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1.
Nitrous oxide (N2O) and methane (CH4) emitted by anthropogenic activities have been linked to the observed and predicted climate change. Conservation tillage practices such as no-tillage (NT) have potential to increase C sequestration in agricultural soils but patterns of N2O and CH4 emissions associated with NT practices are variable. Thus, the objective of this study was to evaluate the effects of tillage practices on N2O and CH4 emissions in long-term continuous corn (Zea mays) plots. The study was conducted on continuous corn experimental plots established in 1962 on a Crosby silt loam (fine, mixed, mesic Aeric Ochraqualf) in Ohio. The experimental design consisted of NT, chisel till (CT) and moldboard plow till (MT) treatments arranged in a randomized block design with four replications. The N2O and CH4 fluxes were measured for 1-year at 2-week intervals during growing season and at 4-week intervals during the off season. Long-term NT practice significantly decreased soil bulk density (ρb) and increased total N concentration of the 0–15 cm layer compared to MT and CT. Generally, NT treatment contained higher soil moisture contents and lower soil temperatures in the surface soil than CT and MT during summer, spring and autumn. Average daily fluxes and annual N2O emissions were more in MT (0.67 mg m−2 d−1 and 1.82 kg N ha−1 year−1) and CT (0.74 mg m−2 d−1 and 1.96 kg N ha−1 year−1) than NT (0.29 mg m−2 d−1 and 0.94 kg N ha−1 year−1). On average, NT was a sink for CH4, oxidizing 0.32 kg CH4-C ha−1 year−1, while MT and CT were sources of CH4 emitting 2.76 and 2.27 kg CH4-C ha−1 year−1, respectively. Lower N2O emission and increased CH4 oxidation in the NT practice are attributed to decrease in surface ρb, suggesting increased gaseous exchange. The N2O flux was strongly correlated with precipitation, air and soil temperatures, but not with gravimetric moisture content. Data from this study suggested that adoption of long-term NT under continuous corn cropping system in the U.S. Corn Belt region may reduce GWP associated with N2O and CH4 emissions by approximately 50% compared to MT and CT management.  相似文献   

2.
The greenhouse gases CO2 and N2O emissions were quantified in a long-term experiment in northern France, in which no-till (NT) and conventional tillage (CT) had been differentiated during 32 years in plots under a maize–wheat rotation. Continuous CO2 and periodical N2O soil emission measurements were performed during two periods: under maize cultivation (April 2003–July 2003) and during the fallow period after wheat harvest (August 2003–March 2004). In order to document the dynamics and importance of these emissions, soil organic C and mineral N, residue decomposition, soil potential for CO2 emission and climatic data were measured. CO2 emissions were significantly larger in NT on 53% and in CT on 6% of the days. From April to July 2003 and from November 2003 to March 2004, the cumulated CO2 emissions did not differ significantly between CT and NT. However, the cumulated CO2 emissions from August to November 2003 were considerably larger for NT than for CT. Over the entire 331 days of measurement, CT and NT emitted 3160 ± 269 and 4064 ± 138 kg CO2-C ha−1, respectively. The differences in CO2 emissions in the two tillage systems resulted from the soil climatic conditions and the amounts and location of crop residues and SOM. A large proportion of the CO2 emissions in NT over the entire measurement period was probably due to the decomposition of old weathered residues. NT tended to emit more N2O than CT over the entire measurement period. However differences were statistically significant in only half of the cases due to important variability. N2O emissions were generally less than 5 g N ha−1 day−1, except for a few dates where emission increased up to 21 g N ha−1 day−1. These N2O fluxes represented 0.80 ± 0.15 and 1.32 ± 0.52 kg N2O-N ha−1 year−1 for CT and NT, respectively. Depending on the periods, a large part of the N2O emissions occurred was probably induced by nitrification, since soil conditions were not favorable for denitrification. Finally, for the period of measurement after 32 years of tillage treatments, the NT system emitted more greenhouses gases (CO2 and N2O) to the atmosphere on an annual basis than the CT system.  相似文献   

3.
The introduction of crop management practices after conversion of Amazon Cerrado into cropland influences soil C stocks and has direct and indirect consequences on greenhouse gases (GHG) emissions. The aim of this study was to quantify soil C sequestration, through the evaluation of the changes in C stocks, as well as the GHG fluxes (N2O and CH4) during the process of conversion of Cerrado into agricultural land in the southwestern Amazon region, comparing no-tillage (NT) and conventional tillage (CT) systems. We collected samples from soils and made gas flux measurements in July 2004 (the dry season) and in January 2005 (the wet season) at six areas: Cerrado, CT cultivated with rice for 1 year (1CT) and 2 years (2CT), and NT cultivated with soybean for 1 year (1NT), 2 years (2NT) and 3 years (3NT), in each case after a 2-year period of rice under CT. Soil samples were analyzed in both seasons for total organic C and bulk density. The soil C stocks, corrected for a mass of soil equivalent to the 0–30-cm layer under Cerrado, indicated that soils under NT had generally higher C storage compared to native Cerrado and CT soils. The annual C accumulation rate in the conversion of rice under CT into soybean under NT was 0.38 Mg ha−1 year−1. Although CO2 emissions were not used in the C sequestration estimates to avoid double counting, we did include the fluxes of this gas in our discussion. In the wet season, CO2 emissions were twice as high as in the dry season and the highest N2O emissions occurred under the NT system. There were no CH4 emissions to the atmosphere (negative fluxes) and there were no significant seasonal variations. When N2O and CH4 emissions in C-equivalent were subtracted (assuming that the measurements made on 4 days were representative of the whole year), the soil C sequestration rate of the conversion of rice under CT into soybean under NT was 0.23 Mg ha−1 year−1. Although there were positive soil C sequestration rates, our results do not present data regarding the full C balance in soil management changes in the Amazon Cerrado.  相似文献   

4.
We examined the effects of various tillage intensities: no-tillage (NT), minimum tillage with chisel plow (MT), conventional tillage with mouldboard plow (CT), and zone-tillage subsoiling with a paraplow (ZT) applied in alternate years in rotation with NT, on the topsoil profile distribution (0–30 cm) of pH, soil organic carbon (SOC), organic N and available nutrients on a semi-arid soil from Central Spain. The equivalent depth approach was used to compare SOC, N and nutrient stocks in the various tillage treatments. Measurements made at the end of 5 years showed that in the 0–30 cm depth, SOC and N had increased under NT and ZT compared with MT and CT. Most dramatic changes occurred within the 0–5 cm depth where plots under NT and ZT had respectively 7.0 Mg ha−1 and 6.2 Mg ha−1 more SOC and 0.5 Mg ha−1 and 0.3 Mg ha−1 more N than under MT or CT. No-tillage and ZT plots, however, exhibited strong vertical gradients of SOC and N with concentrations decreasing from 0–5 to 20–30 cm. In the 0–20 cm layer, higher concentrations of P and K under NT and ZT than under MT or CT were also found. Soil pH under NT and ZT was 0.3 units lower than under MT or CT at a depth of 0–5 cm. This acidifying effect was restricted at the surface layer and in the 20–30 cm interval, pH values under NT and ZT were higher than in MT and CT plots. These results suggest that in the soil studied, ZT in rotation with NT maintain most advantages associated with NT, and present a definite potential for use as a partial-width rotational tillage practice.  相似文献   

5.
Methane (CH4) oxidation potential of soils decreases with cultivation, but limited information is available regarding the restoration of that capacity with implementation of reduced tillage practices. A study was conducted to assess the impact of tillage intensity on CH4 oxidation and several C-cycling indices including total and active microbial biomass C (t-MBC, a-MBC), mineralizable C (Cmin) and N (Nmin), and aggregate-protected C. Intact cores and disturbed soil samples (0–5 and 5–15 cm) were collected from a corn (Zea mays L.)–soybean (Glycine max L. Merr.) rotation under moldboard-plow (MP), chisel-plow (CP) and no-till (NT) for 8 years. An adjacent pasture (<25 years) and secondary growth forest (>60 years) soils were also sampled as references. At all sites, soil was a Kokomo silty clay loam (mesic Typic Argiaquolls). Significant tillage effects on t-MBC and protected C were found in the 0–5 cm depth. Protected C, a measure of C retained within macro-aggregates and defined as the difference in Cmin (CO2 evolved in a 56 days incubation) between intact and sieved (<2 mm) soil samples, amounted to 516, 162 and 121 mg C kg−1 soil in the 0–5 cm layer of the forest, pasture and NT soils, respectively. Protected C was negligible in the CP and MP soils. Methane uptake rate (μg CH4-C kg−1 soil per day, under ambient CH4) was higher in forest (2.70) than in pasture (1.22) and cropland (0.61) soils. No significant tillage effect on CH4 oxidation rate was detected (MP: 0.82; CP: 0.41; NT: 0.61). These results underscore the slow recovery of the CH4 uptake capacity of soils and suggest that, to have an impact, tillage reduction may need to be implemented for several decades.  相似文献   

6.
Crop residue retention is important for sequestering soil organic carbon (SOC), controlling soil erosion, and improving soil quality. Magnitude of residue management impacts on soil structural properties and SOC sequestration is, however, site specific. This study assessed long-term (10 year) impacts of three levels (0, 8, and 16 Mg ha−1 on a dry matter basis) of wheat (Triticum aestivum L.) straw applied annually on SOC concentration and physical properties of the bulk soil and individual 5- to 8-mm aggregates for the 0- to 50-cm soil depth under no-till (NT) on a Crosby silt loam (fine, mixed, active, mesic Aeric Epiaqualfs) in central Ohio. This study also quantified relationships between soil properties and straw-induced changes in SOC concentration. Changes in soil properties due to straw mulching were mostly confined to the upper 5 cm of the soil. Mulching increased SOC concentration, but it did not significantly change cone index (CI) and shear strength (SHEAR). Within the upper 0–5-cm soil depth, mulching decreased bulk density (ρb) by 40–50%, aggregate density (ρagg) by 30–40%, and particle density (ρs) by 10–15%, and increased tensile strength (TS) of aggregates by up to 14 times as compared to unmulched soil. At the same depth, soil with mulch retained >30% more water than soil without mulch from 0 to −1500 kPa potentials. The SOC amount was 16.0 Mg ha−1 under no straw, 25.3 Mg ha−1 under 8 Mg ha−1 straw, and 33.5 Mg ha−1 under 16 Mg ha−1 straw in the 0- to 10-cm depth. Below 10 cm, differences in SOC pool between mulched and unmulched soil were not significant. Overall, SOC from 0- to 50-cm depth was 82.5 Mg ha−1 for unmulched soil, 94.1 Mg ha−1 for 8 Mg ha−1 mulch, and 104.9 Mg ha−1 for 16 Mg ha−1. About 33% of C added with straw over the 10-year period was sequestered in soil. This means that 2/3 of the wheat straw applied was not converted to SOC and most probably was lost as emissions of CO2 and CH4. The annual rate of total C accrual was 1.2 Mg ha−1 in soil mulched with 8 Mg ha−1 and 2.2 Mg ha−1 in soil mulched with 16 Mg ha−1 of straw in the 0- to 50-cm depth. The percentage of macroaggregates (>5-mm) was six times higher under 8 Mg ha−1 of straw and 12 times higher under 16 Mg ha−1 compared to unmulched treatments. Macroaggregates contained greater SOC than microaggregates in mulched soil. The SOC concentration explained the variability in aggregate properties by as much as 96%. Overall, long-term straw mulching increased SOC concentration and improved near-surface aggregate properties.  相似文献   

7.
The objective of this work was to identify soil parameters potentially useful to monitor soil quality under different soil management and crop rotation systems. Microbiological and chemical parameters were evaluated in a field experiment in the State of Paraná, southern Brazil, in response to soil management [no-tillage (NT) and conventional tillage (CT)] and crop rotation [including grain (soybean, S; maize, M; wheat, W) and legume (lupin, L.) and non-legume (oat, O) covers] systems. Three crop rotation systems were evaluated: (1) (O/M/O/S/W/S/L/M/O/S), (2) (O/S/L/M/O/S/W/S/L/M), and (3) (O/S/W/S/L/M/O/M/W/M), and soil parameters were monitored after the fifth year. Before ploughing, CO2-emission rates were similar in NT and CT soils, but plough increased it by an average of 57%. Carbon dioxide emission was 13% higher with lupin residues than with wheat straw; decomposition rates were rapid with both soil management systems. Amounts of microbial biomass carbon and nitrogen (MB-C and MB-N, respectively) were 80 and 104% higher in NT than in CT, respectively; however, in general these parameters were not affected by crop rotation. Efficiency of the microbial community was significantly higher in NT: metabolic quotient (qCO2) was 55% lower than in CT. Soluble C and N levels were 37 and 24% greater in NT than in CT, respectively, with no effects of crop rotation. Furthermore, ratios of soluble C and N contents to MB-C and MB-N were consistently lower in NT, indicating higher immobilization of C and N per unit of MB. The decrease in qCO2 and the increase in MB-C under NT allowed enhancements in soil C stocks, such that in the 0–40 cm profile, a gain of 2500 kg of C ha−1 was observed in relation to CT. Carbon stocks also varied with crop rotation, with net changes at 0–40 cm of 726, 1167 and −394 kg C ha−1 year, in rotations 1, 2 and 3, respectively. Similar results were obtained for the N stocks, with 410 kg N ha−1 gained in NT, while crop rotations 1, 2 and 3 accumulated 71, 137 and 37 kg of N ha−1 year−1, respectively. On average, microbial biomass corresponded to 2.4 and 1.7% of the total soil C, and 5.2 and 3.2% of the N in NT and CT systems, respectively. Soil management was the main factor affecting soil C and N levels, but enhancement also resulted from the ratios of legumes and non-legumes in the rotations. The results emphasize the importance of microorganisms as reservoirs of C and N in tropical soils. Furthermore, the parameters associated with microbiological activity were more responsive to soil management and crop rotation effects than were total stocks of C and N, demonstrating their usefulness as indicators of soil quality in the tropics.  相似文献   

8.
Diversification of production is a concern for farmers in many regions of the world, raising a renewed interest in crop-animal rotations. However little information is available on whether the introduction of grazing animals in a no-till system could be a sustainable practice. The present long-term study was carried out in the semiarid region of Argentina, on an Entic Haplustoll (A, AC, C and Ck profile). The experimental plots were established in August 1993, with two treatments, no-till (NT) and conventional tillage (CT). Stubble was regularly used for grazing until 2002, when plots were divided into grazed (G) and non-grazed (NG) sub-treatments. Soil samples were taken at 0–0.10 and 0.10–0.20 m depth at the beginning of the experiment (1993) and during 2007, with the following determinations: clay + silt contents, bulk density (BD), total carbon (C), total nitrogen (N), available P, C contents of aggregate fractions of 2000–100 (POC), 100–50 (IOC) and <50 (FOC) μm diameter, aggregate size distribution and mean weight diameter change. NT showed a strong effect on all analyzed soil attributes: it had higher total carbon stocks (NT 16.6 Mg ha−1 vs. CT 13.2 Mg ha−1) and higher amounts in all C fractions, even in FOC (11.3 Mg ha−1 vs. 9.2 Mg ha−1). For BD, we found no difference between NT and CT at the surface and an even lower value for NT at 0.10–0.20 m depth. Under NT no depletion of available P occurred, while CT lost about 23 kg ha−1. Grazing had a negative effect on BD when averaging BD data across tillage systems, while there was no effect on aggregate stability, and a positive one on the proportion of >8 mm aggregates (23.3% vs. 11.7% for CT G and CT NG, respectively). C stratification showed a differential effect of grazing: NT G had the highest index (1.31) and CT G the lowest one (0.98). Our results indicated that the introduction of grazing animals in NT crop systems would not be detrimental to soil conditions and quality, at least in semiarid conditions of Argentina.  相似文献   

9.
Conservation tillage practices are commonly used to reduce erosion; however, in fields that have been in no-tillage (NT) for long periods, compaction from traffic can restrict infiltration. Rotational tillage (RT) is a common practice that producers use in the central corn-belt of the United States, and could potentially reduce soluble nutrient loads to surface waters. The objectives of this study were to determine the first year impacts of converting from long-term NT to (RT) on N and P losses through runoff. Plots (2 m × 1 m) were constructed in two fields that had been in NT corn–soybean rotation for the previous 15 years. One field remained in NT management, while RT was initiated prior to planting corn in the other field using a soil finisher. Variable-intensity rainfall simulations occurred before and after fertilization with urea (224 kg N ha−1) and triple superphosphate (112 kg P ha−1). Rainfall was simulated at (1) 50 mm h−1 for 50 min; (2) 75 mm h−1 for 15 min; (3) 25 mm h−1 for 15 min; (4) 100 mm h−1 for 15 min. Runoff volumes and nutrient (NH4-N, NO3-N and dissolved P [DP]) concentrations were greater from the NT field than the RT field before and after fertilization.Dissolved P concentrations in runoff prior to fertilization were greater during the 50 mm h−1 rainfall period (0.09 mg L−1) compared to the other periods (0.03 mg L−1). Nutrient concentrations increased by 10–100-fold when comparing samples taken after fertilization to those taken prior to fertilization. Nutrient loads were greater prior to and after fertilization from the NT treatment. Prior to fertilization, NT resulted in 83 g ha−1 greater NH4-N and 32.4 g ha−1 greater dissolved P losses than RT treatment. After fertilization, NT was observed to lose 5.3 kg ha−1 more NH4-N, 1.3 kg ha−1 more NO3-N, and 2.4 kg ha−1 more dissolved P than RT. It is typically difficult to manage land to minimize P and N losses simultaneously; however, in the short term, tillage following long-term NT resulted in lowering the risk of transport of soluble N and P to surface water.  相似文献   

10.
Broiler chicken (Gallus gallus) manure, a rich source of plant nutrients, is generated in large quantities in southeastern USA where many row crops, such as corn (Zea mays L.), are also extensively grown. However, the use of broiler manure as an economical alternative source of nutrients for corn production has not been extensively explored in this region. This study was conducted to examine the use of broiler litter as a source of nutrients for corn production, as influenced by tillage and litter rate, and any residual effects following application. In addition, the consequence of litter application to soil test nutrient levels, particularly P, Zn and Cu, was explored. The treatments consisted of two rates of broiler litter application, 11 and 22 Mg ha−1 on a wet weight basis, and one rate of chemical fertilizer applied under no-till and conventional tillage systems. Treatments were replicated three times in a randomized complete block design. Corn was grown with broiler litter and inorganic fertilizer applied to the same plots each year from 1998 to 2001. In 2002 and 2003, corn was planted no-till, but only N fertilizer was applied in order to make use of other residual litter nutrients. Soil samples were taken yearly in the spring prior to litter application and 4 years after the cessation of litter application to evaluate the status of the residual nutrients in soil. Two years out of the 4-year experiment, broiler litter application produced significantly greater corn grain yield than equivalent chemical fertilizer application and produced similar grain yield in the other 2 years. Corn grain yield was significantly greater under no-till in 1999, but significantly greater under conventional-till in 2000, and no difference between the two tillage systems were observed in 1998 and 2001. With 4 years of litter application, Mehlich-3 P increased from an initial 18 mg kg−1 to 156 mg kg−1 with 11 Mg ha−1 litter and to 257 mg kg−1 with 22 Mg ha−1 litter. For every 6 kg ha−1 of P applied in poultry litter Mehlich-3 P was increased by 1 mg kg−1. Modest increases in Mehlich-3 Cu and Zn did not result in phytotoxic levels. This study indicated that an optimum rate of broiler litter as a primary fertilizer at 11 Mg ha−1 applied in 4 consecutive years on a silt loam soil produced corn grain yields similar to chemical fertilizer under both no-till and conventional tillage systems and kept soil test P, Cu and Zn levels below values considered to be harmful to surface water quality or the crop.  相似文献   

11.
Maintaining and/or conserving organic carbon (C) and nitrogen (N) concentrations in the soil using management practices can improve its fertility and productivity and help to reduce global warming by sequestration of atmospheric CO2 and N2. We examined the influence of 6 years of tillage (no-till, NT; chisel plowing, CP; and moldboard plowing, MP), cover crop (hairy vetch (Vicia villosa Roth.) vs. winter weeds), and N fertilization (0, 90, and 180 kg N ha−1) on soil organic C and N concentrations in a Norfolk sandy loam (fine-loamy, siliceous, thermic, Typic Kandiudults) under tomato (Lycopersicon esculentum Mill.) and silage corn (Zea mays L.). In a second experiment, we compared the effects of 7 years of non-legume (rye (Secale cereale L.)) and legume (hairy vetch and crimson clover (Trifolium incarnatum L.)) cover crops and N fertilization (HN (90 kg N ha−1 for tomato and 80 kg N ha−1 for eggplant)) and FN (180 kg N ha−1 for tomato and 160 kg N ha−1 for eggplant)) on soil organic C and N in a Greenville fine sandy loam (fine-loamy, kaolinitic, thermic, Rhodic Kandiudults) under tomato and eggplant (Solanum melogena L.). Both experiments were conducted from 1994 to 2000 in Fort Valley, GA. Carbon concentration in cover crops ranged from 704 kg ha−1 in hairy vetch to 3704 kg ha−1 in rye in 1999 and N concentration ranged from 77 kg ha−1 in rye in 1996 to 299 kg ha−1 in crimson clover in 1997. With or without N fertilization, concentrations of soil organic C and N were greater in NT with hairy vetch than in MP with or without hairy vetch (23.5–24.9 vs. 19.9–21.4 Mg ha−1 and 1.92–2.05 vs. 1.58–1.76 Mg ha−1, respectively). Concentrations of organic C and N were also greater with rye, hairy vetch, crimson clover, and FN than with the control without a cover crop or N fertilization (17.5–18.4 vs. 16.5 Mg ha−1 and 1.33–1.43 vs. 1.31 Mg ha−1, respectively). From 1994 to 1999, concentrations of soil organic C and N decreased by 8–16% in NT and 15–25% in CP and MP. From 1994 to 2000, concentrations of organic C and N decreased by 1% with hairy vetch and crimson clover, 2–6% with HN and FN, and 6–18% with the control. With rye, organic C and N increased by 3–4%. Soil organic C and N concentrations can be conserved and/or maintained by reducing their loss through mineralization and erosion, and by sequestering atmospheric CO2 and N2 in the soil using NT with cover crops and N fertilization. These changes in soil management improved soil quality and productivity. Non-legume (rye) was better than legumes (hairy vetch and crimson clover) and N fertilization in increasing concentrations of soil organic C and N.  相似文献   

12.
Broadcasting of urea to agricultural soils can result in considerable losses by NH3 volatilization. However, it is unclear if the impact of this practice on NH3 emissions is further enhanced when performed on no-till (NT) soils. The objective of this study was to compare NH3 volatilization following broadcasting of urea to NT and moldboard plowed (MP) soils. Intact soil cores were taken shortly after harvest from NT and MP plots of three long-term tillage experiments in Québec (Canada) and stored for 4.5 months prior to incubation. Urea (14 g N m−2) was applied at the soil surface and NH3 volatilization was measured for 30 d using an open incubation system. Mean cumulative NH3 losses were greater (P < 0.001) in NT (3.00 g N m−2) than in MP (0.52 g N m−2). Several factors may have contributed to the higher emissions from the NT soils. Urease activity in the top 1 cm of soils was on average 4.2 times higher in NT than in MP soils. As a result, hydrolysis of urea occurred very rapidly in NT soils as indicated by enhanced NH3 emissions 4 h after application of urea. The presence of crop residues at the surface of NT soils also decreased contact of the urea granules with the soil, possibly reducing adsorption of NH4+ on soil particles. Lower volatilization on the MP soils may also have partly resulted from a fraction of urea granules falling into shallow cracks. Field trials are needed to confirm our finding that NT soils bear greater potential for NH3 volatilization following surface application of urea than MP soils.  相似文献   

13.
Soil organic carbon (SOC) and nitrogen (N) are directly influenced by tillage, residue return and N fertilization management practices. Soil samples for SOC and N analyses, obtained from a 23-year field experiment, provided an assessment of near-equilibrium SOC and N conditions. Crops included corn (Zea mays L.) and soybean [Glycine max L. (Merrill)]. Treatments of conventional and conservation tillage, residue stover (returned or harvested) and two N fertilization rates were imposed on a Waukegan silt loam (fine-silty over skeletal, mixed, superactive, mesic Typic Hapludoll) at Rosemount, MN. The surface (0–20 cm) soils with no-tillage (NT) had greater than 30% more SOC and N than moldboard plow (MB) and chisel plow (CH) tillage treatments. The trend was reversed at 20–25 cm soil depths, where significantly more SOC and N were found in MB treatments (26 and 1.5 Mg SOC and N ha−1, respectively) than with NT (13 and 1.2 Mg SOC and N ha−1, respectively), possibly due to residues buried by inversion. The summation of soil SOC over depth to 50 cm did not vary among tillage treatments; N by summation was higher in NT than MB treatments. Returned residue plots generally stored more SOC and N than in plots where residue was harvested. Nitrogen fertilization generally did not influence SOC or N at most soil depths. These results have significant implications on how specific management practices maximize SOC storage and minimize potential N losses. Our results further suggest different sampling protocols may lead to different and confusing conclusions regarding the impact of tillage systems on C sequestration.  相似文献   

14.
Previous studies have demonstrated inconsistent results on the impact of tillage systems on nitrogen (N) losses from field-applied manure. This study assessed the impact of no-tillage (NT) and conventional tillage (CT) systems on gaseous N losses, N2O:N2O + N2 ratios and NO3−-N leaching following surface application of cattle manure. The study was undertaken during the 2003/2004 and 2004/2005 seasons at two field sites in Nova Scotia namely, Streets Ridge (SR) in Cumberland County and the Bio-environmental Engineering Centre (BEEC) in Truro. Results showed that the NT system had higher (p < 0.05) NH3 losses than CT. Over the two seasons, manure incorporation in CT reduced NH3 losses on average by 86% at SR and 78% at BEEC relative to NT. At both sites and during both seasons, denitrification rates and N2O fluxes in NT were generally higher than in CT plots, presumably due to higher soil water and organic matter content in NT. Over the two seasons, mean denitrification rates at SR were 239 and 119 g N ha−1 d−1, while N2O fluxes were 120 and 64 g N ha−1 d−1 under NT and CT, respectively. At BEEC mean denitrification rates were 114 and 71 g N ha−1 d−1, while N2O fluxes were 52 and 27 g N ha−1 d−1 under NT and CT, respectively. Conversely, N2O:N2O + N2 ratios were lower in NT than CT suggesting more complete reduction of N2O to N2 under NT. When averaged across all soil depths, NO3−-N was higher (p < 0.05) in CT than NT. Nitrate-N decreased with depth at both sites regardless of tillage. In most cases, NO3−-N was higher under CT than NT at all soil depths. Similarly, flow-weighted average NO3−-N concentrations in drainage water were generally higher under CT. This may be partly attributed to higher denitrification rates under NT. Therefore, NT may be a viable strategy to remove NO3−-N from the soil, and thus, reduce NO3−-N contamination of groundwater. However, it should be noted that while the use of NT reduces NO3−-N leaching it may come with unintended environmental tradeoffs, including increased NH3 and N2O emissions.  相似文献   

15.
Carbon sequestration in agroecosystems represents a significant opportunity to offset a portion of anthropogenic CO2 emissions. Climatic conditions in the Virginia coastal plain and modern production practices make it possible for high annual photosynthetic CO2 fixation. There is potential to sequester a substantial amount of C, and concomitantly improve soil quality, with the elimination of tillage for crop production in this region. The objectives of our research were to: (1) measure C sequestration rate with continuous no-till management of grain cropping systems of the Virginia middle coastal plain; (2) determine the influence of biosolids application history on C content and its interaction with tillage management; and (3) evaluate the impact of continuous no-till C stratification as an indicator of soil quality. Samples were collected from 63 sites in production fields using a rotation of corn (Zea mays L.)–wheat (Triticum aestivum L.) or barley (Hordeum vulgare L.)/soybean double-crop (Glysine max L.) across three soil series [Bojac (coarse-loamy, mixed, semiactive, thermic Typic Hapludults), Altavista (fine-loamy, mixed semiactive, thermic Aquic Hapludults), and Kempsville (fine-loamy, siliceous, subactive, thermic Typic Hapludults)] with a history of continuous no-till management ranging from 0 to 14 years. Thirty-two of the sites had a history of biosolids application. Five soil cores were collected at each site from 0–2.5, 2.5–7.5 and 7.5–15 cm and analyzed for bulk density and soil C. Bulk density in the 0–2.5 cm layer decreased and C stratification ratio (0–2.5 cm:7.5–15 cm) increased with increasing duration of continuous no-till due to the accumulation of organic matter at the soil surface. A history of biosolids application resulted in an increase of 4.19 ± 1.93 Mg C ha−1 (0–15 cm). Continuous no-till resulted in the sequestration of 0.308 ± 0.280 Mg C ha−1 yr−1 (0–15 cm). Our results provide quantitative validation of the C sequestration rate and improved soil quality with continuous no-till management in the region using on-farm observations.  相似文献   

16.
Integrated crop–livestock management systems (ICLS) have been increasingly recommended in Brazilian agroecosystems. However, knowledge of their effect on soil organic carbon (SOC) and total nitrogen (TN) concentrations and stocks is still limited. The study was undertaken to evaluate the effects of ICLS under two tillage and fertilization regimes on SOC and TN concentrations and stocks in the 0–30 cm soil layer, in comparison with continuous crops or pasture. The following soil management systems were studied: continuous pasture; continuous crop; 4 years’ crop followed by 4 years’ pasture and vice-versa. The adjacent native Cerrado area was used as a control. Under the rotation and continuous crop systems there were two levels of soil tillage (conventional and no-tillage) and fertility (maintenance and corrective fertility). The stock calculations were done using the equivalent soil mass approach. The land use systems had a significant effect on the concentrations of SOC and TN in the soil, but no effect was observed for the soil tillage and fertilizer regimes. For these two latter, some significant discrepancies appeared in the distribution of SOC and TN concentrations in the 0–30 cm layer. Carbon storage was 60.87 Mg ha−1 under Cerrado, and ranged from 52.21 Mg ha−1 under the ICLS rotation to 59.89 Mg ha−1 with continuous cropping. The decrease in SOC stocks was approximately 8.5 and 7.5 Mg ha−1, or 14 and 12%, for continuous pasture and ICLS respectively. No-tillage for 10 years after the conversion of conventional tillage to no-tillage under the continuous crop system, and 13 years of conventional tillage in continuous cropping did not result in significant changes in SOC stocks. The SOC and TN stocks in surface layers, using the equivalent soil mass approach rather than the equivalent depth, stress the differences induced by the calculation method. As soil compaction is the principal feature of variability of stocks determinations, the thickness should be avoid in these types of studies.  相似文献   

17.
Soil degradation associated with tillage is a major problem in Uruguayan agriculture. Either rotation of crops with pastures (ROT) or no-till (NT) cropping have been proposed as alternatives to minimize the impact of agriculture on soil quality. The combined impact on soil properties of ROT and NT has not been evaluated. In this study, we report results of the first 12 years of a long-term experiment established on a clay loam soil in western Uruguay. The objective was to determine the influence of conventional tillage (CT) and NT on systems under continuous cropping (CC, two crops per year) or ROT (3.5-year annual crops/2.5-year pastures). Soil samples taken at the beginning of the experiment in 1994 and in 2004 were analyzed for organic carbon (SOC), total organic carbon (TSOC) and total nitrogen content (STN), and for water-stable aggregation (WAS). Soil loss and erodibility indicators were studied using microrain simulator. With 12 years, the cumulative carbon (C) inputs of aboveground biomass were similar between tillage, but C input in CC was 50% higher than ROT. This difference was explained because 84% of the pastures dry matter was consumed by animals. Nevertheless we estimated a higher below ground biomass in ROT compared to CC systems (24.9 Mg ha−1 vs. 10.9 Mg ha−1). NT presented 7% higher SOC than CT (0–18 cm) with no differences between rotation systems. While all treatments declined in STN during 12 years, ROT had 11% and 58% higher STN and WAS than CC systems, with a large impact of the pasture under CT. Runoff and erosion were minimized under NT in both rotations systems. Thus, including pastures in the rotation, or switching from CT to NT improved soil quality properties. The expected benefit of combining NT and ROT will likely require more years for the cumulative effect to be detectable in both C input and soil properties.  相似文献   

18.
Rainfed crop yields are low in semiarid central Spain because precipitation is limited and highly variable. Under these circumstances, producers have to adopt alternative tillage systems that convey a reduction in their unit costs of production to offset the continuous decline in commodity prices. Farmers respond to this situation in essentially two ways: there is a growing interest in adopting reduced tillage systems for seedbed preparation, and a trend to enlarge enterprises by acquiring more arable land either as ownership or tenancy. The objective of the present study was to assess, in semiarid conditions of central Spain, the economic feasibility of chisel ploughing (CP) and no-tillage (NT) systems compared to mouldboard ploughing (MP) for rainfed winter wheat (Triticum aestivum L.) and forage legume, either vetch (Vicia sativa L.) or pea (Pisum sativum L.), production on different farm sizes ranging from 100 to 1600 ha. A decision support system was used to solve for the least-cost machinery selection for each farm enterprise and tillage system considered. No differences were observed in either wheat or forage vetch crop yields averaged across several years, irrespective of the tillage system used. The economic performance was found to depend on the tillage system adopted and farm size. On average fuel consumption was 23% lower in CP and 62% in NT than in MP. Total variable unitary costs were 3.7 and 5.6% lower in CP and NT than in MP. The cost of herbicides in NT was €7.6 ha−1 year−1 higher than in MP and CP. Average unitary gross margins were 11.9 and 10.8% higher in NT than in MP and CP, respectively. If revenues were considered similar in the three tillage systems, MP would still exhibit the poorest economic results in all farm sizes, while CP performance would improve NT values in farm sizes with 200 ha, or less, of arable land. NT was clearly the most profitable system on farms with 400 ha or more of arable land. The 400 ha farm enterprise was observed to mark the breakeven point between the two reduced tillage systems, since up to that size CP was found to provide a better economic performance than NT.  相似文献   

19.
The one-compartment C model Ct=C0e−k2t+k1A/k2(1−e−k2t) is being long used to simulate soil organic C (SOC) stocks. Ct is the SOC stock at the time t; C0, the initial SOC stock; k2, the annual rate of SOC loss (mainly mineralization and erosion); k1, the annual rate to which the added C is incorporated into SOC; and A, the annual C addition. The component C0e−k2t expresses the decay of C0 and, for a time t, corresponds to the remains of C0 (C0 remains). The component k1A/k2(1−e−k2t) refers, at time t, to the stock of SOC derived from C crops (Ccrop). We herein propose a simple method to estimate k1 and k2 coefficients for tillage systems conducted in long-term experiments under several cropping systems with a wide range of annual C additions (A) and SOC stocks. We estimated k1 and k2 for conventional tillage (CT) and no-till (NT), which has been conducted under three cropping systems (oat/maize −O/M, vetch/maize −V/M and oat + vetch/maize + cowpea −OV/MC) and two N-urea rates (0 kg N ha−1 −0 N and 180 kg N ha−1 −180 N) in a long-term experiment established in a subtropical Acrisol with C0 = 32.55 Mg C ha−1 in the 0–17.5 cm layer. A linear equation (Ct = a + bA) between the SOC stocks measured at the 13th year (0–17.5 cm) and the mean annual C additions was fitted for CT and NT. This equation is equivalent to the equation of the model Ct=C0e−k2t+k1A/k2(1−e−k2t), so that a=C0e−k2t and bA=k1A/k2(1−e−k2t). Such equivalences thus allow the calculation of k1 and k2. NT soil had a lower rate of C loss (k2 = 0.019 year−1) than CT soil (k2 = 0.040 year−1), while k1 was not affected by tillage (0.148 year−1 under CT and 0.146 year−1 under NT). Despite that only three treatments had lack of fit (LOFIT) value lower than the critical 5% F value, all treatments showed root mean square error (RMSE) lower than RMSE 95% indicating that simulated values fall within 95% confidence interval of the measurements. The estimated SOC stocks at steady state (Ce) in the 0–17.5 cm layer ranged from 15.65 Mg ha−1 in CT O/M 0 N to 60.17 Mg ha−1 in NT OV/MC 180 N. The SOC half-life (t1/2 = ln 2/k2) was 36 years in NT and 17 years in CT, reflecting the slower C turnover in NT. The effects of NT on the SOC stocks relates to the maintenance of the initial C stocks (higher C0 remais), while increments in Ccrop are imparted mainly by crop additions.  相似文献   

20.
Abstract

To assess their impacts on net global warming, total greenhouse gas emissions (mainly CO2, N2O and CH4) from agricultural production in arable land cropping systems in the Tokachi region of Hokkaido, Japan, were estimated using life cycle inventory (LCI) analysis. The LCI data included CO2 emissions from on-farm and off-farm fossil fuel consumption, soil CO2 emissions induced by the decomposition of soil organic matter, direct and indirect N2O emissions from arable lands and CH4 uptake by soils, which were then aggregated in CO2-equivalents. Under plow-based conventional tillage (CT) cropping systems for winter wheat, sugar beet, adzuki bean, potato and cabbage, on-farm CO2 emissions from fuel-consuming operations such as tractor-based field operations, truck transportation and mechanical grain drying ranged from 0.424 Mg CO2 ha?1 year?1 for adzuki bean to 0.826 Mg CO2 ha?1 year?1 for winter wheat. Off-farm CO2 emissions resulting from the use of agricultural materials such as chemical fertilizers, biocides (pesticides and herbicides) and agricultural machines were estimated by input–output tables to range from 0.800 Mg CO2 ha?1 year?1 for winter wheat to 1.724 Mg CO2 ha?1 year?1 for sugar beet. Direct N2O emissions previously measured in an Andosol field of this region showed a positive correlation with N fertilizer application rates. These emissions, expressed in CO2-equivalents, ranged from 0.041 Mg CO2 ha?1 year?1 for potato to 0.382 Mg CO2 ha?1 year?1 for cabbage. Indirect N2O emissions resulting from N leaching and surface runoff were estimated to range from 0.069 Mg CO2 ha?1 year?1 for adzuki bean to 0.381 Mg CO2 ha?1 year?1 for cabbage. The rates of CH4 removal from the atmosphere by soil uptake were equivalent to only 0.020–0.042 Mg CO2 ha?1 year?1. From the difference in the total soil C pools (0–20 cm depth) between 1981 and 2001, annual CO2 emissions from the CT and reduced tillage (RT) soils were estimated to be 4.91 and 3.81 Mg CO2 ha?1 year?1, respectively. In total, CO2-equivalent greenhouse gas emissions under CT cropping systems in the Tokachi region of Hokkaido amounted to 6.97, 7.62, 6.44, 6.64 and 7.49 Mg CO2 ha?1 year?1 for winter wheat, sugar beet, adzuki bean, potato and cabbage production, respectively. Overall, soil-derived CO2 emissions accounted for a large proportion (64–76%) of the total greenhouse gas emissions. This illustrates that soil management practices that enhance C sequestration in soil may be an effective means to mitigate large greenhouse gas emissions from arable land cropping systems such as those in the Tokachi region of northern Japan. Under RT cropping systems, plowing after harvesting was omitted, and total greenhouse gas emissions from winter wheat, sugar beet and adzuki bean could be reduced by 18%, 4% and 18%, respectively, mainly as a result of a lower soil organic matter decomposition rate in the RT soil and a saving on the fuels used for plowing.  相似文献   

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