连作土灭菌对葡萄生长及根系分泌特性的影响

为探讨葡萄连作障碍产生的原因,采用盆栽模拟试验,对葡萄连作土壤进行蒸汽灭菌,研究连作土灭菌后葡萄植株生长及根系分泌特性的变化。结果表明,连作土灭菌显著增加了葡萄植株的株高和茎粗,其中以7月份的增加幅度最大,分别比连作土增加了1.51倍和0.14倍,地上和地下鲜质量随着生长期的延长也表现出显著增加的趋势,以9月份的增加幅度最大,分别增加了1.18倍和1.09倍。并且连作土壤灭菌后葡萄叶片SOD酶活性增强,MDA含量降低,根系活力随生长期的延长,表现出先下降再上升的趋势。另外,研究发现连作土壤灭菌后葡萄根系分泌的还原糖及氨基酸总量显著降低,分别比连作土壤降低了72.60%和91.10%;氨基酸的种类及其含量也发生改变,其中Ile、Leu和Tyr3种氨基酸未达到检测水平,其他氨基酸含量降低。可见,对连作土壤进行有效的灭菌后,可以改变根际微生态的核心因素即根系分泌物的成分及含量,促进植株的生长,减轻葡萄的连作障碍,进而证实了土壤生物因素是葡萄连作障碍产生的重要原因之一。

丛枝菌根真菌对连作土壤中葡萄生长及根系分泌特性的影响

为了研究不同丛枝菌根真菌[地表球囊霉Glomus versiforme(简称G.V)、摩西球囊霉Glomus mosseae(简称G.M)和幼套球囊霉Glomus etunicatum(简称G.E)]对连作土壤中贝达(V.vulpina×V.labrusca Beta)葡萄扦插苗生长及根系分泌特性的影响,采用盆栽试验,将连作土灭菌后接种不同丛枝菌根真菌,测定贝达葡萄地上部及根系生理指标,利用液相色谱-质谱联用仪测定根系分泌的物质种类及含量。结果表明:3种丛枝菌根真菌处理葡萄的株高、茎粗、地上及地下鲜重均增加,叶片SOD活性增强,MDA含量降低,根系活力增强。其中G.V处理和G.M处理效果最显著,叶片SOD酶活性分别为对照的2.23倍和2.18倍,MDA含量比对照低12.83%和17.51%,根系活力比对照提高17.07%和20.33%。接种菌剂后,葡萄根系分泌的物质种类及其含量也发生变化,其中G.V处理葡萄根系分泌的物质种类较多,并且含有特异性成分橙花叔醇。连作土灭菌后接种丛枝菌根真菌促进了葡萄的生长,其中G.V处理和G.M处理效果较好。

甜菜连作土壤对甜菜幼苗生长影响及其化感物质成分分析

为探究甜菜化感物质成分,减轻甜菜连作带来的副作用,设置休闲土、连作一年的重茬土2个处理组,探究不同土壤对甜菜幼苗发芽率、染病率以及株高、茎粗等生长指标的影响。采用质谱联用(GC-MS)分析技术初步筛选了2种土壤中差异显著(P<0.05)的化合物。结果表明:与休闲土相比,重茬土种植的甜菜幼苗发芽率没有受到显著影响,但是幼苗感染立枯病的概率大大增加,且达到显著水平。在株高、叶面积、地上部鲜重方面,休闲土种植和重茬土种植差异显著,但茎粗差异不显著(P>0.05)。利用质谱联用技术,得出15种疑似的甜菜化感物质。甜菜连作土壤中的化感物质成分会对甜菜幼苗的生长造成一定的影响,筛选和鉴定疑似化感物质成分,对缓解甜菜连作障碍、提高甜菜产质量具有重要意义。

蔬菜作物轮作对嫁接西瓜植株生理代谢与生长的影响

以山东昌乐连作20年西瓜(Citrullus lanatus)的土壤为对照,比较轮作大葱(Allium fistulosum)、大蒜(Alliumsativum)和芹菜(Apium graveolens)土壤对嫁接西瓜部分生理代谢与生长的影响,结果表明,轮作可以提高嫁接西瓜根系活力和生长量,其中以种植芹菜的处理根系活力最高,生长量最大,其茎粗、地下部鲜重、单株叶片数和根系活力分别比连作西瓜处理(对照)增加10.7%、20.3%、10.5%和38.8%;轮作大葱、大蒜和芹菜处理的西瓜叶片叶绿素含量显著高于对照,其中轮作芹菜增加最多,叶绿素a和叶绿素b含量分别比对照增加了24.9%和17.8%;连作西瓜处理的嫁接西瓜叶片净光合速率明显低于其他处理;轮作处理显著提高嫁接西瓜根和叶的SOD、POD、CAT活性,而降低MDA活性,其中轮作芹菜处理中嫁接西瓜叶片的MDA含量降低最多,为9.1%。结论认为,轮作可以改善嫁接西瓜生理代谢和生长,有效减轻连作危害。

Effects of Different Agricultural Managements on Characteristics of Soil Microbial Community under Continuous Cropped Strawberry(Fragaria ananassa Duchesne)

[Objective] The objective of this study was to investigate the effects of different agricultural managements on soil microbial population,activity,functional diversity and soil enzyme activity in continuous mono-cropping field of strawberry.[Method]A field plot experiment was carried out to evaluate characteristics of soil microbial community by soil enzyme analysis,microbial cultivation and Biolog analysis.[Result]The results showed that bacteria population proportion,the ration of bacteria to fungi,microorganism amount,AWCD,soil dehydrogenase activity,the Shannon,Simpson,and Mcintosh indices of soil microbial communities were obviously increased under strawberry-rice rotation,soil solarization with rice bran,and calcium cyanamide（CaCN2）treatments,in addition,soil urease activity was significantly increased under strawberry-rice rotation and soil solarization with rice bran treatment,when compared with no fertilization.When compared with conventional fertilization treatment,strawberry-rice rotation and soil solarization with rice bran both significantly increased AWCD and Mcintosh index of soil microbial communities,meanwhile respectively increased soil urease and dehydrogenase activity.PCA analyses suggested that carbon utilization of soil microbial communities under strawberry-rice rotation,soil solarization with rice bran,and calcium cyanamide treatment was obviously different from that of conventional fertilization and no fertilization treatment.[Conclusion] strawberry-rice rotation and soil solarization with rice bran were effective agricultural managements to control soil biological degradation under Continuous Cropped Strawberry.

Effects of Different Fertilization Treatments on Soil Microbial Biomass,Soil Enzyme Activities and Related Nutrients in Continuous-cropping Sugarcane Field

[Objective] This study was conducted to expound the fertility improvement effect in continuous-cropping sugarcane field and provide reference for establishment of rational sugarcane fertilization system and improvement of soil quality in continuous-cropping sugarcane field. [Method] The soil in the experimental region is latosolic red soil which was planted with sugarcane for 11 years continuously, and 8 treatments including sole application of chemical fertilizers, sole application of organ- ic fertilizer, and combined application of organic fertilizer and chemical fertilizers were designed according to different fertilization measures. The effects of different fertilization treatments on soil microbial biomass, soil enzyme activities and related fertility factors were determined. [Result} Different fertilization treatments all showed soil microbial biomass N, C and P and activities of soil acid phosphatase, catalase, sucrase and urease higher than the CK. Soil microbial biomass N increased by 5.56%-67.13%, soil microbial biomass C increased by 4.01%-20.40%, and soil mi- crobial biomass P increased by 6.39%-67.02%. The activity of acid phosphatase was improved by 12.96%-35.19%, the activity of catalase was improved by 18.24% -78.93%, the activity of sucrase was improved by 3.00%-42.00%, and the activity of urease was improved by 1.21%-23.43%. However, the soil nutrients of different fertilization treatments increased non-significantly （P〉0.05）. Soil microbial biomass N, C and P and activities of acid phosphatase, catalase and urease were in significant （P〈0.05） or very significant correlation （P〈0.01） with contents of soil rapidly available P, rapidly available K and total N. [Conclusion] The evaluation of improvement of soil fertility in continuous-cropping sugarcane field using soil microbial biomass and enzyme activities as indexes is more comprehensive and sensitive.

Effect of Continuous Plantation of Chinese Fir on Soil Fertility

The changes in soil fertility under continuous plantation of Chinese fir were studied by comparing soilsamples from different forest stands: the first and second plantations of Chinese fir, evergreen broad-leavedforests, and clear-cut and burnt Chinese fir land located at Xihou Village, Nanping of Fujian Province. Thesoils were humic red soil originated from weathered coarse granite of the Presinian system. Soil PH, CEC,base saturation, exchangeable Ca￣(2+), exchangeable Mg￣(2+) and Al-P declined after continuous plantation ofChinese fir. The same trends were also found in the soils under broad-leaved stands and slash burnt lands.The explantation was that not merely the biological nature of the Chinese fir itself but the natural leachingof nutrients, soil erosion and nutrient losses due to clear cutting and slash burning of the preceding plantationcaused the soil deterioration. Only some of main soil nutrients decreased after continuons plantation ofChinese fir, depending on specific silvicultural system, which was different from the conclusions in some otherreports which showed that all main nutrients, such as OM, total N, available P and available K decreased.Some neccessary steps to make up for the lost base, to apply P fertilizer and to avoid buring on clear cutlands could be taken to preventsoil degradation and yield decline in the system of continuous plantation ofChinese fir.

Effects of Tobacco-rice Continuous Cropping Years on Soil Physicochemical Properties and Tobacco Yield and Quality

To investigate the effects of long term tobacco-rice continuous cropping on soil nutrients and flue-cured tobacco leaf yield and quality, the soils of different con- tinuous cropping years were selected in tobacco-rice multiple system of Hengyang. Some important indexes, including pH, contents of organic matter and available nu- trients of N P K, contents of medium trace elements of soil samples, and contents of main chemical components of flue-cured tobacco samples were detected for fur- ther analyzing. The results showed that pH value of moderate continuous cropping soil（≤7 years） was more coordinated, in addition, leaf yield and quality of flue-cured tobacco were contained, and the sugar-nicotine ratio and potassium-chlorine ratio were proper. However, under long-term continuous cropping （≥10 years） condition, the soil became acidification, and yield and output value of flue-cured tobacco de- clined. It was suggested that improving soil quality by planting green manure or keeping fallow after continuous cropping 7 years in tobacco-rice system.

Effects of Dongshengbao Liquid Organic Fertilizer on Soil Improvement of Continuous Cropping Cucumber

[Objective] The effects of Dongshengbao liquid organic fertilizer on soil im- provement of continuous cropping cucumber and the growth conditions of the cu- cumber were studied to provide the scientific basis for solving the problem of con- tinuous cropping of vegetable soil. [Method] The soil of continuous cropping was sampled. The soil EC, pH, nutrient contents and cucumber height, dry weight of aboveground part and leaf area etc were studied with the method of potted cucum- ber test. [Result] Soil EC applied by Dongshengbao liquid organic fertilizer reached 0.93 mS/cm, and decreased by 27.91% compared with the contrast. Soil pH reached 5.89, and increased with 0.86% compared with the contrast. Dry weight of aboveground part, plant height and leaf area of cucumber were increased by 283.08%, 242.12% and 254.02% compared with the contrast. The incidence rank of cucumber Didymella bryoniae was below grade 2. Soil EC applied by compound fertilizer reached 1.53 mS/cm, and increased by 18.6% compared with the contrast. Soil pH reached 5.09, and decreased by 12.84% compared with the contrast. Dry weight of aboveground part, plant height and leaf area of cucumber were increased by 32.31%,-37.24% and 26.20% compared with the contrast. The incidence rank of cucumber Didymella bryoniae was above grade 2. [Conclusion] The organic fertilizer could solve the problems of soil salinization and soil acidification of continuous crop- ping, improve the resistance ability of Didymella bryoniae and promote the plant growth.

Effect of Suppressed DOF on a Rigid RC Bridge Response under Strong Earthquake Motion

NLTHA （nonlinear time history analysis） is impractical for widespread used by the professional engineer because it requires long and inefficient computational time involving complexities when six DOF （degree of freedom） per node is applied. The NLTHA nowadays is predicted by MPA （modal pushover analysis）. In this method, effects of higher modes on the dynamic response are considered to estimate seismic demands for structures. In this study, the effect of the reduction of number of DOF is analyzed using 3D NLTHA together with MPA of a rigid connection RC bridge under large earthquake motion. The results are compared with the 6 DOF NLTHA in terms of response of the structure and CPU time to obtain the most efficient computational effort. Result of NLTHA showed that the computational time of the structure both for 4 DOF （without two lateral torsional effects） and 3 DOF （without two lateral torsional and vertical displacements） was reduced significantly compared to the structure using 6 DOF. The reduction of computational time was close to fifty percent both for 4 and 3 DOF＇s. When the maximum responses between NLTHA and MPA are compared, it is found that the differences are insignificant.

Impact of Anaerobic Soil Disinfestation Treatment on the Properties of Tomato Continuous Cropping Soil

To investigate the impact of anaerobic soil disinfestation(ASD)treatment with different processing duration on tomato continuous cropping soil,a total of eight treatments were designed,which included two treatment temperatures of 10℃ and 30℃,and four treatment times of 3,4,5 and 7 weeks(w).The results showed that whether the temperature was 10℃ or 30℃,the pH values,TOC and available K contents in the soil treated by the ASD method were significantly increased(P<0.05),while the EC values and NO_(3)^(-)contents in soils treated by ASD were significantly reduced compared with the untreated group(P<0.05).The Fusarium oxysporum population in soils treated by ASD decreased with the extension of the treatment time.When the treatment temperature was 30℃,the effect on the removal of the NO_(3)^(-)that had accumulated in soils treated by ASD was significantly better than the treatment temperature of 10℃(P<0.05).When soil was treated by ASD for more than 5 w at 30℃,the NH4+content in soil was significantly increased(P<0.05)compared with the untreated soil.In conclusion,NO_(3)^(-)accumulation in soils could not be completely eliminated with treatment by ASD,even when the treatment time at 10℃ was prolonged.Whether the treatment temperature was 10℃ or 30℃,the F.oxysporum population in soils treated by ASD decreased significantly with the extension of the treatment time to more than 5 w compared with treatment only for only 3 w.

Soil Enzyme Activities and Organic Matter Composition Affected by 26 Years of Continuous Cropping

The study was to determine the long-term effects of subtropical monoculture and rotational cropping systems and fertilization on soil enzyme activities and soil C, N, and P levels. Cropping systems included continuous sorghum(Sorghum bicolor L.), cotton(Gossypium hirsutum L.), corn(Zea mays L.), and cotton/sorghum rotations after 26 years of treatment imposition. Soil under continuous sorghum and continuous corn had 15% and 11%, respectively, greater C concentrations than soil under continuous cotton.Organic C was 10% higher at 0–7.5 cm than at 7.5–15 cm. Total N followed similar trends with soil depth as organic C. Continuous sorghum had 19% higher total N than other crop species and rotations. With fertilization, continuous cotton had the highest total P at 0–7.5 cm and sorghum had the highest at 7.5–15 cm. Soil total P was 14% higher at 0–7.5 than at 7.5–15 cm, and fertilization increased 15% total P compared to unfertilized soil. Arylsulfatase, alkaline phosphatase, and β-d-glucosidase activity were the highest for sorghum and the lowest for cotton. Rotation increased enzyme activities compared to continuous cotton but not for continuous sorghum. Of all crop species and rotations, continuous cotton generally showed the lowest levels of organic matter and enzyme activities after 26 years. Fertilization significantly increased the yields for all cropping systems, but rotation had no significant effect on either sorghum or cotton lint yield compared to each crop grown in monoculture. Long-term cropping did not increase soil organic matter levels beyond short-term gains, indicating the difficulty in promoting C sequestration in subtropical soils.

Prevention and Control of Continuous Cropping Obstacle of Watermelon by Reductive Soil Disinfestation (RSD)

This study aimed to explore whether reductive soil disinfestation（RSD） is an effective method of controlling continuous cropping obstacle of watermelon. Samples of watermelon continuous cropping soils were treated by RSD in laboratory tests and pot experiments in August 2015 and from December 10,2016 to April 10,2017. The soil samples for the laboratory test were divided into 16 groups,and each group comprised three parallel samples of 100 g（dry soil weight）. Except for the original and control（CK） samples,the 14 other groups of soil samples were treated with different combinations of 1% or 3% alfalfa powder,1% or 3% ammonia（NH3） water,and 1% or 3% acetic acid. The soil samples were placed inside size-five self-styled plastic bags and incubated in a constant-temperature biochemical incubator at 35°C for 14 days after blending,flooding,and sealing. Seven groups of soil samples were designed for the pot experiments based on the laboratory test results. Each group consisted of 30 parallel samples of 3 kg（dry soil weight）. These samples were incubated outdoors for 4 months after mixing with alfalfa powder and/or NH3 and/or acetic acid according to the experimental design,blending,flooding,and sealing. Watermelon seedlings were planted in the air-dried soil samples from May to July in 2017. The results showed that the p H of the soil samples treated by RSD were elevated except for those samples with acetic acid. In addition,the electrical conductivities of the soil samples treated by RSD were effectively adjusted. The presence of soil-borne pathogenic Fusarium oxysporum f.sp. niveum was significantly suppressed（p 0.05） in soil samples treated by RSD,and the incidence and mortality rate of watermelons planted in these samples were remarkably lower than those planted in the CK and flooded CK soil samples. Therefore,continuous cropping obstacle of watermelon can be controlled by RSD.