Eff ect of prescribed burning on the small-scale spatial heterogeneity of soil microbial biomass in Pinus koraiensis and Quercus mongolica forests of China

Prescribed burning can alter soil microbial activity and spatially redistribute soil nutrient elements.However,no systematic,in-depth studies have investigated the impact of prescribed burning on the spatial patterns of soil microbial biomass in temperate forest ecosystems in Northeast China.The present study investigated the impacts of prescribed burning on the small-scale spatial heterogeneity of microbial biomass carbon(MBC)and microbial biomass nitrogen(MBN)in the upper(0–10 cm)and lower(10–20 cm)soil layers in Pinus koraiensis and Quercus mongolica forests and explored the factors that infl uence spatial variations of these variables after prescribed burning.Our results showed that,MBC declined by approximately 30%in the 10–20 cm soil layer in the Q.mongolica forest,where there were no signifi cant eff ects on the soil MBC and MBN contents of the P.koraiensis forest(p>0.05)after prescribed burning.Compared to the MBC of the Q.mongolica forest before the prescribed burn,MBC spatial dependence in the upper and lower soil layers was approximately 7%and 2%higher,respectively.After the prescribed burn,MBN spatial dependence in the upper and lower soil layers in the P.koraiensis forest was approximately 1%and 13%lower,respectively,than that before the burn,and the MBC spatial variability in the 0–10 cm soil layer in the two forest types was explained by the soil moisture content(SMC),whereas the MBN spatial variability in the 0–10 cm soil layer in the two forests was explained by the soil pH and nitrate nitrogen(NO_(3)^(–)-N),respectively.In the lower soil layer(10–20 cm)of the Q.mongolica forest,elevation and ammonium nitrogen(NH 4+-N)were the main factors aff ecting the spatial variability of MBC and MBN,respectively.In the 10–20 cm soil layer of the P.koraiensis forest,NO_(3)^(–)-N and slope were the main factors aff ecting the spatial variability of MBC and MBN,respectively,after the burn.The spatial distributions of MBC and MBN in the two forests were largely structured with higher spatial autocorrelation(relative structural variance C/[C 0+C]>0.75).However,the factors infl uencing the spatial variability of MBC and MBN in the two forest types were not consistent between the upper and lower soil layers with prescribed burning.These fi ndings have important implications for developing sustainable management and conservation policies for forest ecosystems.

Seasonal variation in soil microbial biomass carbon and nitrogen in an artificial sand-binding vegetation area in Shapotou, northern China

In this study, seasonal variation characteristics of surface soil microbial biomass carbon （MBC） and soil microbial biomass nitrogen （MBN） of an artificial vegetation area located in Shapotou for different time periods were studied using the chloroform fumigation method, and the results were compared with those of near-natural vegetation areas and mobile dunes. Results showed that the MBC and MBN levels in the 0-5 cm soil layer were higher in autumn than in summer and spring. As the prolongation of vegetation restoration raised the MBC and MBN levels in summer and autumn, no clear variation was found in spring. However, the MBC and MBN in 5-20 cm had no obvious seasonal variation. During summer and autumn, the variation trend of MBC and MBN in the vertical direction was shown to be 0-5 〉 5-10 〉 10-20 cm in the vegetation area, while for mobile dunes, the MBC and MBN levels increased as the depth increased. The natural vegetation area was shown to possess the highest MBC and MBN levels, and yet mobile dunes have the lowest MBC and MBN levels. MBC and MBN levels in artificial sand-binding vegetation increased with the prolongation of vegetation restoration, indicating that the succession of sand-binding vegetation will result in the ac- cumulation of soil carbon and nitrogen, as well as the restoration of soil fertility.

Effects of Lanthanum on Microbial Biomass Carbon and Nitrogen in Red Soil

The result of soil. culture experiment shows that lanthanum has inhibitory effect on the microbial biomass C and N in red soil, and the inhibition is strengthened with increasing concentration of La. The result of rice pot culture experiment shows that low concentration of La has slight stimulative effect on the microbial biomass C and N in red soil, but its high concentration has inhibitory effect and the inhibition is strengthened with increasing concentration of La. Soil microbial biomass is an important indicator for evaluating rare earths-polluted soil. It is assumed that the critical La concentration is 100 mg.kg(-1) at which red soil tends to be polluted.

Influence of chlorsulfuron herbicide on size of microbial biomass in the soil

A laboratory incubation experiment was conducted to study the effect of chlorsulfuron herbicide on the size of the microbial in loamy sand soil. The herbicide was applied, at four levels that were control, field rate 0\^01 (FR), 0\^1 (10FR) and 1 (100FR) μg/g. Determinations of microbial biomass C content and microbial biomass N content were carried out 1, 3, 5, 7, 10, 15, 25 and 45 days after herbicide application. In comparison to untreated soil, the microbial biomass carbon and biomass nitrogen decreased significantly in soil treated with herbicide in levels 10FR and 100FR within the first 10 days incubation. A more considerable increase in the microbial biomass C∶N ratio was observed in the herbicide treated soil than the non treated control. This effect was transitory and only at the higher rates of chlorsulfuron was significant.

Soil microbial biomass and its controls

Microbial biomass represents a relatively small standing stock of nutrients, compared to soil organic matter, but it can act as a labile source of nutrients for plants, a pathway for incorporation of organic matter into the soil, and a temporary sink for nutrients. This review describes several factors controlling the dynamics of soil microbial biomass. These factors mainly include organic carbon and nitrogen limitation, residue and nutrient management, differences in plant species, soil texture, soil moisture and temperature. On the basis of detailed analysis, it is reasonable that future research would be focused on the impact of land use change on soil MB in tropical and subtropical ecosystems.

Effects of Long-Term Combined Application of Organic and Mineral Fertilizers on Microbial Biomass,Soil Enzyme Activities and Soil Fertility

Soil health is important for the sustainable development of terrestrial ecosystem. In this paper, we studied the relationship between soil quality and soil microbial properties such as soil microbial biomass and soil enzyme activities in order to illustrate the function of soil microbial properties as bio-indicators of soil health. In this study, microbial biomass C and N contents （Cmic ＆ Nmic）, soil enzyme activities, and soil fertility with different fertilizer regimes were carried out based on a 15-year long-term fertilizer experiment in Drab Fluvo-aquic soil in Changping County, Beijing, China. At this site, 7 different treatments were established in 1991. They were in a wheat-maize rotation receiving either no fertilizer （CK）, mineral fertilizers （NPK）, mineral fertilizers with wheat straw incorporated （NPKW）, mineral fertilizers with incremental wheat straw incorporated （NPKW＋）, mineral fertilizers plus swine manure （NPKM）, mineral fertilizers plus incremental swine manure （NPKM＋） or mineral fertilizers with maize straw incorporated （NPKS）. In different fertilization treatments Cmic changed from 96.49 to 500.12 mg kg^-1, and Nmic changed from 35.89 to 101.82 mg kg^-1. Compared with CK, the other treatments increased Cmic ＆ Nmic, Cmic/Corg （organic C） ratios, Cmic/Nmic, urease activity, soil organic matter （SOM）, soil total nitrogen （STN）, and soil total phosphorus （STP）. All these properties in treatment with fertilizers input NPKM＋ were the highest. Meantime, long-term combined application of mineral fertilizers with organic manure or crop straw could significantly decrease the soil pH in Fluvo-aquic soil （the pH around 8.00 in this experimental soil）. Some of soil microbial properties （Cmic/Nmic, urease activity） were positively correlated with soil nutrients. Cmic/Nmic was significantly correlated with SOM and STN contents. The correlation between catalase activity and soil nutrients was not significant. In addition, except of catalase activity, the soil pH in this experiment was negatively correlated with soil microbial properties. In conclusion, soil microbial properties reflect changes of soil quality and thus can be used as bio-indicators of soil health.

Seasonal dynamics of soil microbial biomass C and N of Keteleeria fortunei var. cyclolepis forests with different ages

Soil microbial biomass is an important indicator to measure the dynamic changes of soil carbon pool.It is of great signifi cance to understand the dynamics of soil microbial biomass in plantation for rational management and cultivation of plantation.In order to explore the temporal dynamics and infl uencing factors of soil microbial biomass of Keteleeria fortunei var.cyclolepis at diff erent stand ages,the plantation of diff erent ages(young forest,5 years;middle-aged forest,22 years;mature forest,40 years)at the Guangxi Daguishan forest station of China were studied to examine the seasonal variation of their microbial biomass carbon(MBC)and microbial biomass nitrogen(MBN)by chloroform fumigation extraction method.It was found that among the forests of diff erent age,MBC and MBN diff ered signifi cantly in the 0–10 cm soil layer,and MBN diff ered signifi cantly in the 10–20 cm soil layer,but there was no signifi cant diff erence in MBC for the 10–20 cm soil layer or in either MBC or MBN for the 20–40 cm soil layer.With increasing maturity of the forest,MBC gradually decreased in the 0–10 cm soil layer and increased fi rstly and then decreased in the 10–20 cm and 20–40 cm soil layers,and MBN increased fi rstly and then decreased in all three soil layers.As the soil depth increased,both MBC and MBN gradually decreased for all three forests.The MBC and MBN basically had the same seasonal variation in all three soil layers of all three forests,i.e.,high in the summer and low in the winter.Correlation analysis showed that MBC was signifi cantly positively correlated with soil organic matter,total nitrogen,and soil moisture,whereas MBN was signifi cantly positively correlated with soil total nitrogen.It showed that soil moisture content was the main factor determining the variation of soil microbial biomass by Redundancy analysis.The results showed that the soil properties changed continuously as the young forest grew into the middle-aged forest,which increased soil microbial biomass and enriched the soil nutrients.However,the soil microbial biomass declined as the middle-age forest continued to grow,and the soil nutrients were reduced in the mature forest.

Effect of heat-disturbance on microbial biomass carbon and microbial respiration in Chinese fir(Cunninghamia lanceolata) forest soils

Prescribed fire has now become the usual management practice in the Chinese fir （Cunninghamia lanceolata （Lamb.） Hook.） plantation in southern China. Heat generated during fire may affect carbon （C） dynam- ics in soils. We investigated the microbial biomass C （MBC） and microbial respiration in two Chinese fir forest soils （one is not exposed to fire for the past 88 years, and the other is recently exposed to prescribed fire） after soil heating （100 and 200 ℃） under three moisture regimes [25, 50 and 75 % of water holding capacity （WHC）]. For both soils, significant reduction in MBC with increasing heating temperature was found. Soils without exposing to fire previously had significantly greater MBC concentra- tion than the fire-exposed soils when heated at 100 or 200 ℃. Lower soil water content resulted in higher MBC concentrations in both soils. In contrast, both soils had the highest soil microbial respiration rate at 50 % WHC. Soils without exposing to fire previously had the greatest microbial respiration rates at 200 ℃, while the fire-ex- posed soils when heated at 100 ℃ had greatest microbialrespiration rates. During 14-days post-heat incubation, soil MBC in both soils was greatest after heating at 200 ℃ and 25 % WHC. However, soil previously exposed to fire had the lowest CO2 evolution when incubated at 25 % WHC.

Short Term Influence of Organic and Inorganic Fertilizer on Soil Microbial Biomass and DNA in Summer and Spring

The present study was conducted to see the short term impact of organic and inorganic fertilizers on soil microbial biomass both in spring and summer. Also aimed to observe the correlation between soil microbial biomass and soil DNA. The study concluded that type of fertilizer might alter the soil microbial biomass and DNA contents. In soil treated with organic fertilizers resulted in higher concentrations of microbial biomass and DNA contents in summer as compared to spring dute to increase in temperature. Correspondingly, in case of inorganic fertilizer, concentrations of soil microbial biomass and DNA detected higher in summer instead of spring. The statistical correlation between soil microbial biomass, DNA and ODR in spring and summer along with organic and inorganic fertilizers were calculated highly significant （p〉0.01）. This study demonstrated the impact of fertilizers and seasonal variations on soil microbial biomass and also revealed significant correlation between soil microbial biomass and soil DNA.

Impact of enclosure management on soil properties and microbial biomass in a restored semi-arid rangeland, Kenya

Rangeland degradation is a serious problem throughout sub-Saharan Africa and its restoration is a challenge for the management of arid and semi-arid areas. In Lake Baringo Basin of Kenya, communities and individual farmers are restoring indigenous vegetation inside enclosures in an effort to combat severe land degradation and address their livelihood problems. This study evaluated the impact of enclosure management on soil properties and microbial biomass, being key indicators of soil ecosystem health. Six reseeded communal enclosures using soil embankments as water-harvesting structures and strictly regulated access were selected, varying in age from 13 to 23 years. In six private enclosures, ranging from 3 to 17 years in age, individual farmers emulated the communal enclosure strategy and restored areas for their exclusive use. Significant decreases in bulk density, and increases in the soil organic carbon, total nitrogen and microbial biomass contents and stocks were found in the enclosures as compared with the degraded open rangeland. In the private enclosures, the impact of rehabilitation on the soil quality was variable, and soil quality was in general lower than that obtained under communal management. The significant increase of absolute stocks of carbon, nitrogen and microbial biomass compared to the degraded open rangeland indicates the potential for the restoration of soil quality through range rehabilitation. Over-sowing with indigenous legume fodder species could improve total nitrogen content in the soil and nutritional value of the pastures as well.

Response of microbial biomass and bacterial community composition to fertilization in a salt marsh in China

The effects of nitrogen （N） addition on microbial biomass, bacterial abundance, and community composition in sediment colonized by Suaeda heteroptera were examined by chloroform fumigation extraction method, real-time quantitative polymerase chain reaction, and denaturing gradient gel electrophoresis （DGGE） in a salt marsh located in Shuangtai Estuary, China. The sediment samples were collected from plots treated with different amounts of a single N fertilizer （urea supplied at 0.1, 0.2, 0.4 and 0.8 g/kg （nitrogen content in sediment） and different forms of N fertilizers （urea, （NH4）2SO4, and NH4NO3, each supplied at 0.2 g/kg （calculated by nitrogen）. The fertilizers were applied 1-4 times during the plant-growing season in May, luly, August, and September of 2013. Untreated plots were included as a control. The results showed that both the amount and form of N positively influenced microbial biomass carbon, microbial biomass nitrogen, and bacterial abundance. The DGGE profiles revealed that the bacterial community composition was also affected by the amount and form of N. Thus, our findings indicate that short-term N amendment increases microbial biomass and bacterial abundance, and alters the structure of bacterial community.

Contrasting resilience of soil microbial biomass,microbial diversity and ammonification enzymes under three applied soil fumigants

Fumigation is a widely applied approach to mitigate the soil-borne diseases.However,the potential effects of currently applied fumigants on ammonification remain unclear.An 84-day incubation experiment was conducted based on non-fumigated soil(CK)and fumigated soil using three common fumigants,i.e.,chloropicrin(CP),1,3-dichloropropene(1,3-D),and metam sodium(MS).The results showed that,the three fumigants all decreased the microbial C,and the largest reduction(84.7%)occurred with the application of CP.After fumigation,the microbial diversity in the CP treatment rapidly recovered,but that in the 1,3-D treatment decreased and did not recover by the end of the experiment.The application of MS showed no impact on the microbial diversity during the assay,indicating that significantly different microbial diversity can be achieved by choosing different fumigants.Futhermore,the three fumigants showed divergent effects on the enzymes involved in ammonification.The analysis showed that the enzyme variation with CP application was mainly associated with the changed microbial C and N(P<0.05),and not with the microbial community,which was different from the observed effects of 1,3-D or MS application.In addition,the soil quality index showed that CP was still significantly harmful at the end of incubation compared with the good resilience of MS,indicating that CP may not be a suitable fumigant.

Effect of Different Irrigation Methods on Dissolved Organic Carbon and Microbial Biomass Carbon in the Greenhouse Soil

The objective of this study was to investigate the contents and distribution of dissolved organic carbon （DOC） and microbial biomass carbon （MBC） at 0-100 cm soil depth under three irrigation treatments, viz., subsurface, drip and furrow irrigation in the greenhouse soil. The soil samples were collected at different depths （0-100 cm）, and the contents of soil total organic carbon （TOC）, DOC and MBC were analysed. The experiment was conducted for 10 yr, during which period the application of fertilizers and crop management practices were kept identical. The results showed that the contents of TOC, DOC and MBC were significantly affected by different irrigation regimes, decreased with the increase of soil depth. TOC at 0-10 and 80-100 cm soil depths followed the order of furrow irrigation 〉 subsurface irrigation 〉 drip irrigation, whereas at the depth of 10-80 cm followed the order of subsurface irrigation 〉 furrow irrigation 〉 drip irrigation. DOC and MBC contents at 0-100 cm soil depths followed the order of furrow irrigation 〉 drip irrigation 〉 subsurface irrigation, and drip irrigation 〉 furrow irrigation 〉 subsurface irrigation, respectively. The ratios of DOC and MBC to TOC accounted for 4.98-12.87% and 1.48-2.82%, respectively, which were the highest in the drip irrigation treatment, followed were in the furrow irrigation treatment, and the lowest in subsurface irrigation treatment. There were significant positive correlations among the contents of DOC, MBC and TOC in all irrigation treatments. The furrow irrigation facilitated the accumulation of TOC and DOC, while drip irrigation increased the MBC. The content of TOC and the ratios of DOC to TOC were the lowest in subsurface irrigation treatment.

Soil microbial biomass and population in response to seasonal variation and age in Gmelina arborea plantations in south-western Nigeria

We investigated the Effects of plantation development, seasons, and soil depth on soil microbial indices in Gmelina arborea plantations in south-western Nigeria. Soil samples were obtained from the soil depths of 0-15 and 15-30 cm from plantations of six different ages during the rainy season, dry seasons, and their transitions. We used plate count and fumigation-extraction methods to determine microbe population and microbial biomass carbon （MB-C） and nitrogen （MB-N）, respectively. Plantation age did not affect microbial indices, implying a non-significant effect of plantation development on microbial communities. It could also imply that soil microbial indices had already stabilized in the sampled plantations. Seasonal variation and soil depth had significant effects on microbial indices. At 0-15 cm soil depth, mean MB-C increased from 50.74 μg·g^-1 during the peak of the dry season （i.e. March） to 99.58μg·g-1 during the peak of the rainy season （i.e. September）, while it increased from 36.22μg·.g^-1 to 75.31μg·.g^-1 at 15-30 cm soil depth between the same seasonal periods. Bacteria populations and MB-N showed similar increasing trends. Correlations between MB-C, MB-N, microbe populations, and rainfall were positive and linear. Significantly higher microbial activities took place in the plantations during the rainy season, increased with soil wetness, and decreased at greater soil depth.

Effects of freezing intensity on soil solution nitrogen and microbial biomass nitrogen in an alpine grassland ecosystem on the Tibetan Plateau,China

The change of freeze-thaw pattern of the Tibetan Plateau under climate warming is bound to have a profound impact on the soil process of alpine grassland ecosystem;however,the research on the impact of the freeze-thaw action on nitrogen processes of the alpine grassland ecosystem on the Tibetan Plateau has not yet attracted much attention.In this study,the impact of the freezing strength on the soil nitrogen components of alpine grassland on the Tibetan Plateau was studied through laboratory freeze-thaw simulation experiments.The 0–10 cm topsoil was collected from the alpine marsh meadow and alpine meadow in the permafrost region of Beilu River.In the experiment,the soil samples were cultivated at –10℃,–7℃,–5℃,–3℃ and –1℃,respectively for three days and then thawed at 2℃ for one day.The results showed that after the freeze-thaw process,the soil microbial biomass nitrogen significantly decreased while the dissolved organic nitrogen and inorganic nitrogen significantly increased.When the freezing temperature was below –7℃,there was no significant difference between the content of nitrogen components,which implied a change of each nitrogen component might have a response threshold toward the freezing temperature.As the freeze-thaw process can lead to the risk of nitrogen loss in the alpine grassland ecosystem,more attention should be paid to the response of the soil nitrogen cycle of alpine grasslands on the Tibetan Plateau to the freeze-thaw process.

Bentonite-humic acid improves soil organic carbon,microbial biomass,enzyme activities and grain quality in a sandy soil cropped to maize(Zea mays L.) in a semi-arid region

A bentonite-humic acid(B-HA) mixture added to degraded soils may improve soil physical and hydraulic properties, due to effects such as improved soil structure and increased water and nutrient retention, but its effect on soil physicochemical and biological properties, and grain quality is largely unknown. The effect of B-HA, added at 30 Mg ha^(-1), was studied at 1,3, 5 and 7 years after its addition to a degraded sandy soil in a semi-arid region of China. The addition of B-HA significantly increased water-filled pore space and soil organic carbon, especially at 3 to 5 years after its soil addition to the soil. Amending the sandy soil with B-HA also increased the content of microbial biomass(MB)-carbon,-nitrogen and-phosphorus, and the activities of urease, invertase, catalase and alkaline phosphatase. The significant effect of maize(Zea mays L.) growth stage on soil MB and enzyme activities accounted for 58 and 84% of their total variation, respectively. In comparison, B-HA accounted for 8% of the total variability for each of the same two variables. B-HA significantly enhanced soil properties and the uptake of N and P by maize in semi-arid areas. The use of B-HA product would be an effective management strategy to reclaim degraded sandy soils and foster sustainable agriculture production in northeast China and regions of the world with similar soils and climate.

Effects of Carbon and Nitrogen Additions on Soil Microbial Biomass Carbon and Enzyme Activities Under Rice Straw Returning

The effects of different amounts of carbon and nitrogen sources on the soil microbial biomass carbon,dissolved organic carbon and related enzyme activities were studied by the simulation experiment of rice straw returning to the field,and the mechanism of the decomposition of rice straw returning to the field was discussed.Completely randomized experiment of the two factors of the three levels was designed,and a total of nine treatments of indoor soil incubation tests were conducted.Full amount of rice straw was applied to the soil in this simulation experiment and different amounts of brown sugar and urea were added in the three levels of 0(no carbon source and nitrogen source),1(low levels of carbon and nitrogen sources)and 2(high levels of carbon and nitrogen sources),respectively.The results showed that the addition of different amounts of carbon and nitrogen sources to the rice straw could increase the soil carbon content.Compared with T0N0,the microbial biomass carbon of T2N2 was increased significantly by 170.48%;the dissolved organic carbon content of T1N2 was significantly increased by 58.14%and the free humic acid carbon contents of T0N2,T1N1 and T2N0 were significantly increased by 56.16%and 45.55%and 47.80%,respectively;however,there were no significant differences among those of treatments at later incubation periods.The addition of different carbon and nitrogen sources could promote the soil enzyme activities.During the incubation period,all of the soil enzyme activities of adding sugar and urea were higher than those of T0N0 treatment.Therefore,the addition of different amounts of carbon and nitrogen sources to rice straw returning could improve soil microbial biomass carbon content,dissolved organic carbon and soil enzyme activities.

Increasing soil microbial biomass nitrogen in crop rotation systems by improving nitrogen resources under nitrogen application

Soil microbial biomass nitrogen(MBN)contains the largest proportion of biologically active nitrogen(N)in soil,and is considered as a crucial participant in soil N cycling.Agronomic management practices such as crop rotation and monocropping systems,dramatically affect MBN in agroecosystems.However,the influence of crop rotation and monocropping in agroecosystems on MBN remains unclear.A meta-analysis based on 203 published studies was conducted to quantify the effect of crop rotation and mono-cropping systems on MBN under synthetic N fertilizer application.The analysis showed that crop rotation significantly stimulated the response ratio(RR)of MBN to N fertilization and this parameter reached the highest levels in upland-fallow rotations.Upland mono-cropping did not change the RR of MBN to N application,however,the RR of MBN to N application in paddy mono-cropping increased.The difference between crop rotation and mono-cropping systems appeared to be due to the various cropping management scenarios,and the pattern,rate and duration of N addition.Crop rotation systems led to a more positive effect on soil total N(TN)and a smaller reduction in soil pH than mono-cropping systems.The RR of MBN to N application was positively correlated with the RR of mineral N only in crop rotation systems and with the RR of soil pH only in mono-cropping systems.Combining the results of Random Forest(RF)model and structural equation model showed that the predominant driving factors of MBN changes in crop rotation systems were soil mineral N and TN,while in mono-cropping systems the main driving factor was soil pH.Overall,our study indicates that crop rotation can be an effective way to enhance MBN by improving soil N resources,which promote the resistance of MBN to low pH induced by intensive synthetic N fertilizer application.

Variation of Soil Microbial Biomass and Enzyme Activities at Different Growth Stages of Rice (Oryza sativa)

A pot experiment was conducted under submerged conditions with hybrid rice Zhenong 7 to study the variation in the soil microbial biomass carbon （Cmic）, soil microbial biomass nitrogen （Nmic）, soil respiration rate, soil microbial metabolic quotient, soil enzyme activities, chlorophyll content, proline content and peroxidase activity （POD） in rice leaf at different growth stages. The soil Cmic, Nmic and soil respiration rate significantly increased at the early stage and then declined during rice growth, but ascended slightly at maturity. However, soil metabolic quotient declined at all the stages. Soil urease activity increased at first and then decreased, while acid phosphatase and dehydrogenase activities descended before ascended and then descended again. Soil urease activity and acid phosphatase activity showed a peak value at the tillering stage about 30 days after rice transplanting, but the peak value of dehydrogenase activity emerged at about 50 days after rice transplanting and the three soil enzymatic activities were significantly different at the different developmental stages. As rice growing, chlorophyll content in rice leaf descended at the early stage then ascended and a peak value appeared at about the 70th after rice transplanting, after that declined drastically, while POD activity increased gradually, but proline content declined gradually. There was a slight relation between rice physiological indices and soil biochemical indices, which indicated that soil biochemical characteristics were affected significantly by rice growth in the interaction system of the rice. soil and microorganisms.

The Effects of Applying Organic Matter in Wind Blown Soil on Microbial Biomass and Enzyme Activity

Field experiment was conducted to study the effect of applying organic matter in wind blown soil on microbial biomass and enzyme activity.The results showed that microbial biomass and enzyme activity keep dynamic changes during wheat growing season in wind blown soil,and reached the peak level in wheat booting stage.Compared with chemical fertilizer,all the other treatments could increase the microbial biomass in different degree,the same as catalsae and alkaline phosphatase activity,But urease activity was slightly difference from them.