1. Agriculture is a major contributor of non-point source pollution to surface waters in the midwestern United States, resulting in eutrophication of freshwater aquatic ecosystems and development of hypoxia in the Gulf of Mexico. Agriculturally influenced streams are diverse in morphology and have variable nutrient concentrations. Understanding how nutrients are transformed and retained within ...

background and objectives: the quefts model is using for optimizing fertilizer managements in crops, but it has not been used in iran yet. quefts accounts for interactions among npk affecting the ie of n, p and k and allows differentiation according to different yield levels targeted. it is necessary to determine crops parameters before application the model in the studying area. the first step...

The objectives of this study were 1) to compare Sonoran Desert streams with other streams in terms of retention efficiency of nitrate; 2) to examine the effects of a flood on nitrate retention and to determine which factors control nitrate retention in the surface stream subsystem in Sycamore Creek, Arizona; and 3) to compare the short-term nutrient addition technique with computations based up...

mycorrhizal symbiosis increase nutrient uptake and enhance plant growth by elaborating root system. the positive effects of mycorrhizal symbiosis on the growth, physiology and ecology of various plants have been recognized. the symbiotic relations between mycorrhizal fungi and date palm with regard to nutrient uptake by this plant have not yet been explored and studied in iran. this project was...

ABSTRACT- The effects of iron (Fe) and zinc (Zn) treatments on the growth and nutrient composition of chickpea were studied in a greenhouse experiment arranged in a completely randomized design. While the application of Fe decreased mean shoot dry weight of chickpea, that of Zn had no significant effect on chickpea shoot dry weight. Increasing Fe levels drastically decreased Mn concentration an...

Many physiological processes in phytoplankton, including nutrient uptake, vary on a number of temporal scales. Experiments show that the daily cycle in irradiance affects nutrient uptake rates. We used a Droop-based model of resource competition to investigate how diel variability in nutrient uptake influences phytoplankton competition and community structure. The analytical approximation we de...

Mycorrhizal associations are generally favourable for vascular plants in nutrient-poor conditions. Still, non-mycorrhizal plants are common in high arctic and alpine areas, which are often poor in nitrogen and phosphorus. The relative proportion of mycorrhizal plants has been found to decrease along with increasing altitude, suggesting that the advantage of the mycorrhizal symbiosis may change ...