Effects of Fumigants and Systemic Pesticides on Pratylenchus penetrans and Potato Yield

Replicated trials were conducted near Alliston, Ontario, in 1983 and 1984 to evaluate the efficacy of five chemical treatments in controlling the root-lesion nematode Pratylenchus penetrans on potato, Solanum tuberosum cv. Russet Burbank. The fumigants Vorlex, at 55 liters product/ha, and Telone II B, at 75 liters product/ha, were more effective in suppressing high initial population densities of 18,320 and 50,880 P. penetrans/kg soil in 1983 and 1984, respectively, than single applications of the systemic pesticides Temik 10 G at 22 kg product/ha, Vydate L at 18 and 9 liters product/ha, and Furadan 10 G at 33 kg product/ha. The combination of Vorlex + Temik resulted in greatest nematode suppression and lowest populations at harvest. In 1983, marketable tuber yield (> 7 cm) in the Vorlex + Temik plots was 20.7 t/ha, compared to 4.7 t for the untreated check. Vorlex alone and Telone II B plots yielded 17.3 and 15.9 t/ha, respectively; Temik with 7.5 t also yielded better than the check. Vydate and Furadan did not influence yields significantly. Total yields differed from the check in all treatments except with Furadan. In 1984, marketable yields ranged from 15.5 t/ha for the Vorlex + Temik treatment to 11.2 for the untreated check, but the differences were not statistically significant. Total yields, however, were significantly increased by the fumigants. The difference in response to chemical treatment in the 2 years was attributed to greater heat stress and lack of supplementary irrigation in 1983.     

杀灭土壤中线虫对小麦生长和吸收N、P的影响

盆栽条件下研究了施用杀线剂(克线磷,67mg·kg^-1干土)和干热(105℃,2h)两种杀线措施对小麦生长和N、P养分吸收的影响。杀线剂对土壤中线虫的平均杀灭率约为80%, 干热处理的杀灭率为100%. 在杀线剂处理中,苗期至抽穗期小麦生物量、拔节期至成熟期植株含N量、全生育期植株吸N量以及抽穗和成熟期吸P量均显着低于对照。土壤干热处理后抽穗和成熟期小麦的生物量、含N量及N、P吸收量也比对照显着降低。两种杀线处理植株地上部生物量和N、P吸收量与相应处理全株变化趋势基本一致。但杀灭线虫对植株含P量影响较小。分析杀线虫后小麦生长和养分吸收受抑主要与土壤有机氮的矿化作用减弱、微生物活动产生的植物生长促进物质降低有关     

Genetic toxicology of 1,2-dibromo-3-chloropropane (DBCP)

1,2-Dibromo-3-chloropropane (DBCP) is a nematocide, which has been used extensively as a soil fumigant in agriculture. Since sterility was found among male workers involved in the manufacture of DBCP, great concern has been focused on the genetic hazards of DBCP. DBCP gave positive results in many tests such as microbial, in vitro cytogenetics, and Drosophila studies. In mammalian test systems, DBCP caused chromosomal aberrations in the bone marrow cells and dominant-lethal mutations in germ cells in rats. In mice, there were no signs of DBCP-induced heritable mutation in germ cells, although point mutations were detected in somatic cells. The occurrence of Y-chromosomal non-disjunction was indicated in DBCP-exposed male workers by an increased number of sperm containing 2 Y-chromosomes.     

Responses of Wheat Yield,Macro- and Micro-Nutrients,and Heavy Metals in Soil and Wheat following the Application of Manure Compost on the North China Plain

The recycling of livestock manure in cropping systems is considered to enhance soil fertility and crop productivity. However, there have been no systematic long-term studies of the effects of manure application on soil and crop macro- and micro-nutrients, heavy metals, and crop yields in China, despite their great importance for sustainable crop production and food safety. Thus, we conducted field experiments in a typical cereal crop production area of the North China Plain to investigate the effects of compost manure application rates on wheat yield, as well as on the macro-/micro-nutrients and heavy metals contents of soil and wheat. We found that compost application increased the soil total N and the available K, Fe, Zn, and Mn concentrations, whereas the available P in soil was not affected, and the available Cu decreased. In general, compost application had no significant effects on the grain yield, biomass, and harvest index of winter wheat. However, during 2012 and 2013, the N concentration decreased by 9% and 18% in straw, and by 16% and 12% in grain, respectively. With compost application, the straw P concentration only increased in 2012 but the grain P generally increased, while the straw K concentration tended to decrease and the grain K concentration increased in 2013. Compost application generally increased the Fe and Zn concentrations in straw and grain, whereas the Cu and Mn concentrations decreased significantly compared with the control. The heavy metal concentrations increased at some compost application rates, but they were still within the safe range. The balances of the macro-and micro-nutrients indicated that the removal of nutrients by wheat was compensated for by the addition of compost, whereas the level of N decreased without the application of compost. The daily intake levels of micronutrients via the consumption of wheat grain were still lower than the recommended levels when sheep manure compost was applied, except for that of Mn.     

The effect of DD nematocide on soil micro-organisms

The application of DD, a 1∶1 mixture of 1,3-dichloropropene and 1,2-dichloropropane, at field rate, to soil had neither stimulatory nor suppressive effects on bacteria, actinomycetes, fungi and cellulose decomposing bacteria. The toxic effect of the nematocide onAzotobacter and nitrogen-fixing clostridia was slight, the organisms recovering in a very short time. In fumigated soils the counts ofNitrosomonas andNitrobacter were markedly reduced and remained lower than the counts in the untreated soils for the 30 days duration of the experiment. The inhibitory effects of DD were to some extent influenced by soil type, being most marked in sandy and loam and least in calcareous soils.     

Synergistic Effects of Organic Contaminants and Soil Organic Matter on the Soil-Water Partitioning and Effectiveness of a Nonionic Surfactant (Triton X-100)

Napthalene- and decane-contaminated soils were treated with Triton X-100 (a nonionic surfactant) to characterize the soil-water partitioning behavior of the surfactant in soils with different organic content. Soil samples with different organic content were prepared by mixing sand-mulch mixtures at different proportions. The experimental results indicated that the amount of surfactant sorbed onto soil increased with increasing soil organic content and increasing surfactant concentration. The effective critical micelle concentration (CMC) also increased with increasing organic content in soil. The CMC of Triton X-100 in aqueous systems without soil was about 0.3 mM and the effective CMC values measured for soil-water-surfactant systems (approximately 1:19 soil/water ratio) with 25%, 50%, and 75% mulch content were 0.9, 1.0, and 1.7 mM, respectively. Sub-CMC surfactant sorption was modeled accurately with both the Freundlich and the linear isotherm. The maximum surfactant sorption onto soil varied from 66% to 82% of added surfactant in the absence of contaminant. The effective CMC values for Triton X-100 increased to some extent in the presence of contaminants, as did the maximum surfactant sorption. The maximum surfactant sorbed onto the soil with 75% mulch content increased from 82% for clean soils, to 95% and 96% for soils samples contaminated with naphthalene and decane, respectively.     

Nematocide activity of 6,7-diarylpteridines in three experimental models

The in vitro nematocide activity of seventeen 6,7-diarylpteridines has been tested using three different experimental models, Caenorhabditis elegans, Nippostrongylus brasiliensis and Heligmosomoides polygyrus. The method of evaluation of inhibition in the secretion of acetylcholinesterase by H. polygyrus seems to be the most indicated to avoid false positives. The in vivo activities, against Trichinella spiralis, of the most in vitro active pteridines have been assayed. All pteridine derivatives bearing 6,7-di-p-bromophenyl substituents have shown in vitro nematocide activities in the three experimental models used. Amongst all the pteridines tested in vivo, only 2,4-pteridinedithione derivatives exhibited moderate activity.     

Interaction of plastic mulch,pesticides and fungi in the control of soil-borne nematodes

Summary Three different mulching materials — hay, black polyethylene film, and translucent polyethylene film — produced different soil temperatures and thus influenced the microflora of the soil differently.Rhizoctonia solani Kuehn increased in cool or moderate temperatures under hay or black film but not in warmer soil beneath translucent film. Populations of a meadow nematode,Pratylenchus penetrans Cobb were reduced approximately two-thirds under the black film. Under this film conditions apparently favor biological control ofP. penetrans. Over several months this control was destroyed if a fungicide, pentachloronitrobenzene, and a nematocide, dibromochloropropane, were added. Evidently, the fungicide inhibited organisms predaceous onP. penetrans at the same time it inhibitedR. solani.     

利用海拔差异模拟增温对高山森林土壤溶解性有机碳和有机氮含量的影响

在2010年5月—2011年4月和2011年5月—2012年4月2个培养周期内,采用原状土柱野外控制试验,利用海拔梯度变化研究了温度增加对川西高山森林土壤溶解性有机碳(DOC)和有机氮(DON)动态的影响.结果表明: 经模拟增温处理(降低海拔)的土壤有机层和矿质土壤层DOC和DON含量在2个连续培养周期内的各关键时期均呈现明显的动态变化.海拔3300和3000 m样地比海拔3600 m 样地土层DOC含量分别增加6.8和26.6 mg·kg^-1.海拔3600、3300和3000 m样地土层DOC含量均在第1个培养周期的生长季末最高,分别为408.0、317.9和448.2 mg·kg^-1,在第2个培养周期的生长季节中期最低, 分别为33.1、32.4和36.5 mg·kg^-1.与海拔3600 m样地相比,海拔3300和3000 m样地土层DON含量分别增加2.3和30.4 mg·kg^-1.除海拔3000 m样地以外,海拔3600和3300 m样地土层DON含量在第1个培养周期内的生长季节中期最高,分别为65.9和64.6 mg·kg^-1,在第1个培养周期内的融化期最低,分别为31.9和37.1 mg·kg^-1.模拟增温处理增加了样地内土壤有机层DOC和DON含量,降低了矿质土壤层DOC含量、土壤有机层及矿质土壤层DOC/DON值.土壤有机层DOC/DON值与DOC含量呈显著正相关,与DON含量呈显著负相关;矿质土壤层DOC/DON值与DOC含量呈显著负相关,与DON含量呈显著正相关.未来全球气候变暖可能通过影响高寒森林土壤温度和冻融循环格局,增加整个土层DOC和DON含量,进而影响高寒森林土壤碳、氮循环过程.     

The role of mineral nutrients in the increased growth response of tomato plants in solarized soil

Soil solarization is a non-chemical disinfestation technique that frequently promotes plant growth in the absence of known major pathogens, a phenomenon termed increased growth response (IGR). The effect of solarization on plant nutrients and their role in the IGR was studied with tomato plants grown in solarized or non-solarized (control) sandy soil, under controlled conditions. Solarization considerably increased the soil concentrations of water extractable N, K, Ca, Mg and Na at most sites, whereas Cl and DTPA extractable Mn, Zn, Fe and Cu were decreased by the treatment. Plant growth and specific leaf area were enhanced in solarized as well as in N-supplemented control soil. In tomato plants grown in solarized soil, concentrations of most nutrients in the xylem sap, including N, were increased compared to the control, whereas Cl and SO4 levels decreased. The most significant increase in leaf nutrient concentration caused by soil solarization was recorded for N. Furthermore, leaf N concentration was highly and positively correlated with shoot growth. The concentration of Cu increased in leaves from the solarization vs. the control treatment, whereas that of SO4 and Cl decreased, the latter presumably below the critical toxicity level. The correlation between shoot growth and leaf concentration was positive for Cu and inverse for Cl and SO4. In conclusion, we found that soil solarization significantly affects nutrient composition in tomato plants, and provided strong evidence that N, and eventually also Cl, play a major role in IGR.     

硫对铅污染水稻土微生物活性及群落结构的影响

对含有不同浓度铅的水稻土添加硫代硫酸钠进行土培试验,研究硫作用下铅污染水稻土微生物活性及群落结构的变化.结果表明:添加硫底物后,土壤的氧化还原电位(Eh)升高,呼吸强度增强,硫氧化菌的数量显著增加.硫促进了土壤中硫氧化菌等微生物的生长并引起群落结构的变化,克隆测序表明,加硫处理下土壤微生物的特异性条带与拟杆菌、硫杆菌、β-变形菌和嗜酸菌具有很高的相似性.硫处理下土壤碳酸盐结合态及铁锰结合态铅含量发生了显著变化.     

镉污染对水稻土微生物量、酶活性及水稻生理指标的影响

水稻盆栽条件下,研究了外源Cd不同处理对土壤微生物学指标、土壤酶活性及部分水稻生理指标的影响.结果表明,土壤微生物量C和N开始随Cd浓度增加而上升,到一定浓度时则随Cd浓度增加而下降,其转折点因土壤性质有所差异.同时土壤酶活性变化规律与土壤微生物量C、N变化规律相似,但其转折点浓度因土壤类型及土壤酶种类不同而有差异.Cd污染后的变异系数依次为:脱氢酶＞酸性磷酸酶＞脲酶.土壤呼吸作用强度和代谢熵都随Cd浓度增大而缓慢增加.水稻叶绿素含量随Cd处理浓度增加表现出先上升后下降,其转折点受供试土壤性质不同而不同;脯氨酸含量与过氧化物酶活性随着Cd处理浓度增大而增加.Cd污染后水稻生理指标的变异系数在黄松田水稻土中依次为过氧化物酶活性＞叶绿素含量＞脯氨酸含量;黄红壤性水稻土中依次为过氧化物酶活性＞脯氨酸含量＞叶绿素含量.相关分析表明,种植水稻条件下Cd污染对土壤微生物量、酶活性及水稻生理指标的影响是相辅相成的.     

Changes of soil organic and inorganic carbon in relation to grassland degradation in Northern Tibet

The effect of livestock grazing on grassland degradation and the resulting impact on soil carbon concentration is an important factor in carbon estimation. We addressed this issue using field observations and laboratory analysis of samples from Tibetan grassland. Based on the field measurements, we investigated the soil organic carbon (SOC) and soil inorganic carbon (SIC) under two contrasting degradation states: lightly or non-degraded grasslands (LDG) and heavily degraded grasslands (HDG). We assessed their relationships with environmental factors using data collected from 99 sites across Northern Tibet during 2011–2012. Data were analyzed using a linear mixed-effects model and one-way ANOVA. The results showed that: (1) SOC concentration decreased and SIC concentration increased following grassland degradation, especially at soil depths in the range of 0–10 cm (P < 0.05); (2) the major environmental factors affecting SOC and SIC were soil pH and plant biomass; (3) spatially, the SOC density increased with the mean annual temperature and mean annual precipitation, whereas SIC exhibited the opposite trend; (4) the SOC density increased at first and then decreased with increasing grazing intensity, with an opposite trend in SIC; and (5) soil carbon storage in this region was 0.14 Pg smaller in the HDG than in the LDG. This study suggests that grassland degradation can significantly affect the vertical distribution and storage of SOC and SIC. The carbon sequestration capacity of the top 100 cm of soil in Northern Tibet was estimated as 0.14 Pg.     

The development of potential screens based on shoot calcium and iron concentrations for the evaluation of tolerance in Egyptian genotypes of white lupin (Lupinus albus L.) to limed soils

European cultivars of white lupin (Lupinus albus L.) grow poorly in limed or calcareous soils. However, Egyptian genotypes are grown successfully in highly calcareous soil and show no stress symptoms. To examine their physiological responses to alkaline soil and develop potential screens for tolerance, three experiments were conducted in limed and non-limed (neutral pH) soil. Measurements included net CO2 uptake, and the partitioning of Fe2+ and Fe3+ and soluble and insoluble Ca in stem and leaf tissue. Intolerant plants showed clear symptoms of stress, whereas stress in the Egyptian genotypes and in L pilosus Murr. (a tolerant species) was less marked. Only the intolerant plants became chlorotic and this contributed to their reduced net CO2 uptake in the limed soil. In contrast, Egyptian genotypes and L pilosus showed no change in net CO2 uptake between the soils. The partitioning of Ca and Fe either resulted from the stress responses, or was itself a stress response. L pilosus and some Egyptian genotypes differed in soluble Ca concentrations compared with the intolerant cultivars, although no significant difference was apparent in the Ca partitioning of the Egyptian genotype Giza 1. In a limed soil, Giza 1 maintained its stem Fe3+ concentration at a level comparable with that of plants grown in non-limed soil, whereas stem [Fe3+] of an intolerant genotype increased. Gizal increased the percentage of plant Fe that was Fe2+ in its leaf tissue under these conditions; that of the intolerant genotype was reduced. The potential tolerance of the Egyptian genotypes through these mechanisms and the possibility of nutritional-based screens are discussed.     

Immobilization and phytoavailability of cadmium in variable charge soils. III. Effect of biosolid compost addition

We examined the effect of biosolid compost on the adsorption and complexation of cadmium (Cd) in two soils (Egmont and Manawatu) which varied in their organic matter content. The effect of biosolid compost on the uptake of Cd from the Manawatu soil, treated with various levels of Cd (0–10 mg Cd kg^–1 soil), was also examined using mustard (Brassica juncea L.) plants. The transformation of Cd in soil was evaluated by a chemical fractionation scheme. Addition of biosolid compost increased negative charge in soil. The effect of biosolid compost on Cd adsorption varied between the soils, with a large portion of the sorbed Cd remaining in solution as an organic complex. Increasing addition of Cd increased Cd concentration in plants, resulting in decreased plant growth at high levels of Cd (i.e., phytotoxicity). Addition of biosolid compost was effective in reducing the phytotoxicity of Cd as indicated by the decrease in the concentration of NH₄OAc extractable-Cd and soil solution-Cd. The solid-phase fractionation study indicated that the addition of biosolid compost decreased the concentration of the soluble and exchangeable Cd fraction but increased the concentration of organic-bound Cd fraction in soil. Alleviation of Cd phytotoxicity by biosolid compost can be attributed primarily to complexation of Cd by the organic matter in the biosolid compost.     

铜污染旱地红壤的络合诱导植物修复作用

研究EDTA和低分子量有机酸对污染旱地红壤Cu形态变化及金属忍耐－富集型植物印度芥菜生长和Cu吸收的影响,以探讨Cu污染土壤的有机络合诱导植物吸取修复作用,结果表明,在芥菜营养生长旺盛期施用EDTA可显著提高土壤Cu的活性,土壤水浸提态Cu和交换态Cu均显著上升;这种活化效应随外加Cu浓度的上升和EDTA用量的增加而增大;柠檬酸和酸对土壤Cu的活化效应小,只对水浸提态Cu略有影响;EDTA可显著增加芥菜茎叶、根的Cu浓度和吸收量,等摩尔量柠檬酸和苹果酸对土壤铜形态变化和芥菜Cu吸收没有显著作用。     

植冠与土壤种子库储存种子的萌发特性及策略

为明确黄土丘陵沟壑区植物种子库如何调控种子萌发来提高个体适合度,选择研究区7种具有种子库的主要物种为研究对象,以刚成熟和室内储存种子为对照,比较植冠宿存(5个宿存期)和土壤埋藏(5a埋藏期)对植物种子萌发特性的影响,探讨植冠种子库与土壤种子库储存下的种子萌发策略。结果表明:7种植物种子经过不同种子库储存后萌发特性表现出明显的种间差异,黄刺玫(Rosa xanthina)和水栒子(Cotoneaster multiflorus)种子萌发力表现为植冠宿存不变型、土壤储存增强型,土壤储存明显提高水栒子种子萌发速率;达乌里胡枝子(Lespedeza davurica)和狼牙刺(Sophora davidii)种子萌发力表现为植冠宿存增强型、土壤储存减弱型,种子萌发历时表现为植冠宿存延长型,土壤种子库储存还可加快达乌里胡枝子萌发速率、缩短萌发历时;茭蒿(Artemisia giralaii)和铁杆蒿(Artemisia gmelinii),种子萌发率随植冠宿存时间先升高后降低,随土壤储存时间先降低后升高,土壤储存可推迟其萌发,铁杆蒿种子萌发速率在植冠与土壤储存后均加快;紫丁香(Syringa oblata)种子萌发率随植冠宿存先升高后降低,土壤储存明显加快其种子启动萌发与速率。在黄土丘陵沟壑区,植物种子经过植冠或土壤种子库储存,或增加、加快、提早萌发充分利用有利条件提高占据性,或减少、减缓、推迟萌发分摊不利条件的风险;而且该区植物植冠与土壤储存后种子萌发特性间的关系,体现各自适应环境与应对干扰的分工与协作策略,主要表现为:单一主导型和相辅相成型。     

秦岭火地塘真菌群落海拔分布格局

土壤真菌在自然生态系统的养分循环和土壤碳储存方面起重要作用。秦岭火地塘林区在不同海拔分布着不同的优势树种,但其相应的土壤特征及微生物群落的海拔分布格局仍不明晰。本研究分析了5个海拔处(1500、1700、1900、2100和2300 m)的土壤特征变化趋势,并在高通量测序基础上研究了真菌群落格局。结果表明: 土壤有效磷含量、pH值随海拔的增加而显著增加,土壤水分则呈下降趋势。土壤真菌Shannon多样性指数随海拔升高呈下降趋势,而ACE丰度指数相反;真菌优势门为担子菌门(68.2%)、子囊菌门(19.8%)和球囊菌门(1.7%),且随海拔升高整体呈现出“U”型或“单峰”变化格局;真菌优势纲为伞菌纲(64.2%)、粪壳菌纲(5.8%)和锤舌菌纲(4.1%)。冗余分析(RDA)表明,土壤特性解释了土壤真菌群落总变异的89.1%,其中土壤有效磷含量、pH和海拔是土壤真菌群落海拔梯度变化的主要驱动因子。在秦岭火地塘林区,土壤特征在海拔梯度上的差异性影响了土壤真菌群落组成。     

Signalling mechanisms involved in the response of two varieties of Humulus lupulus L. to soil drying: I. changes in xylem sap pH and the concentrations of abscisic acid and anions

Background and aims

Soil drying leads to the generation of chemical signals in plants that regulate water use via control of the stomatal aperture. The aim of our work was to identify the presence and identity of potential chemical signals, their dynamics, and their relationship with transpiration rate during soil drying in hop (Humulus lupulus (L.)) plants.

Methods

We used pressure chamber technique for measurement of shoot water potential and collection of shoot xylem sap. We analyzed concentrations of abscisic acid (ABA), nitrate, phosphate, sulphate and malate in sap and also the rate of whole plant transpiration.

Results

Transpiration rate decreased prior to changes in shoot water potential. The concentration of ABA in xylem sap continuously increased from early to later stages of water stress, whereas in leaves it increased only at later stages. Shoot sap pH increased simultaneously with the decrease of transpiration rate. Xylem sap alkalization was in some cases accompanied by a decrease in nitrate concentration and an increase in malate concentration. Concentration of sulphate increased in xylem sap during drying and sulphate in combination with a higher ABA concentration enhanced stomatal closure.

Conclusions

Several early chemical signals appear in sap of hop plants during soil drying and their impact on transpiration may vary according to the stage of soil drying.