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1.
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   

2.
This study aimed at investigating the effects of agricultural exploitation on desert soil organic C, N and P, and soil aggregation. Four land uses were assessed: (1) 5-year wheat (Triticum aestivum L.)/barley (Hordeum vulgare L.) + 5-year maize (Zea mays L.); (2) 5-year wheat/barley + 5-year alfalfa (Medicago sativa L.); (3) 6-year wheat/barley + 4-year acacia (Robinia pseudoacacia L.) and (4) uncultivated desert soil. The desert soil contained total organic C (TOC) of 3.1, 3.7 and 4.2 g kg−1 and particulate organic C (POC) of 0.6, 0.7 and 0.8 g kg−1 at 0–10, 10–20 and 20–30 cm depths, respectively. The soil TOC concentration was increased by 32–68% under wheat–maize rotation and by 27–136% under wheat–acacia at 0–20 cm depth, and by 48% under wheat–alfalfa only at 0–10 cm depth. This contrasted with an increase in the soil POC concentration by 143–167% at depth 0–20 cm under wheat–maize and by 217%, 550% at depth 0–10 cm under wheat–alfalfa and wheat–acacia, respectively. The desert soil had 13 Mg ha−1 TOC stock and 2 Mg ha−1 POC stock at depth 0–30 cm, whereas crop rotations increased the soil TOC stock by 30–65% and POC stock by 200–350%. Over the 10-year period, the rates of TOC accumulation were 0.6, 0.3, 0.8 Mg ha−1 year−1 and the rates of POC accumulation were 0.4, 0.4 and 0.7 Mg ha−1 year−1 under wheat–maize, wheat–alfalfa and wheat–acacia rotations, respectively. At 0–30 cm depth, total soil N was increased by 61–64% under wheat–maize and wheat–acacia, but total soil P was reduced by 38% under wheat–alfalfa. A significant improvement in clay stability but not in aggregate water-stability was observed in cultivated soils. The results showed a significant increase in soil organic C pool but unimproved macro-aggregation of the desert soil after 10 years of cultivation.  相似文献   

3.
Field experiments were conducted at Fort Vermilion (58°23′N 116°02′W), Alberta, to determine phosphorus (P) release patterns from red clover (Trifolium pratense) green manure (GM), field pea (Pisum sativum), canola (Brassica rapa) and monoculture wheat (Triticum aestivum) residues in the 7th and 8th years of conventional and zero tillage. Phosphorus contained in crop residues ranged from 1.5 kg ha−1 in pea to 9.2 kg ha−1 in clover GM, both under zero tillage. The patterns of P release over a 52-week period sometimes varied with tillage, i.e., a greater percentage of GM residue P was released under conventional tillage than under zero tillage in the first 2–10 weeks of residue placement. Wheat residues resulted in net P immobilization under zero tillage, but the amounts immobilized were less than 1 kg ha−1. When net P mineralization occurred, the percentage of P released ranged from 24% of wheat P under conventional tillage to 74% of GM P under conventional tillage. The amounts of P released were 0.4 kg ha−1 from wheat, 0.8 kg ha−1 from canola, 0.4 kg ha−1 from pea and 5.1–5.6 kg ha−1 from clover GM residues. Therefore, only GM residues recycled agronomically significant amounts of P for use by subsequent crops in rotation. Phosphorus release was positively correlated with residue P concentration and negatively correlated with C/P and lignin/P ratios.  相似文献   

4.
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   

5.
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   

6.
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   

7.
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   

8.
Cover crop and tillage effects on soil enzyme activities following tomato   总被引：2，自引：0，他引：2  
Increasing numbers of vegetable growers are adopting conservation tillage practices and including cover crops into crop rotations. The practice helps to increase or maintain an adequate level of soil organic matter and improves vegetable yields. The effects of the practices, however, on enzyme activities in southeastern soils of the United States have not been well documented. Thus, the objectives of the study were to investigate the effects of cover crops and two tillage systems on soil enzyme activity profiles following tomato and to establish relationships between enzyme activities and soil organic carbon (C) and nitrogen (N). The cover crops planted late in fall 2005 included black oat (Avena strigosa), crimson clover (Trifolium incarnatum L.), or crimson clover–black oat mixed. A weed control (no cover crop) was also included. Early in spring 2006, the plots were disk plowed and incorporated into soil (conventional tillage) or mowed and left on the soil surface (no-till). Broiler litter as source of N fertilizer was applied at a rate of 4.6 Mg ha−1, triple super phosphate at 79.0 kg P ha−1, and potassium chloride at 100 kg K ha−1 were also applied according to soil testing recommendations. Tomato seedlings were transplanted and grown for 60 days on a Marvyn sandy loam soil (fine-loamy, kaolinitic, thermic Typic Kanhapludults). Ninety-six core soil samples were collected at incremental depths (0–5, 5–10, and 10–15 cm) and passed through a 2-mm sieve and kept moist to study arylamidase (EC 3.4.11.2), l-asparaginase (EC 3.5.1.1), l-glutaminase (EC 3.5.1.2), and urease (EC 3.5.1.5) activities. Tillage systems affected only l-glutaminase activity in soil while cover crops affected activities of all the enzymes studied with the exception of urease. The research clearly demonstrated that in till and no-till systems, l-asparaginase activity is greater (P ≤ 0.05) in plots preceded by crimson clover than in those preceded by black oat or their mixture. Activity of the enzyme decreased from 11.7 mg NH4+–N kg−1 2 h−1 at 0–5 cm depth to 8.73 mg NH4+–N kg−1 2 h−1 at 5–10 cm and 10–15 cm depths in the no-till crimson clover plots. Arylamidase activity significantly correlated with soil organic C (r = 0.699**) and soil organic N (r = 0.764***). Amidohydrolases activities significantly correlated with soil organic N but only urease significantly correlated with soil organic C (r = 0.481*). These results indicated that incorporation of cover crops into rotations may increase enzyme activities in soils.  相似文献   

9.
A field trial was conducted during the kharif (rainy) seasons of 2002 and 2003 at the Research Farm, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, India. The trial was carried out to study the effect of planting methods, sources and levels of nitrogen on soil properties, yield and NPK uptake by rice (Oryza sativa L.) under direct seeded condition. Planting methods significantly influenced the physical, chemical and biological properties of soil. Bulk density (1.385 g cm−3), organic carbon (0.43%) and soil moisture content (15.46%) were higher in zero till seeding plots than rotavator and conventional seeding. However, infiltration rate, soil temperature, pH and electrical conductivity showed a declining trend under this treatment and were found maximum (11.54 mm h−1, 36.21 °C at 55 DAS, 30.65 °C at harvest, 7.59 and 0.47 ds m−1) with conventional seeding. The maximum population of bacteria (25.60 × 105), fungi (14.26 × 104) and azotobactor (10.19 × 103) were found in the plot with zero till seeding while in case of actinomycetes the highest population (25.61 × 105) was found in conventional seeding. Nitrogen sources as well as levels failed to bring about any significant change in the soil properties. The highest grain (3825 kg ha−1) and straw yields (5446 kg ha−1) and N, P, K uptake were recorded in conventional seeding and were found significantly superior to zero till seeding (3144 kg ha−1) but it remained at par with rotavator seeding (3585 kg ha−1). Among the nitrogen sources, neem (Azadirachta indica) coated urea produced significantly higher grain (3761 kg ha−1) and straw yields (5396 kg ha−1) with greater NPK uptake than prilled urea and prilled urea + spent mentha. (The distillation waste of mint (Mentha arvensis) herbage is known as spent mentha.) Application of 150 kg N ha−1 produced maximum grain (3828 kg ha−1) and straw yields (5460 kg ha−1) although it remained at par with 100 kg N ha−1 (3738 and 5393 kg ha−1).  相似文献   

10.
The population abundance of free-living and plant-parasitic nematodes was investigated in a long-term rotation/tillage/stubble management experiment at Wagga Wagga Agricultural Institute, New South Wales (NSW), Australia. The treatments were a combination of two crop rotations: wheat (Triticum aestivum)–wheat and wheat–lupin (Lupinus angustifolius); two tillage systems: conventional cultivation (CC) and direct drill (DD); and two stubble management practices: stubble retention (SR) and stubble burnt (SB). Plots of one of the wheat–wheat treatments received urea at 100 kg N ha−1 during the cropping season. Soil samples from 0–5 and 5–10 cm depths were collected in September (maximum tillering), October (flowering) and December (after harvest), 2001, to analyse nematode abundance. Soil collected in September was also analysed for concentrations of total and labile C, and pH levels.Three nematode trophic groups, namely bacteria-feeders (primarily Rhabditidae), omnivores (primarily Dorylaimidae excluding plant-parasites and predators) and plant-parasites (Pratylenchus spp. and Paratylenchus spp.) were recorded in each soil sample. Of them, bacteria-feeders (53–99%, population range 933–2750 kg−1 soil) dominated in all soil samples. There was no difference in nematode abundance and community composition between the 0–5 cm and 5–10 cm layers of soil. The mean population of free-living and plant-parasitic nematodes varied significantly between the treatments in all sampling months. In most cases, total free-living nematode densities (Rhabditidae and Dorylaimidae) were significantly (P < 0.001) greater in wheat–lupin rotation than the wheat–wheat rotation irrespective of tillage and stubble management practices. In contrast, a greater population of plant-parasitic nematodes was recorded from plots with wheat–wheat than the wheat–lupin rotation. For treatments with wheat–wheat, total plant-parasitic nematode (Pratylenchus spp. and Paratylenchus spp.) densities were greater in plots without N-fertiliser (295–741 kg−1 soil) than the plots with N-fertiliser (14–158 kg−1 soil).Tillage practices had significant (P < 0.05) effects mostly on the population densities of plant-parasitic nematodes while stubble management had significant effects (P < 0.05) on free-living nematodes. However, interaction effects of tillage and stubble were significant (P < 0.01) for the population densities of free-living nematodes only. Population of Rhabditidae was significantly higher in conventional cultivated plots (7244 kg−1 soil) than the direct drilled (3981 kg−1 soil) plots under stubble retention. In contrast, plots with direct drill and stubble burnt had significantly higher populations of Dorylaimidae than the conventional cultivation with similar stubble management practice. No correlations between abundance of free-living nematodes, and concentration of total C and labile C in soil were observed in this study. These results showed that stubble retention contributed for enormous population density of free-living (beneficial) nematodes while conventional cultivation, irrespective of stubble management, contributed for suppressing plant-parasitic nematodes.  相似文献   

11.
The extreme climate of the northern Great Plains of North America requires cropping systems to possess a resilient soil resource in order to be sustainable. This paper summarizes the interactive effects of tillage, crop sequence, and cropping intensity on soil quality indicators for two long-term cropping system experiments in the northern Great Plains. The experiments, located in central North Dakota, were established in 1984 and 1993 on a Wilton silt loam (FAO: Calcic Siltic Chernozem; USDA1: fine-silty, mixed, superactive frigid Pachic Haplustoll). Soil physical, chemical, and biological properties considered as indicators of soil quality were evaluated in spring 2001 in both experiments at depths of 0–7.5, 7.5–15, and 15–30 cm. Management effects on soil properties were largely limited to the surface 7.5 cm in both experiments. For the experiment established in 1984, differences in soil condition between a continuous crop, no-till system and a crop–fallow, conventional tillage system were substantial. Within the surface 7.5 cm, the continuous crop, no-till system possessed significantly more soil organic C (by 7.28 Mg ha−1), particulate organic matter C (POM-C) (by 4.98 Mg ha−1), potentially mineralizable N (PMN) (by 32.4 kg ha−1), and microbial biomass C (by 586 kg ha−1), as well as greater aggregate stability (by 33.4%) and faster infiltration rates (by 55.6 cm h−1) relative to the crop–fallow, conventional tillage system. Thus, soil from the continuous crop, no-till system was improved with respect to its ability to provide a source for plant nutrients, withstand erosion, and facilitate water transfer. Soil properties were affected less by management practices in the experiment established in 1993, although organic matter related properties tended to be greater under continuous cropping or minimum tillage than crop sequences with fallow or no-till. In particular, PMN and microbial biomass C were greatest in continuous spring wheat (with residue removed) (22.5 kg ha−1 for PMN; 792 kg ha−1 for microbial biomass C) as compared with sequences with fallow (SW–S–F and SW–F) (Average=15.9 kg ha−1 for PMN; 577 kg ha−1 for microbial biomass C). Results from both experiments confirm that farmers in the northern Great Plains of North America can improve soil quality and agricultural sustainability by adopting production systems that employ intensive cropping practices with reduced tillage management.  相似文献   

12.
Organic matter influences soil structure and compactibility by binding soil mineral particles, reducing aggregate wettability, and influencing the mechanical strength of soil aggregates, which is the measure of coherence of inter-particle bonds. This work was carried out to examine how differences in water-stable aggregates influence the distribution of soil organic carbon and soil organic nitrogen under two tillage techniques [minimum tillage (only planting holes were opened) and conventional tillage (raised beds, 30 cm high, prepared manually with traditional hoes)] in soils of a Fluvisol in Owerri, southeastern Nigeria. Three pedons were dug and studied for each of the tillage technique along a soil sequence. Soil organic carbon and soil organic nitrogen distribution in whole soil and in water-stable aggregates under minimum tillage and conventional tillage were determined for the soils. Soil organic carbon contents in water-stable aggregates (WSA) of the pedons varied according to method of tillage. The highest mean values of soil organic carbon were obtained from minimum tillage and in water-stable aggregates 4.75–2.00 mm (16.03 Mg C ha−1), 1.00–0.50 mm (14.06 Mg C ha−1) and water-stable aggregates 2.00–1.00 mm (13.99 Mg C ha−1) whereas under conventional tillage, water-stable aggregates 1.00–0.50 mm with soil organic carbon of 24.6 Mg C ha−1 had the highest soil organic carbon content. Soil organic carbon correlated significantly with mean weight diameter (r = 0.48; P = 0.05; n = 15), water-stable aggregates 4.75–2.00 mm (r = 0.73; P = 0.05; n = 15), water-stable aggregates 2.00–1.00 mm (r = 0.55; P = 0.05, n = 15), water-stable aggregates 1.00–0.50 mm (r = 0.44; P = 0.05; n = 15) whereas no relationship was found between soil organic carbon and water-stable aggregates 0.50–0.25 mm (r = 0.15; P = 0.05; n = 15) and water-stable aggregates <0.25 mm (r = 0.17; P = 0.05; n = 15) in soils under minimum tillage. There was a significant correlation (r = 0.45–0.58; P = 0.05; n = 14) between all water-stable aggregates classes studied and soil organic carbon in soils under conventional tillage. Mean values of soil organic nitrogen were higher in soils under minimum tillage with 4.75–2.00 mm and 2.00–1.00 mm aggregate classes having 1.64 Mg N ha−1 and 1.57 Mg N ha−1 soil organic nitrogen when compared to 1.01 Mg N ha−1 and 1.00 Mg N ha−1 in conventionally tilled soils of the same aggregate classes, respectively. Larger water-stable aggregate classes (4.75–2.00; 2.00–1.00) had slightly more soil organic nitrogen (22–26%) than smaller aggregate classes (1.00–0.50; 0.50–0.25; >0.25) with 14–24% soil organic nitrogen in minimum tilled soils. In soils under conventional tillage, 1.00–0.50 mm, 0.50–0.25 mm and <0.25 mm aggregate classes contributed more soil organic nitrogen (19.66–22.40%) to the soil whereas larger water-stable aggregate classes contributed 19.22% soil organic nitrogen. The proportion of soil organic carbon and total nitrogen retained in soils with higher percentage of water-stable aggregates are less likely to be lost through soil and wind erosion. The higher values of SOC in the whole soil and WSA classes less than 2.00 mm are indications of positive influence of SOC on the stability of these peds.  相似文献   

13.
Nitrous oxide (N2O) is a greenhouse gas and agricultural soils are major sources of atmospheric N2O. Its emissions from soils make up the largest part in the global N2O budget. Research was carried out at the experimental fields of the Leibniz-Institute of Agricultural Engineering Potsdam-Bornim (ATB). Different types (mineral and wood ash) and levels (0, 75 and 150 kg N ha−1) of fertilization were applied to annual (rape, rye, triticale and hemp) and perennial (poplar and willow) plants every year. N2O flux measurements were performed 4 times a week by means of gas flux chambers and an automated gas chromatograph between 2003 and 2005. Soil samples were also taken close to the corresponding measuring rings. Soil nitrate and ammonium were measured in soil extracts.N2O emissions had a peak after N fertilization in spring, after plant harvest in summer and during the freezing–thawing periods in winter. Both fertilization and plant types significantly altered N2O emission. The maximum N2O emission rate detected was 1081 μg N2O m−2 h−1 in 2004. The mean annual N2O emissions from the annual plants were more than twofold greater than those of perennial plants (4.3 kg ha−1 vs. 1.9 kg ha−1). During January, N2O fluxes considerably increased in all treatments due to freezing–thawing cycles. Fertilization together with annual cropping doubled the N2O emissions compared to perennial crops indicating that N use efficiency was greater for perennial plants. Fertilizer-derived N2O fluxes constituted about 32% (willow) to 67% (rape/rye) of total soil N2O flux. Concurrent measurements of soil water content, NO3 and NH4 support the conclusion that nitrification is main source of N2O loss from the study soils. The mean soil NO3-N values of soils during the study for fertilized soils were 1.6 and 0.9 mg NO3-N kg−1 for 150 and 75 kg N ha−1 fertilization, respectively. This value reduced to 0.5 mg NO3-N kg−1 for non-fertilized soils.  相似文献   

14.
The objective of this study was to investigate the effects of biogas slurry derived from straw-rich farmyard manure on the soil microbial biomass, on the mineralization in the field and on the related crop yield. The experiment was carried out in the following four treatments: (1) fallow, (2) fallow + biogas slurry, (3) spring barley, and (4) spring barley + biogas slurry. The CO2 evolution rate ranged between 15 and 120 mg C m−2 h−1 in both fallow treatments and showed a significant exponential relationship with the soil temperature at 5 cm depth. According to the extrapolation of the CO2 evolution rates into amounts per hectare, approximately 200 kg C ha−1 or 27% of the biogas slurry derived C were mineralized to CO2 during a 50 days’ period to 18 June in the fallow treatment with biogas slurry. An additional amount of up to 29.5 kg inorganic N ha−1 could be calculated as the sum of NH4-N already present in biogas slurry at the time of amendment and from the amount of biogas slurry mineralized in the soil to NO3-N. A good agreement between measured and modelled stocks of inorganic N at 0–60 cm depth was obtained after having five-fold increased soil organic C turnover compared to the default values of the model DNDC. The mineralization data are in line with an amount of up to 21 kg ha−1 more N transferred by the barley plants to their aboveground biomass in biogas slurry treatment. The N not accounted for by the aboveground plant biomass could be explained by the belowground plant-derived N. CO2 evolution from the soil surface, inorganic N content at 0–60 cm depth and N transfer into barley aboveground biomass lead apparently to similar results after the application of biogas slurry. The soil ATP content after harvest of the barley was significantly larger in the two treatments with biogas slurry, especially in the fallow treatment indicating a positive effect on the soil microbial community.  相似文献   

15.
Management of N is the key for sustainable and profitable wheat production in a low N soil. We report results of irrigated crop rotation experiment, conducted in the North West Frontier Province (NWFP), Pakistan, during 1999–2002 to evaluate effects of residue retention, fertilizer N application and mung bean (Vigna radiata) on crop and N yields of wheat and soil organic fertility in a mung bean–wheat sequence. Treatments were (a) crop residue retained (+residue) or (b) removed (−residue), (c) 120 kg N ha−1 applied to wheat, (d) 160 kg N ha−1 to maize or (e) no nitrogen applied. The cropping system was rotation of wheat with maize or wheat with mung bean. The experiment was laid out in a spit plot design. Postharvest incorporation of crop residues significantly (p < 0.05) increased the grain and straw yields of wheat during both years. On average, crop residues incorporation increased the wheat grain yield by 1.31 times and straw yield by 1.39 times. The wheat crop also responded strongly to the previous legume (mung bean) in terms of enhanced grain yield by 2.09 times and straw yield by 2.16 times over the previous cereal (maize) treatment. Application of fertilizer N to previous maize exerted strong carry over effect on grain (1.32 times) and straw yield (1.38 times) of the following wheat. Application of N fertilizer to current wheat produced on average 1.59 times more grain and 1.77 times more straw yield over the 0 N kg ha−1 treatment. The N uptake in wheat grain and straw was increased 1.31 and 1.64 times by residues treatment, 2.08 and 2.49 times by mung bean and 1.71 and 1.86 times by fertilizer N applied to wheat, respectively. The soil mineral N was increased 1.23 times by residues, 1.34 times by mung bean and 2.49 times by the application of fertilizer N to wheat. Similarly, the soil organic C was increased 1.04-fold by residues, 1.08 times by mung bean and 1.00 times by the application of fertilizer N. We concluded that retention of residues, application of fertilizer N and involvement of legumes in crop rotation greatly improves the N economy of the cropping system and enhances crop productivity in low N soils.  相似文献   

16.
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   

17.
Mechanized agriculture is increasing rapidly in the Cerrado region of Brazil, causing concerns about water quality, off-site impacts, and sustainability. Our objective was to determine the impact of tillage on soil biological activity and aggregate stability in an Oxisol typical to the region. Three different tillage practices common to the Cerrado region (no-till, disk harrow, and disk plow) and an area under native vegetation were examined. Five different soil enzyme activities, C- and N-mineralization, organic C, total N, and aggregate distribution were determined. Total N, acid phosphatase, arylamidase, and C- and N-mineralization were the most sensitive to changes in tillage management. For each of these analyses, the no-till system had greater concentrations or activities (18–186%) than disk plow in the 0–5 cm layer. Significant differences observed in the 0–5 cm depth did not necessarily translate into total profile differences to a depth of 30 cm. No-till had significantly greater levels of total N, and C- and N-mineralization (20–127%) than the disk harrow system. Total N ranged from 1.8 to 2.2 kg m−3; C- and N-mineralization (24-day incubation) ranged from 2.8 to 6.8 and 0.04 to 0.10 kg m−3, respectively, among tillage systems and soil depths. Enzyme activities in all treatments were more strongly correlated with total soil N than with soil organic C (SOC), contrary to the norm in temperate soils where the stronger correlation is with SOC. Mean weight diameter of water stable aggregates was related to SOC (r = 0.73) and total N (r = 0.92), indicating that soil organic matter does play a significant role in stabilizing aggregates in Oxisols. Results indicated the importance of reducing tillage as a means of increasing soil biological activity of the topsoil in the Cerrado region of Brazil. By understanding the effects of tillage on soil biological properties, management systems can be implemented that improve natural nutrient cycling processes and soil structure, resulting in increased agricultural sustainability of tropical ecosystems.  相似文献   

18.
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   

19.
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   

20.
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   

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