Summer-dry Environments Research Articles

Growth rates and persistence of annual and perennial clovers

This study quantified the temporal productivity of monocultures of four annual and two perennial clover species in a summer dry environment at Lincoln University, Canterbury, New Zealand. Clovers were ungrazed in the first year to enable natural re-establishment of the annuals, but grazed in the second year.
 In 2019 clover cultivar affected (P<0.001) yield in early spring (24th September) with ‘Viper’ balansa (Trifolium michelianum) producing 5.0 t DM/ha compared (P<0.05) with 3.5 t for ‘Arrotas’ arrowleaf (T. vesiculosum), 3.2 t for ‘Antas’ and ‘Woogenellup’ sub clovers (T. subterraneum), 1.6 t for ‘Kopu’ white clover (T. repens) and 1.2 t for ‘Relish’ red clover (T. pratense). ‘Arrotas’ grew 111 kg DM/ha/d from 14th to 28th August, ‘Viper’ grew 123 kg DM/ha/d from 28th August to 24th September and then 183 kg DM/d to 9th October.
 After a dry autumn in 2020, ‘Kopu’ white and ‘Relish’ red persisted, but only sub clovers ‘Napier’ and ‘Woogenellup’ successfully re-established. By 17th September, accumulated dry matter yield (t) differed with ‘Woogenellup’ sub (4.3) and ‘Relish’ red (3.7) producing more than ‘Kopu’ white (2.8) and ‘Napier’ sub (2.2). ‘Woogenellup’ sub clover grew at 72 kg/ha/day from 20th August to 17th September, which was more than twice the rate of the other clovers (~30 kg/ha/day). These four clovers continued to provide grazable herbage through the second year.
 In 2020 the re-establishment of arrowleaf, balansa and Persian (T. resupinatum) clovers was poor, and each yielded <0.5 t/ha by 17th September, with their plots dominated by weeds. These results confirm monocultures of top flowering annual clovers are productive in their first year but poor re-establishment may occur in their second year. They may therefore be best suited as one-year specialised crops for grazing or conserved feed.
 The earlier growth profiles of the annual compared with perennial clovers suggests there is potential to increase their use in summer dry environments to meet early spring feed requirements of ewes and lambs.

Diversified pastures at the front line of climate change in Northland: farmers experiences, new directions and wider implications for other parts of the country

The persistence of both perennial ryegrass and white clover is challenged under summer-dry conditions. Future climate change projections indicate greater incidence and severity of summer moisture stress for many regions in New Zealand, and therefore, greater pressure on our traditional pasture base. The ‘Northland Diversified Forages Project’ aimed to identify alternative pasture species that provide an advantage in terms of dry matter yield, quality and/or timing of growth within a summer-dry environment, with a particular focus on legumes. A series of mown-plot trial and paddock demonstrations were established across a range of soil types to assess the potential of a wide variety of forage species. Perennial ryegrass and white clover both failed to persist, comprising less than 25% of the sward within 3 years of establishment. Cocksfoot demonstrated potential as a more persistent alternative to perennial ryegrass. However, whilst a range of legumes were successful at increasing the proportion of legume in the sward and total yield in the first year, significant challenges were identified in maintaining functional legumes across multiple years. This raises questions around whether we currently have the right species in New Zealand to adapt to a changing climate.

Resident hill country pasture production in response to temperature and soil moisture over 20 years in Central Hawke’s Bay

The production of resident pastures on rolling hill country was measured in three paddocks over 20 years at Poukawa in Central Hawke’s Bay. The pastures had been routinely fertilised with 250 kg/ha/yr of superphosphate but no pasture renovation, nor nitrogen fertiliser application, occurred during the measurement period. Total annual dry matter (DM) yield ranged from 4.5 to 12.8 t/ha/yr, which shows the level of variability to be expected in this summer-dry environment. The greatest proportion (60-90%) of growth occurred in winter/spring with consistent mean growth rates of 50-62 kg DM/ha/d in September and October. These rates were calculated to be 5.49±0.55 kg DM/ha/°Cd when spring moisture was non-limiting. The pastures had a mean water use efficiency of 16.9±0.34 kg DM/ha/mm of water available (R2 = 0.93). The amount of water available was calculated from a soil water budget based on a plant available water holding capacity of 124 mm (0-1.0 m depth). The results provide coefficients that can be combined with readily available climate data to predict pasture growth rates for feed budgeting purposes. Rainfall data collected on-site was highly correlated (r=0.94) with that predicted from the NIWA virtual climate station network.

Yield and botanical composition of four dryland pastures at Ashley Dene Research Farm over 8 years

Dry matter yield and botanical composition of four grazed dryland pasture types were compared over 8 years in summer-dry conditions at Ashley Dene, Canterbury, New Zealand. The experiment was sown in March 2013 to evaluate cocksfoot (CF)- or meadow fescue/ryegrass hybrid (RG)-based pastures established with either subterranean (Sub) or subterranean and balansa (S+B) clovers. Plantain was included in all pasture types. Perennial ryegrass established poorly on the low soil moisture holding capacity Lismore soil and in Year 2 was re-broadcast into the RG pastures. Despite this, plantain was the main sown species in RG pastures beyond Year 3. Total spring yield was greatest in Year 5 at 6720 kg DM/ha and varied with spring rainfall. Cocksfoot-based pastures had 60% of sown species present in the spring of Year 8, compared with 28% in RG-based pastures. Balansa clover was only present up to Year 5 after a managed seeding event in the first spring. White clover did not persist in the dryland environment past Year 2. Sub clover yield depended on the time and amount of autumn rainfall but contributed up to 45% of the spring yield. Cocksfoot-sub clover pastures appear to be most resilient in this summer-dry environment with variable spring rainfall.

Establishment, production and regeneration of subterranean clovers in the Mackenzie Basin, New Zealand

The ‘Red Flats’ on Omarama Station in the Mackenzie Basin, has a winter cold, summer dry environment and soils with low plant available water (<60 mm in the top 1 m), and low pH(H2O) (5.2) and high aluminium (8 mg/kg) below 75 mm. The site received 3 t of lime, 300 kg sulphur-super, boron (B), molybdenum (Mo) and herbicides to eliminate hieracium (Hieracium pilosella). Twelve cultivars of subterranean clover (Trifolium subterraneaum), ‘Bolta’ balansa clover (T. michelianum), and perennial ‘Rossi’ red clover (T. pratense), were direct-drilled in February 2016. Over the next 3 years their frost tolerance, productivity and persistence were compared with the resident haresfoot clover (T. arvense). Balansa and the subterranean clovers all survived the 2016 and 2017 winters. The subterranean clovers maximum yield was 4.3 t DM/ ha after successful germination in February 2016 when sufficient rain extended the spring growing season into November. Subterranean clover cultivars from subspecies subterraneum yielded well in 2016, averaging 3.3 t DM/ha, as did the brachycalycinum ‘Antas’ with 3 t DM/ha. During the short season of 2017, the subterraneum ssp. cultivars ‘Denmark’ and ‘Karridale’ established the highest ground covers and ‘Antas’ the lowest. In 2018, ‘Antas’ had the lowest emergence rate and autumn yield. ‘Karridale’ had the highest re-establishment rate and the yanninicum ‘Trikkala’ the highest autumn yield (1.3 t DM/ha). Cultivars with low hardseededness ratings were the most successful at re-establishment in autumn 2017. Balansa clover was also persistent. In the favourable 2016 growing season the late-flowering resident haresfoot clover grew into early summer and yielded 3.7 t DM/ha. Red clover yielded 1 t DM/ha in 2016, but did not persist. Results suggest that medium-late flowering softer seeded subterranean clover cultivars and ‘Bolta’ balansa clover, are suitable for this environment.

Intraspecific differences in long-term drought tolerance in perennial ryegrass.

Lolium perenne L. (perennial ryegrass) is the most important pasture grass species in temperate regions of the world. However, its growth is restricted in summer dry environments. Germplasm screening can be used to identify accessions or individual plants for incorporation into breeding programs for drought tolerance. We selected nine perennial ryegrass accessions from different global origins and from a range of climatic and environmental conditions. In addition, the perennial ryegrass cultivar ‘Grasslands Impact’ was chosen as a reference. The accessions were grown for 360 days in a controlled environment through six consecutive drought stress and recovery cycles. We observed intraspecific differences in drought stress responsiveness for shoot biomass and survival from the third stress cycle. An accession from Norway had 50% more shoot dry matter than the next best-performing accession after six drought cycles. Compared with the reference cultivar ‘Grasslands Impact’, shoot dry matter of the accession from Norway was more than seven times higher after six drought cycles, indicating superior performance of this ecotype under drought stress. Drought tolerance was characterized by osmotic adjustment and higher relative leaf water content at low soil moisture levels. Furthermore, the findings of this study identify solute potential as an early predictor of drought stress tolerance. These intraspecific differences can be used in breeding programs for the development of drought-tolerant perennial ryegrass cultivars.

Anisohydric water use behavior links growing season evaporative demand to ring-width increment in conifers from summer-dry environments

Compared to isohydric Pinaceae, anisohydric Cupressaceae exhibited: (1) a threefold larger hydroscape area; (2) growth at lower pre-dawn water potentials that extended longer into the growing season; and (3) stronger coupling of growth to growing season atmospheric moisture demand in summer-dry environments. Conifers in the Pinaceae and Cupressaceae from dry environments have been shown to broadly differ in their stomatal sensitivity to soil drying that result in isohydric versus anisohydric water use behavior, respectively. Here, we first employ a series of drought experiments and field observations to confirm the degree of isohydric versus anisohydric water use behavior in species of these two families that are representative of the Interior West of the United States. We then use experimental soil drying to demonstrate how growth of anisohydric Juniperus osteosperma was more closely tied to pre-dawn water potentials than isohydric Pinus monophylla. Finally, we confirm that measured leaf gas-exchange and growth responses to drying hold real-world consequences for conifers from the Interior West. More specifically, across the past ~ 100 years of climate variation, pairwise comparisons of annual ring-width increment responses indicate that growth of Cupressaceae species (J. osteosperma and J. scopulorum) was more strongly coupled to growing season evaporative demand than co-occurring Pinaceae species (Pinus monophylla, P. edulis, P. flexilis, P. longaeva, P. ponderosa, and Pseudotsuga menziesii). Overall, these experimental and observational results suggest that an a priori distinction based on family and associated hydric water use behavior should lead to more accurate and mechanistically correct dendrochronological reconstructions of growing season evaporative demand (i.e., Cupressaceae) versus antecedent precipitation (i.e., Pinaceae) in summer-dry environments. Moreover, these differences in growth sensitivity to evaporative demand among these groups suggest that incorporating hydric water use behavior into models of forest responses to global warming can provide more accurate projections of future forest composition and functioning.

Plant drought survival under climate change and strategies to improve perennial grasses. A review

The three cool-season perennial forage grasses cocksfoot/orchardgrass, Dactylis glomerata L., tall fescue, Festuca arundinacea Schreb. syn. Lolium arundinaceum (Schreb.) Darbysh., and phalaris/harding grass, Phalaris aquatica L., are of major economic and ecological importance in regions with summer-dry environments. This review considers the constraints that these species are likely to experience under current and predicted increase of droughts due to climate change scenarios in south-eastern Australia, the southern Great Plains of USA and the Western Mediterranean Basin. The review identifies research required to maximise the development and use of C3 cool-season grasses with enhanced resilience to drought while considering the concern of some regulators that these grasses may be potential weeds. The state of knowledge of factors influencing plant drought survival and therefore recovery after stress and long-term persistence is discussed in the light of adaptive strategies. The major research needs identified to enhance traits conferring drought survival include (1) increasing the depth and density of grass root systems to strengthen dehydration avoidance; (2) exploring the biochemical, molecular and hydraulic bases of dehydration tolerance and improving techniques to measure this trait; (3) breaking the trade-off between summer dormancy and forage yield potential and improving understanding of environmental, biochemical and genetic controls over summer dormancy; (4) identifying non-toxic endophyte strains compatible with summer-dormant cultivars of tall fescue to enhance drought survival; and (5) enhancing seed production capability of new cultivars as well as the development of agronomic management packages for promoting stable mixtures combining perennial grasses and legumes. The weed potential of newly introduced summer-dormant cultivars is concluded to be minor. The research directions proposed here should improve pasture grass resilience and forage crop sustainability in Mediterranean and temperate summer-dry environments under the future drier and warmer conditions associated with climate change.

Potential impacts of different spring grazing strategies on lamb finishing in hill country

How does the pasture cover at the beginning of lambing and the grazing strategy used in early spring influence the ability of a hill country sheep and beef farm to finish lambs? The results from an intensive pasture-mowing trial investigating three defoliation intensities (Lax, Moderate and Intense) starting from two herbage masses (1200 or 1500 kg DM/ha) during early spring were used to provide data on potential pasture consumption and feed quality from lambing to weaning for a breeding ewe flock. Using simulation modelling, this pasture data was used to estimate the potential lamb and ewe liveweight changes from birth to weaning at each of three different stocking rates (4.5, 8 and 10.5 twin-bearing ewes/ha) that closely represented the three defoliation intensities originally studied in a mowing trial. The impacts of these early-spring herbage masses and grazing intensities/ stocking rates on subsequent feed requirements and potential lamb finishing during the later summer and autumn period in four contrasting geo-climatic regions of New Zealand were then further investigated using simulation modelling. Variations in ewe and lamb weaning weights were evident and reflected the amount of pasture available through the different grazing management approaches. For all four geoclimatic regions studied, the Intense grazing, high stocking rate strategy generally produced the greatest gross revenue per ha from lamb sales out of the three grazing strategies investigated, though not significantly greater than the moderate stocking rate in summer dry environments. However, under Intense grazing, a high pasture cover (1500 kg DM/ha), in comparison to a low pasture cover (1200 kg DM/ha) at the start of ewe lactation further improved the gross revenue received from lamb sales, especially in the Canterbury and Waikato environments but less so in the Hawke's Bay and Southland environments. These variations demonstrate how iterations based on the same starting properties impact on weaning weight of lambs and post-weaning pasture growth and/or feed quality. Keywords: emergence, feed supply, geo-climatic regions, iteration, lactation, lamb weaning weight, pasture quality.

Persistence of dry matter yield among New Zealand perennial ryegrass (Lolium perenne L.) cultivars: insights from a long-term data set

Persistence of herbage yield is an important productivity trait of grass species and cultivars in New Zealand pastures. However, relatively little is known about genetic variation in this trait, principally because few studies comparing yield have continued beyond 3 years. This paper reports results from a comparison of 25 perennial ryegrass cultivars representing a wide range of functional types and genetic backgrounds conducted under sheep grazing in a summer-dry environment. Dry matter (DM) yield was measured for the first 3 years after sowing, then again in years seven and eight post-sowing, and in year ten post-sowing. Endophyte DNA fingerprinting conducted mid-way through year seven confirmed that, with one exception, ryegrass populations remained true-to-type in the cultivars sown with novel endophyte strains. The cultivar effect on DM yield was statistically significant in all measurement periods. Differences in yields among cultivars in years seven and eight were significantly and positively correlated with yield differences in years one to three (r=0.685 to 0.831 depending on which year contrasts were used). Thus, high-performing cultivars in the early years of the trial were also generally highperforming cultivars in years seven and eight, and vice-versa, indicating a high degree of yield stability in perennial ryegrass cultivars. Yield differences did not appear to be related to differences in cultivar heading date, ploidy, endophyte status, or genetic background. The relationship between yield in year ten and yields in years one to three was much weaker (r=0.392) than the relationship in years seven and eight. Possible reasons for this are discussed. Keywords: Perennial ryegrass; traits; persistence

Pasture establishment on non-cultivable hill country

To determine the best method of pasture establishment on non-cultivable hill country (>20o slope), four treatments were compared in one year on north and south aspects at four sites with contrasting climates and soil types. Sites were located in Waikato (1), Hawke's Bay (2) and Canterbury (1). The treatments included seed mix (grasses, legumes and herbs (GLH); legumes only (LEG)) and sowing time (spring; autumn). Six weeks after sowing, seedling establishment, as a percentage of viable seeds sown, was: i) greater on south than north aspects for perennial ryegrass (31% vs 18%) and birdsfoot trefoil (5% vs 4%); ii) greater for total sown species (14% vs 8%), subterranean clover (7% vs 4%) and red clover (25% vs 14%) in the GLH than LEG mix, but greater for white clover in the LEG than GLH mix (17% vs 8%); iii) greater in autumn than spring for perennial ryegrass (36% vs 13%) and total sown grasses (22% vs 9%) but greater in spring than autumn for lotus (6% vs 3%). Plantain established well in spring in summer-wet environments, while in summer-dry environments establishment was greater in autumn. Broadcasting seed on south aspects during autumn is likely to result in the highest establishment of sown grasses and legumes, but not necessarily of herbs. The trials were conducted in an unusually wet season. Repeating a subset of the treatments at these sites will provide a greater understanding of responses to climatic variation. Keywords: pasture renewal; pasture establishment; pasture mixtures; oversowing.

Feeding systems in summer dry environments for red deer in lactation

An analysis of the pasture growth pattern in a summer- dry environment compared with the feed requirements of breeding hinds shows that the inclusion of a brassica crop can improve feed supply.

Effect of summer irrigation on seasonal changes in taproot reserves and the expression of winter dormancy/activity in four contrasting lucerne cultivars

In the summer dry environment of cool temperate Tasmania, summer irrigation is used to maximise forage production. For lucerne (Medicago sativa L.) this irrigation is likely to interact with winter-dormancy genotypes to influence seasonal changes in taproot reserves and thus, the process of cold acclimation. To test this hypothesis four lucerne cultivars with contrasting levels of winter dormancy (DuPuits: winter-dormant; Grasslands Kaituna: semi winter-dormant; SARDI 7: winter-active: SARDI 10, highly winter-active) were grown in small plots at Elliott, Tasmania, under irrigated or dryland conditions. At each defoliation taproots were sampled and assayed for the concentration of soluble sugars, starch, amino acids, soluble protein, the abundance of vegetative storage proteins (VSP), and the abundance of mRNA transcripts associated with cold acclimation and VSP. Taproot-soluble protein concentrations in DuPuits significantly increased from summer to autumn when plants were grown under dryland conditions. When grown under irrigated conditions, taproot-soluble protein concentrations decreased over summer and increased in autumn for all cultivars. The abundance of VSP increased in summer in all cultivars grown under dryland conditions. Taproot-soluble sugar concentrations increased and starch decreased in autumn for all cultivars grown under both water regimes. Plants grown under dryland conditions showed little change in RNA transcript abundance of cold acclimation genes across all cultivars and sampling dates, while in those plants grown under irrigated conditions, transcript abundance was influenced by sampling date, and for some genes, by cultivar. There was a clear carry-over effect from the exposure of summer drought on the winter-dormancy response. The expression of winter dormancy at an agronomic and molecular level was greater under dryland conditions.

Yield and water use of temperate pastures in summer dry environments

The water use efficiencies (WUE) of a range of temperate pasture species were calculated from measurements on several different dryland and irrigated pastures in Canterbury. The annual WUE ranged from 6.7 kg DM/ ha/mm for a dryland cocksfoot pasture to 40 kg DM/ha/ mm for a dryland lucerne crop grown on a Wakanui silt loam soil. Keywords: Cichorium intybus, Dactylis glomerata, Lolium perenne, Medicago sativa, Trifolium ambiguum, T. michelianum, T. pratense, T. repens, T. subterraneum

Outcomes of the search for new perennial and salt tolerant pasture plants for southern Australia

The potential adaptation of a range of perennial pasture species to recharge environments in southern Australia is reviewed based on their performance in 20 field nurseries in a nationally coordinated project. Species were also evaluated for their suitability to discharge sites where salt and waterlogging are major restraints. Species are ranked according to their potential to be incorporated into farming systems and the scope for further breeding and selection. Medicago sativa L. (lucerne) was the most persistent of the perennial legumes across a diversity of recharge environments. Lotus corniculatus L. (birdsfoot trefoil) showed the most promise on soils prone to waterlogging. Other legumes that showed potential included Cullen australasicum (Schltdl.) J.W. Grimes (tall verbine) and Lotononis bainesii Baker (lotononis). The herb Chicoriyum intybus L. was superior to M. sativa on more acid soils. Phalaris aquatica L. (phalaris) and summer dormant cultivars of Dactylis glomerata L. (cocksfoot), Festuca arundinacea L. (tall fescue) and Lolium perenne L. (perennial ryegrass) were among the most persistent and productive of the perennial grasses. Further exploitation of temperate perennial grass germplasm with increased summer dormancy should be a priority to increase the role of these grass species in lower rainfall, summer-dry environments. Although difficult to establish, the indigenous grasses Austrodanthonia caespitosa (Gaudich.) H.P. Linder (wallaby grass) and A. richardsonii (Cashmore) H.P. Linder were persistent and showed good recruitment. They should be a priority for low rainfall, low input environments. Other grasses that showed promise were Chloris gayana Kunth (Rhodes grass), Secale montanum Guss. (mountain rye), Microlaena stipoides (Labill.) R. Br. (weeping grass), Ehrhata calcycina Sm. (veldt grass) and Bromus stamineus E. Desv. (grazing brome). For discharge environments, Melilotus siculus (Turra) Vitman ex B.D. Jacks. was one of the most salt tolerant legumes and should be a priority for further development. Medicago polymorpha L. (burr medic) appears underutilised in discharge environments. Increasing the waterlogging tolerance of this moderately salt tolerant species would further enhance its potential. Trifolium michelianum Savi. (balansa clover) owed its success in discharge areas more to ‘salt avoidance’ rather than salt tolerance per se. Melilotus sulcatus Desf., T. tomentosum L. and Lotus tenuis Waldst. & Kit. ex Willd. also had traits that may prove advantageous for discharge environments. Within the pasture grasses, Puccinellia ciliata Bor (pucinellia) was superior at sites prone to waterlogging whereas T. ponticum performed better in moderately drained saline sites.

Interactions between influences of genotype and grass competition on growth and wood stiffness of juvenile radiata pine in a summer-dry environment

Clones of radiata pine (Pinus radiata D. Don) were established in two experiments on two contrasting pasture sites in Canterbury, New Zealand, with four levels of competition from grass as main plots within each experiment. Control was extended over the first 5 years at one site, whereas grass at the other site was controlled by a single herbicidal spray immediately after planting. At the latter site, 1 m diameter spots cleared with herbicide were compared with the same size spot created using a woven mat. Grass competition added up to 3 years to a rotation, and the gain from control was correlated with spot size. Competition control was most critical during the first year after planting. Trees grown within spots cleared by mats grew more slowly than those in weed-free spots cleared with herbicide. Green dynamic modulus of elasticity was related to genotype and increased with both slenderness and higher levels of pruning. Significant interactions between genotype and level of competition were observed for growth, indicating that choice of genotype can be a useful way of coping with pasture competition if managers wish to reduce the use of herbicides.

Effects of grazing management on phalaris herbage mass and persistence in summer-dry environments

Grazing management strategies that included resting or intensely utilising pasture on a seasonal basis were compared for their effects on phalaris production and plant frequency (persistence). Experiments were established at 4 on-farm sites (Cootamundra ‘old’, Cootamundra ‘new’, Springhurst and Cavendish) in southern New South Wales and Victoria that had previously been sown to phalaris and were grazed by sheep. At each site, 8 core treatments and extra locally determined treatments were initially imposed in 1993–94 on 2 spatial replicates. In order to determine and describe any year of start effects, treatments were applied again in 1994–95 to plots that had been maintained as controls. The phalaris component of the pastures varied from a minor component to the dominant component depending on site (11–54%). Measurements of botanical composition, available herbage and plant frequency were made between September 1993 and September 1996. Of the core treatments, autumn closure (Cootamundra old and new), winter closure and grazing between defined levels of available herbage (mob stocking) during autumn–winter (Cootamundra old and new, Springhurst), were the most effective in either maintaining or increasing phalaris herbage mass compared to the continually grazed control treatment. In addition, the frequency of phalaris was higher than the control at each of these sites for the autumn–winter mob stocking treatment. These treatments had no effect at the Cavendish site where phalaris was a minor component of the pasture. Rotational grazing, imposed at 2 of the sites (Cavendish and Cootamundra new), led to an increase in phalaris herbage mass compared to continual grazing. A further treatment aimed at encouraging phalaris seedling recruitment by using an extended spring rest until seed fall in summer followed by a rest after the autumn break was imposed at the Cootamundra old site. This treatment increased phalaris herbage mass but did not result in seedling recruitment. The results emphasise the need for periods of rest when buds are regenerating and tillers developing over the autumn–winter period for phalaris pastures in summer-dry environments.

Effects of grazing interval on basal cover of four perennial grasses in a summer-dry environment

The response to variation in grazing interval over the spring–autumn period in southern New South Wales was examined on 4 perennial grass species over 2 years. Plots of phalaris (Phalaris aquatica L. cv. Sirolan), cocksfoot (Dactylis glomerata L. cv. Porto), tall fescue (Festuca arundinacea Shreb cv. Demeter) and a native danthonia (Danthonia richardsonii cv. Taranna), were grazed by sheep every 2, 5 or 8 weeks, either rainfed or given supplementary irrigation. Basal cover was monitored over this period and is combined with measurements of phenological development and herbage mass to explain differences in persistence. The seasons differed with respect to rainfall, 1994–95 being dry compared to 1995–96. Over the 1994–95 season, the relative change in basal cover [RCBC, the ratio of final (May 1995) to initial (September 1994) basal cover] of the 3 introduced perennial grasses was significantly less than 1, which indicated a decline in basal cover over the measurement period. In contrast, RCBC was 1.55 for danthonia. Grazing interval treatments significantly affected RCBC in 1994–95, RCBC increasing with grazing interval. In the 8-week grazing interval, RCBC did not significantly differ from 1. Changes in density were also measured in 1994–95 and followed a similar pattern to RCBC for species effects although there was no significant effect of grazing interval. In 1995–96, there were interactions between watering and both species and grazing interval. The RCBC (September 1995–May 1996) was significantly greater than 1 for cocksfoot and tall fescue under irrigated conditions but not under rainfed conditions. The response to grazing interval depended on water supply. The 5-week grazing interval led to the highest RCBC under both rainfed and irrigated conditions. However, when rainfed, the 5- and 8-week treatments were not significantly different, whereas under irrigation, the 2- and 5-week treatments did not significantly differ. For the 1995–96 season, a movement index (MI, ratio of newly colonised area to that occupied throughout the season) was measured. There was a strong interaction between species and watering but phalaris was the most mobile (highest MI) of the 4 species under both rainfed and irrigated conditions. The absence of any interaction between species and grazing interval in either 1994–95 or 1995–96 suggests that response to grazing of these species may be similar despite differences in survival mechanisms.

Enhanced Survival and Reproduction of Whitefringed Beetle (Coleoptera: Curculionidae) with Irrigation of Pasture in a Dry Summer Environment

Survival of soil-dwelling larvae of the polyphagous whitefringed beetle, Graphognathus leucoloma (Boheman), increased by ≈2-3-fold in annual pasture irrigated, but otherwise undisturbed, in a summer-dry environment. Rate of larval development was unaffected by the unseasonal moisture. The next generation of larvae appeared in late summer, ≈2 mo earlier than usual. The primary cause was oogenesis induced by unseasonable high-quality food plants resulting from the irrigation; moisture probably enhanced egg survival and induced hatching. Fewer larvae in an irrigated potato crop than in both wet and dry pasture indicated that deleterious effects of cultivation outweighed the survival-enhancing effects of irrigation. However, whitefringed beetle abundance, and hence its pest potential, are likely to be increased by irrigation in infrequently cultivated perennials such as alfalfa.

Pasture management and pasture species for improved dry matter production in south Taranaki

Dry matter (DM) production and seasonal distribution of old ryegrass/white clover pasture defoliated at 14- and 28day intervals, and new sowings of 'Grasslands Maru' phalaris (Phaluris aquatica L.), 'Grasslands Roa' tall fescue (Festuca arundinacea Schreb.), and 'Grasslands Kara' cocksfoot (Dactylis glomerata L.) at 28day defoliation intervals were evaluated in an environment prone to grass grub damage and dry summer/autumn periods. Under a 28&y defoliation interval old ryegrass produced 2O%more DM that the 14-day defoliation interval, the difference occuring mainly in spring. Annual production, in the initial 4 years, of phalaris and tall fescue was respectively 17 % and 20 % more than that of old ryegrass. Phalaris was superior to old ryegrass in all seasons. Cocksfoot annual production was similar to that of old ryegrass, producing more in summer (9%) and autumn (19%) but 15% less in spring. Results from year 5 and 6 suggest that phalaris may not be as persistent as tall fescue. A 28-day rotation in spring is recommended to maximise production of old ryegrasslclover pasture. Phalaris and tall fescue are recommended as alternative species to old ryegrass in a grass grub prone and/or summer dry environment. Cocksfoot is not recommended. Keywords pasture production, seasonal distribution, cow requirements, old ryegrass, phalaris, tall fescue, cocksfoot