Department of Agricultural Sciences

Yield and phytotoxicity responses of subterranean clover (Trifolium subterraneum L.) sprayed with different herbicides for broadleaf weed control

Fri, 31 Mar 2017 00:00:00 GMT

Yield and phytotoxicity responses of subterranean clover (Trifolium subterraneum L.) sprayed with different herbicides for broadleaf weed control Lewis, Teresa Rose A key factor for integrating subterranean clover into pastoral systems is its success in the establishment year. With appropriate management, establishment ensures productivity and persistence in future years. This thesis investigated the relative herbicide tolerance of subterranean clover at the seedling stage for pasture establishment in New Zealand rain-fed environments. This involved quantification of the field response to herbicides, at different seedling development stages of subterranean clover cultivars. Four experiments, two arranged as split-plot, and two as split-strip-plot, were established in Canterbury, New Zealand in autumn 2016. Emergence of Experiments 1 and 2 occurred in late-March, while Experiments 3 and 4 were delayed by lack of rainfall. A cultivar*herbicide interaction was identified in all experiments, confirming that cultivars were different in their response to herbicides. The cultivar ‘Narrikup’ showed the greatest herbicide tolerance to imazethapyr across all experiments, with sown clover yields of 2600-3500 kg DM/ha. All yanninicum cultivars (‘Monti’, ‘Napier’, and ‘Trikkala’) were not suited to the environmental conditions of the season and failed to persist following herbicide applications. The subterranean clover subspecies brachycalycinum cultivar ‘Antas’ showed variable herbicide tolerance, with responses of developmental delay as well as yield depression. The white clover control was consistently the lowest yielding at <1000 kg DM/ha, with no response to herbicides. Subterranean clover cultivars had visible phytotoxicity responses to imazethapyr which were related to plant pubescence. The phytotoxicity scores were correlated to yields within each experiment. ‘Whatawhata’, ‘Woogenellup’, and ‘Narrikup’ cultivars showed the greatest tolerance and benefit from imazethapyr, with total clover yields of 3500-4500 kg DM/ha for the growing season, >2000 kg/ha more than their unsprayed unweeded controls. For cocksfoot/clover mixtures only ‘Narrikup’ had no reduction in total dry matter yields compared to unsprayed unweeded controls when imazethapyr was applied. Cocksfoot productivity was slowed by imazethapyr up to 24 weeks after application, with yields 750 kg/DM lower than the unsprayed unweeded controls. Pastures recovered to be no different in November, and cocksfoot can be expected to continue to provide summer grazing after the annual clovers set seed. The early reduction in cocksfoot productivity allowed >20% increases in the clover component of imazethapyr treated swards. Experiments 3 and 4 found that the ALS-inhibiting herbicides imazethapyr and flumetsulam, and photosynthesis-inhibitor bentazone were the least damaging herbicides to subterranean clover. Experiment 3, where plants were treated at the 1-2 trifoliate leaf stage had higher subterranean clover yields when compared to Experiment 4, where herbicide was applied at the 4-6 trifoliate leaf stage. The early seedling herbicide application had less impact on yields than prolonged competition from weeds. Combined sown+resident clover yields showed that sowing cultivar mixes can improve subterranean clover herbicide tolerance and increase total yields. Both application times for Imazethapyr, flumetsulam, and bentazone had mean total clover yields the same as or greater than the unsprayed unweeded controls. 2,4-DB had a negative impact on the development of all subterranean clover plants. For the remaining herbicides bentazone + MCPB, bromoxynil + diflufenican, and MCPB, ‘Antas’ and resident ‘Woogenellup’ were susceptible to developmental delays as a result of application, while ‘Denmark’ and ‘Narrikup’ were less adversely affected. Imazethapyr + saflufenacil, and glyphosate treatments killed all vegetation and left ground bare in all experimental applications, confirming they are unsuitable for use in subterranean clover-containing pastures. This research confirmed a cultivar*herbicide interaction to a range of herbicides, and identified imazethapyr, flumetsulam and bentazone as suitable for use during establishment of subterranean clover based pastures. Longer term effects, such as those on subsequent regeneration and further investigations into effects on development, as well as the apparent brachycalycinum susceptibility are advised.

In vitro fermentation characteristics of ryegrass-white clover sward containing different proportions of chicory

Sun, 01 Jan 2017 00:00:00 GMT

In vitro fermentation characteristics of ryegrass-white clover sward containing different proportions of chicory Al-Marashdeh, Omar; Cheng, L.; Gregorini, Pablo; Edwards, Grant Chicory (Cichorum intybus) is a deep-rooted grazeable forage used to overcome production and nutritive value shortfalls of perennial ryegrass (Loliun perenne) and white clover (Trifolium repens) swards during summer drought periods in New Zealand. Despite the wide use of chicory, limited data is available on its fermentation characteristics, and how those affect rumen fermentation pattern and, thereby, nutrient supply from ryegrass-white clover based swards including chicory. The objective of this study was to evaluate the in vitro fermentation characteristics of ryegrass-white clover sward containing different proportions of chicory. Herbages containing 100% ryegrass-white clover (Ch0); 25% chicory + 75% ryegrass-white clover (Ch25%); 50% chicory + 50% ryegrass-white clover (Ch50%); and 100% chicory (Ch100%) were incubated using the Daisy II-200/220 incubator (ANKOM Technology, NY). Treatments, Ch0, 25%, 50% and 100%, were randomly assigned to the four fermentation jars over two runs. The pH, volatile fatty acids and ammonia-N concentrations of fermentation liquor were measured at 4, 8, 12, 24 and 48 hours of incubation. Data were analysed using repeated measures ANOVA with chicory proportion as treatment effect, incubation time as time effect and run as replicate. The pH, mean concentration of ammonia-N, propionate, acetate and butyrate were not affected by treatment (P > 0.05), averaging at 6.5 ± 0.02, 19.1 ± 1.98, 5.3±1.12, 20.2 ± 3.37and 3.3 ± 0.66 mmol/l, respectively. Current results showed that fermentation pattern of herbage containing increasing proportions of chicory is similar to the ‘conventional’ ryegrass-white clover, suggesting that including chicory in conventional swards might not alter the nutritive value of herbage.

Are faecal egg counts approaching their 'sell-by' date?

Sun, 01 Jan 2012 00:00:00 GMT

Are faecal egg counts approaching their 'sell-by' date? Greer, Andrew W.; Sykes, Andrew R. Historically, the primary determinant for the state of parasitism has been the concentration of nematode eggs in the faeces (FEC). This descriptor has a number of limitations that have implications for the development of drug resistance and hamper the identification of resilient livestock. A major fallacy is that FEC can reliably assess the worm burden, the need for anthelmintic and the efficacy of that treatment. FEC is a ratio, eggs per gram of faeces, not a quantity. Not only is the denominator ignored but interpretation of the numerator requires knowledge of nematode species present and female fecundity which can be affected by infra-population dynamics. By definition, a parasite exists at the expense of its host. As such, the consistent ability of resilient animals to maintain performance, despite a high FEC, strongly suggests that FEC does not provide a reliable indicator of the cost of parasitism. This manuscript reviews the factors that affect FEC and argues for a step change in our approach to the control of nematode parasitism in pastoral systems to one focused on individual treatments based on animal performance utilising radio-frequency electronic identification and automated weighing and drafting systems.

Growth and feed quality of five perennial ryegrass (Lolium perenne L.) cultivars under three water treatments

Wed, 02 Aug 2017 00:00:00 GMT

Growth and feed quality of five perennial ryegrass (Lolium perenne L.) cultivars under three water treatments Zhong, Keren Growth and feed quality of five perennial ryegrass cultivars were compared under three water treatments: non-stress (field capacity, FC), mid-stress (50% FC) and high-stress (30% FC). There were three New Zealand cultivars (Alto, Bronsyn and Trojan), one Morrocan cultivar (Barberia) and one cultivar from Norway (Norway). Water stress reduced dry matter production, leaf water content, leaf width, and leaf photosynthetic rate and stomatal conductance of all cultivars by similar amounts. In contrast, water stress increased feed quality (dry matter digestibility and metabolizable energy) but again with no consistent cultivar effect. Averaged over all cultivars, the magnitude of the reduction in dry matter production (44% under high-stress and 21% under mid-stress) was substantially greater than that of the increase in feed quality (2% under mid-stress and 4% under high-stress for dry matter digestibility, 3% under mid-stress and 5% under high-stress for metabolizable energy). For all cultivars, dry matter production and feed quality returned to normal after rehydration of high water stressed plants. It appears that it will be very difficult to develop a cultivar with maintained growth under water stress conditions. However, against this, perennial ryegrass cultivars in general have a strong ability to recover from drought which is an extremely important characteristic in perennial pastures subject to periodic water stress.