Impact of white grub (Liqyrus subtropicus (Blatchley)) infestation on sugarcane nutrition 1

The white grub (Ligyrus subtropicus (Blatchley)) is a major insect pest of Florida sugarcane (Saccharum spp.). The primary impact this insect has on the sugarcane plant is through larval feeding on plant roots and underground stems. A greenhouse study was conducted to evaluate the effect of L. subtropicus larval feeding on N, P, K, Ca, and Mg nutrition of sugarcane. Third instar L. subtropicus larvae were introduced to the soil at rates of 0, 2, 4, 6, and 8 larvae/plant. Leaf N, P, and K concentrations decreased linearly as the level of grub infestation increased. Leaf Ca and Mg concentrations were not affected by grub feeding.     

Winter Composting Using the Passively Aerated Windrow System

Field trials demonstrated that agricultural wastes could be successfully composted in the winter with the passively aerated windrow system. Three small windrows were constructed. One pile contained a sheep manure-straw mixture, while the other two piles contained varied amounts of horse manure, cow manure, and bedding materials (straw, wood chips). The piles were constructed on a porous base of wood chips. Standard four-inch (10 cm) perforated pipes were placed approximately three feet apart in the porous base, perpendicular to the length of the windrow. Piles were covered with 15 to 20 centimeters of finished compost. A commercial compost covering fabric permeable to gases and water vapor but impermeable to liquid water was used for additional insulation and protection against high winds. Ambient temperatures ranged from ?27°C to 15°C during the trials. Initially, all three piles froze. Then the ends of the piles began to heat up, with the southern ends which received the most sunlight heating up first. Plugging the pipes seemed to help the piles heat up faster, but did not appear to be necessary. Thermophilic temperatures were attained and the composting cycle took 50 to 80 days after the piles heated up. Oxygen levels were highest at the bottom of the pile, and decreased as one moved to the top of the pile. The biggest practical problem encountered was the snow drifts that periodically formed at the windrow base, covering the pipe openings.     

带拉杆的U形壳槽槽身横向内力计算有关问题的分析

在U形壳槽横向内力计算中,若不考虑槽底局部加厚对Φ=90°截面内力的影响,则计算所得的该截面弯矩绝对值偏小.温度变化对截面内力的影响较大,特别是温降引起多数截面的弯矩增加,而轴向力减少;温升引起Φ=90°截面弯矩与轴向拉力均增加,再考虑槽底局部加厚的影响,弯矩值还要增加.槽底局部加厚与温度变化的作用均不能忽略不计,否则,内力计算成果值会偏于不安全.用结构力学方法,推导出二者对内力影响的计算公式,并附有应用的算例.     

Effect of ascorbic acid on the disease caused by Escherichia coli challenge infection

In a series of experiments, leghorn-type chickens were fed diets containing from 0 to 880 mg of ascorbic acid/kg of feed beginning 1 day before air-sac challenge with Escherichia coli. Infection occurred in 46/60 (76%) of the controls and in 12/63 (19%) of those given feed containing 330 mg of ascorbic acid/kg. Levels of ascorbic acid above and below 330 mg/kg feed were less effective.     

Prevention of Toxoplasma gondii abortion in goats by vaccination with oocysts of Hammondia hammondi

Nineteen does (female goats) were dosed with 500,000 oocytes of Hammondia hammondi prior to breeding. At about 90 days of gestation these, and 18 uninoculated does were challenged with 25,000 Toxoplasma gondii oocysts. The 19 H. hammondi--inoculated does produced 26 live and one dead kid (newborn goat). The 18 does not given H. hammondi produced 12 live and 19 dead kids. However, examination of all of the kids by isolation of T. gondii in mice, serology and histology revealed that they were all infected with T. gondii. Thus, while H. hammondi "vaccination" is protective against the deleterious effects of T. gondii on pregnant does, perhaps by reducing the severity of placental lesions, it does not prevent foetal infection.