Knowledge of the relationships between nitrogen fertilization and nitrogen availability is needed to guide plans for providing optimum tree growth by silvicultural operations. PART 1. Detailed studies of the mineralization of urea were made by laboratory incubation of black spruce humus samples. These studies form a part of an experiment in which urea is used for the first time to fertilize a soil supporting a black spruce stand. Urea seems to be a very good fertilizer because it is readily transformed to an available form of nitrogen. It is however doubtful that a nitrogen fertilization only could quickly and greatly affect the humus fertility. PART 2. Total number and number of ureolytic bacteria and fungi were determined at time intervals during a laboratory incubation of black sprucc humus samples. Such a quantitative and qualitative study of the microbial population of a raw humus had never been made. The potential for ureolysis is enormous because this humus contains an abundance of ureolyzing microorganisms Indeed, counts in excess of 100 millions per gram are not uncommon.

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The objective of this study was to examine the relationships between Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) foliar nutrient status and forest floor chemical properties. Foliar nutrient analysis data were collected on 27, 50- to 140-year-old Douglas-fir stands, for which the forest floor chemical properties had previously been analysed. The 27 sites encompassed a broad geographical area within the Coastal Western Hemlock Biogeoclimatic Zone. Foliar samples were individually analysed for total S, N, P, K, Ca, Mg, B, Cu, Zn, Fe, Al, Mn and for AFe (active iron). Four foliar nutrient ratios (N/S, N/P, K/Ca, Ca/Mg) were additionally calculated. As the foliar sampling intensity was often below that recommended in the provincial sampling guidelines, the precision of the within-site foliar nutrient variable mean values was examined for the lowest sampling intensity used in this study (n=8). Foliar nutrient and ratio variances from 6 of the 27 sites, for which 15 trees per site had been sampled, were used as population variance estimates. A sampling intensity of n=8 was found to be sufficiently large to provide foliar nutrient variable mean estimates with an allowable error of 20% (∝ =0.5) for all but the following foliar nutrients and ratios: B, Cu, Ca/Mg and K/Ca. Two combinations of forest floor horizons were examined for possible relationships with foliar nutrient variables: L plus F and L plus F plus H. These two combinations of forest floor horizons were referred to as the LF and the LFH layers. The two criteria used to select forest floor chemical properties are as follows: (1) the precision of the forest floor chemical property site estimate was less than or equal to 20% (∝=0.5) for the field sampling intensity used, or (2) the forest floor chemical property was an established measure of nutrient availabilty. The 12 LF and 16 LFH chemical properties selected included: LF and LFH: pH (CaCl₂), total-S, -N, -P, -Cu, -Zn, -Mg, -K, -C, Min-N (anaerobic mineralizable N), KC1-N (KC1 extractable N, A (lipids), and LFH (only): exK, exCa, exMg (1M NH₄OAC exchangeable bases) and extP (Bray P₁ extractable P). Simple linear relationships between foliar nutrient variables and LF and LFH chemical properties were initially examined. Strong negative associations were found between foliar S and certain forest floor chemical properties, namely LF: pH, LMg and LFH: pH, LMg, LexMg, LexCa, LexK (here and following, L signifies the natural logarithm). It was hypothesized that these relationships reflected the effect of the different sources of plant available sulphur predominant on the higher (17 sites) and lower (10 sites) forest floor pH sites. Organic sulphur mineralization and mineral weathering were suggested as the major sources of plant available sulphur for the higher forest floor pH sites; anthropogenic atmospheric sulphur was suggested as the major source of plant available sulphur for the lower forest floor pH sites. The efficacy of forest floor (LF and LFH) chemical properties for predicting and classifying foliar nutrient status was examined through the use of multiple regression and discriminant analysis, respectively. These analyses were performed for the four foliar nutrient variables for which a range in sufficiency and possible deficiency (actual or inducible) was indicated for the stands sampled: foliar N, S, AFe and N/S. One regression model of potential predictive value was found for foliar LS. Together, LFH pH and LFH LCu statistically accounted for 79% of the observed variation in foliar LS. Several LF and LFH chemical properties were able to reliably classify stands into the following total foliar S groupings: sufficient and deficient (actual or inducible). LF LMg and LF A provided the best classification of stands into the groupings: S sufficiency and N-inducible S deficiency, as defined by foliar N/S. Three LFH chemical properties: P, S, and LexK provided the best classification of stands in terms of adequate and slight to severely deficient foliar N status. LF and LFH chemical properties were only poorly able to classify foliar AFe status. It was concluded that the relationships found in this study could not be extrapolated beyond the present study, due to the unforeseen, yet probable, influence of slightly acidic precipitation on both nutrient cycling and foliar nutrient status for 10 of the 27 stands examined. / Land and Food Systems, Faculty of / Graduate

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Orientador: Salatiér Buzetti / Banca: Marcelo Andreotti / Banca: Ciniro Costa / Resumo: O cerrado é a principal região produtora de carne bovina do Brasil, sendo que a maior parte dessa produção é proveniente de sistemas extensivos de criação. Nesta região, a pecuária apresenta baixos índices de produtividade animal e baixo retorno econômico. Isso se deve, entre outros fatores, ao inadequado manejo do sistema solo-planta-animal, como por exemplo, a falta de interesse dos produtores em realizar a correção do solo e adubação de manutenção. Os pecuaristas preconizam que as plantas forrageiras são consideradas culturas de baixo valor e, por isso, não justificam o uso de corretivos e fertilizantes. Ao contrário do que muitos pensam, essas áreas deveriam receber tratamento de recuperação para melhorar a nutrição e a produtividade da planta forrageira, uma vez que um pasto com deficiência nutricional não gera o ganho de peso esperado dos animais. Este trabalho visou estudar a implantação de um pasto com alto potencial de produção e redução da estacionalidade da produção de forragens utilizando diferentes fontes e doses de nitrogênio. A realização deste projeto de pesquisa visou contribuir para o desenvolvimento da pecuária regional na medida em que subsidiou práticas adequadas de manejo da adubação nitrogenada, evidenciando fontes mais promissoras de N para a manutenção de maiores produtividades do capim. As fontes de N utilizadas foram: Entec (sulfonitrato de amônio com inibidor de nitrificação), nitrato de amônio, sulfato de amônio, Sulfammo e ureia, aplicadas na base de 100 kg ha-1 corte-1, assim como doses de N (50, 100, 150 e 200 kg ha-1 corte-1), tendo a ureia como fonte; em nove cortes. A espécie de forrageira utilizada foi o Panicum maximum Jacq cv. Mombaça, e avaliou-se a produtividade da massa de matéria seca; os teores de proteína bruta (PB), de fibra... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The cerrado is the main beef-producing region of Brazil, where most of this production comes from extensive systems of farming. In this region, the livestock sector has low levels of animal productivity and low economic returns. This is due, among other things, the improper management of the soil-plant-animal, such as the lack of interest of producers to hold the soil amendment and fertilizer maintenance. Ranchers say that the forage crops are considered low value and therefore do not justify the use of lime and fertilizer. Contrary to what many think, these areas should receive treatment recovery to improve nutrition and productivity of grasses, as a poor pasture does not generate the expected weight gain of animals. This work aimed to study the establishment of a pasture with high production potential and reduction of seasonality of forage production using different sources and doses of nitrogen. This study aimed to contribute to the development of regional livestock giving practices appropriate of management of nitrogen fertilization, showing most promising sources of N to maintain higher yields of grass. The N sources used were: Entec (ammonium sulfonitrate with nitrification inhibitor), ammonium nitrate, ammonium sulfate and Sulfammo, applied on the basis of 100 kg ha-1 cut-1, and N rates (0, 50 , 100, 150 and 200 kg ha-1 cut-1), using urea as source, in nine cuts; four replications. The type of forage used was Panicum maximum Jacq cv. Mombaça, and were evaluated: Productivity of dry matter; crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF). The different nitrogen sources applied at a dose of 100 kg ha-1 provided a similar effect on the productivity of dry matter and a chemical composition of the pasture mombaça-grass in low land cerrado. Urea applied to the dose... (Complete abstract click electronic access below) / Mestre

Made available in DSpace on 2014-06-11T19:29:43Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-12-20Bitstream added on 2014-06-13T18:39:38Z : No. of bitstreams: 1 fernandes_jc_me_ilha.pdf: 227290 bytes, checksum: 715b2cc59515f981efa97df84ccdd42d (MD5) / Universidade Estadual Paulista (UNESP) / O cerrado é a principal região produtora de carne bovina do Brasil, sendo que a maior parte dessa produção é proveniente de sistemas extensivos de criação. Nesta região, a pecuária apresenta baixos índices de produtividade animal e baixo retorno econômico. Isso se deve, entre outros fatores, ao inadequado manejo do sistema solo-planta-animal, como por exemplo, a falta de interesse dos produtores em realizar a correção do solo e adubação de manutenção. Os pecuaristas preconizam que as plantas forrageiras são consideradas culturas de baixo valor e, por isso, não justificam o uso de corretivos e fertilizantes. Ao contrário do que muitos pensam, essas áreas deveriam receber tratamento de recuperação para melhorar a nutrição e a produtividade da planta forrageira, uma vez que um pasto com deficiência nutricional não gera o ganho de peso esperado dos animais. Este trabalho visou estudar a implantação de um pasto com alto potencial de produção e redução da estacionalidade da produção de forragens utilizando diferentes fontes e doses de nitrogênio. A realização deste projeto de pesquisa visou contribuir para o desenvolvimento da pecuária regional na medida em que subsidiou práticas adequadas de manejo da adubação nitrogenada, evidenciando fontes mais promissoras de N para a manutenção de maiores produtividades do capim. As fontes de N utilizadas foram: Entec (sulfonitrato de amônio com inibidor de nitrificação), nitrato de amônio, sulfato de amônio, Sulfammo e ureia, aplicadas na base de 100 kg ha-1 corte-1, assim como doses de N (50, 100, 150 e 200 kg ha-1 corte-1), tendo a ureia como fonte; em nove cortes. A espécie de forrageira utilizada foi o Panicum maximum Jacq cv. Mombaça, e avaliou-se a produtividade da massa de matéria seca; os teores de proteína bruta (PB), de fibra... / The cerrado is the main beef-producing region of Brazil, where most of this production comes from extensive systems of farming. In this region, the livestock sector has low levels of animal productivity and low economic returns. This is due, among other things, the improper management of the soil-plant-animal, such as the lack of interest of producers to hold the soil amendment and fertilizer maintenance. Ranchers say that the forage crops are considered low value and therefore do not justify the use of lime and fertilizer. Contrary to what many think, these areas should receive treatment recovery to improve nutrition and productivity of grasses, as a poor pasture does not generate the expected weight gain of animals. This work aimed to study the establishment of a pasture with high production potential and reduction of seasonality of forage production using different sources and doses of nitrogen. This study aimed to contribute to the development of regional livestock giving practices appropriate of management of nitrogen fertilization, showing most promising sources of N to maintain higher yields of grass. The N sources used were: Entec (ammonium sulfonitrate with nitrification inhibitor), ammonium nitrate, ammonium sulfate and Sulfammo, applied on the basis of 100 kg ha-1 cut-1, and N rates (0, 50 , 100, 150 and 200 kg ha-1 cut-1), using urea as source, in nine cuts; four replications. The type of forage used was Panicum maximum Jacq cv. Mombaça, and were evaluated: Productivity of dry matter; crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF). The different nitrogen sources applied at a dose of 100 kg ha-1 provided a similar effect on the productivity of dry matter and a chemical composition of the pasture mombaça-grass in low land cerrado. Urea applied to the dose... (Complete abstract click electronic access below)

Although the physiological nitrogen demand of the soil microbial biomass is a major determinant of N mineralization in forest soils, the exact nature of the relationship is unclear. This study investigated the relationships between a respiration-based indicator of microbial physiological N demand (NIR) and N availability in forest soils. NIR was found to correlate significantly with net mineralized N in the field and annual foliar litterfall N fluxes. In a laboratory incubation, NIR was shown to be sensitive to changes in soil available C and N pools. These results demonstrated that microbial physiological N demand is determined by relative availabilities of labile C and N, and that it is significantly related to N cycling in forest soils. Results from a seasonal study of a forested watershed suggest that nutrient availability determined tree production and soil C availability, which in turn determined microbial physiological N demand and nitrogen dynamics in the forest.

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