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1.
Soil C and N contents play a crucial role in sustaining soil quality and environmental quality. The conversion of annually cultivated land to forage grasses has potential to increase C and N sequestration. The objective of this study was to investigate the short-term changes in soil organic C (SOC) and N pools after annual crops were converted to alfalfa (Medicago sativa L. Algonguin) forage for 4 years. Soil from 24 sets of paired sites, alfalfa field versus adjacent cropland, were sampled at depths of 0–5, 5–10 and 10–20 cm. Total soil organic C and N, particulate organic matter (POM) C and N were determined. Organic C, total N, POM-C, and POM-N contents in the 0–5 cm layer were significantly greater in alfalfa field than in adjacent cropland. However, when the entire 0–20 cm layer was considered, there were significant differences in SOC, POM-C and POM-N but not in total N between alfalfa and crop soils. Also, greater differences in POM-C and POM-N were between the two land-use treatments than in SOC and total N were found. Across all sites, SOC and total N in the 0–20 cm profile averaged 22.1 Mg C ha−1 and 2.3 Mg N ha−1 for alfalfa soils, and 19.8 Mg C ha−1and 2.2 Mg N ha−1 for adjacent crop soils. Estimated C sequestration rate (0–20 cm) following crops to alfalfa conversions averaged 0.57 Mg C ha−1 year−1. Sandy soils have more significant C accumulation than silt loam soils after conversion. The result of this suggests that the soils studied have great C sequestration potential, and the conversion of crops to alfalfa should be widely used to sequester C and improve soil quality in this region.  相似文献   

2.
Soil organic carbon (SOC) has an important role in improving soil quality and sustainable production. A long-term fertilization study was conducted to investigate changes in SOC and its relation to soil physical properties in a rice paddy soil. The paddy soils analyzed were subjected to different fertilization practices: continuous application of inorganic fertilizers (NPK, N–P–K = 120–34.9–66.7 kg ha−1 yr−1 during 1967–1972 and 150–43.7–83.3 kg ha−1 yr−1 from 1973 to 2007), straw based compost (Compost, 10 Mg ha−1 yr−1), a combination of NPK + Compost, and no fertilization (control). Soil physical properties were investigated at rice harvesting stage in the 41st year for analyzing the relationship with SOC fraction. Continuous compost application increased the total SOC concentration in plough layers and improved soil physical properties. In contrast, inorganic or no fertilization markedly decreased SOC concentration resulting to a deterioration of soil physical health. Most of the SOC was the organo-mineral fraction (<0.053 mm size), accounting for over 70% of total SOC. Macro-aggregate SOC fraction (2–0.25 mm size), which is used as an indicator of soil quality rather than total SOC, covered 8–17% of total SOC. These two SOC fractions accumulated with the same tendency as the total SOC changes. Comparatively, micro-aggregate SOC (0.25–0.053 mm size), which has high correlation with physical properties, significantly decreased with time, irrespective of the inorganic fertilizers or compost application, but the mechanism of decrease is not clear. Conclusively, compost increased total SOC content and effective SOC fraction, thereby improving soil physical properties and sustaining production.  相似文献   

3.
A field experiment was conducted for two crop cycles during 2003–2005 and 2004–2006 at the Indian Institute of Sugarcane Research, Lucknow in subtropical India. Trichoderma viride and Gluconacetobacter diazotrophicus amended farm yard manure (FYM) increased organic carbon (19.44 Mg ha−1) and available nitrogen (260 kg N ha−1) content of soil from 14.78 Mg ha−1 (OC) and 204 kg N ha−1 observed under farmer's practice (sole N application). Application of bioagents amended FYM improved soil porosity and reduced compaction (bulk density—1.39 Mg m−3 over 1.48 Mg m−3 under farmer's practice). Sugarcane ratoon crop removed the highest amount of nitrogen (N—165.7 kg ha−1), phosphorus (P—24.01 kg ha−1) and potassium (K—200.5 kg ha−1) in the plots receiving FYM with Trichoderma and Gluconacetobacter. Inoculation of FYM with bioagents improved population of ammonifying and nitrifying bacteria in the soil. Phosphorus and potassium uptake of the crop was greatest in the plots receiving FYM, Trichoderma and Gluconacetobacter. Bioagents (Trichoderma and Gluconacetobacter) amended FYM increased ratoon cane (70.2 Mg ha−1) and sugar yields (7.93 Mg ha−1) compared with control (62.3 and 7.06 Mg ha−1 ratoon cane and sugar yields, respectively).  相似文献   

4.
To explore long-term impact of organic and inorganic fertilizers on soil health and grain quality, we monitored the enzyme activities and chemical properties of soil; and chemical composition of grain from eight treatments at an experimental field site established in 1996. There were eight treatments applied to both wheat and maize seasons: a control; four inorganic fertilizers, that is, nitrogen and phosphorus (NP), nitrogen and potassium (NK), phosphorous and potassium (PK) and nitrogen, phosphorus and potassium (NPK); farm yard manure alone (FYM) and addition of FYM at two different doses (100 and 50% of recommendation) to NPK that is, NPK + FYM and ½ NPK + FYM. After 11 years of the experiment the NPK + FYM and ½ NPK + FYM treatments had the highest yields, about 5 Mg maize ha−1 and 2 Mg wheat ha−1 with about 2 and 0.5 Mg ha−1, respectively more than the NPK treatments. The dehydrogeanse activity of soils increased significantly in FYM and ½ NPK + FYM. Except urease all other enzymatic activities were increased in those treatments, which received manure. Urease activity was higher in mineral-N applied plots. Grain protein content of both maize and wheat was highest in mineral fertilized plots. Test weight also increased significantly on application of mineral fertilizer. Plots treated with half dose of recommended mineral fertilizer along with FYM were higher in urease, phosphomono and diesterase activities than that of NPK + FYM treated plots. Long-term application of inorganic nutrients along with FYM improved grain mineral composition and yield. Inhibition of few enzymatic activities were also observed upon application of inorganic nutrients either alone or in combination.  相似文献   

5.
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   

6.
Changes in residue management and incorporation of organic manures may help in carbon sequestration, restoring soil organic carbon (SOC) and sustaining the productivity of land under a cropping system. An experiment of multi-ratooning sugarcane (Saccharum officinarum L.) was initiated in 2003 in Inceptisols of Indian subtropics, to assess the effect of different organic manures and chemical fertilizer, on the crop productivity and soil quality. The annual sugarcane shoot biomass production in organic manure treatments was at par with the chemically fertilized treatment. Gross input of carbon (GIC) by the sugarcane crop was estimated to be 11.7–12.4 t ha−1 y−1 in different organic manure treatments compared to 8.4 and 5.0 t ha−1 y−1 in NPK and control treatments, respectively. The respiratory loss of C (RLC) increased linearly with increasing input of C in soil and it ranged from 3.3 to 4.1 t ha−1 y−1 in different treatments with maximum in FYM and minimum in control treatment. The sugarcane biomass added in the soil humified at a rate constant of 0.38 in sub-tropical conditions and an addition of 3.9 t C ha−1 y−1 is required to maintain SOC in equilibrium. After 5 years of sugarcane cropping (one plant + four ratoons) an increase of 2.3–17.1 t ha−1 in SOC over initial content was recorded with different treatments. Results in coming years from this long-term experiment shall add to the present calculated relationships between carbon addition and storage in sugarcane multi-ratooning crop production system under sub-tropical condition of India.  相似文献   

7.
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   

8.
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   

9.
Understanding the store and storage potential of carbon (C) and nitrogen (N) helps us understand how ecosystems would respond to natural and anthropogenic disturbances under different management strategies. We investigated organic C and N storage in aboveground biomass, litter, roots, and soil organic matter (SOM) in eight sites that were floristically and topographically similar, but which had been subjected to different intensities of disturbance by grazing animals. The primary objective of this study was to ascertain the impact of grazing exclusion (GE) on the store and storage potential of C and N in the Leymus chinensis Tzvel. grasslands of northern China. The results revealed that the total C storage (including that stored in aboveground biomass, litter, roots, and SOM, i.e. top 100-cm soil layer) was significantly different among the eight grasslands and varied from 7.0 kg C m−2 to 15.8 kg C m−2, meanwhile, the total N storage varied from 0.6 kg N m−2 to 1.5 kg N m−2. The soil C storage decreased substantially with grassland degradation due to long-term heavy grazing. 90% C and 95% N stored in grasslands were observed in the SOM, and they were minor in other pools. The limit range of C and N storage observed in these grassland soils suggests that GE may be a valuable mechanism of sequestering C in the top meter of the soil profile.  相似文献   

10.
Silvopastoral systems have great potential for storing carbon because of carbon assimilation in tree woody biomass, carbon input through litterfall and below-ground carbon turnover. In this study, we quantified and compared the carbon stocks at livestock ranches in Tabasco, Mexico, containing either scattered trees in grazing pastures (STP) or grass monocultures. Sampling plots were randomly established at each ranch where the above- and below-ground carbon stocks, carbon input from litterfall, grass production and arboreal biomass growth were measured. We found that silvopastoral systems stored an average of 257.45 Mg ha−1 of soil organic carbon (SOC) compared to 119.17 Mg SOC ha−1 at grass monoculture ranches (to 30 cm depth); silvopastoral systems also stored 44.64 Mg C ha−1 in wood biomass; and, grass monocultures had greater cumulative grass biomass production. Overall, it is concluded that livestock ranches in Tabasco, Mexico, with scattered trees in grazing pastures stored 58.8% more carbon than those grass monocultures, with carbon stocks of 327.01 Mg C ha−1and 134.47 Mg C ha−1, respectively. The results are useful for land management decision making for sustainable livestock systems framed in the Sustainable Development Goals (SDGs).  相似文献   

11.
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   

12.
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   

13.
Distillery effluent, a foul smelling, dark coloured by-product of distillery industries, is usually applied as irrigation water or as an amendment to arable land in some areas which are in the vicinity of the distillery industries. A field experiment on soybean–wheat system was conducted for 3 consecutive years in a Vertisol of central India to evaluate the effect of distillery effluent (DE) as an amendment on soil properties and crop productivity. The treatments were control (no fertilizer or manure or DE, T1), 100% NPK + FYM @ 4 Mg ha−1 to soybean (T2) and four graded levels of DE, viz.: 2.5 cm DE to soybean and wheat on residual nutrition (T3), 2.5 cm DE to soybean and 1.25 cm to wheat (T4), 5 cm DE to soybean and wheat on residual nutrition (T5), 5 cm DE to soybean and 2.5 cm to wheat (T6). The organic carbon, microbial biomass carbon and electrical conductivity (EC) of the surface (0–10 cm) soil increased significantly with application of DE compared to T1 and T2, but the soil pH was not affected. The EC increased from 0.47 dS m−1 and 0.58 dS m−1, respectively, in T1 and T2 to 1.52 dS m−1 in T6, where highest dose of DE was applied. This indicated a slight build-up of salinity with DE application. The application of DE showed a significant improvement in the physical properties of the soil. The mean weight diameter (MWD), saturated hydraulic conductivity, water retention at field capacity and available water content were significantly (P < 0.05) higher, while bulk density (BD) and penetration resistance of the surface soil were significantly lower (P < 0.05) in all DE treated plots except in T3 than those in T1 and T2. The fractions of WSA of more than 1 mm diameter in T6, T5 and T4 were, respectively, 141%, 107% and 116% more than the control. The MWD showed a positive linear relationship with the organic carbon (r = 0.84**) and microbial biomass carbon (r = 0.90**) of the soil. A significant (P < 0.01) negative linear relationship (r = 0.70**) was found between soil organic carbon and BD. Except T3, all the DE treated plots recorded significantly higher total and microporosity of the soil than control. Water retention at permanent wilting point and macroporosity of the soil were not affected by treatment. The seed yield of soybean in all the DE treatments was similar with T2 (1.86 Mg ha−1) but significantly more than control (1.28 Mg ha−1). The DE application levels have not affected the seed yield of soybean. In wheat highest grain yield was recorded in T2 (3.47 Mg ha−1), which was similar with T4 (3.16 Mg ha−1), T5 (3.22 Mg ha−1) and T6 (3.46 Mg ha−1). DE application up to T4 level was found suitable from productivity, salinity and sustainability point of view. The study showed that judicious application of DE as an amendment to the agricultural field could be considered as a viable option for safe disposal of this industrial waste.  相似文献   

14.
High population pressure in the central highlands of Kenya has led to continuous cultivation of land with minimal additional inputs leading to soil nutrient depletion. Research work has reported positive results from use of manure and biomass from Tithonia, Calliandra, Leucaena, Mucuna and Crotolaria for soil fertility replenishment. An experimental field was set up in Chuka Division to test different soil nutrient replenishment treatments. The experimental design was randomised complete block with 14 treatments replicated three times. At the beginning and end of the experiment, soil was sampled at 0–15 cm depth and analysed for pH, Ca, Mg, K, C, N and P. End of the 2000/2001 short rains (SR) season and 2001 long rains (LR) season, soil samples were taken at 0–30, 30–100 and 100–150 cm for nitrate and ammonium analysis. All the treatments received an equivalent of 60 kg N ha−1, except herbaceous legume treatments, where N was determined by the amount of the biomass harvested and incorporated in soil and control treatment received no inputs. Results indicate soil fertility increased slightly in all treatments (except control) over the 2-year study period. Average maize grain yield across the treatments was 1.1, 5.4, 3.5 and 4.0 Mg ha−1 during the 2000 LR, 2000/2001 SR, 2001 LR and 2001/2002 SR, respectively. The reduced yield in 2000 LR and 2001 LR are attributed to poor rainfall distribution during the two seasons. On average, Tithonia with half recommended rate of inorganic fertilizer recorded the highest (4.8 Mg ha−1) maize yield followed by sole Tithonia (4.7 Mg ha−1). Highest average concentration (144.8 and 115.5 kg N ha−1) of mineral N was recorded at the 30–100 cm soil depth at the end of both 2000/2001 SR and LR, respectively. The lowest average concentration (67.1 kg N ha−1) was recorded in the 100–150 cm soil depth in both seasons, while during the 2001 LR, the 0–30 cm soil depth recorded the lowest concentration (52.3 kg N ha−1). The residual mineral N in the 100–150 cm soil depth doubled at the end of the LR 2001 compared to what was present and the end of the SR 2000/2001 season in all treatments. This shows that there is substantial amount of mineral N that is being leached below the rooting zone of maize in this region.  相似文献   

15.
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   

16.
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   

17.
Evaluation of carbon dynamics is of great concern worldwide in terms of climate change and soil fertility. However, the annual CO2 flux and the effect of land management on the carbon budget are poorly understood in Sub-Saharan Africa, owing to the relative dearth of data for in situ CO2 fluxes. Here, we evaluated seasonal variations in CO2 efflux rate with hourly climate data in two dry tropical croplands in Tanzania at two sites with contrasting soil textures, viz. clayey or sandy, over four consecutive crop-cultivation periods of 40 months. We then: (1) estimated the annual CO2 flux, and (2) evaluated the effect of land management (control plot, plant residue treatment plot, fertilizer treatment plot, and plant residue and fertilizer treatment plot) on the CO2 flux and soil carbon stock at both sites. Estimated annual CO2 fluxes were 1.0–2.2 and 0.9–1.9 Mg C ha?1 yr?1 for the clayey and sandy sites, respectively. At the end of the experiment, crop cultivation had decreased the surface soil carbon stocks by 2.4 and 3.0 Mg C ha?1 (soil depth 0–15 cm) at the clayey and sandy sites, respectively. On the other hand, plant residue application (7.5 Mg C ha?1 yr?1) significantly increased the surface soil carbon stocks, i.e., 3.5–3.8 and 1.7–2.1 Mg C ha?1 (soil depth 0–15 cm) at the clayey and sandy sites, respectively, while it also increased the annual CO2 fluxes substantially, i.e., 2.5–4.0 and 2.4–3.4 Mg C ha?1 yr?1 for the clayey and sandy soils, respectively. Our results indicate that these dry tropical croplands at least may act as a carbon sink, though the efficiency of carbon accumulation was substantially lower in sandy soil (6.8–8.4%) compared to clayey soil (14.0–15.2%), possibly owing to higher carbon loss by leaching and macro-faunal activity.  相似文献   

18.
Information on N cycling in dryland crops and soils as influenced by long-term tillage and cropping sequence is needed to quantify soil N sequestration, mineralization, and N balance to reduce N fertilization rate and N losses through soil processes. The 21-yr effects of the combinations of tillage and cropping sequences was evaluated on dryland crop grain and biomass (stems + leaves) N, soil surface residue N, soil N fractions, and N balance at the 0–20 cm depth in Dooley sandy loam (fine-loamy, mixed, frigid, Typic Argiboroll) in eastern Montana, USA. Treatments were no-tilled continuous spring wheat (Triticum aestivum L.) (NTCW), spring-tilled continuous spring wheat (STCW), fall- and spring-tilled continuous spring wheat (FSTCW), fall- and spring-tilled spring wheat–barley (Hordeum vulgare L.) (1984–1999) followed by spring wheat–pea (Pisum sativum L.) (2000–2004) (FSTW-B/P), and spring-tilled spring wheat–fallow (STW-F). Nitrogen fractions were soil total N (STN), particulate organic N (PON), microbial biomass N (MBN), potential N mineralization (PNM), NH4-N, and NO3-N. Annualized crop grain and biomass N varied with treatments and years and mean grain and biomass N from 1984 to 2004 were 14.3–21.2 kg N ha−1 greater in NTCW, STCW, FSTCW, and FSTW-B/P than in STW-F. Soil surface residue N was 9.1–15.2 kg N ha−1 greater in other treatments than in STW-F in 2004. The STN at 0–20 cm was 0.39–0.96 Mg N ha−1, PON 0.10–0.30 Mg N ha−1, and PNM 4.6–9.4 kg N ha−1 greater in other treatments than in STW-F. At 0–5 cm, STN, PON, and MBN were greater in STCW than in FSTW-B/P and STW-F. At 5–20 cm, STN and PON were greater in NTCW and STCW than in STW-F, PNM and MBN were greater in STCW than in NTCW and STW-F, and NO3-N was greater in FSTW-B/P than in NTCW and FSTCW. Estimated N loss through leaching, volatilization, or denitrification at 0–20 cm depth increased with increasing tillage frequency or greater with fallow than with continuous cropping and ranged from 9 kg N ha−1 yr−1 in NTCW to 46 kg N ha−1 yr−1 in STW-F. Long-term no-till or spring till with continuous cropping increased dryland crop grain and biomass N, soil surface residue N, N storage, and potential N mineralization, and reduced N loss compared with the conventional system, such as STW-F, at the surface 20 cm layer. Greater tillage frequency, followed by pea inclusion in the last 5 out of 21 yr in FSTW-B/P, however, increased N availability at the subsurface layer in 2004.  相似文献   

19.
We assessed the successional development of above- and belowground ecosystem biomass and carbon (C) pools in an age-sequence of four White pine (Pinus strobus L.) plantation stands (2-, 15-, 30-, and 65-years-old) in Southern Ontario, Canada. Biomass and C stocks of above- and belowground live and dead tree biomass, understorey and forest ground vegetation, forest floor C (LFH-layer), and woody debris were determined from plot-level inventories and destructive tree sampling. Small root biomass (<5 mm) and mineral soil C stocks were estimated from soil cores. Aboveground tree biomass became the major ecosystem C pool with increasing age, reaching 0.5, 66, 92, and 176 t ha−1 in the 2-, 15-, 30-, and 65-year-old stands, respectively. Tree root biomass increased from 0.1 to 10, 18, 38 t ha−1 in the 2-, 15-, 30-, and 65-year-old stands, respectively, contributing considerably to the total ecosystem C in the three older stands. Forest floor C was 0.8, 7.5, 5.4, and 12.1 t C ha−1 in the 2-, 15-, 30-, and 65-year-old stands, respectively, indicating an increase during the first two decades, but no further age-effect during the later growth phase. Mineral soil C was age-independent with 37.2, 33.9, 39.1, and 36.7 t C ha−1 in the 2-, 15-, 30-, and 65-year-old stands, respectively. Aboveground ecosystem C increased with age from 3 to 40, 52, and 100 t C ha−1 in the 2-, 15-, 30-, and 65-year-old stands, respectively, due to an increase in aboveground tree biomass. Belowground ecosystem C remained similiar in the early decades after establishment with 37, 39, and 39 t C ha−1 in the 2-, 15-, and 30-year-old stands, but increased to 56 t C ha−1 in the 65-year-old stand due to an increase in root biomass. The difference in total ecosystem C between the 2- and 65-year-old stand was 116 t C ha−1. Our results highlight the importance of considering the successional development of forest ecosystem C pools, when estimating C sink potentials over their complete life cycle.  相似文献   

20.
Soil water and nutrients play an important role in increasing sorghum (Sorghum bicolor L. Moench) yields in the Vertisols of semi-arid tropics during post-rainy season. The effects of tillage practices, organic materials and nitrogen fertilizer on soil properties, water conservation and yield of sorghum were evaluated during winter seasons of 1994–1995 and 1995–1996 on deep Vertisols at Bijapur in the semi-arid tropics of Karnataka State (Zone 3) of south India. Conservation and availability of water and nutrients during different stages of crop growth were increased by deeper tillage resulting in increased grain yield of winter sorghum. Medium and deep tillage increased the grain yield by 23% (1509 kg ha−1) and 57% (1919 kg ha−1) during 1994–1995 and 14% (1562 kg ha−1) and 34% (1835 kg ha−1) during 1995–1996, respectively, over shallow tillage. Water use efficiency increased from shallow (4.90 kg ha−1 mm−1) to deep tillage (7.30 kg ha−1 mm−1). Greater water use efficiency during 1994–1995 as compared to 1995–1996 was attributed to lower consumptive use of water during 1994–1995. Among organic materials, application of Leucaena loppings conserved larger amounts of water and increased winter sorghum yield and water use efficiency. Application of Leucaena loppings increased the winter sorghum grain yield by 9% (mean of 1994–1995 and 1995–1996) as compared to vermicompost. Significantly (P < 0.05) higher water use efficiency of 6.32 kg ha−1 mm−1 was observed in Leucaena loppings incorporated plots compared to 5.72 kg ha−1 mm−1 from vermicompost. Grain yield increased by 245 kg ha−1 with application of 25 kg N ha−1 in 1994–1995, and a further increase in N application to 50 kg ha−1 increased the grain yield by about 349 kg ha−1 in 1995–1996. Deep tillage with application of 25 kg N ha−1 resulted in significantly higher sorghum yield (2047 kg ha−1) than control during 1994–1995. Deep tillage with integrated nutrient management (organic and inorganic N sources) conserved higher amount of soil water and resulted in increased sorghum yields especially during drought years.  相似文献   

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