不同模拟雨量下耕作措施对夏玉米水分利用效率和产量的影响

基于西北夏玉米生产实际和降雨特征,用自制模拟降雨器,于2010年6-9月研究了250、350和450 mm模拟雨量下翻耕、免耕、免耕覆盖对夏玉米农田水分利用效率及产量的影响.结果表明： 在6-9月250 mm雨量下免耕水分利用效率比翻耕高26%,产量比翻耕高16.5%;350 mm雨量下免耕水分利用效率和产量分别比翻耕高17.6%和6.1%;在450 mm雨量下免耕的蓄水效应低于翻耕,水分利用效率比翻耕低1.1%,产量比翻耕低0.6%.免耕覆盖克服了免耕在雨量充沛时水分蓄积量低于翻耕的缺点,在3种雨量下均可有效抑制棵间蒸发,减少翻耕地表裸露造成的无效水分消耗,增加土层贮水量,增大蒸腾量占水分消耗的比例,250 mm雨量下免耕覆盖水分利用效率比翻耕高48.6%,产量比翻耕高32.9%;350 mm雨量下免耕覆盖水分利用效率比翻耕高51.6%,产量比翻耕高27.1%;450 mm雨量下免耕覆盖水分利用效率比翻耕高23.7%,产量比翻耕高13.1%.综上,免耕夏玉米在250和350 mm雨量下相对于翻耕有增产和提高水分利用效率的优势,免耕覆盖夏玉米在250、450 mm雨量下产量和水分利用效率显著高于翻耕.     

不同模拟雨量下耕作措施对夏玉米水分利用效率和产量的影响

基于西北夏玉米生产实际和降雨特征,用自制模拟降雨器,于2010年6-9月研究了250、350和450 mm模拟雨量下翻耕、免耕、免耕覆盖对夏玉米农田水分利用效率及产量的影响.结果表明： 在6-9月250 mm雨量下免耕水分利用效率比翻耕高26%,产量比翻耕高16.5%;350 mm雨量下免耕水分利用效率和产量分别比翻耕高17.6%和6.1%;在450 mm雨量下免耕的蓄水效应低于翻耕,水分利用效率比翻耕低1.1%,产量比翻耕低0.6%.免耕覆盖克服了免耕在雨量充沛时水分蓄积量低于翻耕的缺点,在3种雨量下均可有效抑制棵间蒸发,减少翻耕地表裸露造成的无效水分消耗,增加土层贮水量,增大蒸腾量占水分消耗的比例,250 mm雨量下免耕覆盖水分利用效率比翻耕高48.6%,产量比翻耕高32.9%;350 mm雨量下免耕覆盖水分利用效率比翻耕高51.6%,产量比翻耕高27.1%;450 mm雨量下免耕覆盖水分利用效率比翻耕高23.7%,产量比翻耕高13.1%.综上,免耕夏玉米在250和350 mm雨量下相对于翻耕有增产和提高水分利用效率的优势,免耕覆盖夏玉米在250、450 mm雨量下产量和水分利用效率显著高于翻耕.     

Influence of mulching on the pattern of growth and water use by spring wheat and moisture storage on a fine textured soil

Eight tonnes ha^–1 of stubble were used to mulch spring wheat (Triticum aestivum) on a fine textured soil with the aim of controlling both transpiration and soil evaporation during the wet pre-anthesis phase to increase moisture supply during grain filling in the eastern wheatbelt of Western Australia. Mulching reduced leaf area per plant by reducing the culm number; consequently the green area index was reduced. Reduced culm number was associated with low soil temperature which at 50 mm depth averaged 7°C lower under the mulched crop relative to the control crop in mid-season. The smaller canopies of the mulched crop used 15 mm less water than those of the control before anthesis; this difference in water-use was due equally to reduced transpiration and soil evaporation. However, the mulched crop was unable to increase ET during grain filling, a response associated with the persistence of low soil temperature for most of the growth period. Hence, total ET for the season was significantly lower (18 mm) under the mulched crop than the control crop. At harvest, mulching did not have significant effects on total above-ground dry matter and grain yields, but it increased water use efficiency for grain yield by 18%, grain weight by almost 17% and available moisture in both uncropped and cropped plots by an average of 43 mm.To determine whether there was any residual effects of soil treatment on moisture storage during the summer fallow period, soil moisture was monitored both in cropped plots and uncropped plots, that were either mulched or unmulched during the growing season, from harvest in October 1988 until next planting in June 1989. Available moisture at next planting was correlated with moisture storage at harvest despite the differences in run-off, soil evaporation and fallowing efficiency (increase in moisture storage as a percentage of rainfall) between treatments during fallowing. Therefore, the mulched treatments had more moisture available (30 mm), mostly as a result of less water use during cropping in the previous growing season, than the unmulched treatment.The study shows that mulching may be used to restrain both transpiration and soil evaporation early in the season to increase availability of soil moisture during grain filling. Secondly, mulching during the previous growing season had little effect on soil moisture during the summer fallow period, however, the moisture saved by mulching during cropping was conserved for the following season. These results indicate the importance of evaluating mulching of winter crops in terms of crop yield in the subsequent growing season as well as in the current season in which the soil was treated.Abbreviations D through drainage - DAS days after sowing of the crop on 31 May 1988 - DM dry matter produced in the above-ground portion of the crop (kg ha^–1) - E₀ evaporation from Class A pan (mm) - E_s evaporation from uncropped soil (mm) - E_sc evaporation from soil beneath the wheat canopy (mm) - ET evapotranspiration (mm) - FE fallowing efficiency (gain in soil moisture storage/rainfall) - GAI green area index (area of green vegetation per unit land area) - GWUE water-use efficiency for grain production (grain yield/total ET, kg ha^–1mm^–1) - K extinction coefficient (see equation 1) - RO run-off of moisture from soil surface during/following rainfall (mm) - SM available soil moisture (mm) at harvest (SMh) or at planting (SMp) - WUE water-use efficiency for total above-ground dry matter yield (see GWUE)     

Yield and yield components of maize and soil physical properties as affected by tillage practices and organic mulching

Maize (Zea mays L.) is an important grains cereal crop. Lots of farmers using tillage and mulching practices influence the final yield, to maintain up with the growing demand for food, fuel and feed. Field experiments were conducted to investigate the effects of tillage practices (i.e. conventional tillage CT, reduced tillage RT, deep tillage DT) and wheat straw mulching (i.e. no mulch and wheat straw mulch of 4, 8 and 12 Mg ha⁻¹, SM0, SM1, SM2 and SM3 respectively) on the growth, yield and yield components of maize and some of soil physical properties. The results showed that compared with RT, DT and CT decreased soil bulk density, as well as led to increase soil water content. Application of mulch treatments increased soil water content. DT and CT have been associated with greater plant height, yield components, grain and biomass yield than RT treatment. Plant height, yield components, grain and biomass yield as well as soil water content increased following mulching treatments. Mulching treatment of SM2 had the largest positive effects on maize yield. DT and CT that have potential to break the compacted zone in soil leading to a better soil environment and crop yield. The application of wheat straw mulch could be an efficient soil management practice for corn production in arid subtropical climate region.     

Effects of Conservation Tillage on Topsoil Microbial Metabolic Characteristics and Organic Carbon within Aggregates under a Rice (Oryza sativa L.) –Wheat (Triticum aestivum L.) Cropping System in Central China

Investigating microbial metabolic characteristics and soil organic carbon (SOC) within aggregates and their relationships under conservation tillage may be useful in revealing the mechanism of SOC sequestration in conservation tillage systems. However, limited studies have been conducted to investigate the relationship between SOC and microbial metabolic characteristics within aggregate fractions under conservation tillage. We hypothesized that close relationships can exist between SOC and microbial metabolic characteristics within aggregates under conservation tillage. In this study, a field experiment was conducted from June 2011 to June 2013 following a split-plot design of a randomized complete block with tillage practices [conventional intensive tillage (CT) and no tillage (NT)] as main plots and straw returning methods [preceding crop residue returning (S, 2100−2500 kg C ha⁻¹) and removal (NS, 0 kg C ha^-1)] as subplots with three replications. The objective of this study was to reveal the effects of tillage practices and residue-returning methods on topsoil microbial metabolic characteristics and organic carbon (SOC) fractions within aggregates and their relationships under a rice–wheat cropping system in central China. Microbial metabolic characteristics investigated using the Biolog system was examined within two aggregate fractions (>0.25 and <0.25 mm). NT treatments significantly increased SOC concentration of bulk soil, >0.25 aggregate, and <0.25 mm aggregate in the 0−5 cm soil layer by 5.8%, 6.8% and 7.9% relative to CT treatments, respectively. S treatments had higher SOC concentration of bulk soil (12.9%), >0.25 mm aggregate (11.3%), and <0.25 mm aggregate (14.1%) than NS treatments. Compared with CT treatments, NT treatments increased MBC by 11.2%, 11.5%, and 20%, and dissolved organic carbon (DOC) concentration by 15.5%, 29.5%, and 14.1% of bulk soil, >0.25 mm aggregate, and <0.25 mm aggregate in the 0−5 cm soil layer, respectively. Compared with NS treatments, S treatments significantly increased MBC by 29.8%, 30.2%, and 24.1%, and DOC concentration by 23.2%, 25.0%, and 37.5% of bulk soil, >0.25 mm aggregate, and <0.25 mm aggregate in the 0−5 cm soil layer, respectively. Conservation tillage (NT and S) increased microbial metabolic activities and Shannon index in >0.25 and <0.25 mm aggregates in the 0−5 cm soil layer. Redundancy analysis showed that the SOC and its fractions (DOC and MBC) were closely correlated with microbial metabolic activities. Structural equation modelling showed that the increase in microbial metabolic activities directly improved SOC by promoting DOC in >0.25 mm aggregate in the upper (0−5 cm) soil layer under conservation tillage systems, as well as directly and indirectly by promoting DOC and MBC in <0.25 mm aggregate. Our results suggested that conservation tillage increased SOC in aggregates in the topsoil by improving microbial metabolic activities.     

Sediment Delivery Ratio of Single Flood Events and the Influencing Factors in a Headwater Basin of the Chinese Loess Plateau

Little is known about the sediment delivery of single flood events although it has been well known that the sediment delivery ratio at the inter-annual time scale is close to 1 in the Chinese Loess Plateau. This study examined the sediment delivery of single flood events and the influencing factors in a headwater basin of the Loess Plateau, where hyperconcentrated flows are dominant. Data observed from plot to subwatershed over the period from 1959 to 1969 were presented. Sediment delivery ratio of a single event (SDR _e) was calculated as the ratio of sediment output from the subwatershed to sediment input into the channel. It was found that SDR _e varies greatly for small events (runoff depth <5 mm or rainfall depth <30 mm) and remains fairly constant (approximately between 1.1 and 1.3) for large events (runoff depth >5 mm or rainfall depth >30 mm). We examined 11 factors of rainfall (rainfall amount, rainfall intensity, rainfall kinetic energy, rainfall erosivity and rainfall duration), flood (area-specific sediment yield, runoff depth, peak flow discharge, peak sediment concentration and flood duration) and antecedent land surface (antecedent precipitation) in relation to SDR _e. Only the peak sediment concentration significantly correlates with SDR _e. Contrary to popular belief, channel scour tends to occur in cases of higher peak sediment concentrations. Because small events also have chances to attain a high sediment concentration, many small events (rainfall depth <20 mm) are characterized by channel scour with an SDR _e larger than 1. Such observations can be related to hyperconcentrated flows, which behave quite differently from normal stream flows. Our finding that large events have a nearly constant SDR _e is useful for sediment yield predictions in the Loess Plateau and other regions where hyperconcentrated flows are well developed.     

Grain Yield and Water Use Efficiency in Extremely-Late Sown Winter Wheat Cultivars under Two Irrigation Regimes in the North China Plain

Wheat production is threatened by water shortages and groundwater over-draft in the North China Plain (NCP). In recent years, winter wheat has been increasingly sown extremely late in early to mid-November after harvesting cotton or pepper. To improve water use efficiency (WUE) and guide the extremely late sowing practices, a 3-year field experiment was conducted under two irrigation regimes (W1, one-irrigation, 75 mm at jointing; W2, two-irrigation, 75 mm at jointing and 75 mm at anthesis) in 3 cultivars differing in spike size (HS4399, small spike; JM22, medium spike; WM8, large spike). Wheat was sown in early to mid-November at a high seeding rate of 800–850 seeds m⁻². Average yields of 7.42 t ha⁻¹ and WUE of 1.84 kg m⁻³ were achieved with an average seasonal evapotranspiration (ET) of 404 mm. Compared with W2, wheat under W1 did not have yield penalty in 2 of 3 years, and had 7.9% lower seasonal ET and 7.5% higher WUE. The higher WUE and stable yield under W1 was associated with higher 1000-grain weight (TGW) and harvest index (HI). Among the 3 cultivars, JM22 had 5.9%–8.9% higher yield and 4.2%–9.3% higher WUE than WM8 and HS4399. The higher yield in JM22 was attributed mainly to higher HI and TGW due to increased post-anthesis biomass and deeper seasonal soil water extraction. In conclusion, one-irrigation with a medium-sized spike cultivar JM22 could be a useful strategy to maintain yield and high WUE in extremely late-sown winter wheat at a high seeding rate in the NCP.     

极端干旱条件下燕麦垄沟覆盖系统水生态过程

围绕极端气候条件下沟垄沟覆盖系统水文过程和水生产力变化问题开展两年的大田试验研究。以裸燕麦坝莜3号品种为材料,于2010年和2011年在甘肃定西进行,以充分灌溉为对照组,设置平地无种植、垄沟无覆膜种植、垄沟覆膜种植、裸地4个处理(此4个处理均无灌溉),测定生育期降雨、气温、0—140 cm土壤剖面水分变化、作物生长和产量等指标。结果表明,2010年和2011年分别为阶段性极端干旱和全生育期极端干旱两个类型,均导致所有处理组中土壤剖面60—100 cm的"土壤干层"现象,垄沟覆膜处理对"土壤干层"现象具有显著的缓解效应。与对照组相比,垄沟覆膜处理显著促进了收获期土壤剖面贮水量的回升,其贮水量分别提高了41.2 mm(2010年)和22.4 mm(2011年),全生育期水分利用效率和水生产力分别提高了1.7、0.4 kg·hm-2·mm-1(2010年)和6.5、9.8 kg·hm-2·mm-1(2011年)。另外,垄沟覆膜处理组的地上生物量比对照组降低了30.5%(2010年)和67.42%(2011年),但收获指数较对照分别提高了33.4%(2010年)和55.6%(2011年)。研究表明,垄沟覆膜处理促进了降水向土壤水和作物水的转化效率,显著地缓解了作物水分供需矛盾,是应对极端气候变化的重要生态策略。     

Precipitation Regime Shift Enhanced the Rain Pulse Effect on Soil Respiration in a Semi-Arid Steppe

The effect of resource pulses, such as rainfall events, on soil respiration plays an important role in controlling grassland carbon balance, but how shifts in long-term precipitation regime regulate rain pulse effect on soil respiration is still unclear. We first quantified the influence of rainfall event on soil respiration based on a two-year (2006 and 2009) continuously measured soil respiration data set in a temperate steppe in northern China. In 2006 and 2009, soil carbon release induced by rainfall events contributed about 44.5% (83.3 g C m⁻²) and 39.6% (61.7 g C m⁻²) to the growing-season total soil respiration, respectively. The pulse effect of rainfall event on soil respiration can be accurately predicted by a water status index (WSI), which is the product of rainfall event size and the ratio between antecedent soil temperature to moisture at the depth of 10 cm (r ² = 0.92, P<0.001) through the growing season. It indicates the pulse effect can be enhanced by not only larger individual rainfall event, but also higher soil temperature/moisture ratio which is usually associated with longer dry spells. We then analyzed a long-term (1953–2009) precipitation record in the experimental area. We found both the extreme heavy rainfall events (>40 mm per event) and the long dry-spells (>5 days) during the growing seasons increased from 1953–2009. It suggests the shift in precipitation regime has increased the contribution of rain pulse effect to growing-season total soil respiration in this region. These findings highlight the importance of incorporating precipitation regime shift and its impacts on the rain pulse effect into the future predictions of grassland carbon cycle under climate change.     

栽培模式、施氮和品种对冬小麦冠层结构和产量的影响

在黄土高原南部半湿润易早区土垫旱耕人为土上进行大田试验,研究氮肥、品种和栽培模式对冬小麦叶面积指数（IAI）和透光率（DIFN）及产量的影响。结果表明,小麦生长过程中IAI先增大后减小．在开花期最大。成熟期最小。施氮能够显著增加IAI;DIFN的变化规律与LAI相反。不同品种间IAI和DIFN差异显著。全程覆膜和覆膜150d的LAI极显著大于常规栽培、集雨面栽培和三密一稀栽培模式,DIFN与此相反;施氮后籽粒产量极显著增加。在不同栽培模式下,以全程覆膜、覆膜150d和集雨面栽培模式的产量较高,但从维持土壤质量角度考虑,则覆膜150d和集雨面2种栽培模式优于其它几种栽培模式;从冠层结构特征分析,这2种栽培模式更有利于增加群体光合能力。     

Zooplankton Growth,Respiration and Grazing on the Australian Margins of the Tropical Indian and Pacific Oceans

The specific activity of aminoacyl-tRNA synthetases (spAARS), an index of growth rate, and of the electron transport system (spETS), an index of respiration, was measured in three size fractions (73–150 μm, >150 μm and >350 μm) of zooplankton during five cruises to tropical coastal waters of the Kimberley coast (North West Australia) and four cruises to waters of the Great Barrier Reef (GBR; North East Australia). The N-specific biomass of plankton was 3–4-fold higher in the Kimberley than on the GBR in all 3 size classes: Kimberley 1.27, 3.63, 1.94 mg m^-3; GBR 0.36, 0.88 and 0.58 mg m^-3 in the 73–150 μm, >150 μm and >350 μm size classes, respectively. Similarly, spAARS activity in the Kimberley was greater than that of the GBR: 88.4, 132.2, and 147.6 nmol PPi hr^-1 mg protein ^-1 in the Kimberley compared with 71.7, 82.0 and 83.8 nmol PPi hr^-1 mg protein ^-1 in the GBR, for the 73–150 μm, >150 μm and >350 μm size classes, respectively. Specific ETS activity showed similar differences in scale between the two coasts: 184.6, 148.8 and 92.2 μL O₂ hr^-1 mg protein^-1 in the Kimberley, against 86.5, 88.3 and 71.3 μL O₂ hr^-1 mg protein^-1 in the GBR. On the basis of these measurements, we calculated that >150 μm zooplankton grazing accounted for 7% of primary production in the Kimberley and 8% in GBR waters. Area-specific respiration by >73 μm zooplankton was 7-fold higher in the Kimberley than on the GBR and production by >150 μm zooplankton was of the order of 278 mg C m^-2 d^-1 in the Kimberley and 42 mg C m^-2 d^-1 on the GBR. We hypothesize that the much stronger physical forcing on the North West shelf is the principal driver of higher rates in the west than in the east of the continent.     

Effects of Crop Canopies on Rain Splash Detachment

Crops are one of the main factors affecting soil erosion in sloping fields. To determine the characteristics of splash erosion under crop canopies, corn, soybean, millet, and winter wheat were collected, and the relationship among splash erosion, rainfall intensity, and throughfall intensity under different crop canopies was analyzed through artificial rainfall experiments. The results showed that, the mean splash detachment rate on the ground surface was 390.12 g/m²·h, which was lower by 67.81% than that on bare land. The inhibiting effects of crops on splash erosion increased as the crops grew, and the ability of the four crops to inhibit splash erosion was in the order of winter wheat>corn>soybeans>millet. An increase in rainfall intensity could significantly enhance the occurrence of splash erosion, but the ability of crops to inhibit splash erosion was 13% greater in cases of higher rainfall intensity. The throughfall intensity under crop canopies was positively related to the splash detachment rate, and this relationship was more significant when the rainfall intensity was 40 mm/h. Splash erosion tended to occur intensively in the central row of croplands as the crop grew, and the non-uniformity of splash erosion was substantial, with splash erosion occurring mainly between the rows and in the region directly under the leaf margin. This study has provided a theoretical basis for describing the erosion mechanisms of cropland and for assisting soil erosion prediction as well as irrigation and fertilizer management in cultivated fields.     

Spatial Distribution of Podoconiosis in Relation to Environmental Factors in Ethiopia: A Historical Review

Background

An up-to-date and reliable map of podoconiosis is needed to design geographically targeted and cost-effective intervention in Ethiopia. Identifying the ecological correlates of the distribution of podoconiosis is the first step for distribution and risk maps. The objective of this study was to investigate the spatial distribution and ecological correlates of podoconiosis using historical and contemporary survey data.

Methods

Data on the observed prevalence of podoconiosis were abstracted from published and unpublished literature into a standardized database, according to strict inclusion and exclusion criteria. In total, 10 studies conducted between 1969 and 2012 were included, and data were available for 401,674 individuals older than 15 years of age from 229 locations. A range of high resolution environmental factors were investigated to determine their association with podoconiosis prevalence, using logistic regression.

Results

The prevalence of podoconiosis in Ethiopia was estimated at 3.4% (95% CI 3.3%–3.4%) with marked regional variation. We identified significant associations between mean annual Land Surface Temperature (LST), mean annual precipitation, topography of the land and fine soil texture and high prevalence of podoconiosis. The derived maps indicate both widespread occurrence of podoconiosis and a marked variability in prevalence of podoconiosis, with prevalence typically highest at altitudes >1500 m above sea level (masl), with >1500 mm annual rainfall and mean annual LST of 19–21°C. No (or very little) podoconiosis occurred at altitudes <1225 masl, with annual rainfall <900 mm, and mean annual LST of >24°C.

Conclusion

Podoconiosis remains a public health problem in Ethiopia over considerable areas of the country, but exhibits marked geographical variation associated in part with key environmental factors. This is work in progress and the results presented here will be refined in future work.     

The Effect of N Fertilizer Placement on the Fate of Urea-15N and Yield of Winter Wheat in Southeast China

A field micro-plot experiment using nitrogen isotope (¹⁵N) labeling was conducted to determine the effects of placement methods (broadcast and band) and N rates (60, 150 and 240 kg ha^–1) on the fate of urea-¹⁵N in the wheat–soil system in Guangde County of Anhui Province, China. N fertilizer applied in bands increased grain yield by 15% compared with broadcast application. The N fertilizer application rate had a significant effect on grain yield, straw yield and aboveground biomass, as well as on N uptake and N concentration of wheat. The recovery of urea-¹⁵N was a little higher for broadcast (34.0–39.0%) than for band treatment (31.2–38.2%). Most of the soil residual N was retained in the 0–20 cm soil layer. At the N rates of 60 and 240 kg ha^–1, the residual ¹⁵N was higher for band (34.4 and 108.7 kg ha^–1, respectively) than for broadcast application (29.6 and 88.4 kg ha^–1, respectively). Compared with broadcast treatment, banded placement of N fertilizer decreased the N loss in the wheat–soil system. Band application one time is an alternative N management practice for winter wheat in this region.     

Dry Matter Production,Photosynthesis of Flag Leaves and Water Use in Winter Wheat Are Affected by Supplemental Irrigation in the Huang-Huai-Hai Plain of China

Winter wheat is threatened by drought in the Huang-Huai-Hai Plain of China, thus, effective water-saving irrigation practices are urgently required to maintain its high winter wheat production. This study was conducted from 2012 to 2014 to determine how supplemental irrigation (SI) affected soil moisture, photosynthesis, and dry matter (DM) production of winter wheat by measuring the moisture in 0–20 cm (W2), 0–40 cm (W3), and 0–60 cm (W4) soil profiles. Rainfed (W0) and local SI practice (W1, irrigation with 60 mm each at jointing and anthesis) treatments were designed as controls. The irrigation amount for W3 was significantly lower than that for W1 and W4 but higher than that for W2. The soil relative water content (SRWC) in 0–40 cm soil profiles at jointing after SI for W3 was significantly lower than that for W1 and W4 but higher than that for W2. W3 exhibited lower SRWC in 100–140 and 60–140 cm soil profiles at anthesis after SI and at maturity, respectively, but higher root length density in 60–100 cm soil profiles than W1, W2 and W4. Compared with W1, W2 and W4, photosynthetic and transpiration rates and stomatal conductance of flag leaves for W3 were significantly greater during grain filling, particularly at the mid and later stages. The total DM at maturity, DM in grain and leaves, post-anthesis DM accumulation and its contribution to grain and grain filling duration were higher for W3. The 1000-grain weight, grain yield and water use efficiency for W3 were the highest. Therefore, treatment of increasing SRWC in the 0–40 cm soil profiles to 65% and 70% field capacities at jointing and anthesis (W3), respectively, created a suitable soil moisture environment for winter wheat production, which could be considered as a high yield and water-saving treatment in Huang-Huai-Hai Plain, China.     

半干旱地区地膜覆盖对作物产量和氮效率的影响

在年降水量415mm的半干旱地区黄绵土上,以春小麦为供试作物进行大田试验,研究地膜覆盖进程(包括不覆膜、播种后覆膜30d、覆膜60d和全程覆膜)、底墒和施N对作物产量和N效率的影响．结果表明,增加底墒、地膜覆盖和施N均会显著增加作物产量和吸N量(α＜0.01),其影响顺序为N肥＞底墒＞覆膜．覆膜对产量的效应因底、施N和覆膜进程而异．从平均看,在低底墒时,各种覆膜处理产量虽有增加,但与不覆膜处理间的差异并不显著,而在高底墒时,以覆膜60d的产量最高,以不覆膜最低．由于覆膜和底墒影响作物产量和吸N量,因而也影响N效率．在低底墒时,以不覆膜和覆膜30d时N效率最高,而在高低墒时,30d、60d和全程覆膜处理间差异不显著．综合作物产量和N效率,全生育期覆膜并没有多少实际意义．     

Zoonotic tuberculosis knowledge and practices among cattle handlers in selected districts of Bangladesh

We assessed zoonotic tuberculosis (zTB) knowledge and prevention and control practices of 404 cattle handlers via a survey in three dairy-intensive districts of Bangladesh. Most respondents were aged 30–49 (52%) and male (95%). Almost all (99%) recognized the important public health burden of tuberculosis in Bangladesh, however, most (58%) had inadequate knowledge about zTB transmission to humans. Inappropriate practices such as: not using protective equipment (98%); smoking, drinking or eating food whilst working with cattle (69%); and sharing the same premises with animals (83%) were identified. Cattle handlers educated at secondary or higher levels were 2.82- (95% CI: 1.59–5.10) and 5.15 times (95% CI: 1.74–15.20) more likely to have adequate knowledge of control and prevention activities compared to those with no formal education. Those who had reared animals for 1–5 years were 2.67 times (95% CI: 1.44–4.91) more likely to have adequate knowledge, compared to those who reared animals for >15 years. Cattle handlers with a monthly incomes of 10,000–20,000 taka were significantly (Odds Ratio = 0.36, 95% CI: 0.14–0.92) less likely to have adequate knowledge compared to those with monthly incomes <10,000 taka. Cattle handlers with high school or higher education were 6.98 times (95% CI: 2.47–19.71) more likely to use appropriate zTB control and prevention practices compared to those without formal education. Those who had reared animals for 1–5 years, 6–10 years and 11–15 years were 2.72- (95% CI: 1.42–5.24), 2.49- (95% CI: 1.29–4.77) and 2.86 times (95% CI: 1.13–7.23) more likely to apply appropriate practices compared to those who reared animals for >15 years. Overall, education, duration of cattle rearing and monthly income predicted zTB knowledge and practices. There is an urgent need to educate those at high-risk of zTB transmission on issues including the handling of infected animals, and general hygiene. A One Health approach, to support the Sustainable Development Goals and the End TB strategy, appears to be the way forward.     

Analysis of water- and nitrogen-use efficiency of wheat in a Mediterranean climate

Water-use efficiency (WUE [g grain yield m^–2 mm^–1 ET]) and nitrogen-use efficiency (NUE [ g grain yield g^–1 N_applied]) are important measures that can affect the productivity of crops in different environmental systems. However, measurement and interpretation of WUE and NUE in the field are often hampered by the high degree of complexity of these systems due to season-to-season variability in rainfall, the variation in crop responses to soil types and to agronomic management. To be able to guide agronomic practice, experimentally-derived measurements of WUE and NUE need to be extrapolated across time and space through appropriate modelling. To illustrate this approach, the Agricultural Production Systems Simulator (APSIM), which has been rigorously tested for wheat (Triticum aestivum L.) in a Mediterranean environment, was used to estimate and analyse the WUE and NUE of wheat crops in the Mediterranean-climatic region of the central Western Australian agricultural zone. The APSIM model was run for three locations (average annual rainfall of 461 mm [high rainfall zone], 386 mm [medium] and 310 mm [low]) and two soil types that had contrasting plant-available water-holding capacities in the rooting zone (sand: 55 mm, clay soil: 109 mm). Simulations were carried out with historical weather records (82–87 years) assuming current crop management and cultivars. The modelling analyses highlighted the inherently high degree of seasonal variability in yield, WUE and NUE of wheat, depending on soil type, N fertiliser input, rainfall amount and, in particular, rainfall distribution. The clay soil tended to be more productive in terms of grain yield, WUE and NUE in the high and medium rainfall zones, but less productive in most years in the low rainfall zone. The sandy soil was less productive in the high rainfall zone due to the high nitrate leaching potential of this soil type, but more productive than the clay in the low rainfall zone due to poorer pre-anthesis growth and less water use, less water loss by soil evaporation and relatively more water use in the post-anthesis phase. When a wheat crop was sown early on clay soil in the low rainfall zone, it yielded as high as in the other rainfall zones in seasons when rainfall was above average or there was a good store of water in the soil prior to sowing. The simulations confirmed findings from a limited number of field experiments and extended these findings both qualitatively and quantitatively across soil types, rainfall regions and crop management options. Furthermore, by using long-term historical weather records, the simulations extended the findings across the wide range of climatic scenarios experienced in mediterranean-climatic regions.     

Platelet-to-Lymphocyte Ratio: A Novel Marker for Critical Limb Ischemia in Peripheral Arterial Occlusive Disease Patients

Background

Platelet-to-Lymphocyte Ratio (PLR) is an easily applicable blood test. An elevated PLR has been associated with poor prognosis in patients with different oncologic disorder. As platelets play a key role in atherosclerosis and atherothrombosis, we investigated PLR and its association with critical limb ischemia (CLI) and other vascular endpoints in peripheral arterial occlusive disease (PAOD) patients.

Methods and Findings

We evaluated 2121 PAOD patients treated at our institution from 2005 to 2010. PLR was calculated and the cohort was categorized into tertiles according to the PLR. An optimal cut-off value for the continuous PLR was calculated by applying a receiver operating curve analysis to discriminate between CLI and non-CLI. In our cohort occurrence of CLI significantly increased with an increase in PLR. As an optimal cut-off value, a PLR of 150 was identified. Two groups were categorized, one containing 1228 patients (PLR≤150) and a second group with 893 patients (PLR>150). CLI was more frequent in PLR>150 patients (410(45.9%)) compared to PLR≤150 patients (270(22.0%)) (p<0.001), as was prior myocardial infarction (51(5.7%) vs. 42(3.5%), p = 0.02). Regarding inflammatory parameters, C-reactive protein (median 7.0 mg/l (3.0–24.25) vs. median 5.0 mg/l (2.0–10.0)) and fibrinogen (median 457 mg/dl (359.0–583.0) vs. 372 mg/dl (317.25–455.75)) also significantly differed in the two patient groups (both p<0.001). Finally, a PLR>150 was associated with an OR of 1.9 (95%CI 1.7–2.1) for CLI even after adjustment for other well-established vascular risk factors.

Conclusions

An increased PLR is significantly associated with patients at high risk for CLI and other cardiovascular endpoints. The PLR is a broadly available and cheap marker, which could be used to highlight patients at high risk for vascular endpoints.     

Rice Performance and Water Use Efficiency under Plastic Mulching with Drip Irrigation

Plastic mulching with drip irrigation is a new water-saving rice cultivation technology, but little is known on its productivity and water-saving capacity. This study aimed to assess the production potential, performance, and water use efficiency (WUE) of rice under plastic mulching with drip irrigation. Field experiments were conducted over 2 years with two rice cultivars under different cultivation systems: conventional flooding (CF), non-flooded irrigation incorporating plastic mulching with furrow irrigation (FIM), non-mulching with furrow irrigation (FIN), and plastic mulching with drip irrigation (DI). Compared with the CF treatment, grain yields were reduced by 31.76–52.19% under the DI treatment, by 57.16–61.02% under the FIM treatment, by 74.40–75.73% under the FIN treatment, which were mainly from source limitation, especially a low dry matter accumulation during post-anthesis, in non-flooded irrigation. WUE was the highest in the DI treatment, being 1.52–2.12 times higher than with the CF treatment, 1.35–1.89 times higher than with the FIM treatment, and 2.37–3.78 times higher than with the FIN treatment. The yield contribution from tillers (YCFTs) was 50.65–62.47% for the CF treatment and 12.07–20.62% for the non-flooded irrigation treatments. These low YCFTs values were attributed to the poor performance in tiller panicles rather than the total tiller number. Under non-flooded irrigation, root length was significantly reduced with more roots distributed in deep soil layers compared with the CF treatment; the DI treatment had more roots in the topsoil layer than the FIM and FIN treatments. The experiment demonstrates that the DI treatment has greater water saving capacity and lower yield and economic benefit gaps than the FIM and FIN treatments compared with the CF treatment, and would therefore be a better water-saving technology in areas of water scarcity.