This study examined productivity, nitrogen (N) flows and N balances in grassland-based systems of dairy production in Ireland. There were four stocking densities of dairy cows on grass ⁄ white clover pastures and four inputs of N as fertilizers, concentrates and biological fixation over 2 years; 2001 and 2002. Annual stocking densities were 1AE75, 2AE10, 2AE50 and 2AE50 cows ha )1 . Associated N inputs were 205, 230, 300 and 400 kg ha )1 respectively. There were eighteen cows per system. Cows calved within a 12-week interval in spring with a mean calving date of 28 February and lactation extended until mid-December in each year. There were no differences in annual milk yield (6337 kg cow )1 ; s.e.m. 106AE1), live weight or body condition score. Pre-grazing N concentrations in herbage increased (P < 0AE001) with increasing N input, whereas there were no differences in N concentrations in silage reflecting optimum N inputs for silage production. Grazed herbage accounted for 0AE64, silage 0AE26 and concentrates 0AE10 of annual dry matter consumed by the cows. Annual intakes of N ranged from 144 to 158 kg cow )1 and were mostly influenced by N concentration in grazed herbage. Annual output of N in milk and liveweight change was 38 kg cow )1 and was not different between systems. Annual N surpluses increased with increasing N inputs from 137 to 307 kg ha )1 , whereas the proportion of N inputs recovered in products declined from 0AE34 to 0AE24. More efficient N use was associated with lower N inputs and in particular lower N concentrations in grazed herbage.
-The system of milk production in Ireland is dependent on the efficient utilisation of grazed grass. Therefore the use of grass cultivars with different heading dates may have a large effect on dairy cow performance. The objective of this study was to determine the effect of grass cultivars differing in heading date and grass ploidy on milk production and grass dry matter intake (GDMI) of spring calving dairy cows. The study took place over two years. Seventy-two spring calving dairy cows in Year 1 and 80 in Year 2 were blocked into groups of four and were assigned randomly to one of four grass cultivar treatments. The grass cultivars differed in heading date (intermediate or late) and grass ploidy (diploid or tetraploid). The grazing season began in April 12 (Year 1) and April 25 (Year 2) and lasted until the end of September in both years. A total concentrate DM input of 248 kg and 45 kg·cow -1 was offered to the herds in Year 1 and in Year 2, respectively. All concentrate was offered during the first 3 grazing rotations. Rotation had a significant effect (P < 0.001) on all milk production parameters in both years. In Year 1, late heading cultivars significantly (P < 0.05) increased milk yield, solids corrected milk yield (SCM), fat, protein and lactose yield. There was a significant interaction (P < 0.05) between heading date and grass ploidy for lactose yield and fat concentration. In Year 2, late heading cultivars had also increased milk yield (P < 0.01), lactose yield (P < 0.05), SCM (P < 0.05), protein yield (P < 0.001) and protein concentration (P < 0.05). In Year 1, the GDMI was higher (P < 0.001) for cows grazing the late heading cultivars. It is concluded that later heading grass cultivars have a beneficial effect on the milk production performance of spring calving dairy cows.dairy cows / grazing / grass cultivars / intake / milk production 321 Anim. Res. 52 (2003) Résumé -Influence de la date d'épiaison et de la ploïdie de variétés de ray-grass anglais sur les performances et l'ingestion d'herbe chez les vaches laitières au pâturage. En Irlande, les systè-mes de production laitière reposent surtout sur l'utilisation efficiente du pâturage. Dans ces conditions, la date d'épiaison des variétés de ray-grass peut avoir des conséquences sur les performances du troupeau au pâturage. L'objectif de cette étude est de déterminer l'effet de 4 variétés de ray-grass anglais, différant par leur date d'épiaison et leur ploïdie, sur la production laitière et l'ingestion d'herbe chez les vaches laitières au pâturage. Cette étude s'est déroulée durant deux saisons complètes de pâ-turage. Soixante-douze vaches en année 1 et 80 vaches en année 2, vêlant au printemps, ont été mises en lot et affectées à l'un des 4 traitements expérimentaux. Les variétés de ray-grass ont différé par leur date d'épiaison (intermédiaire ou tardif) et leur ploïdie (diploïde ou tétraploïde). La saison de pâtu-rage a commencé le 12 avril (année 1) et le 25 avril (année 2) et s'est s'achevée fin septembre. L'apport total de concent...
This study compared the profitabilities of systems of dairy production based on N‐fertilized grass (FN) and grass‐white clover (WC) grassland and assessed sensitivity to changing fertilizer N and milk prices. Data were sourced from three system‐scale studies conducted in Ireland between 2001 and 2009. Ten FN stocked between 2·0 and 2·5 livestock units (LU) ha−1 with fertilizer N input between 173 and 353 kg ha−1 were compared with eight WC stocked between 1·75 and 2·2 LU ha−1 with fertilizer N input between 79 and 105 kg ha−1. Sensitivity was confined to nine combinations of high, intermediate and low fertilizer N and milk prices. Stocking density, milk and total sales from WC were approximately 0·90 of FN. In scenarios with high fertilizer N price combined with intermediate or low milk prices, WC was more (P < 0·05) profitable than FN. Based on milk and fertilizer N prices at the time, FN was clearly more profitable than WC between 1990 and 2005. However, with the steady increase in fertilizer N prices relative to milk price, the difference between FN and WC was less clear cut between 2006 and 2010. Projecting into the future and assuming similar trends in fertilizer N and milk prices to the last decade, this analysis indicates that WC will become an increasingly more profitable alternative to FN for pasture‐based dairy production.
Position in and contribution of leaf laminae to the canopy of forage grasses are important both in determining herbage growth rates and intake rate by grazing animals. These canopy characteristics are controlled by the way dry matter is apportioned between sheath and lamina in growing leaves. The objective of this work was to determine how the development of individual leaves is affected by altering the effective length of the psuedostem tube, on the assumption that the light environment within the tube varied. The development of a leaf from initiation at the apex to maturity was followed by successive destructive dissections of tillers. Vertical incisions were made in the pseudostem of each tiller to three different depths. The three treatments imposed wereno incision (control), moderate and severe incision of the sheath length. Destructive harvests of tillers followed 3, 6, 12 and 24 days after imposition of treatments. Incision resulted in the length of the monitored leaf being reduced significantly at all harvests, and differentiation of the sheath beginning earlier. The length reduction reflected a reduction in both cell size and cell number and the effects were evident at the earliest harvest. The data support the theory that leaf size and timing of onset of sheath development are influenced by the environment of the developing leaf. The present results indicate that sheath tube length affects leaf development and suggests that the effects are substantially explained by a direct light effect on the location and depth of the elongation zone.
White clover can reduce fertilizer‐N requirements, improve sward nutritive value and increase environmental sustainability of grazed grasslands. Results of previous experiments in glasshouse conditions and on mown plots have suggested that white clover may be more susceptible than perennial ryegrass to treading damage on wet soils. However, this phenomenon has not been investigated under actual grazing conditions. This experiment examined the effects of treading on clover content, herbage production and soil properties within three clover‐based grazing systems on a wet soil in Ireland for 1 year. Treading resulted in soil compaction, as evidenced by increased soil bulk density (P < 0·001) and reductions in the proportion of large (air‐filled) soil pores (P < 0·001). Treading reduced annual herbage production of both grass and white clover by similar amounts 0·59 and 0·45 t ha−1 respectively (P < 0·001). Treading reduced the sward clover content in June (P < 0·01) but had no effect on annual clover content, clover stolon mass or clover content at the end of the experiment. Therefore, there was little evidence that white clover is more susceptible to treading damage than perennial ryegrass under grazing conditions on wet soils.
This study investigated changes in soil organic carbon (SOC) in a poorly drained clay loam soil under (i) permanent grassland (PG) over 7 years and (ii) after PG renovation over 2·5 years. The experimental area was divided into four blocks with four paddocks per block. Composite soil samples from each PG block were taken to 30‐cm depth on five occasions between 2004 and 2011. In June 2008, one paddock per block was renovated by ploughing and reseeding and sampled as above on the latter four occasions. Renovation decreased SOC (P < 0·05) by 32·2 t ha−1 in the 2·5 years following ploughing; the difference developed almost entirely (86%) in the first four months. Renovation had no effect on above‐ground productivity, standing root and stubble phytomass or on dissolved organic matter leaching. Therefore, soil respiration was considered to be a single potential pathway responsible for the SOC loss from renovated grassland. Although a simple linear regression indicated a tendency for PG to accumulate SOC, there was no evidence of recovery in SOC to previous levels following renovation during the study period. These results could have implications for greenhouse gas inventories in countries where PG is an important land‐use type.
SUMMARYGiven the finite nature of global phosphorus (P) resources, there is an increasing concern about balancing agronomic and environmental impacts from P usage on dairy farms. Data from a 3-year (2009–2011) survey were used to assess farm-gate P balances and P use efficiency (PUE) on 21 intensive grass-based dairy farms operating under the good agricultural practice (GAP) regulations in Ireland. Mean stocking rate (SR) was 2·06 livestock units (LU)/ha, mean P surplus was 5·09 kg/ha, or 0·004 kg P/kg milk solids (MS), and mean PUE was 0·70. Phosphorus imports were dominated by inorganic fertilizer (7·61 kg P/ha) and feeds (7·62 kg P/ha), while exports were dominated by milk (6·66 kg P/ha) and livestock (5·10 kg P/ha). Comparison to similar studies carried out before the introduction of the GAP regulations in 2006 indicated that P surplus, both per ha and per kg MS, has significantly decreased (by 74 and 81%, respectively) and PUE increased (by 48%), mostly due to decreased inorganic fertilizer P import and improvements in P management. There has been a notable shift towards spring application of organic manures, indicating improved awareness of the fertilizer value of organic manures and good compliance with the GAP regulations regarding fertilizer application timing. These results suggested a positive impact of the GAP regulations on dairy farm P surplus and PUE, indicating an improvement in both environmental and economic sustainability of dairy production through improved resource use efficiencies. Such improvements will be necessary to achieve national targets of improved water quality and increased dairy production. Results suggest that optimizing fertilizer and feed P imports combined with improved on-farm P recycling are the most effective way to increase PUE. Equally, continued monitoring of soil test P (STP) and P management will be necessary to ensure that adequate soil P fertility is maintained. Mean P surplus was lower and PUE was much higher than the overall mean surplus (15·92 kg P/ha) and PUE (0·47) from three studies of continental and English dairy farms, largely due to the low import system that is more typical in Ireland, with seasonal milk production (compact spring calving), low use of imported feeds and high use of grazed grass.
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