Toxic effects of limonene againstCulex quinquefasciatus Say larvae and its interference with oviposition

Limonene, a major constituent of citrus essential oil isolated from abraded fresh peels of bitter orangeCitrus aurantium L., was tested for its toxicity against early 4th instar larvae ofCulex quinquefasciatus Say. The response of treated larvae was concentration-dependent and LC₉₀s were 53.80 and 32.52 ppm after 24 and 48 h of treatment respectively. Limonene treated water was less favorable for oviposition by females ofCx. quinquefasciatus.     

A new stochastic optimization model for deficit irrigation

Deficit irrigation has been suggested as a way to increase system benefits, at the cost of individual benefits, by decreasing the crop water allocation and increasing the total irrigated land. Deterministic methods are common for determining optimal irrigation schedules with deficit irrigation because considering the inherent uncertainty in crop water demands while including the lower and upper bounds on soil moisture availability is a hard problem. To deal with this, a constraint state formulation for stochastic control of the weekly deficit irrigation strategy is proposed. This stochastic formulation is based on the first and second moment analysis of the stochastic soil moisture state variable, considering soil moisture as bounded between a maximum value and a minimum value. As a result, an optimal deficit irrigation scheduling is determined using this explicit stochastic model that does not require discretization of system variables. According to the results, if irrigation strategy is based on deterministic predictions, achievement of high, long-term expected relative net benefits by decreased crop water allocation and increased irrigated land may have a higher failure probability.     

Effects of bicarbonate and different Fe sources on vegetative growth and physiological characteristics of bell pepper (Capsicum annuum L.) plants in hydroponic system

In order to determine the best iron (Fe) sources under alkaline conditions, an factorial experiment was conducted based on a completely randomized design with two factors of Fe fertilizer at four forms [iron sulfate (FeSO₄), Fe- ethylenediaminetetraacetic acid (EDTA), Fe- diethylenetriaminepentaacetic acid (DTPA) and Fe- ethylenediamine-N,N’-bis (EDDHA), and sodium bicarbonate (NaHCO₃)] at three levels (0, 10 and 15 mM) with three replications. Results showed that the highest loss of vegetative growth (stem length, leaf number, leaf area, stem diameter, and leaf, stem and root dry weight) and ecophysiological parameters (F_v/F_m, SPAD and RWC) was observed in plants treated with FeSO₄. Alkalinity stress increased proline concentration especially in FeSO₄ treatment. Bicarbonate treatments decreased Fe concentration in plant tissues. Fe-EDTA and Fe-DTPA fertilizer sources acted similar or even better than EDDHA at 10 mM NaHCO₃ concentration, but the best Fe fertilizer source was Fe-EDDHA at 15 mM NaHCO₃ concentration.     

pH Dependent Growth of Chlorella in a Continuous Culture System 1

Production and growth of a local strain of marine Chlorella sp. was investigated under different pH levels ranging from pH 6.0–8.5 using 200 L capacity algal tubes. The results show that a pH of 6.5 will be most conducive for producing this species in a continuous culture system. The highest production was 136 g/m³/d with a mean of 117 ± 11 g/m³/d at pH 6.5 compared with other pH levels tested. The total fatty acid content was elevated at low pH levels and ω 3 PUFA increased as the pH was lowered from 8.5 to 6.5. The investigations show that algal productivity is considerably higher in the continuous culture system than in any of the other culture systems available.     

A survey of mineral status of soil,feeds and cattle in the Selale Ethiopian highlands. II. Trace elements

Summary The trace element status of crossbred Friesian × zebu (Boran) and local zebu cattle in the Selale highlands of Ethiopia was evaluated during the rainy and dry seasons of 1989 and 1990 in terms of the trace element content of soils, feeds, blood plasma and faeces on 25 randomly selected farms. Liver samples from animals of local breeds from a slaughter house were collected during the rainy and dry seasons of 1990 and analysed.Soil Fe and Mn were found to be high. Iron contents of all feeds were extremely high and Mn contents were higher than the dietary requirement. A large proportion of feed samples were deficient in Cu and zinc. There were wide variations in the concentrations of these elements among the soil and feed samples.Blood plasma Fe (P<0·001) and Cu (P<0·01) values differed significantly between the years. Plasma samples collected during 1990 contained lower mean Cu than 1989. The effect of season was statistically significant (P<0·001) for all the trace elements. More than half of the animals were found to have low plasma Cu and Zn during the rainy season. Due to lack of any correlations between soil, pasture and blood plasma it is suggested that analyses of soils and pasture are not reliable for assessing the Fe, Cu and Zn status of grazing cattle in the highlands. Analyses of liver and blood appear to provide better indices.

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Un Estudio Del Estado Mineral Del Suelo, Alimentos Y Ganado En Las Tierras Altas Selale De Etiopia: Microelementos

Resumen Se evaluó el contenido de microelementos en suelos, alimentos, plasma sanguíneo y heces en 25 fincas escogidas al azar. El ganado utilizado como unidades experimentales fueron cruces de Friesian × Cebú (Boran) y ganado Cebú local, en las tierras altas de Selale en Etiopía; la evaluacion tuvo lugar durante las estaciones lluviosas y secas de 1989 y 1990. Se analizaron también muestras de hígado tomadas de ganado en el matadero durante la estación lluviosa y seca de 1990.El Fe y Mn se encontraron altos en los suelos. El contenido de hierro de todos los suelos fue extremadamente alto, como también el contenido de Mn. Sin embargo, una gran proporción de alimentos fue pobre en Cu y Zinc. Estos elementos variaron ampliamente en el suelo y muestras de alimentos.Los valores de Fe plasmático (P<0·001) y de Cu (P<0·01) difirieron ampliamente entre años. Las muestras plasmáticas colectadas durante 1990 contuvieron menos Cu que en 1989. El efecto de la estación fue significativa estadísticamente (P<0·001) para todos los elementos traza.Más de la mitad de los animales se encontraron con niveles de Cu y Zn plasmáticos bajos durante la estación lluviosa. Debido a la carencia de correlación entre suelo, pasturas y plasma sanguíneo, se sugiere que el análisis de pasto y suelo no son confiables para estudiar valores de Fe, Cu y Zn en ganado en pastoreo en las tierras altas de Etiopía. Aparentemente el análisis de hígado y sangre provee mejores índices.

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Enquête Sur La Teneur En Éléments Minéraux Des Sols, Des Aliments Du Bétail Et Des Bovins Dans Les Hautes Terres De Selale Éthiopien. II. Oligo-Éléments

Résumé Les teneurs en oligo éléments des croisements Frison x Boran et zébu locaux dans les Hautes Terres du Selale éthiopien ont été estimées durant les saisons sèches et humides des années 1989 et 1990 en termes de contenu spécifique des sols, des aliments du bétail, du plasma sanguin et des fèces sur 25 fermes sélectionnées au hasard. Des prélèvements de foie sur des animaux de race locale ont été effectués à l'abattoir pendant les saisons sèches et humides de 1990 en vue de leur analyse. Des taux éléves ont été trouvés pour le fer et le magnésium du sol. Les teneurs en fer de tous les aliments étaient extrêmement élevées et celles en magnésium étaient plus élevées que les besoins alimentaires. Une forte proportion des échantillons d'aliments étaient carencés en cuivre et en zinc. Les variations des concentrations de ces élements dans les prélèvements de sols et d'aliments se situaient dans une large échelle. Les valeurs du fer plasmatique sanguin et celles du cuivre différaient de façon significative selon les années (P<0,001 etP<0,01 respectivement). Les prélèvements de plasma collectés en 1990 contenaient en moyenne moins de Cu qu'en 1989. L'effet de la saison etait statistiquement significatif pour (P<0,001 pour tous les oligo éléments. Pour plus de la moitié des animaux, les teneurs plasmatiques en Cu et Zn étaient peu élevées pendant la saison des pluies. En raison du manque total de corrélations entre le sol, le pâturage et le plasma sanguin, il est à penser que les analyses des sols et des pâturages ne sont pas fiables pour la détermination des teneurs en fer, cuivre et zinc du bétail au pâturage dans les Hautes Terres. Les analyses du foie et du sang apportent des indications plus satisfaisantes.

     

The contribution of shallow groundwater by safflower (Carthamus tinctorius L.) under high water table conditions, with and without supplementary irrigation

Lysimetric experiments were conducted to determine the contribution made by groundwater to the overall water requirements of safflower (Carthamus tinctorius L.). The plants were grown in 24 columns, each having a diameter of 0.40 m and packed with silty clay soil. The four replicate randomized complete block factorial experiments were carried out using different treatment combinations. Six treatments were applied during each experiment by maintaining groundwater, with an EC of 1 dS m^?1, at three different water table levels (0.6, 0.8 and 1.10 m) with and without supplementary irrigation. The uptake of groundwater as a part of crop evapotranspiration was measured by taking daily readings of the water levels found in Mariotte tubes. The supplementary irrigation requirement for each treatment was applied by adding water (EC of 1 dS m^?1). The average percentage contribution from groundwater for the treatments (with and without supplementary irrigation under water table levels of 0.6, 0.8 and 1.10 m) were found to be 65, 59, 38% and 72, 70, 47% of the average annual safflower water requirement (6,466 m³ ha^?1). The increase in groundwater depths under supplementary irrigation treatments from 0.6 to 0.80 and 1.10 m caused seed and oil yield reductions of (7, 23.10%) and (48.23, 65.40%), respectively.     

Land-use change and carbon stocks: A case study, Noor County, Iran

Land-use changes and land cover strongly influence carbon stock and distribution within ecosystems. Changing the land-use from natural forest to other land-uses has been more rapid in the past few decades than at any time in Iran’s history. In this study, we investigated the effects of changing the land-use from natural forest to other land-uses on carbon stocks in northern Iran. We selected five sites for this study: (I) a natural forest, (II) an agricultural field and (III) plantations of three different species (Alnus subcordata. L, Acer velutinum.Boiss and Cupressus sempervirens). We examined the effects of land-use changes on: (I) soil carbon stock (0–50 cm depth), (II) biomass and carbon content of grassy vegetation and litter and (III) above- and below-ground biomass C in trees. Soil C stock was higher under A. velutinum and C. sempervirens whereas it was lower under A. subcordata and agricultural sites. Biomass and C content of grassy vegetation were significantly higher at A. velutinum and C. sempervirens plantations. However, litter biomass and C content were significantly higher at the natural forest site. Natural forest had the highest amount of C content in above- and below-ground biomass. Total ecosystem C stocks declined following land-use changes.