MSCAGR (Soil Science) / Department of Soil Science / Accelerated soil erosion is a serious agricultural problem in South Africa limiting soil productivity and little it’s known about its effect on soil quality. This study aimed to provide a less laborious, less time consuming and inexpensive protocol of estimating the effects of accelerated erosion on the soil quality. An assessment was undertaken in sites showing threat of accelerated erosion using various direct physical soil quality indicators. Four sites with different soil types were identified at initial survey. In each of the sites, two areas were selected. These areas were then classified as Not Visibly Eroded (NVE) and Visibly Eroded (VE). Each measurement in all site was done in those area classified respectively. The most stable structure and consistency were observed in NVE areas. Medium and large stones were observed in VE areas in all soil types studied. The VE soils were lighter in colour compared to soil colour in NVE. Aggregate stability and moisture content were significantly higher for the NVE and VE areas. Difference in values of water stable aggregates between NVE and VE was clear which showed that stability of aggregates is important in determining soil susceptible to erosion. Bulk density values were slightly different for the two areas. However, there was no significant difference between the bulk density of NVE and VE. Differences between soil texture for NVE and VE areas are only apparent for the sand, clay and silt particles with no changes in textural class. For all soil types investigated, silt was vulnerable to accelerated erosion with respect to soil texture. The research has provided baseline protocol for using physical soil quality indicators to find out effects of accelerated erosion. Soil functionality is critical in the restoration process of soil quality, and the methods used here could be effectively applied in a broad range assessment of erosion impact. / NRF

Encouraging greater implementation of conservation agriculture practices such as reduced tillage and cover crops may require better understanding of the effect of these practices on soil health. The overall objective of this study was to quantify soil health dynamics due to conservation agriculture practices and address methodological gaps in terms of measuring soil health parameters. We developed five sites across the state of Virginia; each site had replicated plots with combinations of reduced tillage versus disk tillage and wintertime cover crops versus no cover crops as experimental treatments. Soil and plant samples were collected 1-2 times per year for 3 years, and were analyzed for 30 soil health parameters. The parameters were first evaluated to determine if any consistently detected treatment differences. We then quantified the temporal dynamics of the eight most responsive soil health parameters, while considering influences of soil water content at time of tillage, cover crop biomass, and previous land management history. Of the analyzed parameters, only 2-4 mm aggregate stability and magnesium showed high responsiveness and consistency in identifying tillage and cover crop effects. None of the parameters detected treatment differences in all sites or at all times, yet samples collected after high biomass cover crops or after tillage in wet conditions tended to show significant treatment differences for multiple indicators. The previous history of management in each site may have affected trends in aggregate stability, but did not appear to influence other indicators. As soil aggregate stability was found to be the most important soil health parameter, our third study developed an improved method for measuring soil aggregate stability. This new method, Integrated Aggregate Stability (IAS), interprets aggregate stability using a laser diffraction machine. Overall, IAS showed higher correlation with the wet sieving method (R2 = 0.49 to 0.59) than widely used median aggregate size (d50) (R2 = 0.09 to 0.27). IAS can also quantify stability of macro- and micro-sized aggregates, which d50 cannot. When comparing between IAS and wet sieving, IAS requires considerably less time and sample amounts. Our fourth study focused on creating an inexpensive yet accurate tool for measuring soil respiration, as microbial assessments based on respiration rates have great potential for detecting rapid changes in soil health. Using an Arduino-based infrared gas analyzer (IRGA) sensor, we developed the Soil Microbial Activity Assessment Contraption (SMAAC) for less than $150. Our results show that SMAAC provided consistent readings with a commercial IRGA unit when tested using three different configurations. Altogether, the research presented in this dissertation identifies important soil health parameters and quantifies their temporal and between-site dynamics. Using this narrower set of indicators can help producers and practitioners save resources when conducting measurements to assess soil health effects of agricultural practices. Further, this work also provides improved measurement techniques for useful soil health parameters like aggregate stability and soil respiration. These findings and innovations should help to encourage greater adoption of agricultural management practices that build and preserve soil health. / Doctor of Philosophy / If we want to make sure that ample and safe food is available to future generations, then it is time that we produce food without damaging the soil. Many widely used soil management techniques like tillage and leaving the field bare can harm the soil and decrease productivity in the long run. One potential technique to produce food while protecting the soil and environment is conservation agriculture, which can include reduced tillage and cover cropping. Reduced tillage is a technique in which we grow food without majorly disturbing the soil, while cover crops are planted when cash crops are not in the field in order to improve or sustain the soil. Understanding the soil-related benefits of conservation agriculture practices is important to encourage farmers to adopt these practices. In this study we tested the effects on soils of reduced tillage and cover crop practices versus conventional tillage and bare soil practices, using five locations across Virginia. We also developed improved methods for measuring two informative soil parameters. We found that, when looking at all of our five sites, the stability of soil aggregates, the rate at which water enters soil, and the nutrients in surface soils were all affected by the type of management that the soils were subjected to. Reduced tillage increased stability of soil aggregates when compared with conventional till. This increased stability of aggregates indicators lower potential for surface water runoff, erosion, and flooding when we practice reduced tillage. Cover cropping also increased stability of soil aggregates, especially when the cover crops attained substantial above-ground mass. Soil nutrients (which are essential for plants to grow) were also overall higher in the surface soil layers under no-till. Since the stability of soil aggregates was found to be an important benefit of CA practices, we also perceived a need for a better method for measuring stability of these aggregates. In response, we developed a new index called Integrated Aggregate Stability (IAS). IAS was found to give similar results as established methods, but the time required to get IAS result is about 10 minutes, whereas the time required for established methods like wet sieving is around 2 days. IAS measurements are therefore both accurate and quick to perform. We also focused on developing an inexpensive tool for measuring soil respiration. Soil respiration-based measurements help us to understand the activity of microbes in the soil. These microbes are very important for soils to function. Our tool, Soil Microbial Activity Assessment Contraption (SMAAC), was very consistent with a currently used tool and shows high potential for future use. Altogether, we found that no-tillage and cover cropping can increase stability of soil aggregates even within 1-3 years of starting those practices. No-till can also increase nutrient concentrations in the top soil layer. The tools and innovations developed in this study have the potential to increase the ability of farmers to assess soil health and also encourage greater adoption of conservation agriculture practices.

Master of Science / Department of Agronomy / Walt Fick / Prescribed burning has been a common conservation practice on native prairie dating back to the days of pioneer settlement. Advantages include increased forage quality, reduction of undesirable plants, improved wildlife habitat, removal of accumulated dead plant litter and relatively low costs. While spring is the commonly accepted time to burn, little research has been conducted on late-summer and fall burning for specific objectives that include targeting undesirable plant species and measuring potential effects on soil physical properties. The first part of this study was to evaluate the effect that prescribed burning has on population dynamics of sericea lespedeza (Lespedeza cuneata [Dumont] G. Don), rough-leaf dogwood (Cornus drummondii Meyer), and additional woody species. Stem counts and cover estimates were taken from 20, 0.25-m[superscript]2 frames prior to and post-burn. Change in botanical composition, plant density, frequency, and Daubenmire canopy cover estimates were calculated. Sericea lespedeza plant frequency across all clay upland burns decreased 2.27% and increased 4.76% across all loamy/limy upland burns the first growing season post-burn. Dogwood densities increased 3.12 stems m[superscript]-[superscript]2 on spring burns compared to a decrease of 0.30 stems m[superscript]-[superscript]2 on unburned plots the first growing season post-burn. Changes in frequency of other woody species the first growing season post-burn showed significant interactions between burn treatment and ecological site, and between ecological site and year. A significant interaction between burn treatment and ecological site was found on total woody species plant composition changes two growing seasons post-burn for the first year of burn treatments. The secondary part of this study was to evaluate the effect of prescribed burning on soil bulk density and wet-aggregate stability. Soil samples were collected along the same line-transects used for vegetation sampling. Significant differences among mean weight diameters (MWD), percent water-stable aggregates (WSA), and WSA size fractions occurred between burned and unburned soils following burning in the fall of 2011. Monitoring plant and soil response to prescribed burning in different seasons may lead to adjustments being made in management of rangelands where sericea lespedeza, dogwood, and additional woody species occur.

Made available in DSpace on 2017-07-25T19:30:58Z (GMT). No. of bitstreams: 1 Daiani Cruz Hartman.pdf: 1884563 bytes, checksum: e16a5b42a86658f86cfd68e490069ec0 (MD5) Previous issue date: 2016-04-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The soil organic matter (SOM) perform an important role in the agriculture sustainability, and depending of the management system used, the soil can behave as a source or drainage of carbon (C) to the atmosphere. The objective of this study was to comprehend the impact of the use of phosphorous (P) sources in the soil organic carbon (SOC) pools and in the soil aggregation, managed in the crop-livestock integration system (CLIS), in no-till, adopting as a reference the native vegetation. The experiment design was completely randomized blocks in factorial 2x3, with four replicates. The experiment was established in April 2009 with five treatments: (i) control: without P application; (ii) TSP60: application of 60 kg ha-1 in the form of triple superphosphate (TSP); (iii) TSP120: application of 120 kg ha-1 of P in the form of TSP; (iv) MTP60: application of 60 kg ha-1 of P in the form of magnesium thermophosphate (MTP); (v) MTP120: application of 120 kg ha-1 of P in the form of MTP. In addition, we used as a reference a nearby native vegetation area. The soil was sampled in march 2013, at the depths of 0-5, 5-10, 10-20 cm for aggregate analysis and 0-5, 5-10, 10-20, 20-40, 40-60, 60-80 and 8-100 cm for total organic carbon (TOC) analysis, total and labile polysaccharides (PT and PL), hot water extractable organic carbon (HWEOC), permanganate oxidizable organic carbon (POXC), pyrophosphate oxidizable organic carbon (PIOC), recalcitrant carbon (Crec), particulate organic carbon (POC) and mineral associated organic carbon (MAOC). The treatments with TSP promoted higher stocks in all the SOC labile pools at 0-100 layer. The treatment with TSP presented higher POC, HWEOC and POXC stocks, which was 22.65 and 22.53; 21.99 and 22.49; 4.98 and 4.85 Mg ha-1, respectively, for TSP60 and TSP120, respectively at 0-100 cm layer. The extra-large macroaggregate class (8-19 mm) at the depth of 0-20 cm presented the highest TOC stocks regarding the other aggregate classes and the TSP at the rate of 60 kg ha-1 promoted the highest TOC stock. The C sequestration rate estimated by the unicompartimental model of C balance was 10 times higher in the 8-19 aggregate class at the depth of 0-20 regarding the 0.053-0.25 mm aggregate class. The C sequestration rate for the treatments control, TSP60, TSP120 MTP60 and MTP120 were 0.82, 1.06, 1.14, 1.09 and 1.06 Mg ha-1, respectively. The minimum amount of crop residue necessary to maintain the carbon balance for the treatments control, TSP60, TSP120 MTP60 and MTP120 respectively were from 6.98, 8.17, 7.93, 7.98 and 8.0 Mg ha-1 to 0.32, 0.23, 0.27, 0.20 and 0.22 Mg ha-1, in the 2-19 and 0.25-0.053 classes, respectively. The phosphate fertilization with soluble source in no-till in CLIS in short-term promoted higher benefits to soil structure and higher C stock in the SOC pools and in the aggregates, than the partial soluble source, indicating higher potential in reverting the soil degradation process. / A matéria orgânica do solo (MOS) desempenha um papel importante, na sustentabilidade agrícola e dependendo do manejo adotado o solo pode atuar como fonte ou dreno de Carbono (C) para a atmosfera. O objetivo deste trabalho foi compreender o impacto do uso de fontes de fósforo, nos compartimentos de Carbono orgânico e na agregação do solo, manejado no sistema integrado de produção agropecuária (SIPA), em plantio direto (PD), tendo como referência a vegetação nativa (VN). O experimento foi realizado em um Cambissolo Háplico argiloso no município de Castro, PR. O delineamento experimental foi o de blocos aleatorizados, em arranjo fatorial (2X3), com quatro repetições. O experimento foi implantado em abril de 2009 e constitui-se de 5 tratamentos: (i) Controle – sem aplicação de P; (ii) SFT60 - aplicação de 60 kg ha-1 de P2O5 na forma de superfosfato triplo (SFT); (iii) SFT120 – aplicação de120 kg ha-1 de P2O5 na forma de SFT; (iv) TFM60 - aplicação de 60 kg ha-1 de P2O5 na forma de termofosfato magnesiano (TFM); (v) TFM120 –aplicação de 120 kg ha-1 de P2O5 na forma de TFM, também, foi adicionado como tratamento o solo sob VN adjacente ao experimento, caracterizando a referência. O solo foi coletado em março de 2013, nas profundidades 0-5, 5-10, 10-20 cm para análise de agregados e 0-5, 5-10, -10-20, 20-40, 40-60, 60-80 e 80-100 cm para análise de C orgânico total (COT), C organico particulado (COP) e C associado aos minerais, C extraído por água quente (CAQ), C oxidado por permanganato de potássio (COXP), C extraído por pirofosfato de sódio (CPIR), polissacarídeos totais e lábeis (PT e PL respectivamente), e C recalcitrante (Crec), compreendendo os compartimentos do C. Os tratamentos com SFT promoveram estoque superior nos compartimentos lábeis na camada de 0-100 cm. Os tratamentos com fonte SFT resultaram em maior estoque de COP, CAQ e COXP que foi de 22,65 e 22,53; 21,99 e 22,49; 4,98 e 4,85 Mg ha-1, respectivamente, para o SFT60 e SFT120, respectivamente na camada de 0-100 cm. A classe de macroagregado extra-grande (8-19 mm) na camada de 0-20 cm constituiu-se no maior estoque de COT em relação as demais classes de agregados e o tratamento com SFT na dose de 60 kg ha-1 promoveu o maior estoque de COT. A taxa de sequestro de C estimada pelo modelo unicompartimental de balanço de C foi de quase 10 vezes superior na classe de macroagregados (8-19 mm) na camada de 0-20 cm em relação a classe de microagregados (0,053- 0,25 mm). A taxa de de sequestro de C para os tratamentos Controle, SFT60, SFT120 TFM60 e TFM120 foi de 0,82, 1,06, 1,14, 1,09 e 1,06 Mg ha-1ano-1, respectivamente. A quantidade mínima de resíduos culturais na forma de palhada para manter o balanço de C em equilíbrio estável para os tratamentos Controle, SFT60, SFT120, TFM60 e TFM120 foi de 6,98, 8,17, 7,93, 7,98 e 8,03 Mg ha-1 e 0,32, 0,23, 0,27, 0,20 e 0,22 Mg ha-1, respectivamente, nas classes 2-19 e 0,25-0,053 mm, respectivamente, A adubação fosfatada com fonte solúvel em PD em experimento sob SIPA de curto prazo, promoveu maiores benefícios à estruturação do solo e maior estoque de C nos compartimentos de C e nos agregados, do que a fonte parcialmente solúvel, indicando maior potencial em reverter o processo de degradação da qualidade do solo.

Agronomijos studijų programos magistro baigiamasis darbas 40 puslapių, 10 paveikslų, 2 lentelės, lietuvių kalba. Tyrimo objektas: paprastojo miežio (Hordeum vulgare L.) vasarinės veislės ,,Simba'' agrocenozė. Tyrimo tikslas: Įvertinti ilgalaikio skirtingo intensyvumo žemės dirbimo poveikį miežių agrocenozei, taikant intensyvias technologijas. Tyrimo uždaviniai: 1. Apžvelgti mokslinę literatūrą ir atlikti sisteminę analizę tiriamuoju klausimu. 2. Aprašyti atlikto eksperimento vykdymo sąlygas ir metodus. 3. Tyrimais nustatyti ir įvertinti ilgalaikio skirtingo intensyvumo žemės dirbimo poveikį struktūros patvarumui, miežių sudygimui, pasėlių piktžolėtumui ir miežių produktyvumui. Tyrimo metodai: mokslinės literatūros apžvalga, loginė analizė ir sintezė, statistinė analizė, palyginamoji analizė, grafinio modeliavimo technikos. Tyrimo rezultatai: • Pirmoji dalis pristato Lietuvos ir užsienio autorių mokslinės literatūros analizę. Mokslinė medžiaga atrinkta, susisteminta ir analizuota. • Antroje dalyje aprašyti koncentruojamasi ties bandymo schema ir parametrais, mokslinio eksperimento variantais ir duomenų analizės stebėjimais ir metodais. • Trečioji dalis identifikuoja dirvožemio struktūros patvarumą, miežių sudygimą ir stiebų produktyvumą, miežių derlių, pasėlių piktžolėtumą bei miežių produktyvumą. Nustatyta, kad ilgalaikis skirtingo intensyvumo žemės dirbimas neturėjo esminės įtakos dirvožemio struktūros patvarumui. Nenustatyta esminės įtakos ir miežių produktyvumui... [toliau žr. visą tekstą] / Final work of University Undergraduate/Master Studies 47 pages, 9 figures, 2 tables, the Lithuanian language. Object of the research: barley (Hordeum vulgare L.) spring variety Simba'' agrocenoses. Aim of the research: to evaluate the long-term effect of different soil tillage intensity on barley agrocenosis applying intensive technologies. Objectives of the research: 1. Review of the literature and perform a systematic analysis of the relevant issue. 2. Describe an experiment carried out with the conditions and methods. 3. Studies to identify and evaluate the long-term differences in the intensity of tillage effects on structural stability, barley germination, weed infestation and barley productivity. Research methods: review of scientific literature logical analysis and synthesis, statistical analysis, comparative analysis, graphical modelling techniques. Research results: • Part One presents Lithuanian and foreign scientific literature. Scientific material selected, structured and analysed. • Part Two describe the focus is on testing scheme and the parameters of the scientific variants of the experiment and data analysis methods and observations. • Part Three identifies the soil structure stability, barley germination and stem productivity of barley harvest, weed and barley crop productivity. It was established, that tillage intensity had no significant effect on soil aggregate stability and on barley productivity parameters except the number of germinating barley... [to full text]

Submitted by (lucia.rodrigues@ufrpe.br) on 2016-08-18T12:38:54Z No. of bitstreams: 1 Veronildo Souza de Oliveira.pdf: 823920 bytes, checksum: 0d97083c73532a03b76ed1dd705e5c3b (MD5) / Made available in DSpace on 2016-08-18T12:38:55Z (GMT). No. of bitstreams: 1 Veronildo Souza de Oliveira.pdf: 823920 bytes, checksum: 0d97083c73532a03b76ed1dd705e5c3b (MD5) Previous issue date: 2008-03-11 / The sugarcane cultivation requires an intensive use of agricultural machinery for tillage and crop procedures; however, compression effect on soil caused by passage of agricultural machinery has been little studied in the last years. Deformations due to continuous traffic of agricultural machinery and implements in association with inadequate managements have been observed to decrease the sustainability of agricultural soils, mainly because of alterations of some soil physical attributes which can make the soil more susceptible to compaction. The objective of this work was to evaluate the susceptibility to compaction of a Yellow Argissol submitted to three distinct managements of sugarcane cultivation and native forest, through aggregate stability and distribution, compaction and compressibility characteristics of the soil. Four distinct areas were investigated: a native forest (NF), an area cultivated with sugarcane without irrigation (ANI), an irrigated area (AWI), and an area irrigated with vinasse (AIV). Soil samples were collected randomly, in 50.00×50.00m-area, at depths ranging from 0 to 20 cm, 20 to 40 cm, and 40 to 60 cm. For assessment of aggregate stability and distribution it was evaluated total organic carbon (TOC) content, wet aggregate stability, aggregate stability index (ASI), module of thinness (MT), and percentage of aggregates larger than 2.0 mm stable in water (AGRI). For compaction analyses, undeformed soil samples were collected with metallic rings and were used for the determination of soil density. Deformed samples were used for the determination of organic matter content and the performance of Standard Proctor tests. Regarding the compressibility analyses, a trench was dug in the four selected areas and four underformed samples were collected in each depth. The samples were collected using metallic rings with 6.4 cm in diameter and 2.5 cm in height, at 0-20, 20-40 cm, with four replicates. In laboratory, the samples were previously saturated and submitted to soil suctions raging from 0.1 to 1500. Confined compression tests were performed with the saturated samples. Data were submitted to variance analysis and the differences among means were compared using the Tukey test at 5% of probability. In all areas, the results pointed out decrease in aggregate stability as the soil depth increased for classes higherthan 2.0 mm. The aggregation indexes of the cultivated areas were comparatively smaller than that of the native forest following the sequence NF>AIV>AWI >AWI. The management AWI showed the smallest aggregation indexes and AIV was the most close to NF. Significant and positive correlations occurred between The management that more closely approached the native forest conditions was the vinasse management (MWV), which showed better aggregate stability under water. Significant and positive correlations were obtained between TOC and stability indexes studied. Data of maximum capacity of soil compaction followed the crescent order of compaction susceptibility ANI>AWI>AIV>NF, and the critical humidity the inverse order. A regression analysis for pre-consolidation stress in function of water content (Ug) and correlations among the several variables were carried out. In all investigated areas, the depth of 0 to 20 cm showed to be more susceptible to compaction than 20 to 40 cm; the AIV management modified the compressive behavior of the soil in both depth ranges (0-20 and 20-40 cm); and the load support capacity of the soil was larger in the depth of 20 to 40 cm. / O cultivo da cana-de-açúcar requer um intensivo uso de máquinas agrícolas desde a realização do preparo do solo até as operações de colheita, no entanto, o efeito de compressão sofrida pelo solo durante a passagem do maquinário agrícola tem sido pouco pesquisado nos últimos anos. As deformações decorrentes do tráfego de máquinas e implementos agrícolas aliados a manejos inadequados vêm comprometendo a sustentabilidade dos solos agrícolas, principalmente pelas modificações de alguns atributos físicos que podem contribuir com a sua compactação. O objetivo deste trabalho foi estudar a susceptibilidade à compactação de um Argissolo Amarelo distrocoeso, submetido a três diferentes manejos, sob cultivo de cana-de-açúcar e mata nativa, através do estudo da estabilidade e distribuição dos agregados; da compactação; e do comportamento compressivo dos solos. Assim, foram avaliadas quatro áreas sendo: mata nativa (MA), manejo sem irrigação (MSI), manejo com irrigação (MCI), e manejo com fertirrigação de vinhaça (MCV). Para a realização dos ensaios foram coletadas amostras de solo nos locais sorteados, 50,00 x 50,00 m, nas quatro áreas nas profundidades de 0-20, 20-40 e 40-60 cm. No estudo da estabilidade e distribuição dos agregados foi analisado o carbono orgânico total (COT) e determinando a estabilidade de agregados por via úmida, expressa por quatro índices: diâmetro médio ponderado (DMP), índice de estabilidade de agregados (IEA), módulo de finura (MF) e da porcentagem de agregados maiores que 2,0 mm estáveis em água (AGRI). Na determinação da densidade do solo, amostras indeformadas foram retiradas por meio de anel; e deformada na determinação da densidade máxima (Dsmax) e da umidade crítica (Uc) de compactação, através do ensaio de Proctor normal; além da determinação do grau de compactação. No caso especifico da compressibilidade, quatro trincheiras foram abertas nos locais sorteados das quatro áreas de estudo e retiradas amostras indeformadas com auxílio de anéis metálicos de 6,4 cm diâmetro e 2,5 cm de altura nas profundidades de 0-20, 20-40 cm, com quatro repetições. As amostras após coletadas foram saturadas e submetidas a sucções de 0,1 a 10 kPa e 50, 500 e 1500 kPalevadas a prensa mecânica e realizado o ensaio de compressibilidade. Todos os dados foram submetidos à análise de variância e as diferenças entre médias comparadas pelo teste de Tukey, a 5% de probabilidade. Em todos os manejos, houve diminuição da estabilidade de agregados com o aumento da profundidade, para as classes superiores a 2,0 mm. Os tratamentos cultivados tiveram seus índices de agregação reduzidos em relação à mata nativa na seguinte seqüência: MA>MCV>MCI>MSI. O sistema MSI apresentou os menores índices de agregação e o MCV o mais próximo da condição de mata. Correlações significativas e positivas foram obtidas entre COT e os índices de estabilidade estudados. Os valores das densidades máximas de compactação do solo obedeceram a seguinte ordem crescente de susceptibilidade à compactação: MSI>MCI>MCV>MA, enquanto a umidade crítica o inverso. Análise de regressão para a variável tensão de pré-consolidação em função da umidade gravimétrica (Ug) além de correlações entre as diversas variáveis foram realizadas. A profundidade de 0-20 cm, em todos os casos, mostrou ser a mais susceptível à compactação em relação à profundidade de 20-40 cm; o manejo MCV alterou o comportamento compressivo do solo em ambas as profundidades (0-20 e 20-40 cm); e que a capacidade de suporte de carga do solo foi maior em todos os manejos nas camadas de20-40 cm.

Submitted by (lucia.rodrigues@ufrpe.br) on 2016-10-13T11:39:44Z No. of bitstreams: 1 Ricardo Rafael Andrade de Vasconcelos.pdf: 933968 bytes, checksum: 226d9d7819e34ad7946ec555c3a74882 (MD5) / Made available in DSpace on 2016-10-13T11:39:44Z (GMT). No. of bitstreams: 1 Ricardo Rafael Andrade de Vasconcelos.pdf: 933968 bytes, checksum: 226d9d7819e34ad7946ec555c3a74882 (MD5) Previous issue date: 2012-09-28 / The present study had as objective to evaluate the effectiveness of applying different levels of gypsum on saline-sodic soil reclamation and its influence on physical-chemical newly corrected soil characteristics by the gypsum application. The laboratory experiment used PVC columns. The treatments were done in a randomized factorial arrangement block of 2x5 (two soil x five level gypsum of requirement), with five replicates. The levels used were equivalent to 50, 100, 150, 200 and 250 % of gypsum requirement, determined by the modified method Schoonover (Schoonover M-1), incorporated at the first 12,5 cm column of soil. The leachate electrical conductivity (EC), soluble cations and pH were evaluated. In soils were determinate the exchangeabled sodium and the exchangeable sodium percentage (ESP); The EC, soluble cations and sodium adsorption relation (SAR) in the saturation extract; the hydraulic conductivity, infiltration rate, the dispersed clay water and aggregate stability. The application level 100% of the need of plaster, obtained by the method of Schoonover M-1, followed by a water depth correspondent to three pore volumes afforded the correction of soil sodicity (SAR < 13 mmol L-1 and ESP < 15 %). The water depth correspondent to three times the pore volumes corrected salinity of soil was used when the levels of 50 and 100 % of gypsum requirement (EC < 4,0 dS m-1). The use of increasing levels of gypsum for the correction of saline-sodic soils provided greater water infiltration rate of the soil. The level of 100 % of the gypsum requirement in lower degree of dispersion and more stability of aggregates of soils. / O presente trabalho teve como objetivo avaliar a eficiência da aplicação de diferentes níveis de gesso, na recuperação de solos salino-sódicos e sua influência nas características físico-químicas de solos recém corrigidos pela aplicação de gesso. O experimento foi realizado em laboratório, utilizando colunas de PVC. Os tratamentos foram dispostos em delineamento em blocos casualizados com arranjo fatorial de 2 x 5 (dois solos x cinco níveis da necessidade de gesso), com cinco repetições. Os níveis utilizados foram equivalentes a 50, 100, 150, 200 e 250% da necessidade de gesso, determinada pelo método de Schoonover modificado (Schoonover M-1), incorporados aos primeiros 12,5 cm da coluna de solo. Foram avaliados nos lixiviados a condutividade elétrica (CE); os cátions solúveis e o pH. Nos solos foram determinados o sódio trocável e a percentagem de sódio trocável (PST); a CE; os cátions solúveis e a relação de adsorção de sódio (RAS) no extrato da pasta saturada; a condutividade hidráulica; a taxa de infiltração; grua de dispersão e a estabilidade de agregados. A aplicação do nível de 100% da necessidade de gesso, obtido pelo método de Schoonover M-1, seguida de uma lâmina de lixiviação correspondente a três vezes o volume de poros, proporcionou a correção da sodicidade dos solos (RAS < 13 mmolc L-1 e PST < 15%). A lâmina de lixiviação correspondente a três vezes o volume de poros corrigiu a salinidade dos solos quando foram utilizados os níveis de 50 e 100% da necessidade de gesso (CE < 4,0 dS m-1). A utilização de níveis crescentes de gesso para a correção de solos salino-sódicos proporcionaram maior taxa de infiltração de água dos solos. O nível de 100% da necessidade de gesso promoveu menor grau de dispersão e maior estabilidade de agregados dos solos estudados.

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O desenvolvimento econômico brasileiro depende da crescente produção agropecuária, aliada ao conservacionismo. O sistema de plantio direto é o manejo de solo que reúne o mais amplo conjunto de preceitos da agricultura conservacionista. As áreas agrícolas cultivadas sob plantio direto, entretanto, têm apresentado duas camadas de solo distintas: uma entre, aproximadamente, 0 e 7 cm de profundidade, com condições físicas e químicas favoráveis ao desenvolvimento radicular; e uma entre, aproximadamente, 7 e 20 cm de profundidade, com menor permeabilidade do solo ao ar e a água, elevada resistência à penetração e baixa fertilidade química do solo. Estas condições promovem a concentração do sistema radicular das plantas agrícolas cultivadas na camada mais superficial do solo (0 a 7 cm), motivando perdas de produtividade por estresse hídrico. A magnitude desse problema se estende a mais de 30 milhões de hectares de lavoura cultivada sob plantio direto no Brasil, colocando em risco as projeções de exuberância da agricultura no país. Assim, o desenvolvimento desta tese teve o objetivo de estudar fatores que, além do processo de compactação mecânica do solo, possam estar promovendo a estratificação física e química de solos altamente intemperizados cultivados sob sistema de plantio direto. Dentre os possíveis fatores causadores deste tipo de degradação, foram avaliados: i) a aplicação excessiva de calcário, exclusivamente em superfície, ocasionando, na camada de 0 a 7 cm, a elevação do pH do solo para além do ponto de carga zero do solo, elevando o potencial eletronegativo do solo e por consequência, promovendo a dispersão de argila; ii) a migração da argila dispersa no perfil do solo, pela água de percolação, como um fator promotor de degradação física em subsuperfície; iii) o aporte de fitomassa ao solo em quantidade e qualidade para manter a estabilidade estrutural dos solos cultivados. Os resultados obtidos mostraram que o movimento de calcário no perfil dos solos estudados é muito lento, limitando o efeito deste produto a poucos centímetros abaixo do local onde ele é depositado ou incorporado (2,5 cm em 130 semanas), independentemente da dose aplicada (até 33,2 Mg ha-1). Assim, a calagem superficial promove e intensifica a estratificação dos atributos químicos no perfil do solo, aumentando, demasiadamente, o pH próximo à superfície e sendo ineficiente em mitigar a acidez na subsuperficie destes solos. A concentração de calcário na camada mais superficial dos solos altamente intemperizados aumenta a eletronegatividade do solo, resultando na dispersão de argila. A migração dos argilominerais dispersos no perfil do solo, pela água de percolação, promove uma série de alterações estruturais, incluindo a diminuição da porosidade total e da continuidade dos poros e o aumento da densidade e da resistência do solo à penetração na camada subsuperficial. A diminuição da estabilidade estrutural dos Latossolos sob cultivo também está ligada ao aporte de material orgânico ao solo em quantidade e qualidade inferiores à que ocorre no solo sob sistema nativo. Os Latossolos cauliníticos são mais propensos a diminuição da estabilidade estrutural quando submetidos ao cultivo. Portanto, a recomendação de calagem em solos altamente intemperizados cultivados sob plantio direto, precisa considerar a mineralogia do solo e a possível degradação estrutural promovida pela calagem em excesso. / The economic development of Brazil depends upon the increasing agricultural production associated with conservation practices. The no-tillage system is the soil management practice that brings together the broadest set of principles for conservation agriculture. Areas under no-till system, however, generally have two completely different soils layers: a surface layer, around 0 to 7 cm, with physical and chemical conditions favorable for root development; and a sub-surface layer, around 7 to 20 cm, with lower permeability to air and water, high soil penetration resistance, and low soil fertility. The existence of these stratified layers dramatically restricts the development of the root system into the sub-surface soil layer, which may result in reducing plant productivity by water deficit. This problem exists on more than 30 million hectares cultivated under no-tillage system in Brazil, and can compromise the optimistic projections of agricultural growth in the country. Therefore, more research is necessary to explore challenges that come with no-tillage. The aim of this thesis was to study the factors that can promote the physical and chemical stratification of highly weathered soils cultivated under no-till system. Among the factors that could cause this degradation, the following were studied: i) the application of excessive lime only on surface soil, or into the uppermost soil layer, which can increase its pH to levels beyond of the zero point of charge of soil, raising its electronegative potential and promoting, as a consequence, the clay dispersion; ii) the dispersed clay migration thtough the soil profile, by the percolation water, as a factor of physical degradation of sub-surface of soil cultiveted under no-tillage; and iii) the aplication of phytomass to the soil in insufficient amount and quality to maintain the soil structural stability of the soil. The results of this study showed that lime movement into the deeper soil profile, is very slow, as its impacts are limited to just a few centimeters below of where it is applied or incorporated (2.5 cm after 130 weeks), independent of the applied amount of lime. Thus, the surface lime application intensifies the chemical stratification of the clayey soils under no-tillage, increasing to much the soil pH of the uppermost soil layer, and being inefficient to decrease the soil acidity in the subsurface soil layer. The concentration of lime into the uppermost soil layer can significantly increase the electronegativity of the soil system and result in clay dispersion in the topsoil layer (0 to 5 cm). The resulting clay migration into the soil profile led to a series of structural alterations in subsurface layers, including: decrease of both soil porosity and pore continuity; and increase of both soil bulk density and soil penetration resistance in the sub-superficial layer. The structural stability decreasing of Oxisols under no-till system also is linked with the low addition of organic matter to the cultivated soil, in relation to the non-cultivated soils. The kaolinitic Oxisols are more susceptible to degradation than the gibbsitic Oxisols. Thus, it could be conclude that liming practices (rate and application methods of lime), mainly under no-till systems, need to consider both type and mineralogy of soil, as well as considering soil structure degradation promoted by over-liming in the uppermost soil layer.

O desenvolvimento econômico brasileiro depende da crescente produção agropecuária, aliada ao conservacionismo. O sistema de plantio direto é o manejo de solo que reúne o mais amplo conjunto de preceitos da agricultura conservacionista. As áreas agrícolas cultivadas sob plantio direto, entretanto, têm apresentado duas camadas de solo distintas: uma entre, aproximadamente, 0 e 7 cm de profundidade, com condições físicas e químicas favoráveis ao desenvolvimento radicular; e uma entre, aproximadamente, 7 e 20 cm de profundidade, com menor permeabilidade do solo ao ar e a água, elevada resistência à penetração e baixa fertilidade química do solo. Estas condições promovem a concentração do sistema radicular das plantas agrícolas cultivadas na camada mais superficial do solo (0 a 7 cm), motivando perdas de produtividade por estresse hídrico. A magnitude desse problema se estende a mais de 30 milhões de hectares de lavoura cultivada sob plantio direto no Brasil, colocando em risco as projeções de exuberância da agricultura no país. Assim, o desenvolvimento desta tese teve o objetivo de estudar fatores que, além do processo de compactação mecânica do solo, possam estar promovendo a estratificação física e química de solos altamente intemperizados cultivados sob sistema de plantio direto. Dentre os possíveis fatores causadores deste tipo de degradação, foram avaliados: i) a aplicação excessiva de calcário, exclusivamente em superfície, ocasionando, na camada de 0 a 7 cm, a elevação do pH do solo para além do ponto de carga zero do solo, elevando o potencial eletronegativo do solo e por consequência, promovendo a dispersão de argila; ii) a migração da argila dispersa no perfil do solo, pela água de percolação, como um fator promotor de degradação física em subsuperfície; iii) o aporte de fitomassa ao solo em quantidade e qualidade para manter a estabilidade estrutural dos solos cultivados. Os resultados obtidos mostraram que o movimento de calcário no perfil dos solos estudados é muito lento, limitando o efeito deste produto a poucos centímetros abaixo do local onde ele é depositado ou incorporado (2,5 cm em 130 semanas), independentemente da dose aplicada (até 33,2 Mg ha-1). Assim, a calagem superficial promove e intensifica a estratificação dos atributos químicos no perfil do solo, aumentando, demasiadamente, o pH próximo à superfície e sendo ineficiente em mitigar a acidez na subsuperficie destes solos. A concentração de calcário na camada mais superficial dos solos altamente intemperizados aumenta a eletronegatividade do solo, resultando na dispersão de argila. A migração dos argilominerais dispersos no perfil do solo, pela água de percolação, promove uma série de alterações estruturais, incluindo a diminuição da porosidade total e da continuidade dos poros e o aumento da densidade e da resistência do solo à penetração na camada subsuperficial. A diminuição da estabilidade estrutural dos Latossolos sob cultivo também está ligada ao aporte de material orgânico ao solo em quantidade e qualidade inferiores à que ocorre no solo sob sistema nativo. Os Latossolos cauliníticos são mais propensos a diminuição da estabilidade estrutural quando submetidos ao cultivo. Portanto, a recomendação de calagem em solos altamente intemperizados cultivados sob plantio direto, precisa considerar a mineralogia do solo e a possível degradação estrutural promovida pela calagem em excesso. / The economic development of Brazil depends upon the increasing agricultural production associated with conservation practices. The no-tillage system is the soil management practice that brings together the broadest set of principles for conservation agriculture. Areas under no-till system, however, generally have two completely different soils layers: a surface layer, around 0 to 7 cm, with physical and chemical conditions favorable for root development; and a sub-surface layer, around 7 to 20 cm, with lower permeability to air and water, high soil penetration resistance, and low soil fertility. The existence of these stratified layers dramatically restricts the development of the root system into the sub-surface soil layer, which may result in reducing plant productivity by water deficit. This problem exists on more than 30 million hectares cultivated under no-tillage system in Brazil, and can compromise the optimistic projections of agricultural growth in the country. Therefore, more research is necessary to explore challenges that come with no-tillage. The aim of this thesis was to study the factors that can promote the physical and chemical stratification of highly weathered soils cultivated under no-till system. Among the factors that could cause this degradation, the following were studied: i) the application of excessive lime only on surface soil, or into the uppermost soil layer, which can increase its pH to levels beyond of the zero point of charge of soil, raising its electronegative potential and promoting, as a consequence, the clay dispersion; ii) the dispersed clay migration thtough the soil profile, by the percolation water, as a factor of physical degradation of sub-surface of soil cultiveted under no-tillage; and iii) the aplication of phytomass to the soil in insufficient amount and quality to maintain the soil structural stability of the soil. The results of this study showed that lime movement into the deeper soil profile, is very slow, as its impacts are limited to just a few centimeters below of where it is applied or incorporated (2.5 cm after 130 weeks), independent of the applied amount of lime. Thus, the surface lime application intensifies the chemical stratification of the clayey soils under no-tillage, increasing to much the soil pH of the uppermost soil layer, and being inefficient to decrease the soil acidity in the subsurface soil layer. The concentration of lime into the uppermost soil layer can significantly increase the electronegativity of the soil system and result in clay dispersion in the topsoil layer (0 to 5 cm). The resulting clay migration into the soil profile led to a series of structural alterations in subsurface layers, including: decrease of both soil porosity and pore continuity; and increase of both soil bulk density and soil penetration resistance in the sub-superficial layer. The structural stability decreasing of Oxisols under no-till system also is linked with the low addition of organic matter to the cultivated soil, in relation to the non-cultivated soils. The kaolinitic Oxisols are more susceptible to degradation than the gibbsitic Oxisols. Thus, it could be conclude that liming practices (rate and application methods of lime), mainly under no-till systems, need to consider both type and mineralogy of soil, as well as considering soil structure degradation promoted by over-liming in the uppermost soil layer.