Pathways of water loss from legumes and grasses cut for conservation

Abstract

IntroductionThe slow loss of water from crops cut for high dry-matter silage, pre-wilting before grass drying and particularly from crops cut for hay, causes loss of dry matter and reduction in nutritive value. The total loss of dry matter can be very large and Klinner (1976) states that as much as 30% of the dry matter in the original crop can be lost during hay-making. In addition to the purely mechanical losses caused by fragmentation, dry matter can be lost as a result of continued respiration after a crop has been cut and Greenhill (1959) found that 7% ofthe original dry matter in ryegrass and white clover could be lost in this way. Woods (1972) calculated from the data of Pizarro and James (1972) that 7% of the dry matter in peretinial ryegrass could be lost in a 9-day drying period as a result of continued respiration. Rain falling on to a cut crop will increase losses by leaching out soluble nutrients and the losses are greater if the crop has been mechanically damaged to increase drying rate. Thus Kormos and Chestnutt (1968) found that laceration increased leaching losses. Demedde and Wilmschen (1969) subjected grass of low water content to simulated rainfall and found that the serious losses of dry matter which occurred were greater if the grass had been previously crushed.Mechanical conditioning treatments such as crushing, crimping and flailing have been used for many years to accelerate the field drying of forage crops. Reviews by Bruhn (1959) and Klinner (1975) indicate that greater severity of treatment produced bigger increases in drying rate but also resulted in greater losses of dry matter. While mechanical treatments open new pathways of water loss by physical rupture of tissues, chemical conditioning treatments could facilitate water loss from the existing pathways by reducing stomatal and cuticular resistance. Such treatment may avoid the losses associated with mechanical conditioning.The pathways of water loss have been the subject of considerable research effort in the case of the growing plant, but the literature on the function of these pathways in the cut plant is much less extensive. The reduction in the water content of the growing plant during 1 day resulting from the excess of transpiration over water uptake is very small compared to the reductions which are necessary to produce hay which can be safely stored. Thus Willard (1931), showed that, with lucerne, soya beans, red clover, sweet clover and alsike clover, the decrease of water concentration during the day is never more than 3%. With grasses, Greenhill (1936) observed a similar fall in water concentration between 09.30 and 15.00 hours. It is therefore unlikely that data on the loss of water from the growing plant will be relevant to the process of drying in the cut plant, except in the very early stages. A further area of interest in the drying plant is the extent to which stem water continues to be transferred to and lost from the leaves after cutting.The object of this paper is to review existing literature on these topics...

Some changes associated with the field drying of lucerne and timothy

“…that of non-leaf material; similar results have been reported by Pederson and Buchele (1960) and by Jones and Prickett (1981). Harris and Tullberg (1980) also suggested that the faster rate of drying of the leaves, compared with that of stems, results in a situation where the leaves are dried to a point where they are very susceptible to shattering. The more rapid rate of loss of moisture from leaf material, compared with that of non-leaf material, is not surprising, in view ofthe fact that the leaf is the principal site of moisture loss from the plant by transpiration (Watson and Nash, 1960).…”

Production of alfalfa hay under different drying methods

“…Twenty-seven hours after cutting, the drying in the field up to 50% DM and dried under the shade began to reduce the DM value because the material did not have any solar radiation, which, according to Harris & Tullberg (1980), has been identified as the main environmental factor that influences the drying of grass and leguminous.…”

Effect of silage additives and wilting on silage fermentation, digestibility and intake, and on liveweight change of young cattle

“…A more probable explanation is the rain which delayed harvesting. In these conditions losses of highly digestible nutrients through oxidation and leaching will be high (McDonald, 1981) particularly if the crop has been conditioned to increase drying rate (Harris and Tullberg, 1980). Alternatively Waldo (1978) has suggested that organic matter digestibility figures may be biased because of possible analytical errors due to losses of volatiles on drying highly fermented, i.e.…”