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Thesis (MScAgric (Soil Science))--Stellenbosch University, 2005. / Soil acidity is one of the greatest limitations to crop production in most soils of the world. The increasing high costs of conventional liming materials have made it necessary to explore the possibilities of using cheaper substitutes. In South Africa, 16 million hectares of land are naturally acid while on the other hand, the country’s coalfired power plants generate 28 million tons of mostly alkaline coal ash per year, disposal of which is increasingly becoming difficult. The use of coal ash as an agricultural soil amendment while solving the liming needs of local farmers, may also present a safe and more economical disposal option. This study was carried out to evaluate the effectiveness of coal ash as an agricultural liming material. A greenhouse experiment was conducted using maize as test crop. A field experiment was also established on Beestepan Farm in Middelburg, Mpumalanga Province using dry beans as test crop for the first season. In both experiments, fresh unweathered coal ash from Duvha power station (CCE 10%), dolomitic lime (CCE 77%) and calmasil (calcium silicate slag, CCE 99%) were applied to acidic sandy loam soils in the presence or absence of gypsum. Both calmasil and dolomitic lime were applied at equivalent rates of 0, 1, 2, and 4 tons/ha, and rates of 0, 7, 14 and 28 tons/ha were used for ash. Gypsum was applied at a rate of 4 tons/ha. All treatments were applied in three replications. Results showed that liming increased soil pH, improved soil nutrient status and plant uptake of base cations, and enhanced yield. In the greenhouse, coal ash decreased exchangeable acidity from 13.0 mmolc/kg to 6.67 mmolc/kg, increased Ca levels from 200 mg/kg to 379 mg/kg, and increased Mg levels from 25.9 mg/kg to 42.0 mg/kg. Nitrate levels were also raised from 4.4 mg/kg to 14.8 mg/kg hypothetically as a result of the increase in the activity of nitrifying bacteria following a decrease in soil acidity after ash application. Maize yield in the greenhouse was not significantly affected by ash or by other liming materials, and the sufficient watering and consequent elimination of aluminium-induced drought stress is put forward as having masked crop responses to acidity. In the field, coal ash reduced exchangeable acidity from 10.0 mmolc/kg to 5.88 mmolc/kg, increased Ca levels from 71 mg/kg to 132 mg/kg, and increased Mg levels from 7.3 mg/kg to 17 mg/kg. The increase in bean yield from 958 kg/ha to 1724 kg/ha by ash was similar to that realized by dolomitic lime and calmasil. Gypsum had little effect on soil acidity, but it substantially improved soil Ca and sulfate levels, and enhanced bean yield in the field experiment. The study demonstrated that coal ash could be effective as a liming material, and underscores the need for a cost-benefit assessment of ash use necessitated by the relatively higher rates of ash required to obtain significant soil and plant responses.

Thesis (MScAgric (Soil Science))--Stellenbosch University, 2008. / The soils of north-west Zambia are largely unexplored and are regarded by local residents as problematic in providing sufficient nutrients for the staple crop of maize in the area. The area is semi-tropical, with an average rainfall of 1300mm annum-1 falling predominantly in the summer. The undulating landscape is dominated by miombo woodland interspersed with savanna grassland. Little work has been done on these soils and further information is required to understand their origin and their fertility status. The main objectives of this thesis were: 1) to classify and sample soils from a large number of small-scale agricultural lands, 2) to develop a better understanding of these soils chemical characteristics, 3) to determine the effect of vegetation clearance on soil fertility by sampling adjacent uncultivated land, and 4) to test locally derived rock dust as a soil ameliorant in pot trial. Soils from 100 agricultural and adjacent bush/forest sites were classified and analysed to determine their fertility status. They were tentatively classified according to the WRB system and are dominated by Arenosols, Acrisols and Ferralsols with infrequent occurrences of Lixisols. Most of these soils have a sandy texture. The clay fraction comprises of gibbsite, kaolinite and hydroxyl-Al interlayered vermiculite (HIV), with a few soils also having some mica present. The soils are consistently acidic with 42% of soils sampled having a pH (KCl) <4.3. Furthermore, the subsoils proved to be equally if not more acidic than the topsoils. Low nutrient levels are invariably associated with the soil acidity, with 84% of soils having <15mg/kg P, 59% of soils <50 mg/kg K, 80% soils <300 mg/kg Ca, and 44% soils <80 mg/kg Mg. Comparisons between cultivated and bushland soils showed no consistent changes to the soil acidity and fertility. This is contrary to research that was reviewed but is likely to have been affected by the spatial variability of these soils arising from the termite dominated landscape and the soils having been derived from different parent materials. Amelioration of these soils is required in order to increase yields. It is thought that lime, used with an N, P, K, Zn and B fertilizer, will best remedy the deficiencies found in these soils. Using these nutrients could raise the yields of <1t.ha-1 to in excess of 5 t.ha-1. Local soil ameliorants of crushed rock, ash, compost, green manure and termite mounds were also considered with pulverised granite being tested through factorial pot trials to determine its usefulness as a source of K and alkalinity. It raised both soil pH and K levels but is of limited value as these rises were not significant enough to affect yield. It is recommended that future research should: 1) strategically sample across the district, classify soils and determine their fertility status; 2) compile a soil yield potential map and 3) undertake field trials to test the quantities and effectiveness of fertilizers alongside local soil ameliorants.

Highbush blueberry (Vaccinium corymbosum L.) is adapted to soils with high organic matter and acidic pH. Composts provide organic matter and nutrients for growing blueberry in mineral soils, but many composts are high in pH and soluble salts. Acidification with elemental sulfur (S°) can remedy high pH, but the process further increases compost salinity. The objectives of this study were to: i) determine the effects of diverse composts on blueberry growth and nutrient uptake, ii) determine whether S° acidification can ameliorate the negative effects of high compost pH, and iii) develop and validate a simple titration method to determine pH buffering capacity of compost. In our first study, ten composts were evaluated under greenhouse conditions with one-year-old blueberry. Each compost was either acidified or not with S° and then mixed 30% by volume with silt loam soil before planting. Controls were sawdust incorporation or soil only. Plants were managed with a low rate of fertilization to emphasize compost effects on nutrient supply. Compost inorganic nitrogen (N) ranged from 0.1 to 4.1 g∙kg⁻¹, and NO₃-N to NH₄-N ratios were greater than 20:1. Aboveground plant growth and nutrient uptake, including N, phosphorous (P), potassium (K), and boron (B) were higher in soil with compost than in soil with sawdust or soil only. Composts with pH < 7.5 produced more shoot growth than those with higher pH, and composts with EC > 2 dS∙m⁻¹ produced less root growth than those with lower EC. Adding S° reduced compost pH by an average of 1.9 units, and acidification increased shoot and root growth in the composts as well as uptake of many nutrients. Plant growth and N uptake were not correlated with compost N supply. Composts with greater amounts of plant-based feedstocks produced more total shoot growth than manure-based composts. In our second study, 3.7 L blueberry transplants were grown outdoors for 119 d in pots containing compost and soil. Manure feedstocks included separated dairy solids or horse stall cleanings. Plant feedstocks included urban yard trimmings, leaves from street sweeping, conifer bark conditioned with municipal biosolids, or peppermint distillation residue. Control treatments were sawdust amendment or soil only. Plant-based compost treatments had less effect on soil pH and produced 20% greater plant growth than manure-based compost treatments. Plant growth was not different with plant-based composts vs. the sawdust amendment control. Elemental S addition at potting did not acidify soil enough to overcome the increase in pH resulting from compost addition. In our third study, we titrated eight composts with dilute H₂SO₄ to predict response to S° acidification. Our objective was to develop and validate a simple method to determine the pH buffering capacity of compost. Compost pH decreased linearly with laboratory acid addition. Compost pH buffering capacity (linear slope of titration curve) was 0.16 to 0.39 mol H⁺ per kg dry compost per pH unit. To determine correlation between titration and S° acidification, composts samples were incubated with S° at 22° C for 70 d. The majority of the decrease in pH from S° addition occurred within 28 d. Compost pH at 28 d was closely predicted by the laboratory titration. Because of the linearity of compost response to acid addition, a 2-point titration method (one rate of acid addition) is an effective alternative to the 7-point method we used. We conclude that compost pH is the primary limiting factor affecting blueberry response to compost. Compost incorporation provided benefit to blueberry, especially under low N management, and generally increased plant growth and nutrient uptake when compared with plants grown in mineral soil only. Composts made from plant-based feedstocks, rather than manure-based feedstocks, tend to have characteristics which favor blueberry growth, including low buffering capacity, pH, and soluble salts. Feedstocks which showed promise include deciduous leaves, yard debris, bark, and horse bedding with low manure content. Acidification of composts with S° increased plant growth and nutrient uptake, and is a promising technology for eliminating the negative effects of high compost pH. Our method of laboratory titration with dilute acid addition was effective in determining pH buffering capacity of compost, and predicted the compost acidification by S° and the effect of compost on soil pH. / Graduation date: 2012

A study was conducted in 2006 to investigate the long-term effects of air pollution on soil properties in the vicinity of the Arnot power station, Mpumalanga, South Africa. Fifteen sites were re-sampled and the soil chemical properties compared to baseline data gathered in 1996, resulting in a ten year period after which changes in soil properties were investigated. A spatial gradient was incorporated into the study in order to better understand the deposition of pollutants with increasing distance from the power station. The study indicates that long-term acidic deposition has led to detectable changes in soil chemical properties. Three chemical properties, namely the concentrations of calcium and magnesium in both the topsoils and the subsoils, as well as the effective cation exchange capacity in the subsoils showed a significant increase since 1996. However, five soil chemical properties, namely soil pH (K2SO4), the concentration of hydrogen and aluminium and total sulphur in both the topsoils and the subsoils, as well as extractable sulphate in the topsoils and soluble sulphate in the subsoils, all show that the soils have become more acidic over the ten years. The acidic components in the soil override the basic components, as shown by the ratio of basic cations to acidic cations in the soils. The spatial gradient generally indicates that at approximately 8 km from the power station, there is a decrease in the concentration of acidic soil properties and one explanation for this may be a reduction in the acidic components of atmospheric deposition at this site. However, this needs further investigation. Two significant relationships with distance were found, namely a significant negative relationship with soluble sulphate and a significant positive relationship with acid neutralising capacity. This research will form part of a database for other long-term monitoring programmes and will allow data to be compared to other data from this area of research. It will also provide information to important industry leaders such as Eskom.

Made available in DSpace on 2014-06-11T19:22:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-02-09Bitstream added on 2014-06-13T19:27:19Z : No. of bitstreams: 1 deus_acf_me_botfca.pdf: 1380017 bytes, checksum: 6e4d5e1437947fadf9a4d182d77580da (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A eficiência dos corretivos de acidez do solo, e, sua qualidade depende da taxa de reatividade (RE), e do poder de neutralização (PN), sendo esta eficiência indicada pelo poder relativo de neutralização total (PRNT). Para os silicatos existem poucos estudos que estabeleça taxas de reatividade para suas frações granulométricas e, portanto, utilizam-se as mesmas taxas de reatividade do calcário. Foram desenvolvidos três experimentos no período de julho/2008 a outubro/2009 em casa de vegetação na Faculdade de Ciências Agronômicas/UNESP – Botucatu-SP, com o objetivo de comparar valores de reatividade das frações granulométricas para materiais silicatados em três solos de diferentes classes texturais cultivados com plantas de alfafa. Utilizou-se seis materiais corretivos: escória, silicato de cálcio, silicato de cálcio e magnésio, wollastonita, calcário dolomítico e calcário calcítico os quais no experimento 1 e 2 foram separados em quatro frações granulométricas, peneiras: nº 10 (Ø = 2 mm), nº 20 (Ø = 0,84 mm), nº 50 (Ø = 0,30 mm) e fundo (Ø<0,30 mm), exceto a wollastonita que possui apenas a granulometria < 0,30 mm. Os tratamentos foram aplicados em três solos: Latossolo Vermelho distrófico, Nitossolo Vermelho eutrófico e Neossolo Quartzarênico. No 1° experimento aplicou-se quatro doses (1, 2, 4 e 8 t ha-1) afim de obter a curva de neutralização dos solos, para determinar a dose a ser aplicada de cada fração granulométrica para atingir o pH 5,5. O 2° experimento constou da aplicação das doses ecomendadas no primeiro experimento e com o valor de pH obtido aos 90 dias de incubação calculou-se a eficiência relativa de reatividade para cada fração granulométrica, tomando-se como referência o pH obtido com a aplicação do calcário dolomítico na peneira... / The efficiency and quality of materials for soil acidity correction are based on the reactivity rate (RR) and neutralization power (NP), and it is indicated by the effective calcium carbonate (ECC). Considering that there are few studies establishing reactivity rates of silicate particle-size fractions, lime values are used as reference. Three experiments were carried in the period July/2008 to October/2009 out in greenhouse in College of Agricultural Sciences, UNESP, Botucatu – SP, aiming to compare reactivity rates of silicate particle-size fractions in three soils with distinct textures cultivated with alfalfa plants. Slag, calcium silicate, calcium+magnesium silicate, wollastonite, dolomitic and calcitic lime were the materials evaluated. The first and second experiments consisted of four particlesize fractions obtained from each material, separated by the sieves no. 10 (Ø = 2 mm), no. 20 (Ø = 0.84 mm), no. 50 (Ø = 0.30 mm) and bottom (Ø < 0.30 mm), except that the wollastonite has the particle-size fraction < 0,30 mm. Treatments were applied in three soils: Oxisol, Hapludox and Quartzipsamment. In the first study, four doses were applied (1, 2, 4 and 8 t ha- 1) to obtain soil neutralization curve and thus determine which one was to be applied for each particle-size fraction to reach pH 5.5. The second study consisted of the application of the recommended doses from the first experiment. Then, with the pH values obtained 90 days after incubation, the relative efficiency of reactivity was calculated for each particle-size fraction based on the pH of dolomitic lime from the last sieve. Afterwards, RR and ECC were calculated. In the third study, the doses to increase soil base saturation up to 80% were calculated based on both the PRNT reported in the laboratory and in the experiment. Treatments were incubated... (Complete abstract click electronic access below)

Orientador: Carlos Alexandre Costa Crusciol / Banca: José Salvador Simoneti Foloni / Banca: Eduardo Fávero Caires / Resumo: No sistema plantio direto praticamente não há revolvimento do solo e o consequente acúmulo de fertilizantes na superfície acelera o processo de acidificação, contínuo e acentuado que ocorre naturalmente em solos de regiões úmidas, onde, geralmente, é observada baixa disponibilidade de nutrientes e elevados teores de alumínio. Assim, da mesma forma que no sistema de cultivo convencional, no sistema plantio direto também existe a necessidade de aplicação de insumos em superfície, especialmente, materiais corretivos de acidez. Dentro deste enfoque, o trabalho foi desenvolvido na Fazenda Experimental Lageado, pertencente à Faculdade de Ciências Agronômicas - UNESP, Campus de Botucatu (SP), dando continuidade a um projeto de pesquisa que vem sendo conduzido desde 2002, com o objetivo de avaliar o efeito residual da aplicação superficial de corretivos na correção da acidez do solo, bem como na nutrição, na produtividade das culturas da soja e do sorgo e na produção de matéria seca e acúmulo de nutrientes da aveia-preta em região de inverno seco. O delineamento experimental utilizado foi em blocos casualizados em parcelas subdivididas, com 4 repetições. As parcelas foram constituídas por quatro doses de calcário (0, 1000, 2000 e 4000 kg ha-1) e as subparcelas por duas doses de gesso agrícola (0 e 2100 kg ha-1), aplicado em novembro 2004. Como cultura de verão foi utilizada a cultura da soja e na entressafra as culturas da aveia-preta e sorgo granífero. A aplicação de calcário em superfície promoveu diminuição da acidez e elevação nos teores de fósforo, cálcio, magnésio e matéria orgânica, em praticamente todo perfil do solo. A aplicação de gesso agrícola promoveu aumentos nos 2 teores de Ca trocável e S-SO42-, e diminuição no teor de Al trocável no solo... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In no tillage system the absence of soil mobilization consequently decreases places fertilizers on surface, affecting the acidification process. Like in conventional system, in no tillage it is also necessary input application, especially materials for acidity correction. The experiment was carried out in an experimental area, in the city of Botucatu (SP, Brazil), continuing a research project that has been conducted since 2002, to evaluate the long-term effects of surface application of lime and gypsum on acidity correction, nutrition, yield of soybean and sorghum, and dry matter production and nutrients accumulation on black oat in a dry winter region. The experimental design was the completely randomized with subdivided plots and four replications. The mains plots consisted of four dolomite limestone levels (0, 1000, 2000 e 4000 kg ha-1) and the subplots consisted areas with and without gypsum (0 and 2100 kg ha-1), applied in November 2004. Soybean was the summer crops and the off-season crops are black oat and grain sorghum Lime surface application reduced soil acidity and increased phosphorus, calcium, magnesium and organic matter, practically all the soil profile. Phosphogypsum application promoted increasing exchangeable Ca and S-SO42- contents, and decreased exchangeable Al in the soil, favoring the effects of surface liming on soil properties, mainly the surface layer (0-0.20 m). Base saturation values obtained at a depth of 0-0.20 m with liming were lower than those estimated by BS method, even with phosphogypsum application. Liming increased, on soybeans, foliar contents of N, P, Ca, Mg and S in 2008/09, and N, Ca and Mg, in 2009/10. In the presence of phosphogypsum increased the levels of N In no tillage system the absence of soil mobilization consequently... (Complete abstract click electronic access below) / Mestre

Made available in DSpace on 2017-07-10T17:37:53Z (GMT). No. of bitstreams: 1 Tatiane_Ohland.PDF: 1598453 bytes, checksum: ed82eeb6e587304b7aaf365f98d333aa (MD5) Previous issue date: 2012-07-12 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Two experiments were conducted in a greenhouse in pots made of PVC tubes containing 10.6 dm3 of soil, using a randomized complete block design with four replications. The first experiment aimed to evaluate the influence of soil density in the initial development of physic nut (Jatropha curcas L.). The soil used was an Oxisol clayey, in levels of bulk density of 1.08, 1.22, 1.36, 1.50 and 1.64 kg dm-3. After 120 days of plant emergence, was evaluated the number of leaves, plant height, stem diameter, leaf area, root length, root volume, dry matter of leaves + petioles, stems, roots, total dry matter of plant, root/shoot ratio and the content of P, K, Ca and Mg. The results indicate that the increase of soil density negatively affected the development of shoot and root system of plants of physic nut. The limitation of shoot growth occurred from the estimated density of 1.26 kg dm-3, reducing the number of leaves, leaf area and dry matter of shoots. The root system development and content of P and K in plants of physic nut decreased linearly with increasing density. The contents of Ca and Mg is not influenced by increasing the density of the soil. The second experiment aimed to evaluate the initial development of physic nut in different limestone rates in subsurface. The soil used was Oxisol clayey collected in Cascavel - PR. The physic nut plants were grown in PVC pots divided into two rings, the upper ring (0-20) received limed soil (11.1 t ha-1 of CaCO3 and MgCO3) and fertilized, the lower ring (20-60 cm) was added to soil at doses of 0, 3.7, 5.6, 7.4, 11.1 and 14.9 t ha-1 of CaCO3 and MgCO3 in 4:1 molar ratio. After 120 days of plant emergence, was evaluated the number of leaves, leaf area, plant height, stem diameter, root length, root volume, dry matter of leaves, stems, roots, and total dry matter of plant and levels of Al, P, K, Ca, Mg, Zn, Cu, Mn and Fe in leaves, stems and roots. The development of the shoot of physic nut was not limited by the different limestone rates in subsurface, as assessed by plant height, stem diameter, dry matter of leaves, stem and total dry matter of plant. The decrease in limestone rates reduces the volume and dry matters of roots in subsurface. Liming decreased the concentration of Zn and Mn in shoots and roots, which may have influenced the plant height and root volume / Foram conduzidos dois experimentos em casa de vegetação, em vasos constituídos por tubos de PVC contendo 10,6 dm-3 de solo, utilizando o delineamento experimental em blocos casualizados, com quatro repetições. O primeiro experimento teve como objetivo avaliar a influência da densidade do solo no desenvolvimento inicial da cultura do pinhão-manso (Jatropha curcas L.). O solo utilizado foi o Latossolo Vermelho eutroférrico de textura argilosa, sob os níveis de densidade do solo de 1,08; 1,22; 1,36; 1,50 e 1,64 kg dm-3. Após 120 dias da emergência das plantas, avaliou-se o número de folhas, altura de planta, diâmetro de caule, área foliar, comprimento da raiz principal, volume radicular, produção de matéria seca de folhas+pecíolos, caule, raízes, planta inteira, relação raiz/parte aérea e o conteúdo de P, K, Ca e Mg. Os resultados indicam que o aumento da densidade do solo afetou negativamente o desenvolvimento da parte aérea e do sistema radicular de plantas de pinhão-manso. A limitação do desenvolvimento da parte aérea ocorreu a partir da densidade estimada de 1,26 kg dm-3, com redução do número de folhas, área foliar e produção de matéria seca da parte aérea. O desenvolvimento do sistema radicular e o conteúdo de P e K nas plantas de pinhão-manso reduziram linearmente com o aumento da densidade do solo. O conteúdo de Ca e Mg não foi influenciado pelo aumento da densidade do solo. O segundo experimento teve como objetivo avaliar o desenvolvimento inicial do pinhão-manso sob diferentes doses de calcário em subsuperfície. O solo utilizado foi o Latossolo Vermelho distroférrico de textura argilosa coletado em Cascavel - PR. As plantas de pinhão-manso foram cultivadas em vasos de PVC dividido em dois anéis, o anel superior (0-20 cm) recebeu solo corrigido (11,1 t ha-1 de calcário) e adubação com NPK, no anel inferior (20-60 cm) foi adicionado o solo com as doses de 0; 3,7; 5,6; 7,4; 11,1 e 14,9 t ha-1 de CaCO3 e MgCO3 na relação molar 4:1. Após 120 dias da emergência das plantas, avaliou-se o número de folhas, área foliar, altura de planta, diâmetro de caule, comprimento da raiz, volume radicular, produção de matéria seca de folhas, caule, raízes, planta inteira e o teores de Al, P, K, Ca, Mg, Zn, Cu, Mn e Fe nas folhas, no caule e nas raízes. O desenvolvimento da parte aérea do pinhão-manso não foi limitado pelas doses de calcário aplicadas em subsuperfície, avaliado pela altura de planta, diâmetro de caule, produção de matéria seca de folhas, de caule e de matéria seca total. A redução das doses de calcário reduz o volume e a matéria seca de raízes em subsuperfície. A calagem reduziu os teores de Zn e Mn na parte aérea e raízes, o que afetou a altura de planta e volume de raízes

Orientador: Edson Lazarini / Resumo: Em um sistema plantio direto em processo de estabilização, preconiza o não revolvimento do solo. Neste sentido o uso de gesso agrícola pode ser uma alternativa para viabilizar a aplicação do calcário em superfície sem que seja necessária sua incorporação. Dessa forma, o gesso entra como um insumo complementar ao uso do calcário. Em vista do exposto, o presente trabalho objetivou estudar o comportamento do calcário e/ou gesso reaplicados em superfície, e seus reflexos nos atributos químicos do solo e nas culturas do milho e soja em sucessão. O experimento está sendo desenvolvido desde o ano de 2011 em LATOSSOLO VERMELHO distrófico de textura argilosa, desde o ano de 2011, no qual se apresenta em delineamento em blocos ao acaso, em esquema de parcelas sub-subdivididas com quatro repetições. Como tratamentos nas parcelas, foi instalado o milho em dois sistemas de cultivo, sendo eles, solteiro e consorciado com Urochloa. Para as subparcelas foram utilizadas quatro doses de calcário (0; 2000; 4000 e 6000 kg ha-1) e quatro doses de gesso (0; 1500; 3000 e 4500 kg ha-1) distribuídas ao acaso nas sub-subparcelas. As aplicações foram em superfície manualmente em cada parcela e sendo realizadas as seguintes avaliações: características agronômicas, estado nutricional e produtividade de grãos das culturas do milho e soja e os atributos químicos do solo em diferentes profundidades (0,0 – 0,10; 0,10 – 0,20 e 0,20 – 0,40 m). O efeito residual das maiores doses de calcário reaplicados em 2014... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In the process of stabilizing in a no-tillage system, the soil revolving must be minimized. In this sense the application of lime can be an alternative to enable the use of gypsum as an alternative to conditioner the subsurface soil layers in the short term, and it can be used as a complementary product to lime because of its greater solubility and mobility in the soil profile. Therefore, the aim of this experiment was to study the effect of lime and gypsum reapplied in surface and their impacts on maize crop under the sole and intercropped with soybean. The experiment is being developed in a dystrophic Red Latosol with clayey texture, since the year of 2011, and arranged in a randomized block designs, in split-split plots, with four replications. As treatments in the plots, the maize was installed in two cropping systems: sole and intercropped with Urochloa. For the subplots, were used four doses of lime (0; 2000; 4000 and 6000 kg ha-1) and four doses of gypsum (0; 1500; 3000 and 4500 kg ha-1) randomly distributed in the sub-subplots. The applications were manual and in surface in each plot, and being performed the following evaluations: agronomic characteristics, nutritional status and grains yield of maize and soybean and the chemical attributes of soil in three different depth (0,0 – 0,10; 0,10 – 0,20 e 0,20 – 0,40 m). The residual effect of the major gypsum doses reapplied in 2014 provided greater yield on the soybean sown two years after. Higher doses of gypsum reduced ... (Complete abstract click electronic access below) / Mestre

Thesis (M.Sc. Agric (Soil Science)) -- University of Limpopo, 2013 / Knowledge and management of soil pH, particularly soil acidity across spatially variable soils is important, although this is greatly ignored by farmers in the Limpopo Province of South Africa. The significance of understanding spatial variability of soil acidity is the implementation of best and site-specific management strategies because when soil acidity is poorly managed, toxicity and nutrient deficiency problems in the soil are inevitable. The objective of the study was to evaluate in-field spatial variability of soil pH, and compare the efficiency of managing soil pH through site-specific method vs. uniform lime application. The study was conducted in 3 site years (23o50’ S; 29 o40’ E and 23o59’ S and 28o52’ E) with site year I, and II adjacent to each other in the semi-arid regions of the Limpopo Province, South Africa. Soil samples were taken in four replicates within a 1 m radius from geo-referenced locations in 3 study sites to sampling depths of 0-20 cm on a regular grid of 30m using differential Global Positioning System (DGPS). Soils were analyzed for pH, and SMP buffer pH for lime recommendations. Lime requirement to achieve a soil pH of 6.5 for a 20 cm plough layer per hectare was calculated using CalciumCarbonateequivalent, efficiency factor (fineness factor), and neutralizing index of the liming materials. The spatial maps for SMP buffer pH and lime requirement maps were produced with surfer version 8.0 (Surfer Version 8, Golden Software, Golden, CO). The soil pH datasets from systematic unaligned randomly sampled soils on a 30-m grid were interpolated using inverse distance weighing (IDW) in Surfer software version 8.0 (Surfer Version 8, Golden Software, Golden, CO). Soil pH varied from strongly acidic to slightly acidic with minimum values of 4.22, 3.93, and 4.74 and maximum values of 6.11, 7.00, and 6.82 in site I, II, and II respectively. In Site I, II, and III, the areas of the field that had soil pH values of less than 6.0 were 99.43, 82.61, and 62.89% of the field. When lime was recommended for application using a conventional method of uniform lime application based on an average value derived from samples collected in the whole field, the results of the study showed a waste of lime in excess of lime recommended for individual grids. An excess amount of lime as high as 10, 30, and 7 tons/ha recommended on sites I, II and III respectively under uniform application. These recommendations were in excess on field areas that needed little or no lime applications. Again, the fields showed under applications of lime as much as 30, 35, and 13 tons/ha in site I, II, and III respectively for uniform liming applications. This under- and over recommendations of lime based on average soil pH values suggests that uniform soil acidity management strategy is not an appropriate strategy to be adopted in these fields. Again, in both of these sites as shown in the maps, the areas that required high amount of lime and those that require little or no lime are clearly defined, such that the fields can be divided into lime application zones. When a field is divided into lime application zones, management of soil acidity becomes easier because instead of applying variable rates of lime for every grid, lime rates are applied per zone. These zones could be areas in a field that require, (i) high rates of lime, (ii) low rates of lime, and (iii) areas that requires no lime at all. Agricultural fields that exhibit spatial variability of soil acidity must not be managed or treated as uniform when lime is applied in the field. Keywords: Lime requirement, Site specific management and Soil pH.