Effects Of Ryegrass Research Articles

Positive effect of Ca addition on the risk of Cu and Zn in digestate as biofertilizer

The addition of Ca in anaerobic digestion will passivate the heavy metals in digestate. The effects of CaCl2, Ca(OH)2 and CaCO3 addition on the anaerobic digestion process and the speciation changes of Cu and Zn in solid fraction of anaerobic digestate (SFD) after digestion were studied. Then the effects of Ca-containing solid fraction digestate (SFD-Ca) application on the speciation changes of Cu and Zn in soil and the effects of ryegrass on the enrichment of Cu and Zn were also explored through pot experiments. The results indicated that: The addition of Ca(OH)2 was beneficial to the transfer of Cu and Zn from the liquid fraction of anaerobic digestate (LFD) to SFD, and the transfer effect was the best. The transfer amount of Cu and Zn increased by about 10.0% and 4.2%, respectively, compared with the blank group. The SFD-Ca promoted the increase of biomass, inhibited the enrichment of Cu and Zn by ryegrass, and the effect of a high concentration of Ca(OH)2 was the best. Ryegrass biomass increased by 19.7%, and the enrichment of Cu and Zn decreased by 39.3% and 31.1%, respectively. High concentration of Ca(OH)2-containing solid fraction digestate (SFD-Ca(OH)2) had the best passivation effect on Cu and Zn in soil, the residual state of Cu and Zn in soil increased by 4.3% and 7.8%, respectively. Adding a high concentration of Ca(OH)2 had a positive effect on ryegrass biomass and reduced the risk of Cu and Zn when SFD was used as biofertilizer.

Response of Intestinal Microbiota to the Variation in Diets in Grass Carp (Ctenopharyngodon idella)

The intestinal microbiota is important for the nutrient metabolism of fish and is significantly influenced by the host's diet. The effect of ryegrass and commercial diets on the intestinal microbiota of grass carp was compared in this study. In comparison to ryegrass, artificial feed significantly reduced the microbial diversity in the intestine, which was measured by a decrease in the observed OTUs, ACE, Shannon, and the InvSimpson index. Although grass carp fed with ryegrass and artificial feed shared a dominant phyla Firmicutes and Proteobacteria, the microbial composition was clearly distinguishable between the two groups. In grass carp fed with ryegrass, Alphaproteobacteria, Gammaproteobacteria, and Actinobacteria predominated, whereas Bacilli was significantly higher in the artificial feed group due to an increase in Weissella and an unassigned Bacillales bacteria, as well as a significant increase in a potential pathogen: Aeromonas australiensis. Grass carp fed with ryegrass exhibited a more complex ecological network performed by the intestinal bacterial community, which was dominated by cooperative interactions; this was also observed in grass carp fed with artificial feed. Despite this, the increase in A. australiensis increased the competitive interaction within this ecological network, which contributed to the vulnerable perturbation of the intestinal microbiota. The alteration of the microbial composition through diet can further affect microbial function. The intestinal microbial function in grass carp fed with ryegrass was rich in amino acids and exhibited an increased energy metabolism in order to compensate for a low-nutrient diet intake, while the artificial feed elevated the microbial lipid metabolism through the promotion of its synthesis in the primary and secondary bile acids, together with a notable enhancement of fatty acid biosynthesis. These results indicated that diet can affect the homeostasis of the intestinal microbiota by altering the microbial composition and the interspecific interactions, whilst microbial function can respond to a variation in diet.

The Effect of Ryegrass Silage Feeding on Equine Fecal Microbiota and Blood Metabolite Profile.

Silage is fed to horses in China and other areas in the world, however, knowledge about the impact of feeding silage on horse health is still limited. In the current study, 12 horses were assigned into two groups and fed ryegrass silage and ryegrass hay, respectively, for 8 weeks. High-throughput sequencing was applied to analyze fecal microbiota, while liquid chromatography–tandem mass spectrometry (LC–MS/MS) based metabolomics technique was used for blood metabolite profile to investigate the influence of feeding ryegrass silage (group S) compared to feeding ryegrass hay (group H) on equine intestinal and systemic health. Horses in group S had significantly different fecal microbiota and blood metabolomes from horses in group H. The results showed that Verrucomicrobia was significantly less abundant which plays important role in maintaining the mucus layer of the hindgut. Rikenellaceae and Christensenellaceae were markedly more abundant in group S and Rikenellaceae may be associated with some gut diseases and obesity. The metabolomics analysis demonstrated that ryegrass silage feeding significantly affected lipid metabolism and insulin resistance in horses, which might be associated with metabolic dysfunction. Furthermore, Pearson’s correlation analysis revealed some correlations between bacterial taxa and blood metabolites, which added more evidence to diet-fecal microbiota-health relationship. Overall, ryegrass silage feeding impacted systemic metabolic pathways in horses, especially lipid metabolism. This study provides evidence of effects of feeding ryegrass silage on horses, which may affect fat metabolism and potentially increase risk of insulin resistance. Further investigation will be promoted to provide insight into the relationship of a silage-based diet and equine health.

COMPARATIVE DISSIPATION OF ANTHRACENE AND PHENANTHRENE IN A PRISTINE TYPIC HAPLUDOLL SOIL

Polycyclic aromatic hydrocarbons (PAHs) are of great environmental concern due to their widespread occurrence and persistence. Anthracene and phenanthrene (C14H10) are two priority pollutants that are found in high concentrations in PAHs-contaminated surface soils. The objective of this study was to analyze the capability of endogenous soil microorganisms of a pristine soil of the Pampas region, Argentina, to dissipate two isomers: anthracene and phenanthrene. Nutrient availability and the effects of ryegrass (Lolium perenne L.) on these PAHs´ dissipation were also evaluated. After 100 days, both contaminants were significantly degraded in root-free soils by autochthonous microorganisms. L. perenne significantly enhanced microbial degradation. The dissipation of both pollutants in the rhizosphere was accompanied by higher values of total bacteria counts at the end of the experimental period. No biostimulation effect was observed. In all cases, the dissipation of phenanthrene was significantly higher than anthracene. These results point to the important role of indigenous PAH degrading microorganisms, even present in a non-polluted soil.

Non-leguminous winter cover crop and nitrogen rate in relation to double rice grain yield and nitrogen uptake in Dongting Lake Plain, Hunan Province, China

Annual ryegrass (Lolium multiflorum Lam.), a non-leguminous winter cover crop, has been adopted to absorb soil native N to minimize N loss from an intensive double rice cropping system in southern China, but a little is known about its effects on rice grain yield and rice N use efficiency. In this study, effects of ryegrass on double rice yield, N uptake and use efficiency were measured under different fertilizer N rates. A 3-year (2009–2011) field experiment arranged in a split-plot design was undertaken. Main plots were ryegrass (RG) as a winter cover crop and winter fallow (WF) without weed. Subplots were three N treatments for each rice season: 0 (N0), 100 (N100) and 200 kg N ha−1 (N200). In the 3-year experiment, RG reduced grain yield and plant N uptake for early rice (0.4–1.7 t ha−1 for grain yield and 4.6–20.3 kg ha−1 for N uptake) and double rice (0.6–2.0 t ha−1 for grain yield and 6.3–27.0 kg ha−1 for N uptake) when compared with WF among different N rates. Yield and N uptake decrease due to RG was smaller in N100 and N200 plots than in N0 plots. The reduction in early rice grain yield in RG plots was associated with decrease number of panicles. Agronomic N use efficiency and fertilizer N recovery efficiency were higher in RG plots than winter fallow for early rice and double rice among different N rates and experimental years. RG tended to have little effect on grain yield, N uptake, agronomic N use efficiency, and fertilizer N recovery efficiency in the late rice season. These results suggest that ryegrass may reduce grain yield while it improves rice N use efficiency in a double rice cropping system.

Possible evidence for contribution of arbuscular mycorrhizal fungi (AMF) in phytoremediation of iron-cyanide (Fe-CN) complexes.

Arbuscular mycorrhizal fungi (AMF) are integral functioning parts of plant root systems and are widely recognized for enhancing contaminants uptake and metabolism on severely disturbed sites. However, the patterns of their influence on the phytoremediation of iron-cyanide (Fe-CN) complexes are unknown. Fe-CN complexes are of great common interest, as iron is one of the most abundant element in soil and water. Effect of ryegrass (Lolium perenne L.) roots inoculation, using mycorrhizal fungi (Rhizophagus irregularis and a mixture of R. irregularis, Funneliformis mosseae, Rhizophagus aggregatus, and Claroideoglomus etunicatum), on iron-cyanide sorption was studied. Results indicated significantly higher colonization of R. irregularis than the mixture of AMF species on ryegrass roots. Series of batch experiments using potassium hexacyanoferrate (II) solutions, in varying concentrations revealed significantly higher reduction of total CN and free CN content in the mycorrhizal roots, indicating greater cyanide decrease in the treatment inoculated with R. irregularis. Our study is a first indication of the possible positive contribution of AM fungi on the phytoremediation of iron-cyanide complexes.

Effect of ryegrass (Lolium multiflorum L.) growth on degradation of phenanthrene and enzyme activity in soil

A 75-day pot experiment was carried out to study the effect of growth of ryegrass (Lolium multiflorum L.) on degradation rate of spiked phenanthrene (the concentration was 5, 50, 200 mg/kg) in soil. The results showed that ryegrass growth enhanced the degradation of phenanthrene spiked in the soil, thus making the content of extractable phenanthrene lower (P < 0.05) in the ryegrass planted pots than that of pots without ryegrass. In the treatments of 5, 50 and 200 mg/kg of phenanthrene, phenanthrene degradation rate reached 81.1, 90.4 and 85.0%, respectively, while in pots without ryegrass they were only 73.5, 86.2 and 67.6%, respectively, and ryegrass growth shorted phenanthrene half-life. Ryegrass growth enhanced activities of polyphenol oxidase, dehydrogenase and increased the content of microbiological biomass carbon, thus raised the degradation rate of phenanthrene in the soil. High concentration of phenanthrene inhibited soil biological activity, and in turn the effect of soil biology on phenanthrene degradation. Therefore, the findings disclose the biological and enzymological mechanisms of the plant enhancing phenanthrene degradation. It was also found that ryegrass is rather tolerant to polycyclic aromatic hydrocarbons, but high phenanthrene concentration affected ryegrass growth.

Influence of root-exudates concentration on pyrene degradation and soil microbial characteristics in pyrene contaminated soil

The effect of ryegrass (Lolium perenne L.) root-exudates concentration on pyrene degradation and the microbial ecological characteristics in the pyrene contaminated soil was investigated by simulating a gradually reducing concentration of root exudates with the distance away from root surface in the rhizosphere. Results showed that, after the root-exudates were added 15d, the pyrene residue in contaminated soil responded nonlinearly in the soils with the same pyrene contaminated level as the added root-exudates concentration increased, which decreased first and increased latter with the increase of the added root-exudates concentration. The lowest pyrene concentration appeared when the root exudates concentration of 32.75mgkg−1 total organic carbon (TOC) was added. At the same time, changes of microbial biomass carbon (MBC, Cmic) and microbial quotient (Cmic/Corg) were opposite to the trend of pyrene degradation as the added root-exudates concentration increased. Phospholipid fatty acid (PLFA) analysis revealed that bacteria was the dominating microbial community in pyrene contaminated soil, and the changing trends of pyrene degradation and bacteria number were the same. The changing trend of endoenzyme-dehydrogenase activity was in accordance with that of soil microbe, indicating which could reflect the quantitative characteristic of detoxification to pyrene by soil microbe. The changes in the soils microbial community and corresponding microbial biochemistry characteristics were the ecological mechanism influencing pyrene degradation with increasing concentration of the added root-exudates in the pyrene contaminated soil.

Phosphorus fertilizer induced changes in the soil available P, the P nutrition and the growth of Pinus radiata seedlings grown in association with understory

A study was carried out to investigate changes in the soil plant-available P, the P nutrition and the growth of Pinus radiata seedlings grown in association with understory, broom (Cytisus scoparius L.) or ryegrass (Lolium multiflorum) on Orthic Allophanic Soil, following the application of three rates of triple superphosphate (TSP) (0, 50, and 100 mg·kg−1P) under a glasshouse condition. The application of P fertilizer enhanced P availability in the rhizospheric of radiata seedlings and the bulk soils in a P-deficient site. P availability in the rhizospheric soils of ryegrass and broom, grown in association with radiata, were also increased by the presence of radiata roots. P concentrations in new shoot needles, old shoot needles, stem and roots of radiata pine increased with increase rates of TSP application, but the effects of ryegrass and broom on P nutrition of radiata seedlings depended on the soil P status. In the absence of P fertilizer addition (control treatment), P concentrations in new shoot needles, old shoot needles, stem, and roots of radiata grown in association with broom were higher than those with ryegrass, whereas, when P fertilizer was added (50 and 100 mg·kg−1) the P concentration was lower. This is probably related to the growth of broom that may have removed much of the plant-available P in the soil as indicated by the consistently lower Bray-2 P concentration in the rhizosphere soil of radiata in association with broom than that in the rhizosphere soil of radiata in association with grass at the two high P rates. Furthermore, in the high P fertile soil (application rate of 100 mg·kg−1), the dry matter yield of radiata was lower when it was grown with broom than with ryegrass. This result suggests that in moderate to high P fertile soils, P. radiata seedlings grow better with ryegrass than with broom, because broom grows vigorously in high P fertile soil and competes with P. radiata for P and perhaps for other nutrients as well.

The effect of ryegrass ( Lolium perenne) on decrease of PAH content in long term contaminated soil

The biodegradation of polycyclic aromatic hydrocarbons in microecosystems containing long-term contaminated soil was investigated. Soil was contaminated by different chemicals, including PAHs since World War II. Aging of the soil was expected to act as a principal factor limiting biodegradation. Half of the microecosystems contained ryegrass ( Lolium perenne) and long-term selected natural soil microflora originally present in contaminated soil. The others contained contaminated soil with natural microflora only. Half of the microecosystems in each parallel experiment was fertilised with N–P–K fertiliser. Cultivation was carried out at 12 and 18 months in a greenhouse with a natural photoperiod and the ability to degrade 15 chosen PAH was investigated. For analysis, the soil from each pot was divided into three horizontal layers for mutual comparison among layers and each layer was further divided into four equal samples. Soil extracts were analysed using HPLC. After a one-year-cultivation period the content of the monitored PAHs declined to 50%. Mostly, there were no significant differences between the microecosystems. Best degraded were fluoranthene and pyrene, which were the major contaminants present in original soil. Also, other compounds were successfully degraded, even benzo[ a]pyrene and benzo[ ghi]perylene. Dibenz[ a, h]anthracene and indeno[1,2,3- cd]pyrene were the only PAHs, examined that showed no significant degradation. Although some differences between the soil layers were detected, no conclusive trends could be found. However, significantly lower concentrations of PAHs were determined mostly in the bottom layer of the analysed profiles. In vegetated microecosystems the decline of PAHs concentrations was more remarkable after 18 months cultivation.

Effects of perennial ryegrass infected with either AR1 or wild endophyte on dairy production in the Waikato

A 3‐year farmlet experiment was carried out at Dexcel, Hamilton to compare the effects of ryegrass infected with either AR1 (no lolitrem B or ergovaline production) or wild endophyte on milksolids production and cow health. Two farmlets (7 ha each) were managed as self‐contained systems with cows grazing rotationally from September 2000 to May 2003, with 2.6 cows ha–1 in 2000/01 and 3.0 cows ha–1 in 2001/02 and 2002/03. AR1‐infected ryegrass pastures remained free of contamination from volunteer wild‐endophyte‐infected ryegrass plants for at least 3 years after sowing. Mean annual pasture production and ryegrass tiller density were similar for both AR1‐ and wild‐endophyte‐infected ryegrass farmlets in 3 years, with low numbers of black beetle. A combined analysis of the three lactations data showed that cows grazing AR1‐infected ryegrass pastures produced 8.9% more total milk‐solids than cows grazing wild‐endophyte‐infected pastures (318 versus 292 kg cow–1, SED = 9.2, P = 0.006). The difference between treatments averaged across lactations was 0.1 kg milksolids cow–1 day–1, but the magnitude of the difference varied from week to week. This highlighted the benefits of evaluating the effects of endophyte strain over the entire lactation and for consecutive years, in order to include effects of seasonal variations in alkaloid concentration. Milk composition was similar for both treatments in all lactations. Ryegrass staggers occurred in cows grazing wild‐endophyte‐infected pastures in January 2001, coinciding with the highest concentrations of lolitrem B over the three lactations (>3.5 mg kg–1 DM). Cow body temperatures, respiration rates and plasma prolactin concentrations measured during periods of heat stress were only occasionally affected by endophyte treatment. Results from this 3‐year farmlet evaluation demonstrate that renovating pastures with AR1‐infected perennial ryegrass can offer significant improvements in milksolids production and elimination of ryegrass staggers.

Effect of ryegrass intercropping on the yield and net profit of autumn planted sugarcane

Field studies were conducted on the intercropping of ryegrass in autumn planted sugarcane on sandy loam soil at Regional Research Station (PAU), Kheri (Sangrur) during 2000–01 and 2001–02. Cane yield reduced significantly with the sowing of ryegrass as intercrop in sugarcane. However, maximum reduction in cane yield was recorded with the sowing of two rows of ryegrass where double cut was taken for green fodder. The intercropping systems as sugarcane + ryegrass single cut (1:1), sugarcane + ryegrass double cut (1:1) and sugarcane + ryegrass single cut (1:2) gave statistically higher net profit which was of Rs.13904, 4987 and 6338 per hectare more as compared to sole crop of sugarcane. The lowest net profit was observed under the sugarcane + ryegrass double cut (1:2) could be due to the higher competition with the main crop of sugarcane for inputs and natural resources as soil and water. There is need of further research work to find out the fertilizer requirement for sugarcane + ryegrass intercropping because ryegrass response to nitrogen is very high being a high yielding, fast growing and multicut grass.

Milksolids production and farm profitability from different combinations of perennial ryegrass and white clover cultivars: Progress report 2001-2003

2001/2002 and 2002/2003 were the final two seasons of a replicated dairy farm systems trial designed to evaluate the effects of progress in perennial ryegrass and white clover breeding programmes on whole farm productivity and profitability (Economic Farm Surplus, EFS). All the pastures were sown in late autumn 1998. There were four treatments with all combinations of 1980's (80R), and late 1990's (98R) ryegrasses, and 1960's (60C) and late 1990's (98C) white c lover s, each replicated two times in a randomised block design giving eight 4 ha, self-contained farmlets stocked with three Friesian cows/ha and rotationally grazed. In agreement with the first two years of the trial, the last two seasons have demonstrated no major benefit in terms of either milksolids (MS) production or EFS to sowing different combinations of perennial ryegrass and only a small advantage in one season (2001/2002) to sowing new (98C) white clover cultivars. There were no effects of ryegrass or clover cultivar type on total dry matter (DM) production during the last two seasons but, as observed during the first two seasons of the trial, there were differences in the distribution of pasture growth through the year with old ryegrass (80R) treatments having more pasture growth during spring. During 2001/2002 and 2002/2003 the clover content of the swards was determined more strongly by clover type than by the type of companion ryegrass, in contrast to events during the first two seasons of the trial. Thus clover type, rather than a ryegrass x clover interaction, had a small effect on MS production and EFS during 2001/2002, but not 2002/2003, due to significantly higher clover content in both the new clover (98C) treatments than the old clover (60C) treatments. Any differences between ryegrass or white clover cultivars in terms of lower DM production at certain times of the year, and consequent small differences in total DM production and pasture quality caused only minor differences in EFS between treatments because effective farm management decisions compensated for these effects. Keywords: cultivars, dairying, economic farm surplus, milksolids, perennial ryegrass, white clover

A comparison of management regimes for one-year rotational set-aside within a sequence of winter wheat crops, and of growing wheat without interruption. 3. Effects on diseases

Different management regimes for 1-year rotational set-aside were tested in three experiments that followed winter wheat and started in autumn 1988–90. The regimes included operations that prevented the establishment of volunteers or allowed them to establish and persist until either spring or summer, and also altered the distribution of debris from the winter wheat that preceded the set-aside. For comparison, treatments in the set-aside year also included winter wheat.Samples taken in spring from the first test crop showed that there were few significant or consistent effects on leaf diseases of growing the wheat after different set-aside treatments or after winter wheat. There were significant effects of the set-aside treatments on root and stem base diseases but some of the effects, and the apparent absence of others, are not easily reconciled with current understanding of the biology of the pathogens concerned. In summer, eyespot (Pseudocercosporella herpotrichoides) was most severe after winter wheat and least severe after ryegrass. Severity after the other set-aside treatments did not differ significantly. There was more sharp eyespot (Rhizoctonia cerealis) in plots that had been ploughed at the start of the set-aside year, including those sown with winter wheat, than in those that had not. Brown foot rot (Fusarium spp.) was equally severe where the wheat followed wheat or where it followed set-aside treatments that allowed volunteers to develop, and less so where the development of volunteers was prevented. Take-all (Gaeumannomyces graminis var. tritici) was most severe after winter wheat and more severe after set-aside treatments that allowed volunteers to develop and survive through the winter than after those that did not. Effects of ryegrass (Lolium perenne ssp. multiflorum) on take-all in the following wheat were particularly variable, perhaps because ryegrass is a host of both the take-all fungus and of Phialophora graminicola, one of its principal antagonists.

Effects of ryegrass on biodegradation of hydrocarbons in soil

The effects of growing ryegrass ( Lolium perenne L.) on the biodegradation of hydrocarbons was studied in laboratory scale soil columns. Degradation of hydrocarbons as well as bacterial numbers, soil respiration rates and soil dehydrogenase activities were determined. In the rhizosphere soil system, aliphatic hydrocarbons disappeared faster than in unvegetated columns. Abiotic loss by evaporation was of minor significance. Elimination of pollutants was accompanied by an increase in microbial numbers and activities. The microbial plate counts and soil respiration rates were substantially higher in the rhizosphere than in the bulk soil. The results indicate that biodegradation of hydrocarbons in the rhizosphere is stimulated by plant roots.

Green Manuring with Clover and Ryegrass Catch Crops Undersown in Small Grains: Crop Development and Yields

Abstract In three field trials in southern Norway, spring wheat (Triticum aestivum L.) or barley (Hordeum vulgare L.) monoculture was compared with crops undersown with Italian ryegrass (Loliun multiflorum Lam.), white clover (Trifolium repens L.) and subterranean clover (T. subterraneum L.) at three levels of N fertilizer. The catch crops were ploughed in in late October, and the after-effect on succeeding spring wheat or barley crops was determined. The catch crops were more competitive in 1986, when rainfall in spring was abundant, than in 1985, when it was low. Ryegrass was stimulated by N fertilizer, whereas the clovers were repressed owing to increased shading. At ploughing, catch-crop biomass N ranged from 17 to 94, 37 to 155 and 41 to 243 kg N ha−1 for ryegrass, white clover and subterranean clover, respectively. Grain yields (mean of N-fertilized plots), respectively, ranged from 83 to 94, 84 to 110 and 84 to 100% of yields in monoculture. The catch crops reduced weeds. The fertilizer replacement value of ploughed-in white clover was 50–60 kg N ha−1 on loam soil without N fertilizer. Fertilizer N given either of the years decreased the grain yield response to white clover. Yet, the grain yield with white clover plus 60 kg N ha−1 exceeded that on plots receiving 120 kg N ha−1 as mineral fertilizer only. On sandy loam, the aftereffect was much smaller, most likely owing to N loss during wet conditions in the spring. The effect of ryegrass was neutral and that of subterranean clover intermediate.

Effect of ryegrass containing the endophyte (Acremonium lolii), on the performance of associated white clover and subsequent crops

Ryegrass seed lines with (+E) and without (-E) the fungal endophyte Acremonium lolii were sown with white clover. Fewer clover seedlings survived under +E ryegrasses irrespective of whether the plots were mown or grazed. The dominant contrast was an inverse competitive relationship between grass yield and clover seedling survival. A further component unexplained by effects of defoliation or competition is interpreted as an allelopathic effect. Two pot trials, using wheat, were established to determine it there was any residual effect of +E wards on following crops. Wheat grown in soil with a history of +E or-E ryegrass with clover produced higher yields from the-E than the +E soil. However, wheat grown on soil from previously clover-free pastures showed no difference between +E and -E. Residual effects on wheat crops are therefore interpreted as being related to lower nitrogen fertility, as a result of reduced clover growth in +E pastures. Keywords: Ryegrass, endophyte, white clover. competition, vigour. allelopathy, soil nitrogen, wheat yield, Acremonium lolii

The influence of wheat density and spatial arrangement on annual ryegrass, Lolium rigidum Gaudin, competition

The influence of wheat (Triticum aestivum L.) planting arrangement and density on the competitive effect of the weed, annual ryegrass (Lolium rigidum Gaudin), was examined in field experiments over three climatically contrasting years on the central western slopes of New South Wales. Results for three experiments conformed to a common trend. Geometrical arrangement of the crop (rectangularities of 1 to 6.4) at any one of a range of crop densities had no significant effect (P > 0.05) on ryegrass competition, expressed as relative wheat grain yield reduction. However, the effect of ryegrass was substantially reduced by increasing wheat sowing density from 40 or 75 to 200 plants m-2. In analysing models of weed competition a reciprocal yield model (I/ Y = 0.0092 + 0.0037X, r2= 0.89) predicted yield reduction (Y, as per cent of weed-free controls), especially when used with the ratio of weed density to crop density (X), with residual sums of squares lower than for other models.

Competition between Wimmera ryegrass and narrow-leafed lupins

The ways in which Wimmera ryegrass (Lolium rigidum) affects the growth and yield of narrow-leafed lupins (Lupinus angustifolius) were studied in two experiments at Baker's Hill, W.A. (average annual rainfall 650 mm). In the first experiment, Uniharvest lupins and Wimmera ryegrass were grown alone and together starting at two dates. The three rates of ryegrass produced similar biomasses (total dry matter) at maturity (about 8000 kg/ha) but lupin grain yield decreased significantly with ryegrass sowing rate. One effect of ryegrass at the highest sowing rate was to alter the distribution of dry matter in the lupin canopy so that, at the end of the growing season, there was a lower percentage of leaf in the lower part of the canopy and this was associated with less light being received. Water stress in lupins at the end of the growing season was higher at the later planting with ryegrass. A multiple regression analysis showed that 74% of the variation in lupin grain yield between plots was due to variation in lupin height and biomass, and ryegrass tiller numbers in October. Lupins had little effect on ryegrass yield; although there were fewer tillers in the presence of lupins, weights of tillers were higher. In the second experiment, the effects of 38 ryegrass plants/m2 on growth of both Uniharvest and Unicrop lupins grown at a density of 40 plants/m2 were studied. Lupin biomass was unaffected until October but was then reduced significantly by the ryegrass, which yielded 4000 kg/ha dry matter. Grain yield was reduced because fewer pods were produced on lateral branches in both varieties, and on main stems in Uniharvest. The experiments showed that in good growing seasons, in high rainfall areas, lupins will yield grain even when grown with very high densities of ryegrass.

Effect of plant species and organic matter on feeding behaviour and weight gain of larval black beetle,Heteronychus arator(Coleoptera: Sacrabaeidae)

The effect of ryegrass (Lolium perenne), white clover (Trifolium repens), and Lotus pedunculatus on the movement and feeding behaviour of 3rd‐instar larvae of Heteronychus arator (Fabricius) and the influence of organic matter on these responses were studied. In choice chamber tests larvae did not aggregate at plant roots but did aggregate at organic matter (sieved horticultural peat). Weight gain was greater on ryegrass than on white clover or lotus. Organic matter stimulated feeding and increased weight gain. Evidence for both plant roots and organic matter being phagostimulants is discussed.