Agricultural land in China is being degraded, with soil erosion becoming an increasing problem. In Yunnan Province, south-west China, there is a long history of soil erosion due to soil type, climate, anthropogenic influence and because 95% of the Province is mountainous. Population pressure and lack of flat land necessitate cultivation of steep slopes. The Yunnan Government prohibits cultivation of slopes >25°, however policy enforcement would result in food shortages in the Province, due to a lack of suitable land <25°. Therefore, the most appropriate way to curb soil erosion in Yunnan is to devise affordable agronomic means of reducing soil loss, which do not decrease crop productivity on sloping land currently under cultivation. At present, very little research has addressed these issues. A research project, building on existing work from 1993-1996, was initiated in 1998. The aim was to test the hypothesis that contour cultivation and contour cultivation plus straw mulch decrease runoff and soil erosion rates on sloping land in Yunnan Province under maize cultivation and to assess the impact of these conservation measures on maize productivity and soil nutrient status. Thirty runoff plots, located on three different slope angles (I 3°, II 10° and III 27°), in three groups of 10, were used to examine three cropping treatments in a replicated plot design in 1998 and 1999. Treatments were downslope cultivation (control), contour cultivation and contour cultivation plus straw mulch. In addition, there was an unreplicated bare plot in each group. Runoff and soil loss were measured on a storm-by-storm basis. Soil nutrient status was measured at the beginning and end of each cropping season. Crop growth parameters and soil physical properties were measured throughout the cropping seasons (21/05–7/10 in 1998 and 22/05–2/10 in 1999). In 1998, seasonal rainfall was 1024 mm, ~28% greater than the 30-year mean. Soil loss was significantly reduced by contour cultivation on Slopes I and II. On Slope I, downslope cultivation produced 3.07 t ha-1 soil loss and contour cultivation reduced this by 81.4 %. On Slope II, downslope cultivation produced 19.11 t ha-1 and contour cultivation reduced this by 58.0%. The addition of straw mulch gave a further, nonsignificant, reduction on both slopes. On Slope III, downslope cultivation and contour cultivation produced 6.92 and 6.29 t ha-1 of soil loss, respectively, with contour cultivation plus straw mulch having 99.4% less erosion than downslope cultivation. In the much drier 1999 season, no treatment significantly reduced soil loss on Slope I. Contour cultivation significantly reduced soil loss on Slopes II and III. On Slope II, downslope and contour cultivation produced 11.52 t ha-1 of soil loss and contour cultivation reduced this by 85.8%. On Slope III, downslope and contour cultivation produced 8.62 and 0.23 t ha-1, respectively; a reduction of 97.3% by contour cultivation. The addition of straw mulch did not further decrease soil loss. Treatment effects on soil nutrient status varied between the two years. At the end of the 1998 season, there was significantly higher soil available N under contour cultivation plus straw mulch on all three slopes (Slopes I and II P <0.001, Slope III P <0.05), an effect that was not found in 1999. At the end of the 1999 season, soil available K was significantly (P <0.001) higher under contour cultivation plus straw mulch on Slope III. In both years, contour cultivation plus straw mulch significantly reduced soil temperature. However, this did not result in yield reductions in comparison with the control. There was an increase in soil moisture content under contour cultivation plus straw mulch during dry periods, which was particularly noticeable in 1999. In 1998, there were no significant treatment effects on grain or shoot yield. In 1999, on Slope II, contour cultivation plus straw mulch significantly increased grain yield by 50.3% compared with the downslope treatment (P <0.05). In 1999, contour cultivation plus straw mulch also significantly increased leaf plus stem yield on Slopes I and II by 12.4 and 36.8%, respectively. It is concluded that on ≤10° slopes, contour cultivation alone is a suitable soil conservation measure. However, use of straw mulch would benefit soil moisture and nutrient status and could, therefore, increase crop yield. On ≥27° slopes, it is recommended that contour cultivation plus straw mulch be used as a soil conservation measure to ensure maximum soil conservation, even in extreme rainfall conditions.

Field experiments were conducted on an Alfisol in the semi-arid tropics of northern Australia to investigate nitrogen (N) cycling in the leucaena (Leucaena leucocephala) alley cropping system. This is a farming system in which maize (Zea mays L.) is grown in alleys formed by leucaena hedgerows spaced 4.5 metres apart. Mineralization of N from Ieucaena (prunings) and maize residues was studied under field conditions. Response of maize growth to addition of N fertilizer and plant residues was evaluated both in field plot and microplot experiments. The fate of fertilizer N and leucaena N was examined over four consecutive seasons. The decomposition (loss of mass) of dry, cut 15N-labelled leucaena residues differed from that of intact fresh leucaena prunings in the first cropping season although no difference was detected after one year. At the end of one cropping season, 3 months after application, 58-72% of 15N-labelled leucaena had decomposed compared to only 34-36% of fresh leucaena prunings. Similar trends occurred at 20 and 52 days after application. The extent of decomposition of fresh leucaena prunings (28-33%) was similar at two loading rates (2.4 and 4.7 t DM ha -1) by 3 months after addition. About 72% of young 15N labelled maize residues was decomposed by 3 months after addition in the presence of fresh leucaena prunings. Decomposition of 15N-labelled leucaena residues and unlabelled fresh prunings was 91% and 88% respectively 14 months after addition. After 2 years the corresponding values were 96% and 94%. When N content of the recovered residues was taken into account, the values were 95% and 94% after 14 months, and the same (97%) after 2 years. Maize yield and N uptake were significantly increased following addition of either unlabelled fresh leucaena residues or 15N-labelled thy Ieucaena residues. Application of N ferilizer produced a thither increase in the presence of the residues. The maize yield and N uptake with the 15N-labelled leucaena were not different from those with the unlabelled residues. There was a significant positive interaction between N fertilizer and leucaena prunings which increased maize production. Addition of maize residues decreased the yield and N uptake of maize compared with that obtained in the presence of N fertilizer at 40 kg N ha~1 and leucaena residues (2.4 t DM ha-1). There was a marked residual benefit of N fertilizer applied in the first season at 36 kgN hat in the presence of leucaena prunings on the second maize crop yield and N uptake, but not on the third crop. However, a significant residual benefit of leucaena prunings added in the first season was found in DM yield and N uptake of the second and third maize crop. The short-term fate of 15N applied in plant residues was examined during two separate cropping seasons. By 20 days after application of separate 15N-labelled leucaena leaves, stems and petioles, 3-9% of the added 15N could be found in maize plants, 33-49% was in surface residues, 36-48% in the 2 m soil proffle and 0.3-22% unaccounted for. In a separate experiment when leucaena components were not separated, 5% of 15N applied in leucaena residues was taken up by maize 52 days after addition, 45% was in residues, 25% was in soil and 25% was unaccounted for. Jn another experiment, maize recovered 6% of added leucaena 15N after 2 months, 39% remained in residues, 28% was in soil and 27% was not recovered. Incorporation of 15N-labelled leucaena residues in the soil did not increase recoveiy of leucaena 15N by maize compared with placement of the residues on the soil surface. By the end of one cropping season (3 months after application), 9% of added 15N was recovered by maize from 15N-labelled leucaena. There was a similar 15N recoveiy from 15N-labelled maize residues applied as mulch at 1.7 t DM ha1 together with unlabelled leucaena prunings at 2.4 t DM ha ~. In both cases, 30-32% of added 15N was detected in soil, 28% in residues, and 31-34% apparently lost. The short-term fate of fertilizer 15N was different from that of 15N added in plant residues. In a 52-day experiment, maize recovered 65-79% of fertilizer 15N applied at low rates (6.1 and 12.2 kg N ha -1) in the presence of leucaena prunings, 21-34% was present in soil, and less than 1% was not recovered. By 2 months after application, recoveiy of fertilizer 15N by maize was 41% from N fertilizer added at 80 kg N ha -1, 35% from N fertilizer at 40 kg N ha -1 in the presence of leucaena prunings, and 24% from N fertilizer at 40 kg N ha -1 in the presence of maize residues and leucaena prunings. The corresponding deficits (unaccounted-for 15N) were 37%, 38% and 47% respectively. A small but significant amount of the fertilizer 15N was present in the unlabelled leucaena residues (3%) and in the mixture of unlabelled leucaena and maize residues (7%) present on the soil surface. However, application of the plant residues did not affect recoveiy of the fertilizer 15N in soil (21-24%). When N fertilizer was applied at 40 kg N hi1 in the presence of leucaena prunings, 43% of fertilizer 15N was recovered by maize at the end of cropping season, 20% in soil, 2% in residues, and 35% unaccounted for. The long-term fate of fertilizer 15N was compared with that of leucaena 15N in an experiment over four cropping seasons. In the first season, maize tops recovered 50% of the fertilizer 15N but only 4% of the leucaena 15N. In the second, third and fourth seasons, maize (tops + roots) recovered 0.7%, 0.4% and 0.3% of the initial fertilizer 15N compared with 2.6%, 1.8% and 1.4% of the initial leucaena 15N. In the second, third and fourth seasons, recovery of the initial fertilizer 15N (12-14%) in soil was much lower than that of the initial leucaena 15N (38-40%). There was no further loss of the fertilizer 15N after the first season. However, the cumulative 15N deficit for the leucaena 1N in the first two seasons was 50%--thissuggested an additional loss of 23% since the end of the first season. There was no further loss of 15N from either residual fertilizer 15N or residual leucaena 15N in the third and fourth seasons. In conclusion, application of leucaena prunings could substantially increase maize yield and N uptake although some supplementary N fertilizer may be required to achieve maximum crop yield. Maize recovered only a small amount of added leucaena N in the first year. Most of the leucaena residue N was present in the soil and remaining residues after one season. This residue N would be gradually available for plant uptake by subsequent crops. Of course, annual additions of leucaena prunings would appreciably increase the pool of available N over time. Thus, application of leucaena prunings could substantially improve soil fertility in the long term.

Made available in DSpace on 2014-06-11T19:33:37Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-02-05Bitstream added on 2014-06-13T20:45:30Z : No. of bitstreams: 1 cazetta_da_dr_jabo.pdf: 537560 bytes, checksum: 1d9d7ab4cc189b5b27c53c296f415bad (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O N é o nutriente exigido em maior quantidade pela cultura do milho, influenciando nas características fenológicas, produtivas e na qualidade de grãos. Para avaliar a influência de épocas de aplicação do N sobre as características agronômicas e de eficiência de uso do nutriente na cultura do milho, o presente trabalho foi desenvolvido nos anos agrícolas 2006/2007 e 2007/2008, em dois ambientes de produção (Jaboticabal – em solo do tipo Latossolo e Itápolis – em solo do tipo Argissolo) no sistema de plantio direto em consolidação, utilizando o delineamento experimental em blocos ao acaso, constituídos por vinte e dois tratamentos, com quatro repetições. Cada parcela foi representada por oito linhas com 6,0 m de comprimento, considerando-se como área útil as quatro linhas centrais, desprezando-se um metro em ambas as extremidades. Concluiu-se que as características agronômicas, nutricionais e de eficiência de uso do N são influenciadas pelas épocas de aplicação de N e pelo ambiente, porém a aplicação de 120 kg ha-1 nos estádios de V4-V5 é superior em relação as demais, proporcionando também maior eficiência agronômica de uso do N; em ambiente de produção de Itápolis, as maiores produtividades são decorrência da aplicação parcelada de N na semeadura, no estádio V4-V5 e V10-V12 (30-60-30), ou pela aplicação total de N no estádio V4-V5; em ambiente de produção de Jaboticabal, as maiores produtividades são promovidas pelo parcelamento do N, como também pela aplicação total do N na semeadura e no estádio V4-V5; a estimativa do teor de clorofila para diferenciar tratamentos de adubação nitrogenada deve ser feita no estádio V10-V11 do milho; o estudo de correlação é viável para o estudo da adubação nitrogenada no milho e serve como uma ferramenta para as demais observações / Nitrogen is the nutrient required in greatest quantity by the maize crop, influencing the phenological, yield and grain quality. To assess the influence of timing of N application on agronomic characteristics and use efficiency of nutrient use in maize, this work was developed in the years of 2006/2007 and 2007/2008, in two production environments (Jaboticabal - Oxisol soil type and Itápolis – Alfisol soil type) in no-tillage system in consolidation, using a randomized block design, consisting of twenty-two treatments with four replications. Each plot was represented by eight lines, with 6,0 m long, considering how useful the area four central lines, ignoring one meters at both ends. We conclude that the agronomic characteristics, nutritional and use efficiency of N are influenced by timing of N application and the environment, but the application of 120 kg ha-1 in stages V4-V5 is higher than in the other, also provide the highest agronomic use efficiency of N; in production environment Itápolis, the highest yields are due to split N application at sowing, at the stage V4-V5 and V10-V12 (30-60-30), or the total application of N at V4-V5 stage; in production environment Jaboticabal, the highest yields are promoted by splitting N, as well as the application of total N at sowing and at stage V4-V5, the estimation of chlorophyll content to differentiate fertilization treatments should be done in the V10-V11 stage of maize, the correlation study is feasible for the study of nitrogen fertilization in maize and serves as a tool for other observations

The relationship between soil properties and micromorphological features was studied in six Alfisol and six Spodosol profiles from Southern Ontario. The total porosity of the soil material was largely related to the size, shape and conformation of the soil voids in thin sections, while the differential development of plasma fabric could be used to discern a sequence of degrees of weathering which was also expressed by various mineralogical and physico-chemical indices. The relative proportions of soil constituents in thin sections was successfully used to indicate the existing textural discontinuities in five of the profiles studied. The elementary structure of soil thin sections is considered the most important micromorphological feature in the investigation of the degree of B horizon development in both Alfisol and Spodosol profiles. / Thesis / Doctor of Philosophy (PhD)

Orientador: Domingos Fornasieri Filho / Banca: Aildson Pereira Duarte / Banca: Orivaldo Arf / Banca: José Carlos Barbosa / Banca: Leandro Borges Lemos. / Resumo: O N é o nutriente exigido em maior quantidade pela cultura do milho, influenciando nas características fenológicas, produtivas e na qualidade de grãos. Para avaliar a influência de épocas de aplicação do N sobre as características agronômicas e de eficiência de uso do nutriente na cultura do milho, o presente trabalho foi desenvolvido nos anos agrícolas 2006/2007 e 2007/2008, em dois ambientes de produção (Jaboticabal - em solo do tipo Latossolo e Itápolis - em solo do tipo Argissolo) no sistema de plantio direto em consolidação, utilizando o delineamento experimental em blocos ao acaso, constituídos por vinte e dois tratamentos, com quatro repetições. Cada parcela foi representada por oito linhas com 6,0 m de comprimento, considerando-se como área útil as quatro linhas centrais, desprezando-se um metro em ambas as extremidades. Concluiu-se que as características agronômicas, nutricionais e de eficiência de uso do N são influenciadas pelas épocas de aplicação de N e pelo ambiente, porém a aplicação de 120 kg ha-1 nos estádios de V4-V5 é superior em relação as demais, proporcionando também maior eficiência agronômica de uso do N; em ambiente de produção de Itápolis, as maiores produtividades são decorrência da aplicação parcelada de N na semeadura, no estádio V4-V5 e V10-V12 (30-60-30), ou pela aplicação total de N no estádio V4-V5; em ambiente de produção de Jaboticabal, as maiores produtividades são promovidas pelo parcelamento do N, como também pela aplicação total do N na semeadura e no estádio V4-V5; a estimativa do teor de clorofila para diferenciar tratamentos de adubação nitrogenada deve ser feita no estádio V10-V11 do milho; o estudo de correlação é viável para o estudo da adubação nitrogenada no milho e serve como uma ferramenta para as demais observações / Abstract: Nitrogen is the nutrient required in greatest quantity by the maize crop, influencing the phenological, yield and grain quality. To assess the influence of timing of N application on agronomic characteristics and use efficiency of nutrient use in maize, this work was developed in the years of 2006/2007 and 2007/2008, in two production environments (Jaboticabal - Oxisol soil type and Itápolis - Alfisol soil type) in no-tillage system in consolidation, using a randomized block design, consisting of twenty-two treatments with four replications. Each plot was represented by eight lines, with 6,0 m long, considering how useful the area four central lines, ignoring one meters at both ends. We conclude that the agronomic characteristics, nutritional and use efficiency of N are influenced by timing of N application and the environment, but the application of 120 kg ha-1 in stages V4-V5 is higher than in the other, also provide the highest agronomic use efficiency of N; in production environment Itápolis, the highest yields are due to split N application at sowing, at the stage V4-V5 and V10-V12 (30-60-30), or the total application of N at V4-V5 stage; in production environment Jaboticabal, the highest yields are promoted by splitting N, as well as the application of total N at sowing and at stage V4-V5, the estimation of chlorophyll content to differentiate fertilization treatments should be done in the V10-V11 stage of maize, the correlation study is feasible for the study of nitrogen fertilization in maize and serves as a tool for other observations / Doutor

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The soil management with emphasis in keeping soil residues on surface combined with vegetation growth may reduce carbon (C) emission to the atmosphere. The objective of this study is to measure the effects of the Eucaliptus Forest 20, 44 and 240 months old and native grassland on carbon sequestration in Paleudult, in Santa Maria, RS. The forest production was determined by Smalian method measuring selected trees, chosen from forest inventory based on standard deviation of breast height. The carbon of trees biomass was measured by weighting dry matter of leaves, branches, wood and cork and after converting to C by multiplying by 0.45. The C content in the forest litter, grassland, soil particulate and mineral associated organic matter in six soil layers were determined by CHNS auto analyzer. Soil physical properties as total, macro and microporosity, particle density and size distribution were determined and related to Eucaliptus and grassland. Soil samples were also used to measure some soil chemical properties. The dataset were tested to detect if there were normal distribution and variance homogeneity. To normal or transformed data, analysis of Variance and Tukey test (5%) for variables with significant F was applied. The greatest C stocks were in the wood and cork in all forest ages, however, the proportinal C in leaves and branches decreased with Eucalyptus age.The C stock in forest production added to grassland and litter dry matter increased with substitution of grassland by Eucalyptus Forest, and the difference increased with the age of trees. The content and stock of soil C are low and did not increase with introduction of forest on grassland soil. The soil layers with higher clay content had less C as compared to surface layers with lower clay content and higher C. The particulate organic matter varied the most with forest age and grassland indicating higher sensibility than organic matter associated with soil minerals. The introduction of forest on grassland did not change soil physical properties suggesting that more detailed studies should be done in order to better measure the impact of trees plantation. / O cultivo planejado e consciente do solo com a manutenção do resíduo em superfície e o crescimento equilibrado da vegetação pode amenizar a emissão de carbono (C) para a atmosfera. O objetivo do estudo é conhecer o efeito das florestas de eucalipto aos 20, 44 e 240 meses de idade e do campo nativo no estoque de C em Argissolo Vermelho Distrófico úmbrico, em Santa Maria, Rio Grande do Sul. A produção florestal foi determinada pela cubagem rigorosa por meio do método de Smalian de árvores-amostras selecionadas a partir do cálculo do desvio padrão do diâmetro à altura do peito, obtido por inventário florestal. A estimativa do C na biomassa arbórea foi determinada por pesagem da massa seca dos componentes folhas, galhos, madeira e casca das árvores-amostra, transformados em C considerando um fator de 0,45, conforme Wang et al. (2001). O C presente na serapilheira das florestas, na vegetação do campo nativo, no solo, em seis camadas distribuída em profundidade e nas frações da matéria orgânica particulada e associada a minerais foi determinado por meio de autoanalisador CHNS. As demais propriedades físicas do solo como a porosidade total, macro e microporosidade, densidade de partícula, foram também relacionadas ao efeito das florestas de eucalipto. A caracterização química do solo também foi realizada. Posteriormente à análise de distribuição normal dos dados bem como da homogeneidade de variância, cada variável foi submetida à análise de variância e comparação de médias pelo teste de Tukey, a 5% de probabilidade. Os maiores estoques de carbono estão no componente madeira e na casca independente da idade das florestas, tendendo à diminuição do percentual para os componentes galhos e folhas. A produção do material arbóreo florestal agregado ao material em decomposição, bem como o seu estoque de carbono, aumentam sobremaneira quando da substituição da vegetação nativa de campo para as florestas de eucalipto, adquirindo expressividade no decorrer do crescimento e desenvolvimento das florestas. O teor e estoque de carbono no solo são baixos, indicando que o crescimento das florestas de eucalipto em substituição à vegetação nativa de campo não agregou um aumento significativo, ao contrário das constatações no componente vegetal. As camadas com maior percentual de argila não refletem diferença na presença de C comparado às camadas mais arenosas, ou superficiais, com maior presença de material orgânico. A fração matéria orgânica particulada foi a mais sensível às variações de idade de povoamento e uso da área, e menor variação na fração associada aos minerais do solo devido a suas características de proteção. Para as propriedades físicas do solo, não se observaram variações significativas quando da substituição do campo nativo pelas florestas de eucalipto. Portanto, as proposições para estudos desta magnitude objetivando o mercado de carbono e das florestas como mecanismos de desenvolvimento limpo deverão ser fidedignamente avaliadas e monitoradas durante o crescimento das florestas.