种带真菌对结缕草种子发芽和活力的影响

采用孢子悬浮液法将从结缕草上分离得到的种带真菌菌种进行回接，测试不同种带真菌对结缕草发芽和活力的影响。研究结果表明：多数种带真菌显著降低了种子的发芽率和活力指数，抑制了种苗的生长，使死种率显著上升，其中，不等弯孢（Curvularia inaequalis）、禾生皮司霉（Pithmyces graminicola）、橡胶平脐蠕（Bipolaris heveae）、嘴突突脐蠕孢（Exerohilum rostratum）、白粉寄生菌（Ampelomyces sp．）、狗尾草平脐蠕孢（B．setariae）、茎点霉（Phoma sp．）、木贼镰刀菌（Fusarium equiseti）等对结缕草种子和种苗的危害最为严重。     

Untersuchungen zur Ertragsbildung kurz- und langstrohiger Winterweizensorten

Investigations about the yield formation of Winter Wheat Cultivars with Short and Long Straw.
The yield formation of winter wheat cvs with semi-dwarf, short straw and long straw growth habit was investigated over three years in field and glasshouse trials.
The cv with semi-dwarf growth habit had less earbearing tillers and spikelets per ear, an essential lower reduction rate of spikelets and more kernels per spikelet. This cv ranged medium in thousand kernel weight (tkw). Cvs with short straw differed from cvs with long straw through a lower reduction rate of tillers and a lower tkw.
No differences were found in the time of development of generative organs in specific growth phases. Cvs with short straw had advantages in assimilation by means of higher leaf area indices from tiller formation till anthesis and a better light penetration in the canopy due to a more erect leaf orientation. These characters may have been decisive for the higher survival of tillers. The cvs with a long straw however had a higher tkw, properly due to a less compact ear and a higher assimilate gain during kernel filling. Only small differences were found in root growth in favour of the cvs with short straw. The semi-dwarf cv had the shortest roots. The cv "Kanzler" with a long straw had the best drought resistance.     

Impact of very low crop residues cover on wind erosion in the Sahel

In the Sahel, with average annual precipitation in the order of 500 mm yr^− 1, wind erosion occurs mainly on cultivated millet fields whose surfaces are only partially covered by crop residues. The impact of these residues on wind erosion was not clearly established. The objective of this study is thus to quantify the actual amount of crop residues in traditional Sahelian fields and to determine their impacts on wind erosion by reference to a bare surface throughout the seasonal cycle over several years.     

Combined effects of abiotic factors on Collembola communities reveal precipitation may act as a disturbance

Global increases in temperature and atmospheric CO₂, coupled with increasingly sporadic and intense precipitation regimes, may affect the biodiversity of boreal forest communities, potentially leading to shifts in functional process rates such as decomposition. However, the effects of these factors on microarthropod community composition have not been thoroughly studied in combination in controlled settings. We conducted a full factorial experiment exposing moss/soil mesocosms to three temperatures (11.5, 15.5, and 19.5 °C), two CO₂ levels (430 ppm and 750 ppm), and three moisture levels (drought, intermediate, and saturated conditions) for 18 weeks. Following treatment, we quantified effects on species diversity of a representative group of mesofaunal microarthropods, the Collembola. We also quantified the effects of these factors on the distribution of collembolan body sizes as an indicator of functional changes in the community. We found that moisture regime was a dominant factor, with increased precipitation leading to decreased collembolan abundance and richness. The mechanisms of these detrimental effects are unclear but may be due to the saturation of air-filled soil pore space or competition with moisture-tolerant species. Severe precipitation regimes caused a general loss of abundance in species of all sizes, which may have long term effects on boreal forest soil food webs.     

环境流体动力学模拟优选人工湿地设计中隔板湿地长度比

采用环境流体动力学模型(environmental fluid dynamics code,EFDC)建立表面流人工湿地水动力-水质耦合模型,研究隔板长度与湿地长度比值(简称隔长比)对表面流人工湿地水力性能及净化效果的影响规律,优选适宜的隔长比。结果表明:1)率定和验证的12组结果中,水动力模型模拟评价结果为中等及以上,即相关系数0.7、纳什系数0.4、相对误差20%,的有7组,水质模型模拟评价结果为中等及以上,即相对误差20%,的有10组。2)表面流人工湿地适宜隔长比随长宽比的增加而增大,当长宽比由1、2、4变为4、8、16时,对应的适宜隔长比分别为0.675、0.850、0.938。3)表面流人工湿地主要水力指标随适宜隔长比的增大而增加,对净化效果指标的提升不明显。4)在适宜隔长比不变的情况下增加湿地的表面积能明显提升水质净化效果(50%)。研究可为表面流人工湿地实际工程设计提供依据。     

沼气组分比例对其燃烧稳定性及层流燃烧特性的影响

为了获得沼气主要组分比例所占比例对其燃烧稳定性与层流燃烧特性的影响规律,试验测量了当量比范围为0.8~1.3、初始压力范围为0.1~0.3 MPa、初始温度为320 K、甲烷体积分数分别为47%、55.5%、59%条件下沼气的火焰发展特性。同时,分析了沼气主要组分比例所占比例对沼气层流燃烧时的火焰稳定性与燃烧速度的影响规律。结果表明,当初始温度为320 K、当量比为1.0、初始压力为0.1 MPa时,在不同甲烷体积分数下火焰前锋面均较为光滑,并呈准球形向外发展;当初始压力升高至0.2 MPa时,不同甲烷体积分数下火焰前锋面均出现了裂纹与火焰突起,优先扩散不稳定性初步显示;当初始压力继续升高至0.3 MPa时,优先扩散不稳定性逐步明显,同时,浮力不稳定性将初步显示。随着当量比的增加、初始压力的降低或沼气中甲烷体积分数的增加,马克斯坦长度逐渐增大,火焰稳定性逐步增强。在各工况下无拉伸火焰传播速度与层流燃烧速度随当量比的升高呈现先增加后降低的趋势,在当量比为1.1时达到最大;同时,随着初始压力的降低或甲烷体积分数的升高,无拉伸火焰传播速度与层流燃烧速度逐渐增大。     

Corn Hybrid Response to Starter Fertilizer Combinations

ABSTRACT

Research has shown that some corn (Zea mays L.) hybrids grown under reduced tillage conditions respond to starter fertilizer containing nitrogen (N) and phosphorus (P), while others do not. This research studied variability of responsiveness among corn hybrids to starter fertilizer containing a more complete complement of nutrients. The experiment was conducted from 1996 to 1998 on a producer's field near Scandia, KS, on a Carr sandy-loam soil (coarse-loamy, mixed, superactive calcareous, mesic Typic Udifluvents). The response of four corn hybrids (Pioneer 3563, Pioneer 3346, DeKalb 591, and DeKalb 646) to starter fertilizer combinations containing N, P, potassium (K), sulfur (S), and zinc (Zn) was evaluated. In all three years of the experiment, starter fertilizer containing N and P consistently increased grain yield, reduced the number of thermal units needed from emergence to maturity, decreased grain-moisture content at harvest, and increased total P uptake (grain plus stover at maturity) of Pioneer 3346 and DeKalb 591, but had no effect on Pioneer 3563 and DeKalb 646. Addition of S to the starter mix produced additional yield increases for Pioneer 3346 and DeKalb 591, whereas addition of K and Zn to the starter did not show any additional yield benefit for these two hybrids. Grain yield of Pioneer 3563 and DeKalb 646 was not improved by starter fertilizer, regardless of the elemental composition. When no starter fertilizer was applied, early-season root development was greater in Pioneer 3563 and DeKalb 646 than in the other two hybrids. However, the addition of starter fertilizer increased numbers of roots and depth of rooting in Pioneer 3346 and DeKalb 591 but had no effect on Pioneer 3563 and DeKalb 636. Results showed starter fertilizer benefited grain yield for two hybrids. Grain yield of the other two hybrids, however, was not influenced by starter, regardless of which nutrients were supplied. This response may be attributed to differences in root-growth characteristics of the hybrids. The two responsive hybrids did, however, yield an average of 0.75 mg ha^?1 greater than the two non-responsive hybrids. This result indicates it is unlikely that all of the yield loss from not using a starter can be avoided by hybrid selection.     

Waiting reveals waning weight: Monitoring over 54 years shows a decline in body condition of a long-lived reptile (tuatara, Sphenodon punctatus)

Knowledge gained from monitoring has been the basis for many critical decisions in threatened and endangered species and ecosystem management. Long-term monitoring has been recognized as a necessity for elucidating population trends and community interactions, particularly for long-lived species or ecosystems with slow rates of change. We examine seasonal and annual cycles of morphological changes in a threatened, long-lived, insular reptile, the tuatara (Sphenodon punctatus), on Stephens Island, New Zealand. We used body condition indices as a surrogate measure of fitness, and examined seasonal fluctuations, using data from an intensive mark-recapture study, and long-term trends using a dataset that spans 54 years. In spite of seasonal and annual fluctuations, body condition of tuatara has declined significantly between 1949 and 2003; the decline was only evident after >22 years of monitoring. We hypothesize that increasing numbers of tuatara have resulted in a density-dependent population response driven by past habitat modification on Stephens Island. We emphasize the need for long-term monitoring and suggest that potentially costly management decisions, particularly for long-lived species or ecosystems with slow rates of change, should not be based solely on short-term monitoring.     

Root Growth and Soil Water Dynamics in Relation to Inorganic and Organic Fertilization in Maize–Wheat

Agricultural productivity is increasingly becoming dependent upon soil fertility, which is generally thought to be supplemented through the application of nutrients mainly through inorganic fertilizers. The present study aims to characterize the soil physical environment in relation to long-term application of farmyard manure (FYM) and inorganic fertilizers in a maize–wheat cropping system. The treatments in both the maize and wheat systems included a control (without any fertilizer or FYM), FYM (farmyard manure at 20 t ha^?1), N₁₀₀ (nitrogen at 100 kg ha^?1), N₁₀₀P₅₀ (nitrogen and phosphorus at 100 and 50 kg ha^?1), and N₁₀₀P₅₀K₅₀ (nitrogen, phosphorus, and potash at 100, 50, and 50 kg ha^?1). The treatments were replicated four times in a randomized complete block design in sandy loam soil. The root mass density in surface layers of both the crops was lower in FYM and higher in inorganic fertilizer plots. The root length density was found to be highest in FYM-treated plots and lowest in control plots. The periodic soil matric suction during wheat following maize remained highest in FYM plots followed by that in N₁₀₀ plots in all the layers. The soil water storage of wheat at harvest (rice–wheat) was highest (21.1 cm) in control and lowest (17.8 cm) in FYM-treated plots. The soil water status, root growth, and crop performance improved with balanced fertilization.     

Zinc-Use Efficiency in Upland Rice Genotypes

Zinc (Zn) deficiency is very common in annual crops grown on Brazilian Oxisols. A greenhouse experiment was conducted to evaluate Zn-use efficiency of 20 upland rice genotypes. The Zn levels used were 0 mg kg^?1 (natural level of the soil) and 20 mg kg^?1 of soil applied with zinc sulfate (ZnSO₄). Zinc × genotype interactions were significant for grain yield, panicle number, panicle length, root dry weight, and specific root length, indicating different responses of genotypes with the variation of Zn levels and that selection for Zn-use efficiency is necessary at low as well as at high Zn rates. Based on Zn-use efficiency index, 11 genotypes were classified as efficient and nine were classified as moderately efficient. The most Zn-efficient genotypes were BRA 01596, BRA 042156, BRA 052053, BRA Primavera, and BRA 01506. The most inefficient genotypes in Zn-use efficiency were BRA 042094, BRA 052045, BRA 052034, and BRA 052023. Grain yield and most of the yield attributing characteristics have significant Zn × genotype interactions, which indicate that genotypes respond differently under different Zn levels. Thus, genotype selection is an important strategy for upland rice production in Brazilian Oxisols.