Alkyl resorcinols in grains from plants from the family Gramineae

5-n-alkylresorcinols were found in 22 of the 27 studied species of grasses. In <em>Agropyron caninum</em> and <em>Bromus macrostachys</em> only the content of alkyl resorcinols was determined, in <em>Agropyron repens, Bromus mollis</em> and <em>Elymus arenarius</em> the composition of alkyl resorcinol homologues was also established. When calculated per gram of dry mass of air-dried grains, the content of alkyl resorcinols was found to be: in the genus <em>Agropyron</em> - approximately 715 µg, in the genus <em>Bromus</em> approximately 60 µg and in <em>Elymus</em> arenarius, 272 µg. The homologues of alkyl resorcinods in the studied genera of grasses differ from the homologues found in wheat or rye by their greater content of long-chain fractions.

Spatial distribution and changes in occurrence of some weed species in the orchard in AES Felin near Lublin

From 1993 to 1997 a study of spatial distribution of most important weeds in apple orchard herbicide strips was performed. This study was continued in 1998, once the trees were cut down. As the time progressed, <i>Epilobium adenocaulon</i> Hausskn., <i>Chenopodium album</i> L., <i>Polygonum aviculare</i> L. and <i>Atriplex patulum</i> L. showed an increase in their occurrence. An opposite tendency was found with <i>Erigeron canadensis</i> L., <i>Convolvulus arvensis</i> L. and Taraxacum fficinale Web. Some species grew in patches (Convolvulus arvensis L., Chenopodium album L., <i>Atriplex patulum</i> L.), while the others appeared sporadically throughout the orchard. In 1998, the decrease of occurrence of <i>Epilobium </i> Haussk. was observed. Simultaneously, this was coupled with an increase of occurrence of <i>Taraxacum officinale</i> Web., <i>Erigeron caanadensis</i> L. and <i>Chenopodium album</i> L. The predominating species in 1998 was <i>Cerastium vulgatum</i> L., followed by <i>Lolium perenne</i> L., <i>Poa annua</i> L. and <i>Bromus mollis</i> L.

Characteristics of a potyvirus associated with a mosaic-like disease of yellow oat-grass

The properties of a new filamentous virus found on yellow oat-grass (suggested name <I>Trisetum flavescens mosaic virus</I> – TFMV) were compared with those of the two potyviruses <I>Oat mosaic virus (</I>OMV) and <I>Oat necrotic mottle virus</I> (ONMV). The latter viruses were chosen because their host range, virus particles and some other characteristics are similar to TFMV. Mechanical transmission of TFMV to some OMV and ONMV host plants, drop precipitation, indirect-ELISA, DAS-ELISA, SSEM and RT-PCR were used in the study. However, there was no proof that TFMV is identical with OMV or ONMV. <I>Avena abyssinica</I> and <I>Bromus mollis</I> were found to be new experimental hosts of TFMV.&nbsp;

Peach Tree Vegetative and Root Growth Respond to Orchard Floor Management

Peach (Prunus persica L. Batsch. `Biscoe'/Lovell) trees were grown in a sandy loam soil under six orchard floor management systems, including five vegetative covers (continuous under the tree) and a vegetation-free control (bare ground). At the end of the fifth year, trees grown in bare ground and nimblewill grass (Muhlenbergia schreberi J.F. Gmel.) had a significantly larger trunk cross-sectional area (TCSA) than trees grown in weedy plots, centipedegrass [Eremochloa ophiuroides (Munro) Hack.], or bahiagrass (Paspalum notatum Flugge). Trees grown in brome (Bromus mollis L.) did not differ significantly in TCSA from any other treatment. Soil profile excavations of the root system revealed that trees grown in bare ground or with nimblewill had significantly higher root densities than those in the weedy plots or grown with bahiagrass. Vector analysis of root distribution indicated that trees grown in bare ground or nimblewill rooted deeper than trees in all other treatments. The greatest reduction in deep rooting occurred with bahiagrass.

GRASS SEED PRODUCTION: WEEDS, HERBICIDES AND FERTILISERS

Four weed species (Bromus mollis, Vulpia sp., Poa annua, Steltaria media) occur in 30% or more of all perennial ryegrass seed samples. Of the listed undesirable species, Avena fatua (wild oat) and Hordeum murinum occurred respectively in 5.3 and 3.5% of ryegrass seedlots. Only 6 herbicides are registered for use in grass seed crops in New Zealand, 2 for wild oat, and 4 for broadleaved weeds. The results of research on weed control in seedling and established seed crops (ryegrass, cocksfoot, tall fescue, phalaris, prairie grass) are presented. Fertilisers for grass seed crops discussed are nitrogen (N), phosphorus (P), potassium (K), lime and zinc. Autumn N is commonly used and will increase seed yields in early flowering species (Pestuca rubra, F. arundinacea), but in ryegrass variable results have occurred. Spring N should be applied at stem elongation. No responses to P have been reported for ryegrass, while in established cocksfoot responses to P and K have been reported. Overliming can induce Zn deficiencies, and of the grass species only prairie grass may require lime. Keywords: Lolium, ryegrass, seed production, weed occurrence, Bromus mollis, herbicides, fertilisers, nitrogen, phosphorus, potassium, lime, zinc

Effects of cattle grazing, sheep grazing, cutting and sward height on a grass-white clover sward

SUMMARYThirteen defoliation treatments were applied to a grass-white clover sward for 2 years to study some effects on the sward of cattle grazing compared with sheep grazing compared with various cutting treatments and to study the effect of height of defoliation.Sheep actively sought out the clover in preference to grass whereas the cattle did not. The response of the clover to sheep grazing was a large reduction in the amount of stolon, shorter internodes, petioles and leaflets, and thinner stolon closer to the ground. Reducing the height of defoliation from 8 to 4 cm above ground level also reduced the dimensions of white clover. The clover, however, appeared to recover quickly and completely from the effects both of sheep grazing and of reducing the height of defoliation when these treatments were discontinued. In plots cut for hay the clover disappeared from the sward suddenly and completely in dry conditions following the 2nd-year hay cut. The effect of cattle grazing on white clover was similar to the effect of comparable cutting treatments. Cattle grazing, however, reduced the number of tillers of grass andincreased the proportion of bare ground, compared with cutting or sheep grazing. Grazing rather than cutting tended to encourage perennial ryegrass and to discourage Holcus. Cutting for hay encouraged Bromus mollis. Reducing the height of defoliation reduced leaf sheath and blade length and the rate of production of new blade per tiller in perennial ryegrass, but increased the numbers of tillers of grasses.