Surface charge, secondary adsorption- desorption and form distribution of Cu2+ and Zn2+ in Ultisols and Alfisols having adsorbed phosphate were studied by potentiometric titration, adsorption equilibrium and sequentia...Surface charge, secondary adsorption- desorption and form distribution of Cu2+ and Zn2+ in Ultisols and Alfisols having adsorbed phosphate were studied by potentiometric titration, adsorption equilibrium and sequential extraction method, respectively. The soil surface negative charges increased whereas the amount of positive charges decreased with increase of P adsorbed. The soil secondary adsorption capacity for Cu2+ and Zn2+ was positively significantly correlated with the amount of P adsorbed by the soils, which could be described by the Langmuir equation. The amounts of Cu2+ and Zn2+ desorption from soils were decreased after P adsorption by the soils and the relationship between them was linear. After the soils adsorbed P, form distribution of Cu2+ and Zn2+ in soils changed remarforbly.展开更多
The distribution of actinomycetes in oil contaminated sandy loam ultisols of the Niger Delta region of Nigeria was studied to aid in understanding the effect of hydrocarbons on indigenous microbial population in trop...The distribution of actinomycetes in oil contaminated sandy loam ultisols of the Niger Delta region of Nigeria was studied to aid in understanding the effect of hydrocarbons on indigenous microbial population in tropical soils. The average total counts of actinomycetes in all the oil samples analysed was 10 3 cfu/g. Higher counts of actinomycetes were observed during the dry season than during the wet season. The counts of hydrocarbonoclastic actinomycetes correlated positively with the total count of actinomycetes. The actinomycetes were generally restricted to the top soil(0—10 cm soil depth) although a seemingly deeper(down to 40 cm soil depth) distribution was noticed in the dry season. The isolates included oil degrading species of Actinoplanes, Norcadia, Streptomyces and Streptosporangium. Their high oil utilization ability indicates their positive potential and role in the bioremediation of oil spilled soils.展开更多
Agricultural liming contributes significantly to atmospheric CO2 emission from soils but data on magnitude of lime- contributed CO2 in a wide range of acid soils are still few. Data on lime-contributed CO2 and SOC tur...Agricultural liming contributes significantly to atmospheric CO2 emission from soils but data on magnitude of lime- contributed CO2 in a wide range of acid soils are still few. Data on lime-contributed CO2 and SOC turnover for global acid soils are needed to estimate the potential contribution of agricultural liming to atmospheric CO2. Using Ca13CO3 (13C 99%) as lime and tracer, here we separated lime-contributed and SOC-originated CO2 evolution in an acidic Kuroboku Andisol from Tanashi, Tokyo Prefecture (35°44′ N, 139°32′ E) and Kunigami Mahji Ultisol of Nakijin, Okinawa Prefecture, Japan (26°38′ N, 127°58′ E). On the average, lime-CO2 was 76.84% (Kuroboku Andisol) and 66.36% (Kunigami Mahji Ultisol) of overall CO2 emission after 36 days. There was increased SOC turnover in all limed soils, confirming priming effect (PE) of liming. The calculated PE of lime (Kuroboku Andisol, 51.97% - 114.95%;Kunigami Mahji Ultisol, 10.13% - 35.61%) was entirely 12C turnover of stable soil organic carbon (SOC) since SMBC, a labile SOC pool, was suppressed by liming in our experiment. Our results confirmed that mineralization of lime-carbonates is the major source of CO2 emission from acid soils during agricultural liming. Liming can influence the size of CO2 evolution from agricultural ecosystems considering global extent of acid soils and current volume of lime utilization. We propose the inclusion of liming in simulating carbon dynamics in agricultural ecosystems.展开更多
Field experiments were conducted to evaluate the effects of integrated use of agricultural wastes and a compound mineral fertilizer on the fluxes of soil nutrients. Agricultural wastes applied were: livestock manure (...Field experiments were conducted to evaluate the effects of integrated use of agricultural wastes and a compound mineral fertilizer on the fluxes of soil nutrients. Agricultural wastes applied were: livestock manure (cow dung and poultry litter), shoots of Chromolaena odorata and Parkia biglosa (locust bean), Neem (Azadiracta inidca) seed powder/cake and melon shell. These materials were applied at zero (control), 100% (i.e. organic wastes applied at the recommended rates of 10 t/ha) and 70% of their recommended rates plus 30% of the recommended rate of the mineral fertilizer (NPK: 400 Kg/ha). Average values of soil organic carbon (SOC) were 1.94, 1.68, 1.36 and 1.38 for organic wastes alone, organic waste plus mineral fertilizer (NPK) and unamended control. Mineral N ( N plus N) pools were relatively high at 30 and 60 days after planting, and were significantly higher for organically amended soils (550) and wastes applied at reduced rates combined with 120 kg/ha mineral NPK (470) than the unamended control (277). Across sampling dates, SOC values were the highest in poultry manure and neem seed cake. The values of N plus exchangeable N which constitutes plant available nitrogen (PAN) were significantly higher for organically amended soils and wastes applied at reduced rates combined with 120 kg/ha mineral NPK than the unamended control. The % C microbial to C organic ratio was higher in organically amended soils. The temporal profile of SOC, NH4-N and NO3-N showed declines with time, the relationship was linear for SOC (Y = 0.18x + 1.07;R2 = 0.34), by a power function for N (Y = 48.084x-1.79;R2 = 0.91) and a polynomial function for NH4-N (Y = -28.75x + 130.65x - 57.25;R2 = 0.61). The time dynamics of microbial population (cfu) followed trends obtained for SOC.展开更多
An experiment was conducted to determine the effects of application of various levels of GML （ground magnesium limestone） for sweet corn production on two Ultisols, viz.： Bungor and Rengam series soil. The treatmen...An experiment was conducted to determine the effects of application of various levels of GML （ground magnesium limestone） for sweet corn production on two Ultisols, viz.： Bungor and Rengam series soil. The treatments consisted of six levels of GML 0, 0.5, 1.0,2.0,4.0 and 8.0 Mg·ML·ha^-1 incorporated into the top 15 cm, a control which received no GML and no fertilizer. Two crops of sweet corn were planted with a crop of groundnut in a sequence of corn-groundnut-corn. Results indicated that application of 4.0 Mg·GML·ha^-1 and 2.0 Mg·GML·ha^-1 on Bungor and Rengan series soil respectively gave the highest yields in terms of saleable cob number. Soil analysis showed that application of 4.0 and 2.0 Mg·ha^-1 to Bungor and Rengam series soils respectively reduced Al saturation in both soils to 2.0% and increased soil pH to 5.7 and 4.8, respectively.展开更多
The effects of crude oil on soil nitrogen dynamics and cycling in plant-soil ecosystems and its effect on the growth of legumes (Calopogonium mucunoides, Centrosema pubescens and Pueraria phaseolodes) grown in wetland...The effects of crude oil on soil nitrogen dynamics and cycling in plant-soil ecosystems and its effect on the growth of legumes (Calopogonium mucunoides, Centrosema pubescens and Pueraria phaseolodes) grown in wetland ultisols were investigated. The test plants species were grown on wetland soil simulated with 0.35, 10.8, 20.5, and 50 g.kg<sup>-1</sup>levels of crude oil contamination. The results showed time and species dependent variation in mineral N content of the treated soils. The variation is indicative of significant interaction between the hydrocarbon content and plant species. Variations in microbial N and microbial C were similar and correlation between the microbial N and the total C (Organic matter (C) + hydrocarbon content (C)) in soil was highly significant (r = 0.96, n = 12, P ≤ 0.01). The presence of hydrocarbon contaminant widens the C:N ratio in soil and leads to more available N being immobilized by soil microorganisms, which reduces available N for plant uptake. This result implies that crude oil contamination significantly reduces N uptake by plants but increases N accumulation in soil microbial biomass. The findings show that N dynamics, transformation and cycling in soil are influenced by hydrocarbons and that the interactions between hydrocarbon content and plant species in contaminated soil are remarkable. The use of plant Centrosema pubescens with poultry manure or NPK fertilizer for bioremediation is more effective than that of Calopogonium mucunoides and Pueraria phaseoloides. However, the selective attributes of the various treatment approaches adopted here may be exploited for enhanced remediation of contaminated wetlands in the Niger Delta region of Nigeria. 展开更多
This study aims to determine the ability of CM(Cow Manure)combined with RHA(Rice Husk Ash)to provide a significant effect on the growth and production of soybean planted in an ultisol.It was conducted in a pot experim...This study aims to determine the ability of CM(Cow Manure)combined with RHA(Rice Husk Ash)to provide a significant effect on the growth and production of soybean planted in an ultisol.It was conducted in a pot experiment at the Experimental Site of the Faculty of Agriculture,Sriwijaya University,Indralaya,Indonesia between September 2019 and February 2020 using completely randomized design factorial with two factors which were two rate levels of RHA at 3.75 and 7.5 tons·ha^(-1) and three rate levels of CM at 0,10,and 20 tons·ha^(-1).It is important to note that each combination was repeated three times,thereby,leading to a total of 18 pots.The variables studied were plant growth and yield which are represented by plant height,the total number of pods,number of filled pods,seed weight per plant,and soybean produced.The results showed that CM combined with RHA was effective in increasing nutrient availability and reducing soil acidity.It was discovered that CM had a significant effect on soil pH,plant height,the total number of pods,number of filled pods,seed weight per plant,and soybean produced while RHA did not have any significant difference on all the variables observed.However,the combination of 10 tons·ha-1 CM with 3.75 tons·ha-1 RHA was observed to be the best combination treatment to increase the growth and production of soybean in ultisol as indicated by its ability to produce 2.58 tons·ha^(-1) soybean.展开更多
Assessment of variability and understanding of traits relationship in eggplant species are vital pre-requisite for formulating an effective breeding programme.We studied 23 genotypes of eggplants in a coarse-textured ...Assessment of variability and understanding of traits relationship in eggplant species are vital pre-requisite for formulating an effective breeding programme.We studied 23 genotypes of eggplants in a coarse-textured Ultisol using a randomized complete block design experiment with three replications.Data were collected on number of branches,number of leaves,number of nodes and internodes,stem diameter,plant height,floral and yield traits.Results revealed significant(p=0.05)variation in the flowering and fruiting pattern of the genotypes.‘Yalo x K3BC2P10 gave the highest individual fruit weight of 80.8 g.Individual fruit weight contributed the highest direct positive effect on the fruit yield.It acted majorly through plant height,number of branches,number of leaves and number of days to first fruit set as revealed in the path coefficient result.Individual fruit weight,number of fruits per plant,plant height,number of days to 50%flowering,number of branches,numbers of days to first flowering and 50%fruit set had positive direct effect on yield.These traits should be considered in developing high yielding eggplant breeding programme.展开更多
Vineyard management practices to enhance soil conservation principally focus on increasing carbon(C)input,whereas mitigating impacts of disturbance through reduced tillage has been rarely considered.Furthermore,inform...Vineyard management practices to enhance soil conservation principally focus on increasing carbon(C)input,whereas mitigating impacts of disturbance through reduced tillage has been rarely considered.Furthermore,information is lacking on the effects of soil management practices adopted in the under-vine zone on soil conservation.In this work,we evaluated the long-term effects(22 years)of alley with a sown cover crop and no-tillage(S+NT),alley with a sown cover crop and tillage(S+T),and under-vine zone with no vegetation and tillage(UV)on soil organic matter(SOM),microbial activity,aggregate stability,and their mutual interactions in a California vineyard in USA.Vegetation biomass,microbial biomass and activity,organic C and nitrogen(N)pools,and SOM size fractionation and aggregate stability were analysed.Soil characteristics only partially reflected the differences in vegetation biomass input.Organic C and N pools and microbial biomass/activity in S+NT were higher than those in S+T,while the values in UV were intermediate between the other two treatments.Furthermore,S+NT also exhibited higher particulate organic matter C in soil.No differences were found in POM C between S+T and UV,but the POM fraction in S+T was characterized by fresher material.Aggregate stability was decreased in the order:S+NT>UV>S+T.Tillage,even if shallow and performed infrequently,had a negative effect on organic C and N pools and aggregate stability.Consequently,the combination of a sown cover crop and reduced tillage still limited SOM accumulation and reduced aggregate stability in the surface soil layer of vineyards,suggesting relatively lower resistance of soils to erosion compared to no-till systems.展开更多
Effects of citrate and tartrate on phosphate adsorption and desorption from kaolinite, goethite, amorphous Al-oxide and Ultisol were studied. P adsorption was significantly decreased as the concentration of the organi...Effects of citrate and tartrate on phosphate adsorption and desorption from kaolinite, goethite, amorphous Al-oxide and Ultisol were studied. P adsorption was significantly decreased as the concentration of the organic anions increased from 10-5 to 10-1 M. At 0.1 M and pH 7.0, tartrate decreased P adsorption by 27.6% - 50.6% and citrate by 37.9 - 80.4%, depending on the kinds of adsorbent. Little Al and/ or Fe were detected in the equilibrium solutions, even at the highest concentration of the organic anions. Effects of the organic anions on phosphate adsorption follow essentially the competitive adsorption mechanism.The selectivity coefficients for competitive adsorption can be used to compare the effectiveness of different organic anions in reducing P adsorption under given conditions.Phosphate desorption was increased by 3 to 100 times in the presence of 0.001 M citrate or tartrate compared to that in 0.02 M KC1 solution alone. However, for all the soil and clay minerals studied the amount of P desorbed by citrate or tartrate was generally lower than or close to that of isotopically exchangeable P. The effect of organic anions on phosphate desorption arises primarily from ligand exchange.展开更多
At the peak of the Vietnam War, the network of tunnels in the Iron Triangle and Cu Chi linked Viet Cong (VC) support bases over a distance of some 250 km, from the Ho Chi Minh Trail and Cambodian border to the outskir...At the peak of the Vietnam War, the network of tunnels in the Iron Triangle and Cu Chi linked Viet Cong (VC) support bases over a distance of some 250 km, from the Ho Chi Minh Trail and Cambodian border to the outskirts Saigon. In the early 1960s, the United States escalated its military presence in Vietnam in support of a non-Communist regime in South Vietnam. The North Vietnamese and VC troops gradually expanded the tunnels. Tunnels frequently were dug by hand in Old Alluvium terraces, and only a short distance at a time. Four major efforts were made by the US Military to locate and destroy these tunnels. These included Operation Crimp, a search and destroy mission which began in 1966 and a geological and soil survey approach was used to detect VC tunnels. Later in 1967, General William Westmoreland tried launching a larger assault on Cu Chi and the Iron Triangle areas. The operation called Operation Cedar Falls was an expanded version of Operation Crimp. Finally in 1969, B-52s started carpet bombing the Cu Chi and Iron Triangle areas and destroyed many of the tunnels. However, not before the tunnels had proven very effective in 1960s at hiding and protecting the VC during US occupation of the area. The nature and properties of the Old Alluvium soils were key to the soil tunnels being so resilient. Soils located in Old Alluvium terraces had high levels of clay and iron. Iron (Fe) leached from the upper soil layers (0 to 1.5 m) and accumulated in the lower layers (1.5 to 20 m) and became a cement-like binding agent. When dried the soil layers took on properties close to concrete, and were resistant to ever becoming soft and moist again especially around the aerated tunnel walls. The tunnels were dug in the monsoon season when the upper layers of soil were soft and moist but not in dry season. The soils were highly stable without any lining or support. After drying out, the soil materials surrounding the tunnel turned into concrete like material that could withstand adjacent explosive blasts.展开更多
基金Project (No. 49871043) supported by the National Natural Science Foundation of China.
文摘Surface charge, secondary adsorption- desorption and form distribution of Cu2+ and Zn2+ in Ultisols and Alfisols having adsorbed phosphate were studied by potentiometric titration, adsorption equilibrium and sequential extraction method, respectively. The soil surface negative charges increased whereas the amount of positive charges decreased with increase of P adsorbed. The soil secondary adsorption capacity for Cu2+ and Zn2+ was positively significantly correlated with the amount of P adsorbed by the soils, which could be described by the Langmuir equation. The amounts of Cu2+ and Zn2+ desorption from soils were decreased after P adsorption by the soils and the relationship between them was linear. After the soils adsorbed P, form distribution of Cu2+ and Zn2+ in soils changed remarforbly.
文摘The distribution of actinomycetes in oil contaminated sandy loam ultisols of the Niger Delta region of Nigeria was studied to aid in understanding the effect of hydrocarbons on indigenous microbial population in tropical soils. The average total counts of actinomycetes in all the oil samples analysed was 10 3 cfu/g. Higher counts of actinomycetes were observed during the dry season than during the wet season. The counts of hydrocarbonoclastic actinomycetes correlated positively with the total count of actinomycetes. The actinomycetes were generally restricted to the top soil(0—10 cm soil depth) although a seemingly deeper(down to 40 cm soil depth) distribution was noticed in the dry season. The isolates included oil degrading species of Actinoplanes, Norcadia, Streptomyces and Streptosporangium. Their high oil utilization ability indicates their positive potential and role in the bioremediation of oil spilled soils.
文摘Agricultural liming contributes significantly to atmospheric CO2 emission from soils but data on magnitude of lime- contributed CO2 in a wide range of acid soils are still few. Data on lime-contributed CO2 and SOC turnover for global acid soils are needed to estimate the potential contribution of agricultural liming to atmospheric CO2. Using Ca13CO3 (13C 99%) as lime and tracer, here we separated lime-contributed and SOC-originated CO2 evolution in an acidic Kuroboku Andisol from Tanashi, Tokyo Prefecture (35°44′ N, 139°32′ E) and Kunigami Mahji Ultisol of Nakijin, Okinawa Prefecture, Japan (26°38′ N, 127°58′ E). On the average, lime-CO2 was 76.84% (Kuroboku Andisol) and 66.36% (Kunigami Mahji Ultisol) of overall CO2 emission after 36 days. There was increased SOC turnover in all limed soils, confirming priming effect (PE) of liming. The calculated PE of lime (Kuroboku Andisol, 51.97% - 114.95%;Kunigami Mahji Ultisol, 10.13% - 35.61%) was entirely 12C turnover of stable soil organic carbon (SOC) since SMBC, a labile SOC pool, was suppressed by liming in our experiment. Our results confirmed that mineralization of lime-carbonates is the major source of CO2 emission from acid soils during agricultural liming. Liming can influence the size of CO2 evolution from agricultural ecosystems considering global extent of acid soils and current volume of lime utilization. We propose the inclusion of liming in simulating carbon dynamics in agricultural ecosystems.
文摘Field experiments were conducted to evaluate the effects of integrated use of agricultural wastes and a compound mineral fertilizer on the fluxes of soil nutrients. Agricultural wastes applied were: livestock manure (cow dung and poultry litter), shoots of Chromolaena odorata and Parkia biglosa (locust bean), Neem (Azadiracta inidca) seed powder/cake and melon shell. These materials were applied at zero (control), 100% (i.e. organic wastes applied at the recommended rates of 10 t/ha) and 70% of their recommended rates plus 30% of the recommended rate of the mineral fertilizer (NPK: 400 Kg/ha). Average values of soil organic carbon (SOC) were 1.94, 1.68, 1.36 and 1.38 for organic wastes alone, organic waste plus mineral fertilizer (NPK) and unamended control. Mineral N ( N plus N) pools were relatively high at 30 and 60 days after planting, and were significantly higher for organically amended soils (550) and wastes applied at reduced rates combined with 120 kg/ha mineral NPK (470) than the unamended control (277). Across sampling dates, SOC values were the highest in poultry manure and neem seed cake. The values of N plus exchangeable N which constitutes plant available nitrogen (PAN) were significantly higher for organically amended soils and wastes applied at reduced rates combined with 120 kg/ha mineral NPK than the unamended control. The % C microbial to C organic ratio was higher in organically amended soils. The temporal profile of SOC, NH4-N and NO3-N showed declines with time, the relationship was linear for SOC (Y = 0.18x + 1.07;R2 = 0.34), by a power function for N (Y = 48.084x-1.79;R2 = 0.91) and a polynomial function for NH4-N (Y = -28.75x + 130.65x - 57.25;R2 = 0.61). The time dynamics of microbial population (cfu) followed trends obtained for SOC.
文摘An experiment was conducted to determine the effects of application of various levels of GML （ground magnesium limestone） for sweet corn production on two Ultisols, viz.： Bungor and Rengam series soil. The treatments consisted of six levels of GML 0, 0.5, 1.0,2.0,4.0 and 8.0 Mg·ML·ha^-1 incorporated into the top 15 cm, a control which received no GML and no fertilizer. Two crops of sweet corn were planted with a crop of groundnut in a sequence of corn-groundnut-corn. Results indicated that application of 4.0 Mg·GML·ha^-1 and 2.0 Mg·GML·ha^-1 on Bungor and Rengan series soil respectively gave the highest yields in terms of saleable cob number. Soil analysis showed that application of 4.0 and 2.0 Mg·ha^-1 to Bungor and Rengam series soils respectively reduced Al saturation in both soils to 2.0% and increased soil pH to 5.7 and 4.8, respectively.
文摘The effects of crude oil on soil nitrogen dynamics and cycling in plant-soil ecosystems and its effect on the growth of legumes (Calopogonium mucunoides, Centrosema pubescens and Pueraria phaseolodes) grown in wetland ultisols were investigated. The test plants species were grown on wetland soil simulated with 0.35, 10.8, 20.5, and 50 g.kg<sup>-1</sup>levels of crude oil contamination. The results showed time and species dependent variation in mineral N content of the treated soils. The variation is indicative of significant interaction between the hydrocarbon content and plant species. Variations in microbial N and microbial C were similar and correlation between the microbial N and the total C (Organic matter (C) + hydrocarbon content (C)) in soil was highly significant (r = 0.96, n = 12, P ≤ 0.01). The presence of hydrocarbon contaminant widens the C:N ratio in soil and leads to more available N being immobilized by soil microorganisms, which reduces available N for plant uptake. This result implies that crude oil contamination significantly reduces N uptake by plants but increases N accumulation in soil microbial biomass. The findings show that N dynamics, transformation and cycling in soil are influenced by hydrocarbons and that the interactions between hydrocarbon content and plant species in contaminated soil are remarkable. The use of plant Centrosema pubescens with poultry manure or NPK fertilizer for bioremediation is more effective than that of Calopogonium mucunoides and Pueraria phaseoloides. However, the selective attributes of the various treatment approaches adopted here may be exploited for enhanced remediation of contaminated wetlands in the Niger Delta region of Nigeria.
文摘This study aims to determine the ability of CM(Cow Manure)combined with RHA(Rice Husk Ash)to provide a significant effect on the growth and production of soybean planted in an ultisol.It was conducted in a pot experiment at the Experimental Site of the Faculty of Agriculture,Sriwijaya University,Indralaya,Indonesia between September 2019 and February 2020 using completely randomized design factorial with two factors which were two rate levels of RHA at 3.75 and 7.5 tons·ha^(-1) and three rate levels of CM at 0,10,and 20 tons·ha^(-1).It is important to note that each combination was repeated three times,thereby,leading to a total of 18 pots.The variables studied were plant growth and yield which are represented by plant height,the total number of pods,number of filled pods,seed weight per plant,and soybean produced.The results showed that CM combined with RHA was effective in increasing nutrient availability and reducing soil acidity.It was discovered that CM had a significant effect on soil pH,plant height,the total number of pods,number of filled pods,seed weight per plant,and soybean produced while RHA did not have any significant difference on all the variables observed.However,the combination of 10 tons·ha-1 CM with 3.75 tons·ha-1 RHA was observed to be the best combination treatment to increase the growth and production of soybean in ultisol as indicated by its ability to produce 2.58 tons·ha^(-1) soybean.
文摘Assessment of variability and understanding of traits relationship in eggplant species are vital pre-requisite for formulating an effective breeding programme.We studied 23 genotypes of eggplants in a coarse-textured Ultisol using a randomized complete block design experiment with three replications.Data were collected on number of branches,number of leaves,number of nodes and internodes,stem diameter,plant height,floral and yield traits.Results revealed significant(p=0.05)variation in the flowering and fruiting pattern of the genotypes.‘Yalo x K3BC2P10 gave the highest individual fruit weight of 80.8 g.Individual fruit weight contributed the highest direct positive effect on the fruit yield.It acted majorly through plant height,number of branches,number of leaves and number of days to first fruit set as revealed in the path coefficient result.Individual fruit weight,number of fruits per plant,plant height,number of days to 50%flowering,number of branches,numbers of days to first flowering and 50%fruit set had positive direct effect on yield.These traits should be considered in developing high yielding eggplant breeding programme.
文摘土壤含水量和氮素水平是调控氨氧化微生物和硝化速率的重要因素。本研究以旱地红壤为对象,设置3个土壤含水量(40%WFPS、60%WFPS、80%WFPS,WFPS为土壤孔隙含水量)×4个氮添加水平(0、25、50和100 mg N·kg^(-1)),进行微宇宙培养试验,研究含水量和氮添加对土壤净硝化速率和氨氧化微生物功能基因丰度的影响。结果表明:土壤净硝化速率随土壤含水量和氮添加量的增加而增加。土壤含水量增加显著提高AOA和AOB amoA基因丰度,但降低完全氨氧化菌clade A amoA基因丰度,表明土壤含水量增加不利于完全氨氧化菌clade A生长。氮添加显著提高AOA和AOB amoA基因丰度,但对完全氨氧化菌clade A amoA基因丰度无显著影响。综上,土壤含水量增加不利于旱地农田红壤完全氨氧化菌生长,但氮添加对其丰度影响不显著。
基金supported by the USDA-ARS Sustainable Viticulture Production Systems, USA (No. 2032-21220-006-00, NP305 Crop Production)
文摘Vineyard management practices to enhance soil conservation principally focus on increasing carbon(C)input,whereas mitigating impacts of disturbance through reduced tillage has been rarely considered.Furthermore,information is lacking on the effects of soil management practices adopted in the under-vine zone on soil conservation.In this work,we evaluated the long-term effects(22 years)of alley with a sown cover crop and no-tillage(S+NT),alley with a sown cover crop and tillage(S+T),and under-vine zone with no vegetation and tillage(UV)on soil organic matter(SOM),microbial activity,aggregate stability,and their mutual interactions in a California vineyard in USA.Vegetation biomass,microbial biomass and activity,organic C and nitrogen(N)pools,and SOM size fractionation and aggregate stability were analysed.Soil characteristics only partially reflected the differences in vegetation biomass input.Organic C and N pools and microbial biomass/activity in S+NT were higher than those in S+T,while the values in UV were intermediate between the other two treatments.Furthermore,S+NT also exhibited higher particulate organic matter C in soil.No differences were found in POM C between S+T and UV,but the POM fraction in S+T was characterized by fresher material.Aggregate stability was decreased in the order:S+NT>UV>S+T.Tillage,even if shallow and performed infrequently,had a negative effect on organic C and N pools and aggregate stability.Consequently,the combination of a sown cover crop and reduced tillage still limited SOM accumulation and reduced aggregate stability in the surface soil layer of vineyards,suggesting relatively lower resistance of soils to erosion compared to no-till systems.
文摘Effects of citrate and tartrate on phosphate adsorption and desorption from kaolinite, goethite, amorphous Al-oxide and Ultisol were studied. P adsorption was significantly decreased as the concentration of the organic anions increased from 10-5 to 10-1 M. At 0.1 M and pH 7.0, tartrate decreased P adsorption by 27.6% - 50.6% and citrate by 37.9 - 80.4%, depending on the kinds of adsorbent. Little Al and/ or Fe were detected in the equilibrium solutions, even at the highest concentration of the organic anions. Effects of the organic anions on phosphate adsorption follow essentially the competitive adsorption mechanism.The selectivity coefficients for competitive adsorption can be used to compare the effectiveness of different organic anions in reducing P adsorption under given conditions.Phosphate desorption was increased by 3 to 100 times in the presence of 0.001 M citrate or tartrate compared to that in 0.02 M KC1 solution alone. However, for all the soil and clay minerals studied the amount of P desorbed by citrate or tartrate was generally lower than or close to that of isotopically exchangeable P. The effect of organic anions on phosphate desorption arises primarily from ligand exchange.
文摘At the peak of the Vietnam War, the network of tunnels in the Iron Triangle and Cu Chi linked Viet Cong (VC) support bases over a distance of some 250 km, from the Ho Chi Minh Trail and Cambodian border to the outskirts Saigon. In the early 1960s, the United States escalated its military presence in Vietnam in support of a non-Communist regime in South Vietnam. The North Vietnamese and VC troops gradually expanded the tunnels. Tunnels frequently were dug by hand in Old Alluvium terraces, and only a short distance at a time. Four major efforts were made by the US Military to locate and destroy these tunnels. These included Operation Crimp, a search and destroy mission which began in 1966 and a geological and soil survey approach was used to detect VC tunnels. Later in 1967, General William Westmoreland tried launching a larger assault on Cu Chi and the Iron Triangle areas. The operation called Operation Cedar Falls was an expanded version of Operation Crimp. Finally in 1969, B-52s started carpet bombing the Cu Chi and Iron Triangle areas and destroyed many of the tunnels. However, not before the tunnels had proven very effective in 1960s at hiding and protecting the VC during US occupation of the area. The nature and properties of the Old Alluvium soils were key to the soil tunnels being so resilient. Soils located in Old Alluvium terraces had high levels of clay and iron. Iron (Fe) leached from the upper soil layers (0 to 1.5 m) and accumulated in the lower layers (1.5 to 20 m) and became a cement-like binding agent. When dried the soil layers took on properties close to concrete, and were resistant to ever becoming soft and moist again especially around the aerated tunnel walls. The tunnels were dug in the monsoon season when the upper layers of soil were soft and moist but not in dry season. The soils were highly stable without any lining or support. After drying out, the soil materials surrounding the tunnel turned into concrete like material that could withstand adjacent explosive blasts.
