El proceso de agriculturización sufrido en la Región Pampeana, sumado a la mayor participación de la soja entre los cultivos de verano, dio como resultado una importante reducción en el aporte de residuos y del contenido de materia orgánica (MO) edáfica. La MO es determinante de la fertilidad física y química del suelo, ya que es un elemento clave en el ciclado de nutrientes. Cambios en las secuencias de cultivos y/o el uso de cultivos de cobertura (CC) pueden llegar a afectar los valores de MO, principalmente la fracción lábil. El objetivo principal del trabajo fue avaluar la interacción entre el CC y diferentes cultivos y como esto afecta la disponibilidad de los nutrientes en forma directa o a través de su efecto potencial sobre las fracciones de la MO. Para estudiar el efecto de los CC se utilizó un ensayo de larga duración principal ubicado en General Villegas y se compararon parte de los efectos observados con otros dos sitios con diferentes características edafoclimáticas (Balcarce y Oliveros). Como principales resultados se destacan, el incremento no solo de las fracciones orgánicas lábiles de la MO (hasta un 110%), sino también de la MO total en los primeros 5 cm de suelo debido al uso del CC en un (28,8%) aproximadamente. Con respecto al N se observó el mismo efecto del CC incrementando las fracciones lábiles (hasta un 88%) y totales (19,8%). Se observó un incremento en las fracciones orgánicas lábiles del fósforo (P) (71,9 y 44,7 mg kg-1 con y sin CC). Se observaron además efectos temporarios sobre la disponibilidad de P y azufre (S). En el caso de los micronutrientes se observó un incremento en la disponibilidad y la fracción orgánica lábil del manganeso (Mn). Estos cambios en sus fracciones lábiles podrían estar evidenciando un mayor reciclado y transformación de fracciones inorgánicas a orgánicas. Con respecto a los cultivos comerciales, el CC no tuvo un efecto sobre sus rendimientos. Los resultados obtenidos en General Villegas se repitieron en mayor medida en la localidad de Balcarce, mientras que en Oliveros se observó un menor efecto del CC debido a la mayor temperatura ambiente que descompone con mayor velocidad los residuos de cosecha disminuyendo su incorporación al suelo. / The Pampas Region has suffered a process of agriculturization, with a greater participation soybean crop. This lead to a significant reduction in the contribution of crops residues to the soil, affecting the soil organic matter (SOM) content. SOM is determinant in the physical and chemical soil fertility, being a key element in the nutrient cycling. Changes in crop sequences and the use of cover crops (CC) can affect MOs values, mainly the labile fraction. The main objective of the work was to evaluate the effects of the crops rotation and the CC over the SOM and the soil nutrient availability. A long-term experiment located in General Villegas, Buenos Aires was sampled in order to study this effects. Also parts of the results observed were compared with the effect of CC in two other sites with different edaphoclimatic characteristics (Balcarce, Buenos Aires y oliveros, Santa Fe). In General Villegas, CC increase the labile fraction (110%) and the total OM (28.8%). Respect to nitrogen (N), CC increases the labile fraction in 88% and the total soil organic nitrogen (SON) in 19.8%. In regard of the other nutrients, the phosphorus (P) bounded to the MOP was increase from 44.7 (without CC) to 71.9 because of the use of the CC. Temporary effects on the availability of P and sulfur (S) was observed. In the case of micronutrients, an increase of the availability and the MOP bounded fraction of manganese (Mn) were observed. With respect to the commercial crops, CC did not have a statistically significant effect on their yields. In Balcarce, it was observed similar effects of CC in carbon, nitrogen and soil nutrients availability. In Oliveros a lower effect of the CC was observed due to the higher ambient temperature that probably decomposes crop residues with greater speed, decreasing its incorporation into the soil. / TEXTO PARCIAL en período de teletrabajo

Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2017-10-11T20:09:52Z No. of bitstreams: 1 2016 - Liliane de Souza Ferreira.pdf: 1966686 bytes, checksum: eebcf58399ae9c79283075f9e54588e5 (MD5) / Made available in DSpace on 2017-10-11T20:09:52Z (GMT). No. of bitstreams: 1 2016 - Liliane de Souza Ferreira.pdf: 1966686 bytes, checksum: eebcf58399ae9c79283075f9e54588e5 (MD5) Previous issue date: 2016-08-09 / The management of weeds is complex and comprises a major component of the production cost of most cultures. Growing cover crops is one of the forms of management to reduce weeds competing. Agrobiodiversity, including the biota and the surrounding properties, constituting a cultural and natural capital able to provide ecosystem services. In this context, we developed a study to investigate the potential of wild species Crotalaria incana (rattlesnake rattle or Xique-Xique) and Diodia saponariifolia (Poaia the swamp), which occur in a nearby landscape the Atlantic Forest fragments in the River Basin region Guapi-Macacu-RJ, as part of sustainable agro-ecosystems, constituting strategy to reduce the use of herbicides and enhancing local biodiversity. This potential was assessed in C. incana through phenological studies of plant height, crown diameter, number of branches, presence of inflorescence and number of pods along the cycle and at different times, October, January, February and March. Also evaluated in its interaction with the climate and planting dates. It was found that the planting October C. incana had the longest growing season, low seed production. In the planting in February, the performance of C. incana was good in both parameters; while planting in March, C. incana demonstrated lower performance for mass production and seeds. Preliminary assessments of total biomass and macronutrients, indicate the potential of C. incana as a cover crop that needs to be better investigated. As for D. saponariifolia, a creeping species characterized as macrophyte, evaluations were made of soil coverage percentage after its introduction, compared to the most frequently dominant families in the system, Poaceae and Cyperaceae. Subsequently evaluated the seed bank behavior in this same area after being introduced (experimental area), compared to natural area, which was already established spontaneously. We observed a cooling populations of Poaceae and Cyperaceae after the introduction D. saponariifolia. The spontaneous seed bank revealed a reduction in the expression of these families, important competitors in the system. Possible allelopathic effect of D. saponariifolia in suppressing spontaneous, was evaluated by bioassay with the soil of the natural area where D. saponariifolia prevails spontaneously. In this ground sesame seeds were germinated Sesame indicu L. () in 15-cell trays 3 treatments (T1, T2, T3). T1, activated carbon was added to neutralize allelopathic effects harmful to the development of seedlings. T2, do not add anything. In T3 (control) used a soil adjacent area without the presence of individuals D. saponariifolia. There was no significant difference in the development of seedlings in 3 treatments, indicating no evidence of allelopathic effects of D. saponariifolia on Sesame germination. We can infer that the suppression of processes D. saponariifolia are only for "muffling". / O manejo de plantas espont?neas ? complexo e comp?e um dos principais componentes do custo de produ??o da maioria das culturas. O cultivo de plantas de cobertura ? uma das formas de manejo para redu??o das plantas espont?neas competidoras. Neste contexto desenvolveu-se um estudo com objetivo de investigar o potencial das esp?cies espont?neas Crotalaria incana (Xique-Xique) e Diodia Saponariifolia (Poaia do brejo), que ocorrem em uma paisagem pr?xima a fragmentos de Mata Atl?ntica, na regi?o da Bacia do Rio Guapi-Macacu-RJ, como parte integrante de agroecossistemas sustent?veis, constituindo estrat?gia para redu??o do uso de herbicidas e incremento da biodiversidade local. Este potencial foi avaliado em C. incana, atrav?s de estudos fenol?gicos de altura da planta, di?metro de copa, n?mero de ramos, presen?a de infloresc?ncia e n?mero de vagens ao longo do ciclo e em diferentes ?pocas Outubro, Janeiro, Fevereiro e Mar?o). Avaliou-se tamb?m sua intera??o com o clima e ?pocas de plantio. Constatou-se que no plantio de Outubro, C. incana teve o ciclo vegetativo mais longo, com pouca produ??o de sementes. J? no plantio em Fevereiro, o desempenho de C. incana foi bom em ambos par?metros; enquanto no plantio de Mar?o, C. incana demonstrou menor desempenho tanto para produ??o de massa como de sementes. Avalia??es preliminares de macronutrientes totais e biomassa indicam bom potencial de C. incana a ser melhor investigado. Quanto ? D. Saponariifolia, uma esp?cie rasteira caracterizada como macr?fita, foram feitas avalia??es de porcentagem de cobertura do solo ap?s sua introdu??o, comparando com as fam?lias mais frequentemente dominantes no sistema, Poaceae e Cyperaceae. Posteriormente avaliou-se o comportamento do banco de sementes nesta mesma ?rea ap?s ser introduzida (?rea experimental), comparando com ?rea natural onde j? estava estabelecida espont?neamente. Observou-se um arrefecimento das popula??es de Poaceae e Cyperaceae ap?s a introdu??o D. saponariifolia. O banco de sementes de espont?neas revelou uma redu??o na express?o destas fam?lias e de Asteraceae, importantes competidoras no sistema. Poss?vel efeito alelop?tico de D. saponariifolia na supress?o de espont?neas, foi avaliado atrav?s de biosensaio com o solo da ?rea natural, onde D. saponariifolia predomina espontaneamente. Neste solo foram germinadas sementes de Sesamo indicu L. (Gergelim) em bandejas de 15 c?lulas, com 3 tratamentos (T1,T2,T3). Em T1, adicionou-se carv?o ativado, que neutralizaria efeitos alelop?ticos prejudiciais ao desenvolvimento das pl?ntulas. Em T2, n?o se adicionou nada. Em T3 (controle) utilizou-se um solo da ?rea adjacente, sem presen?a de indiv?duos de D. saponariifolia. N?o houve diferen?a significativa no desenvolvimento das pl?ntulas nos 3 tratamentos, indicando n?o haver evid?ncias de efeitos alelop?ticos de D. saponariifolia na germina??o de Gergelim. Podemos inferir que os processos de supress?o de D. saponariifolia sejam apenas por ?abafamento?.