The influence of soil, tillage and other factors on the uptake of nitrogen by barley

Field experiments were conducted, using ¹⁵N- labelled nitrogen fertilizer, to measure the absolute and relative uptakes of nitrogen by barley from (a) the fertilizer and (b) other sources. Results from 2 years of parallel experiments on several sites are presented, together with previous years' data from one site.The response of unlabelled N uptake to increasing levels of labelled N application seen at Bush was observed occasionally at the other, higher yielding, sites. It was observed more frequently at a site at Balerno (Midlothian), on soil derived from carboniferous till (as at Bush) than at Aberlady, East Lothian, on a raised beach soil. Uptake of unlabelled N generally increased towards the end of the growing season, while uptake of labelled N remained constant or fell.. This phenomenon was observed at all sites. Of the various mechanisms possible for the interaction of nitrogen fertilizer with other sources of N, it was concluded that the most likely explanation of the results was a stimulation of crop root growth by the fertilizer, promoting greater exploitation of available N. Significantly higher quantities of N from both sources were taken up by winter barley than by spring barley.In soil under autumn -sown barley, there was less available N in spring than in similar soil newly sown with spring barley. This highlighted the risk of leaching of available N in the soil before it could be taken up by the spring-sown crop. Laboratory measurements of N mineralization indicated a zero-order relationship with time in topsoil. There was also rough agreement with A-values calculated from crop uptake.Interaction between the 2 sources of nitrogen was observed on imperfectly-drained soil at the Bush Estate, Midlothian. There was a general, positive response of unlabelled N uptake to increasing levels of applied, labelled N. There was no evidence of differences in readily-mineralizable N in topsoil due to differential rates of N application over several years. In general, crop yields were greater on the ploughed than on the direct- drilled plots. The exception was in 1979, when the spring was wetter and the summer was drier than in the other years

Use of selected fodder shrubs in the reclamation of degraded arid rangelands

Aspects, which influence the choice of species for the rehabilitation of degraded arid areas, were studied. Although only one trial was established in the target area (transition area between the Succulent and Nama Karoo) seed of the indigenous species used was collected from this area. In the initial trials the effect of rumen digestion on the germination of fodder shrubs was observed. Species included the exotic Atriplex nummularia and Cassia sturtii, and the indigenous Sutherlandia microphylla, Tetragonia calycina, Tripteris sinuatum and Salsola glabrescens. No seed of T. calycina germinated. In T. sinuatum and S. glabrescens rumen digestion prevented germination while in the other species percentage germination was reduced. In the establishment trial with A. nummularia and C. sturtti, on a bare area onfarm, in the arid Northern Cape Province, no seed germinated. Observations showed that, for both species, protection is essential, where the risk of herbivory is high. Of the two species, C. sturtti shrubs appeared to be more drought tolerant. A further trial addressed the intra-species variation in the palatability of A. nummularia. Established shrubs of the F1 “elite” generation were browsed by sheep. The most palatable shrubs were identified and seed from these shrubs will be used to produce seedlings that will go into further selection trials. The final section of this study was a comparison, in terms of quantity, quality and re-growth, of C. sturtii, T. sinuatum and S. microphylla, at, and subsequent to, five different harvest dates. In the first three harvests no significant differences were observed in the total plant material produced, between the three species. In Harvest 5 both indigenous species had produced more edible material (leaf and <3mm stem material) than C. sturtii. The edible material of Harvests 1, 3 and 5, was analysed for crude protein content, in vitro digestibility and mineral concentrations. All three species had sufficient crude protein as well as calcium, phosphorus and magnesium, to meet maintenance requirements of sheep. Trace minerals, manganese and copper, were present in adequate amounts and toxicity could be more of a concern. The concentrations of zinc in all three species, however, were only sufficient in material obtained in Harvests 1 and 3. Re-growth of all shrubs 21 weeks after Harvest 5 was assessed in terms of survival, healthiness, leafiness, volume and dry matter production. C. sturtii shrubs harvested at a later stage in the initial trial had the best survival. For most re-growth periods, C. sturtii shrubs also appeared healthier and leafier than the indigenous species. S. microphylla seedlings had, however, established in the S. microphylla plots, which was a plus for that species. CopyrightDissertation (MScAgric)--University of Pretoria, 2010.Plant Production and Soil Scienceunrestricte

Factors influencing the energy requirements of native ponies living outdoors in the United Kingdom

The purpose of this study was to determine the daily energy requirements of ponies native to the U.K., living on upland areas. This information can be used to improve the management of ponies kept under these conditions.The objectives of this thesis were to i) determine the effects of speed and terrain on the energy costs of ponies when walking, ii) measure seasonal differences in the hair coat, iii) estimate the effect of a wet winter coat on metabolic rate, iv) determine the proportion of a day spent by free-living ponies in feeding, walking, standing and lying, v) estimate the total distance moved daily by these ponies, and vi) describe the relationship between weather conditions and the behaviour and location of ponies.In the first study, the energy costs of walking were measured in four Shetland and two Exmoor ponies by using open-circuit, indirect calorimetry. The energy cost of activity, above that for standing, was independent of speed and averaged 1.02 J/kg liveweight/m travelled. An Oxylog, a portable breath-by-breath oxygen analyser, was used to determine effects of terrrain on the energy cost of walking using five Shetland ponies. The mean (s.e.) energy expenditures (J/kg/m) were:- grass 1.7 (0.07); concrete 2.9 (0.15); 12 cm of mud 5.9 (0.21); uphill (+5.8°) 5.5 (0.31); downhill (-5.8°) 3.3 (0.23) J/kg/m.In the second study, physical parameters of the winter and summer hair coats of six Shetland ponies were compared. Also, metabolic rate was monitored as a means of assessing the effect of wetting ponies in winter coat. Coat density in the winter 2 • 2 averaged 96.2 (s.e. 8.01) mg/cm , 3.24 times the summer value of 29.5 (3.37) mg/cm . Fibre diameter differed significantly between ponies within season. For some ponies there were seasonal changes in fibre diameter. The number of fibres/cm" did not differ significantly between seasons. Metabolic rate (determined by open-circuit, indirect calorimetry) and body temperature were unaffected by wetting (to the skin) the dorsal surface of Shetland ponies in winter coat. However, there were decreases in skin temperature over the wetted area which suggested local vasoconstrictionIn the third study, six Exmoor pony mares, kept in an enclosed area of fell in Cumbria, were observed in late winter (W) when they were pregnant, and in summer (S) when they were lactating. There were significant seasonal differences in the time spent feeding 17.2 h (W), 13.5 h (S); walking 0.5 h (W), 1.2 h (S); and standing 4.6 h (W), 6.2 h (S); but not in lying 1.3 h (W & S). The total distance moved by the mares in 24 h; 3.1 - 5.7 km (W) and 3.7 - 4.9 km (S), was calculated as the sum of the distances moved whilst grazing and walking. In winter, ponies preferentially grazed facing directly into or away from the wind at all wind speeds, and preferred to stand in areas where wind viii speed was reduced. In the summer, the same orientations to the wind became evident at wind speeds of 5 m/s. Ponies stood in the most exposed areas during the hottest parts of the day, but stood in sheltered areas at night. Grazing speed and bite rate were significantly greater (P<0.05) in the winter than in the summerThe results showed that the energy costs of activity (walking and grazing) were greater in winter than in summer. Therefore, seasonal adjustments in energy requirements are needed to allow for changes in activity as well as changes in heat loss. Recommendations are made regarding the management strategies for ponies kept outdoors

An investigation of soil water movement on drained and undrained clay grassland in South West England

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