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1.
Although the Midwestern United States is one of the world's major agricultural production areas, few studies have assessed the effects of the region's predominant tillage and rotation practices on greenhouse gas emissions from the soil surface. Our objectives were to (a) assess short-term chisel (CP) and moldboard plow (MP) effects on soil CO2 and CH4 fluxes relative to no-till (NT) and, (b) determine how tillage and rotation interactions affect seasonal gas emissions in continuous corn and corn–soybean rotations on a poorly drained Chalmers silty clay loam (Typic Endoaquoll) in Indiana. The field experiment itself began in 1975. Short-term gas emissions were measured immediately before, and at increasing hourly intervals following primary tillage in the fall of 2004, and after secondary tillage in the spring of 2005, for up to 168 h. To quantify treatment effects on seasonal emissions, gas fluxes were measured at weekly or biweekly intervals for up to 14 sampling dates in the growing season for corn. Both CO2 and CH4 emissions were significantly affected by tillage but not by rotation in the short-term following tillage, and by rotation during the growing season. Soil temperature and moisture conditions in the surface 10 cm were significantly related to CO2 emissions, although the proportion of variation explained by temperature and moisture was generally very low (never exceeded 27%) and varied with the tillage system being measured. In the short-term, CO2 emissions were significantly higher for CP than MP and NT. Similarly, mean seasonal CO2 emissions during the 2-year period were higher for CP (6.2 Mg CO2-C ha−1 year−1) than for MP (5.9 Mg CO2-C ha−1 year−1) and NT (5.7 Mg CO2-C ha−1 year−1). Both CP and MP resulted in low net CH4 uptake (7.6 and 2.4 kg CH4-C ha−1 year−1, respectively) while NT resulted in net emissions of 7.7 kg CH4-C ha−1 year−1. Mean emissions of CO2 were 16% higher from continuous corn than from rotation corn during the two growing seasons. After 3 decades of consistent tillage and crop rotation management for corn and soybean producing grain yields well above average in the Midwest, continuous NT production in the corn–soybean rotation was identified as the system with the least soil-derived C emissions to the atmosphere from among those evaluated prior to and during corn production.  相似文献   

2.
Evaluation of computer models with field data is required before they can be effectively used for predicting agricultural management systems. A study was conducted to evaluate tillage effects on the movement of water and nitrate–nitrogen (NO3–N) in the root zone under continuous corn (Zea mays L.) production. Four tillage treatments considered were: chisel plow (CP), moldboard plow (MP), no-tillage (NT), and ridge-tillage (RT). The root zone water quality model (RZWQM: V.3.25) was used to conduct these simulations. Three years (1990–1992) of field observed data on soil water contents and NO3–N concentrations in the soil profile were used to evaluate the performance of the model. The RZWQM usually predicted higher soil water contents compared with the observed soil water contents. The model predicted higher NO3–N concentrations in the soil profile for MP and NT treatments in comparison with CP and RT treatments, but the magnitude of simulated NO3–N peak concentrations in the soil profile were substantially different from those of the observed peaks. The average NO3–N concentrations for the entire soil profile predicted by the model were close to the observed concentrations except for ridge tillage (percent difference for CP=+5.1%, MP=+12.8%, NT=+18.4%, RT=−44.8%). Discrepancies between the simulated and observed water contents and NO3–N concentrations in the soil profile indicated a need for the calibration of plant growth component of the model further for different soil and climatic conditions to improve the N-uptake predictions of the RZWQM.  相似文献   

3.
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   

4.
No-tillage (NT) farming offers innumerable benefits to soil and water conservation, however, its potential to sequester soil organic carbon (SOC) and related soil properties varies widely. Thus, the impact of long-term (>4 yr) NT-based cropping systems on SOC sequestration and selected soil physical and chemical parameters were assessed across soils within five Major land Resource Areas (MLRAs: 99 and 111 in Michigan; 124 and 139 in Ohio; and 127 in Pennsylvania) in eastern U.S.A. Soil samples were collected from paired fields of NT and plow tillage (PT) based cropping systems and an adjacent woodlot (WL). The SOC concentration, bulk density (ρb), texture, pH, electrical conductivity (EC), soil N, coarse particulate organic matter (CPOM) C and N, and nitrate N (NO3-N) concentrations were determined. Conversion from NT to PT practice increased surface soil pH from 5.97, 6.56 and 6.02 to 6.62, 6.91 and 7.09 under MLRAs 127, 111 and 99, respectively. NT soils had higher SOC concentration soils by 30, 50 and 67% over PT soils at 0–5 cm depth under MLRAs 99, 111 and 127, respectively. Considering the whole soil profile SOC, WL had higher SOC pool than NT and PT practices under MLRAs 99, 111 and 124, however, there was no significant difference (P < 0.05) between NT and PT practices across five soils. Almost the same trend was observed in the case of depthwise soil N content. NT soil had higher N content than PT soils by 27, 44 and 54% under MLRAs 99, 127 and 111, respectively. However, whole soil profile N content of NT soil was significantly higher by 12% than PT soil under MLRA 99. Concentrations of CPOM associated C and N of NT soil was higher than PT soil under MLRAs 99, 111 and 127 at 0–5 soil depth. These results indicated that impact of tillage on soil C and associated soil quality parameters is confined within specific soil types.  相似文献   

5.
A wide range of tillage systems have been used by producers in the Corn-Belt in the United States during the past decade due to their economic and environmental benefits. However, changes in soil organic carbon (SOC) and nitrogen (SON) and crop responses to these tillage systems are not well documented in a corn–soybean rotation. Two experiments were conducted to evaluate the effects of different tillage systems on SOC and SON, residue C and N inputs, and corn and soybean yields across Iowa. The first experiment consisted of no-tillage (NT) and chisel plow (CP) treatments, established in 1994 in Clarion–Nicollet–Webster (CNW), Galva–Primghar–Sac (GPS), Kenyon–Floyd–Clyde (KFC), Marshall (M), and Otley–Mahaska–Taintor (OMT) soil associations. The second experiment consisted of NT, strip-tillage (ST), CP, deep rip (DR), and moldboard plow (MP) treatments, established in 1998 in the CNW soil association. Both corn and soybean yields of NT were statistically comparable to those of CP treatment for each soil association in a corn–soybean rotation during the 7 years of tillage practices. The NT, ST, CP, and DR treatments produced similar corn and soybean yields as MP treatment in a corn–soybean rotation during the 3 years of tillage implementation of the second experiment. Significant increases in SOC of 17.3, 19.5, 6.1, and 19.3% with NT over CP treatment were observed at the top 15-cm soil depth in CNW, KFC, M, and OMT soil associations, respectively, except for the GPS soil association in a corn–soybean rotation at the end of 7 years. The NT and ST resulted in significant increases in SOC of 14.7 and 11.4%, respectively, compared with MP treatment after 3 years. Changes in SON due to tillage were similar to those observed with SOC in both experiments. The increases in SOC and SON in NT treatment were not attributed to the vertical stratification of organic C and N in the soil profile or annual C and N inputs from crop residue, but most likely due to the decrease in soil organic matter mineralization in wet and cold soil conditions. It was concluded that NT and ST are superior to CP and MP in increasing SOC and SON in the top 15 cm in the short-term. The adoption of NT or CP can be an effective strategy in increasing SOC and SON in the Corn-Belt soils without significant adverse impact on corn and soybean yields in a corn–soybean rotation.  相似文献   

6.
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   

7.
Conservation management systems such as no tillage may enhance sequestration of soil C. The soil properties that contribute to soil C storage under such systems are still largely unknown, especially in subtropical agroecosystems. We investigated the influence of tillage [mouldboard plough (MP) and no tillage (NT)] on soil organic C, microbial biomass and activity, structural stability and mycorrhizal status of a field cultivated with maize (Zea mays L.) or bean (Phaseolus vulgaris L.) on a Vertisol in Northern Tamaulipas, Mexico. Crop type, tillage system and soil depth had a significant effect on soil organic C, aggregate stability and bulk density. Soil organic C, microbial biomass C and N and dehydrogenase and phosphatase activities were greater with NT than with MP, particularly under bean cultivation. In the 0–5 cm layer, microbial biomass C and N were, on average, about 87 and 51% greater in the soils cultivated with bean and maize, respectively, under NT than under MP. Higher levels of mycorrhizal propagules, glomalin related soil protein (GRSP) and stable aggregates were produced under NT than under MP in both crops. The no-tillage system can be considered an effective management practice for carrying out sustainable agriculture under subtropical conditions, due to its improvement of soil physical and biochemical quality and soil C sequestration.  相似文献   

8.
In Brazil, no tillage (NT) is a soil conservation practice now widely adopted by farmers, including smallholders. The effect of NT and conventional tillage (disc ploughing followed by two light disc harrowings, CT) was investigated on the aggregation properties of a clayey Rhodic Ferralsol from southern Brazil under different crop rotations. The same soil type under secondary forest was used as reference. Macro- and microaggregate classes were separated by wet sieving using a series of eight sieves (8, 4, 2, 1, 0.5, 0.25, 0.125, 0.053 mm) at four sampling layers (0–5, 5–10, 10–20, 20–30 cm). The soil in general had high structural stability. At 0–5 cm, meanweight diameter (MWD, 11.1 mm) and total organic C in macroaggregates (TOC, 39 g kg−1 soil) were highest for the forest soil. Soil under NT had a more similar distribution of aggregate size classes and TOC to the forest soil than CT. The most pronounced difference between tillage systems was observed in the surface soil layer (0–5 cm). In this layer, NT had higher aggregate stability (ASNT: 96%; ASCT: 89%), had higher values of aggregate size distribution (MWDNT: 7.9 mm, MWDCT: 4.3 mm), and had on average 28% greater TOC in all aggregate size classes than CT. Soil under NT had greater TOC in macroaggregates (NT: 22 g kg−1; CT: 13 g kg−1). Crop rotation did not have a significant effect on soil aggregate distribution and TOC. By increasing macroaggregation NT increased organic carbon accumulation in soil.  相似文献   

9.
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   

10.
Detailed information on the profile distributions of agronomically important soil properties in the planting season can be used as criteria to select the best soil tillage practices. Soil cores (0–60 cm) were collected in May, 2012 (before soybean planting), from soil transects on a 30‐yr tillage experiment, including no‐tillage (NT), ridge tillage (RT) and mouldboard plough (MP) on a Brookston clay loam soil (mesic Typic Argiaquoll). Soil cores were taken every 19 cm across three corn rows and these were used to investigate the lateral and vertical profile characteristics of soil organic carbon (SOC), pH, electrical conductivity (EC), soil volumetric water content (SWC), bulk density (BD), and penetration resistance (PR). Compared to NT and MP, the RT system resulted in greater spatial heterogeneity of soil properties across the transect. Average SOC concentrations in the top 10 cm layer were significantly greater in RT than in NT and MP (P = 0.05). NT soil contained between 0.8 and 2.5% (vol/vol) more water in the top 0–30 cm than RT and MP, respectively. MP soil had lower PR and BD in the plough layer compared to NT and RT soils, with both soil properties increasing sharply with depth in MP. The RT had lower PR relative to NT in the upper 35 cm of soil on the crop rows. Overall, RT was a superior conservation tillage option than NT in this clay loam soil; however, MP had the most favourable soil conditions in upper soil layers for early crop development across all treatments.  相似文献   

11.
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   

12.
The long-term effects of cropping systems and management practices on soil properties provide essential information for assessing sustainability and environmental impact. Field experiments were undertaken in southern Spain to evaluate the long-term effects of tillage, crop rotation and nitrogen (N) fertilization on the organic matter (OM) and mineral nitrogen (Nmin) contents of soil in a rain-fed Mediterranean agricultural system over a 6-year period. Tillage treatments included no tillage (NT) and conventional tillage (CT), crop rotations were of 2 yr with wheat (Triticum aestivum L.)-sunflower (Helianthus annuus L.) (WS), wheat-chickpea (Cicer arietinum L.) (WP), wheat-faba bean (Vicia faba L.) (WB), wheat-fallow (WF), and in addition, continuous wheat (CW). Nitrogen fertilizer rates were 50, 100, and 150 kg N ha−1. A split-split plot design with four replications was used. Soil samples were collected from a depth of 90 cm at the beginning of the experiment and 6 yr later. Soil samples were also collected from a depth of 30 cm after 4 yr. These samples, like those obtained at the beginning of the experiment, were subjected to comprehensive physico-chemical analyses. The soil samples that were collected 6 yr later were analyzed for OM, NH4+---N and NO3−---N at the 0–30, 30–60 and 60–90 cm soil depths. The tillage method did not influence the OM or Nmin contents of the soil, nor did legume rotations increase the OM content of soil relative to CW. A longer period may have been required for differences between treatments to be observed owing to the small amount of crop residue that is returned to soil under rain-fed conditions of semi-arid climates. The WF rotation did not raise the Nmin content of the soil relative to the other rotations. The consistent significant interaction between tillage and crop rotation testifies to the differential effect of the management system on the OM content and N status of the soil. The ammonium levels clearly exceeded those of NO3−---N throughout the soil profile. The high Nmin content of the soils reveals the presence of abundant N resources that should be borne in mind in establishing N fertilization schemes for crops under highly variable climatic conditions including scant rainfall such as those of the Mediterranean region.  相似文献   

13.
Tillage practices can potentially afect soil organic carbon (SOC) accumulation in agricultural soils. A 4-year experiment was conducted to identify the influence of tillage practices on SOC sequestration in a double-cropped rice (Oryza sativa L.) field in Hunan Province of China. Three tillage treatments, no-till (NT), conventional plow tillage(PT), and rotary tillage(RT), were laid in a randomized complete block design. Concentrations of SOC and bulk density(BD) of the 0-80 cm soil layer were measured, and SOC stocks of the 0-20 and 0-80 cm soil layers were calculated on an equivalent soil mass(ESM) basis and fixed depth (FD) basis.Soil carbon budget(SCB) under diferent tillage systems were assessed on the basis of emissions of methane(CH4) and CO2 and the amount of carbon (C) removed by the rice harvest. After four years of experiment, the NT treatment sequestrated more SOC than the other treatments. The SOC stocks in the 0-80 cm layer under NT (on an ESM basis) was as high as 129.32 Mg C ha 1,significantly higher than those under PT and RT (P < 0.05). The order of SOC stocks in the 0-80 cm soil layer was NT > PT > RT,and the same order was observed for SCB; however, in the 0-20 cm soil layer, the RT treatment had a higher SOC stock than the PT treatment. Therefore, when comparing SOC stocks, only considering the top 20 cm of soil would lead to an incomplete evaluation for the tillage-induced efects on SOC stocks and SOC sequestrated in the subsoil layers should also be taken into consideration. The estimation of SOC stocks using the ESM instead of FD method would better reflect the actual changes in SOC stocks in the paddy filed, as the FD method amplified the tillage efects on SOC stocks. This study also indicated that NT plus straw retention on the soil surface was a viable option to increase SOC stocks in paddy soils.  相似文献   

14.
Management practices including various tillage systems influence quantity and composition of soil organic matter (SOM). Parameters for evaluating both the SOM quantity (organic C [Cox], total N [Nt]) and quality (microbial biomass C, hydrophobic and hydrophilic organic components) were determined in soil samples, taken from two soil depths (0–0.1 m and 0.1–0.3 m) in a field experiment in the period 2001–2007, with different tillage systems. The experiment, founded in 1995 in Prague-Ruzyně, includes conventional soil tillage (CT) plus some selected methods of conservation tillage: (a) no tillage (NT), (b) no tillage + mulch (NTM), and (c) minimum tillage with pre-crop residues incorporated (MTS). Cox and microbial biomass C contents increased significantly with conservation tillage as compared to CT in 0–0.1 m layer, non-significant increase was found in 0.1–0.3 m layer. Nt increased non-significantly in both layers. Along with the depth of sampling, the content of the characterized parameters decreased in all variants; but the decrease in the conventionally tilled variant was, for the most part, lower than in the conservation tillage. The functional hydrophobic and hydrophilic groups of soil organic matter were identified by Fourier transform infrared (FTIR) spectroscopy, and the hydrophobic/hydrophilic group intensities ratio was calculated as the parameter of soil hydrophobicity. A higher soil hydrophobicity existed in all three conservation tillage treatments compared to CT due to the significantly higher content of hydrophobic organic components. Cox correlated significantly with microbial biomass C, Nt, hydrophobic components, and soil hydrophobicity (R = 0.552–0.654; P < 0.05). Hydrophilic components did not correlate with other soil characteristics, with the exception of hydrophobic components. These data show that shifting from CT to the conservation tillage systems increased the content of SOM in top soil layer in relatively short time, improved the SOM quality and increased soil hydrophobicity in the condition of experiment.  相似文献   

15.
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   

16.
Grazing of cover crops in grain cropping systems can increase economic return and diversify agricultural production systems, but the environmental consequences of this intensified management have not been well documented, especially under different tillage systems. We conducted a multiple-year investigation of how cover crop management (grazed and ungrazed) and tillage system [conventional (CT; initial moldboard plowing and thereafter disk tillage) and no tillage (NT)] affected soil physical properties (bulk density, aggregation, infiltration, and penetration resistance) on a Typic Kanhapludult in Georgia. Responses were determined in two cropping systems: summer grain/winter cover crop and winter grain/summer cover crop. Soil bulk density was reduced (P = 0.02) with CT compared with NT to a depth of 30 cm at the end of 0.5 year, but only to a depth of 12 cm at the end of 2, 2.5, and 4.5 years. Grazing of cover crops had little effect on soil bulk density, except eventually with 4.5 years of management. Water-stable macroaggregation was reduced (P ≤ 0.01) with CT compared with NT to a depth of 12 cm at all sampling times during the first 2.5 years of evaluation. Stability of macroaggregates in water was unaffected by grazing of cover crops in both tillage systems. Across 7 sampling events during the first 4 years, there was a tendency (P = 0.07) for water infiltration rate to be lower with grazing of cover crops (5.6 mm min−1) than when ungrazed (6.9 mm min−1), irrespective of tillage system. Across 10 sampling events, soil penetration resistance was greater under NT than under CT at a depth of 0–10 cm (P = 0.001) and the difference was greater in ungrazed than in grazed systems (P = 0.06). Biannual CT operations may have alleviated any surface degradation with animal traffic, but the initially high level of soil organic matter following long-term pasture and conversion to cropland with NT may have buffered the soil from any detrimental effects of animal traffic. Overall, the introduction of cattle to consume the high-quality cover crop forage did not cause substantial damage to the soil.  相似文献   

17.
Abstract

The objective of the project was to determine the effects of tillage on soil physical properties. A tillage project, involving three treatments with eight replications [no‐tillage (NT), chisel plowing (CP), and moldboard plowing (MP)], was initiated in the spring of 1989 in southern Illinois. The soil on which the work was conducted was a Grantsburg silt loam (fine‐silty, mixed, mesic Typic Fragiudalf), with a root‐restricting fragipan found at an average depth of 64 + 14 cm from the soil surface. Corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] were grown on the plot area on a yearly rotation. The soil physical properties evaluated were: penetration resistance; bulk density; aggregate stability; and pore size distribution by water‐release. Tillage effects on soil penetration resistance were mainly confined to the plow‐layer (i.e. top 23 cm of soil). Generally, the cone index (CI) values for the top 23 cm of soil for all treatments were below 2MPa, except at midseason in 1991, a dry year. Penetration resistance differences due to tillage treatments were not caused by differences in soil water content. Soil bulk density was generally highest for NT at planting, however, the bulk density for CP and MP increased later in the season attaining values comparable to those of NT treatment. Chiseling and moldboard plowing reduced soil aggregate stability. Soil temperature at planting was lower for no‐tillage compared to the moldboard plowed system. Effects of tillage on pore size distribution, for the first two years of the experiment, were significant only at planting. Total porosity was higher for MP than CP and NT in both years. At midseason, 1991, total porosity was lower with MP than with NT and CP. The improved NT crop performance relative to the CP and MP treatments could also be related to better seed bed and root bed conditions following soybean (third year) than sod (first year) and better weed control. Initial crop yield advantages of MP over the conservation tillage systems (NT and CP) deteriorated over time, resulting in decreased soil aggregation, total porosity and soil productivity.  相似文献   

18.
To investigate the consequences of long-term N additions on soil CH4 dynamics, we measured in situ CH4 uptake rates, soil profiles and kinetics parameters during the growing season in a temperate deciduous forest in northwestern Pennsylvania (Allegheny College Bousson Environmental Forest). Measurements were made in control and adjacent plots amended with 100 kg N ha–1 year–1 for 8 years. We found that the in situ consumption rates were 0.19±0.02 (mean±SE) for the control and 0.12±0.01 mg CH4–C m–2 h–1 for the N treatment, indicating that consumption had been reduced by 35% after 8 years of N amendments. Despite the large difference in rates of consumption, there were no differences in the CH4 concentration profiles between the control and N-amended plots. Laboratory incubations of CH4 consumption throughout the soil column (organic horizon and mineral soil depths) showed that rates were greatest in the organic horizon of both control and N-amended soils, although consumption was reduced by 42% in the N-amended plot. However, the rate in the organic horizon was only about 50% the rate measured in organic horizons at other temperate forests. The apparent Km [Km(app)] value in the organic horizon of the control plot was fourfold less than the Km(app) value in the organic horizon of another temperate forest, but similar to the Km(app) values in adjacent plots amended with N for a decade. Unlike results for other temperate forests, Km(app) values at Bousson generally did not decrease with soil depth. These results indicate that N cycling strongly controls the CH4-consuming community, and suggest that alterations of the N cycle due to N deposition or addition may alter rates and the location of CH4 consumption by soils, even in soils with high N content and cycling rates.  相似文献   

19.
Drainage, tillage, and intensive land use lead to drastic alterations in physical characteristics of organic soils. As decomposition and soil formation progress, bulk density (ρb) increases and total porosity (ft) decreases due to subsidence, shrinkage, and mineralization of soil organic matter (SOM). However, the rate of subsidence and the changes in soil properties differ among management systems. Thus, the objectives of this study were to determine the effects of different tillage practices on ρb and ft of cultivated peat soils. These experiments were conducted during 2004–2005, on Histosols in north central Ohio. Soil core samples were obtained from experimental plots managed with moldboard plow (MB), no-till (NT), or left bare (B). Conversion of plow tillage to NT increased ρb from 0.52 to 0.57 Mg m−3, and decreased ft from 0.72 to 0.70 m3 m−3.  相似文献   

20.
Laboratory incubation experiments were conducted to study the effects of soil chemical and physical properties on CH4 emission and entrapment in 16 selected soils with a pH range of 4.7–8.1, organic matter content of 0.72–2.38%, and soil texture from silt to clay. There was no significant correlation with CH4 emission for most of the important soil properties, including soil aerobic pH (measured before anaerobic incubation), total Kjeldahl N, cation exchange capacity, especially soil organic matter, and soil water-soluble C, which were considered to be critical controlling factors of CH4 emission. A lower CH4 emission was observed in some soils with a higher organic matter content. Differences in soil Fe and Mn contents and their chemical forms contributed to the this observation. A significant correlation between the CH4 emission and the soil organic C content was observed only after stratifying soils into subgroups according to the level of CH4 emission in soils not amended with organic matter. The results also showed that the soil redox potential (Eh), anaerobic pH, anerobic pH, and biologically reducible Fe and Mn affected CH4 emission significantly. Urea fertilization promoted CH4 emission in some soils and inhibited it in others. This result appeared to be related to the original soil pH. CH4 entrapment was positively correlated with soil clay content, indicating the importance of soil physical characteristics in reducing CH4 emissions to the atmosphere.  相似文献   

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