Pathogens occurring on ten varieties of ryegrass at Rothamsted in 1973–74

Six varieties oi Loliumperenne, three of L. multiflorum and one hybrid (L. multiflorum × L. perenne) were assessed for diseases over two harvest years. Crown rust (Puccinia coronata) and mildew (Erysiphe graminis) occurred on some varieties in 1973. Leaf spotting (Drechslera spp.) was common, but slight on most varieties, in both years. Ryegrass mosaic virus (RMV) and its mite vector, Abacarus hystrix were present on all varieties in the second year. The relative susceptibility of varieties to RMV was similar in the field and in glasshouse tests.     

The effect of delayed autumn harvest on the survival of varieties of perennial ryegrass

The reactions of five early and five late varieties of perennial ryegrass to stimulation of bulky autumn growth and deferment of harvesting were compared in terms of spring growth and subsequent recovery during three winters. Winterkill was marked in 1971–72, particularly when harvesting was deferred to late November, in early varieties S24 and Presto Pajbjerg and in the late variety S23. Least affected among early varieties were Premo and Barvestra (tetraploid) and among late varieties, Perma and Barpastra (tetraploid). All varieties showed rapid recovery. The results are discussed in terms of the significance of winterkill, and the effects of age of sward, variety susceptibility and deferment of autumn defoliation. It is concluded that the form of winterkill which occurs in the west of Scotland can have serious consequences to farm productivity in severe winters. Autumn growth left standing into November can also lead to winterkill. Under good management, varietal differences are unimportant. In a severe winter, no varieties of perennial ryegrass are reliable.     

Removal of mineral nutrients by red clover varieties

K, P, Ca and Mg contents and uptakes are reported from total herbage of plots sown with six varieties of red clover harvested three times a year for 3 years. K, P and Mg contents were above those reported as critical for growth; values for Ca were lower than quoted ranges which suggested that growth might have been affected by either deficiency of Ca or low pH. Hungaropoly was characterized by relatively low K and P and high Ca contents. Maximum uptakes in red clover total herbages over 3 years were 1198 kg ha^?1 K (Hera), 112 kg ha^?1 P (Hera), 494 kg ha^?1 Ca (Hungaropoly) and 104 kg ha^?1 Mg (Mars). Results were compared with those found for S101 perennial ryegrass, harvested on a similar system and receiving similar fertilization with uptakes of 759 kg ha^?1 K, 100 kg ha^?1 P, 200 kg ha^?1 Ca and 46 kg ha^?1 Mg, by expressing accumulating uptakes and inputs as linear regression equations. The better varieties of red clover, Hera, Hungaropoly, Mars and S123 show rates of DM accumulation similar to S101 perennial ryegrass and similar uptake rates of K and P but higher rates of uptake of Ca and Mg. The levels of application of K and P used in the experiment seem to be more than adequate but attention to the Ca status may be required to sustain high-yielding red clover swards.     

Economic trade-offs to limit nonpoint sources of agricultural pollution

A national model has been built which allows analysis of physical and economic trade-offs as soil loss per acre is limited to specified levels in each major land group of the nation. Crop variables with their associated conservation practices are developed for each of 1891 land groups in 223 agricultural producing regions and 51 water supply regions. The regions and soil groups are made interdependent through regional commodity demands and a transportation submodel. Hence, changes in cropping systems and erosion control practices in one region are simultaneously expressed in effects on other regions. Soil loss limits are set at 10, 5, and 3 t per acre. The 10 t limit does not have a large impact on interregional production patterns and farm comodity prices. However, the 5 and 3 t limits, either singularly or in combination with different export levels, cause rather marked increases in commodity prices. Also at limits of 5 and 3 t, considerable shifts take place among regions in the crops grown and the erosion control methods used. Regions with erosive soils sacrificed in reduced income; regions with level soils can crop more intensely and gain greater income. Conservation practices such as reduced tillage increase the amount of pesticides needed in some regions and pose special environmental problems. The South Atlantic region is affected most by soil loss limits to control nonpoint pollution. The Great Plains regions with more level land and limited rainfall are affected least.     

Pyrolysis-gas chromatographic analysis of black paints.

Samples of 79 black paints from 27 manufacturers in the United States were examined to determine the extent to which paints can be distinguished by pyrolysis-gas chromatography. Evaluation by a Carbowax column showed some differences among paints from different manufacturers and among batches of paints from the same manufacturer. However, it was not possible to conclude that paints with identical chromatograms had a common origin.     

Impact of Intracoastal Waterway maintenance dredging on a mud bottom benthos community

The effects of hydraulic dredging on the benthic infauna of a mud bottom area were investigated in Georgia in the Atlantic Intracoastal Waterway. Complete displacement of the benthic community was caused by dredging; however, the community began to recover within a month following the cessation of dredging. Within two months the diversity and species composition of the dredged channel were similar to that of a control area and little change in sediment composition resulted. Thus, no apparent limitation was imposed on the normal benthic population by habitat alteration. Recolonisation was too rapid to have been caused by the settling of immature or larval stages from the water column alone. Bank slumping and migration of adult forms have been postulated as other means of recolonisation.     

The effects of dredging operations on the benthic community of a chalk stream

Sampling of the benthic fauna showed that dredging operations produced relatively short-term effects on invertebrate population levels. The behaviour of the animals was immediately affected, the differences between species were noted and the implications of dredging at different times of year are discussed.     

Report by Bureau of Land Management on range conditions and grazing in Nevada

The Bureau of Land Management, a federal agency administering more than 72 million ha in the western United States, has often been criticised for allowing excessive livestock grazing and neglecting wildlife, watershed and recreation values on its lands. The first draft of a report by Bureau personnel evaluating the agency's policies in the State of Nevada supports the allegations. Congressional action is necessary to provide the Bureau with broader responsibilities, increased funding and greater authority, all of which are necessary to bring better balance to the Bureau's programme.