Soil profile modification and cotton production

Hardpan soils of the southeastern Coastal Plains were mixed to depths up to 0.61 m in an attempt to alleviate strength problems associated with a subsurface pan. It was hypothesized that mixing the dense, coarse-textured E Horizon with the less dense Ap and the relatively clayey B horizon would increase the water-holding capacity of the E and decrease its strength. Mixed soil did have a higher amount of water held than the unmixed E, increasing it from 5 to 7% at -200 kPa matric potential. This would reduce its strength by approximately 0.1 MPa allowing easier root penetration whether the increased water is available for uptake or not. Although seed cotton in the deeply-mixed treatments outyielded the moldboard-plowed treatments by 233 kg/ha in one year, they were outyielded by 132 kg/ha in another year. The decrease in strength and the increases of retention as a result of the mixing were small and infiltration was unchanged. Furthermore, mixing of field samples was less homogenous than lab samples. It is doubtful that the level of improvement of cotton would warrant the effort involved in the mixing operation. Treatments at two sites were split into fertility subplots. The only significant fertility difference was between rates of N sidedressed when plants were about 0.40 m tall. The 20 kg/ha rate outyielded the 67 kg/ha rate by up to 300 kg/ha presumably because the higher rate encouraged vegetative growth and retarded boll formation which in turn limited lint and seed production. Interactions between tillage or mixing and fertility were non-significant. Plants grew better in the deeper disturbed soils in dryer years. Other crops may respond more favorably to the mixing

Liquid 4He: contributions to first principles theory of quantized vortices, thermohydrodynamic properties, and the lambda transition

Liquid 4He has been studied extensively for almost a century, but there are still a number of outstanding weak or missing links in our comprehension of it. This paper reviews some of the principal paths taken in previous research and then proceeds to fill gaps and create an integrated picture with more complete understanding through first principles treatment of a realistic model that starts with a microscopic, atomistic description of the liquid. Newly derived results for vortex cores and thermohydrodynamic properties for a two-fluid model are used to show that interacting quantized vortices may produce a lambda anomaly in specific heat near the superfluid transition where flow properties change. The nature of the order in the superfluid state is explained. Experimental support for new calculations is exhibited, and a unique specific heat experiment is proposed to test predictions of the theory. Relevance of the theory to modern research in cosmology, astrophysics, and Bose-Einstein condensates is discussed.Comment: 155 pages, 28 figure

Padrão geográfico de diversidade genética em populações naturais de Pau-rosa (Aniba rosaeodora), na Amazônia Central

Rosewood (Aniba rosaeodora Ducke, Lauraceae) is an Amazonian evergreen tree and a source of the purest linalool, the main component of its essential oil, which is very valuable in the international perfumery market. After decades of over-exploitation it is currently considered as threatened. We evaluated the genetic diversity and its distribution in four populations in Central Amazonia. Thirty-five reliable RAPD markers were generated, of which 32 were polymorphic (91.4%). Variation was higher within the populations (76.5%; p < 0.0001) and geographic distribution contributed to population differentiation (23.4%; p < 0.0001). The Amazon River had a small influence on gene flow (3.3%; p < 0.0001), but we identified evidence of gene flow across the river. There were significant differences in marker frequencies (p < 0.05), in agreement with the low gene flow (Nm = 2.02). The correlation between genetic distance and gene flow was - 0.95 (p = 0.06) and between geographic distance and gene flow was -0.78 (p = 0.12). There was a geographic cline of variability across an East-West axis, influenced as well by the Amazon River, suggesting the river could be a barrier to gene flow. Although threatened, these Rosewood populations retain high diversity, with the highest levels in the Manaus population, which has been protected for over 42 years in a Reserve.O Pau-rosa (Aniba rosaeodora Ducke, Lauraceae) é uma árvore amazônica fonte do mais puro linalol, o qual é o principal componente do seu óleo essencial e muito valioso no mercado internacional de perfumaria. Após várias décadas de intensa exploração, a espécie foi levada à categoria de ameaçada de extinção. Quatro populações naturais distribuídas na bacia Amazônia Central foram avaliadas quanto ao nível e a distribuição da diversidade genética. Trinta e cinco marcadores RAPD reprodutíveis foram gerados, dos quais 32 foram polimórficos (91,4%). A diversidade foi maior dentro das populações (76,5%; p < 0,0001) e a distribuição geográfica contribuiu para a diferenciação entre as populações (23,4%; p < 0,0001). A AMOVA indicou que pode haver uma influência parcial do Rio Amazonas no fluxo gênico (3,3%; p < 0,0001), mas foram identificadas evidências de fluxo gênico atravessando o rio. Houve diferenças significativas nas freqüências dos marcadores (p < 0,05) e o fluxo gênico estimado foi relativamente baixo (Nm = 2,02). A correlação entre a distância genética e o fluxo gênico foi de - 0,95 (p = 0,06) e para a distância geográfica e o fluxo gênico foi de - 0,78 (p = 0,12). Houve um padrão geográfico de variabilidade ao longo do eixo Leste - Oeste, influenciado também pelo Rio Amazonas, o que sugere que o rio poderia funcionar como uma barreira para o fluxo gênico. Apesar de ameaçadas, estas populações de Pau-rosa possuem alta diversidade, com o maior valor na população de Manaus, que vem sendo protegida por 42 anos em uma reserva

Soil profile modification and cotton production

Hardpan soils of the southeastern Coastal Plains were mixed to depths up to 0.61 m in an attempt to alleviate strength problems associated with a subsurface pan. It was hypothesized that mixing the dense, coarse-textured E Horizon with the less dense Ap and the relatively clayey B horizon would increase the water-holding capacity of the E and decrease its strength. Mixed soil did have a higher amount of water held than the unmixed E, increasing it from 5 to 7% at -200 kPa matric potential. This would reduce its strength by approximately 0.1 MPa allowing easier root penetration whether the increased water is available for uptake or not. Although seed cotton in the deeply-mixed treatments outyielded the moldboard-plowed treatments by 233 kg/ha in one year, they were outyielded by 132 kg/ha in another year. The decrease in strength and the increases of retention as a result of the mixing were small and infiltration was unchanged. Furthermore, mixing of field samples was less homogenous than lab samples. It is doubtful that the level of improvement of cotton would warrant the effort involved in the mixing operation. Treatments at two sites were split into fertility subplots. The only significant fertility difference was between rates of N sidedressed when plants were about 0.40 m tall. The 20 kg/ha rate outyielded the 67 kg/ha rate by up to 300 kg/ha presumably because the higher rate encouraged vegetative growth and retarded boll formation which in turn limited lint and seed production. Interactions between tillage or mixing and fertility were non-significant. Plants grew better in the deeper disturbed soils in dryer years. Other crops may respond more favorably to the mixing