The patch structure of the grass sward at Kroomie (26°25'38"E 33°48'30"S) in a semi-arid savanna in the Eastern Cape, South Africa, was investigated. The study was conducted on long term grazing trials on five treatments varying in stocking rate (SR; recommended (low) and 1.5 x recommended (high), grazing system (continuous and rotational), and animal type (cattle and sheep). The treatments studied were CR (cattle, rotational stocking, low SR), CC (cattle, continuous stocking, low SR), CH (cattle, rotational stocking, high SR), SC (sheep, continuous stocking, low SR), and SR (sheep, rotational stocking, low SR). Rainfall during the two years of the study (1997/98 and 1998/99) was slightly below the mean average rainfall of the area (66 and 84% of the mean of 519 mm, respectively). Analysis of sward height data using Maximum Likelihood Estimation reflected a bimodal height structure in all treatments. Due to a high overlap of the two distributions in some cases, however, the height at which to separate patches (short grass) from non-patches (tall grass) could not be determined. Canonical Correspondence Analysis (CCA) was used to relate species composition to sward height. It emerged that there are two distinct grass communities at Kroomie, and these are associated with sward height (i.e. patches and non-patches). The interface (in cm) between these two communities, as determined using Two Way Indicator Species Analysis (TWINS PAN) was 6 cm, and this value was subsequently used to discriminate between patches and non-patches. Sward structure was affected by treatments. Animals (cattle and sheep) stocked rotationally at low SR's grazed less than a third of the total area, and this grazing was concentrated primarily in small patches (< 6 m; length is used as a linear indicator of patch size). Animals stocked continuously at low SR's grazed approximately half the area, in small and large (up to 40 m) patches. Animals in the CH treatment grazed approximately two-thirds of the area, in both small and large patches. There was an inverse relation between the size of patches and the size of non-patches, as expected. Nine common grass species were related to sward height. Digiteria eriantha, Eragrostis racemosa, Eustachys paspaloides, and Microchloa caffra were associated with short swards, while Cymbopogon pluronodis, Eragrostis chloromelas, and Sporobolus fimbriatus were associated with tall swards. Themeda triandra (themeda), the most abundant grass at Kroomie, was principally associated with tall swards, but was present at all sward heights. Applying CCA demonstrated a considerable difference between the species composition of patches and of non-patches. There was also a difference in composition between treatments, although these were not as pronounced. Patches reflected a higher species diversity than non-patches. There was a significant (P<0.05) effect of treatment, and of an interaction of treatment by sward structure (i.e. patches and non-patches), on the density of themeda plants. The density of themeda plants was positively correlated with patch size, which suggested that themeda plants that have been grazed may suffer fatal competition from ungrazed neighbours. Anecdotal evidence suggested that patches are stable over the medium term, and that non-patches that are grazed during a drought return to a non-patch structure after rainfall. There was no evidence to support the contention that rotational stocking reduced patch-selective grazing, nor that the species composition of rotationally stocked treatments was better than continuously stocked treatments. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2003.

The majority of the vegetation types occurring on Malilangwe Estate, in the south-eastern lowveld of Zimbabwe, are dominated by Colophospermum mopane (mopane). Over the past 30-50 years the stand density of these mopane vegetation types has increased, and an investigation was undertaken to determine the effect of season of burning and type of fire on mopane woodlands. From this study the following was ascertained: 1) A single predictive equation cannot be used over all seasons to estimate standing crop (fuel load) using the standard disc pasture meter procedure. The calibration equations developed using this procedure accounted for between 39 and 72% of the variation in standing crop, illustrating the high variation in basal cover of the grass sward, as well as the variation between months. Although the revised procedure, developed for areas with low basal cover, accounts for a lot more of the variation in standing crop, this procedure was not used to estimate standing crop over the study period because the calibration equation covered a number of vegetation types, and was not specific to the mopane woodlands. 2) Standing crop tracks effective rainfall (monthly rainfall divided by monthly pan evaporation) closely, with a lag period of less than one month. Standing crop can be estimated using a predictive equation that utilizes effective rainfall from the previous month. There is a positive relationship between peak standing crop and rainfall. A predictive equation was developed to estimate peak standing crop, using annual rainfall. Standing crop declines through the dry season as effective rainfall decreases, and this 'decrease function' allows for the estimation of the standing crop for a particular month, after peak standing crop is reached. 3) Two leaf quantification equations were developed for mopane trees in the south-eastern lowveld of Zimbabwe, one for coppicing and for non-coppicing individuals. These allow for the estimation of leaf dry mass from measured canopy volume. 4) There was no significant difference between the fire intensities attained for the three seasons of burning. Over all seasons, head fires were significantly more intense than back fires. 5) Percentage topkill after late dry season burns was significantly higher than topkill after early dry season burns. There was no significant difference between mid and late dry season burns, and head fires led to significantly more topkill than back fires. Plants < 150 cm experienced significantly more topkill (80 %) than did individuals > 150 cm (44%). 6) Fire per se led to an increase in stand density over all seasons and types of fire, but this change was not significant. Fire did not influence the nett recruitment of new individuals. Height class one (0-50 cm) and three (151-350 cm) were impacted most by fire. This reflects a change in tree structure, with an increase in the amount of leaf material in height class three, and a subsequent decrease in the amount of material in height class one. 7) The effect of season of burning on the change in tree height was significant, whereas the effect of type of fire was not significant. All treatments, except early dry season back fires, led to a reduction in tree height, whereas trees in the no burn areas increased in height. 8) Burning in any season, and implementing either type of fire, led to an increase in the number of stems. Mid dry season burns led to the highest increase in number of stems. However, the more intense the fire the smaller the increase in number of stems. 9) All three seasons of burning (head and back fires) led to a significant decrease in maximum canopy diameter per tree, while the maximum canopy diameter of trees in the no burn areas increased. Mid dry season burns resulted in the greatest decrease in canopy diameter. 10) The effect of burning on the change in leaf dry mass per tree was highly significant. All three seasons of burning led to a decrease in leaf dry mass, while there was no difference between head and back fires. Leaf dry mass in the control areas increased however. High fire intensities led to the greatest decrease in leaf dry mass, late dry season head fires having the greatest decrease. This study suggests that mopane plants face a constraint due to fire and/or browsing, and a tradeoff occurs between canopy volume, canopy diameter, canopy area; and number of stems. Fire leads to an increase in the number of stems through coppicing, while canopy volume and leaf dry mass decreases. This decrease is either (i) a tradeoff in response to increasing stem number, or (ii) a reduction in canopy because additional leaves on the new stems contribute to photosynthesis. The most important response to season of burning is the altered phenophase (phenological stage) of the plant. Early dry season burns cause the trees to be leafless during the early dry season (when unburnt trees are carrying full leaf), and then to be in leaf at the end of the dry season (when unburnt trees are leafless). It would appear that fire disturbance initiates leaf senescence after burning, and then leaf expansion earlier than normal i.e the whole leaf senescence/growth process is brought forward. Trees in late dry season burn areas remain leafless at the start of the rains, while trees in unburnt areas are carrying leaf. Being leafless these trees do not photosynthesize during this time, and it is proposed that the grass sward is advantaged by the reduced competition from the tree component. The consequences of these two changes in phenophase could not be addressed in this study, but are pertinent questions that must be answered if mopane woodland dynamics are to be more fully understood. Management recommendations for (1) the removal of unacceptable moribund grass material, or (2) the reduction of encroachment by woody species on Malilangwe Estate are also given. In an attempt to combat the increase in stand density of mopane it is recommended that high intensity head fires be implemented, when standing crop (fuel load) is sufficient and climatic conditions are conducive to maintaining high intensity fires. These should be carried out at the end of the dry season, before the onset of the rains. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2000.

Food selection by free-ranging black rhinoceros, eland, giraffe and kudu as well as the utilisation of vegetation types by the latter three browsers were investigated over an entire seasonal cycle, from June 1998 to July 1999, at Weenen Nature Reserve, KwaZulu-Natal. The study was aimed at determining the extent of resource overlap within this browser guild. Feeding habits of eland, giraffe and kudu were studied by direct observations, while a plant-based technique was used for black rhinoceros. Dung counts were conducted to monitor selection for vegetation types. Overlap was estimated by measuring the similarities in resource utilisation patterns. Giraffe were exclusively browsers, feeding mostly on woody foliage, over the complete seasonal cycle. The bulk of the annual diet of kudu also consisted of woody browse, although forbs were important and their use increased from early summer to winter. The annual diet of eland consisted of approximately equal proportions of grass and browse, with pods making up almost a third of the diet. Similar to kudu, forbs were more prominent in the winter diet, while grass use decreased. During winter, overlap in forage types generally increased and was considerable because the browsers did not resort to distinct forage 'refuges'. Overlap in the utilisation of woody plant species, however, decreased as animals diversified their diets. Nonetheless, overlap was extensive, primarily owing to the mutual utilisation of Acacia karroo and Acacia nilotica. The quantity of woody foliage decreased during winter, as indicated by phenological differences, but numerous individual plants still carried leaves. Based on current evidence, food quality was assumed to decline. Under prevailing conditions, eland, giraffe and black rhinoceros suffered no mortalities indicating that they were not food limited, possibly owing to the nutritional advantages conferred by their large body size, and that competition among them was unlikely. By comparison, kudu mortalities were great which may signify that they were constrained by food supply and that the larger browsers exerted a pronounced competitive effect on them. Based on the current study it is hypothesised that during periods of resource scarcity the abundance of high quality foods are limited and if interspecific competition does prevail, which will further limit the availability of these resources, it is the smaller bodied herbivores that will be most affected and suffer the greatest mortalities. Consequences of competitive interactions among these browsers have important management implications, especially in small reserves, which are a key stone for the conservation of mammalian herbivores. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2000.

The main aim of this study was to classify and map the threatened coastal grassland communities of the 3 257 ha Umtamvuna Nature Reserve (UNR) in KwaZulu-Natal (30°07'30" to 300 11'05"E; 30°55'00" to 31°04'30"S). Secondary aims were to relate past management and selected environmental variables to community composition and to develop guidelines for monitoring. Alpha diversity was measured using a Whittaker plot and revealed 119 species. A pilot study to test the efficiency of botanical techniques showed that a point based technique (nearest plant method in a 20 X 20 m plot) was efficient (52 minutes for recording 200 points), but recorded only 23% of the species. By increasing the number of points to six hundred, 34% of the species were recorded in 178 minutes; the same time was required to randomly place 30 quadrats (50 X 50 cm), which revealed 80% of the species. Tests for replicate similarity showed a high retrieval of internal association (PS = 86%), using abundant species only and 100 points per plot. The point based technique was thus efficient in detecting abundant species and was acceptable for producing a classification, especially in this case where a comprehensive species list already existed. Indirect gradient analysis (TWINSPAN) identified six grassland communities. An ordination using detrended correspondence analysis (DCA) contributed towards the community classification and grazing and fire frequency gradients were inferred from this ordination. Protea roupelliae communities were common but did not influence grass species composition . Canonical ordination revealed that, of the eight environmental variables measured, 'distance from the sea' strongly affected species distribution (r= 0.83). Cost effectiveness was considered in the development of a monitoring programme. Point based monitoring techniques favoured by sourveld researchers in KwaZulu-Natal were found to be inefficient, particularly for studies requiring the measurement of both species richness and community composition. Randomly located 100 X 100 cm quadrats, located in selected sites which represent previously identified communities, was more efficient. This study contributed towards a refinement of information on the grassland communities of KwaZulu-Natal and supported the use of point data for the classification of grasslands not previously studied. It also demonstrated that point based techniques were not suitable for meeting all grassland monitoring requirements. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1995.

This research was conducted at the University of KwaZulu-Natal, Pietermaritzburg, South Africa. The research encompasses five different studies to assess nutrient cycling in intensive and extensive grazing systems with a view to optimising livestock production. The first study was designed to assess the effect of teff-lucerne mixtures on teff, lucerne and teff-lucerne mixture yields. Lucerne and teff-lucerne mixtures benefited from the association. The overall soil N content of the teff-lucerne mixture plots was greater than the teff alone plots. The second study focused on teff-leucaena association evaluation. It had two leucaena plant row spacings as treatments, 180cm and 120cm, respectively. Teff grown in mixture with leucaena produced a total teff dry matter (DM) of 7931.57 kg ha¯¹ for the 180cm row spacing and 8329.57 for the 120cm row spacing compared to the 3548.93 kg ha¯¹ of DM obtained from the teff alone treatment. The teff-Ieucaena stand also had a greater DM yield response to leucaena row spacing compared to the teff alone. In terms of nutritive quality, all stands from the teff-leucaena plots were better than the quality obtained from the teff alone plots. Total N content of teff from the l80cm row spacing was 21.83 g kg¯¹ and that from the 120cm 16.07 g kg¯¹ compared to the total nitrogen (N) content of 19.77 g kg¯¹ of the teff alone treatment. The total phosphorus (P) content was 2.73, 1.96 and 2.07 g kg¯¹ for the 180cm, 120cm and teff alone treatments respectively. However, the total soil N content was higher for the teff alone plot than for the teff-leucaena plots, which are 1.91, 1.48 and 100 g kg¯¹ for the teff alone, 180cm and 120cm treatments respectively. The third study was designed to assess the effects of different N fertilizer application rates on teff yield response. The rates applied were 0, 50, 100 and 150 kg N ha¯¹. There was significant difference in teff response of the three N fertilizer application rates compared to the control and teff DM yield response was lower for the 150 kg N ha¯¹ (838 kg ha¯¹) treatment compared to the control (553 kg ha¯¹). Both teff DM and nutritive value were higher in the plots treated with N fertilizer than in the plot which received no N fertilizer (control). The soil N content was also higher in those plots treated with N fertilizer. Study four was conducted on the Department of Grassland Science's grassland management techniques trial field at Ukulinga. The effects of nutrient cycling under different management techniques such as burning, mowing and grazing on grass yield response, plant quality and soil nutrients were assessed. However, the response of grass DM yield and P content was not significant but the three treatments had a significant effect on grass N content. Their effect on soil N content was also significant and the grazing plot had the greatest soil N levels. The last study was conducted in the rural areas of Okhombe and Zwelitsha to assess the effects of grazing intensity on grass yield response, plant quality and soil nutrient status at different distances from homesteads. Grass DM yield and nutritive value declined when distance from the homestead increased. The soil N content also was higher nearer to the homestead than further away. Most farmers, particularly in developing countries including those in Eritrea, often experience that their animals prefer forages from some plants such as lucerne, leucaena, and other indigenous leguminous plants. They also observe that they get greater yield from crops grown near leguminous plants or in rotation with legumes. They are also still using manure from their animals to fertilize their croplands. Therefore, it is still the duty of the researchers to demonstrate to farmers on farm studies to convince farmers that it is because leguminous plants have the ability to add quality and quantity to the feed of the animals and soil nutrients to the croplands. Hopefully, this study will convey to farmers the use of growing integrated grassllegume pastures and crops, and illustrate that livestock have their own role in transporting nutrients and hence use them as good means of distributors of soil nutrients. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2004.

No abstract available. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1983.

Patch grazing may be an important factor providing the focus from which wide-scale veld degradation has occurred in the humid grasslands of KwaZulu-Natal. A number of discrete studies were therefore initiated to examine the patch grazing patterns and selected factors which may influence patch grazing at two sites in the humid grasslands of KwaZulu-Natal. The sites were located at Ukulinga Research Farm, situated in the Southern Tall Grassveld, and Kokstad Research Station in the Highland Sourveld. An investigation into the frequency and intensity of gazing patches and non-patches at Ukulinga Research Farm indicated that patch grazing was most evident and most extensive during summer and autumn. As forage in the patches became limiting during winter animals were forced to forage in areas not frequently grazed during the season. The patch grazing pattern was further modified by the time of grazing commencement after a burn in early spring. Early grazing significantly reduced the extent of patch grazing. With early stocking animals were forced to graze less selectively while with increased delay in the commencement of grazing, animals became increasingly patch-selective. Early grazing in conjunction with an autumn rest and heavy grazing during winter could significantly reduce patch grazing. Urine and dung significantly influenced the patch grazing pattern. The sward surrounding a urine deposit was preferentially grazed by both cattle and sheep for a period of at least six months after deposition. Cattle rejected the sward surrounding cattle and sheep dung immediately after deposition and for a period of up to six months. Sheep also rejected cattle and sheep dung patches immediately after deposition. As dung deposits aged, sheep tended to increase their grazing around both cattle and sheep dung pats, and after six months dung did not seem to influence sheep grazing. Urine may be an important factor influencing patch initiation and consequent patch development. A study to examine the characteristics of patches and non-patches in the Highland Sourveld revealed that patches were characterised by lower soil moisture, soil depth and hydraulic conductivity, but by a higher soil nutrient status. Patches and non-patches could also be distinguished in terms of species composition and basal cover. Patches were characterised by Increaser II species, especially Microchloa caffra and, non-patches by Increaser I species such as Trachypogon spicatus, Alioteropsis semialata and Eulalia villosa. Three seasons of patch grazing at Kokstad Research Station negatively influenced the vigour of Themeda triandra in patches relative to the non-patches. The vigour of T. triandra in patches was consistently low throughout a full season's rest. The vigour of T. triandra in non-patches was initially significantly higher than the vigour in the patches and remained so for c. 24 weeks. Vigour measurements at the start of the following season showed that photosynthate accumulation had taken place and a full seasons rest proved to be sufficient in restoring the vigour of T. triandra in patches to the same level as that in non-patches. A full seasons rest did, however, not prevent animals from regrazing the same previously grazed patches the following season. Growth in patches also started c. six weeks later than in nonpatches and above-ground herbage production in patches was significantly lower than nonpatches for at least 20 weeks after a bum. At the end of a full season's rest above-ground herbage production in patches was still slightly lower than that in non-patches possibly due to a difference in species composition between patches and non-patches. Some implications of patch grazing are discussed together with an evaluation of some management recommendations for the humid grasslands with the aim of reducing the potential for patch degradation. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1995.

A remote control sampling technique was developed for the collection of oesophageal fistula samples from goats. Number and size of samples can be varied and collected throughout the day without disturbing the animal's normal feeding behaviour. The equipment developed and tested in this study consists of an oesophageal fistula valve which allows the fistula to be opened and closed, a rechargeable battery pack and motor to operate the valve, a portable radio and receiver to activate the valve motor, and a harness to attach the equipment to the body of the animal In addition, a closing device to effectively seal large oesophageal fistulae (> 1 050 mm²), which in turn is required to accommodate the valve, was developed. During field tests with the fistula valve, 10 % of I 027 sampling attempts failed due to blockage of the valve, and an average of 1.3 incidences of equipment failure were recorded per animal per sampling day, from an average of 9.9 extrusa collections per day. Observed feeding behaviour (grazing/browsing) as well as grass / bush ratio of fistula valve and standard fistula bag samples of four goats, formed the basis for the evaluation of this technique. In addition, extrusa recovery rates, measured under controlled conditions, were used in the evaluation of this sampling method Differences in extrusa composition between the fistula valve and fistula bag techniques varied substantially during the browsing period within a camp and also between camps. Furthermore, during high frequencies of observed grazing, there were large differences between the fistula valve and fistula bag methods. During this study, the fistula valve technique provided a more realistic estimate (R²=.91) of the observed feeding behaviour of goats than the fistula bag technique (R²=.63). Under controlled conditions, the large oesophageal fistula, with or without the valve, enables high and consistent extrusa recovery rates (87 % recovery; SD 7.5). / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1993.

This study was designed to provide the means for implementing formal scientific vegetation management 1n the succulent valley bushveld of the eastern Cape, South Africa. Nowhere in the world has a detailed, effective and practical veld management system being developed entirely from research, and even the most successful management systems rely heavily on the intuition of people. A process, formally called 'adaptive management', combines this intuition with scientific testing and the overall objective of this study was to provide a framework for formalized adaptive management in succulent valley bushveld. On analyzing the process of adaptive management, the following knowledge 'tools' were identified: (i) a management system for immediate implementation; (ii) a technique for vegetation assessment; (iii) a technique for monitoring vegetation change; (iv) a technique for monitoring forage use and recovery; (v) a list of key forage species; (vi) a model to set initial stocking rates; (vii) a method of recording essential information; and (viii) a database of ecological principles. Providing these 'tools' became the goals of this study. These topics covered almost all facets of rangeland science, and the approach was to address these in a 'top down' manner, rather than sub-optimize by specializing on anyone component. Most of the 'tools' were achieved to a greater or lesser extent and are presented as a series of publications. However, a central tool, that for monitoring vegetation change, remains outstanding despite comprehensive testing of a range of traditional botanical methods. Indeed, critical review revealed that this 'missing tool' is a problem which is common in all vegetation communities in South Africa - despite the impression created by vegetation researchers that adequate techniques are indeed available. This is serious because land managers are not able to evaluate the impact of their efforts and the government is unable to monitor the effectiveness of their research and extension services, costing millions of public monies annually. The implication also, is that vegetation cannot be managed scientifically (management implies monitoring). Either formal adaptive management is not practicable, or researchers are operating from an inappropriate paradigm; specifically that of providing techniques for their research projects and claiming that these (or derivatives of these) are adequate for farm or regional scale monitoring. More generally, research has often become an end in it's self, with research quality being judged by criteria which are of little significance to the real world and which damage efficiency. Perhaps, the real value of vegetation research lies in the experiential learning which the researcher gains not the inevitably parochial results. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1993.

The work reported in this thesis was designed to develop a better understanding of the fate of fertiliser nitrogen applied to a tropical pasture under field conditions, with the eventual objective of improving the economy of livestock production off such pastures. This involved an examination of the concentrations of soil total nitrogen, ammonium nitrogen and nitrate nitrogen at different depths within the soil profile following the application of different levels of fertiliser nitrogen to a grazed kikuyu (Pennisetum clandestinum) pasture, as well as the influence of such applications on pasture yield and some elements of pasture quality. The trial was conducted over a two year period at Broadacres in the Natal Mistbelt. A labelled [15]NH[4]N0[3] fertiliser experiment was also conducted to ascertain how the labelled ammonium ion moved through the soil, roots and herbage after being applied in spring onto a kikuyu pasture. In the absence of fertiliser N, a total of 15.45 t/ha of soil N was recorded at an average concentration of 0.15%. More than 30% of the soil total N was, however, situated within the top 10cm of soil. organic matter (OM) content in the top 0-10cm of the profile was high (4.75%), reflecting an accumulation of organic matter in this zone. However, as organic C (and thus c: N ratios) declined with depth, so too did soil total N concentration. Not surprisingly, fertiliser measurably increase soil total N, N applications did not but indirectly may have affected soil N dynamics by increasing net mineralisation (due to its "priming" effect) thereby stimulating plant growth and thus increasing the size of the organic N pool through greater plant decay. Total soil N concentration did not change significantly from the first to the second season. This could be attributed to the fact that N gains and losses on the pastures, being over 15 years old, were probably in equilibrium. Generally similar trends in soil total N down the profile over both seasons was further confirmation of this. Before the application of any fertiliser, 331.9 kg NH[4]-N was measured in the soil to a depth of 1m, on average, over both seasons. This amount represented only 2.1% of the soil total N in the profile. The concentration of NH[4]-N followed a quadratic trend down the soil profile, irrespective of the amount of fertiliser N applied, with the largest concentrations accumulating, on average, in the 0-10cm and 75-100cm depth classes and lowest concentrations in the 50-75cm depth class. Laboratory wetting/drying experiments on soil samples collected from a depth of 75-100cm showed that NH[4]-N concentrations declined only marginally from their original concentrations. A high organic C content of 1.44% at this depth was also probable evidence of nitrification inhibition. Analysis of a similar Inanda soil form under a maize crop did not exhibit the properties eluded to above, suggesting that annual turn-over of the soil was causing mineralisation-immobilisation reactions to proceed normally. Addition of fertiliser N to the pasture significantly increased the amount of NH[4]-N over that of the control camps. Furthermore, the higher the application rate, the greater the increase in NH[4]-N accumulation within the soil profile. As N application rates increased, so the NH[4]-N:N0[3]-N ratio narrowed in the soil complex. This was probably due to NH[4]-N being applied ln excess of plant requirements at the high N application rates. On average, 66.7 kg more NH[4]-N was present in the soil in the first season than in the second after fertilisation. Although this amount did not differ significantly from spring through to autumn, during early spring and late summer/autumn concentrations were higher than in mid-summer. Observed soil NH4-N trends were also very similar to the soil total N trends within both seasons, suggesting that soil total N concentrations might well play an important role in determining soil NH4-N concentrations. Before fertilisation, only 45.6 kg N0[3]-N, representing 0.29% of the soil total N, was on average, found in the profile to a depth of 1m. The highest concentration of N0[3]-N was lodged in the top 10cm of the soil. Nitrate-N declined, on average, with depth down the profile. However, during the second season, even though the concentration of N03-N declined down the profile, it increased with depth during relative to that of the first season, suggesting the movement of N0[3]-N down the profile during this period. Fertilisation significantly increased the concentration of N0[3]-N above that of the control camps. Concentrations increased as fertiliser application rates increased, as did N0[3]-N concentrations with depth. This has important implications regarding potential leaching of N03-N into the groundwater, suggesting that once applications reach levels of 300 kg N/ha/season or more, applications should become smaller and more frequent over the season in order to remove this pollution potential. On average, 94.3 kg N0[3]-N/ha was present down to a depth of 1m over both seasons. However, significantly more N0[3]-N was present in the second season than in the first. This result is in contrast to that of the NH[4]-N, wherein lower concentrations were found in the second season than in the first. No specific trends in N0[3]-N concentration were observed within each season. Rather, N0[3]-N concentrations tended to vary inconsistently at each sampling period. Nitrate N and ammonium N concentrations within each month followed a near mirror image. A DM yield of 12.7 t/ha, averaged over all treatments, was measured over the two seasons. A progressive increase in DM yield was obtained with successive increments of N fertiliser. The response of the kikuyu to the N applied did, however, decline as N applications increased. A higher yield of 1.8 t DM/ha in the first season over that of the second was difficult to explain since rainfall amount and distribution was similar over both seasons. On average, 2.84% protein N was measured in the herbage over both seasons. In general, protein N concentrations increased as N application rates increased. On average, higher concentrations of protein-N were measured within the upper (>5cm) than in the lower <5cm) herbage stratum, irrespective of the amount of N applied. Similar bi-modal trends over time in protein-N concentration were measured for all N treatments and within both herbage strata over both seasons, with concentrations tending to be highest during early summer (Dec), and in early autumn (Feb), and lowest during spring (Oct), mid-summer (Jan) and autumn (March). spring and autumn peaks seemed to correspond with periods of slower growth, whilst low mid-summer concentrations coincided with periods of high DM yields and TNC concentrations. The range of N0[3]-N observed in the DM on the Broadacres trial was 0.12% to 0.43%. As applications of fertiliser N to the pasture increased, N0[3]-N concentrations within the herbage increased in a near-linear fashion. On average, higher concentrations of N0[3]-N, irrespective of the amount of fertiliser N applied, were measured wi thin the upper (>5cm) than the lower <5cm) herbage stratum. A similar bi-modal trend to that measured with protein-N concentrations was observed in both seasons for N0[3]-N in the herbage. High concentrations of N0[3]-N were measured during spring (Nov) and autumn (Feb), and lower concentrations in midsummer (Dec & Jan), very early spring (Oct) and early autumn (March). During summer, declining N0[3]-N concentrations were associated with a corresponding increase in herbage DM yields. A lack of any distinctive trend emerged on these trials in the response of TNC to increased fertilisation with N suggests that, in kikuyu, applied N alone would not materially alter TNC concentrations. Higher concentrations of TNC were determined in the lower <5cm) height stratum, on average, than in the corresponding upper (>5cm) stratum. This may be ascribed to the fact that TNCs tend to be found in higher concentrations where plant protein-N and N0[3]-N concentrations are low. A P concentration of 0.248% before N fertilisation, is such that it should preclude any necessity for P supplementation, at least to beef animals. Herbage P concentrations did, however, drop as N fertiliser application rates were increased on the pasture, but were still high enough to preclude supplementation. Even though no significant difference in P concentration was measured between the two herbage strata, a higher P content prevailed within the lower <5cm) herbage stratum. On average, 2.96% K was present within the herbage material in this trial. The norm for pastures ranges between 0.7 and 4.0%. On these trials, applications of fertiliser N to the camps did not significantly affect K concentrations within the herbage. The lower <5cm) herbage stratum, comprising most of the older herbage fraction, was found to contain the highest K concentration in the pasture. The presence of significantly (although probably biologically non-significantly) less K within the herbage in the second season than in the first may be linked to depletion of reserves of · this element in the soil by the plant and/ or elemental interactions between K and other macro-nutrients. An average Ca content of 0.35% within the herbage falls within the range of 0.14 to 1.5% specified by the NRC (1976) as being adequate for all except high-producing dairy animals. Increasing N application rates to the pasture increased the Ca content within the herbage . No significant differences in Ca concentration were found between the upper (>5cm) and lower <5cm) herbage strata over both seasons, even though the lower stratum had a slightly higher Ca concentration, on average, than the upper stratum. Calcium concentrations did not vary between seasons, probably because concentrations tend rather to vary according to stage of plant maturity, season or soil condition. However, higher concentrations of the element were measured in the second season than in the first. The reason for this is unknown. On average, 0.377% Mg was present within the herbage over both seasons. This compares favourably with published data wherein Mg concentrations varied from 0 . 04 to 0.9% in the DM, with a mean of 0.36%. All camps with N applied to them contained significantly more Mg in their herbage than did the material of the control camps. On these trials, the Ca :Mg ratio is 0.92: 1, which 1S considered to be near the optimum for livestock and thus the potential for tetany to arise is minimal. Magnesium concentrations remained essentially similar within both herbage strata, regardless of the rate of fertiliser N applied. As in the case of Ca, Mg concentrations within the herbage were significantly higher in the second season than in the first. Calcium:phosphate ratios increased, on average in the herbage, as N application rates increased. This ratio was high in spring, dropped off in summer and increased again into autumn, suggesting that the two ions were following the growth pattern of the kikuyu over the season. The K/Mg+Ca ratios were nearly double that of the norm, suggesting that the pasture was experiencing luxury K uptake which may be conducive to tetany in animals grazing the pasture. This ratio narrowed as N application rates were increased, probably as a result of ion dilution as the herbage yields increased in response to these N applications. The ratio was low in spring (October), but increased to a peak in December, before declining again to a low in March. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1994.