Autumn Root Reserves of Lucerne Affected Shoot Yields During the Following Spring

Frequent grazing affects shoot yield of lucerne (Medicago sativa L.) by limiting radiation interception (Teixeira et al., 2005b) and the accumulation of endogenous reserves (C and N) in perennial storage organs like crowns and taproots (Teixeira et al., 2005a). In temperate regions, the impact of low level of perennial reserves is particularly evident during early-spring, when lucerne regrowth resumes after an overwintering period. The analysis of lucerne yield can be fragmented into its yield components of plant population, shoots per plant and yield per shoot (Volenec et al., 1987). The objective of this research was to quantify the impact of limiting levels of perennial reserves, caused by frequent defoliations, on lucerne early-spring yield and determine the sensitivity of yield components to treatments

Caucasian Clover is More Productive Than White Clover in Temperate Pastures

White clover (wc) (Trifolium repens) is present and is often the dominant legume in the \u3e11 m ha of grassland in New Zealand (NZ). However, wc has limitations and normally contributes less than 20% of total annual pasture dry matter (DM) production. The use of a wider range of legume species is one way to increase legume percentage in wc/grass pastures. Caucasian (Cc) or Kura clover (Trifolium ambiguum) is a persistent legume which is slower to establish than wc but can increase total legume production (Cc plus volunteer wc) and hence N2 fixation and animal productivity. This paper compares the productivity of Cc and wc in irrigated and dryland environments, and relates their relative establishment success to differences in seedling development

Net Photosynthesis Rate and Chlorophyll Content of Caucasian and White Clover Leaves Under Different Temperature Regimes

In spring and summer in intensive temperate pastures, Caucasian clover (Cc) (Trifolium ambiguum) has higher dry matter (DM) production rates than white clover (wc) (Trifolium repens) (Black et al., 2003). An examination of the physiological basis for these differences can provide a greater insight into the suitability of Cc for inclusion in temperate pastures. Specifically, leaf photosynthesis rate is a major driver of seasonal growth and is strongly regulated by temperature and chlorophyll content. This study aimed to compare the net photosynthesis rate (Pn) and chlorophyll content of Cc and wc leaves under different temperature regimes

Prediction of Canopy Photosynthesis for Cocksfoot Pastures Grown Under Different Light Regimes

Plants in field environments can experience frequent fluctuations in irradiance from full sun to shade caused by cloud cover, overstory shading (e.g. silvopastoral systems) and within canopy shading. Research with widely spaced radiata pine (Pinus radiata D. Don) has suggested that due to its shade tolerance cocksfoot (Dactylis glomerata L.) is a suitable grass for silvopastoral systems. However, there is limited explanation of the physiological basis for the responses, and consequently no predictive capacity. This limits the application of results to environments, sites and seasons outside of those in which they were measured. The objectives of this study were to simulate net daily canopy photosynthesis rates incorporating the leaf photosynthesis models into a canopy photosynthesis model when only shade was limiting, and to determine the optimum net canopy photosynthesis and LAI for each light regime

Lucerne Crown and Taproot Biomass Affected Early-Spring Canopy Expansion

Leaf area index (LAI) quantifies canopy expansion in crops and is used in lucerne (Medicago sativa L.) simulation models to predict daily PAR interception (PAR i). This then drives yield through radiation use efficiency (RUE) (Gosse et al., 1984). In perennial crops, like lucerne, the level of biomass stored in crown and taproot may affect canopy expansion in subsequent regrowth cycles (Avice et al., 1997). In temperate regions the impact of this is likely to be greatest in early-spring, when low temperatures delay development. The objective of the current research was to identify whether contrasting levels of winter biomass in crown and taproots affected LAI expansion in early-spring regrowth crops

Clover species cover on summer dry hill country in Central Otago

The prevalence of annual clover species and white clover (Trifolium repens) during the critical late winter to early summer period (mid Aug – Dec) are compared in relation to aspect, altitude, temperature and rainfall on Mt Grand at Hawea Flat. Measurements were at four north facing sites (450, 620, 750, 910 m a.s.l.) and one shady site at 630 m a.s.l. The rainfall was similar for all altitudes and aspects but annual clovers dominated on sunny faces and the perennial white clover dominated on the shady face with suckling (T. dubium) the only adventive annual clover present. Annual cluster clover (T. glomeratum) dominated on the lower sunny faces at 450 and 620 m and sub clover (T. subterraneum) dominated at 750 m. Suckling and striated clover (T. striatum) were present on all sunny aspect sites and were unaffected by altitude while haresfoot (T. arvense) presence increased with altitude. Air thermal time accumulation for the mid Aug-Dec period was 1440 °Cd at the 450 m site and declined at 100 °Cd per 100 m of elevation (r² = 0.99). Thermal time at 910 m was <1000 °Cd and may limit seed production of some annual clover species at or above this altitude. The dominance of adventive annual clovers on the sunny aspects indicates areas that are probably suitable for introduction of improved annual species such as balansa clover (T. michelianum) or modern cultivars of sub. Productivity of perennial white clover which has persisted on the shady faces may be increased by more intensive grazing management

Optimizing Yield and Quality of Orchardgrass Pasture in Temperate Silvipastoral Systems

The objective of this study was to provide grazing management recommendations for a silvipastoral system by determining the effects of shade and nitrogen (N) on the pattern of dry matter accumulation and nutritive value of orchardgrass (Dactylis glomerata) in a subhumid temperate environment. Orchardgrass in open pasture (100% transmittance) and under 10 year old Pinus radiata tree shade (60% transmittance) at 200 stems/ha was used as the main plot and nitrogen (0 and 300 kg N/ha as synthetic urine) was the subplot factor. Dry matter (DM) production of orchardgrass in the first 60-day spring rotation was similar in open and shade conditions (2.6 t/ha) but approximately doubled by the application of N. In the 60- day summer rotation, DM production was about 22% lower in the shaded plots and was increased by about 60% by the addition of N. Crude protein and organic matter digestibility declined with herbage age and the onset of reproductive tiller growth. It was concluded that to maximise DM production without compromising pasture quality, grazing management of orchardgrass should be similar in open and shaded pastures in spring (30-35 day regrowth) but a shorter regrowth length used for open (20 days) than silvipastoral (25-30 days) systems in summer

Seasonal Variation of Taproot Biomass and N Content of Lucerne Crops Under Contrasting Grazing Frequencies

Taproot nitrogen reserves (TN, kg N/ha) a function of N concentration within taproots (N%) and taproot biomass (TBM) are a major determinant of lucerne (Medicago sativa L.) growth rates after defoliation and in early-spring (Avice et al., 1997b). Several studies have shown that N% changes with seasons (Cunninghan & Volenec, 1998) and defoliation frequencies (Avice et al., 1997a). However the seasonal pattern of TBM deserves further investigation as the dynamics of root reserves is a weak point in lucerne simulation models (Confalonieri & Bechini, 2004). The objective of this experiment was to assess the seasonal variation in TN through the measurement of TBM and N% of lucerne crops subjected to two defoliations frequencies

Dry Matter Production and Nutritive Value of Alfalfa (\u3ci\u3eMedicago sativa\u3c/i\u3e L.) and Orchardgrass (\u3ci\u3eDactylis glomerata\u3c/i\u3e L.) under Different Light Regimes

Spring and summer alfalfa dry matter and nitrogen production rates were greater than orchardgrass in open pasture and under three shade levels. Ten years old Pinus radiata allowed 60% light transmissivity. The addition of artificial shade resulted in 45% and 25% transmissivity. Orchardgrass pastures were nitrogen deficient and water stressed. In contrast, alfalfa was not stressed and it was more light responsive than orchardgrass. Differences in nutritive value were relatively small between species and between light regimes. Sheep liveweight gain on alfalfa was greater than on orchardgrass. Orchardgrass demonstrated shade tolerance, but alfalfa was more productive even at 25% transmissivity. Conventional concepts of shade tolerance may not be appropriate when screening pasture species for silvipastoral systems