The effect of soil moisture content on leaf extension rate and yield of perennial ryegrass

peer-reviewedThree experiments are described that were designed to evaluate the relationship between soil moisture and perennial ryegrass growth and leaf extension rate (LER) in loam or silt clay loam soil. When soil moisture was maintained at a range of proportions (0.5, 0.75, 1.0, 1.25) of field capacity (FC) in a pot experiment in a glasshouse, 0.75FC had consistently higher growth and LER than 0.5FC and, to a lesser extent, 1.25FC. The quadratic relationship between herbage growth and amount of water applied to maintain target field capacity, was stronger than for that between LER and the amount of water applied, with a maximum response at an application of about 2.5 L/m2 per day. In a microsward (soil depth of 30 cm in boxes 56 cm × 72 cm) trial inducing drought by withholding water for a range of durations resulted in a progressive decline in LER. When soil moisture content fell to about 0.4 of that of the consistently watered control LER was less than 0.1 of the control. However within one week of receiving water, even in the relatively severe drought treatment, LER was not significantly lower than the control treatment. LER was quadratically related to soil moisture content when soil was drying or after rewatering. In a further experiment on the microswards, reducing soil moisture content to about 0.18 g/g by limiting water in May-June resulted in a severe reduction in LER and growth rate and a decline in tillering rate. However, after application of the equivalent of 3 mm precipitation per day in late June, while soil moisture content remained relatively low (about 0.2 to 0.25 g/g soil), LER and herbage growth increased rapidly to as high as in consistently watered microswards. In a treatment in which soil moisture content eventually exceeded FC, LER and herbage growth declined with increase in excess above FC, concurring with findings in the steady state soil moisture experiment. Implications of the data for prediction of production from sown grass swards using temperate maritime grass-growth models are that: (1) during drought, when rainfall resumes, regrowth will be influenced more by amount of rainfallthan soil moisture content and (2) excess soil moisture should be taken into account, including effects of reduced nutrient uptake and post-anoxia stress

Comparison of milk production from clover-based and fertilizer-N-based grassland

peer-reviewedFunding for this study was provided by the Irish National Development Plan and the Irish Dairy Levy.This study, conducted over four years (2003–2006), compared herbage production, nutritive value of herbage, the length of the grazing season and milk production per cow and per hectare from grassland systems based on (i) white clover (average 219 g/kg of herbage DM) (WC) receiving on average N application of 90 kg/ha (s.d. 6.4) in spring and successive 0.2 of the area over-seeded annually with white clover seed and (ii) fertilizer N (FN) input of 226 kg/ha (s.d. 9.7). The stocking density of Holstein- Friesian dairy cows on both systems was 2.0/ha 2003 and 2.2/ha in each of the following three years. There were 22 cows per system in 2003 and 24 cows per system in each of the following three years. Cows calved within a 12 week interval in spring with mean calving date in mid-February. Milk was produced until mid-December each year. Total annual herbage DM production was lower (P 0.05) differences in the in vitro organic matter digestibilities of pre-grazing herbage. The crude protein concentration in pre-grazing herbage DM was higher (P 0.05) differences in annual production of milk per cow (mean 6524 kg; s.e. 83.9 kg), live-weight or body condition score between the two systems. There were no (P < 0.05) differences in the lengths of the grazing season, which averaged 254 days (s.e. 0.9). Although there was no difference in performance per cow, the higher herbage production indicates that a higher stocking rate and milk output per hectare was possible from FN than WC. Nevertheless, the WC swards supported an annual stocking density of 2.15/ha and a milk output of 14 t/ha.National Development PlanIrish Dairy Levy Research Fun

Comparative growth and management of white and red clovers

peer-reviewedThe aim of this paper is to provide the underpinning scientific basis for the optimum management of white and red clovers. Critical morphological and canopy characteristics which influence the yield and persistence of white and red clover in swards, and how management factors (choice of cultivar, defoliation and nitrogen (N) fertilizer) modify these are considered. Canopy development is vitally important as it determines the extent to which a) light is intercepted for photosynthesis needed for growth and b) the base of the sward is deprived of the red component in daylight, inhibiting branching of stolons and crowns in white and red clover, respectively. The role of cultivar, defoliation and N fertilizer in determining yield and persistence of the two legumes, mainly in mixtures with grass, are discussed principally in terms of morphological development and exploitation of light. It is concluded that optimum management for grass/white clover places emphasis on building up stolons and maximising contribution of clover leaf area to the upper layers of the mixed canopy and, while red clover is more competitive to grass than white clover, that benefit is lost when a grass/red clover sward is grazed

Botanical composition, production and nutrient status of an originally Lolium perenne-dominant cut grass sward receiving long-term manure applications

Effects of long-term applications (50, 100 and 200 m(3) ha(-1)y(-1)) of pig and cow slurries on yield, botanical composition and nutrient content of herbage of an original perennial ryegrass sward were assessed in a three-cut silage system and compared with unamended and fertilized controls in the 36th year of the experiment. Cow slurry at 50 m(3) ha(-1) produced similar annual herbage DM yield to 200 kg ha(-1) fertilizer N in 2006, whereas about 100 m(3) ha(-1) pig slurry were required to produce a similar amount of DM. The highest slurry application rate significantly influenced sward botanical composition without depressing DM yield. The principal invading species were creeping bent and meadow grasses (similar to findings at a previous assessment in 1981) except in the unamended control (which were common bent and Yorkshire fog). Perennial ryegrass remained a main species in plots receiving fertilizer (31 % annual DM yield) and low slurry rates (38 %) but declined to 3 % annual DM yield at the highest slurry rate where the ability of ryegrass to utilize slurry N and P may have been affected by chemically or physically induced deficiencies of other nutrients (e.g. Ca) or direct physical effects such as smothering

A short survey of key silage-making practices on Northern Ireland dairy farms, and farmer perceptions of factors influencing silage quality

peer-reviewedNorthern Ireland dairy farmers (n = 174) were surveyed to identify key silage-making practices, and factors perceived to influence the quality of grass silage made on their farms. The majority of farmers (65%) harvested grass for silage three times/year: 62% normally used a contractor, while 47% routinely used a silage additive. Delays to mowing and delays to harvesting due to adverse weather or poor ground conditions were perceived to have a large or very large impact on silage quality (68% and 53% of farmers, respectively). Inadequate wilting, poor-quality swards on owned land, on rented land and “contamination” of first-cut grass with autumn or winter growth herbage were all perceived as having a large or very large impact on silage quality (32%, 27%, 40%, 30% of farmers, respectively). Over the previous decade, 11%, 41% and 37% of farmers claimed a small, moderate or large improvement in silage quality, mainly due to earlier cutting of grass and ensiling better quality swards

Seasonality and Children’s Blood Lead Levels: Developing a Predictive Model Using Climatic Variables and Blood Lead Data from Indianapolis, Indiana, Syracuse, New York, and New Orleans, Louisiana (USA)

On a community basis, urban soil contains a potentially large reservoir of accumulated lead. This study was undertaken to explore the temporal relationship between pediatric blood lead (BPb), weather, soil moisture, and dust in Indianapolis, Indiana; Syracuse, New York; and New Orleans, Louisiana. The Indianapolis, Syracuse, and New Orleans pediatric BPb data were obtained from databases of 15,969, 14,467, and 2,295 screenings, respectively, collected between December 1999 and November 2002, January 1994 and March 1998, and January 1998 and May 2003, respectively. These average monthly child BPb levels were regressed against several independent variables: average monthly soil moisture, particulate matter < 10 μm in diameter (PM(10)), wind speed, and temperature. Of temporal variation in urban children’s BPb, 87% in Indianapolis (R(2) = 0.87, p = 0.0004), 61% in Syracuse (R(2) = 0.61, p = 0.0012), and 59% in New Orleans (R(2) = 0.59, p = 0.0000078) are explained by these variables. A conceptual model of urban Pb poisoning is suggested: When temperature is high and evapotranspiration maximized, soil moisture decreases and soil dust is deposited. Under these combined weather conditions, Pb-enriched PM(10) dust disperses in the urban environment and causes elevated Pb dust loading. Thus, seasonal variation of children’s Pb exposure is probably caused by inhalation and ingestion of Pb brought about by the effect of weather on soils and the resulting fluctuation in Pb loading

The effect of soil moisture content on leaf extension rate and yield of perennial ryegrass

Three experiments are described that were designed to evaluate the relationship between soil moisture and perennial ryegrass growth and leaf extension rate (LER) in loam or silt clay loam soil. When soil moisture was maintained at a range of proportions (0.5, 0.75, 1.0, 1.25) of field capacity (FC) in a pot experiment in a glasshouse, 0.75FC had consistently higher growth and LER than 0.5FC and, to a lesser extent, 1.25FC. The quadratic relationship between herbage growth and amount of water applied to maintain target field capacity, was stronger than for that between LER and the amount of water applied, with a maximum response at an application of about 2.5 L/m2 per day. In a microsward (soil depth of 30 cm in boxes 56 cm × 72 cm) trial inducing drought by withholding water for a range of durations resulted in a progressive decline in LER. When soil moisture content fell to about 0.4 of that of the consistently watered control LER was less than 0.1 of the control. However within one week of receiving water, even in the relatively severe drought treatment, LER was not significantly lower than the control treatment. LER was quadratically related to soil moisture content when soil was drying or after rewatering. In a further experiment on the microswards, reducing soil moisture content to about 0.18 g/g by limiting water in May-June resulted in a severe reduction in LER and growth rate and a decline in tillering rate. However, after application of the equivalent of 3 mm precipitation per day in late June, while soil moisture content remained relatively low (about 0.2 to 0.25 g/g soil), LER and herbage growth increased rapidly to as high as in consistently watered microswards. In a treatment in which soil moisture content eventually exceeded FC, LER and herbage growth declined with increase in excess above FC, concurring with findings in the steady state soil moisture experiment. Implications of the data for prediction of production from sown grass swards using temperate maritime grass-growth models are that: (1) during drought, when rainfall resumes, regrowth will be influenced more by amount of rainfallthan soil moisture content and (2) excess soil moisture should be taken into account, including effects of reduced nutrient uptake and post-anoxia stress