菲对秀丽隐杆线虫、中杆属和拟丽突属线虫毒性效应研究

采用悉生培养系统,研究不同浓度菲对秀丽隐杆线虫、拟丽突属与中杆属线虫的毒性效应,以及3种线虫对菲的去除作用。结果表明:(1)随着菲浓度的增加,3种线虫存活率逐渐降低。秀丽隐杆线虫在不添加菲的处理中,48 h内出现繁殖,而在添加菲的处理中,即使在最低浓度5 mg/L下,繁殖现象也会消失。中杆属与拟丽突属线虫由于世代时间较长,在本试验周期内均未出现繁殖现象。(2)暴露24 h时,比较不同浓度菲处理下线虫的相对死亡率,得到3种线虫的耐性依次为中杆属线虫≥秀丽隐杆线虫≥拟丽突属线虫,且随菲浓度的增加,秀丽隐杆线虫耐性水平逐渐降低;暴露48 h时中杆属线虫耐性依旧高于拟丽突属,而72 h时中杆属与拟丽突属线虫的耐性趋于一致。(3)3种线虫受菲胁迫后均失去头部正常摆动能力,且秀丽隐杆线虫与拟丽突属线虫体长随菲浓度的增加而逐渐降低。(4)不同种类线虫的添加均能促进菲的去除,不同线虫之间无显著差异。因此,菲会显著抑制3种线虫的存活率和生长发育,抑制秀丽隐杆线虫的繁殖。线虫的存活率受线虫种类、暴露时间、菲浓度及其交互作用的影响显著,其中中杆属线虫对菲的综合耐性最强,3种线虫均能促进溶液中菲的去除。     

Tillage effects on cassava (Manihot esculenta) production and some soil properties

Cassava is traditionally grown on tilled soils. Interest in reduced-tillage systems is increasing in the humid tropics due to erosion problems. A field study was conducted on a sandy clay loam Ultisol to compare cassava performance in three tillage systems effects on soil water and organic carbon content. Tillage treatments were: (1) ploughing, harrowing and ridging (conventional); (2) digger-made holes (minimum); (3) pushing the sharpened end of cassavs cuttigs directly into the soil (no-till). Tillage did not affect total biomass yields in the first year. In the second year, significant differences were obtained in the yield of tops but not of fresh roots. No-till and minimum tillage out-yielded the conventional system by 40% and 23%, respectively, in the yield of tops,. It was apparent that elimination of ploughing did not reduce total biomass yield. Soil moisture contents in no-till and minimum tillage were significantly higher (P = 0.05) than in the conventional-tillage system. Conv organic carbon decresed significantly (P = 0.01) over time in all tillage systems. Conventional tillage gave the highest reduction. Cassava may be grown successfully in reduced-tillage systems in Ultisols of the humid tropics.     

耕作措施对农田黑土入渗速率的影响

应用田间长期定位试验，研究了5种耕作措施对东北农田黑土入渗速率的影响。结果表明，传统耕作为代表的平翻和旋松耕作的垄台容重最小，表层土壤稳定入渗速率高于其它3种耕作措施，分别为9．20mm／min和7．31mm／min。免耕垄台和垄沟的容重虽较高，但均具有较高的稳定入渗速率。在夏季进行垄沟深松少耕，可显著提高垄沟的稳定入渗速率。免耕和少耕是高效的水土保持耕作措施。     

Tillage, mulch and irrigation effects on corn (Zea mays L.) in relation to evaporative demand

The effects of deep tillage, straw mulching, and irrigation on corn (Zea mays L.) yield on a loamy sand (mixed, hyperthermic, Typic Ustipsamment) were studied for early (high evaporativity) and normally sown (relatively low evaporativity) crop for 3 years in a semi-arid sub-tropical monsoon region at Punjab Agricultural University, Ludhiana, India. Treatments included all combinations of two tillage systems (conventional tillage — harrowing the soil to a 10-cm depth; deep tillage — chiselling 40 cm deep, 35–40 cm apart), two irrigation regimes (75 mm irrigation when net open pan evaporation accumulated to 75 mm or 50 mm), and two straw mulch rates (0 and 6 Mg ha⁻¹).

Deep tillage significantly reduced soil strength (cone index) and caused deeper and denser rooting than conventional tillage, more so in the dry season and with the infrequent irrigation regime than in the wet season and frequent irrigation regime. Mulch also improved rooting by influencing the hydrothermal regime of the soil. Better rooting with deep tillage and/or mulch helped the crop to extract stored soil water more efficiently, which was reflected in a favourable plant water status (indicated by canopy temperature). Averaged across years, irrigation, and mulch, deep tillage increased grain yield by 1.6 Mg ha⁻¹ for the early season and 0.5 Mg ha⁻¹ for the normal season crop over the yield of 2.0 Mg ha⁻¹ achieved with conventional tillage regardless of season. Yield increase with mulching was also greater for the early season crop. Crop response to deep tillage and mulching was generally linked to the interplay between water supply (rain + irrigation) and demand (seasonal evaporativity) during the growing season. Increasing irrigation frequency increased crop yield when evaporativity exceeded rainfall early in the growing season. The results show that higher corn yields on coarse-textured soils in these regions may be achieved by advancing the seeding time and by using a proper combination of deep tillage, mulch, and irrigation.     

不同耕作方式土壤结构季节变化

试验于2011年通过对玉米全生育期土壤容重和团聚体的测定,分析4种黑土农田耕作方式土壤结构季节变化。结果表明:从播种到收获,传统耕作平翻(MT)和旋松(Rot)在0~20 cm土层土壤容重逐渐增大。保护性耕作少耕(RT)垄沟深松后(6月)土壤容重降低且显著低于其他耕作方式,免耕(NT)土壤容重季节差异不显著。各耕作方式1~2 mm与0.25~0.5 mm粒级团聚体季节差异不显著,2 mm团聚体平均含量表现为NTRTMTRot,且NT更容易形成5 mm团聚体。各耕作方式0.25 mm水稳定性团聚体数量(WR0.25)均随时间推移逐渐减少。MT土壤团聚体平均重量直径(MWD)季节差异不显著,10~20 cm土层几何平均直径(GMD)则表现为降低趋势,分形维数随时间推移表现出先增加后降低趋势。Rot的MWD和GMD季节变化均较小。在0~10 cm土层,RT的MWD与GMD先增加后降低,分形维数季节性变幅较大。NT处理8月份土壤团聚体的MWD和GMD最大,在0~20 cm土层,NT方式下WR0.25、MWD和GMD均大于其他耕作方式,而分形维数则小于其他耕作方式且季节变化差异不显著,NT土壤结构季节变化更稳定。     

Effect of Tillage Systems and Axle Load on Undisturbed Soil Hydraulic Properties

The effects of tillage treatment and axle load resulting from wheeled traffic on tilled soil (0 to 20 cm) were evaluated by measuring the changes in soil physical properties (bulk density and infiltration rate) and by measuring the impact on water retention in comparison with controlled plots. Data obtained from the experimental plots showed that infiltration rate was strongly affected by tillage treatments in 0‐ to 20‐cm depths. Dry bulk density was affected in 0‐ to 20‐cm depths by tillage treatments and axle load. Tillage system changed the ability of the soils to hold moisture and decreased the plant‐available water capacity.     

Tillage induced differential morphometric responses and growth patterns in afforestation with Quercus ilex

This study describes the changes in height and diameter in Quercus ilex trees grown on agricultural land in a semi-arid Mediterranean climate, in response to different soil management practices: mechanical weeding (MW), chemical weeding (CHW) and no treatment (NT); and compares trees grown from 1-year-old saplings and from acorns. After 6 years, trees that had been mechanically weeded were largest; for trees grown from saplings the average height was 120 cm and diameter was 3.83 cm, for trees grown from acorns average height was 100 cm and diameter was 2.56 cm. Soil organic matter increased in all managed plots while phosphorus, nitrate, and water content oscillated between years. The no treatment plot had the highest values for nitrate and organic matter while the chemical weeding plot had the highest level of phosphorus. Annual mean on C/N ratios were higher in the mechanical weeding (12.6 ± 3.3) followed by the chemical weeding (12.0 ± 1.6). Also mechanical weeding treatment showed the lowest soil water content throughout the study. An old tillage-induced compaction zone appeared in all plots at a depth of 12.5–17.5 cm with mechanical weeding causing the greatest compaction. However, no relationships were found with tree heights, neither with spatial compaction zoning. All trees showed the same growth pattern, whether raised from saplings or acorns and irrespective of soil management system. The height and diameter of trees were linked to the sum of height and diameter ratios from previous years. Our study shows that soil management does influence tree growth rate. Mechanical weeding should be considered for afforestation of agricultural lands with Q. ilex in semiarid Mediterranean lands.     

The Impact of No-Till,Conservation, and Conventional Tillage Systems on Erosion and Soil Properties in Lower Austria

Eurasian Soil Science - The effect of long-term (about 25 years) use of different farming practices on a set of soil properties and development of erosion in Lower Austria has been studied. Three...     

长期向上耕作对坡耕地土壤水稳定性团聚体的影响

为了研究耕作侵蚀对坡耕地不同景观位置内土壤结构稳定性的影响。以常规顺坡向下耕作和长期向上耕作的坡耕地为研究对象,通过对土壤水稳定性团聚体、有机碳含量等指标的测定,分析了不同耕作方式引起土壤不同分布模式对水稳性团聚体特征空间变异性的影响。结果表明:长期向上耕作平均质量直径值(MWD)在不同景观位置均高于常规向下耕作。在坡耕地1m和20m位置,向上耕作MWD比向下耕作分别显著(p0.05)增加了31.94%,23.54%,在5,10,15 m位置分别增加了0.87%,2.99%,3.03%。几何平均直径值(GMD)和0.25 mm水稳性团聚体(WSA0.25)的变化趋势与MWD类似。两种不同耕作方式引起土壤结构特征显著变化主要发生在坡顶和坡底位置,而中坡仅仅起类似于传送带的作用传输来自上坡(向下耕作)或下坡(向上耕作)的土壤。向上耕作比向下耕作的团聚体破坏率(PAD)值降低了25.29%,表明向上耕作显著减少了对大团聚体(0.25mm)的破坏程度。结果显示长期向上耕作显著减少了耕作侵蚀,增加了土壤结构稳定性。     

保护性耕作对麦-豆轮作土壤有机碳全氮及微生物量碳氮的影响

通过设置在甘肃省定西市李家堡镇的保护性耕作措施长期定位试验,共设4个处理（T：传统耕作;NT：免耕无覆盖;TS：传统耕作＋秸秆还田;NTS：免耕＋秸秆覆盖）,采用春小麦豌豆双序列轮作（即小麦→豌豆→小麦和豌豆→小麦→豌豆,本文中所指春小麦地、豌豆地分别指2008年种植春小麦、豌豆的轮作次序）,于2008年3月中旬对春小麦、豌豆双序列轮作下的土壤有机碳、全氮、土壤微生物量碳及土壤微生物量氮含量进行了采样测定。结果表明,经过7a的轮作后,两种轮作次序下,0-30cm土层中土壤有机碳、全氮、土壤微生物量碳、土壤微生物量氮含量均有在免耕＋秸秆覆盖、传统耕作＋秸秆还田处理较免耕不覆盖、传统耕作处理高的趋势,且其含量均随着土壤深度的增加而降低。其中,土壤微生物量碳含量在两种轮作次序下的排序均为：免耕＋秸秆覆盖（NTS）〉传统耕作＋秸秆还田（TS）〉免耕不覆盖（NT）〉传统耕作（T）;而土壤微生物量氮含量在春小麦地和豌豆地的排序则分别表现为：免耕＋秸秆覆盖（NTS）〉传统耕作＋秸秆还田（TS）〉传统耕作（T）〉免耕不覆盖（NT）和免耕＋秸秆覆盖（NTS）〉传统耕作＋秸秆还田（TS）〉免耕不覆盖（NT）〉传统耕作（T）。同时,微生物量碳、微生物量氮与有机碳和全氮均呈显著正相关,说明提高土壤有机质、全氮含量的保护性耕作模式有利于土壤微生物量碳与氮的积累。     

Effect of No‐Tillage and Conventional Tillage Systems on the Chemical Composition of Soil Solid Phase and Soil Solution of Brazilian Savanna Oxisols

No‐tillage (NT) cropping systems are becoming increasingly important in the Brazilian savanna. To evaluate their sustainability we compared soil chemical properties in 1‐ to 3‐year‐old NT systems following 9 to 11 years of conventional tillage (CT) with systems where CT was continuously in place for 12 years. In the rainy season 1997/98, NT was cropped with soybean and CT with corn while in the rainy season 1998/99 both systems were cropped with soybean. Soil solid phase samples were taken from the 0—0.15, 0.15—0.3, 0.3—0.8, 0.8—1.2, and 1.2—2 m layers on three spatially separated plots under each of NT and CT. Soil solution samples were collected weekly at 0.15, 0.3, 0.8, 1.2, and 2 m soil depth during two rainy seasons (14 October to 28 April 1997/98 and 1998/99). We determined soil moisture contents, pH, the concentrations of exchangeable cations, the electrical conductivity (EC) of the soil solution, and the concentrations of Al, C, Ca, Cl^—, K, Mg, Mn, Na, NH₄⁺, NO₃^—, P, S, and Zn in solid soil and soil solution samples. Differences in soil solid phase properties and moisture content between NT and CT were small, few were significant. Under NT, the average solution pH was significantly lower (5.5), Al (26 μg l^—1), Mn (17 μg l^—1) and total organic C concentrations (TOC, 6.5 mg l^—1) were higher than under CT (pH: 6.0, Al: 14μg l ⁻¹, Mn: 14μg l ⁻¹, TOC: 5.5 mg l ⁻¹). Irrespective of the different crops in the first rainy season, under NT, the EC (205 μS cm^—1), Ca (17 mg l^—1), and Mg (2.9 mg l^—1) concentrations at 0—0.3 m depth were lower than under CT (EC: 224 μS cm^—1, Ca: 25 mg l^—1, Mg: 5.6 mg l^—1). At 1.2—2 m depth, the reverse order was observed (EC: 124 μS cm^—1 under NT and 84 μS cm^—1 under CT, Ca: 11 mg l^—1 under NT and 7.5 mg l^—1 under CT, Mg: 3.1 mg l^—1 under NT and 1.8 mg l^—1 under CT). Our results indicate that enhanced soil acidification because of higher rates of organic matter mineralization and a more pronounced nutrient leaching because of increased pore continuity may limit the sustainability of NT.     

Analysis of clonal germplasm from five Saccharum species: S. barberi , S. robustum, S. officinarum, S. sinense and S. spontaneum . A study of inter- and intra species relationships using microsatellite markers

In order to study relationships within and among species of the highly complex polyploid genus Saccharum, 30 clones from 5 species (S. barberi, S. officinarum, S. robustum, S. sinense, and S. spontaneum) and 6 cultivated clones were analyzed using 15 sugarcane simple sequence repeat (SSR) markers and two multivariate statistical methods. The origins of two species, S. barberi and S. sinense, are unclear, and it has been hypothesized that they arose from crosses of S. officinarum × S. spontaneum. S. robustum is suggested to be ancestral to S. officinarum, which, when crossed with S. spontaneum, principally comprise the genomes of commercial cultivars. Although our analyses supported S. robustum as being an ancestor of S. officinarum, and show the composition of commercial clones as expected, our results concerning the species S. barberi and S. sinense indicated them to be much less related to the main Saccharum germplasm pool than previous molecular marker investigations, suggesting that introgression from other genera may exist in their ancestry. The differing results of our analysis of S. barberi and S. sinense are likely attributable to more equal and larger numbers of clones studied in each species. Given the extremely high ploidy, the use of only 15 SSR markers enabled clear distinction of Saccharum species and clones, and also identified likely mislabeled accessions. In addition, the replication of DNA extraction, polymerase chain reactions, and fragment electrophoresis increased the robustness of our analysis.     

Oleaster (var. sylvestris) and subsp. cuspidata are suitable genetic resources for improvement of the olive (Olea europaea subsp. europaea var. europaea)

The olive belongs to Olea, a complex genus and to a species with six subspecies. Subsp. europaea includes both the cultivated olive and the oleaster, the wild ancestor of the olive. Little is known on the phenotype of fruits from subsp. cuspidata. We aimed to compare europaea and cuspidata trees for oil content and composition and to verify whether natural hybrids may exist between the two subspecies. Specimens were from Kenya and putative natural hybrids between cuspidata and europaea were from Stellenbosch (South Africa). Cultivar and oleaster trees were sampled in France (continental and Corsica), Italy (Continental and Sardinia) and Tunisia. We have examined the fruit (drupe) structure between subsp. cuspidata and europaea and extracted oil from the pulp, seed and total drupe. Comparison for oil content was made between the cultivated olive and the oleaster and some cuspidata trees from Kenya. A few of cuspidata individuals from Botanical gardens do not enable phenotyping for oil content and composition. Oil composition analyses were performed for the main fatty acids to compare the three taxa. We used microsatellite markers at 11 loci to compute genetic distances between cuspidata, oleaster and cultivar trees and to reveal eventual hybrids. The SSR polymorphisms were huge between the two subspecies and they revealed that putative hybrids were true hybrids sampled around olive orchards. The whole comparison of oil content shows that olive cultivars display higher oil content than the subsp. cuspidata and that the oleaster trees are intermediate, whereas for oil composition of the drupe, cuspidata from Kenya shows less oleic acid than europaea. However, the cuspidata trees show seed oil composition similarities with the other two taxa. The discussion deals with possible reasons to explain the differences and of the possible uses of these taxa for breeding both the olive and brown olive. H. Hannachi and H. Sommerlatte have equal contribution in the article.     

耕作方式对紫色水稻土颗粒态氮的影响

土壤颗粒态氮作为土壤有机氮中的非稳定性部分,对土壤中氮的平衡有着重要的影响,对作物的生长及增产增收也有着重要意义.试验以西南大学农业部重庆紫色土生态环境重点野外科学观测试验站内于1989年设立的长期免耕试验田为研究对象,研究冬水田平作、水旱轮作、垄作免耕和垄作翻耕等耕作方式对土壤颗粒态氮的影响.结果表明,不同耕作方式下土壤全氮及颗粒态氮含量均具有明显的垂直分布特征,由上到下含量逐渐降低.在0-60 cm的土壤深度内,土壤全氮平均含量依次为垄作免耕(1.53g/kg)>冬水田平作(1.50 g/kg)>垄作翻耕(1.31 g/kg)>水旱轮作(1.16 g/kg);颗粒态氮平均含量依次为冬水田平作(0.55 g/kg)>垄作免耕(0.46 g/kg)>垄作翻耕(0.40 g/kg)>水旱轮作(0.35 g/kg).免耕能够增加土壤全氮含量,但无助于颗粒态氮含量的增加.不同耕作方式下的颗粒态土碳氮比大于全土碳氮比,表明颗粒态土壤有机质易被微生物分解,是土壤营养物质的重要来源.     

氮、磷、钾施用量及其配比对白芷产量的影响

采用三元二次回归正交组合设计,试验研究N、P、K施用量及其配比对白芷产量的影响结果表明,白芷产量与N、P、K的供应均为正效应,N、P、K单施低于零水平时,随施用量的增加而白芷产量逐步提高,N、P、K配合施用比单施的产量高。