The potential harm of heavy metals is a primary concern in application of sludge to the agricultural land. A pot experiment was conducted to evaluate the effect of two sludges on fractionation of Zn and Cu in soil and...The potential harm of heavy metals is a primary concern in application of sludge to the agricultural land. A pot experiment was conducted to evaluate the effect of two sludges on fractionation of Zn and Cu in soil and their phytotoxicity to pakchoi. The loamy soil was mixed with 0%, 20%, 40%, 60% and 80% （by weight） of digested sewage sludge （SS） and composted sludge （SC）. The additions of the both sludges caused a significant raise in all fractions, resulting in that exchangeable （EXCH） and organic matter （OM） became predominance for Zn and organic bound Cu occupied the largest portion. There was more available amount for Zn and Cu in SS treatments than SC treatments. During the pot experiment, the concentration of Zn in EXCH, carbonate （CAR） and OM and Cu in EXCH and OM fractions decreased in all treatments, so their bioavailability reduced. Germination rate and plant biomass decreased when the addition rate was high and the best yield appeared in 20% mixtures at the harvest of pakchoi. The two sludges increased tissue contents of Zn and Cu especially in the SS treatments. Zn in pakchoi was not only in relationship to AEXCH and ACAR forms but also in AOM forms in the sludge-soil mixtures. Tissue content of Cu in pakchoi grown on SC-soils could not be predicted by AEXCH. These correlation rates between Zn and Cu accumulation in pakchoi and variation of different fractions increased with time, which might indicate that sludges represented stronger impacts on the plant in long-term land application.展开更多
The potential influences of cadmium (Cd) on the biochemical processes of the soil nitrogen (N) cycle, along with the dynamics of ammonification, nitrification, and denitrification processes in the rhizosphere and non-...The potential influences of cadmium (Cd) on the biochemical processes of the soil nitrogen (N) cycle, along with the dynamics of ammonification, nitrification, and denitrification processes in the rhizosphere and non-rhizosphere (bulk soil), respectively, were investigated in a Cd-stressed system during an entire soybean growing season. In terms of Cd pollution at the seedling stage, the ammonifying bacteria proved to be the most sensitive microorganisms, whereas the effects of Cd on denitrification were not obvious. Following the growth of soybeans, the influences of Cd on ammonification in the bulk soil were: toxic impacts at the seedling stage, stimulatory effects during the early flowering stage, and adaptation to the pollutant during the podding and ripening stages. Although nitrification and denitrification in the bulk soil decreased throughout the entire growth cycle, positive adaptation to Cd stress was observed during the ripening stage. Moreover, during the ripening stage, denitrification in the bulk soil under high Cd treatment (20 mg kg-1) was even higher than that in the control, indicating a probable change in the ecology of the denitrifying microbes in the Cd-stressed system. Changes in the activity of microbes in the rhizosphere following plant growth were similar to those in the non-rhizosphere in Cd treatments; however, the tendency of change in the rhizosphere seemed to be more moderate. This suggested that there was some mitigation of Cd stress in the rhizosphere.展开更多
Soil dissolved phosphorus (P) and colloidal P mobilization could be closely related to the degree of phosphorus saturation (DPS). Effects of a wide range of DPS on the distributions of dissolved P and colloidal P in a...Soil dissolved phosphorus (P) and colloidal P mobilization could be closely related to the degree of phosphorus saturation (DPS). Effects of a wide range of DPS on the distributions of dissolved P and colloidal P in a paddy soil profile were investigated in this study. Dissolved P and colloidal P in water-dispersible soil colloid suspension increased obviously with increasing DPS. The change point of DPS was at 0.12 by using a split-line model. Above the value, dissolved P (3.1 mg P kg-1 ) in soil profile would increase sharply and then transfer downward. Compared with dissolved P, colloidal P was the dominant fraction (78%-91%) of P in soil colloid suspension, and positively related to DPS without a significant change point. The high release of colloids in subsoils with low DPS was attributed to the low ionic strength and high pH value in subsoils. The DPS also had a significant and positive correlation with electrical conductivity (EC), but it showed a negative correlation with pH value. However, the concentration of colloidal P was not greatly correlated to the pH value, EC and optical density of the soil colloid suspension. The results indicated that DPS was an important factor that may affect the accumulation and mobilization of water-extractable colloidal P and dissolved P.展开更多
Soil phosphomonoesterase plays a critical role in controlling phosphorus(P) cycling for crop nutrition,especially in P-deficient soils.A 6-year field experiment was conducted to evaluate soil phosphomonoesterase activ...Soil phosphomonoesterase plays a critical role in controlling phosphorus(P) cycling for crop nutrition,especially in P-deficient soils.A 6-year field experiment was conducted to evaluate soil phosphomonoesterase activities,kinetics and thermodynamics during rice growth stages after consistent swine manure application,to understand the impacts of swine manure amendment rates on soil chemical and enzymatic properties,and to investigate the correlations between soil enzymatic and chemical variables.The experiment was set out in a randomized complete block design with three replicates and five treatments including three swine manure rates(26,39,and 52 kg P ha^(-1),representing low,middle,and high application rates,respectively) and two controls(no-fertilizer and superphosphate at 26 kg P ha^(-1)).The results indicated that the grain yield and soil chemical properties were significantly improved with the application of P-based swine manure from 0 to 39 kg P ha^(-1);however,the differences between the 39(M_(39)) and 52 kg P ha^(-1) treatments(M_(52)) were not significant.The enzymatic property analysis indicated that acid phosphomonoesterase was the predominant phosphomonoesterase in the tested soil.The M_(39) and M_(52) treatments had relatively high initial velocity(V_0),maximal velocity(V_(max)),and activation grade(lgN_a) but low Michaelis constant(K_m),temperature coefficient(Q_(10)),activation energy(E_a),and activation enthalpy(ΔH),implying that the M_(39) and M_(52) treatments could stimulate the enzyme-catalyzed reactions more easily than all other treatments.The correlation analysis showed that the distribution of soil phosphomonoesterase activities mainly followed the distributions of total C and total N.Based on these results,39 kg P ha^(-1) could be recommended as the most appropriate rate of swine manure amendment.展开更多
基金Project supported by the Provincial Technique Program of Zhejiang Province(No.2004c23024)the Key Science and Technology Program of Hangzhou City(No.2005113A07).
文摘The potential harm of heavy metals is a primary concern in application of sludge to the agricultural land. A pot experiment was conducted to evaluate the effect of two sludges on fractionation of Zn and Cu in soil and their phytotoxicity to pakchoi. The loamy soil was mixed with 0%, 20%, 40%, 60% and 80% （by weight） of digested sewage sludge （SS） and composted sludge （SC）. The additions of the both sludges caused a significant raise in all fractions, resulting in that exchangeable （EXCH） and organic matter （OM） became predominance for Zn and organic bound Cu occupied the largest portion. There was more available amount for Zn and Cu in SS treatments than SC treatments. During the pot experiment, the concentration of Zn in EXCH, carbonate （CAR） and OM and Cu in EXCH and OM fractions decreased in all treatments, so their bioavailability reduced. Germination rate and plant biomass decreased when the addition rate was high and the best yield appeared in 20% mixtures at the harvest of pakchoi. The two sludges increased tissue contents of Zn and Cu especially in the SS treatments. Zn in pakchoi was not only in relationship to AEXCH and ACAR forms but also in AOM forms in the sludge-soil mixtures. Tissue content of Cu in pakchoi grown on SC-soils could not be predicted by AEXCH. These correlation rates between Zn and Cu accumulation in pakchoi and variation of different fractions increased with time, which might indicate that sludges represented stronger impacts on the plant in long-term land application.
基金Project supported by the National Natural Science Foundation of China (No. 2977020)the National Key Basic Research Program (973 Program) of China (No. 2002CB410807)
文摘The potential influences of cadmium (Cd) on the biochemical processes of the soil nitrogen (N) cycle, along with the dynamics of ammonification, nitrification, and denitrification processes in the rhizosphere and non-rhizosphere (bulk soil), respectively, were investigated in a Cd-stressed system during an entire soybean growing season. In terms of Cd pollution at the seedling stage, the ammonifying bacteria proved to be the most sensitive microorganisms, whereas the effects of Cd on denitrification were not obvious. Following the growth of soybeans, the influences of Cd on ammonification in the bulk soil were: toxic impacts at the seedling stage, stimulatory effects during the early flowering stage, and adaptation to the pollutant during the podding and ripening stages. Although nitrification and denitrification in the bulk soil decreased throughout the entire growth cycle, positive adaptation to Cd stress was observed during the ripening stage. Moreover, during the ripening stage, denitrification in the bulk soil under high Cd treatment (20 mg kg-1) was even higher than that in the control, indicating a probable change in the ecology of the denitrifying microbes in the Cd-stressed system. Changes in the activity of microbes in the rhizosphere following plant growth were similar to those in the non-rhizosphere in Cd treatments; however, the tendency of change in the rhizosphere seemed to be more moderate. This suggested that there was some mitigation of Cd stress in the rhizosphere.
基金Supported by the National Natural Science Foundation of China (Nos. 21077088 and 41271314)the National Basic Research Program (973 Program) of China (No. 2002CB410807)
文摘Soil dissolved phosphorus (P) and colloidal P mobilization could be closely related to the degree of phosphorus saturation (DPS). Effects of a wide range of DPS on the distributions of dissolved P and colloidal P in a paddy soil profile were investigated in this study. Dissolved P and colloidal P in water-dispersible soil colloid suspension increased obviously with increasing DPS. The change point of DPS was at 0.12 by using a split-line model. Above the value, dissolved P (3.1 mg P kg-1 ) in soil profile would increase sharply and then transfer downward. Compared with dissolved P, colloidal P was the dominant fraction (78%-91%) of P in soil colloid suspension, and positively related to DPS without a significant change point. The high release of colloids in subsoils with low DPS was attributed to the low ionic strength and high pH value in subsoils. The DPS also had a significant and positive correlation with electrical conductivity (EC), but it showed a negative correlation with pH value. However, the concentration of colloidal P was not greatly correlated to the pH value, EC and optical density of the soil colloid suspension. The results indicated that DPS was an important factor that may affect the accumulation and mobilization of water-extractable colloidal P and dissolved P.
基金supported by the National Natural Science Foundation of China(Nos.21077088,41271314and 51008107)
文摘Soil phosphomonoesterase plays a critical role in controlling phosphorus(P) cycling for crop nutrition,especially in P-deficient soils.A 6-year field experiment was conducted to evaluate soil phosphomonoesterase activities,kinetics and thermodynamics during rice growth stages after consistent swine manure application,to understand the impacts of swine manure amendment rates on soil chemical and enzymatic properties,and to investigate the correlations between soil enzymatic and chemical variables.The experiment was set out in a randomized complete block design with three replicates and five treatments including three swine manure rates(26,39,and 52 kg P ha^(-1),representing low,middle,and high application rates,respectively) and two controls(no-fertilizer and superphosphate at 26 kg P ha^(-1)).The results indicated that the grain yield and soil chemical properties were significantly improved with the application of P-based swine manure from 0 to 39 kg P ha^(-1);however,the differences between the 39(M_(39)) and 52 kg P ha^(-1) treatments(M_(52)) were not significant.The enzymatic property analysis indicated that acid phosphomonoesterase was the predominant phosphomonoesterase in the tested soil.The M_(39) and M_(52) treatments had relatively high initial velocity(V_0),maximal velocity(V_(max)),and activation grade(lgN_a) but low Michaelis constant(K_m),temperature coefficient(Q_(10)),activation energy(E_a),and activation enthalpy(ΔH),implying that the M_(39) and M_(52) treatments could stimulate the enzyme-catalyzed reactions more easily than all other treatments.The correlation analysis showed that the distribution of soil phosphomonoesterase activities mainly followed the distributions of total C and total N.Based on these results,39 kg P ha^(-1) could be recommended as the most appropriate rate of swine manure amendment.
