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Measuring the methane to carbon dioxide ratio (CH4/CO2) from animals could be useful to predict CH4 yield when dry matter intake (DMI) cannot be measured. The objectives were to (1) evaluate the relationship of CH4/CO2 with CH4 yield; (2) compare the CH4/CO2 of 10–60 simulated spot-samples with the CH4/CO2 calculated with data from 48-h of respiration chamber measurements. The DMI and CH4 and CO2 emissions measured every 5–6 min in respiration chambers from a previous experiment with 70 lambs fed ryegrass substituted with 0%, 25%, 50%, 75% and 100% of forage rape were retrieved. Emission data were used to perform simulations of 10, 20, 30, 40, 50 and 60 randomly selected spot-samples per lamb. The CH4/CO2 of 20 or more spot-samples was useful to predict CH4 yield and detect differences between dietary treatments, while the precision of the prediction increased when increasing the number of spot-samples up to 50 samples per lamb. Twenty spot-samples were sufficient to obtain accurate CH4/CO2 estimates; however, variance decreased (precision improved) with an increasing number of spot-samples per lamb up to 50 spot-samples. The CH4/CO2 of 10–60 simulated spot-samples explained 61% to 66% of variation in the 48-h measured CH4 yield. [ABSTRACT FROM AUTHOR]

Pasture seed samples that were harvested around 1917 in New Zealand were analysed for purity, Epichloë endophyte and insects. Samples consisted of 13 packets of seed varying from 2.2 to 15.0 g and comprising, Chewings fescue (Festuca rubra L.), cocksfoot (Dactylis glomerata L.), oat (Avena sativa L.), perennial ryegrass (Lolium perenne L.) and red clover (Trifolium pratense L.). These findings show that in the period prior to modern seed testing laboratories only four of the 13 samples (31%) could possibly have met today's seed certification standards as it relates to seed purity. When compared with published purities and weed content of seed of the era these samples appear typical. Endophyte testing on the four ryegrass seed samples and the ryegrass contaminants found in the Chewings fescue and cocksfoot samples showed sample-to-sample variation in endophyte infection from nil to 91%. One cocksfoot sample, most likely harvested from the Banks Peninsula, contained an Argentine stem weevil. Subsequent checking of entomological collection records also revealed specimens being present in the Wellington region from 1916. Together these occurrences precede the earliest published record for the species in New Zealand by ten years and suggest that it may have been widespread at that time. [ABSTRACT FROM AUTHOR]

Plantain (Plantago lanceolata L.) is a forage that produces secondary metabolites with one, aucubin, known to inhibit soil nitrification. This study aimed to quantify the exudation of aucubin and catalpol by plantain root systems in a hydroponic experiment; evaluate the effect of aucubin on nitrogen (N) leaching and nitrous oxide (N2O) emissions from urine applied to plantain and ryegrass-white clover swards; and compare N losses from a ryegrass-white clover sward after urine from cows fed plantain and cows fed ryegrass-white clover was applied. Nitrate ( NO 3 − ) leaching and N2O losses were measured in a lysimeter experiment. Catalpol, but not aucubin, was exudated by plantain roots. N2O emissions were decreased by plantain swards and by ryegrass-white clover swards to which aucubin was also applied. Aucubin had no effect on NO 3 − leaching. Urine from cows grazing plantain had no effect on N2O emissions, and N leaching when compared to the urine from cows grazing ryegrass-white clover with the same N content. We conclude the plantain sward and the aucubin applied to the ryegrass-white clover sward decreased N2O emissions via mechanisms in the soil separate from the decreased emissions resulting from the lower N concentration of urine derived from cows grazing plantain. [ABSTRACT FROM AUTHOR]

The productivity of perennial ryegrass (Lolium perenne L.) is constrained by summer water deficit. We hypothesised that selection for desirable water relations traits might partially mitigate this constraint. Genotypes of a 1970s, and two recent ryegrass cultivars were grown in 55 cm tall pots for three months and exposed to moisture deficit for four weeks, then 66 plants were assessed for shoot (SDW) and root (RDW) dry weight, leaf elongation rate (LER), specific water use (SWU), leaf osmotic potential (OP), OP change, leaf relative water content (RWC), and gravimetric soil moisture. Among the 66 genotypes, SWU ranged from 935 ± 19 to 1754 ± 74 g H2O g–1 DM. In principal component (PC) analysis, PC1 indicated greater growth and lower SWU from greater soil water extraction as the common trait association among genotypes tested and ANOVA of PC scores indicated that recent cultivars outperformed the 1970s cultivar. PC2 indicated water saving by decreased LER and SDW, with increased RDW indicative of summer dormancy. PC3 associated more negative OP with improved SWU and RWC. This experiment demonstrates not only genotypic diversity for SWU but also diversity in trait associations determining SWU, which should be considered when investigating SWU, both in ecology and agronomy research. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate forage mass, morphological, and chemical composition of diploids and tetraploids Italian ryegrass cultivars in hydromorphic soil. Eight ryegrass cultivars were evaluated in a two-years completely randomised trial with four plots per cultivar. Forage production was recorded, and samples were collected to evaluate morphological and chemical composition. The contrasts methodology was used to verify differences between diploid and tetraploid cultivars. Compared to tetraploids, the diploids had the greatest number of cuts and the largest accumulation of forage in the second year, highlighting the better adaptation of cultivars in hydromorphic soils. Tetraploid ryegrass increased leaves and reduced stem and inflorescence proportion relative to diploid ryegrass. Tetraploid cultivars had lower DM, organic matter, and acid detergent fibre content than diploid cultivars. However, there was no significant difference between cultivars associated with their ploidy for the neutral detergent fibre and estimated total digestible nutrients. Additionally, only in the second year, tetraploid had lower crude protein content than diploid ones. Tetraploid ryegrass showed be less tolerant to periods of water stress due to flooding, characteristic of hydromorphic soils, resulting in less forage production than diploid ryegrass. [ABSTRACT FROM AUTHOR]

Combining several cultivars within species in seed mixtures is often advocated as a means for improving crop or pasture performance. Herbage accumulation (HA) of perennial ryegrass-white clover pastures sown with a single cultivar representing different functional types of perennial ryegrass was compared with the HA of cultivar mixtures over three years in two contrasting environments (Waikato, dryland; Canterbury, irrigated) under dairy cattle grazing. Functional types were: mid-season flowering diploid, late-season diploid, and late-season tetraploid. Mixture treatments (n = 4 at each site) included all binary combinations plus the three-way combination. Mixture HA and the mean HA of the constituent cultivars did not differ for any of the mixture combinations in either environment, apart from winter in Waikato where the mid-diploid plus tetraploid mix out-yielded the mean of the individual cultivars and tended to increase total annual HA. The total annual HA of the mixtures was between 1.0 and 2.3 t DM/ha/year less than the HA of the highest-yielding individual cultivar included in the mixture in six of the eight mixture-environment combinations. While some benefits of mixtures for controlling grazing outcomes were observed, sowing individual high-performing cultivars is a better overall strategy than mixing cultivars to cover a spectrum of traits. [ABSTRACT FROM AUTHOR]

The objective was to determine the effect of grazing fodder beet versus ryegrass-dominant pasture from mid-to-late gestation on dam and offspring performance under practical farming conditions. Twin-bearing ewes were randomly allocated to grazing regimes of either fodder beet plus ad libitum ryegrass/clover hay (FB; n = 100) or ryegrass-dominant pasture plus ad libitum ryegrass/clover hay (RG; n = 100) with three replicates per group, from pregnancy day (P) 100–110 to birth. At P135, 10 ewes per treatment were randomly selected from each replicate, slaughtered and back fat and eye muscle depth and fetal body weight and composition were measured. Samples were evaluated for selected blood metabolites. Ewe BW and BCS change and lamb growth were measured, and lamb survival from birth to weaning calculated. Compared with RG, FB ewes had lower ADG and overall lower BCS resulting from increased mobilisation of both fat and muscle. Lambs born to FB-ewes had lower BW and postnatal growth rates and increased mortality from birth to weaning (29% versus 12%). Body composition and blood parameters indicated that FB compared to RG ewes were subject to undernutrition. This study provides new insights into the consequences of FB grazing regimes, as an alternative to ryegrass pasture, on animal performance. [ABSTRACT FROM AUTHOR]

Keywords: Clover; grass; legumes; forage; alfalfa; herbicide resistance; buttercup; chicory; proximal hyperspectral sensing EN Clover grass legumes forage alfalfa herbicide resistance buttercup chicory proximal hyperspectral sensing 249 251 3 05/17/22 20220801 NES 220801 In this special issue of NZJA, we have collected papers that focus on new science in the discipline of plant sciences. Ranunculus acris control in dairy pasture - a comparison of herbicides, plant growth promoters, a bioherbicide and pregraze mowing. Clover, grass, legumes, forage, alfalfa, herbicide resistance, buttercup, chicory, proximal hyperspectral sensing Continuing the legume theme, Gerard et al. ([7]) present an interesting data set comparing yields of eight perennial clover cultivars under field conditions over two years. [Extracted from the article]

The objective of this study was to investigate the relationship between plasma amino acid (AA) concentration and urinary nitrogen (N) concentration of dairy heifers offered cut plantain or perennial ryegrass-white clover pasture indoors. Twelve Jersey-Friesian heifers aged 9–10 months were equally assigned to two dietary treatments (plantain vs. perennial ryegrass-white clover pasture) in a completely randomised design. Urinary N concentration was lower in plantain fed heifers (1.4 g/kg) than in perennial ryegrass-white clover pasture fed heifers (3.4 g/kg). Feeding cut plantain or perennial ryegrass-white clover pasture did not have an effect on either plasma essential AA, non-essential AA or total AA. There was no association found between plasma AA concentration and urinary N concentration in the present study. Therefore, the urinary N concentration reduction in plantain fed heifers compared with perennial ryegrass-white clover pasture cannot be attributed by the differences in plasma AA. [ABSTRACT FROM AUTHOR]

In New Zealand, a commonly sown pasture combination is perennial ryegrass with white clover. The hydrothermal time model (HTT) was used to quantify germination under different temperature (T) and water potential (WP) conditions for white clover 'Nomad' and perennial ryegrass 'Stellar AR1'. Seeds were germinated in vitro under a range of T × WP combinations, and HTT models were fitted to germination time course data. Rapid germination of white clover under optimum T and WP was reflected by a much lower value for its HTT constant compared with perennial ryegrass (10.8 vs 80.7 MPa °C d). However, the lower base water potential for perennial ryegrass (−1.29 vs −0.495 MPa) and a higher threshold temperature for thermoinhibition (21.8 vs 18.3°C), meant that predicted perennial ryegrass germination was more resilient in warm dry conditions. HTT models can be used to assist decisions about the timing of perennial ryegrass and white clover sowing. [ABSTRACT FROM AUTHOR]

We tested whether selection of ryegrass for reduced root hair length and density would reduce root competition on white clover for phosphate (P). A Rhizosheath Selection Tool was used to select two ryegrass populations with contrasting root hair traits. These were grown at five soil P levels in a glasshouse experiment and rhizosheath trait selection had no effect on growth or shoot P concentrations. The ryegrass populations were also grown with white clover in soils with Olsen P12 or 19 mg L−1. In the Olsen P12 soil, clover grown with the smaller rhizosheath ryegrass had significantly heavier shoots and contained more P than clover grown with the larger rhizosheath ryegrass. In the Olsen P19 soil differences in ryegrass rhizosheath had no effect on clover growth. The results showed that under the experimental conditions, grass-clover competition for soil P could be modified by the rhizosheath traits of ryegrass. [ABSTRACT FROM AUTHOR]

Ryegrass is the primary pasture crop in New Zealand; however, despite this importance, gains in yield through conventional breeding have been marginal. Other significant crops, particularly maize and rice, have benefited from hybrid breeding programmes whereby heterosis has been exploited. Ryegrass presents many challenges to breeders wishing to produce F1 hybrid progeny on a large scale such as self-incompatibility, inbreeding depression, and a lack of genetic tools for creating and maintaining male-sterile lines for crossing. Many of these challenges have been overcome in other species, providing a basis for addressing them in ryegrass. With the advent of new technologies such as CRISPR gene editing and the genome sequence for ryegrass, F1 hybrid production is now possible on a large scale. Regulations in New Zealand surrounding new genetic tools are a hurdle which must be addressed to allow the agricultural industry in New Zealand to apply these advanced technologies. [ABSTRACT FROM AUTHOR]

This experiment investigated the feasibility of using herb-clover mixes to enable early weaning of lambs at ∼60 days of age. Over two years, twin lambs weighing more than 16 kg were allocated to three treatments: ryegrass pastures until 90 days-of-age, herb-clover mix until 90 days-of-age or weaned at ∼60 days of age onto herb-clover mix. In 2014, lambs offered the herb-clover mix, weaned at 60 or 90 days, were heavier at 90 days than lambs grazing on pasture with their dams. In 2015, lambs that weaned early onto the herb-clover mix were lighter at the same age as lambs that remained with their dam, but they still achieved a commercial weight. Ewes weaned early were heavier at weaning than ewes suckling lambs on ryegrass pasture in both years. Under some conditions, early weaning of lambs onto a herb-clover mix can be an effective alternative to conventional weaning on ryegrass pasture. [ABSTRACT FROM AUTHOR]

The objective of this study was to quantify amino acid (AA) profiles in plasma collected from dairy heifers grazing swards containing ryegrass/clover, chicory and plantain in autumn and spring. The study comprised a 28-day autumn trial and a 21-day spring trial using 56 Friesian x Jersey heifers. Total AA concentrations ranged from 2849 to 3165 μM in autumn and from 3195 to 3454 μM in spring, with no treatment effect. Season affected essential AA (EAA) and total AA concentrations. Total plasma AA concentrations were lower in autumn (2965 μM) than in spring (3303 μM). Based on these results, feeding dairy heifer's either pure chicory, binary mixture or pure plantain does not affect EAA and total AA of Friesian x Jersey heifers. Further, no relationship was established between AA and weight gain of heifers in this study. [ABSTRACT FROM AUTHOR]

The aim of this research was to assess the potential of using perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) forages containing plantain (Plantago lanceolata L.) (PRGWC + Plantain) to mitigate nitrate (NO3−) leaching in grazed grassland. Lysimeter studies were carried out to determine NO3− leaching losses from the PRGWC + Plantain forage, compared with the standard perennial ryegrass and white clover forage (PRGWC) under three different irrigation conditions (flood, rotorainer and pivot). Fresh dairy cow urine (700 kg N ha−1) was applied to these lysimeters in early summer (December) and late summer (February). Nitrogen (N) dynamics and the abundance of ammonia oxidising bacteria (AOB) and archaea (AOA) were also determined in companion mini-plots alongside the lysimeters. Nitrate leaching losses from the PRGWC + Plantain forage were 82% lower than those from the PRGWC forage when urine was applied in December and 74% less when urine was applied in February (P < .05). This was possibly due to the release of biological nitrification inhibitors by plantain which slowed down the nitrification process and this, combined with a lower drainage volume, was largely responsible for the lower NO3− leaching losses in the PRGWC + Plantain forages. The three different irrigation schemes did not significantly affect NO3− leaching losses under the two forage types. These results demonstrate the potential of using PRGWC + Plantain forages as an effective mitigation option for NO3− leaching in grazed grasslands. [ABSTRACT FROM AUTHOR]

Pasture mitigation strategies are needed to reduce the negative effects of nitrate (NO3−) leaching from intensive pastoral livestock production systems. We explored the capability of pasture grasses with different cool season (winter-early spring) growth rates to reduce NO3− leaching and increase N uptake. Following a single urine application of 700 kg N ha−1, NO3− leaching loss and N uptake by Italian ryegrass and four perennial ryegrass cultivars of varying seasonal growth (heading dates from -7 to +20 days), either undersown with/without Italian ryegrass, were quantified in a 12 month lysimeter study. Italian ryegrass cv. Tabu had lower NO3−-N leaching loss and drainage, and greater N uptake and DM yield than perennial ryegrass varieties. Italian ryegrass total N leaching loss (143 kg N ha−1 yr−1) was 46-33% less (P < .05) than early and mid-season maturing Tyson, Arrow and AberDart perennial ryegrass. Italian ryegrass total N uptake (463 kg N ha−1) was 1.2-1.4 times greater than all other grass sward types. Overall, perennial ryegrass pure swards had similar N uptake and N leaching. Late-season maturing One 50 perennial ryegrass showed significantly reduced (P < .05) total N leaching loss. Undersowing Italian ryegrass into established perennial ryegrass swards resulted in lower NO3− leaching and greater N uptake than non-undersown perennial ryegrass swards, though not significant. Results confirm Italian ryegrass is a useful pasture grass option for reducing annual N leaching loss. Cool season perennial ryegrass varieties appear not to influence soil N uptake and leaching loss. [ABSTRACT FROM AUTHOR]

Irrigated, diverse pastures were managed under normal (grazed to 3.5 cm) or lax (grazed to 5 cm allowing ryegrass seed head development) grazing intensity, with or without mowing (to 3.5 cm), in spring. On the subsequent grazing rotation in summer, an experiment was conducted to investigate the carry-over effects of previous management on herbage regrowth and milk production. Nine groups of three Friesian × Jersey dairy cows each were randomly allocated to three replicates of three treatments: normal grazing (Norm); previously lax managed pastures (Lax); previously lax managed pastures that were pre-graze mown (Mow). Herbage in Mow treatments had a higher ME (p < 0.05) than Lax and Norm (11.7, 11.3 and 11.4 MJ ME/kg DM, respectively). There was no difference in dry matter intake (18 ± 0.30 kg DM/cow/d) or MS production (1.85 ± 0.02 kg MS/cow/d) among treatments. Results of this study indicated that milk production was not altered by grazing management. [ABSTRACT FROM AUTHOR]

The objective of this study was to assess live weight gain, animal behaviour and N excretion in the urine of dairy heifers fed herbs during autumn and spring. Sixty heifers were allocated into five dietary treatments: 100% ryegrass-white clove pasture (100RG/WC); 50% RG/WC + 50% chicory (50CH); 75% RG/WC + 25% chicory (25CH); 75% RG/WC + 25% plantain (25PL); and 50% RG/WC + 50% plantain (50PL). The 100RG/WC had the highest (5.0 times/6 h) and lowest (2.5 times/6 h) urination frequency compared with other treatments in autumn (averaged 3.5 times/6 h) and spring (averaged 4.5 times/6 h), respectively. The heifer LWG in spring was higher in 25CH (1.36 kg/day) than other treatments (averaged 1.10 kg/day). Urinary N concentration was 0.18% and 0.23% in autumn and spring, respectively, across treatments, with no difference between treatments. The study demonstrated inconsistent results of use of chicory and plantain as a mitigation tool to reduce the environmental impact of heifer rearing systems in autumn and spring. [ABSTRACT FROM AUTHOR]

Herbage accumulation (HA) data from four sites were combined to (1) address the hypothesis that adjustments to the New Zealand Forage Value Index to account for grass-clover interactions are not required and (2) explore the main effects of clover and nitrogen (N) fertiliser treatments on pasture productivity. In summer and autumn, pastures based on mid-season heading ryegrass cultivars consistently supported a greater clover content than pastures based on late heading cultivars. However, the clover ×  cultivar interaction was significant in only 2 of 17 HA data sets available for analysis. Thus, the hypothesis is supported. Compared with ryegrass monocultures, mixtures yielded an additional 2.4 (in the Low-N treatment) and 1.2 (High-N treatment) t DM/ha/year. Apparent N transfer from clover to grass was 79 (Low N) and 27 (High N) kg N/ha/year, derived from estimated N fixation efficiencies of 66 (Low N) and 50 (High N) kg N/t clover DM grown. [ABSTRACT FROM AUTHOR]

Concentrations of boron, cobalt, copper, iron, manganese, molybdenum, selenium and zinc were measured in eight perennial ryegrass cultivars grown at four sites in New Zealand (Waikato, Manawatu, Canterbury and Southland). Herbage samples were collected from pure ryegrass plots, grown with two nitrogen fertiliser rates, with three sites sampled in autumn (April/May 2013) and all four sites in spring (October/November 2013). There were significant differences among the cultivars for most of the elements, but consistent patterns were not obvious due to interactions involving site, season and nitrogen fertiliser treatment. It is concluded that breeding ryegrass for variation in micronutrient concentrations is unlikely to be productive. [ABSTRACT FROM AUTHOR]

Concentrations of nitrogen, phosphorus, potassium, calcium, magnesium, sulphur and sodium were measured in eight perennial ryegrass cultivars grown at four sites in New Zealand (Waikato, Manawatu, Canterbury and Southland). For the macronutrient analyses, herbage samples were collected from pure ryegrass plots, grown with two nitrogen fertiliser rates, with three sites sampled in autumn (April/May) and all four sites in spring (October/November) of 2013. There were significant differences among the cultivars for all elements except potassium, extending the results of earlier research to contemporary commercial cultivars. It is suggested that breeding ryegrass for lowered shoot phosphorus concentration should be prioritised because of the economic and environmental benefits to be gained from farming with reduced phosphate fertiliser requirements. [ABSTRACT FROM AUTHOR]

This paper describes how the core treatments in the national experimental design (all combinations of with/without clover and high/low nitrogen (N)) were implemented at an irrigated Canterbury site and monitored for three years. There was a consistent N × clover interaction, caused mainly by substantially lower yields in the Low N without clover treatment compared with all other treatments. At the phenotypic contrast level, the main effect of perennial ryegrass heading date on white clover content was significant in four of the nine seasonal data sets available: on these occasions, mixtures based on mid-season heading cultivars had higher clover content than later season-heading cultivars. However, this difference was not sufficient to cause any clover × cultivar interactions in herbage accumulation. Hence, the hypothesis that relative yield rankings of ryegrass cultivars do not differ when ryegrass is grown in monoculture or in mixture with white clover is supported. [ABSTRACT FROM AUTHOR]

The implementation and monitoring of the treatments in the core experiment (eight perennial ryegrass cultivars grown under four combinations of plus/minus clover and high/low nitrogen (N)) at a dryland Waikato site is described. The N x clover interaction was significant in 10 of the 17 seasonal or total annual herbage accumulation (HA) data sets available, caused by substantially lower annual HA in the low N minus clover treatment compared with all other treatments. Five significant scaling-type clover × cultivar interactions in HA were evident. In all cases, HA was greater in plus clover than minus clover treatments, but more so for some cultivars than others. However, the interactions were not consistent across seasons, and different cultivars or phenotypic contrast groups were involved in many cases. The hypothesis that relative HA rankings of ryegrass cultivars do not differ when ryegrass is grown in monoculture versus mixtures with white clover is supported. [ABSTRACT FROM AUTHOR]

This experiment, implemented at a Southland site representative of the lower South Island, New Zealand, and monitored for three full years from 2012/2013 to 2015/2016, was one of four throughout New Zealand that investigated the yield and nutritive value rankings of perennial ryegrass cultivars sown with or without white clover and with high (225 kg N/ha/annum) or low (50 kg N/ha/annum) application rates of nitrogen fertiliser. High inputs of nitrogen (N) fertiliser increased annual total dry matter (DM) yields and seasonal yield in 12 out of 18 measurement occasions. Adding white clover increased both annual dry matter yield and seasonal yield in 7 out of 18 measurement occasions. An interaction between clover and N input occurred on 10 occasions. Over time, the low N minus clover treatment became progressively lower yielding compared with the other three treatments. Ryegrass cultivar by clover interactions occurred in the latter half of the experiment. When analysed using ryegrass characteristics, early- and late-heading ryegrass cultivars produced similar yields when sown without clover, but late-heading ryegrass cultivars had a higher yield than early-heading pastures when sown with white clover (P < .001). Tetraploid ryegrasses had lower yields than diploid ryegrasses when sown without clover (P = .001). This difference was reduced when white clover was included. There was no significant interaction with ryegrass morphology when sown with white clover, as dense ryegrass cultivars always had a higher yield than open ryegrass cultivars (P = .005). Interactions occurred between N input levels and ryegrass cultivar. These occurred in early spring or late spring of each year. Analysis by ryegrass characteristics identified consistent interactions. Ryegrass cultivars with a late-heading date were higher yielding than early-heading cultivars at low N inputs (P = .029), but they were not different at high N inputs. Diploid and tetraploid ryegrass cultivars were similar with low N inputs, but diploid cultivars out-yielded tetraploid cultivars at high N inputs (P = .005). Significant interactions between N inputs and white clover addition affected herbage nutritive value but this did not extend to consistent interactions with ryegrass cultivar. Invertebrate pest numbers were generally low and unlikely to have influenced clover/ryegrass interactions or cultivar ranking. Results from this site suggest that ranking of ryegrass cultivars needs to account for both the inclusion of clover and variation in N fertiliser input. [ABSTRACT FROM AUTHOR]

The development of economic indexing systems for ranking cultivars of forage species requires new knowledge of factors that may influence the scaling of agronomic data collected in controlled, small-plot evaluation trials to whole farm systems. In the case of perennial ryegrass indexing, one such knowledge gap is the effect of growing clover with ryegrass on the relative rankings of different ryegrass cultivars. The objective of the investigation reported in this series was to test whether the relative yield rankings of perennial ryegrass (Lolium perenne L.) cultivars representing the range in phenotypes now available to New Zealand farmers as a result of recent breeding differed when those cultivars were grown in monocultures (as per standard protocols for cultivar yield trialling systems such as the National Forage Variety Trials) versus mixtures of grass and clover. This paper presents the rationale for the investigation by reviewing developments in perennial ryegrass breeding and evaluation in the context of grass-clover relationships in grazed pasture systems. The papers that follow report results from a multi-year, multi-site investigation comparing the yield, nutritive value and other productivity-related variables of eight perennial ryegrass cultivars grown with or without white clover (monoculture versus mixture respectively) at two levels of nitrogen fertiliser. Key considerations in the design of the experiment on which the investigation was based are discussed. [ABSTRACT FROM AUTHOR]

A farm systems experiment comparing five pasture-based dairy systems was conducted in south-western Australia over 4 years on an annual ryegrass:subterranean clover sward. Fertiliser N inputs (0, 0.5, 1, 1.5 and 2 kg N ha−1day−1) and stocking rate (SR; 1.25, 1.50, 1.75, 2.0 and 2.25 milking cows ha−1) increased concurrently for each treatment (F1–F5, respectively). By design, milk yield per cow did not differ between treatments; therefore, the response was measured in terms of changes in herbage dry matter (DM) utilisation and nutritive characteristics, as well as differences in feed input and imported forage required. Total annual pasture utilisation (t DM ha−1) increased from treatment F1–F3 (5.1, 5.9 and 7.3 t DM−1ha−1, respectively), but responses beyond treatment F3 were not significant. Mean total N response efficiency was 9, 13, 8 and 7 kg DM per kg applied N for F2–F5, respectively, while mean marginal N response efficiency was 9, 17, −2 and 3 kg DM per kg applied N for F2–F5, respectively. The most efficient use of N fertiliser was achieved on treatment F3, where annual pasture utilisation levels in excess of 7 t DM ha−1yr−1were consistently demonstrated under the management strategies outlined, substantially greater than the local industry average. [ABSTRACT FROM AUTHOR]

Time of urine application on mineral N (Nmin) leaching from a pumice soil was tested. Artificial urine (600 kg N ha−1) was applied in early June or late July to small plots after removing a kale/swede crop or to ryegrass/white clover. Mineral N leached in the first winter (measured by porous cups, 600 mm deep) was similar under pasture or ex-forage crop: 185 vs. 60 kg N ha−1for June or July urine, with 170–300 kg N ha−1remaining in the soil (0–600 mm) at the end of drainage. Additionally, 54–118 kg N ha−1leached in the second winter. In total, later application decreased Nmin leaching by 35–40%. Application of the process inhibitor dicyandiamide increased soil Nmin levels in the post forage crop site for the early urine application but had no effect in the late-applied urine treatment. There was no significant effect on N leaching. [ABSTRACT FROM PUBLISHER]

A plot study was undertaken to investigate the interactive effect of three defoliation intervals (one-leaf, two-leaf and three-leaf stage in perennial ryegrass (PR) and one-leaf, two-leaf and four-leaf stage in tall fescue (TF)) and two defoliation height residuals (low, 5 cm and high, 8 cm) on production parameters of TF compared with PR plots. DM yields, botanical composition and tiller densities of both species were all generally greater at the longest defoliation intervals (TF-4 and PR-3). However, this consistently resulted in the poorest herbage quality in the TF-4 treatment. The herbage quality was higher in TF-2 compared with TF-4; however, the DM yield, tiller density and proportion of sown species in the sward were reduced. It is not possible to achieve an adequate compromise between DM yield, botanical composition, tiller survival and herbage quality in TF, throughout the year, when defoliation occurs at the two-leaf and the four-leaf stages. [ABSTRACT FROM PUBLISHER]

Growth rates of weaned bull calves in late summer/early autumn can be low in a ryegrass/white clover-based system. This experiment compared the liveweight gain of weaned bull calves (n = 18 per treatment per year, in 3 replicates of 6 bulls) grazed on a herb sward comprised of chicory, plantain, red clover and white clover with bulls grazed on either pasture supplemented with 1.8 kg DM/day of concentrate, or pasture without supplementation. The experiment was repeated over three years. Bulls grazed on the herb sward grew faster (P < .05) than bulls grazed on pasture with or without concentrate supplementation. Liveweight gain of bulls grazed on pasture was less than for bulls supplemented with concentrate in two of the three years (P < .05). A herb sward is a better quality alternative to late summer/early autumn pasture, and could be used to increase liveweight gain of bulls during this period. [ABSTRACT FROM AUTHOR]

A set of 18 × 0.5 ha paddocks at the DairyNZ research farm in Hamilton made up from three replicates of six sward mixes had pasture collected weekly from 31 January 2012 to 9 May 2012 and spore counts ofPithomyces chartarumwere determined. Low diversity (LD) meant that the paddock was sown with a single grass species (tall fescue, high sugar cultivar, ryegrass) and white clover. High diversity (HD) meant that the paddock was sown with a single grass species and white clover plus prairie grass, chicory, plantain and lucerne. The study aims were to assess the benefit of diversity and sward type in the control of facial eczema. There was no difference in spore counts over time between high diversity and low diversity pastures (P = 0.43). Both tall fescue paddocks (LD and HD) showed a lower spore count over time in comparison with low diversity ryegrass (P = 0.055 and 0.05). [ABSTRACT FROM AUTHOR]

The objective of this study was to compare the effect of one or two applications of gibberellic acid (GA) or nitrogen (N) fertiliser on dry matter (DM) yield and composition of perennial ryegrass-white clover pasture. Pasture was treated with 0 or 8 g a.i./ha of GA and 0 or 50 kg/ha N fertiliser in a 2 × 2 factorial design in late winter and spring. One application of N fertiliser increased DM yield by increasing leaf mass and tiller density of perennial ryegrass while one application of GA increased DM yield by increasing perennial ryegrass and white clover yield. There was no DM yield response to two applications of GA, though two applications of N did increase DM yield. A single GA application in late winter increased fibre and reduced protein concentration in ryegrass. The use of GA to increase DM yield with reduced herbage protein concentration may have reduced environmental impact through reducing N intake of livestock. [ABSTRACT FROM AUTHOR]

In New Zealand vineyards, evolution of glyphosate resistance in perennial ryegrass (Lolium perenne) has been reported recently, and restricted translocation of glyphosate has been found in these resistant plants. Past research with other plant species has found that restricted glyphosate translocation is temperature dependent. Glasshouse dose-response experiments were conducted with resistant perennial ryegrass at different temperatures to investigate if this population becomes susceptible to glyphosate under cooler conditions. Glyphosate-susceptible plants (population SP) grown in either warm (average of 20 °C) or cool (average of 9 °C) temperatures following treatment with several rates of glyphosate responded similarly to the herbicide regardless of temperature. In contrast, plants of population J (glyphosate resistant) were significantly more resistant than population SP to glyphosate when treated under warm conditions, but at the cooler temperature, population J was as susceptible as population SP. Thus the mechanism of resistance in population J appeared to be suppressed under cool conditions, suggesting that application of glyphosate during winter might improve control of glyphosate-resistant perennial ryegrass infestations. [ABSTRACT FROM PUBLISHER]

Three quick tests were evaluated for detecting glyphosate-resistant biotypes of Italian ryegrass and perennial ryegrass. Biotypes of these two species were used that were 13.4 and 7.3 times more resistant to glyphosate, respectively, than susceptible biotypes when assessed using a sprayed pot study. One assay exposed germinating seeds of resistant and susceptible populations for 8 days to different concentrations of glyphosate. Measurements of reduction in seedling root growth gave an estimate of resistance magnitude of 10.8 and 8.9 for Italian ryegrass and perennial ryegrass, respectively, similar to that from the sprayed pot study. Two other assays were tested and were able to differentiate resistant and susceptible biotypes. One measured the relative levels of shikimic acid in leaves following exposure to glyphosate; four to seven times more shikimic acid accumulated in glyphosate-susceptible populations of Italian and perennial ryegrass than in resistant populations. The other assay involved growing tillers of the plants in glyphosate solutions and the results showed that at glyphosate concentrations of 10 and 40 mg/L, the plantlets of resistant plants showed negligible visual injury and growth reduction compared with susceptible ones. Results obtained from these assays were not affected by whether the glyphosate formulation used was an isopropylamine salt or potassium salt. [ABSTRACT FROM AUTHOR]

Liveweight production was quantified from six dryland pastures at Lincoln University, Canterbury, New Zealand, over an 8 year period. The experiment was a randomised complete block with six replicates. The pastures were established in autumn 2002 with cocksfoot (CF) and subterranean (CF/Sub), balansa (CF/Bal), white (CF/Wc) or Caucasian (CF/Cc) clovers, a perennial ryegrass/white clover (RG/Wc) control and a lucerne (Luc) monoculture. Liveweight (LWt) production from Years 2 (2003–04) to 9 (2010–11) was 7940 kg LWt/ha from the lucerne monoculture, 7270 kg LWt/ha from the CF/Sub pasture and 5680 ± 171 kg LWt/ha from CF/Bal, CF/Wc, CF/Cc and RG/Wc pastures. Annually, LWt production ranged from 443 kg/ha (CF/Wc pastures with hoggets grazing in spring in 2006–07) to 1285 kg/ha from CF/Sub pastures in Year 9 when ewes with twin lambs at foot grazed in spring. On average, grass-based pastures produced 64%–70% of their total annual LWt production in spring compared with 57% from lucerne monocultures. In spring, relationships between LWt and total spring DM yield showed that 7.3 ± 0.68 kg LWt/ha was produced per 100 kg total DM (R2= 0.87) grown in 5 of the 6 years under the hogget/weaned lamb grazing system. Relationships between LWt and metabolisable energy or N yield failed to improve this relationship, which suggests that DM yield from persistent improved pasture components was the major factor responsible for differences in LWt production from these optimally grazed pastures. [ABSTRACT FROM PUBLISHER]

An outdoor grazing study conducted with 45 pregnant, dry dairy cows for 47 days during the winter period measured dry matter (DM) utilisation, DM intake, forage disappearance, body condition score (BCS) and liveweight (LW) of cows fed 11 (K11) or 14 (K14) kg of kale DM per day or 11 (G11) kg DM Italian ryegrass per cow per day. Cows were offered 3 kg DM barley straw/cow/day at 0800 h and their daily forage allowance at 0900 h. Within 6 hours of being offered a fresh forage allocation, cows had consumed more than 86% of their apparent daily DM intake with cumulative DM intake of 10.4, 10.5 and 7.3 kg DM/cow for K11, K14 and G11, respectively. Daily percentage DM utilisation averaged over the 47 days of the trial was higher for K11 (96%) and K14 (88%) than for G11 (70%), leading to higher apparent daily DM intake for K14 (12.1 kg) and K11 (10.5 kg) than for G11 (7.9 kg DM). Liveweight and BCS gain during the 47 days were higher for K14 (45.4 kg LW and 0.3 BCS units) and G11 (46.8 kg LW and 0.3 BCS units) than for K11 (30.1 kg LW and 0.2 BCS units). This study indicates that compared with offering the common industry allowance of 11 kg kale DM/cow/day, increasing the allowance to 14 kg kale DM/cow/day or offering grass at 11 kg DM/cow/day may lead to higher BCS and LW gain, although all regimes failed to meet expectations of cows gaining 0.5 BCS units during the winter feeding period. [ABSTRACT FROM PUBLISHER]

A botanical survey of 24 commercial dairy pastures ranging in post-sowing age and perennial ryegrass type (mid-season diploid, late-season diploid, tetraploid) was undertaken in each of Waikato-Bay of Plenty (BoP), Taranaki and Canterbury during autumn/winter. The mean perennial ryegrass proportion (85% of total DM) and tiller density (3252 m−2) was greatest in Canterbury and the broadleaved weed proportion lowest (2%). Conversely, Waikato–BoP had the lowest ryegrass proportion (59%), tiller density (1817 m−2) and greatest proportion of broadleaved weeds (15%), with Taranaki intermediate. Tiller density was greater in pastures sown with diploid rather than tetraploids (averaging 3033 vs. 1784 m−2). Grass grub (Costelytra zealandica, 11 m−2) populations were lowest in the youngest age category pastures where nematode populations were highest (80 g−1dry soil). The soil seedbank was dominated by unsown species (with total species emergence averaging 4594 seeds m−2), with negligible ryegrass emergence. [ABSTRACT FROM PUBLISHER]

Genetic control of herbage yield—a complex trait of fundamental importance to agricultural productivity—was characterized in a perennial ryegrass biparental mapping population (I×S). Seasonal and combined growth score estimates of herbage yield (GS) were obtained from a trial conducted at three sites in New Zealand, over 2 years. Twenty-nine quantitative trait loci (QTL) for GS were identified on an I×S genetic linkage map constructed using simple sequence repeat (SSR) markers. Most QTL explained less than 15% of the phenotypic variation. QTL consistency was low among and within trial sites and years but 17 QTL were observed in more than one environment or season. QTL on linkage groups (LG) 1, 2, 4 and 6 were most consistent, based on numbers of QTL co-located at these positions and persistence of their allelic effects. SSR markers from consistent QTL positions may be beneficially applied in marker-assisted selection to enhance genetic gain for herbage yield in ryegrass breeding. [ABSTRACT FROM PUBLISHER]

Soil phosphorus (P) concentrations in excess of those required to maximise pasture production impose unnecessary costs on farmers and potentially increase the risk of P runoff to waterways. The relationship between soil available P concentration and pasture production was examined on an Oxyaquic Hydrosol. Mean annual pasture production ranged from 18,415 to 21,834 kg DM/ha over the 3-year sampling period. There was no significant difference in the annual DM production at Olsen P concentrations of 23-81 mg/kg measured from the 0-75 mm sampling depth. Results show that there was no increase in pasture production when soil Olsen P concentrations exceeded 23 mg/kg (0-75 mm). The optimum soil Olsen P ranges determined in the current study are well below the mean paddock concentrations previously measured in northwest Tasmania (54 mg/kg) and suggest that such high concentrations are not justified in terms of optimising pasture growth. [ABSTRACT FROM AUTHOR]

The plant growth regulator trinexapac-ethyl (TE) is widely used to enhance ryegrass seed yields by reducing lodging (i.e. delaying collapse of the crop). However, lodging data are usually a single evaluation related to TE rate for a particular date of measurement. In eight field trials with varying rates of TE, weekly lodging assessments were made from full head emergence and days to 50% lodging were determined. In all trials, dynamic assessment of TE treatment showed there was a strong positive correlation (R 2 = 0.82) between the number of days to 50% lodging and seed yield. Nil TE reached 50% lodging in 7 days compared with 33 days for TE treatments of 400 g ha-1. On average, one days' delay in reaching 50% lodging increased seed yield by 24 kg ha-1 (response range 16-33 kg ha-1). The data indicate that TE rate per se is less important than the rate required to delay the date that 50% lodging is reached. The seed yield response was linear for delayed lodging from full head emergence to harvest, suggesting that the highest yields are achieved if the crop is not more than 50% lodged at harvest. [ABSTRACT FROM AUTHOR]

Perennial ryegrass (Lolium perenne L.) can be sown as a mixture of cultivars, but different eco-physiological mechanisms among cultivars can cause the cultivar proportions to change over time. The objectives of this work were to differentiate the cultivars 'Barnhem', 'Barmaco', 'Barlet' and 'Mara', and to identify their proportions in mixture. Two seed-lots of each cultivar were characterised using one simple sequence repeat (SSR) and two inter-SSR (ISSR) markers. Simulated mixtures based on random sub-samples from monocultures of each cultivar showed that individuals could be correctly allocated to their respective seed-lot and cultivar with 78-87% accuracy using discriminant analysis. 100 BG34 plants were collected from three dairy pastures in Ohio, USA and their SSR/ISSR profiles were compared with the reference populations. One pasture had a similar cultivar proportion as the original sown mixture. Two pastures had increased proportions of 'Mara' and 'Barmaco' and decreases of 'Barlet' or 'Barnhem', depending on the pasture. [ABSTRACT FROM AUTHOR]

A lysimeter experiment evaluated the use of sawdust or sucrose to decrease nitrogen (N) leaching from newly deposited urine patches to a perennial ryegrass/white clover pasture on sandy loam soil. Cow urine (equivalent to 500 kg N ha-1), labelled with 15N-urea, was applied to the surface of lysimeters and sawdust (9 t ha-1) or sucrose (3, 12 or 24 t ha-1) was applied immediately afterwards. Sawdust did not decrease mineral N leaching compared with urine-only (82 kg N ha-1). Sucrose applied at 12 or 24 t ha-1 decreased mineral N leaching by 27 or 66%, compared to urine-only. Pasture dry matter yields were decreased in all sucrose treatments (range 16-29% over 247 days, but 15-73% over the first 70 days) compared with urine-only. Total recovery of 15N in pasture and soil was similar across treatments (average 66%) but the 15N partitioning between soil and pasture differed; soil recovery was 19% in the urine-only and urine + sawdust treatments, and 27-51% in the sucrose treatments, increasing with increasing rate of sucrose. In the farm situation, the risk of yield loss and the large carbon applications required may limit the practical application of this N mitigation method. [ABSTRACT FROM AUTHOR]

The effects of one cycle of selection for adventitious root system shape (i.e. percentage of total root mass in successive depth increments) were investigated in progeny of four perennial ryegrass pools with contrasting rooting patterns: (1) low surface (0-10 cm) root mass and roots to 1 m; (2) high surface root mass and roots to 1 m; (3) high root mass 10-20 cm and roots to 1 m; (4) high surface root mass, shallow rooting. Ten half-sib families were selected from each of the root type progenies, and five seeds from each family were sown and raised as stock plants. Tiller cuttings of each plant were planted into individual 1 m deep root screening tubes of sand and irrigated with nutrient solution After 115 days, the shoots were cut off, the sand/root column cut into 10 cm increments and the roots washed free of sand. The shoots and root samples were oven-dried and weighed. The four root shape progeny groups did not differ significantly for shoot or root dry weight (DW), or root/shoot DW ratio. Root type 2 (high surface root mass and roots to 1 m) progeny had a significantly higher percentage of total root mass between 0 and 10 cm than did root type 1 (low surface root mass and roots to 1 m) but none of the other differences were significant for percentage roots 0-10 cm. The root type 2 progeny had a lower percentage of total root DW between 10 and 20 cm than all the other root types, none of which differed and had a significantly lower percentage of root DW 20-30 cm than types 1 and 4 but did not differ at this depth from type 3 progeny. The probability of root type 4 (high surface root mass, shallow rooting) plants having roots at 1 m depth was 0.67; this was significantly lower than for the other selections, none of which varied significantly. These results indicate that it should be possible to change root system shape in perennial ryegrass using conventional breeding techniques. [ABSTRACT FROM AUTHOR]

Agronomic trials at cool (Gore) and warm (Palmerston North) temperate sites in New Zealand tested ten United Kingdom-bred (six diploids, four tetraploids) and two New Zealand-bred diploid ('Bronsyn', 'Impact') perennial and long-term hybrid ryegrasses (Lolium perenne, L. boucheanum) over two trial periods. Dry matter (DM) yields and persistence were better at the cool site but differential expression among cultivars for water-soluble carbohydrates (WSC) and yields was small compared with the warm site. The tetraploid cultivars generally had the highest concentrations of WSC but also on occasions had higher levels of crown rust, moderate DM yields and poorer persistence compared with diploids. Two of the tetraploid cultivars will be of value for their high WSC and good agronomic performance at the cool site. Some of the diploid UK cultivars expressed higher WSC and had similar or higher annual DM yields than some of the NZ-bred cultivars, and had high levels of resistance to crown rust. Overall, differences among cultivars in expression of WSC were small. Some differences occurred for seasonal DM yields with some UK cultivars having lower winter yields. [ABSTRACT FROM AUTHOR]

The objective of this study was to improve the McCall herbage growth model. A more mechanistic senescence function was incorporated, replacing an empirical senescence function. The new function is based on leaf lifespan (LLS), measured in thermal time, which is characteristic of a given grass species, and can be measured independently or sourced from the literature. Other complementary changes were also incorporated, the major ones being to incorporate soil water infiltration constraints and to improve seasonal predictions in winter based on greater photosynthetic efficiency of leaves at low light intensity. The existing and new versions of the model were each calibrated against five time series of herbage growth data using the first half of each time series. The second half of each time series was used for validation, along with an independent dataset. A suite of goodness-of-fit indicators was used to evaluate and compare the existing and new versions of the model. The new version more accurately predicted herbage growth following calibration, showing higher concordance correlation coefficients (ρ c = 0.59, 0.62, 0.81, 0.81 and 0.53 versus 0.85, 0.88, 0.81, 0.88 and 0.80, for existing and new versions respectively). Most goodness-of-fit indicators also improved for the independent dataset (e.g. ρ c = 0.708 versus 0.787, for existing and new versions, respectively). It is concluded that the new improved version of the model can be confidently used as a replacement for the existing version [ABSTRACT FROM AUTHOR]

The leaf regrowth stage of perennial ryegrass (Lolium perenne L.) is an effective and generic measure to determine the optimum time for defoliation and reflects important physiological processes. Previous research suggests that uptake of phosphorus (P) fertiliser by perennial ryegrass during regrowth may vary with leaf development stage, however little research has been undertaken in this area. The current study aimed to characterise P uptake with sequential leaf development, in order to provide knowledge which could be used to improve the efficiency of P fertiliser uptake. A glasshouse study was used to investigate the uptake of P by ryegrass grown in soil with optimum P fertility. Results showed a positive linear relationship between the 10-leaf stage increments (ranging from 0 to 4 leaves) and both the change in P content in leaves and P uptake by the whole plant (leaves, tiller bases and roots) (P < 0.001 for both relationships and R² = 0.58 and 0.48 respectively). The linear relationship showed that an increasing amount of P was removed from the soil as the regrowth cycle progressed and, although P uptake was greatest at the 4-leaf stage of regrowth, the optimum time of defoliation for perennial ryegrass is between the 2-leaf and 3-leaf stages of regrowth. This suggests that the greatest uptake of P by the plant can be enabled by providing adequate soil P availability prior to the optimum 2-leaf to 3-leaf defoliation interval. [ABSTRACT FROM AUTHOR]

Gibberellins are plant hormones that activate dormant enzyme systems. Applied to pasture, they can stimulate out-of-season growth or accelerate growth through reserve mobilisation, leaf and stem elongation, and promotion of flowering. When evaluating gibberellin as a potential pasture production stimulant, historical investigations frequently used rates ranging from 25-700 g/ha of active ingredient. Responses were found to be uneconomic, and there were often side effects including a decrease in tillering, decreased root mass, and a yield depression subsequent to the initial response. With gibberellic acid now available from China at comparatively cheaper prices than applied historically, and emerging understanding that application rates as low as 5-10 g/ha active ingredient can produce more cost-effective responses, possibly with reduced side effects, there is renewed interest in gibberellin use to increase winter and spring pasture production or manipulate seasonality of production. a rationale for delivery of extension advice is presented. [ABSTRACT FROM AUTHOR]

Root and shoot dry weights (DW), and root DW depth distribution were determined for wild type perennial ryegrass, breeding lines and cultivars. The plants were grown in 1 m deep tubes of sand culture in a glasshouse experiment. There were significant differences in shoot DW among accessions in the wild types but not within the bred material, and the wild types had more accessions with low shoot DW. Root DW varied significantly among accessions in both the bred material and the wild types. There were significant differences in root/shoot DW ratios among accessions, and between pools in the breeding lines, but no differences within the wild types. Root/ shoot ratios in the wild types had a much narrower and generally higher range of values than those in the bred lines. The percentage of root DW in the top 10 cm of sand did not vary significantly in the bred lines but it did in the wild types. Variation was recorded in root DW depth distribution at both the accession and genotype levels. We concluded that selection for merit based on shoot performance does not necessarily result in large root systems, and better plant performance might result from an increase in root system size in perennial ryegrass. [ABSTRACT FROM AUTHOR]

Interspecific hybridisation between tetraploid Lolium perenne L. (Lp) and L. multiflorum lam. (Lm) was investigated by using morphological genetic markers. Fluorescent-root and awned-floret phenotypes are dominant in Italian ryegrass (L. multiflorum), so seed-parent Italian ryegrass plants were emasculated to eliminate the possibility of self-fertilisation. The percentages of germination were 84.3% in LP x Lm and 90.6% in Lm x Lp crosses. The fluorescent seedlings were 81.8% in Lp x Lm and 83.7% in Lm x Lp crosses, and interspecific hybrids were 88.8 and 97.3%, respectively. The percentage of self-fertilisation was 4.0% in the perennial ryegrass. Pollen viability was 90.2% in the Lp x Lm and 91.0% in the reciprocal cross. The direction Lp x Lm seems to be a suitable method to produce interspecific hybrids on a mass scale. [ABSTRACT FROM AUTHOR]

The article discusses a breeding project aimed at producing ryegrass cultivars with branched inflorescences in New Zealand. The first cultivar produced was the GA143, which achieved about double the number of florets compared with unbranched cultivars. It is said that the breeding project was continued by transferring the branched character into annual and hybrid ryegrass which resulted to three germplasms including GA189 perennial ryegrass, GN190 hybrid ryegrass and GB191 Italian ryegrass. The characteristics of each germplasm are described.

Rhizobium populations were counted in random soil samples from a ryegrass/clover pasture, in soil around white clover plants, and also in the rhizoplane of the white clover roots. The random soil samples contained 3 x 105 cells per g dry soil of Rhizobium leguminosarum bv. trifolii effective on its host, and the same number of Mesorhizobium loti. Soil around white clover plants had 106 cells per g dry soil of each Rhizobium. In the rhizoplane of white clover there were 106 effective R. leguminosarum bv. trifolii per mg root dry weight, and only 10³ M. loti per mg root dry weight. The increase in the ratio of effective white clover rhizobia to M. loti in the rhizoplane demonstrates species-specific stimulation of effective rhizobia on the root surface. This would be important for the ongoing cycles of effective nodulation required by the clonal growth habit of white clover in pasture. [ABSTRACT FROM AUTHOR]