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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]

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]

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 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]

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]

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]

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]

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]