A non-equilibrium sediment transport model for rill erosion

Sediment transport in rill flows exhibits the characteristics of non-equilibrium transport, and the sediment transport rate of rill flow gradually recovers along the flow direction by erosion. By employing the concept of partial equilibrium sediment transport from open channel hydraulics, a dynamic model of rill erosion on hillslopes was developed. In the model, a parameter, called the restoration coefficient of sediment transport capacity, was used to express the recovery process of sediment transport rate, which was analysed by dimensional analysis and determined from laboratory experimental data. The values of soil loss simulated by the model were in agreement with observed values. The model results showed that the length and gradient of the hillslope and rainfall intensity had different influences on rill erosion. Copyright (c) 2006 John Wiley & Sons, Ltd

Case Study: Influence Of Morphological Changes On Flooding In Jingjiang River

The middle reach of the Yangtze River, customarily called the Jingjiang River, together with its diversion channels and Dongting Lake, form a large complicated drainage system. In the last five decades, significant geomorphological changes have occurred in the drainage system, including the shrinkage of diversion channels, contraction of Dongting Lake, changes in the rating curve at the Luoshan station, and cutoffs of the lower Jingjiang River. These changes are believed to be the cause of the occurrence of abnormal floods in the Jingjiang River. Qualitative analyses suggest that the first three factors aggravate the flood situation in the lower Jingjiang River, while the last factor seems beneficial for flood prevention. To quantitatively evaluate these conclusions, a finite-volume numerical model was constructed. A series of numerical simulations were carried out to test the individual and combined effects of the aforementioned four factors, and these simulations showed that high flood stages in the Jingjiang River clearly are related to the geomorphological changes

Divergência genética entre acessos de batata-doce utilizando caracteres fenotípicos de raiz Genetic divergence among sweet potato accessions based on root traits

Estudos de quantificação da divergência genética entre acessos e caracterização dos recursos genéticos têm sido de grande importância em programas de melhoramento, auxiliando na identificação de genitores e no conhecimento do material genético disponível. Os objetivos do presente trabalho foram: (1) avaliar os acessos de batata-doce pertencentes ao banco de germoplasma da Embrapa com base em caracteres de raiz; (2) calcular a importância relativa dos caracteres morfo-agronômicos quantitativos na discriminação dos acessos e, (3) obter indicações das combinações híbridas mais promissoras para cruzamentos. Foi avaliada uma coleção de 11 clones pertencentes ao Banco Ativo de Germoplasma da Embrapa por meio de um experimento conduzido na Embrapa SPM/EN, em Canoinhas-SC. Os acessos foram cultivados em condições de campo no delineamento em blocos ao acaso com quatro repetições, onde a parcela experimental foi composta por 10 plantas. As plantas de cada parcela foram colhidas e avaliadas para 12 caracteres fenotípicos de raiz. O estudo indicou que os caracteres número e massa total de raízes e peso específico foram os que mais contribuíram para a divergência genética. A maioria dos acessos é bastante similar quanto aos caracteres quantitativos avaliados. Porém, há a possibilidade de ganhos com a heterose, geração de variabilidade genética e de progênies superiores cruzando-se os acessos dos diferentes grupamentos formados; pois os genótipos mais contrastantes '1228', '051-1' e '1270' foram agrupados entre os melhores para várias características como massa e número total de raízes, massa comercial de raízes; os dois primeiros apresentaram elevado peso específico e o '1270' apresentou coloração alaranjada intensa, indicativo de alto teor de &#946;-caroteno.<br>The estimation of the genetic divergence among accessions of a germplasm bank, as well as their characterization are very important in breeding programs in order to identify the best parental genotypes and to provide a better understanding of the available plant genetic resources. Considering this information, the objectives of this research were: (1) evaluate the sweet potato plant accessions of Embrapa Germplasm Bank based on root traits; (2) estimate the relative importance of quantitative morphoagronomic characters in the genotype discrimination; and (3) find out promising hybrid combinations for crosses. Then, 11 sweet potato clones from Embrapa Germplasm Bank were evaluated in a trial at Embrapa SPM/EN Canoinhas, Brazil. The genotypes were cultivated in field conditions on a randomized blocks experimental design with four replications; the experimental plot was composed of 10 plants. In each experimental plot the plants were harvested and 12 characteristics of the roots were evaluated. The total number and mass of roots, and the specific gravity were the characteristics with the greatest influence on the genetic divergence. Most of the evaluated genotypes were closely related considering their quantitative characteristics. However, it is possible to obtain useful gains with heterosis and the generation of superior progenies, through crosses between genotypes from the different groups; because the most contrasting genotypes '1228', '051-1' and '1270' were grouped among the best ones for various characteristics such as mass and total number of roots, marketable root mass, the first two showed a high specific weight and '1270' intense orange color, indicative of high levels of &#946;-carotene

A comparison of the properties of manufactured soils produced from composting municipal green waste alone or with poultry manure or grease trap/septage waste

Manufactured soil for landscaping purposes was produced by composting for 6 weeks (1) municipal green waste alone, (2) green waste amended with 25% v/v poultry manure, or (3) green waste immersed in, and then removed from, a mixture of liquid grease trap waste/septage. Composting temperatures increased most rapidly and reached highest values (78°C) in the grease trap/septage-amended green waste. In comparison with green waste alone, addition of poultry manure prolonged the period of elevated temperatures and increased the maximum temperature attained from 52°C to 61°C. Following composting, each of the materials was split into (1) 100% compost, (2) 80% compost plus 20% v/v soil, and (3) 70% compost plus 20% soil plus 10% coal fly ash. Addition of poultry manure or grease trap/septage to green waste prior to composting increased bulk density and reduced total porosity of the composted product. Addition of soil, or soil and ash, to composts increased bulk density, reduced total porosity, decreased percentage macropores, and increased percentage mesopores and available water-holding capacity. Bicarbonate-extractable P, exchangeable NH and NO, electrical conductivity (EC), soluble C, soluble C as a percentage of organic C, basal respiration, and metabolic quotient were all markedly greater in the grease trap/septage-amended than poultry manure-amended or green waste alone treatments. Values for extractable P and EC were considered large enough to be damaging to plant growth and germination index (GI) of watercress was less than 60% for all grease trap/septage composts. Extractable P and EC were also high, and GI was 100%