Herbage

In the case of animals we are concerned primarily with a two-step process accumulation of airborne contaminants on or in vegetation or forage that serves as their feed and subsequent effects of the ingested herbage on animals. In addition to pollution-affected vegetation, carnivores (humans... 

Cattle feeding on herbage containing 25-50 mg/kg (ppm wt) lead develop excitable jerking of muscles, frothing at the mouth, grinding of teeth, and paralysis of the larynx muscles a "roaring" noise is caused by the paralysis of the muscles in the throat and neck. 

Herbage 10 kg containing 200 mg/kg of fluoride Water 5 kg containing 1 mg/kg of fluoride... 

Herbage, B.S., High Speed Journal and Thrust Bearing Design, Proceedings of the 1st. Turbomachinery Symposium, Texas A M University, October 1972, pp. 56-61. 

Herbage, B., High Efficiency Fluid Film Thrust Bearings for Turbomachinery, 6th Proceedings of the Turbomachinery Symposium, Texas A M University, December 1977, pp. 33-38. 

Armstrong, H. E., Armstrong, F. and Horton, E. 1912. Herbage studies. 1. Lotus comiculatus, a cyanophoiic plant. Proc. Royal Soc. Series B 84 471 84. 

The second important point is that although factors that affect herbage production, such as climate, latitude and aspect, are outside the farmer s control, other factors, such as soil nutrient level and grazing management, can be controlled by the skilful farmer. 

The factors considered above are all factors over which the farmer has no control, but they are important in determining herbage production. The next factors to be considered can be altered by management. 

ADAS lowest level of 0 for potassium is less than 60. As the level of soil nutrients decreases, so herbage production is reduced. What is not so clear at the moment is whether very high levels of phosphorus and potassium increase herbage production. 

Under-grazing on the other hand will result in decreased utilisation of herbage by the animal, due to large amounts of senescent and wasted material. When a sward reaches full canopy, the rate of senescence will equal the rate of new leaf appearance and there will be no further increase in the weight of the standing crop (Fig. 2.2). 

Curll, ci al. (1985) measured an increase in total yield from 6 t dry matter per ha with 10% white clover in the dry matter up to 11 t dry matter per ha with 45% white clover (Fig. 2.4). The increase in total yield was mainly caused by the increase in clover yield the grass yield remained more or less static, with clover levels above 20%. Reports from other experiments show considerable variation in the response. For this reason it can be stated only that white clover increases total herbage yield, but not at very high levels of clover, and that white clover always improves milk yield and liveweight gain compared with grass alone. 

Fig. 2.4 The effect of proportion of white clover on total herbage yield.

Newton, J.E. (1992) Herbage production from organic farms. Research Note 8, Elm Farm Research Centre, Newbury. 

Peel, S.J., Matkin, E.A. Huckle, C.A. (1988) Herbage growth and utilized output from grassland on dairy farms in south-west England Case studies of five farms, 1982 and 1983. Grass and Forage Science, 43, 71-78. 

The organic farmer must be fully satisfied that close grazing does not result in under-nutrition. It need not, but any system based on utilising herbage as fully as possible tends to make the dairy cows eat second or third choice herbage, which may reduce intake slightly and thus milk yield. 

Conventional advice maintains that there is no benefit in adding P to soils that contain available P of index 3 (26-45 mg/kg P in the soil). Beyond this level, there is unlikely to be an increase in herbage yield (Lockhart Wiseman, 1993). However, the experiment cited above (Newton, 1993) showed a straight-line response up to levels of available P of 103 mg/kg (index 6). The equation derived from this work suggested that for every increase of 10 mg/kg available P in the soil,... 

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