Made available in DSpace on 2017-07-10T19:24:49Z (GMT). No. of bitstreams: 1 Roseli Regina Rambo Bremm.pdf: 856845 bytes, checksum: 116b2a4bd1fa4adc294e2b393d19bebd (MD5) Previous issue date: 2005-05-20 / The sewage sludge is a by-product resulting of the sewage treatment that contains high organic matter concentration and that, properly applied, it can to supply improvements in the soil fertility. The objective of this study was to evaluate the sewage sludge agricultural potential. The experiment was accomplished in field, in the year of 2004, with randomized blocks, utilizing sewage sludge with neutralization to 50% generated in the SANEPAR Wastewater Treatment Plant, Cascavel, Paraná, Brazil, with 6 treatments: a) mineral fertilizer, b) Control (without fertilization and without sewage sludge), c) 2,5, d) 5, e) 10 and f) 15 Mg.ha-1 of dry sludge, applied to the corn culture in a dystrophic red latossol typical (LVd). Soil samples were collected before installation of experiment for chemical and heavy metal analysis. To the 20, 40, 60 and 80 days after the planting were appraised the parameters of the culture development in the field: stature and diameter of plants and number of leaves. After harvesting the production components were evaluated: length and diameter of spikes, number of useful plants and mass of grains. The soil samples were collected for evaluation of the heavy metals: copper and zinc and chemical analysis. The results were appraised for the software SISVAR.LNK version 13.0 and Minitab being accomplished with Tukey test for comparison of averages with 5% level significance. It was observed that the addition of Copper and Zinc through biossolid contributed with small increment in the tenors of x these in the soil in function of the concentration of the elements in the residue as well as the low amounts applied , and for the parameters of the culture development, the best answers were obtained in the treatments that used the sludge, when compared with the control and fertilizer mineral. For the length and diameter of spikes and mass of grains the largest averages were obtained in the 15 Mg.ha-1 of sludge treatment. / O lodo de esgoto é um subproduto resultante do tratamento de esgotos que contém elevado teor de matéria orgânica e se, devidamente aplicado, pode conferir ao solo melhorias em relação a sua fertilidade. Neste contexto, o presente trabalho teve por objetivo avaliar o potencial agrícola do lodo de esgoto como fertilizante na cultura do milho. O experimento foi realizado em campo, no ano de 2004, com delineamento experimental em bloco inteiramente casualizado, utilizando-se lodo de esgoto calado a 50% proveniente da Estação de Tratamento de Esgoto da SANEPAR Cascavel PR, com 6 tratamentos: a) Adubação convencional, b) Testemunha (sem adição de biossólido e sem adubação convencional), c) 2,5 Mg.ha-1, d) 5 Mg.ha-1, e) 10 Mg.ha-1 e f) 15 Mg.ha-1 base seca do biossólido, aplicado à cultura do milho em um Latossolo Vermelho distroférrico típico. Foram coletadas amostras para análise química e teores totais de metais pesados no solo antes da instalação do experimento. Aos 20, 40, 60 e 80 dias após o plantio, foram avaliados os parâmetros de desenvolvimento da cultura no campo: estatura da planta, diâmetro do colmo e número de folhas. Após a colheita, foram avaliados os parâmetros: comprimento e diâmetro das espigas, número de plantas úteis por parcela e massa de grãos. Na data da colheita, foi coletada amostra de solo na camada de 0-20cm para avaliação do teor de Zinco e Cobre e análise química. Os resultados foram avaliados pelo software SISVAR.LNK versão 13.0 e Minitab, ix sendo realizado o teste de Tukey para comparação de médias ao nível de 5% de significância. Observou-se que a adição de Cobre e Zinco via biossólido contribuiu com pequeno incremento nos teores destes no solo em função da concentração dos elementos no resíduo, bem como as baixas dosagens aplicadas, sendo que para os parâmetros de desenvolvimento da cultura, as melhores respostas foram obtidas nos tratamentos que empregaram o biossólido nas diferentes dosagens, quando comparados com a testemunha e adubação convencional. Para o diâmetro e comprimento das espigas e massa de grãos, a maior média foi obtida no tratamento que empregou 15 Mg.ha-1 de biossólido.

A agropecuária tem um importante papel na economia do Brasil. Fertilizantes nitrogenados estão entre os principais insumos da agropecuária mundial, e o seu uso em grandes volumes geram problemas ambientais. Sistemas Integrados de Produção Agropecuária (SIPAs) buscam a maior eficiência no uso dos recursos naturais em comparação às monoculturas agrícolas, reduzir as perdas de nutrientes e promover a ciclagem do nitrogênio (N). O animal é considerado um catalizador da ciclagem de nutrientes e em um SIPA a intensidade de pastejo e a fertilização, são as principais variáveis a ser manejada na fase pastagem, pois determinam a cobertura do solo, que é transferida para a fase lavoura e influencia a sua produtividade. A soja e o milho estão entre as mais importantes culturas da agricultura Brasileira. A soja tem o potencial de suprir parte das suas demandas através da Fixação Biológica de N, já o milho é dependente do solo para atender a sua necessidade por N. A adubação antecipada baseia-se em que a exportação de nutrientes na fase lavoura é maior do que na fase pastagem. Propõe-se que a adubação seja realizada no inverno, promovendo maiores rendimentos da fase pastagem e a ciclagem dos nutrientes para a fase lavoura. O objetivo deste trabalho foi avaliar o efeito da adubação nitrogenada em pastagem de azevém pastejada por ovinos sob diferentes intensidades de pastejo e métodos de pastoreio no índice de nutrição nitrogenada das culturas de verão em SIPAs. Este estudo foi realizado entre os anos 2013 e 2014, em um experimento de longa duração iniciado em 2003, em SIPA, o qual é composto por 32 unidades experimentais delineados em blocos casualizados, com quatro tratamentos, dois métodos de pastoreio, contínuo e rotativo, duas intensidades de pastejo, moderada e baixa em pastagem de azevém-anual pastejada por ovinos, no período de inverno e dois sistemas de cultivos de verão, monocultivo de soja e rotação soja/milho, com quatro repetições. A fertilização foi realizada exclusivamente na fase pastagem com 75 kg de N e 60 kg de P2O5 e K2O ha-1. A massa de forragem residual (MFR) foi avaliada ao final da fase pastagem. Durante o verão foram avaliados o rendimento de fitomassa das culturas de verão durante a fase vegetativa, o teor de N na fitomassa e o Índice de Nutrição Nitrogenada (INN) das culturas. Para a cultura do milho, houve efeito das intensidades de pastejo (P<0,05) para INN e MFR. Para as culturas da soja houve efeito das intensidades de pastejo (P<0,05) apenas para a MFR. Não foi encontrada diferença entre os métodos de pastoreio para as duas culturas. A MFR é uma importante fonte de N para a cultura de verão subsequente. Menores intensidades de pastejo resultam em maiores MFR e, consequentemente, maiores INN para a cultura do milho. A adubação nitrogenada antecipada não apresentou efeito sobre a soja uma vez que esta cultura tem a capacidade de atender a sua demanda por N através da Fixação Biológica de N. / Agriculture has an important role in Brazilian economy. Nitrogen fertilizers are among the main inputs of worldwide agriculture, and its use in large volumes has generated environment problems. Integrated Crop Livestock Systems (ICLS) search for a more efficient use of natural resources than monoculture agriculture systems, reduce Nitrogen (N) losses and promote its cycling. The animal is consider a catalyst for nutrient cycling and in an ICLS, the grazing intensity along with fertilization, are the main variable to be manage in the pasture phase, since it determines the soil cover, which is transfer to the crop stage and directly influences its yield. Soybean and maize are among the most important crops of the Brazilian agriculture. Soybean has the potential to attend most of their demands for nitrogen (N) through the Biological Fixation, on the other hand, maize is dependent on soil fertility to attend their need for this nutrient. Early fertilization is based on that the export of nutrients in the crops phases is greater than pasture phase. Is propose that the fertilization should be manage on winter, because it would provide higher yields of pasture phase and recycling of nutrients to the crop stage. The objective of this study was to evaluate the effect of early nitrogen fertilization on Italian ryegrass pasture grazed by sheep under different grazing intensities and grazing methods on ICLS summer crops nitrogen nutrition index. This work was perform between 2013 and 2014, in a long-term ICLS experiment, with 32 experimental units designed in a randomized block with four treatments and four replications. The treatments were two stocking methods, continuous and rotational grazing, two grazing intensities, moderate and low, with Italian ryegrass grazed by sheep on winter, and two cropping systems, soybean monoculture and soybean/maize crop rotation, on summer. The fertilization management was 75 kg of N, 60 kg of P2O5 and K2O ha-1. The residual forage mass (RFM) on the end of grazing phase. During summer were evaluate the crops biomass yield on vegetative phase, the N content on the phytomass, and the crops NNI. On maize crop area were found effect of the grazing intensities (P<0.05) on the RFM and NNI. On soybean crop area was found effect of the grazing intensities (P<0.05) on the RFM. There were no differences between the grazing methods in both crop systems, and on RFM and NNI of soybeans areas (P>0.05). The RFM is an important summer crop N source. Lowest grazing intensities result on higher RFM, and consequently in higher NNI on maize crop. The early fertilization does not cause effects on soybean, once this crop has the ability to meet its demand for N by N Biological Fixation.

Made available in DSpace on 2017-05-12T14:48:13Z (GMT). No. of bitstreams: 1 Roseli Regina Rambo Bremm.pdf: 856845 bytes, checksum: 116b2a4bd1fa4adc294e2b393d19bebd (MD5) Previous issue date: 2005-05-20 / The sewage sludge is a by-product resulting of the sewage treatment that contains high organic matter concentration and that, properly applied, it can to supply improvements in the soil fertility. The objective of this study was to evaluate the sewage sludge agricultural potential. The experiment was accomplished in field, in the year of 2004, with randomized blocks, utilizing sewage sludge with neutralization to 50% generated in the SANEPAR Wastewater Treatment Plant, Cascavel, Paraná, Brazil, with 6 treatments: a) mineral fertilizer, b) Control (without fertilization and without sewage sludge), c) 2,5, d) 5, e) 10 and f) 15 Mg.ha-1 of dry sludge, applied to the corn culture in a dystrophic red latossol typical (LVd). Soil samples were collected before installation of experiment for chemical and heavy metal analysis. To the 20, 40, 60 and 80 days after the planting were appraised the parameters of the culture development in the field: stature and diameter of plants and number of leaves. After harvesting the production components were evaluated: length and diameter of spikes, number of useful plants and mass of grains. The soil samples were collected for evaluation of the heavy metals: copper and zinc and chemical analysis. The results were appraised for the software SISVAR.LNK version 13.0 and Minitab being accomplished with Tukey test for comparison of averages with 5% level significance. It was observed that the addition of Copper and Zinc through biossolid contributed with small increment in the tenors of x these in the soil in function of the concentration of the elements in the residue as well as the low amounts applied , and for the parameters of the culture development, the best answers were obtained in the treatments that used the sludge, when compared with the control and fertilizer mineral. For the length and diameter of spikes and mass of grains the largest averages were obtained in the 15 Mg.ha-1 of sludge treatment. / O lodo de esgoto é um subproduto resultante do tratamento de esgotos que contém elevado teor de matéria orgânica e se, devidamente aplicado, pode conferir ao solo melhorias em relação a sua fertilidade. Neste contexto, o presente trabalho teve por objetivo avaliar o potencial agrícola do lodo de esgoto como fertilizante na cultura do milho. O experimento foi realizado em campo, no ano de 2004, com delineamento experimental em bloco inteiramente casualizado, utilizando-se lodo de esgoto calado a 50% proveniente da Estação de Tratamento de Esgoto da SANEPAR Cascavel PR, com 6 tratamentos: a) Adubação convencional, b) Testemunha (sem adição de biossólido e sem adubação convencional), c) 2,5 Mg.ha-1, d) 5 Mg.ha-1, e) 10 Mg.ha-1 e f) 15 Mg.ha-1 base seca do biossólido, aplicado à cultura do milho em um Latossolo Vermelho distroférrico típico. Foram coletadas amostras para análise química e teores totais de metais pesados no solo antes da instalação do experimento. Aos 20, 40, 60 e 80 dias após o plantio, foram avaliados os parâmetros de desenvolvimento da cultura no campo: estatura da planta, diâmetro do colmo e número de folhas. Após a colheita, foram avaliados os parâmetros: comprimento e diâmetro das espigas, número de plantas úteis por parcela e massa de grãos. Na data da colheita, foi coletada amostra de solo na camada de 0-20cm para avaliação do teor de Zinco e Cobre e análise química. Os resultados foram avaliados pelo software SISVAR.LNK versão 13.0 e Minitab, ix sendo realizado o teste de Tukey para comparação de médias ao nível de 5% de significância. Observou-se que a adição de Cobre e Zinco via biossólido contribuiu com pequeno incremento nos teores destes no solo em função da concentração dos elementos no resíduo, bem como as baixas dosagens aplicadas, sendo que para os parâmetros de desenvolvimento da cultura, as melhores respostas foram obtidas nos tratamentos que empregaram o biossólido nas diferentes dosagens, quando comparados com a testemunha e adubação convencional. Para o diâmetro e comprimento das espigas e massa de grãos, a maior média foi obtida no tratamento que empregou 15 Mg.ha-1 de biossólido.

<p>Korisni mikroorganizmi ili mikroorganizmi promotori biljnog rasta (PGPM) ispoljavaju efekat na rast i razviće biljaka azotofiksacijom, mobilizacijom hraniva (N, P, Fe) u zemlji&scaron;tu i produkcijom fitohormona te na taj način stimuli&scaron;u rast biljaka, povećavaju prinos i &scaron;tite biljke od patogena. Cilj ovih istraživanja bio je da se izvr&scaron;i karakterizacija bakterija izolovanih iz rizosfere kukuruza, inokulacija semena kukuruza odabranim izolatima, ispitivanje efektivnosti primene pojedinačnih i združenih kultura izolata na mikrobiolo&scaron;ku aktivnost u rizosfernom zemlji&scaron;tu, kao i na početni rast i razvoj biljke, sadržaj pojedinih hranljivih elemenata u biljnom materijalu i prinos kukuruza. Kori&scaron;ćeno je 50 izolata iz rizosfernog zemlji&scaron;ta hibrida kukuruza NS 6010 gajenog na zemlji&scaron;tu tipa karbonatni černozem (13 izolata roda Azotobacter, 16 izolata roda Bacillus, 15 izolata roda Pseudomonas, 6 izolata roda Streptomyces). Karakterizacija izolata obuhvatila je određivanje morfolo&scaron;kih, fiziolo&scaron;kih, biohemijskih i PGP osobina. Inokulacija semena kukuruza izvr&scaron;ena je s osam odabranih izolata primenjenih pojedinačno i u sme&scaron;i i to s tri izolata azotobaktera (Azb5, Azb8, Azb13), s dva izolata bacilusa (Bac9, Bac15 ), s dva izolata pseudomonasa (Pse1, Pse5) i s jednim izolatom aktinomiceta (Act6). U ogledima su kori&scaron;ćeni hibridi kukuruza NS 6010 i NS 6030 selekcionisani u Odeljenju za kukuruz Instituta za ratarstvo i povrtarstvo, a efektivnost primene odabranih izolata na mikrobiolo&scaron;ku aktivnost u rizosfernom zemlji&scaron;tu, kao i na biljku kukuruza, ispitana je u polukontrolisanim i poljskim uslovima. Brojnost mikroorganizama određena je metodom agarnih ploča, a dehidrogenazna aktivnost spektrofotometrijskom metodom. Uticaj izolata na klijanje semena ispitan je u laboratorijskim uslovima. Uticaj izolata na početni rast<br />biljaka ispitan je u fazama 3. i 5-7. lista merenjem visine i suve mase nadzemnog dela<br />biljke. Sadržaj azota, fosfora, bakra i cinka u biljnom materijalu (nadzemni deo/list)<br />određen je u fazi 5-7. lista kukuruza za ogled u polukontrolisanim uslovima i u fazi svilanja<br />za ogled u polju. Ukupan prinos zrna kukuruza po jedinici povr&scaron;ine određen je<br />preračunavanjem prinosa po svakoj elementarnoj parceli. Najbolji efekat na brojnost<br />mikroorganizama dobijen je primenom izolata A zb5, B ac15, P se1, A ct6 i sme&scaron;e i zolata.Na povećanje dehidrogenazne aktivnosti najvi&scaron;e je uticala primena izolata Azb5, Azb8,<br />Bac15 i Act6. Inokulacija je imala pozitivan uticaj na klijavost, visinu i suvu masu<br />nadzemnog dela biljke, sadržaj N, P, Zn i Cu u biljnom materijalu, kao i prinos kukuruza.<br />Najbolji efekat na visinu i masu nadzemnog dela biljke u polukontrolisanim uslovima<br />utvrđen je sa izolatima azotobaktera, Bac15 i Pse1, dok je u poljskim uslovima najveće<br />povećanje ovih parametara dobijeno primenom izolata Pse5 i Act6. U proseku, najbolji<br />efekat na prinos dobijen je primenom sme&scaron;e izolata. Rezultati ovih istraživanja treba da<br />posluže kao osnova za dalja istraživanja koja će omogućiti odabir visoko kompatibilne<br />zajednice ispitivanih hibrida kukuruza i najefektivnijih vrsta PGPM u cilju proizvodnje<br />mikrobiolo&scaron;kog preparata kojim bi se ostvario veći prinos i omogućilo održavanje i<br />povećanje plodnosti zemlji&scaron;ta.<br />&nbsp;</p> / <p>Beneficial or plant growth promoting microorganisms (PGPM) exert effect on plant growth and development through nitrogen fixation, mobilization of nutrients (N, P, Fe) in soil and production of phytohormones and thereby stimulate plant growth, increase yield and reduce pathogen infection. The aim of this study was to perform characterization of bacteria isolated from maize rhizosphere, inoculation of maize seeds with selected isolates, testing the effectiveness of single and co-inoculation on microbial activity in rhizosphere, as well as on initial growth and development of plants, content of some nutrients in plant material and yield of maize. 50 isolates from rhizosphere of maize hybrid NS 6010 grown on calcareous chernozem soil (13 isolates of the genus Azotobacter, 16 isolates of Bacillus, 15 isolates of Pseudomonas, 6 isolates of Streptomyces) were used. Characterization of isolates included determination of morphological, physiological, biochemical and PGP traits. Inoculation of maize seeds was carried out with eight selected strains applied individually and in mixture, and that with three isolates of Azotobacter (Azb5, Azb8, Azb13), two isolates of Bacillus (Bac9, Bac15), two isolates of Pseudomonas (Pse1, Pse5) and one isolate of Streptomyces (Act6). The experimental objects were maize hybrids NS 6010 and NS 6030 developed at Maize Department, Institute of Field and Vegetable Crops, and the effectiveness of selected isolates on microbial activity in rhizosphere, as well as on maize plant, was tested in semi-controlled and field conditions. The number of microorganisms was determined by agar plates method, and dehydrogenase activity by spectrophotometric method. Effect of isolates on maize seed germination was tested in the laboratory. The effect of isolates on initial plant growth was tested at 3 and 5-7 leaf stages by measuring height and dry weight of above ground plant parts. The contents of nitrogen, phosphorus, copper and zinc in plant material (above ground part/leaf) were determined at 5-7 leaf stage for experiment in semi-controlled conditions and at silking stage for field trial. Thetotal grain yield per unit area is determined by recalculating yield for each elementary</p><p>plot. The best effect on the number of microorganisms was obtained by applying Azb5,<br />Bac15, Pse1, Act6 and mixtures of isolates. The largest increase in dehydrogenase activity<br />was achieved with isolates Azb5, Azb8, Bac15 and Act6. Inoculation had a positive impact<br />on germination, height and dry weight of above ground part of the plant, the content of<br />N, P , Z n and C u i n p lant material, as well as the yield of maize. The best effect on the<br />height and weight of above ground part of the plant in semi-controlled conditions was<br />achieved with isolates of azotobacters, Bac15 and Pse1, while in field conditions the<br />largest increase in these parameters was obtained with isolates Pse5 and Act6. On average,<br />the best effect on yield was obtained by using a mixture of isolates. The results of this<br />study should be the basis for further research which would allow the selection of highly<br />compatible community of maize hybrids and the most effective strains of PGPM and be<br />used in the production of microbial preparations in order to achieve higher yields and<br />facilitate the maintenance and increase fertility of soil.<br />&nbsp;</p>

A consorciação do milho com gramíneas forrageiras pode ser utilizada tanto para renovações de pastagens, como para a formação de cobertura morta de qualidade e longevidade para o sistema de Plantio Direto. O objetivo deste trabalho foi avaliar as interações e interferências de diferentes espécies de braquiárias no desempenho da cultura de milho, bem como determinar qual das espécies seria a mais adequada para o sistema de consórcio. O experimento foi conduzido em Nitossolo eutrófico típico, sob pivô central, em área experimental pertencente ao Departamento de Produção Vegetal da Escola Superior de Agricultura "Luiz de Queiroz"/ Universidade de São Paulo, situado no Município de Piracicaba, SP. O delineamento experimental utilizado foi o de blocos ao acaso com sete tratamentos e quatro repetições. Os tratamentos foram constituídos da combinação de três espécies de braquiárias (Brachiaria decumbens, Brachiaria brizantha e Brachiaria ruziziensis) semeadas em duas épocas (concomitantemente ao milho e quando o milho apresentava quatro folhas totalmente expandidas), acrescido de um tratamento testemunha (milho solteiro). Com relação ao milho, os resultados evidenciaram ausência de diferença estatística entre os tratamentos para as seguintes variáveis: altura de plantas; índice de área foliar; diâmetro do colmo; análise foliar; número de fileiras de grãos; número de grãos por espiga; peso de mil grãos e produtividade. Todavia, o número de folhas de milho e a sanidade de espigas foram afetados pelos tratamentos estudados. Assim, o tratamento 6 (B. brizantha semeada na quarta folha do milho) propiciou maior número de folhas em plantas de milho e a B. decumbens semeada na mesma data do milho propiciou menor taxa de grãos deteriorados na espiga em comparação ao tratamento testemunha. Com relação às braquiárias, todas as espécies semeadas na primeira época (semeadura concomitante ao milho) diferiram daquelas semeadas quando o referido cereal apresentava quatro folhas, quanto à produção de massa verde e seca. A B.decumbens e a B. brizantha, semeadas na primeira época, apresentaram maior produção de matéria seca de raiz em comparação à B. brizantha, semeada na segunda época. Após a roçagem, a produção de massa verde e seca de parte aérea das B. decumbens e B. brizantha semeadas na primeira época foi superior à produção da B. ruziziensis semeada na segunda época. A B. decumbens, independentemente da época de semeadura, apresentou maior efeito supressor de plantas daninhas. Assim, a análise e a interpretação dos resultados, permitiram concluir que a presença das braquiárias, indiferentemente à época de semeadura, não afeta o desenvolvimento e a produtividade do milho, demonstrando a viabilidade técnica de sistemas consorciados de produção. Entretanto, a presença do milho influencia negativamente o acúmulo de fitomassa das braquiárias, principalmente, quando estas são semeadas quando o milho apresenta quatro folhas. Para a formação de pastagens, as forrageiras estudadas apresentam melhor desempenho e produtividade quando implantadas na mesma data da cultura do milho. Dentre as braquiárias, destaca-se a B. decumbens pela quantidade de forragem produzida, bem como pelo efeito supressor de plantas daninhas. Entretanto, para a produção de forragem a B. brizantha apresenta resultados semelhantes a B. decumbens. / Maize intercropped with grass can be used both to pasture renewals and to quality and longevity of soil cover formation in no-tillage system. The present work aimed at evaluating the interactions and interferences of different brachiaria species on maize yield, as well as determining which would be the most appropriate species for a intercropping system. The experiment was carried out in Piracicaba, São Paulo State, Brazil (Universidade de São Paulo, ESALQ), in a typical Rhodudalf soil, under central pivot, in an experimental area belonging to the Department of Crop Production. The experimental design was in randomized blocks with seven treatments and four replications. The treatments consisted of a combination of three brachiaria species (Brachiaria decumbens, Brachiaria brizantha and Brachiaria ruziziensis) sowed in two different dates (together with maize and when maize had four fully expanded leaves), as well as a control treatment (single maize). In relation to maize, the results showed no statistical differences among the treatments for the following parameters: plant height; leaf area index; stem diameter; foliar analysis; number of grain rows; number of grain per rows in ear; thousand grain weight and productivity. However, the number of maize leaves and the sanity of ears were affected by the treatments. Thus, treatment 6 (B. brizantha sowed at the four leaves stage of maize) favored larger number of leaves on maize plants, and B. decumbens sowed on the same dates as maize presented lower rate of deteriorated grains per spike in comparison to the control treatment. In relation to brachiaria, all of the species sowed on the first date (concomitant sowing with maize) differed from those sowed at the four leaves stage of maize, for green and dry mass production. The B. decumbens and B. brizantha, sowed in the first time, presented larger production of root dry matter in comparison to B. brizantha, sowed on the second date. After cutting, the green and dry mass production of shoot of B. decumbens and B. brizantha sowed on the first date was superior to the green and dry mass production of B. ruziziensis sowed on the second date. B. decumbens, regardless of the sowing date, presented a greater suppressor effect on weeds. The analysis and the interpretation of the results allowed to conclude that the presence of brachiaria, regardless of sowing date, doesn't affect the development and the productivity of maize, thus demonstrating the technical viability of intercropped systems of production. However, the presence of maize negatively influences the biomass accumulation of brachiaria, especially, when these are sowed when maize has four leaves. For pasture formation, the studied forage grasses present better yield and productivity when sowed at the same date as maize. Among the brachiaria, B. decumbens stands out for the amount of forage produced, as well as for the suppressor effect on weeds. However, for forage production, B. brizantha presents similar results to B. decumbens.

Stable carbon isotope analyses of the humin fraction of the soil organic matter were conducted on more than 160 soil profiles from Tikal, Guatemala. The profiles were collected from near areas associated with the earthworks of Tikal; an ancient ditch and parapet construction hypothesized to have formed ancient boundaries of the polity. In addition to the isotope analyses, the physical and chemical characteristics of the horizons were determined. Maize, a C4 plant, formed an integral part of the ancient Maya diet and is the only known C4 plant cultivated by the Maya. Prior to and subsequent to the ancient Maya occupation of Tikal, the landscape was dominated by C3 forest vegetation. Over the centuries C4 plant biomass including rhizodeposition decomposed to form soil organic matter that contains a distinct C4 signature reflecting the vegetation history of the area. Forested areas anciently cleared for agriculture were identified through interpretation of significant isotopic shifts that signaled past vegetation changes. Buried horizons were encountered in the upland depressions and bajo wetlands. The aggraded soil deposits were likely the result of increased human activity related to settlement and agriculture. The buried horizons and the overlying sediments exhibited stable carbon isotope shifts associated with forest clearance and maize agriculture. Geospatial analysis of the stable carbon isotope ratios indicated that ancient Maya agriculture was focused on deeper footslope and toeslope soils in both bajos and upland depressions. Some evidence of infield agriculture or food processing was also encountered in connection with ancient settlement at upland locations. The soil data provide insight into ancient land use and sustainability that could potentially contribute to subsistence and population reconstruction models.

Thesis (M.Sc. (Agriculture)) --University of the North, 1985 / Refer to the document / University of the North, HSRC (Human Science Research Council), and Lebowa Project Committee

Thesis (M.Sc. Agric. (Agricultural Economics)) -- University of Limpopo, 2018 / Agriculture is the backbone and a very important sector of the South African economy. This is because it provides food and employment to a lot of people in the country especially those living in the rural areas. Smallholder farmers also play an important role in livelihood creation and also alleviation of poverty among the population in Limpopo province, but despite this, their productivity is low. A decline in agricultural productivity reduces market access resulting from low quality and quantity of produce by smallholder farmers which invariably affect their accessibility to market. This study therefore examined the determinants of market access and productivity among smallholder maize farmers in Lepelle-Nkumpi municipality using the Probit model and Cobb Douglass production functions. While the Probit regression model was used to analyse the effect of socioeconomic characteristics of smallholder maize farmers on market access, the Cobb Douglass production function was used to examine the determinants of productivity among the farmers in the study area. The results of the Probit regression analysis indicated that farm size, hired labour and maize produced per hectare had positive significant influence on probability of farmers accessing markets. Farm size and maize produced per hectare were statistically significant at 1% and hired labour was statistically significant at 5%. The results of Cobb Douglas Production Function indicated that the elasticities of market access, farm experience, fertilizers, capital and membership of association were significant and positive. Based on the study findings, it is recommended that farmers should be provided with market infrastructure and marketing information services. This will help the farmers in a way that the transaction cost will be minimised and farmers will not incur more cost when they participate in the markets. Farmers in the study area indicated that transportation cost is the major challenge facing them. This is because of the poor conditions of roads in the study area. Therefore, the study recommends that there should be inputs subsidy that helps farmers to improve their productivity.

Thesis (M.Sc. Agric. (Agronomy)) --University of Limpopo, 2018 / Two experiments were conducted at Ukulima Root Biology Centre, Waterberg district in Limpopo Province (24°32'58.1"S, 28°06'21.1"E) during 2013-2014 cropping season to select IBM population inbred lines with improved root whorl and stem diameter that can enable them to tolerate nitrogen and phosphorus stress. The experiments were laid out in a Split plot format based on a randomized complete block design with four replicates. The main plot factors were: nitrogen levels (low and high) and phosphorus (low and high), in the respective trials and maize inbred lines (MO345, MO034, MO001, MO199, MO031 and MO196) were in the sub plots. Traits investigated included shoot morphological traits (plant height, leaf area per plant, chlorophyll content, stem diameter, number of leaves), root architectural traits (Whorl angles, root area, average root density, number of adventitious roots, number basal roots, average lateral root length, lateral branching frequency, root top angle, root bottom angle, distance to the first lateral root) and dry biomass. Results showed morphological traits, root architectural traits and biomass were affected by nitrogen fertilizer. Those traits were greater under high nitrogen level. On the other hand nitrogen had no influence on stem diameter size variation and whorl distribution. Plant height, number of leaves and dry biomass were significantly different among the inbred lines. The interaction of inbred and nitrogen fertilizer level had significant effect on leaf width and leaf area per plant. The lowest leaf width was recorded on inbred MO345 under low nitrogen level, while the highest value was recorded on inbred MO345 under high nitrogen level. Inbred MO031 and MO199 had highest values of leaf area per plant under high nitrogen level and inbred MO345 had the lowest value under low nitrogen level. Inbred lines planted under high nitrogen level had relative advantage in leaf growth over inbred lines planted under low nitrogen level. The study showed that nitrogen fertilizers have positive effect on some root architectural traits and growth parameters of maize. Maximum leaf area was obtained by inbred MO031 and MO199 under high nitrogen level. Thus, in order to enhance leaf growth and physiological traits, the use of either MO031 or MO199 is recommended under high nitrogen level while any of these inbred lines MO001, MO034 or MO199 can be used under low nitrogen production as they are highly tolerant to low soil xiv nitrogen. Morphological and root architectural traits correlated positively with dry biomass in both low and high N level. Results from the phosphorus split plot showed that only projected root area was affected by phosphorus level. Chlorophyll content, plant height, 1st whorl angle, 4th whorl angle, root top angle, root bottom angle, average lateral root length and lateral branching frequency differed significantly among the inbred lines. The interaction effect of phosphorus and inbred on root top angle and average lateral root length was significant. Inbred MO199, inbred MO034 and MO031 recorded the shallowest angles under low and high phosphorus level respectively, while inbred MO345 recorded the steeper root top angle at 54.44° under high phosphorus level. Thus to enhance P uptake, inbred MO199 is a potential candidate on low P soils. To improve water and N acquisition efficiency inbred MO345 with high phosphorus level can be used, therefore MO345 with high phosphorus can be recommended for water scarce areas such as Limpopo province. Inbred MO199 had the longest lateral roots of 251.46 mm under lower P level and significantly longer than inbred MO199 and MO001 both at lower phosphorus level. Inbred MO345 (182.88 mm) and MO001 (179.22 mm) were highly tolerant to the low P conditions as the two had shorter lateral roots, a trait vital for uptake of P. Inbred MO199 (251.46 mm) had the longest lateral roots under low P conditions showing higher tolerance to low P conditions. There were positive and significant correlations between dry biomass and morphological traits and root architectural traits on both low and high phosphorus levels. A strongly negative correlation was however observed between biomass and 2nd whorl angle on high phosphorus level. The high significant correlations indicate that selection of high yielding inbreds may be useful based on phosphorus level and biomass. This study showed that several traits have potential under low N and P levels, hence they can be used as selection criteria for inbred lines with improved nutrient use efficiency. Keywords: Maize inbred lines, fertilizer, growth, correlation, root angles

Epigenetics is the study of heritable changes in phenotypes that are not the result of changes in DNA sequence. Examples of epigenetic affecters include methylation changes, chromatin modifications, transcription factors, and RNA-based changes. The molecular mechanisms behind epigenetic changes are not fully understood. Canalization is the buffering of gene expression against environmental changes over time, while habituation is semi-stable expression change over time due to selection. This work characterized the molecular changes associated with the kernel color changes of the R-sc:86-17pale allele at the maize red color1 (r1) locus to determine if the changes are epigenetic in nature. The research; 1) quantified the color differences between the progenitor and habituated sublines; 2) Determined that there are not sequence differences between the progenitor and habituated sublines at the 3` end of the Sc||nc1 gene that could account for changes in seed color; 3) and examined the cytosine methylation patterns at the 3` end of the Sc||nc1 gene of the habituated sublines and the progenitor to determine whether there are methylation differences that correspond with the kernel color changes. Quantification of the kernel colors of the R-sc:86-17pale selection sublines showed that there was a statistically significant difference in kernel color. The identical sequence of the R-sc:86 line and the R-sc:86-17pale Lightest and R-sc:86-17pale Darkest sublines at the 3` end of the Sc||nc1 gene is evidence that the kernel color change is not driven by differences in sequence within the r1 gene. The methylation data suggests that some methylation differences in the R-sc:86-17pale Lightest and R-sc:86-17pale Darkest sublines are present, and suggests that the molecular basis of the kernel color is epigenetic in nature.