Made available in DSpace on 2017-07-21T14:19:36Z (GMT). No. of bitstreams: 1 Karine Sato da Silva.pdf: 1399940 bytes, checksum: 7e4d6aa73a1bc504cbbbf109e805da76 (MD5) Previous issue date: 2013-03-01 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The subsoil acidity is harmful towards the growing of plants roots and, consequently, affects the agricultural productivity. In handled areas in the no-till cropping system (SPD), the toxic effects caused by high levels of Al and Mn, due to the soil acidity, are corrected by the superficial liming. This technique improves the acidity of the superficial layers, but it presents no great efficiency in the acidity correction of deeper layers of the soil. The agricultural gypsum (CaSO4.2H2O) is an input that might help in the improvement of the subsoil’s chemical conditions, because besides of being a Ca and S source, it is also able to transport cationic nutrients to the sub superficial layers and reduce the Al activity. It happens, however, that there are questions about which situations may be expected beneficial effects regarding the agricultural gypsum use, and as for the amount that should be applied to reach such effects. A possible form to assist the comprehension of these questions is with the Data Mining (MD) utilization. However, the agronomic databases usually involve a limited number of registers, which difficult the MD use. As a result, this study addresses, beyond the MD utilization, a new research area involving MD in small databases. Therewith, the goals of this work were:(i) obtaining a better comprehension of the gypsum application effects in the chemical attributes of handled soil in SPD, (ii) identifying the chemical attributes of the soil that present narrower correlations with the estimation of the need of gypsum using selection techniques at the pre-processing stage, and (iii) defining models to the estimation of the need of agricultural gypsum in soils under SPD. The database used in this study was obtained from three distinct areas of the region of Campos Gerais do Parana, containing chemical attributes of the soil in different epochs coming from SPD experiments, which received increasing doses of agricultural gypsum on their surfaces. It was used Principal Component Analysis techniques based on B2 and B4 criteria, and also the Supervised ACP technique. Still regarding the pre-processing techniques, it was implemented a covariance matrix that assumes the marginal independence between the base attributes in their calculus and utilizes the B2 and B4 criteria for the attributes selection. For the databases expansion, besides the SMOTE technique, it was implemented the megatrend-diffusion (MTD) method. The M5Rules algorithm was utilized to find models of estimation of the need of agricultural gypsum. The results showed that the elapsed time after the gypsum application (epoch), the saturation through Ca and the saturation through Mg in the capacity of effective cations exchange (CTCe) of soil were the attributes which presented the narrower correlations with the dose estimation of gypsum. The work identified four possible models for the estimation of the need of agricultural gypsum, showing that the M5Rules algorithm was efficient for such prediction. The MTD method presented positive results because increased the correlation coefficient and reduced the average absolute error. / A acidez do subsolo é prejudicial ao crescimento das raízes das plantas e, consequentemente, afeta a produtividade agrícola. Em áreas manejadas no sistema plantio direto (SPD), os efeitos tóxicos causados pelos teores elevados de Al e Mn, decorrentes da acidez do solo, são corrigidos pela calagem superficial. Essa prática melhora a acidez das camadas superficiais, mas não apresenta grande eficiência na correção da acidez em camadas mais profundas do solo. O gesso agrícola (CaSO4.2H2O) é um insumo que pode auxiliar na melhoria das condições químicas do subsolo, pois além de ser fonte de Ca e S, também é capaz de transportar nutrientes catiônicos para as camadas subsuperficiais e reduzir a atividade do Al. Acontece,porém, que ainda existem dúvidas sobre quais as situações em que podem ser esperados efeitos benéficos do uso de gesso agrícola e também quanto à dose que deve ser aplicada para alcançar tais efeitos. Uma forma possível para auxiliar na compreensão dessas dúvidas é a utilização da Mineração de Dados (MD). Entretanto, as bases de dados agronômicos normalmente envolve um número limitado de registros, o que dificulta o emprego da MD. Em decorrência disso, estudou-se, além da utilização da MD, uma nova área de pesquisa que envolve a MD em pequenas bases. Com isso, os objetivos do presente trabalho foram: (i) obter melhor compreensão dos efeitos da aplicação do gesso nos atributos químicos de solos manejados no SPD, (ii) identificar os atributos químicos do solo que apresentam correlações mais estreitas com a estimativa da necessidade de gesso usando técnicas de seleção na etapa de pré-processamento, e (iii) definir modelos para estimativa de necessidade de gesso agrícola em solos sob SPD. A base de dados utilizada nesse estudo foi obtida de três áreas distintas da região dos Campos Gerais do Paraná, contendo atributos químicos do solo em diferentes épocas provenientes de experimentos sob SPD que receberam doses crescentes de gesso agrícola na superfície. Utilizaram-se técnicas de Análise de Componentes Principais (ACP) baseada nos critérios B2 e B4 e, ainda, a técnica de ACP Supervisionado. Quanto às técnicas de pré-processamento, implementou-se também uma matriz de covariância que assume a independência marginal entre os atributos da base no seu cálculo e utiliza os critérios B2 e B4 para a seleção dos atributos. Para ampliação da base de dados, além da técnica SMOTE, foi empregado o método mega-trend-diffusion (MTD). O algoritmo M5Rules foi utilizado para encontrar modelos de estimativa da necessidade de gesso agrícola. Os resultados mostraram que o tempo decorrido após a aplicação de gesso (época), a saturação por Ca e a saturação por Mg na capacidade de troca de cátions efetiva (CTCe) do solo foram os atributos que apresentaram as correlações mais estreitas com a estimativa da dose de gesso. O trabalho identificou quatro possíveis modelos para a estimativa da necessidade de gesso, mostrando que o algoritmo M5Rules foi eficiente para tal predição. O emprego do método MTD apresentou resultados positivos porque aumentou o coeficiente de correlação e diminuiu o erro médio absoluto.

Orientador: Orivaldo Arf / Banca: Orivaldo Arf / Banca: Maria Aparecida Anselmo Tarsitano / Banca: Helder Barbosa Paulino / Resumo: O trabalho foi conduzido no ano agrícola de 2005/06, no município de Selvíria, Estado do Mato Grosso do Sul e teve como objetivo avaliar o comportamento do arroz de terras altas irrigado por aspersão em função do manejo do solo e da adubação nitrogenada em cobertura. O delineamento experimental utilizado foi o de blocos ao acaso disposto em um esquema fatorial 3 x 2 x 7, totalizando 42 tratamentos constituídos pela combinação de três modalidades de preparo do solo (grade pesada + grade niveladora, escarificador + grade niveladora e plantio direto), duas fontes de adubos nitrogenados, na dose de 90 kg ha-1 (Uréia e um sulfonitrato de amônio com inibidor de nitrificação = Entec) e da aplicação de nitrogênio em diferentes épocas de desenvolvimento da cultura do arroz de terras altas, com quatro repetições. Os manejos do solo utilizados influenciaram a altura de plantas, grau de acamamento, total de grãos por panícula, grãos cheios e chochos por panícula e produtividade de grãos, onde o manejo com grade pesada apresentou melhores resultados. O manejo da adubação influenciou apenas a produtividade de grãos. O uso do Entec proporcionou um maior número de grãos cheios e menor número de grãos chochos em relação à uréia / Abstract: The research was conducted in 2005/06, in Selvíria, Mato Grosso do Sul State, and had the objective of evaluating the development of upland rice irrigated by aspersion considering the management of soil and top-dress nitrogenous fertilization as to grain productivity and quality. The experimental design was a randomized in a factorial scheme of 3 x 2 x 7, totalizing 42 treatments as a result of a combination of three types of soil management (heavy disk + leveling disk; disk plow + leveling disk; no-till), two nitrogenous seasoning sources, urea and sulfatenitrate ammonium with inhibitor of nitrification (Entec) and 90 kg ha-1, of applied at different growth stages on upland rice crop under sprinkler irrigation, with four repetitions. The soil management influenced the height of plants, degree of lodging rate, total of full and empty grainsser panicle and productivity of grains. The soil management with disk + leveling disk presented better resulted. Handling of the fertilization influenced only the productivity of grains. The use of Entec provided a bigger number of full grains and less empty grains in relation to use of urea / Mestre

Made available in DSpace on 2016-12-08T15:50:03Z (GMT). No. of bitstreams: 1 PGMS11DA003.pdf: 2953340 bytes, checksum: bbaae7a8b0e4fdd162058cd82f79cea9 (MD5) Previous issue date: 2011-08-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Under conservation soil tillage, the effectiveness of crop residues in reducing water erosion decrease if the mulch is transported by runoff and/or if the runoff furrows the soil. This phenomenon is called mulch failure, characterizing the critical slope length, i.e., the distance on the ground from which the flood gains sufficient shear stress to overcome the resistance to transport the mulch and/or the resistance of the soil to furrow. The objectives of this study were to define critical slope lengths and critical shear stress in two sowing directions under different types and doses of crop residues, in no-till. The field work was conducted from May 2009 to May 2011, on a Nitosol (Alfisol) in Santa Catarina, Brazil, in experimental units with dimensions of 3.5 x 11 m, and mean slope of 0.144 m m-1. Sowing directions transverse (contour) and parallel (up-and-down) to the slope were tested using maize (Zea mays), wheat (Triticum aestivum) and soybean (Glycine max) mulches at doses of 50 and 100% of the total residue produced. During the research, simulated rainfall tests were performed using a rotating-boom rainfall simulator, with rain intensity of 65 mm h-1 and 90 min of duration, which was time required to achieve the constant runoff rate. At the end of 90 min of rain, without disconnecting the rainfall simulator were applied increasing levels of extra flow of clean water at the upper part of the plots, simulating additional runoff from longer slopes. The mulch failure was evaluated based on the theory of erosion, using the relationship between erosion rate (Dp) x runoff rate (qm), sediment concentration in runoff (C) x runoff rate (qm) and runoff velocity (V) x runoff rate (qm). Moreover, the mulch failure was observed visually when it occurred. In all treatments were found the critical slope lengths, and, in general, contour sowing and higher dose of crop residues increased the critical slope length and critical shear stress in relation to the up-and-down sowing and the lowest crop residue dose, respectively. Such lengths and critical stress ranged from 35 to 155 m and 1.9 to 7.4 N m-2, respectively. The theory of erosion, the point of failure was identified jointly analyzing the relationships Dp x qm and C x qm. The relationship V x qm was not a good indicator of failure. The visual failure could be identified for maize and soybean residues, while for wheat it was not clearly distinct / Nos preparos conservacionistas de solo, a eficácia dos resíduos culturais na redução da erosão hídrica diminui se os resíduos forem transportados pela enxurrada e/ou se a enxurrada sulcar o solo. A esse fenômeno se denomina falha dos resíduos, caracterizando a existência de comprimento crítico de declive, ou seja, a distância no terreno a partir da qual a enxurrada adquire tensão cisalhante suficiente para superar a resistência do resíduo ao transporte e/ou a resistência do solo ao sulcamento. Os objetivos do trabalho foram definir comprimentos críticos de declive e a tensão crítica de cisalhamento em duas direções de semeadura direta, sob diferentes tipos e doses de resíduos culturais. O trabalho foi desenvolvido em campo, entre maio de 2009 e maio de 2011, sobre um Nitossolo Bruno aluminoférrico húmico, em São José do Cerrito (SC), usando unidades experimentais com dimensões de 3,5 x 11 m, com declividade média de 0,144 m m-1. Foram testadas as formas de execução de semeadura direta no sentido transversal (em contorno) e paralelo ao declive (na pendente), sobre os resíduos culturais de milho (Zea mays), trigo (Triticum aestivum) e soja (Glycine max), nas doses de 50% e 100% do total produzido para cada um deles. Foram realizados testes de chuva simulada com o uso de simulador de chuva de braços rotativos, na intensidade de chuva planejada de 65 mm h-1 e, com duração de 90 min cada um, tempo este necessário para se obter a taxa constante de enxurrada. Ao final dos 90 min de chuva, sem desligar o aparelho simulador de chuva, foram aplicados níveis crescentes de fluxo extra de água limpa na cabeceira das parcelas, simulando a enxurrada provinda de declives mais longos. Para identificação da falha dos resíduos, usou-se teoria de erosão, efetuando as relações entre taxa de erosão (Dp) x taxa de enxurrada (qm), concentração de sedimentos na enxurrada (C) x taxa de enxurrada (qm) e velocidade da enxurrada (V) x taxa de enxurrada (qm). Em adição, a falha dos resíduos foi avaliada visualmente. Detectou-se comprimento crítico de declive em todos os tratamentos, sendo que, de modo geral, a semeadura direta em contorno e a dose maior dos resíduos de milho, trigo e soja aumentaram o comprimento crítico e a tensão crítica de cisalhamento, em relação à semeadura direta na direção da pendente e à menor dose de resíduos, respectivamente. Tais comprimentos e tensões críticas variaram de 35 a 155 m e 1,9 a 7,4 N m-2, respectivamente. Da teoria de erosão, o ponto de falha foi melhor identificado analisando conjuntamente as relações Dp x qm e C x qm. A relação V x qm não foi um bom indicador da falha. A observação visual em campo indicou falha real dos resíduos de milho e soja, enquanto que para o de trigo, não houve clareza

Made available in DSpace on 2014-07-29T14:52:08Z (GMT). No. of bitstreams: 1 Tese cicero agronomia.pdf: 980115 bytes, checksum: fc39630e9c5fb7bef0bb3944a6ce5081 (MD5) Previous issue date: 2009-04-16 / Different soil organic matter pools under management systems and natural Cerrado vegetation were studied. These pools were estimated using their carbon and nitrogen contents. Total soil organic carbon and total nitrogen (COT and NT), carbon and nitrogen of particulate organic matter (COP and NP), mineral-associated organic carbon and nitrogen (COM and NM), particulate organic carbon associated with different aggregates size classes (COPA), microbial biomass carbon and nitrogen contents (CBM and NBM) and their relations, and basal respiration as a measure of microbial activity, were determined in this study. Eight treatments were used: seven soil management systems and an undisturbed area of Savanna type vegetation, Cerrado, as a reference. They were: heavy disk harrow and legume species cultivation during twelve years (GP); disk plow and legume species cultivation during twelve years (AD); minimum tillage with chisel plow starting five years after installing the experiment (ESC); no-tillage with biennial crop rotation: grass and legume species as cover crop (PD1); no-tillage with crop rotation and annual cover crops (PD2), no-tillage with annual crop rotation of grass and legume species (PD3), permanent pasture (PAST) and natural savanna vegetation, cerrado (CER). The experiment was established in a randomized blocks design with three replicates to study soil tillage and crop rotation dynamics, with temporal and spatial alternation. Soil samples were taken at five depths: 0-5, 5-10, 10-20, 20-30 and 30-40 cm. Soil samples were collected in February, 2008, at soybean flowering stage. The soil management systems cause changes on soil organic carbon contents mainly on particulate organic matter (> 53 μm) and microbial biomass fractions as compared to the Cerrado vegetation. The annual use of plow discs to soil tillage causes increase of associated minerals-organic matter levels. In soil and climatic conditions of Cerrado, the use of no-till system preceded by soil chemical and structural correction has promote a more uniform distribution of particulate organic matter in the profile. The microbial biomass is responsive to changes caused by different soil management systems in the Cerrado / Foram estudados diferentes compartimentos da matéria orgânica do solo sob sistemas de manejo e vegetação natural de Cerrado. Esses compartimentos foram estimados por meio de seus conteúdos de carbono e nitrogênio. Determinaram-se: carbono orgânico e nitrogênio total do solo (COT e NT, respectivamente); carbono e nitrogênio da matéria orgânica particulada (> 53 μm) (COP e NP, respectivamente); carbono e nitrogênio orgânicos associados a minerais (COM e NM, respectivamente); carbono orgânico particulado associado a classes de agregados (COPA); carbono e nitrogênio da biomassa microbiana (CBM e NBM, respectivamente) e suas relações; e respiração basal como medida da atividade microbiana. Utilizaram-se oito tratamentos: sete com sistemas de manejo do solo e um com vegetação natural de Cerrado, como referência. Os sistemas estudados foram: uso de grade pesada e cultivado com leguminosas há doze anos (GP); uso de arado de discos e cultivado com leguminosas há doze anos (AD); preparo mínimo com escarificador a partir do quinto ano de experimento (ESC); plantio direto com alternância bienal de gramíneas e leguminosas (PD1); plantio direto com rotação bienal e safrinha (PD2); plantio direto com alternância anual de gramíneas e leguminosas (PD3); pastagem permanente (PAST); e cerrado nativo (CER). O experimento foi projetado para estudar a dinâmica de sistemas de preparo do solo e a rotação de culturas, com alternância no tempo e no espaço. O delineamento experimental utilizado foi o de blocos ao acaso com três repetições. As amostras de solo foram coletadas em cinco profundidades: 0-5, 5-10, 10-20, 20-30 e 30-40 cm. A amostragem de solo foi realizada em fevereiro de 2008, por ocasião da floração da soja. Alterações nos teores de carbono orgânico pelo uso do solo no Cerrado ocorreram, principalmente, na fração particulada da matéria orgânica (> 53 μm) e na fração microbiana do solo (CBM), quando comparadas ao cerrado nativo. Com o uso freqüente de arado de discos no preparo do solo, ocorre aumento dos teores de matéria orgânica associada aos minerais. Nas condições edafoclimáticas do Cerrado, o uso do sistema de plantio direto, precedido de correção química e estrutural do solo, promove uma distribuição mais uniforme da matéria orgânica particulada no perfil. A biomassa microbiana é sensível às mudanças causadas pelos diferentes sistemas de manejo do solo no Cerrado

L'adozione di (agro)ecosistemi sostenibili viene indicata come una efficace strategia in grado sequestrare carbonio (C) nel suolo, mitigando così il cambiamento climatico e migliorando la fertilità. Sebbene il potenziale di sequestro del C della non-lavorazione (NT) sia stato generalmente sovrastimato, esso risulta essere di 0,26 Mg ha-1 anno-1 superiore rispetto al regime arativo. Inoltre, il 76,6% di questo quota è localizzato in frazioni considerabili come relativamente stabili. Il NT aumenta lo sviluppo radicale delle colture erbacee (es. mais, soia, frumento) negli stati superficiali del suolo (0-5 cm). Le correlazioni tra i parametri di densità radicale e le proprietà fisiche del suolo mostrano come lo sviluppo radicale sia un fondamentale indicatore di qualità del suolo in NT. I residui delle cover crops influenzano le emissioni di protossido d’azoto (N2O) in NT: i residui di segale favoriscono l'immobilizzazione dell’azoto (N), aumentandone così l'efficienza d’utilizzo e diminuendo le emissioni, mentre i residui di veccia vellutata aumentano l’N2O come conseguenza della mineralizzazione dell’N. Le emissioni di N2O e la produttività dei prati stabili possono essere positivamente correlate, perché meccanismi diversi rispetto alla regolazione indotta dalla disponibilità di N possono controllare l'N2O: il C potrebbe essere un principale fattore di regolazione per nitrificazione e denitrificazione. / Adoption of sustainable (agro)ecosystems has been widely suggested to increase soil organic carbon (C) sequestration, to mitigate climate change and enhance soil fertility. Although its carbon sequestration potential has been generally overestimated, no-till (NT) results in an extra C sequestration of 0.26 ± 0.18 Mg ha-1 yr-1 as compared to conventional tillage and 76.6% of this extra C is located in C pools which could be considered relatively stable. NT increases root development of field crops (i.e. maize, soybean, winter wheat) in the top soil (0-5 cm), while does not in the deeper soil (5-60 cm). Positive correlations between root density and soil physical parameters shows how roots are main drivers of soil physical properties under NT. Cover crop residues may affect nitrous oxide (N2O) emissions under NT: rye residues enhances soil-nitrogen (N) immobilization, thus increasing N use efficiency and decreasing N2O, while hairy vetch residues as cover crop under NT increases N2O as a consequence of soil-N mineralization. N2O emissions and shoot productivity may be positive correlated in grasslands, because other mechanisms than plant-induced regulation of soil N pool may control N2O: C could be a major factor regulating nitrification and denitrification processes.

La pratique du «sans labour» (NT) se développe dans le cadre de l’agriculture de conservation des sols. Cette pratique modifie nombre de propriétés du sol comme, par exemple, la répartition du phosphore (P) dans le profil du sol. L’objectif de cette thèse est d’analyser les impacts après plusieurs décennies du NT sur le cycle biogéochimique du P et d’intégrer ces effets dans un modèle de fonctionnement. Nous avons utilisé un essai au champ de longue durée sous maïs-soja (L’Acadie, Québec, Canada) implanté sur un sol argilo-limoneux. Le dispositif était un split-plot à 4 blocs avec mouldboard plough (MP) et sans labour (NT), subdivisés par 3 doses de fertilisation en P minéral [0 (0P), 17.5 (0.5P), 35 (1P) kg P ha-1] apportées sur le maïs et localisées à 5 cm de profondeur et à 5 cm du rang de maïs.La concentration des ions phosphates du sol (Cp) test était relativement uniforme dans la couche labourée (0-20 cm) (0.08 mg P L-1), puis baissait légèrement dans 20-30 cm (0.05 mg P L-1) et davantage au-delà (0.01 mg P L-1). Sous les traitements [NT, 0.5P] et [NT, 1P] traitements, le Cp était plus élevé dans la couche 0-10 cm (0.28 et 0.19 mg P L-1) que dans la couche labourée mais baissait rapidement avec la profondeur. Cette stratification verticale sous NT était également observée pour les teneurs en P-Olsen, P-M3 et autres nutriments comme C, N et K. Après 23 et 24 années d’essai, il y avait tendanciellement moins de racines du maïs sous NT (-14%) que sous MP, probablement à cause de la présence plus importante d’adventices sous NT. Pour le soja, il y avait beaucoup plus de racines dans la couche 0-10 cm sous NT (44% de longueur total) que sous MP (21%) et inversement dans la couche 10-20 cm. Ces différences de distribution des racines sous NT et MP correspondent à la stratification de N, P, et K.Cet ensemble de données sur la distribution des racines et du phosphore a été utilisé pour i) évaluer un modèle 1D décrivant la dynamique du P sur plusieurs décennies dans la couche labourée du sol, ii) proposer un mode d’estimation de la distribution du prélèvement dans le profil de sol, et iii) développer un modèle spatialisé 2D décrivant la dynamique du P pour le traitement sans labour. Ce modèle permet de simuler l’évolution de la disponibilité en P du sol sur le long terme quels que soient les modes de préparation du sol et le régime de fertilisation P. Même si le modèle surestime parfois la disponibilité en P à proximité de la zone fertilisée, il permet de prédire la stratification du P du sol en NT et ses conséquences sur le prélèvement de P en relation avec les propriétés du sol et le développement du système racinaire. Il pourra contribuer à améliorer le raisonnement de la fertilisation phosphatée dans le contexte du sans-labour. / The no-till (NT) is gaining great attention for soil preparation. This practice modifies number of soil properties such as the distribution of phosphorus (P) in the soil profile. This work aims to analyze the impacts on the biogeochemical P cycle after decades of NT and incorporate those effects in an operational model. We used a long-term field experiment under corn-soybean rotation established on a clay loam soil (L’Acadie, Quebec, Canada). The design was a split-plot plan with 4 blocks under moldboard plough (MP) and NT, subdivided by 3 doses of P [0 (0P), 17.5 (0.5P), 35 (1P) kg P ha-1] applied in corn phase and localized to 5-cm deep and 5-cm from the corn row.The phosphate ion concentration in MP was relatively constant (0.08 mg P L-1) in the tilled layer (0-20 cm), slightly lower in 20-30 cm (0.05 mg P L-1) and much lower below (0.01 mg P L-1). In [NT, 0.5P] and [NT, 1P] plots, Cp was higher (0.28 et 0.19 mg P L-1) in the 0-10 cm layer compared to the tilled layer in MP, but decreased sharply with depth. This vertical stratification in NT was also observed for P-Olsen, P-M3 and other nutrients as C, N, and K. After 23- and 24-year of experimentation, maize roots tended to be fewer (-14%) under NT than MP, probably because of increased weed infestation under NT. For soybean, more roots accumulated in the 0-10 cm layer under NT (44% of total length) than MP (21%) and vice versa for the 10-20 cm layer. Those differences in root distribution under NT and MP corresponded to the stratification of N, P, and K.This set of data on the distribution of roots and phosphorus was used i) to develop a 1D model describing P dynamics over several decades in MP, ii) to test a method to assess the spatial P uptake distribution according local root length density and soil P availability, and iii) to develop a spatial 2D model describing P dynamic in NT. This model simulates the soil P availability dynamic on long term according soil properties and crop root distribution within soil profile for different soil preparation regime and different P fertilization rate. Although the model overestimates the P availability near the localized P fertilizer, it is able to predict the soil P stratification in NT treatment and its consequences on crop P uptake. This new model will be a useful tool to improve P fertilization management in context of no-till practices.

Die im ökologischen Pflanzenbau oftmals durchgeführte Grundbodenbearbeitung mit dem Pflug wird genutzt, um Unkräuter und Krankheitserreger möglichst wirksam zu regulieren, zusätzlich soll die Mineralisierung von Stickstoff im Boden angeregt werden. Eine intensive Bodenbearbeitung mit dem Pflug birgt jedoch ein erhöhtes Risiko der Bodenerosion durch Wind sowie Wasser, zudem wird die Bildung von Bodenverdichtungen im Wurzelbereich der angebauten Kulturpflanze gefördert. Der Einsatz des Pfluges führt zu einem erhöhten Kraftstoffverbrauch bei den einge-setzten Zugfahrzeugen, zusätzlich steigt der Arbeitszeitbedarf. Der vorliegende Versuch im ökologischen Landbau beschäftige sich mit den Effekten einer reduzierten Bodenbearbeitung mit dem Grubber und Direktsaat im Vergleich zu einer wendenden Bearbeitung mit Pflug auf Ertragsbildung, Unkrautwachstum und Stickstoffflüsse im Fruchtfolgeglied Erbse und Winterweizen. Hierzu erfolgte die Anlage eines Feldversuches am Standort Pinkowitz bei Dresden (Parabraunerde aus Löss, 55 Bodenpunkte) in einer 2- (Erbse) bzw. 3-faktoriellen (Weizen) Spaltanlage in den Jahren 2009 und 2010. Die Körnererbse wurde am 19.04.09 bzw. 08.04.10 nach einer Grundbodenbearbeitung mit dem Pflug bzw. Grubber oder in Direktsaat eingesät. Eine Woche später erfolgte die Einsaat einer Untersaat mit Erdklee zur Gründüngung in der Hälfte der Parzellen. Am 26.10.09 bzw. 23.10.10 wurde Winterweizen analog zu den Saatsystemen zur Körnererbse (Pflug/Grubber/Direktsaat), jedoch im 90 Grad Winkel versetzt zur Einsaat der Erbse, eingesät. In einem Teilversuch wurde mittels 15N-Isotopenanreicherung von Erdklee-sprossmasse die Verfügbarkeit des Stickstoffes aus der Sprossmasse des Erdklees im Winterweizen quantifiziert. Ziel der Versuche war es die Effekte des Anbaus von Erbsen und Weizen bei konservierender Bodenbearbeitung im ökologischen Pflanzenbau im Vergleich zu einer intensiven Bodenbearbeitung zu identifizieren und daraus Strategien für einen verstärkten Einsatz von reduzierter Bodenbearbeitung und Direktsaat abzuleiten.   Es erfolgte die Erhebung der Sprosstrockenmasse von Erbse, Erdklee und Unkraut zu BBCH 20, 65 und 89, sowie vor der Saat des Weizens. Die Sprossmasse des Weizens und des Unkrautes erfolgte zu den BBCH-Stadien 39, 59 und 89 des Weizens. Zusätzlich wurden in beiden Kulturen zur Druschreife eine Beerntung per Hand und ein Kernparzellendrusch durchgeführt. Zeitnah zur Entnahme von Pflanzenproben fand eine Entnahme von Bodenproben zur Bestimmung des Nmin-Vorrates im Boden statt. Zudem erfolgten Erhebungen zur Bodentemperatur, der Lagerungsdichte des Bodens im Saathorizont und der Bodenfeuchte. Aus den gewonnenen Daten konnten mehrere Indizes und Kennzahlen zur Ertragsbildung und Stickstoffversorgung der angebauten Kulturpflanzen errechnet werden. Die Ertragsleistung der Körnererbse war nach einer reduzierten Bodenbearbeitung leicht, jedoch nicht signifikant vermindert. Auch eine Einsaat der Erbse in Direktsaat hatte lediglich in einem Versuchsjahr eine signifikante Minderung des Kornertrages zu Folge. Die Keimung des Erbsensaatgutes war nach Einsaat in Direktsaat beeinträchtigt und die Erbse konnte diesen verminderten Feldaufgang nicht kompensieren. Die verringerte Fähigkeit der Erbse zur Kompensation geringer Feldaufgänge wurde durch eine hohe Unkrautsprossmasse, einen geringen Stickstoffversorgungsindex der Erbse zur Blüte sowie einer hohen Lagerungsdichte des Bodens außerhalb des Säschlitzes verursacht. Um auch unter Direktsaat-bedingungen höhere Kornerträge zu erzielen müssen die genauen Ursachen für den geringen Feldaufgang ermittelt werden, da sich im vorliegenden lediglich Anhaltspunkte wie eine ungenaue Saatgutablege und ein verstärktes Auftreten von Pflanzenkrankheiten dafür ergeben haben. Die Folgekultur Winterweizen war nach einer Saat in Direktsaat im Vergleich zu Pflug und Grubber in der Ertragsbildung massiv beeinträchtigt. Wurde die Vorfrucht Erbse in Direktsaat gesät, zeigte sich ein leicht negativer Effekt auf den Kornertrag des Weizens unabhängig davon, ob die Folgefrucht Weizen nach einer Bodenbearbeitung mit Pflug und Grubber oder in Direktsaat gesät wurde. Eine einmalige Anwendung von Direktsaat bei Erbse war im vorliegenden Versuch auch unter den Bedingungen des ökologischen Landbaus gut möglich, die Ertragsrückgang betrug 13,3 % in 2009 bzw. 26,2 % in 2010. Die Untersaat Erdklee reduzierte das Wachstum des Unkrautes in allen Varianten der Bodenbearbeitung und konkurrenzierte die Deckfrucht lediglich schwach, so dass in 2009 eine Minderung des Kornertrages um 1,1 dt ha-1 in 2010 um 4,6 dt ha-1 verzeichnet wurde. Die Beurteilung der Umsetzungsprozesse des Stickstoffes aus der Erdkleesprossmasse mittels 15N-Spurenanreicherung von Winterweizen über das Aufbringen von angereichertem Erdkleesprossmaterial war in jeder Variante der Bodenbearbeitung sicher möglich. Die Aufnahme von Stickstoff aus der Erdklee-sprossmasse durch den Winterweizen ging mit Rücknahme der Bodenbearbeitungs-intensität zurück, so stammten zur Abreife des Weizens nach einer Pflugsaat 13,0 % des Stickstoffes im Spross des Weizens aus der Sprossmasse des Erdklees, nach Grubber bzw. Direktsaat betrug dieser Anteil 8,6 % bzw. 8,5 %. Die Mineralisierung des Stickstoffes aus der Erdkleesprossmasse hielt jedoch nach konservierender Bodenbearbeitung insgesamt nicht lange an, so dass keine Steigerung der Korn-proteingehalte über eine zusätzliche Bereitstellung von Stickstoff während der Kornfüllungsphase erzielt werden konnte.:Abbildungsverzeichnis Tabellenverzeichnis 1 Einleitung 2 Stand des Wissens 2.1 Effekte verschiedener Intensitäten der Bodenbearbeitung 2.2 Direktsaatversuche im ökologischen Landbau 2.3 Untersaat 2.4 N-Transfer aus der Untersaat in die Folgefrucht 3 Material und Methoden 3.1 Standorteigenschaften und Witterung 3.2 Versuchsaufbau 3.3 Probennahme und Probenaufarbeitung 3.4 Statistische Analysen 4 Ergebnisse 4.1 Zwischenfrucht 4.2 Erbse 4.2.1 Auflaufen der Erbse 4.2.2 Bestandsentwicklung und Kornertrag der Erbse 4.2.3 Harvest-Indizes und Stickstoffakkumulation 4.2.4 N-Aufnahme der Sommergerste 4.3 Winterweizen 4.3.1 Etablierung des Winterweizens 4.3.2 Bestandsentwicklung und Kornertrag des Winterweizens 4.3.3 Harvest-Indizes und Kornproteingehalt des Winterweizens 4.3.4 Nmin unter Winterweizen 4.4 Stickstoffaufnahme des Weizens aus 15N-markiertem Erdklee 5 Diskussion 5.1 Ertragsleistung Erbse 5.2 Ertragsleistung Winterweizen 5.3 Legume Untersaat Erdklee 5.4 15N-Anreicherung 6 Zusammenfassung 7 Literaturverzeichnis 8. Anhang Versicherung

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The transition of natural landscapes to intensive agricultural uses has resulted in severe loss of soil organic carbon (SOC), increased CO₂ emissions, river depletion, and groundwater overdraft. Despite negative documented effects of agricultural land use (i.e., soil erosion, nutrient runoff) on critical natural resources (i.e., water, soil), food production must increase to meet the demands of a rising human population. Given the environmental and agricultural productivity concerns of intensely managed soils, it is critical to implement conservation practices that mitigate the negative effects of crop production and enhance environmental integrity. In the Mississippi Alluvial Valley (MAV) region of Mississippi, USA, the adoption of cover crop (CC) and no-tillage (NT) management practices has been low because of a lack of research specific to the regional nuances. Therefore, this study assessed the long-term soil physiochemical and biological responses from integrating CC and NT management to agricultural soils of the region. Research plots were established in a split-block design with two tillage treatments: NT and reduced tillage (RT) and three CC treatments: no cover (NC), rye (RY) and a rye+clover (RC) mix. Soil samples were taken during the growing season of 2019 and 2020. Bulk density was found to be significantly lower in NT plots and aggregate stability was greatest in plots with a single CC species. Moisture retention increased in NT.. Soil organic carbon was greater in NT and CC treatments and there was no difference in CO₂ flux. Bacterial abundance had a positive effect on SOC but a negative effect on CO₂. The rate of proportional change and pattern of variability in C pools suggested loss of SOC in reduced tillage (RT) treatments. Microbial abundance, functional genes and enzyme activity was greater in NT with CC, but diversity was greater in RT. No-tillage practices lower diversity and influence long-term community changes while CC practices enact a seasonal response to environmental conditions. I conclude that in heavy clay soils of the mid-South region of the MAV, RT with a CC is optimal for soil health traits associated with crop sustainability, however the management will still contribute to increased CO₂ emissions.

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