Effect of moisture level on the root pattern of Alfalfa

Summary There have been a few investigations on the effect of moisture on root development of alfalfa (Medicago sativa L.), but none have attempted to describe the relationships in a quantitative manner. Therefore, alfalfa root patterns along with yield and evapotranspiration (ET) were examined under different moisture levels, using a line-source sprinkler system. Water application ranged from 28 to 153 cm, the latter representing the potential evapotranspiration. Alfalfa root mass and yield were highest under high moisture levels, and the shoot/root ratio increased with increasing moisture level. The relationships between ET and root mass and between ET and shoot/root ratio were curvilinear. The largest percentage of root mass under all moisture treatments was found in the top 45 cm of the soil profile where the largest differences in total root mass between treatments were observed. The percentages of roots at each soil depth averaged over three ranges of moisture levels were curvilinear functions of soil depth. Although alfalfa roots were found to a depth of at least 150 cm for all moisture levels, there was a greater rooting depth with a higher moisture level. Roots were detected to a depth of 210 cm for the high moisture treatment, although root biomass was small below 170 cm where a sand layer was encountered which may have impeded root penetration. The root diameter was found to be independent of moisture level, which means that there was a greater root surface area with higher moisture levels. Root length density distribution was similar to root mass distribution.Journal article 911, Agricultural Experiment Station, New Mexico State University, Las Cruces, NM 88003, USA     

Comparing the value of Southern Oscillation Index-based climate forecast methods for Canadian and US wheat producers

Southern Oscillation Index (SOI) based forecasting methods are compared to determine which method is more valuable to Canadian and US wheat producers. Using decision theory approach to valuing information, the more commonly used three-phase method of El Niño, La Niña, and other is compared to a five-phase system. Because of differences in growing season and yearly SOI classification schemes, two different three-phase methods are used. The five-phase system is based on the level and rate of change of the SOI over a 2 month period. Phases are consistently negative, consistently positive, rapidly falling, rapidly rising, and near zero. As expected, results vary by the method used. Winter wheat producers in Illinois place no value on either of the SOI-based forecasting systems. Producers at seven of the 13 sites prefer the five-phase method over either of the three-phase method (spring wheat producers in Manitoba, Alberta, North Dakota and South Dakota, along with winter wheat producers in Oklahoma, Texas, and Washington). The value of the five-phase approach is up to 70 times more valuable than the three-phase approach. Producers growing spring wheat in Saskatchewan and Montana, along with winter wheat producers in Ohio and Kansas value the three-phase approach more than the five-phase. In this case, the value of the three-phase system is up to two times more valuable than the five-phase system. Depending on expected price and region, the values of the SOI-based forecasts range from 0 to 22% of the value of perfect forecasts. In both absolute and percentage of perfect forecasts, producers in Oklahoma, Texas, Manitoba, Saskatchewan, and South Dakota value either system more than producers in the remaining regions. Economic value and distributional aspects of the value of climate forecasts have implications for producers, policy makers, and meteorologists. Finally, the results clearly suggest all producers will not prefer one forecast type. Forecasts need to be tailored to specific regions.     

The role of moisture content in the stability of soil aggregates from a temperate silty soil to raindrop impact

Aggregate stability to drop impact is of fundamental importance to many aspects of the soil system, in particular rainsplash erosion. The role of moisture content is considered by the use of a single drop simulator on soil aggregates of known moisture content selected from the Hamble series. Results indicate a negative logarithmic relationship between time to breakdown and specific moisture content. In addition the variability of the results drastically declines with increasing moisture content. The results are explained in terms of distribution of moisture within the aggregates prior to experimentation.     

Ultrastructural analysis of softwood fracture surfaces

Summary The ultrastructural characteristics of fracture surfaces from southern pine and Douglas-fir specimens tested in tension at various angles to grain were examined. The fracture surace morphology was inspected using scanning electron microscopy. Three anatomical failure types were recognized: intercell failure, transwall failure, and intrawall failure. Certain failure characteristics were ascribed as a function of the magnitudes of paralleland perpendicular-tograin tension and parallel-to-grain shear present in the specimen. In specimens tested in paralleland perpendicular-to-grain tension, the thick-walled latewood cells were found to fail in a combination of transwall and intrawall failure. The intrawall failures were usually at the S₁–S₂ interface. The more thin-walled earlywood cells were more likely to exhibit abrupt, transwall failures. At intermediate angles of load to grain, surfaces indicative of the type found in pure shear tests were predominant. Perpendicularto-grain tension failures resulted in mostly intercell failures. Ray cells consistently exhibited transwall failures. The failure surface frequently changed planes in all loading modes. This path transfer was inevidably associated with material discontinuities in the wood. When the path did transfer, all three failure types were observed. No significant species effect was observed.     

孟加拉国丘陵地带桔园和灌木林地土壤物理性质的比较评价(英文)

对孟加拉国丘陵地带Mro部落经营的桔园与灌木林35%和55%两种坡地土壤物理性质进行了比较与评价。每一块用地内挖掘3个土壤剖面采集不同深度(0-5cm,5-15cm and 15-30cm)的土壤样品,测定土壤水分、有机质含量和土壤密度。最大持水量、田间持水量、干或湿土壤容重和土壤孔隙度的测定仅限于表层土壤。两种坡地桔园3个深度的土壤水分含量均显著高于灌木林地相同深度的土壤水分。桔园在55%坡地内土壤有机质含量低于林地含量值,而在35%坡地内的含量值则高于林地值。两块样地内上述两项测定值均在表层土壤中最高,且随土层深度的增加而降低。与灌木林地比较,桔园地表层土壤最大持水量、孔隙度和3个不同深度的土壤密度均较低。两块用地内不同坡地的表层土田间持水量有所差异,且桔园地干或湿表层土壤容重高于林地内的数值。表5参23。     

Acetocarmine squash method for observing sugar beet chromosomes

Summary Based on successful results of an acetocarmine squash method for staining chromosomes of many plant species, the method was applied to chromosomes of sugar beet (Beta vulgaris L.). This simple method proved to be applicable to the relatively small chromosomes of sugar beet. Several known disadvantages of acetocarmine staining techniques are overcome by applying acid hydrolysis and maceration. Squashing the stained specimens in 45% acetic acid increases the contrast between stained chromosomes and destained cytoplasm. The advantages of this method are its simple procedure and applicability to both somatic and meiotic chromosomes. Uniform and high quality preparations make detailed analysis possible even with the relatively small chromosomes of sugar beet.Contribution from the Department of Agronomy and published with the approval of the Colorado State University Experiment Station as Scientific Series Paper No. 2334.Supported in part by a Research Grant from the Great Western Sugar Company, Longmont, Colorado.