Competition between white clover (Trifolium repens L.) and subterranean clover (Trifolium subterraneum L.) in binary mixtures in the field

White clover, (cv. Haifa) and subterranean clover (cv. Seaton Park) were grown in binary replacement series mixtures in the field at proportions of 100:0, 90:10, 50:50. 10:90 and 0:100, and cut every four weeks over three growing seasons from 1985 to 1987 at Scone, New South Wales (NSW) (32°S).
Relatively low plant densities minimized competition in 1985, but in subsequent seasons Haifa and Seaton Park competed vigorously for the same resource;.; usually having relative crowding coefficients greater than 1.0, and relative yield totals greater than 1.0 in spring of 1986 and 1987, and autumn 1987. This over-yielding appeared to be due to some complementarity of leaf morphology and canopy architecture.
Haifa severely depressed seed production of Seaton Park in mixtures. Haifa regenerated as an annual in 1986, but as a perennial, from surviving stolons, in 1987 owing to lower maximum temperatures and better rainfall distribution in late summer and autumn of 1987.
It is concluded that white clover can survive severe competition from subterranean clover as a seedling, and if moisture allows, may severely depress seed production from subterranean clover, regardless of whether plants are annual or perennial in origin. Spatial separation may minimize competition in average years but competition effects may be severe in seasons with sufficient summer rainfall for perennation of white clover, and seasonal autumn rainfall for germination of subterranean clover.     

Orchardgrass and perennial ryegrass with applied nitrogen and in mixtures with legumes

High-yielding grass-legume mixtures play an important role in forage-animal systems but finding compatible and adapted species can sometimes be difficult. The objective of this study was to examine productivity of perennial ryegrass and orchardgrass in pure stands with N and in mixtures with legumes.
Broadcast sowings were made on conventionally prepared seedbeds in August 1979 and May 1980 on a Hagerstown silt loam soil (fine, mixed mesic Typic Hapludalf). When sown alone orchardgrass cv. Pennlate and perennial ryegrass cv. Reveille received rates of N ranging from 0 to 448 kg ha⁻¹ a⁻¹. The grasses were also grown in mixtures with alfalfa cv. Arc, red clover cv. Arlington, or birds foot trefoil cv. Viking. The same legumes were sown alone. Four legume seed rates were used in both the pure legume and mixed stands.
Orchardgrass-N swards were more productive than ryegrass-N swards over 3 years. More dry matter (DM) was harvested from pure stands of     

Characteristics of Water Infiltration in Layered Water-Repellent Soils

Water-repellent(WR) soil greatly influences infiltration behavior. This research determined the impacts of WR levels of silt loam soil layer during infiltration. Three column scenarios were utilized, including homogeneous wettable silt loam or sand, silt loam over sand(silt loam/sand), and sand over silt loam(sand/silt loam). A 5-cm thick silt loam soil layer was placed either at the soil surface or 5 cm below the soil surface. The silt loam soil used had been treated to produce different WR levels, wettable, slightly WR, strongly WR, and severely WR. As the WR level increased from wettable to severely WR, the cumulative infiltration decreased. Traditional wetting front-related equations did not adequately describe the infiltration rate and time relationships for layered WR soils. The Kostiakov equation provided a good fit for the first infiltration stage. Average infiltration rates for wettable, slightly WR, strongly WR, and severely WR during the 2 nd infiltration stage were 0.126, 0.021, 0.002, and 0.001 mm min~(-1) for the silt loam/sand scenario,respectively, and 0.112, 0.003, 0.002, and 0.000 5 mm min~(-1) for the sand/silt loam scenario, respectively. Pseudo-saturation phenomena occurred when visually examining the wetting fronts and from the apparent changes in water content(?θ_(AP)) at the slightly WR,strongly WR, and severely WR levels for the silt loam/sand scenario. Much larger ?θAPvalues indicated the possible existence of finger flow. Delayed water penetration into the surface soil for the strongly WR level in the silt loam/sand scenario suggested negative water heads with infiltration times longer than 10 min. The silt loam/sand soil layers produced sharp transition zones of water content. The WR level of the silt loam soil layer had greater effects on infiltration than the layer position in the column.     

替米考星对仔猪呼吸道感染的疗效试验

进行了替米考星对仔猪呼吸道感染的疗效试验,并与泰乐菌素、支炎净、氟苯尼考、克林霉素进行比较。替米考星治疗组仔猪死亡率、有效率、治愈率分别为5.88%、94.12%和88.23%,经统计学分析,效果显著优于对照组(P<0.01);替米考星预防组仔猪发病率、死亡率、有效率和15 d增重分别为4.76%、0、100%和(5.65±1.25)kg,经统计学分析,有效率、治愈率和相对增重显著高于对照组(P<0.01),仔猪发病率、死亡率明显低于对照组(P<0.01)。试验结果表明,替米考星对仔猪呼吸道感染疗效显著,具有临床使用和推广价值。     

Biological control of Botrytis stem infection of greenhouse tomatoes

Botrytis cinerea infects stem wounds of greenhouse tomatoes and can cause serious economic losses. A bioassay using stem sections was developed to study wound infection and to screen potential fungal antagonists for activity against Botrytis Cladosporium cladosporioides reduced infection from 80–100% to 0–10%. A much smaller proportion of Trichoderma harzianum gave this reduction. Similar results were obtained on whole plants. Penicillium isolates varied widely in activity. The concentration of Cladosporium and Trichoderma which gave the highest level of protection was c . 10⁸ cfu/mL. When only half the wound was treated, simulating poor spray coverage, Cladosporium isolates still prevented infection. By contrast, Trichoderma isolates and four fungicides failed to give the same level of protection. The ability of certain fungal isolates to colonize the wound surface was thought to be partly responsible for this activity. The successful application of antagonists to whole plants using both aqueous suspensions and gel secateurs is described.