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1.
Prediction of potentially mineralizable N as an important N pool from soil amidohydrolases was investigated. Composite soil samples were collected from plots of a field experiment in which 0, 50 and 100 Mg cow manure ha−1 year−1 had been applied for five consecutive years. The soils were treated with corn shoots or roots or remained untreated in a factorial combination with the manure treatments, with three replications. The mineralized inorganic N was measured periodically in 20-week incubations and potentially mineralizable N (N0) was calculated based on a first-order kinetic model. Urease, l-glutaminase and l-asparaginase activities were measured before and after incubation. The values of N0 ranged from 208.6 in the controls to 388.4 in soils that had received 50 Mg ha−1 year−1 of cow manure and were amended with corn shoots. Corn residue amendment in the manure treated soils, increased the values of N0 or changed the N mineralization kinetic pattern from a first-order to a zero-order model. According to a relative sensitivity index, l-asparaginase was the most sensitive enzyme to the treatments. Multiple regression analysis revealed that 92% of N0 variations can be described by the activities of urease and l-asparaginase and therefore the soil amidohydrolase activities have the potential to evaluate potentially mineralizable N.  相似文献   

2.
探讨秸秆还田与施氮对高纬度黑土区春玉米产量与温室气体排放特性的影响,对促进粮食增产和降低环境代价具有重要意义。本研究通过位于黑土区的大田定位试验,利用静态箱-气相色谱计数方法,在秸秆还田与不还田和3个氮素用量(纯N:120 kg·hm~(-2),240 kg·hm~(-2)和300 kg·hm~(-2))条件下,研究了春玉米不同生育时期农田土壤CO2、N2O和CH4综合温室效应与排放强度,以及土壤过氧化氢酶和脲酶活性的变化。结果表明:无秸秆还田时,高氮用量处理春玉米产量最高;秸秆还田后,中等氮用量处理(240 kg·hm~(-2))春玉米产量最高,且与无秸秆还田的高氮处理间无显著差异。无秸秆还田时,随施氮量增加,CO2、N2O和CH4排放量均显著提高,综合温室效应和土壤温室气体排放量与强度显著增加(P0.05);增施氮肥配合秸秆还田,增加了CO2和N2O的排放量,而土壤CH4的碳汇功能增强,温室气体排放量与强度未显著提高(P0.05)。无秸秆还田,增施氮肥降低了土壤过氧化氢酶活性但提高了土壤脲酶活性;而秸秆还田使得增施氮肥引起的土壤过氧化氢酶活性降低的幅度加大但土壤脲酶活性提高的幅度变小。因此,秸秆还田后配合中等用量氮处理(240 kg·hm~(-2))玉米产量最高,且能够抑制单纯增施氮肥对综合温室效应和土壤温室气体排放强度的促进作用,推荐在生产中参考使用。  相似文献   

3.
Summary Non-symbiotic N2 fixation was studied under laboratory conditions in two soils from Pakistan (Hafizabad silt loam and Khurrarianwala silt loam) and one from Illinois, USA (Drummer silty clay loam) incubated in a 15N-enriched atmosphere. N2 fixation was greatest with the Drummer soil (18–122 g g–1 soil, depending upon the soil treatment) and lowest with the Khurrarianwala soil (4–81 g g–1 soil). Fixation was increased by the addition of glucose, a close correlation being observed between the amount of glucose added and the amount of N2 fixed in the three soils (r = 0.96). Efficiency of N2 fixation varied with soil type and treatment and was greatest in the presence of added inorganic P. Application of Mo apparently had a negative effect on the amount and efficiency of N2 fixation in all the soils. The percentage of non-symbiotically fixed 15N in potentially mineralizable form (NH 4 + -N released in soil after a 15-day incubation period under anaerobic conditions) was low (2%–18%, depending upon the soil treatment), although most of the fixed N (up to 90%) was recovered as forms hydrolysable with 6N HCl. Recovery in hydrolysable forms was much greater for the fixed N than for the native soil N, indicating that the former was more available for uptake by plants.  相似文献   

4.
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   

5.
Application of crop residues and its biochar produced through slow pyrolysis can potentially increase carbon (C) sequestration in agricultural production systems. The impact of crop residue and its biochar addition on greenhouse gas emission rates and the associated changes of soil gross N transformation rates in agricultural soils are poorly understood. We evaluated the effect of wheat straw and its biochar applied to a Black Chernozemic soil planted to barley, two growing seasons or 15 months (at the full-bloom stage of barley in the second growing season) after their field application, on CO2 and N2O emission rates, soil inorganic N and soil gross N transformation rates in a laboratory incubation experiment. Gross N transformation rates were studied using the 15N isotope pool dilution method. The field experiment included four treatments: control, addition of wheat straw (30 t ha?1), addition of biochar pyrolyzed from wheat straw (20 t ha?1), and addition of wheat straw plus its biochar (30 t ha?1 wheat straw + 20 t ha?1 biochar). Fifteen months after their application, wheat straw and its biochar addition increased soil total organic C concentrations (p?=?0.039 and <0.001, respectively) but did not affect soil dissolved organic C, total N and NH4 +-N concentrations, and soil pH. Biochar addition increased soil NO3 ?-N concentrations (p?=?0.004). Soil CO2 and N2O emission rates were increased by 40 (p?p?=?0.03), respectively, after wheat straw addition, but were not affected by biochar application. Straw and its biochar addition did not affect gross and net N mineralization rates or net nitrification rates. However, biochar addition doubled gross nitrification rates relative to the control (p?2 and N2O emissions and enhance soil C sequestration. However, the implications of the increased soil gross nitrification rate and NO3 ?-N in the biochar addition treatment for long-term NO3 ?-N dynamics and N2O emissions need to be further studied.  相似文献   

6.
Concentrations of CH4, a potent greenhouse gas, have been increasing in the atmosphere at the rate of 1% per year. The objective of these laboratory studies was to measure the effect of different forms of inorganic N and various N-transformation inhibitors on CH4 oxidation in soil. NH 4 + oxidation was also measured in the presence of the inhibitors to determine whether they had differential activity with respect to CH4 and NH 4 + oxidation. The addition of NH4Cl at 25 g N g-1 soil strongly inhibited (78–89%) CH4 oxidation in the surface layer (0–15 cm) of a fine sandy loam and a sandy clay loam (native shortgrass prairie soils). The nitrification inhibitor nitrapyrin (5 g g-1 soil) inhibited CH4 oxidation as effectively as did NH4Cl in the fine sandy loam (82–89%), but less effectively in the sandy clay loam (52–66%). Acetylene (5 mol mol-1 in soil headspace) had a strong (76–100%) inhibitory effect on CH4 consumption in both soils. The phosphoroamide (urease inhibitor) N-(n-butyl) thiophosphoric triamide (NBPT) showed strong inhibition of CH4 consumption at 25 g g-1 soil in the fine sandy loam (83%) in the sandy clay loam (60%), but NH 4 + oxidation inhibition was weak in both soils (13–17%). The discovery that the urease inhibitor NBPT inhibits CH4 oxidation was unexpected, and the mechanism involved is unknown.  相似文献   

7.
The effects of soil incorporation with cereal straw (nil, 2.5, 5 and 10 t straw ha–1) and direct drilling on the proportion and amount of pea N derived from biological N fixation were investigated in three field experiments. Fixed N was determined by15N dilution using barley as a reference plant. The three sites were on acidic, red clay-loams in the cropping zone of southeastern Australia. Seasonal plant available soil N, as determined by the N accumulated in barley, was 31, 56 and 158 kg N ha–1, for the three sites. Incorporated straw reduced soil nitrate at sowing by 10–50 kg N ha–1 (0–30 cm), and 5 or 10 t straw ha–1 reduced barley uptake of N by 10–38 kg N ha–1. However, reducing plant available soil N was generally ineffective for increasing the N fixed by pea. Fixed N increased only at the site with the least plant-available N, and only one-third of the increase could be attributed to lower soil N uptake by pea. There was no evidence that direct drilling pea increased fixed N by decreasing crop uptake of soil N. It is proposed that a lower requirement for soil N by pea as compared to barley, and availability of mineral N beneath the soil layer treated with straw, minimise the effectiveness of straw incorporation for increasing the N fixed by pea.  相似文献   

8.
Summary A 2-year study (1983–1984 to 1984–1985) was conducted to estimate temporal and seasonal changes and the effects of fertiliser on some soil chemical, biochemical and microbiological characteristics. The soil used was a Typic Vitrandept under grazed pasture. Soil samples were taken regularly to a depth of 75 mm from paired unfertilised and fertilised (500 kg ha– 30% potassic superphosphate) plots. Except for organic C, fertiliser had little or no effect on the characteristics measured. Organic C averaged about 9.2% in unfertilised soil and was about 0.3% higher in the fertilised soil. The size of the microbial biomass fluctuated widely in the 1st year (3000 g C g–1 in February to 1300 g C g–1 in September) but there was less variation in the 2nd year (range 1900 g C g–1 to 2500 g C g–1 soil). CO2 production values (10- to 20-day estimates averaged 600 g of CO2-C g–1 soil) were generally higher in spring compared to the rest of the year. Water extractable C increased over winter and declined through spring in both years (range 50 g C g–1 soil to 150 g C g–1 soil). Mineral-N flush values were higher in summer (300 g N g–1 soil) and lower in winter months (200 g N g–1 soil). The pattern of variation of microbial N values was one of gradual accumulation followed by rapid decline. This rapid decline in values occurred in spring and autumn (range 130–220 g N g–1 soil). N mineralisation and bicarbonate-extractable N showed no clear trend; these values ranged from 100–200 and 122–190 g N g–1 soil, respectively. There was a significant correlation (0.1%) between N mineralisation and bicarbonate-extractable N in the late summer-autumn-early winter period (February–August) in both years but not in spring. These results and their relationships to climatic factors and rates of pasture production are discussed.  相似文献   

9.
Summary Under greenhouse and field conditions, after the harvest of maize-cowpea intercropping, soils were analysed for total, ammonium and organic N fractions and fertilizer 15N residues. Growing cowpea as the sole crop or in intercropping with maize results in increased relative amounts of the acid hydrolysable organic N fractions in soil. After sole cropping of maize 70% of the residual fertilizer N was found in the acid hydrolysable fraction while after intercropping it was 80%–92%. The fertilizer and soil N labelling with 15N in identical but alternate series provided information on the nitrogen fixed by cowpea and left in the soil as crop residues. Under field conditions the cowpea plant residues left after cropping contained 170 kg N ha–1 in sole cropping and 105 kg N ha–1 in intercropping with maize. The N assimilated by cowpea-Rhizobium symbiosis was mainly present in the acid hydrolysable forms, particularly in the -amino N fraction and ammonium N fraction.  相似文献   

10.
This study investigated the long-term effect of lime application and tillage systems (no-till, ridge-till and chisel plow) on the activities of arylamidase and amidohydrolases involved in N cycling in soils at four long-term research sites in Iowa, USA. The activities of the following enzymes were assayed: arylamidase, -asparaginase, -glutaminase, amidase, urease, and -aspartase at their optimal pH values. The activities of the enzymes were significantly (P<0.001) and positively correlated with soil pH, with r values ranging from 0.42* to 0.99*** for arylamidase, 0.81*** to 0.97*** for -asparaginase, 0.62*** to 0.97*** for -glutaminase, 0.61*** to 0.98*** for amidase, 0.66** to 0.96*** for urease, and 0.80*** to 0.99*** for -aspartase. The Δactivity/ΔpH values were calculated to assess the sensitivity of the enzymes to changes in soil pH. The order of the sensitivity of enzymes was as follows: -

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-aspartase. The enzyme activities were greater in the samples of the 0–5 cm depth than those of the 0–15 cm samples under no-till treatment. Most of the enzyme activities were significantly (P<0.001) and positively correlated with microbial biomass C (Cmic) and N (Nmic). Lime application significantly affected the specific activities of the six enzymes studied. Results showed that soil management practices, including liming and type of tillage significantly affect soil biological and biochemical properties, which may lead to changes in nitrogen cycling, including N mineralization in soils.  相似文献   

11.
Field experiments were conducted to study soil properties, soil enzymes activities, water use efficiency (WUE) and crop productivity after six years of soya bean straw mulching in the semi‐arid conditions of China. The experiment included four treatments: CK (Control), N (240 kg N ha‐1), H (soya bean straw mulching at half rate 700 kg ha‐1 with 240 kg N ha‐1) and F (soya bean straw mulching at full rate 1,400 kg ha‐1 with 240 kg N ha‐1). Soil organic carbon (SOC), soil labile organic carbon (LOC), soil available N (AN), available P (AP) and enzyme activities were analysed after wheat harvesting in 2016 and 2017. Results show that straw amounts had positive effects on the soil fertility indices being higher for treatment F. The SOC, LOC, AN, AP and enzyme activities (i.e. saccharase, urease and alkaline phosphatase) were in the order of F > H > N > CK. High wheat grain yield and WUE were observed for F treatment. A total of six years mulching along with 240 kg ha‐1 nitrogen fertilizer application is sufficient for wheat yield stability and improving soil properties except urease activities in the semi‐arid condition of China. However, the straw mulching amount should be further studied with minimum nitrogen fertilizer for an environment‐friendly and effective approach for improving the soil biological properties with adequate crop production on a sustainable basis in the semi‐arid region of China.  相似文献   

12.
Summary Field studies to determine the effect of different rates of fertilization on emission of nitrous oxide (N2O) from soil fertilized with anhydrous ammonia showed that the fertilizer-induced emission of N2O-N in 116 days increased from 1.22 to 4.09 kg ha–1 as the rate of anhydrous ammonia N application was increased from 75 to 450 kg ha–1. When expressed as a percentage of the N applied, the fertilizer-induced emission of N2O-N in 116 days decreased from 1.6% to 0.9% as the rate of fertilizer N application was increased from 75 to 450 kg N ha–1. The data obtained showed that a 100% increase in the rate of application of anhydrous ammonia led to about a 60% increase in the fertilizer-induced emission of N2O.Field studies to determine the effect of depth of fertilizer injection on emission of N2O from soil fertilized with anhydrous ammonia showed that the emission of N2O-N in 156 days induced by injection of 112 kg anhydrous ammonia N ha–1 at a depth of 30 cm was 107% and 21 % greater than those induced by injection of the same amount of N at depths of 10 cm and 20 cm, respectively. The effect of depth of application of anhydrous ammonia on emission of N2O was less when this fertilizer was applied at a rate of 225 kg N ha–1.  相似文献   

13.
Summary The influence of the partial pressure of oxygen on denitrification and aerobic respiration was investigated at defined P02 values in a mull rendzina soil. The highest denitrification and respiration rates obtained in remoistened, glucose- and nitrate-amended soil were 43 1 N20 h–1g–1 soil and 130 1 O2 h–1g–1 soil, respectively. At -55 kPa matric water potential, corresponding to 40% water saturation, N20 was produced only below P02 40 hPa. The K m, for O2 was 3.0 x 10–6 M. Formation of N2O and consumption of O2 occurred simultaneously with half maximum rates at P02 6.7–13.3 hPa. Nitrite accumulated in soil below 40 hPa and increased with decreasing pO2. The upper threshold for N20 formation in amended soil was P02 33–40 hPa (39-47 M O2).  相似文献   

14.
The contribution of organic resources to the restoration of soil fertility in smallholder farming systems in East Africa is being tested as an alternative to costly fertilizers. Organic inputs are expected to have advantages over fertilizers by affecting many biochemical properties controlling nutrient cycling. Our study examined changes in soil C and N, C and N mineralization, microbial biomass C (MBC) and N (MBN), and particulate organic matter (POM) in a P-limiting soil in western Kenya after applications of organic residues and fertilizers to overcome P limitation to crops. Leaf biomass from six different tree (shrub) species was incorporated into the soil at 5 Mg ha–1 for five consecutive maize growing seasons, over 2.5 years. Triple superphosphate was applied separately at 0, 10, 25, 50, and 150 kg P ha–1 in combination with 120 kg N ha–1 as urea. Soil inorganic N, soil organic C, mineralizable N, and total C in all POM fractions and total N in the 53- to 250-m POM fraction increased following addition of all organic residues compared to the control. Whether there was an advantage of organic residue incorporation over inorganic fertilizer use depended on the soil parameter studied, the organic residue and the rate of fertilization. Most differences were found in N mineralization where 14.4–21.6 mg N kg–1 was mineralized in fertilizer treatments compared to 25.2–30.5 mg N kg–1 in organic residue treatments. C and N mineralization and the 53- to 250-m POM fractions were the most sensitive parameters, correlating with most of the studied parameters. Organic residues can contribute to improved soil nutrient cycling while the magnitude of their contribution depends on the biochemical properties of the residues.  相似文献   

15.
Nitrogen (N) surpluses from fertilizer application can cause major environmental harm including pollution of surface water, groundwater, and air. To assess such negative externalities, N balances are a complex but useful tool to predict surpluses and to measure effects of nutrient optimization strategies in agriculture. The Yaqui Valley in north‐western Mexico is representative for thousands of square kilometres of intensive, irrigated wheat production under arid conditions worldwide and has been targeted for conservation agriculture in recent years. For these cropping systems, detailed N balances are scarce and often incomplete. To help fill this knowledge gap, data from a long‐term experiment were collected in 2013/14 on a Vertisol to examine the impact of three tillage‐straw management practices (CTB: conventionally tilled beds; PB‐straw: permanent raised beds with residue retention; PB‐burn: permanent raised beds with residue burning) on N dynamics. Tillage had significant effects on soil NO3‐N, NH4‐N, and total N contents across the cropping period. Soil total N content was at all sampling depths lowest in CTB. Soil NO3‐N in the 0–90 cm profile was highest in PB‐burn over the cropping period and ranged from 77 kg ha?1 in the bed before pre‐planting fertilizer application up to 269 kg ha?1 in the furrow after the second fertilizer application. Annual simple N balances were +59 kg N ha?1 in CTB, +39 kg N ha–1 in PB‐straw, and +46 kg N ha?1 in PB‐burn. Residual mineral soil N was significantly affected by tillage‐straw management and lowest for PB‐straw (+205 kg N ha?1) and highest for CTB, and for PB‐burn (+283 kg N ha?1 each) in the 0–90 cm soil profile. Soil NO3‐N moved out of the effective wheat root zone, as indicated by the high residual NO3‐N content at 30–90 cm depth, which is an important pathway of N leaching. Quantifiable N losses through leaching and volatilization averaged 100 kg N ha?1. Our findings suggest that there is potential for substantial reductions in N inputs in all tillage‐straw systems to decrease N losses and to reduce mineral residual soil N, but care should be taken to avoid reducing grain protein content, which in PB straw was already below the quality standard. A knowledge transfer of the European “Nmin” concept is advisable in this region to regulate N fertilizer over‐application.  相似文献   

16.
Summary Studies of the effects of different forms of N on urease production in soils amended with organic C showed that although microbial activity, as measured by CO2 production, was stimulated by the addition of NH4 + or NO3 - to C-amended soils (200 mol glucose-C g–1 soil), urease production was repressed by these forms of N. The addition of L-methionine sulfoximine, an inhibitor of inorganic N assimilation by microorganisms, relieved the NH4 + and NO3 - repression of urease production in C-amended soil. The addition of sodium chlorate, an inhibitor of NO3 - reduction to NH4 + by microorganisms, relieved the NO3 - repression of urease production, but did not eliminate the repression associated with NH4 +. These observations indicate that microbial production of urease in C-amended soils is not directly repressed by NH4 + or NO3 -, but by products formed by microbial assimilation of these forms of N. This conclusion is supported by our finding that the biologically active L-isomers of alanine, arginine, asparagine, aspartate, and glutamine, repressed urease production in C-amended soil, whereas the D-isomers of these amino acids had little or no influence on urease production. This work suggests that urease synthesis by soil microorganisms is controlled by the global N regulon.  相似文献   

17.
With annual incorporation of straw, soil N mineralization is expected to increase whereby requirements for fertilizer N inputs may be reduced. Samples of whole soil, clay (< 2 μm), silt (2–20 μm) and sand (20–2000 μm) sized organomineral separates from three soils with annual additions of straw ranging from 0 to 12 t ha–1 were leached after 0, 1, 2, 4, 8, 12 and 16 weeks of incubation at 20°C, to determine the content of NH4 + NO3. A three-pool model using first order kinetics and fixed rate constants (N1, k1 = 0.231 day–1; N2, k2 = 0.00693 day–1; N3, k3 = 0) was fitted to the mineralization data. The mineralizability of whole soil N (mg N g–1 N) differed among soil types. Straw generally increased the fast N1 and the passive N3 pool while the medium-term N2 pool was reduced in size. The N1, N2 and N3 averaged 0.8, 2.6 and 96.6% of the whole soil N, respectively. The N mineralizability increased in the order: sand < silt < clay. The lability of N in a given size separate was almost similar across soil types and straw managements. The active N pools (N1 + N2) averaged 7.1% of the clay N and 2.2% of the silt N. The main difference was related to the N2 pool, which accounted for 5.5% in clay and 1.2% in silt. Mineral N produced during incubation ranged from 63 to 105 kg N ha–1. Effects of straw disposal were small (< 11 kg N ha–1). Maximum response was at 4 t straw ha–1; adding more straw diminished mineralization of N. Long-term annual incorporation of cereal straw contributes mainly soil N with a slow turnover.  相似文献   

18.
Summary Field studies of the effects of different N fertilizers on emission of nitrous oxide (N20) from three Iowa soils showed that the N2O emissions induced by application of 180 kg ha–1 fertilizer N as anhydrous ammonia greatly exceeded those induced by application of the same amount of fertilizer N as aqueous ammonia or urea. On average, the emission of N2O-N induced by anhydrous ammonia was more than 13 times that induced by aqueous ammonia or urea and represented 1.2% of the anhydrous ammonia N applied. Experiments with one soil showed that the N2O emission induced by anhydrous ammonia was more than 17 times that induced by the same amount of N as calcium nitrate. These findings confirm indications from previous work that anhydrous ammonia has a much greater effect on emission of N2O from soils than do other commonly used N fertilizers and merits special attention in research relating to the potential adverse climatic effect of N fertilization of soils.Laboratory studies of the effect of different amounts of NH4OH on emission of N2O from Webster soil showed that the emission of N2O-N induced by addition of 100 g NH4OH-N g–1 soil represented only 0.18% of the N applied, whereas the emissions induced by additions of 500 and 1 000 g NH4OH-N g–1 soil represented 1.15% and 1.19%, respectively, of the N applied. This suggests that the exceptionally large emissions of N2O induced by anhydrous ammonia fertilization are due, at least in part, to the fact that the customary method of applying this fertilizer by injection into soil produces highly alkaline soil zones of high ammonium-N concentration that do not occur when urea or aqueous ammonia fertilizers are broadcast and incorporated into soil.  相似文献   

19.
In the central highlands of Mexico, mesquite (Prosopis laevigata) and huisache (Acacia schaffneri), N2-fixing trees or shrubs, dominate the vegetation and are currently used in a reforestation program to prevent erosion. We investigated how natural vegetation or cultivation of soil affected oxidation of CH4, and production of N2O. Soil was sampled under the canopy of mesquite (MES treatment) and huisache trees (HUI treatment), outside their canopy (OUT treatment) and from fields cultivated with maize (ARA treatment) at three different sites while production of CO2, and dynamics of CH4, N2O and inorganic N (NH4+, and NO3–) were monitored in an aerobic incubation. The production of CO2 was 2.3 times higher and significantly greater in the OUT treatment, 3.0 times higher in the MES treatment and 4.0 times higher in the HUI treatment compared to the ARA treatment. There was no significant difference in oxidation of CH4 between the treatments, which ranged from 0.019 g CH4–C kg–1 day–1 for the HUI treatment to 0.033 CH4–C kg–1 day–1 for the MES treatment. The production of N2O was 30 g N2O–N kg–1 day–1 in the MES treatment and >8 times higher compared to the other treatments. The average concentration of NO3– was 2 times higher and significantly greater in the MES treatment than in the HUI treatment, 3 times greater than in the OUT treatment and 10 times greater than in the ARA treatment. It was found that cultivation of soil decreased soil organic matter content, C and N mineralization, but not oxidation of CH4 or production of N2O.  相似文献   

20.
Summary The influence of soil moisture on denitrification and aerobic respiration was studied in a mull rendzina soil. N2O formation did not occur below –30 kPa matric water potential (m), above 0.28 air-filled porosity (a) and below 0.55 fractional water saturation (v/PV volumetric water content/total pore volume). Half maximum rates of N2O production and O2 consumption were obtained between m = –1.2 and –12 kPa,a = 0.05 and 0.23, and v/PV = 0.63 and 0.92. No oxygen consumption was measured at v/PC 1.17. O2 uptake and denitrification occurred simultaneously arounda = 0.10 (at m = –10 kPa and v/PV = 0.81) at mean rates of 3.5 µl O2 and 0.3 µl N2 h–1g–1 soil. Undisturbed, field-moist soil saturated with nitrate solution showed constant consumption and production rates, respectively, of 0.6 µl O and 0.22 µl N2O h–1g–1 soil, whereas the rates of air-dried remoistened soil were at least 10 times these values. The highest rates obtained in remoistened soil amended with glucose and nitrate were 130 µl O2 and 27 µl N2O h–1g–1 soil.  相似文献   

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