首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 78 毫秒
1.
Soil N mineralization was quantified in two long-term experiments in northern France, in which no-till (NT) and conventional tillage (CT) had been differentiated for 33 years (Site 1) and 12 years (Site 2). Both sites had the same soil type but differed in crop rotation. N mineralization kinetics were assessed in situ in bare soil in both systems for 254 days (Site 1) and 555 days (Site 2) by taking frequent measurements of water and nitrate contents from soil layers and using the LIXIM calculation model. The N mineralization potential was also determined in soil samples incubated under controlled laboratory conditions. Small or non-significant differences in water and nitrate contents between NT and CT were apparent within the soil profiles on both sites. Net mineralization did not differ significantly between sites or tillage treatments. The amount of N mineralized from August 2003 to April 2004 was 67 ± 10 kg N ha−1 on Site 1 and 74 ± 5 kg N ha−1 on Site 2, and 161 ± 6 kg N ha−1 from August 2003 to February 2005 on Site 2. The kinetics of N mineralization versus normalized time (equivalent time at constant temperature of 15 °C and water content at field capacity) were linear during the shorter period (254 days corresponding to 120 normalized days). The slope (N mineralization rate) did not differ significantly between treatments and sites, and the average rate was 0.57 ± 0.05 kg N ha−1 nd−1. The kinetics were non-linear on Site 2 over the longer period (555 days corresponding to 350 normalized days). They could be fitted to an exponential model with a slope at the origin of 0.62 kg N ha−1 nd−1. The N mineralization kinetics obtained in laboratory incubations for 120–150 normalized days were also almost linear with no significant differences between treatments. Assuming that mineralization took place in the ploughed layer (in CT) or over the same soil mass (in NT) they were in good agreement with the kinetics determined in situ on both sites. The calculated water drainage below the sampled profile was slightly greater in NT due to lower evaporation. The calculated leached N was slightly higher in NT than CT on Site 1, but did not differ between treatments on Site 2. It is concluded that N mineralization and leaching in NT and CT were similar, despite large differences in N distribution within the soil profile and a slight difference in organic N stock.  相似文献   

2.
An 8-yr (1998–2005) field experiment was conducted on a Gray Luvisol (Boralf) soil near Star City, Saskatchewan, Canada, to determine the effects of tillage (no-tillage – NT and conventional tillage – CT), straw management (straw retained – R and straw not retained – NR) and N fertilizer (0, 40, 80 and 120 kg N ha−1, except no N to pea (Pisum sativum L.) phase of the rotation) on seed and straw yield, mass of N and C in crop, organic C and N, inorganic N and aggregation in soil, and nitrous oxide (N2O) emissions for a second 4-yr rotation cycle (2002–2005). The plots were seeded to barley (Hordeum vulgare L.) in 2002, pea in 2003, wheat (Triticum aestivum L.) in 2004 and canola (Brassica napus L.) in 2005. Seed, straw and chaff yield, root mass, and mass of N and C in crop increased with increasing N rate for barley in 2002, wheat in 2004 and canola in 2005. No-till produced greater seed (by 51%), straw (23%) and chaff (13%) yield of barley than CT in 2002, but seed yield for wheat in 2004, and seed and straw yield for canola in 2005 were greater under CT than NT. Straw retention increased seed (by 62%), straw (by 43%) and chaff (by 12%) yield, and root mass (by 11%) compared to straw removal for barley in 2002, wheat in 2004, and seed and straw yield for pea in 2003. No-till resulted in greater mass of N in seed, and mass of C in seed, straw, chaff and root than CT for barley in 2002, but mass of N and C were greater under CT than NT for wheat in 2004 and for canola in 2005 in many cases. Straw retention had greater mass of N and C in seed, straw, chaff and root in most cases compared to straw removal for barley in 2002, pea in 2003 and wheat in 2004. Soil moisture content in spring was higher under NT than CT and with R than NR in the 0–15 cm depth, with the highest moisture content in the NT + R treatment in many cases. After eight crop seasons, tillage and straw management had no effect on total organic C (TOC) and N (TON) in the 0–15 cm soil, but light fraction organic C (LFOC) and N (LFON), respectively, were greater by 1.275 Mg C ha−1 and 0.031 Mg N ha−1 with R than NR, and also greater by 0.563 Mg C ha−1 and 0.044 Mg N ha−1 under NT than CT. There was no effect of tillage, straw and N fertilization on the NH4-N in soil in most cases, but R treatment had higher NO3-N concentration in the 0–15 cm soil than NR. The NO3-N concentration in the 0–15, 15–30 and 30–60 cm soil layers increased (though small) with increasing N rate. The R treatment had 6.7% lower proportion of fine (<0.83 mm diameter) and 8.6% greater proportion of large (>38.0 mm) dry aggregates, and 4.5 mm larger mean weight diameter (MWD) compared to NR treatment. This suggests a lower potential for soil erosion when crop residues are retained. There was no beneficial effect of elimination of tillage on soil aggregation. The amount of N lost as N2O was higher from N-fertilized (580 g N ha−1) than from zero-N (155 g N ha−1) plots, and also higher in CT (398 g N ha−1) than NT (340 g N ha−1) in some cases. In conclusion, retaining crop residues along with no-tillage improved some soil properties and may also be better for the environment and the sustainability of high crop production. Nitrogen fertilization improved crop production and some soil quality attributes, but also increased the potential for NO3-N leaching and N2O-N emissions, especially when applied in excess of crop requirements.  相似文献   

3.
Burning of sugarcane residues contributes to air pollution and sugarcane producers have been forced to abandon it. The change from burning to residue retention is likely to alter the cycling of nutrients. Additionally, there is often a time gap of 6–8 months between two different sugarcane cycles during which legumes could be planted. Thus, the objective of this study was to assess the effects of burning, mulching or incorporation of sugarcane residues on residue decomposition and N mineralization (sugarcane residue management period) and subsequently upon ploughing (legume period) on N dynamics, N2 fixation, development and nutrient yields of groundnut and soybean grown between two sugarcane cycles on a sandy soil in Northeast Thailand.

Soil microbial biomass N increased when sugarcane residues were incorporated instead of burned or surface applied at 14 days after initiation of cane residue management. Thereafter, high net N mineralization was accompanied by a reduction in microbial biomass N, indicating that mineralized N was derived from microbial N turnover. However, upon ploughing after 96 days the different previous sugarcane residue management strategies had no significant (P > 0.05) effect on net mineral N and microbial biomass N during the subsequent legume period. Although, 15N enrichment in control reference plants and plant N uptake indicated significant N immobilization effects persisting into the legume crop phase, the proportion of N derived from N2 fixation (%Ndfa) or amount of N2 fixed were not significantly different between sugarcane residue management treatments. Soybean fixed more N2 (78%Ndfa, 234 kg N fixed ha−1) than groundnut (67%Ndfa, 170 kg N fixed ha−1) due to its larger N demand and a poorer utilization of soil N (64 kg N ha−1 vs. 85 kg N ha−1). Groundnut led to a positive soil N balance while that of soybean was negative due to its high nitrogen harvest index. Legume residues returned 61 and 146 kg N ha−1 to the soil for soybean and groundnut, respectively, compared to only 34–39 kg N ha−1 by fallow weeds. Sugarcane residue retention improved soil organic carbon and N content. The results suggested that although a change from burning to sugarcane residues retention led to alterations in N cycling and improved soil organic matter it did not significantly affect N2 fixation due to the uniforming action of ploughing and the extended time gap between sugarcane residue incorporation and legume planting.  相似文献   


4.
Direct drilling of autumn-sown cereal crops reduced the loss of nitrate in drainage. Losses of nitrate nitrogen in water draining from arable land have been measured for 4 seasons, 1980–1984. The field experiment was on a mole-drained clay soil in southern England. Autumn-sown cereal crops were established by direct drilling or after ploughing and traditional seed-bed preparation. Losses ranged from 3 to 75 kg N ha−1 year−1, with an average of 34 kg N ha−1 year−1. Most of the loss (about 90%) was removed via the mole-drain system. Measured loss of nitrate from the direct-drilled soil was 76% (range 48–89%) of that lost from the ploughed soil. Mole drains apparently increased loss of nitrate directly to the river system. In the absence of mole drains, nitrate loss in surface drainage averaged 6 kg N ha−1, compared with 4 kg N ha−1 in the presence of drains. However, in one year, exceptionally high amounts of nitrate (80 kg N ha−1) were lost from undrained, direct-drilled land because of poor crop establishment; deep leaching of nitrate in the undrained soil was not measured. Approximate calculations show that up to half the autumn-applied fertiliser-N was lost by leaching and up to 15% of spring applications.  相似文献   

5.
Land configuration in combination with nutrient management has the potential to improve the productivity of Alfisols and Vertisols in the semi-arid tropics. A four year (1989–1990 and 1992–1993) field experiment was conducted at Coimbatore, India on Alfisols (Chromic Cambisol) to compare the effect of land configuration and nutrient management practices on yield of rainfed sorghum (Sorghum bicolor (L.) Moench). The land configuration treatments were flat bed (FB, the traditional practice), open ridging (OR, ridges, 45 cm apart and 30 cm high) and tied ridging (TR, same as OR plus ridges were tied randomly). The manure and fertilisers were farm yard manure (FYM, livestock excreta plus litter at 5 Mg ha−1) and coir dust (CD, by-product after the extraction of coir from the coconut (Cocos nucifera L.) husk at 12.5 Mg ha−1) in combination with nitrogen (N) and phosphorus (P) fertiliser levels. Tied ridges stored 14% more soil water and produced 14% and 11% more grain and straw yields of sorghum, respectively, than did flat bed. However, crop yield in TR was comparable with OR. Application of CD at 12.5 Mg ha−1 combined with 40 kg N ha−1 and 9 kg P ha−1 was beneficial for more soil water storage and increased yield of sorghum by 7% over FYM at 5 Mg ha−1 + 40 kg N ha−1 and 9 kg P ha−1. In Vertisols (Vertic Cambisols), experiments were conducted for two years (1991–1992 and 1992–1993) to evaluate land configuration practices. The treatments were broad bed furrow (BBF, 120 cm wide bed with 30 cm wide and 15 cm deep furrows on both sides), compartmental bunding (CB, bunds of 15 cm height formed in all the four sides to form a check basin of 6 m × 5 m size), ridging (RD, ridges were formed for each and every row of the crop manually at four weeks after sowing) and FB under sorghum + pigeonpea (Cajanus cajan (L.) Millsp) and pearl millet (Pennisetum glacum (L.) Stuntz) + cowpea (Vigna unguiculata (L.) Walp) intercropping separately. Compartmental bunding stored 22% more soil moisture and increased the yield of sorghum + pigeonpea intercropping than did FB in a low rainfall year. In a high rainfall year, BBF produced 34% and 33% more grain yield of sorghum and pearl millet base crops, respectively, over FB. However, BBF and CB were comparable. Pigeonpea intercrop under sorghum followed the same trend as its base crop, whereas, yield of cowpea differed compared to the pearl millet base crop. Tied ridging and application of manures (CD or FYM) in combination with inorganic N and P fertiliser can increase the soil water storage and yield of crops compared to traditional flat bed cultivation in rainfed Alfisol and related soils of semi-arid tropics. Similarly BBF and CB land configuration practices could be adopted on Vertisols for better water conservation to increase the soil fertility and productivity of intercropping systems.  相似文献   

6.
Soil organic matter is strongly related to soil type, landscape morphology, and soil and crop management practices. Therefore, long-term (15–36-years) effects of six cropland management systems on soil organic carbon (SOC) pool in 0–30 cm depth were studied for the period of 1939–1999 at the North Appalachian Experimental Watersheds (<3 ha, Dystric Cambisol, Haplic Luvisol, and Haplic Alisol) near Coshocton, OH, USA. Six management treatments were: (1) no tillage continuous corn with NPK (NC); (2) no tillage continuous corn with NPK and manure (NTC-M); (3) no tillage corn–soybean rotation (NTR); (4) chisel tillage corn–soybean rotation (CTR); (5) moldboard tillage with corn–wheat–meadow–meadow rotation with improved practices (MTR-I); (6) moldboard tillage with corn–wheat–meadow–meadow rotation with prevalent practices (MTR-P). The SOC pool ranged from 24.5 Mg ha−1 in the 32-years moldboard tillage corn (Zea mays L.)–wheat (Triticum aestivum L.)–meadow–meadow rotation with straight row farming and annual application of fertilizer (N:P:K=5:9:17) of 56–112 kg ha−1 and cattle (Bos taurus) manure of 9 Mg ha−1 as the prevalent system (MTR-P) to 65.5 Mg ha−1 in the 36-years no tillage continuous corn with contour row farming and annual application of 170–225 kg N ha−1 and appropriate amounts of P and K, and 6–11 Mg ha−1 of cattle manure as the improved system (NTC-M). The difference in SOC pool among management systems ranged from 2.4 to 41 Mg ha−1 and was greater than 25 Mg ha−1 between NTC-M and the other five management systems. The difference in the SOC pool of NTC-M and that of no tillage continuous corn (NTC) were 16–21 Mg ha−1 higher at the lower slope position than at the middle and upper slope positions. The effect of slope positions on SOC pools of the other management systems was significantly less (<5 Mg ha−1). The effects of manure application, tillage, crop rotation, fertilizer rate, and soil and water conservation farming on SOC pool were accumulative. The NTC-M treatment with application of NPK fertilizer, lime, and cattle manure is an effective cropland management system for SOC sequestration.  相似文献   

7.
Management practices that simultaneously improve soil properties and yield are crucial to sustain high crop production and minimize detrimental impact on the environment. The objective of this study was to determine the influence of tillage and crop residue management on crop yield, N uptake and C removal in crop, soil organic C and N, inorganic N and aggregation, and nitrous oxide (N2O) emissions on a Gray Luvisol (Boralf) soil near Star City, Saskatchewan, Canada. The 4-year (1998–2001) field experiment was conducted with two tillage systems: no tillage (NT), and conventional tillage (CT); two levels of straw: straw retained (S), and straw removed (NS); and four rates of fertilizer N: 0, 40, 80, and 120 kg N ha−1, except no N to pea phase of the rotation. The plots were seeded to barley (Hordeum vulgare L.) in 1998, pea (Pisum sativum L.) in 1999, wheat (Triticum aestivum L.) in 2000 and canola (Brassica napus L.) in 2001. Tillage and straw treatments generally had no effect on crop yield during the first three years. But in 2001, NT produced 55, 32, and 20% greater canola seed, straw and chaff than CT, respectively, whereas straw retention increased seed and straw yield by 33 and 19% compared to straw removal. Seed, straw and chaff yield of canola increased with N rate up to 40 kg N ha−1, and root mass (0–15 cm depth) with N rate to 80 kg N ha−1. Amount of N uptake and C removed in wheat and canola generally increased with N rate, but tillage and straw management had no consistent effect. After four crop seasons, total organic C (TOC) and N (TN), light fraction organic matter (LFOM), C (LFC), and N (LFN) were generally greater with S than NS treatments. Tillage did not affect TOC and TN in soil, but LFOM, LFC, and LFN were greater or tended to be greater under NT than CT. There was no effect of tillage, straw and N fertilization on NH4-N in soil, but CT and S tended to have higher NO3-N concentration in 0–15 cm soil than NT and NS, respectively. Concentration of NO3-N increased substantially with N rate ≥80 kg ha−1. The NT + S treatment had the lowest proportion (34%) of wind-erodible (<0.83 mm diameter) aggregates and greatest proportion (37%) of larger (>12.7 mm) dry aggregates, compared to highest (50%) and lowest (18%) proportion of corresponding aggregates in CT + NS, indicating less potential for soil erosion when tillage was omitted and crop residues were retained. Amount of N lost as N2O was higher from N-fertilized than from zero-N plots, and it was substantially higher from N-applied CT plots than from N-applied NT plots. Retaining crop residues along with no-tillage improved soil properties and may also be better for the environment.  相似文献   

8.
Improved-fallow agroforestry systems are increasingly being adopted in the humid tropics for soil fertility management. However, there is little information on trace gas emissions after residue application in these systems, or on the effect of tillage practice on emissions from tropical agricultural systems. Here, we report a short-term experiment in which the effects of tillage practice (no-tillage versus tillage to 15 cm depth) and residue quality on emissions of N2O, CO2 and CH4 were determined in an improved-fallow agroforestry system in western Kenya. Emissions were increased following tillage of Tephrosia candida (2.1 g N2O-N ha−1 kg N applied−1; 759 kg CO2-C ha−1 t C applied−1; 30 g CH4-C ha−1 t C applied−1) and Crotalaria paulina residues (2.8 g N2O-N ha−1 kg N applied−1; 967 kg CO2-C ha−1 t C applied−1; 146 g CH4-C ha−1 t C applied−1) and were higher than from tillage of natural-fallow residues (1.0 g N2O-N ha−1 kg N applied−1; 432 kg CO2-C ha−1 t C applied−1; 14.7 g CH4-C ha−1 t C applied−1) or from continuous maize cropping systems. Emissions from these fallow treatments were positively correlated with residue N content (r = 0.62–0.97; P < 0.05) and negatively correlated with residue lignin content (r = −0.56, N2O; r = −0.92, CH4; P < 0.05). No-tillage of surface applied Tephrosia residues lowered the total N2O and CO2 emitted over 99 days by 0.33 g N2O-N ha−1 kg N applied−1 and 124 kg CO2-C ha−1 t C applied−1, respectively; estimated to provide a reduction in global warming potential of 41 g CO2 equivalents. However, emissions were increased from this treatment over the first 2 weeks. The responses to tillage practice and residue quality reported here need to be verified in longer term experiments before they can be used to suggest mitigation strategies appropriate for all three greenhouse gases.  相似文献   

9.
Wheat (Triticum aestivum L.) yield and quality is influenced by management of the previous crop but is highly dependent on current year management. The objective of this study was to evaluate the response of winter wheat seeded in two tillage systems [conventional tillage (CT) and no-till (NT)] to four N rates applied to a previous cotton (Gossypium hirsutum L.) crop (0, 67, 134, and 202 kg ha−1). The experiment with wheat was conducted on a Dothan sandy loam (fine, loamy siliceous, thermic Plinthic Kandiudults) at the University of Florida North Florida Research and Education Center near Quincy, FL from 1995 to 1997. For most plant characteristics, there was a tillage x N x year interaction. Greater plant emergence (79.4 vs. 65.3%) and grain N (23.5 vs. 21.5 g kg−1), and lower grain moisture (139 vs. 142 g kg−1) were obtained under NT than CT, respectively, in one out of two years. Nitrogen applied to a previous cotton crop increased wheat grain yields, plant height and seed number under NT in 1995–1996 and CT in 1996–1997, head density under NT in both years, harvest index under CT in 1996–1997, and grain N concentration in 1995–1996 and 1996–1997 due to residual plant and soil N. With every 1 kg N applied to a previous cotton crop, wheat grain yields increased by 5.38 kg ha−1 under NT, whereas grain yield under CT was not influenced by N application to cotton in 1995–1996. In 1996–1997, grain yields increased by 4.96 and 4.23 kg ha−1 for wheat grown in NT and CT, respectively. Generally, wheat seeded in NT following cotton did not decrease stand or yields compared to CT and wheat grain yields and grain N content increased with N fertilization of the previous crop. However, we would have to apply about 134 kg N ha−1 to a previous cotton crop to maximize wheat production under NT and CT.  相似文献   

10.
A detailed short-term (12 d) laboratory study was carried out to investigate the effects of applying animal urine, fertilizer (ammonium nitrate) and fertilizer+urine on emission of NO and N2O from soil. A complementary 24 d field study measured the effect of fertilizer or fertilizer+sheep grazing on NO and N2O emissions from pasture. The data generated were used to interpret the transformations responsible for the release of these gases. Application of urine to the soil (at a rate equivalent to 930 kg N ha−1) increased the amount of mineral and microbial N in the soil. This was followed by increases in emissions of NO (from 0.02 to 1.76 mg NO-N m−2 d−1) and N2O (from 15 to 330 mg N2O-N m−2 d−1). Molar ratios of NO-N-to-N2O-N were very low (<0.001 to 0.011) indicating that denitrification was the main process during the first 12 d after application. In the laboratory, nitrification was inhibited during the first 7 d due to an inhibitory effect of the urine, but even though nitrification was clearly underway 7–12 d after application, denitrification was still the dominant process. The fertilizer was applied at a lower rate (120 kg N ha−1) than the urine. Consequently, the effect on soil mineral N was smaller. Nevertheless the fertilizer still increased NO and N2O emission with denitrification the dominant process. The effects of fertilizer and grazing on NO and N2O emissions was less obvious in the field compared with the laboratory and fluxes returned to background rates within 4 d. This was attributed to the rapid decline in soil mineral N in the field trial due to plant uptake and leaching, processes that did not occur in the laboratory.  相似文献   

11.
Seventy years of different management treatments have produced significant differences in runoff, erosion, and ponded infiltration rate in a winter wheat (Triticum aestivum L.)–summer fallow experiment in OR, USA. We tested the hypothesis that differences in infiltration are due to changes in soil structure related to treatment-induced biological changes. All plots received the same tillage (plow and summer rod-weeding). Manure (containing 111 kg N ha−1), pea (Pisum sativum L.), vine (containing 34 kg N ha−1), or N additions of 0, 45 and 90 kg ha−1 were treatment variables with burning of residue as an additional factor within N-treatments. We measured soil organic C and N, water stability of whole soil, water stable aggregates, percolation through soil columns, glomalin, soil-aggregating basidiomycetes, earthworm populations, and dry sieve aggregate fractions. Infiltration was correlated (r = 0.67–0.95) to C, N, stability of whole soil, percolation, and glomalin. Basidiomycete extracellular carbohydrate assay values and earthworm populations did not follow soil C concentration, but appeared to be more sensitive to residue burning and to the addition of pea vine residue and manure. Dry sieve fractions were not well correlated to the other variables. Burning reduced (p < 0.05) water stability of whole soil, total glomalin, basidiomycetes, and earthworm counts. It also reduced dry aggregates of 0.5–2.0 mm size, but neither burning nor N fertilizer affected total C or total N or ponded infiltration rate. Water stability of whole soil and of 1–2-mm aggregates was greater at 45 kg N ha−1 than in the 0 and 90 kg N ha−1 treatments. Zero N fertilizer produced significantly greater 0.5–2.0 mm dry aggregate fractions. We conclude that differences in infiltration measured in the field are related to relatively small differences in aggregate stability, but not closely related to N or residue burning treatments. The lack of an effect of N fertilizer or residue burning on total C and N, along with the excellent correlation between glomalin and total C (r = 0.99) and total N (r = 0.98), indicates that the major pool of soil carbon may be dependent on arbuscular mycorrhizal fungi.  相似文献   

12.
Despite being one of the most profitable crops for the southeastern USA, cotton (Gossypium hirsutum L.) is considered to create a greater soil erosion hazard than other annual crops such as corn (Zea mays L.) and soybeans (Glycine max (L.) Merr.). Reduced tillage systems and cover cropping can reduce soil erosion and leaching of nutrients into ground water. The objectives of this study, which was conducted in north Alabama from 1996 to 1998, were to assess the impact of no-till and mulch-till systems with a winter rye (Secale cereale L.) cover crop and poultry litter on soil erosion estimates in cotton plots using the revised universal soil loss equation (RUSLE). Soil erosion estimates in conventional till plots with or without a winter rye cover crop and ammonium nitrate fertilizer were double the 11 t ha−1 yr−1 tolerance level for the Decatur series soils. However, using poultry litter as the N source (100 kg N ha−1) gave soil erosion estimates about 50% below the tolerance level under conventional till. Doubling the N rate through poultry litter to 200 kg N ha−1 under no-till system gave the lowest soil erosion estimate level. No-till and mulch-till gave erosion estimates which were about 50% of the tolerance level with or without cover cropping or N fertilization. This study shows that no-till and mulch-till systems with cover cropping and poultry litter can reduce soil erosion in addition to increasing cotton growth and lint yields, and thus improve sustainability of cotton soils in the southeastern USA.  相似文献   

13.
Yield decline or stagnation and its relationship with soil organic matter fractions in soybean (Glycine max L.)–wheat (Triticum aestivum L.) cropping system under long-term fertilizer use are not well understood. To understand this phenomenon, soil organic matter fractions and soil aggregate size distribution were studied in an Alfisol (Typic Haplustalf) at a long-term experiment at Birsa Agricultural University, Ranchi, India. For 30 years, the following fertilizer treatments were compared with undisturbed fallow plots (without crop and fertilizer management): unfertilized (control), 100% recommended rate of N, NP, NPK, NPK+ farmyard manure (FYM) and NPK + lime. Yield declined with time for soybean in control (30 kg ha−1 yr−1) and NP (21 kg ha−1 yr−1) treatments and for wheat in control (46 kg ha−1 yr−1) and N (25 kg ha−1 yr−1) treatments. However, yield increased with time for NPK + FYM and NPK + lime treatments in wheat. At a depth of 0–15 cm, small macroaggregates (0.25–2 mm) dominated soil (43–61%) followed by microaggregates (0.053–0.25 mm) with 13–28%. Soil microbial biomass carbon (SMBC), nitrogen (SMBN) and acid hydrolysable carbohydrates (HCH) were greater in NPK + FYM and NPK + lime as compared to other treatments. With three decades of cultivation, C and N mineralization were greater in microaggregates than in small macroaggregates and relatively resistant mineral associated organic matter (silt + clay fraction). Particulate organic carbon (POC) and nitrogen (PON) decreased significantly in control, N and NP application over fallow. Results suggest that continuous use of NPK + FYM or NPK + lime would sustain yield in a soybean–wheat system without deteriorating soil quality.  相似文献   

14.
Cover crops may influence soil carbon (C) sequestration and microbial biomass and activities by providing additional residue C to soil. We examined the influence of legume [crimson clover (Trifolium incarnatum L.)], nonlegume [rye (Secale cereale L.)], blend [a mixture of legumes containing balansa clover (Trifolium michelianum Savi), hairy vetch (Vicia villosa Roth), and crimson clover], and rye + blend mixture cover crops on soil C fractions at the 0–150 mm depth from 2001 to 2003. Active fractions of soil C included potential C mineralization (PCM) and microbial biomass C (MBC) and slow fraction as soil organic C (SOC). Experiments were conducted in Dothan sandy loam (fine-loamy, kaolinitic, thermic, Plinthic Kandiudults) under dryland cotton (Gossypium hirsutum L.) in central Georgia and in Tifton loamy sand (fine-loamy, siliceous, thermic, Plinthic Kandiudults) under irrigated cotton in southern Georgia, USA. Both dryland and irrigated cotton were planted in strip tillage system where planting rows were tilled, thereby leaving the areas between rows untilled. Total aboveground cover crop and cotton C in dryland and irrigated conditions were 0.72–2.90 Mg C ha−1 greater in rye + blend than in other cover crops in 2001 but was 1.15–2.24 Mg C ha−1 greater in rye than in blend and rye + blend in 2002. In dryland cotton, PCM at 50–150 mm was greater in June 2001 and 2002 than in January 2003 but MBC at 0–150 mm was greater in January 2003 than in June 2001. In irrigated cotton, SOC at 0–150 mm was greater with rye + blend than with crimson clover and at 0–50 mm was greater in March than in December 2002. The PCM at 0–50 and 0–150 mm was greater with blend and crimson clover than with rye in April 2001 and was greater with crimson clover than with rye and rye + blend in March 2002. The MBC at 0–50 mm was greater with rye than with blend and crimson clover in April 2001 and was greater with rye, blend, and rye + blend than with crimson clover in March 2002. As a result, PCM decreased by 21–24 g CO2–C ha−1 d−1 but MBC increased by 90–224 g CO2–C ha−1 d−1 from June 2001 to January 2003 in dryland cotton. In irrigated cotton, SOC decreased by 0.1–1.1 kg C ha−1 d−1, and PCM decreased by 10 g CO2–C ha−1 d−1 with rye to 79 g CO2–C ha−1 d−1 with blend, but MBC increased by 13 g CO2–C ha−1 d−1 with blend to 120 g CO2–C ha−1 d−1 with crimson clover from April 2001 to December 2002. Soil active C fractions varied between seasons due to differences in temperature, water content, and substrate availability in dryland cotton, regardless of cover crops. In irrigated cotton, increase in crop C input with legume + nonlegume treatment increased soil C storage and microbial biomass but lower C/N ratio of legume cover crops increased C mineralization and microbial activities in the spring.  相似文献   

15.
A 3-year field study was conducted to evaluate the effect of three tillage practices (conventional, zero and reduced/strip) with two nitrogen levels (120 and 150 kg N ha−1) applied in primary strips and three crop residue management practices (removal, burning and incorporation) in secondary strips in wheat after rice. Reduced tillage resulted in significantly higher overall mean wheat yield (5.10 Mg ha−1) compared to conventional (4.60 Mg ha−1) and zero tillage (4.75 Mg ha−1). Residue incorporation resulted in highest mean yield (5.86 Mg ha−1) during third year. Maximum mean yield (6.1 Mg ha−1) was obtained in reduced tillage followed by conventional tillage (5.8 Mg ha−1) under residue incorporation in third year. The weed dry weight recorded at 30 days after sowing was highest (0.3 Mg ha−1) under zero tillage and lowest under conventional tillage (0.16 Mg ha−1). Among crop residue management practices, the highest dry weight of weeds (0.22 Mg ha−1) was recorded under residue incorporation. The highest infiltration rate (1.50 cm h−1) was recorded in residue incorporation followed by residue burning (1.44 cm h−1) whereas; the lowest (0.75 cm h−1) in zero tillage. Soil bulk density was the highest (1.69 Mg m−3) under zero tillage and the lowest in residue incorporation (1.59 Mg m−3). There were no changes in soil available P and K after each crop sequence in relation to tillage practices during first 2 years. Higher organic carbon (5.1–5.4 g kg−1) was measured under zero tillage compared to other treatments. Residue incorporation increased soil organic carbon and available P while higher available K was monitored in burning treatment during the third year. These results suggest that reduced tillage and in situ incorporation of crop residues at 5 Mg ha−1 along with 150 kg N ha−1 were optimum to achieve higher yield of wheat after rice in sandy loam soils of Indo-Gangetic plains of India.  相似文献   

16.
In a region where water is the primary limiting factor of crop production, loss of water from fields by overland flow represents an economic loss to producers. Traditional crop management practices in north-central Oregon have led to crop water loss by overland flow. In 1931, a long-term experiment was begun near Pendleton, Oregon, in a Walla Walla silt loam (coarse-silty, mixed, mesic Typic Haploxeroll—US; Kastanozems—FAO), to examine the influence on soil fertility and crop production by nutrient amendments and crop residue management practices. This experiment provided the opportunity to evaluate the influence of a several traditional farming practices on field hydrology. Tillage in all treatments consisted of moldboard plowing and multiple passes with secondary tillage equipment to smooth the surface for planting and for weed control. The treatments were combinations of nutrient amendments (0.90 kg N ha−1 commercial fertilizer, and 145 kg N ha−1 from manure) and residue management (fall-burn, spring-burn, and no-burn), whose soil organic carbon increased with increasing nutrient amendments. These treatments were in a winter wheat–fallow system and represent a set of past and current cultural practices. Overland flow from these treatments was measured. Lister furrows separated the plots of 12 m×40 m (≈0.05 ha) to prevent overland flow from treatment to treatment and were instrumented with weirs to capture and measure overland flow. To determine if hydrologic differences existed between treatments, we tested the overland flow to precipitation (Q/P) ratio. The Q/P ratio (P<0.15) was greatest within crop year/low soil fertility (0 kg N ha−1, burn) whereas the high fertility (145 kg N ha−1, no-burn) treatment crop year plots Q/P ratios were similar to fallow, standing stubble plots. Most notably, the manure amendment plots in crop, produce significantly less overland flow than the other residue and nutrient management practices, and marginally less overland flow than treatments in stubble. This research demonstrates that overland flow was greater from low fertility and stubble burned treatments. Increased overland flow increases the risk of soil erosion and loss of water to overland flow is potentially a loss of needed soil water for crop growth and production.  相似文献   

17.
Conservation management systems can improve soil organic matter stocks and contribute to atmospheric C mitigation. This study was carried out in a 18-year long-term experiment conducted on a subtropical Acrisol in Southern Brazil to assess the potential of tillage systems [conventional tillage (CT) and no-till (NT)], cropping systems [oat/maize (O/M), vetch/maize (V/M) and oat + vetch/maize + cowpea (OV/MC)] and N fertilization [0 kg N ha−1 year−1 (0 N) and 180 kg N ha−1 year−1 (180 N)] for mitigating atmospheric C. For that, the soil organic carbon (SOC) accumulation and the C equivalent (CE) costs of the investigated management systems were taken into account in comparison to the CT O/M 0 N used as reference system. No-till is known to produce a less oxidative environment than CT and resulted in SOC accumulation, mainly in the 0–5 cm soil layer, at rates related to the addition of crop residues, which were increased by legume cover crops and N fertilization. Considering the reference treatment, the SOC accumulation rates in the 0–20 cm layer varied from 0.09 to 0.34 Mg ha−1 year−1 in CT and from 0.19 to 0.65 Mg ha−1 year−1 in NT. However, the SOC accumulation rates peaked during the first years (5th to 9th) after the adoption of the management practices and decreased exponentially over time, indicating that conservation soil management was a short-term strategy for atmospheric C mitigation. On the other hand, when the CE costs of tillage operations were taken into account, the benefits of NT to C mitigation compared to CT were enhanced. When CE costs related to N-based fertilizers were taken into account, the increases in SOC accumulation due to N did not necessarily improve atmospheric C mitigation, although this does not diminish the agricultural and economic importance of inorganic N fertilization.  相似文献   

18.
In the dry savannas of west and central Africa, where low soil fertility is major constraint to maize production, the development of tropical maize genotypes with high and stable yield under low-nitrogen condition is very important, since access to these improved genotypes may be the only affordable alternative to many small scale farmers.

Field trials were conducted at Samaru (Typic Haplustalfs) to investigate the response of low-N tolerant maize cultivars to nitrogen (N) fertilizer. Nitrogen application rates were 0, 30, 60, 90 kg N ha−1 and four maize cultivars (Low-N pool C2, ACR 8328 BN C7, Super Oba II and TZR-SR). Maize leaf area index, intercepted radiation, leaf area and stover weights were increased due to nitrogen application at flowering. For most of the parameters, 60 kg N ha−1 appeared to have the significantly high values. However, there was no significant difference between application rates of 60 and 90 kg N ha−1 in stem weight, stover weight, grain yield and shelling percent at harvest. Genotypic variation observed in the maize agronomic traits were not significant except in leaf weight and grain yield. The amount of nitrogen taken by maize increased with increase in fertilizer rates. Application of 30 and 90 kg N ha−1 to soil increased the maize grain N concentration and total N uptake. About 45.3 kg ha−1 and 8.8 g N kg−1 nitrogen uptake was obtained in maize shoot and grain, respectively, at the application of 90 kg N ha−1. Low-N pool C2 genotype had the highest grain N concentration and shoot uptake significantly higher than TZB-SR. Nitrogen fertilizer applied accounted for 97% variation in soil nitrate. There existed a positive and significant correlation between maize grain yield and leaf nitrogen uptake (r = 0.33, P < 0.01). Averagely, nitrogen fertilizer applied accounted for 86% variations in maize grain yield.  相似文献   


19.
Tillage, organic resources and fertiliser effects on soil carbon (C) dynamics were investigated in 2000 and 2001 in Burkina Faso (West Africa). A split plot design with four replications was laid-out on a loamy-sand Ferric Lixisol with till and no-till as main treatments and fertiliser types as sub-treatments. Soil was fractionated physically into coarse (0.250–2 mm), medium (0.053–0.250 mm) and fine fractions (< 0.053 mm). Particulate organic carbon (POC) accounted for 47–53% of total soil organic carbon (SOC) concentration and particulate organic nitrogen (PON) for 30–37% of total soil nitrogen concentration. The POC decreased from 53% of total SOC in 2000 to 47% of total SOC in 2001. Tillage increased the contribution of POC to SOC. No-till led to the lowest loss in SOC in the fine fraction compared to tilled plots. Well-decomposed compost and single urea application in tilled as well as in no-till plots induced loss in POC. Crop N uptake was enhanced in tilled plots and may be up to 226 kg N ha−1 against a maximum of 146 kg N ha−1 in no-till plots. Combining crop residues and urea enhanced incorporation of new organic matter in the coarse fraction and the reduction of soil carbon mineralisation from the fine fraction. The PON and crop N uptake are strongly correlated in both till and no-till plots. Mineral-associated N is more correlated to N uptake by crop in tilled than in no-till plots. Combining recalcitrant organic resources and nitrogen fertiliser is the best option for sustaining crop production and reducing soil carbon decline in the more stabilised soil fraction in the semi-arid West Africa.  相似文献   

20.
The effect of soil incorporations of lantana (Lantana spp.) biomass, an obnoxious weed, on physical environment of a silty clay loam soil (Typic Hapludalf) under rice (Oryza sativa L.)–wheat (Triticum aestivum L.) cropping was studied in a long-term field experiment conducted in a wet temperate region of north India. Fresh lantana biomass was incorporated into the plough layer at 10, 20 and 30 Mg ha−1 annually, 7–10 days before puddling. Plant-available water capacity (PAWC), non-limiting water range (NLWR) and NLWR:PAWC ratio were determined to characterize soil physical environment during wheat crop in the tenth cropping cycle.

Ten annual applications of lantana at 10, 20 and 30 Mg ha−1, increased organic carbon (OC) content over control by 12.6, 17.6 and 27.9% in 0–15 cm soil layer, and 17.1, 26.3 and 39.5% in 15–30 cm soil layer, respectively. The OC content in 0–15 and 15–30 cm soil layer of control plots was 11.1 and 7.6 g kg−1 soil. Bulk density decreased by 3–14% in 7.5–10.5 cm layer and 1–6% in 15–18 cm layer. Volumetric moisture contents at 10% air-filled porosity were 38.4, 40.0, 54.5 and 55.7% at 7.5–10.5 cm depth, and 31.4, 32.2, 33.9 and 34.6% at 15–18 cm depth corresponding to 0, 10, 20 and 30 Mg ha−1 lantana treatment, respectively. At 15–18 cm soil depth, volumetric moisture contents at 2 MPa soil penetration resistance were 26.9, 24.8, 23.0 and 19.6% in zero, 10, 20 and 30 Mg ha−1 lantana-treated plots, respectively. Lower soil water contents associated with 10% air-filled porosity and greater soil water contents associated with a limiting penetration resistance of 2 MPa resulted in a lower NLWR (4.3%) for control as compared to lantana-treated soil (7.4–15.1%). The PAWC showed slight increase from 12.9 to 13.4–14.9% due to lantana additions. The NLWR:PAWC ratio was also lower in control (0.33) as compared to lantana-treated soil (0.55–1.01). The NLWR was significantly and positively correlated with wheat grain yield (r=0.858**).  相似文献   


设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号