Although silicon (Si) has not yet been recognized as an essential nutrient element, its application to sugarcane (Saccharum officinarum L.) has proved to be beneficial. Since optimum crop production depends on the maintenance of adequate plant nutrients in the soil, there is a need in the South African sugar industry for a reliable index for assessing the requirement for supplemental silicon (Si) in soils, particularly in reducing the risk of Eldana saccharina stalk borer infestation in cane. The objective of this study was to assess Si availability in soils, to select a suitable Si extraction method and a critical value for determining when a response is likely. For this purpose, five acid soils (representing. some of the most important agricultural soil groups used for sugarcane production in the sugar belt) were used in October 2004, in the lAKE WILSON glasshouse of the South African Sugarcane Research Institute (SASRI) based at Mount Edgecombe. Except for the Arcadia form soil with an initial Si content of 1.2 mmol kg- I as estimated using the O.OlM H2S04 + (NH4)zS04) extractant, soils representing the other five soil forms namely Cartref, Glenrosa, Longlands and Nomanci; exhibited a sub-optimal Si content of not more than 4.0 mmol kg-I. Sorghum was used as a plant crop and sugarcane as a ratoon crop because of their Si accumulator status. Three different Si sources: calmasil, slagment and wollastonite; with respectively 9.85, 15.20, and 5.25% Si content were applied at increasing rates of 0, 3 and 6 tons ha- 1 as Si fertilizers. Silicon (Si) was extracted from untreated and treated soils by utilizing six different extractants, (1) O.OlM H2S04 + (NH4)2S04; (2) Distilled water; (3) 0.025M H2S04; (4) 0.5M CH3COOH; (5) 0.5M CH3COONH4pH 4.8; and (6) O.OlM CaCh.2H20. The amount of soil Si extracted followed the order: 0.025M H2S04 > 0.5M CH3COOH > O.OlM H2S04 + (NH4)2S04 > O.OlM CaCh.2H20 > 0.5M CH3COON~ pH 4.8 > distilled water. Soil Si extracted by 0.025M H2S04 was significantly correlated with soil exchangeable cations,. CEC, clay content, cane biomass yield, cane Si uptake and increasing rates of applied Si. Averaged over all soil forms investigated, the increases in dry biomass yield and Si uptake ranged. from 18% to 154% for sorghum; and from 23% to 85% for cane respectively. Even though the highest increases (%) in cane biomass yield and Si uptake were obtained on a Nomanci form soil with initial poor fertility status, the highest means were obtained on an Arcadia form soil with the highest Si initial content. There was no difference between different Si sources in their ability to influence cane biomass yield and Si uptake, and therefore the supply to the soils. Even though the lower and higher Si source rates were not different from each other, they increased cane yield and Si uptake, indicating that Si was undoubtedly beneficial for sugarcane. The Si critical levels for different soils as estimated by 0.025M H2S04 were 6.0 mmol kg-1 (168 mg kg-I) for Arcadia; 2.6 mmol kg-I (64 mg kg-I) for Cartrel; 2.5 mmol kg-I (64 mg kg-I) for Glenrosa; 1.6 mmol kg-I (45 mg kg-I) for Longlands; and 2.4 mmol kg-I (67 mg kg-i) for Nomanci form soils. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2007.

The effects of phosphorus fertilization on the growth and survival of Liatris pycnostachya, Physostegia virginiana, and Sporobolus heterolepis seedlings were examined in a prairie restoration project. Treatment included fertilizing once at the time of planting. Plant responses were measured on two soil types, Bono (very high phosphorus levels, lower and flatter) and Morley (very low phosphorus levels, on a slight hill with some slope). P fertilization did not increase the growth of any species on either soil type, although results may have been limited by the effects of surrounding plant competition. Only one significant difference in plant growth was observed between fertilized and unfertilized plots; control Liatris pycnostachya and Physostegia virginiana in the Bono soils produced more shoots than fertilized plants of the same species. P- fertilized Liatris pycnostachya in Morley soil had significantly higher survivorship than unfertilized plants. In contrast, P-fertilized Physostegia virginiana in the Bono soil had the significantly lower survivorship than unfertilized plants. For the other species on either soil type, the survivorship was not significantly different. Because P-fertilization produced very limited benefit, and even adverse plant responses in some cases, the recommendation of this study is that P-fertilization should not be applied at the time of planting of prairie restoration projects. / Department of Biology

[Truncated abstract] There is a well-documented global decline of seagrass meadows in response to anthropogenic pressures. Transplantation of rhizome fragments into denuded areas has been used to enhance natural recovery but nutrient limitation and poor root growth may contribute to low success rates. Addition of nutrients to sediments has been proposed as a means of enhancing growth and survival of seagrass transplants by alleviating nutrient limitation but there is limited information of the effects of nutrient additions to seagrass transplants, particularly root development and morphology. In addition to nutrient limitation, sulphide accumulation in sediments with high organic matter has been shown to reduce seagrass growth and experimental iron additions have been shown to enhance seagrass growth by buffering the development of reduced conditions in organic rich sediments. This thesis examines responses (growth, morphology and nutrient status) of Posidonia australis and Posidonia sinuosa transplants to nitrogen (N), phosphorus (P) and chelated iron (Fe EDTA) additions, and includes a detailed investigation of root growth and morphology in response to these additions. Experiments were carried out in underwater plots in Oyster Harbour, a sheltered estuarine inlet with seasonal river flow, located on the southern coast of Western Australia. In the first experiment, nutrients (N, P and N+P) and Fe EDTA were added to sediment underlying transplants at the end of summer (March 2005). ... Nitrogen (both N and N+P) addition also reduced overall biomass allocation to roots. Nitrogen concentrations increased with N addition in P. sinuosa only but both species had more negative d15N values with N and N+P addition indicating that added N had been taken up. In contrast, P addition had little effect on root growth, and P concentrations only increased in P. australis. However, tissue concentrations of Zn, Co, and Mo in both species increased with P addition. Roots showed limited morphological variation (total root length, mean root diameter, root fineness, specific root length, surface area) in response to nutrient addition. Combined N and P addition increased lateral root density (branches m-1) but had no effect on other morphological parameters of the root compartment. Iron addition had no effect on P. sinuosa but P. australis transplants significantly reduced root growth and productivity, particularly in spring/summer growth period, due to lower primary and lateral growth rates. Overall, N or P additions did not enhance growth although these nutrients were taken up. Iron additions also had little effect on transplant growth. Seagrass transplants had significant root growth although they appeared not to respond to nutrient or iron addition. Both species produced extensive root systems capable of taking up sediment nutrients, which suggests that root development was not a limiting factor in establishment and growth of transplants in the temperate estuary, Oyster Harbour.

Thesis (MSc)--Stellenbosch University, 1964. / ENGLISH ABSTRACT: The influence of manganese sulphate sprays on the yield and ripening of fruit of manganese-deficient Vitis vinifera L. (cv. Pinotage) plants was investigated. Ripening was determined in terms of changes in concentration of the indivi= dual and total sugars and organic acids. Increasing concentrations of manganese sulphate resulted in significant increases in the manganese content of the leaves. The higher levels of manganese were associated with an increase in yield. Ripening, however, was retarded, in that the percentage sugar of the fruit was decreased and titrable acid content increased. The principal sugars present in the fruit were sucrose, glucose, fructose and xylose. Malic and tartaric acids were the main organic acid constituents. Glucose and fructose increased sharply, and sucrose and xylose slightly during ripening of the fruit, whereas malic and tartaric acid de= creased. Glucose, fructose, tartaric and malic acid tended to increase with increasing manganese content. Sucrose and xylose were not appreciably affected. An application of 1% manganese sulphate can be recommend- · ed for manganese deficient vineyards, as it results in an increased yield, in addition to delaying ripening until a more favourable time for handling. Furthermore, the lowered sugar content of the fruit may be advantageous for the pro= duction of dry wines from Pinotage grapes . / AFRIKAANSE OPSOMMING: Die invloed van mangaansulfaatbespuiting op die opbrengs en vrugrypwording van Vitis vinifera L. cv. Pinotage, wat aan ernstige mangaantekorte gely het, is ondersoek. Rypwording is met betrekking tot veranderings in die konsentrasies van totale en indiwiduele suikers en sure bepaal. 2. Toenemende konsentrasies Mnso4 (van O.2% tot l.O%) het n betekenisvolle toename in die mangaangehalte van die blare (van 3 tot 80 d.p.m.) tot gevolg gehad. Die ver= hoogde mangaangehalte het gepaard gegaan met n toe= name in opbrengs, terwyl rypwording vertraag is, deurdat die suikerpersentasie en die titreerbare suurgehalte ver= meerder is in vergelyking met die kontroleplante. 3. Die vernaamste suikers in die vrugte was sukrose, glukose, fruktose en xilose. Glukose en fruktose het vinnig en sukrose en xilose geleidelik toegeneem met die verloop van rypwording. In die ryp vrugte was glukose en fruk= tose oorheersend. Glukose en fruktose was geneig om toe te neem met toenemende mangaangehalte, terwyl sukrose en xilose nie beinvloed is nie. 4. Appelsuur en Wynsteensuur was die oorwegende sure in die vrugte. Beide hierdie sure het gedurende rypwording verminder. Hulle konsentrasies het oor die algemeen toegeneem namate die mangaankonsentrasie verhoog is. 5. Dit is afgelei dat bespuiting met 1.0% MnS04 aanbeveel kan word vir wingerde met mangaantekorte, daar dit n toename in opbrengs, gepaard met 'n vertraging in rypwording tot gevolg gehad het. So 'n vertraging mag moontlik in parstyd voordelig wees. Die verlaagde suikerpersentasie van die vrugte is moontlik gunstig vir die bereiding van droe wyne, waarvoor Pinotage hoofsaaklik gebruik word.

Made available in DSpace on 2014-06-11T19:22:16Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-07-30Bitstream added on 2014-06-13T20:28:26Z : No. of bitstreams: 1 mancuso_mac_me_botfca.pdf: 468949 bytes, checksum: da5909b1b01d8fee70d243a15e351d58 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O Brasil é o maior produtor mundial de café, sendo esse um dos mais importantes produtos agrícolas de exportação, gerando riquezas e divisas ao País. Com isso, a produção de plantas bem nutridas, através da utilização de fertilizantes, tornase cada vez mais importante. O Brasil é um dos maiores importadores mundiais de fertilizantes e o 4o maior consumidor dos mesmos. Só de KCl, em 2009, o Brasil consumiu cerca de 3,2 milhões de toneladas. Isso se deve a fatores como a extensa área cultivada, refletindo na dimensão da produção agrícola brasileira, as características dos seus solos muito pobres quanto aos macronutrientes K e P e a insuficiente produção doméstica de fertilizantes. Para diminuir a dependência nacional do K utilizado na agricultura, a pesquisa vem buscando opções para obtenção desse nutriente com base em minerais contidos em rochas brasileiras, especialmente mediante a moagem de rochas potássicas. Com isso, o presente trabalho teve como objetivo avaliar a eficácia de uma rocha fonolito moída em fornecer K para a cultura do café. Para tanto, o experimento foi desenvolvido em uma propriedade no município de Pirajú-SP, sendo conduzido nos anos agrícolas de 2008/09 e 2009/10. Os tratamentos foram duas fontes de K (KCl e rocha fonolito moída F2) e três doses (75, 150 e 300 kg ha-1 de K2O), correspondente à ½, 1 e 2 vezes a dose de K2O recomendada para a cultura, aplicadas em um cafezal cultivar... / Brazil is the largest coffee producer in the world, which it is one of the most important agricultural export products, generating wealth and currency to this country. Therefore, a well-nourished plants production by fertilizers use becomes more and more important. Brazil is one of the largest importers and the 4th consumer of fertilizers in the world. In 2009, Brazil consumed about 3.2 million tons of KCl only. This is due to factors such as the huge planted area, what it is reflected in the size of Brazilian agricultural production, the characteristics of their soils, which are very poor in relation of the macronutrients K and P, and the insufficient fertilizer domestic production. To reduce the national dependency of K used in agriculture, research has sought options to obtain this element based on Brazilian minerals contained in rocks, especially through the grinding of potassic rocks. Thus, this study aimed to evaluate the effectiveness of a crushed rock to provide potassium to coffee crop. The experiment was carried out in the crop seasons 2008/09 and 2009/10, in a farm placed in Piraju-SP. The experimental treatments consisted in two K sources (KCl and ground phonolite rock F2) and three doses (75, 150 and 300 kg ha-1 of K2O), corresponding to ½, 1 and 2 times the recommended dose of K2O for coffee, applied to the cultivar Mundo Novo plants and these were already productive, besides a control (without K application). The experiment was in a randomized block design, in a factorial scheme (2 x 3 + 1), with four replications. The most important evaluations were leaf contents of N, P, K, Ca, Mg, S and Si, grain contents of the... (Complete abstract click electronic access below)

A greenhouse study was carried out to investigate the effectiveness of soil-applied silicon (Si) with that of foliar applications for sorghum growth. Silicon sources were soil-applied as calmasil (calcium silicate) at two rates (4 and 8t/ha) and foliar applied Si including pure K-silicate, K-humate and K-fulvate (all three foliar treatments at rates of 300 and 600 ppm). Another treatment included soil applied calmasil plus low rate of foliar applied K-humate. The soils used for the greenhouse trial were Cartref, Glenrosa, Nomanci and Fernwood. Results indicated that application of calcium silicate to the soil before planting increased sorghum yield and Si uptake in three of the four soils. Silicon uptake from different experimental treatments followed the order: Calmasil 8t/ha > calmasil 4t/ha ~ calmasil + 300 ppm K-humate> K-humate = K-fulvate = pure-K silicate = control. Foliar sprays were ineffective at increasing yield, Si content of the plant tissues or Si uptake. The concentrations of exchangeable Ca, Mg as well as soil pH were significantly increased by calmasil treatments. Extractable AI concentrations were also reduced due to the Iiming effect of calcium silicate and also possibly formation of insoluble aluminosilicates. The yield response to applied calmasil seemed to be primarily related to its Iiming effect and reductions in extractable AI in the Cartref, Glenrosa and Nomanci soils. The dry matter yield was highest in Fernwood and lowest in Cartref soil. However, there was no significant yield response to calmasil in Fernwood soil which had an initial pH of 5.8 and insignificant extractable AI concentrations. Therefore application of calcium silicate had no significant effect on extractable AI concentration in this soil. Yield response to calmasil may also have been partly due to direct positive effects of applied Si on crop growth through mechanisms such as increased photosynthetic rate and reduced transpiration rate, Addition of calmasil increased the concentrations of Si in the plant tissues and reduced those of N, P and Kin Nomanci and Fernwood soils respectively. This indicates that nutrient interactions were occurring in the plant. It was concluded that foliar-application is not an effective way of applying Si to a Siresponsive crop such as sorghum when growing in soils low in extractable soil Si. This is because Si is accumulated in plant tissues in similar amounts to macronutrients. It was also concluded that in future, studies of crop response to applied Si should include the use of non-Iiming source of Si (e.g. silicic acid) so as to separate a liming effect of calcium silicate from effect of applied Si. In a laboratory study, the effects of applied silicic acid, calcium silicate and calcium hydroxide on levels of extractable P in two Si-deficient soils were investigated. Two soils (Fernwood and Nomanci soils) were treated with two rates of P and three soil amendments (calcium silicate, calcium hydroxide and silicic acid) and incubated for six weeks at room temperature. Phosphorus was extracted using Truog, AMBIC and resin methods, and levels of exchangeable and solution AI and extractable and solution Si were also measured. Application of calcium silicate and calcium hydroxide increased soil pH in both soils while silicic acid additions had no significant effect compared with the control. The pH increase was much greater in the Fernwood than Nomanci soil because of the low buffering capacity of the sandy Fernwood soil. Exchangeable AI and concentrations of monomeric and total AI in soil solution generally followed the order: control ~ silicic acid> calcium silicate> calcium hydroxide. The lowering of soluble AI concentrations in the silicic acid treatments was attributed to formation of insoluble aluminosilicate compounds while that in the calcium silicate and calcium hydroxide treatments was attributed to their Iiming effects causing a rise in pH. Concentrations of Si in soil solution were lower in the calcium hydroxide than the control treatment suggesting the solubility of Si decreased with increased pH. Additions of both Si sources increased Si concentrations in solution and the effect was more marked for the calcium silicate treatment. This was attributed to formation of insoluble aluminosilicates in the silicic acid treatment. Concentrations of H2S04extractable Si with treatment did not closely follow the same trends as those for Si concentrations in soil solution. That is, levels of extractable Si were very much higher in the calcium silicate than silicic acid treatment in both soils. In addition, concentrations of extractable Si in the calcium hydroxide treatment were similar to control in the Nomanci soil, while for the Fernwood soil, concentrations in the calcium hydroxide treatment were exceptionally high. It was suggested that liming with calcium silicate or calcium hydroxide had rendered some Si-containing compounds in the soil acid-extractable and that the nature of acid-extractable Si fraction need further study in future. The quantities of P extracted from the two soils by the various extractants followed the order: Truog> AMBle> resin. The greatest increase in extractable P induced by additions of P was recorded for Truog P and the least for resin P. The effects of Iiming (addition of calcium silicate or calcium hydroxide) on extractable P levels differed depending on the soil and extractant used with increase, decrease or no effect being recorded. Such results confirm the complexity of lime and P interactions which occur in acid soils. Additions of silicic acid had no effect on levels of extractable P, compared to control. It was suggested that the reason for this was that phosphate is adsorbed to AI and Fe oxide surfaces much more strongly than silicate. As a result, additions of Si are ineffective at increasing extractable P levels. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.

The effect of species, parent material, and stand age on nitrogen mineralization were examined during aerobic lab and field incubations. The experimental design consisted of 3 tree species (birch (Betula papyrifera Marsh.); poplar (Populus tremuloides Michx.); and conifers (Abies balsamea (L.) Mill. and Picea glauca (Moench) Voss.)); two parent materials (lacustrine clay and glacial till); and three stand ages (50, 75, and 124 years of age). The strongest determinant of nitrogen mineralization potential was species. The effects of parent material and stand age were variable. Total nitrogen, pH, and soil moisture also affected N mineralization. Nitrogen mineralization dynamics may be largely affected by annual changes in quality of organic matter or climate. Available nitrogen inherent in forest stands must be taken into consideration when replacing hardwood stands with softwoods, because eliminating stages of boreal mixedwood succession could have detrimental effects on available nitrogen and forest productivity in the long-term.

Orientador: Rogério Peres Soratto / Banca: Dirceu Maximino Fernandes / Banca: Enês Furlani Junior / Resumo: O Brasil é o maior produtor mundial de café, sendo esse um dos mais importantes produtos agrícolas de exportação, gerando riquezas e divisas ao País. Com isso, a produção de plantas bem nutridas, através da utilização de fertilizantes, tornase cada vez mais importante. O Brasil é um dos maiores importadores mundiais de fertilizantes e o 4o maior consumidor dos mesmos. Só de KCl, em 2009, o Brasil consumiu cerca de 3,2 milhões de toneladas. Isso se deve a fatores como a extensa área cultivada, refletindo na dimensão da produção agrícola brasileira, as características dos seus solos muito pobres quanto aos macronutrientes K e P e a insuficiente produção doméstica de fertilizantes. Para diminuir a dependência nacional do K utilizado na agricultura, a pesquisa vem buscando opções para obtenção desse nutriente com base em minerais contidos em rochas brasileiras, especialmente mediante a moagem de rochas potássicas. Com isso, o presente trabalho teve como objetivo avaliar a eficácia de uma rocha fonolito moída em fornecer K para a cultura do café. Para tanto, o experimento foi desenvolvido em uma propriedade no município de Pirajú-SP, sendo conduzido nos anos agrícolas de 2008/09 e 2009/10. Os tratamentos foram duas fontes de K (KCl e rocha fonolito moída F2) e três doses (75, 150 e 300 kg ha-1 de K2O), correspondente à ½, 1 e 2 vezes a dose de K2O recomendada para a cultura, aplicadas em um cafezal cultivar... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract : Brazil is the largest coffee producer in the world, which it is one of the most important agricultural export products, generating wealth and currency to this country. Therefore, a well-nourished plants production by fertilizers use becomes more and more important. Brazil is one of the largest importers and the 4th consumer of fertilizers in the world. In 2009, Brazil consumed about 3.2 million tons of KCl only. This is due to factors such as the huge planted area, what it is reflected in the size of Brazilian agricultural production, the characteristics of their soils, which are very poor in relation of the macronutrients K and P, and the insufficient fertilizer domestic production. To reduce the national dependency of K used in agriculture, research has sought options to obtain this element based on Brazilian minerals contained in rocks, especially through the grinding of potassic rocks. Thus, this study aimed to evaluate the effectiveness of a crushed rock to provide potassium to coffee crop. The experiment was carried out in the crop seasons 2008/09 and 2009/10, in a farm placed in Piraju-SP. The experimental treatments consisted in two K sources (KCl and ground phonolite rock F2) and three doses (75, 150 and 300 kg ha-1 of K2O), corresponding to ½, 1 and 2 times the recommended dose of K2O for coffee, applied to the cultivar Mundo Novo plants and these were already productive, besides a control (without K application). The experiment was in a randomized block design, in a factorial scheme (2 x 3 + 1), with four replications. The most important evaluations were leaf contents of N, P, K, Ca, Mg, S and Si, grain contents of the... (Complete abstract click electronic access below) / Mestre

No description available.

Thesis (MScFor)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: Increases in woody plant density ('bush encroachment') reduce livestock production and biodiversity. By convention, soil moisture, soil nutrients, fire and herbivory are regarded as the principal factors governing the tree-grass ratio of savannas. An experiment with a completely-crossed design was employed to investigate woody seedling (Acacia me/lifera) recruitment near Kimberley, Northern Cape, South Africa, after fire and under conditions of maximum-recorded rainfall, nitrogen addition and grazing. The field experiment was repeated as a garden experiment to determine if the two experiments yield comparable results. Tree germination in the field was extremely low, probably due to below-average natural rainfall in plots that only received natural rain, and insufficient watering frequency in irrigated plots. As a result of low germination, none of the treatments (rain/nitrogen/fire/grazing) had a significant effect on tree recruitment in the field experiment. The duration of the experiment (2000/2001 growing season) was insufficient for the treatments to affect grass composition, although the high rainfall treatment and grazing exclusion significantly improved grass cover and height. The garden experiment showed that frequent watering, no nitrogen addition and grass clipping significantly enhanced tree germination and survival (termed 'recruitment'). There were also significant interactions among rain, nitrogen and grazing in their effects on tree recruitment. The effects of rain on tree recruitment were more pronounced under nitrogen supplementation and vice versa. Similarly, high rain and high nitrogen enhanced the effect of grazing on tree recruitment. It is inferred that above-average rainfall years with frequent rainfall events are required for mass tree recruitment. Tree seedlings can further benefit from space and resources which are made available through grass defoliation. Conversely, nitrogen enrichment improves the competitive ability of the fast-growing grasses relatively more than that of the N2-fixing tree component, thereby suppressing tree recruitment. In contrast to conventional wisdom that grazing alone causes encroachment, it is suggested that there are complex interactions between the abovementioned factors and 'triggering' events such as unusually high rainfall. Contrary to many claims that equilibrium models are inappropriate for explaining savanna dynamics, it was shown that consumer-resource theory has explanatory power for bush-grass dynamics of the savanna studied. The state-space approach that was used facilitated the understanding of savanna dynamics and enabled predictions about the system's response to perturbations. The applicability of consumer-resource theory to semi-arid nutrient-poor savannas confirmed the importance of resource competition in structuring natural systems. / AFRIKAANSE OPSOMMING: Toenames in die digtheid van houtagtige plante ('bosverdigting') verlaag veeproduksie en biodiversiteit. Volgens konvensie word grondvog, grondvoedingstowwe, vuur en beweiding beskou as die belangrikste faktore wat die boom-gras verhouding van savannas bepaal. 'n Volledig-gekruisde ("completely crossed") eksperiment is ontwerp om boomsaad-ontkieming (Acacia mellifera) naby Kimberley, Noord-Kaap, Suid- Afrika, te bestudeer na 'n brand en onder toestande van maksimum-aangetekende reënval, stikstof toevoeging en beweiding. Die veldeskperiment is herhaal as 'n tuineksperiment om vas te stel hoe resultate van die twee eksperimente vergelyk. Boomsaad-ontkieming was uiters laag in die veld, waarskynlik weens ondergemiddelde reënval in persele wat slegs natuurlike reënvalontvang het, en 'n te lae benattingsfrekwensie in die besproeide persele. As gevolg van lae ontkieming in die veldeksperiment, het geen behandeling (reënval/stikstof/brand/beweiding) boomsaad-ontkieming beduidend geaffekteer nie. Die duur van die eksperiment (2000/2001-groeiseisoen) was te kort vir die behandelings om grassamestelling te beïnvloed, alhoewel besproeiing en geen beweiding die grasbedekking en -hoogte betekenisvol verhoog het. Die tuineksperiment het getoon dat boomsaadontkieming en vroeë oorlewing (genoem 'vestiging') betekenisvol verhoog is deur gereëlde benatting, geen stikstof toevoeging en die sny van gras. Daar was ook beduidende interaksies tussen reën, stikstof en beweiding in hul invloed op boomvestiging. Die reënbehandeling het 'n groter uitwerking op boomvestiging gehad onder stikstoftoevoeging en vice versa. Hoë reënval en stikstoftoevoeging het ook die invloed van beweiding op boomvestiging versterk. Die afleiding is dat bogemiddelde reënvaljare met gereëlde reënbuie 'n vereiste is vir grootskaalse boomvestiging. Boomsaailinge kan verder voordeel trek uit die spasie en hulpbronne wat beskikbaar raak wanneer gras ontblaar word. Daarteenoor verhoog stikstofverryking die mededingendheid van die vinniggroeiende grasse meer as dié van die N2-bindende boomkomponent, met die gevolg dat boomvestiging onderdruk word. In kontras met die konvensionele veronderstelling dat beweiding opsigself bosverdigting veroorsaak, word voorgestel dat ingewikkelde interaksies plaasvind tussen die bogenoemde faktore en ander 'sneller-gebeurtenisse', soos buitengewoon hoë reënval. In teenstelling met baie aansprake dat ekwilibrium modelle ontoepaslik is om savanna-dinamika te verklaar, is getoon dat die verbruikers-hulpbron teorie ("consumer-resource theory") oor verklaringsvermoë beskik vir boom-gras dinamika van die savanna wat bestudeer is. Die staat-spasie ("state-space") benadering gebruik, het begrip van savanna-dinamika bevorder en voorspellings moontlik gemaak aangaande die sisteem se reaksie op versteurings. Die toepaslikheid van verbruikers-hulpbron teorie vir semi-ariede, nutriënt-arm savannas bevestig dat kompetisie vir hulpbronne 'n sentrale rol speel in die strukturering van ekologiese sisteme.