0.92, CH4; P < 0.05). No-tillage of surface applied Tephrosia residues lowered the total N2O and CO2 emitted over 99 days by 0.33 g N2O-N ha−1 kg N applied−1 and 124 kg CO2-C ha−1 t C applied−1, respectively; estimated to provide a reduction in global warming potential of 41 g CO2 equivalents. However, emissions were increased from this treatment over the first 2 weeks. The responses to tillage practice and residue quality reported here need to be verified in longer term experiments before they can be used to suggest mitigation strategies appropriate for all three greenhouse gases.  相似文献   

15.
Long-term field experiments are among the best means to predict soil management impacts on soil carbon storage. Soil organic carbon (SOC) and natural abundance 13C (δ13C) were sensitive to tillage, stover harvest, and nitrogen (N) management during 13 years of continuous corn (Zea mays L.), grown on a Haplic Chernozem soil in Minnesota. Contents of SOC in the 0–15 cm layer in the annually-tilled [moldboard (MB) and chisel (CH)] plots decreased slightly with years of corn after a low input mixture of alfalfa (Medicago sativum L.) and oat (Avena sativa L.) for pasture; stover harvest had no effect. Storage of SOC in no-till (NT) plots with stover harvested remained nearly unchanged at 55 Mg ha−1 with time, while that with stover returned increased about 14%. The measured δ13C increased steadily with years of corn cropping in all treatments; the NT with stover return had the highest increase. The N fertilization effects on SOC and δ13C were most evident when stover was returned to NT plots. In the 15–30 cm depth, SOC storage decreased and δ13C values increased with years of corn cropping under NT, especially when stover was harvested. There was no consistent temporal trend in SOC storage and δ13C values in the 15–30 cm depth when plots received annual MB or CH tillage. The amount of available corn residue that was retained in SOC storage was influenced by all three management factors. Corn-derived SOC in the 0–15 cm and the 15–30 cm layers of the NT system combined was largest with 200 kg N ha−1 and no stover harvest. The MB and CH tillage systems did not influence soil storage of corn-derived SOC in either the 0–15 or 15–30 cm layers. The corn-derived SOC as a fraction of SOC after 13 years fell into three ranges: 0.05 for the NT with stover harvested, 0.15 for the NT with no stover harvest, and 0.09–0.10 for treatments with annual tillage; N rate had no effect on this fraction. Corn-derived SOC expressed as a fraction of C returned was positively biased when C returned in the roots was estimated from recovery of root biomass. The half-life for decomposition of the original or relic SOC was longer when stover was returned, shortened when stover was harvested and N applied, and sharply lengthened when stover was not harvested and N was partially mixed with the stover. Separating SOC storage into relic and current crop sources has significantly improved our understanding of the main and interacting effects of tillage, crop residue, and N fertilization for managing SOC accumulation in soil.  相似文献   

16.
Under semi-arid Mediterranean conditions, limited moisture is the main constraint to rainfed cropping with wheat (Triticum aestivum), barley (Hordeum vulgare), and food and forage legumes. With increasing land-use pressure, moisture-conserving fallowing is being replaced by continuous cropping, which is considered an unsustainable practice. Thus, a long-term trial with durum wheat (T. turgidum var. durum) was established in 1983 at Tel Hadya, Aleppo, Syria (mean annual rainfall 330 mm) to assess alternative rotation options to fallow and continuous cropping. Nitrogen (N) and grazing/residue management were secondary factors. Soil aggregation, infiltration, hydraulic conductivity, and total soil organic matter and component fractions (fulvic and humic acids and polysaccharides) were determined at the end of 12 years. Some rotations, e.g., medic (Medicago sativa) and vetch (Vicia faba), significantly increased soil organic matter (12.5–13.8 g kg−1 versus 10.9–11 g kg−1 for continuous wheat and wheat/fallow). All measurements, or indices, indicated parallel trends with increasing organic matter, e.g., coefficients of macro-structure, micro-aggregation, and water-stable aggregates, and decreasing dispersion. Similarly, legume rotations had higher infiltration rates (16.2–21.8 cm h−1 versus 13.9–14.4 cm h−1 with continuous wheat and wheat/fallow) and hydraulic conductivity rates (8.7–12.4 cm h−1 versus 6.2–7.4 cm h−1 with continuous wheat and wheat/fallow). We conclude that cereal/legume rotations, in addition to being biologically and economically attractive, also enhance soil quality and thus promote soil use sustainability in fragile semi-arid areas as in the Mediterranean zone.  相似文献   

17.
Soil carbon (C) losses and soil translocation from tillage operations have been identified as causes of soil degradation and soil erosion. The objective of this work was to quantify the variability in tillage-induced carbon dioxide (CO2) loss by moldboard (MP) and chisel (CP) plowing across an eroded landscape and relate the C loss to soil properties. The study site was a 4 ha wheat (Triticum aestivum L. cv. Marshall) field with rolling topography and five soil types in the Svea-Barnes complex in west central Minnesota (N. Latitude = 45°41′W, Longitude = 95°43′). Soil properties were measured at several depths at a 10 m spacing along north–south (N–S) and west–east (W–E) transects through severely eroded, moderately eroded and non-eroded sites. Conventional MP (25 cm deep) and CP (15 cm deep) equipment were used along the pre-marked transects. Gas exchange measurements were obtained with a large, portable chamber within 2 m of each sample site following tillage. The measured CO2 fluxes were largest with the MP > CP > not tilled (before tillage). The variation in 24 h cumulative CO2 flux from MP was nearly 3-fold on the N–S transect and 4-fold on the W–E transect. The surface soil organic C on the transects was lowest on the eroded knolls at 5.1 g C kg−1 and increased to 19.6 g C kg−1 in the depositional areas. The lowest CO2 fluxes were measured from severely eroded sites which indicated that the variation in CO2 loss was partially reflected by the degradation of soil properties caused by historic tillage-induced soil translocation with some wind and water erosion.

The spatial variation across the rolling landscape complicates the determination of non-point sources of soil C loss and suggests the need for improved conservation tillage methods to maintain soil and air quality in agricultural production systems.  相似文献   


18.
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   

19.
Many factors including management history, soil type, climate, and soil landscape processes affect the dynamics of soil organic carbon (SOC). The primary objective of this research was to determine the effects of no-tillage and tillage systems on the SOC content after 12 years of controlled treatments. A tillage experiment with three treatments (no-till (NT), chisel plow (CP) and moldboard plow (MP)) was initiated in the spring of 1989 in southern Illinois. The plot area was previously in a tall fescue hayland for 15 years and had a 6% slope. Maize (Zea mays L.) and soybean (Glycine max L. Merr.) were grown in the plot area on a yearly rotation system starting with maize. Periodically, the SOC content of various soil layers, to a depth of either 30 or 75 cm, was measured and expressed on both a gravimetric and volumetric basis. After 12 years, the 0–15 cm surface soil layer of MP was significantly lower in SOC than the NT and CP plots. For all but 2 values, the significance of findings did not change with the form of expression (gravimetric versus volumetric). The surface layer (0–15 cm), subsoil (15–75 cm), and rooting zone (0–75 cm) of all treatments had reduction in SOC on a volumetric basis when compared to the pre-treatment values for sod. At the end of the 12-year study, the MP system had significantly less SOC in the surface layer, subsurface layer and rooting zone than the NT system at comparable depths. After 12 years of tillage under a maize–soybean rotation, the NT treatment sequestered or maintained more SOC stock (47.0 Mt ha−1) than the CP (43.7 Mt ha−1) and MP (37.7 Mt ha−1) treatments. The annual rate of SOC stock build up in the root zone (0–75 cm), above the MP system base, was 0.71 Mt ha−1 year−1 for the NT system and 0.46 Mt ha−1 year−1 for the CP system. For land coming out of the Conservation Reserve Program and returning to row crop production, NT and CP systems would maintain more SOC stock than MP system and reduce CO2 emissions to the atmosphere.  相似文献   

20.
Crop rotation effects, due to emerging soil ecological interactions and processes that occur with time, can have a major impact on crop productivity and soil health. 2-year potato (Solanum tuberosum L.) rotation studies were conducted during an 11-year period on a fine sandy loam (Orthic Podzol) under a cool, humid climate in Prince Edward Island in eastern Canada. Rotation partners included Italian ryegrass (Lolium multiflorum Lam.), red clover (Trifolium pratense L.), and barley (Hordeum vulgare L.). The study objective was to assess trends in yield parameters, populations and diversity in nematodes and soil-borne pathogens, and soil structural stability and organic matter retention with time. Italian ryegrass had the largest biomass of both herbage (6.5 Mg ha−1) and roots (4.8 Mg ha−1), compared to red clover or barley. Averaged across 9 years, potato tuber yield was highest under Italian ryegrass (35.0 Mg ha−1) and lowest under red clover (31.1 Mg ha−1) rotations. Differences in tuber yield among rotations was associated with soil N limitation and nematode activity, but was not evident until Year 6. Population densities of specific plant parasitic nematodes recovered from roots and soil were generally low and varied according to host plant. Root lesion (Pratylenchus spp.) and root-knot (Meloidogyne spp.) nematodes were more prevalent under red clover compared to other rotational crops. Stunt (Merlinius spp. and Tylenchorhynchus spp.) nematodes were more common under Italian ryegrass. The main organisms associated with tuber-borne disease were Rhizoctonia solani, Streptomyces spp., Fusarium spp., and Helminthosporium solani. The greatest reduction in tuber-borne diseases occurred with the potato–red clover rotation but significant differences were infrequent. Soil structural form throughout the soil profile (to 30 cm depth) was not adversely affected by the rotational treatments during the duration of the study, while soil structural stability at the soil surface (0–10 cm) was significantly improved. Losses of soil organic C, during the 11-year period ranged from marginal (4%) for rotations with Italian ryegrass, to significant (16%) under the barley rotation. Computer simulations, using the Century model, illustrated the importance of C inputs to maintain soil organic matter levels. Overall, potato crop productivity and soil organic C were generally maintained in rotations that contained Italian ryegrass, but declined under rotations with red clover and barley.  相似文献   

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