Intensive forest management led to elevated losses of nitrogen from a recently harvested loblolly pine plantation in North Carolina. Measurements of nitrogen-15 retention in the field demonstrated that microbial uptake of nitrogen during the decomposition of residual organic material was the most important process retaining nitrogen. Management practices that remove this material cause increase...

Nitrogen management practices have an effect on crop yields but they can also have a negative impact on the environment. Practices such as banding fertilizer and/or split-applying total nitrogen needs per acre offer a more efficient use of nitrogen by significantly reducing nitrate leaching potential. Heavy rains occurring when plants are small and nitrogen demands are low can also increase nit...

Nitrogen availability is a major factor determining plant growth and productivity. Plants acquire nitrogen nutrients from the soil through their roots mostly in the form of ammonium and nitrate. Since these nutrients are scarce in natural soils, plants have evolved adaptive responses to cope with the environment. One of the most important responses is the regulation of nitrogen acquisition effi...

A numerical model of nitrogen uptake and growth was developed for the temperate seagrass Zostera marina L. Goals were to evaluate the relative effects of light and nitrogen availability on nitrogen uptake and partitioning between leaf and root tissue. and to estimate nitrogen concentrations in the sedmen t and water column required to saturate growth. Steady-state predichons are quite robust wi...

Optimal allocation of leaf nitrogen maximizes daily CO(2) assimilation for a given leaf nitrogen concentration. According to the hypothesis of optimization, this condition occurs when the partial derivative of assimilation rate with respect to leaf nitrogen concentration is constant. This hypothesis predicts a linear increase of assimilation rate with leaf nitrogen concentration under constant ...

The present study was undertaken to compare the nitrogen content of human feces as determined by the Kjeldahl technic and the micro-Dumas method as utilized in the automated Coleman nitrogen analyzer. The standard deviation between duplicate determinations of the same sample was 0.06% nitrogen in the case of the nitrogen analyzer and 0.02% nitrogen for the Kjeldahl method. The standard deviatio...

Abstract—Liquid spray heat exchanger is the critical equipment of temperature regulating system by gaseous nitrogen which realizes the environment temperature in the range of -180 °C~+180 °C. Liquid nitrogen is atomized into smaller liquid drops through liquid nitrogen sprayer and then contacts with gaseous nitrogen to be cooled. By adjusting the pressure of liquid nitrogen and gaseous nitrogen...

This paper presents the effect of soil supplementation with urea and magnesium on nitrogen uptake and its utilization by two different types of hybrid maize cultivars. Based on the results of 3-year fertilization studies, it was shown that for average volume of grain yield of maize, nitrogen content in grain dry matter and nitrogen uptake with its yield was significantly determined by the doses...