Soil organic carbon has been the most important soil quality measurement factors and has intense relation with soil physical, chemical and biological characteristics. Organic matter and its components are important factors of soil aggregates constitution and stability and play significant role in its structure.So, this research has been done for achieving this purpose. This area is arounding sa...

Between 1700 and 1850, English grain yields were substantially higher than those attained in other countries. It is widely believed that yields were constrained by the availability of nitrogen, and that supplies of nitrogen were effectively limited to animal dung produced on the farm. This paper presents the first systematic analysis of off-farm sources of nitrogen, such as urban and industrial...

In Klebsiella aerogenes P-galactosidase and histidase are subject to strong catabolite repression by glucose in the presence of a good source of nitrogen. Under conditions of nitrogen limitation, the catabolite repression of histidase is relieved, while fi-galactosidase remains strongly repressed. Exogenous adenosine 3’, 5’-monophosphate relieves the catabolite repression of both histidase and ...

The responses of gas exchange and water use efficiency to nitrogen nutrition for winter wheat were investigated under well-watered and drought conditions. The photosynthetic gas exchange parameters of winter wheat are remarkably improved by water and nitrogen nutrition and the regulative capability of nitrogen nutrition is influenced by water status. The effects of nitrogen nutrition on photosy...

the leaf nitrogen content is generally accepted as an indicator of food quality and as a factor affecting host selection by phytophagous insects. the alate pea aphids (acyrthosiphon pisum harris, aphididae) were given a choice among non-nodulated pea plants (pisum sativum l.) supplied with one of four nitrate-n levels (0, 3, 15 and 30 mm). when whole plants were exposed to aphids for 7 days, th...

abstract in this study different proportions of nh4+ and no3- in the growth medium on plant growth were investigated in hydroponic greenhouse experiments. the objectives of these studies were to investigate if ammonium (nh4+) stress in cucumber, a species sensitive to nh4+ toxicity, can be alleviated by matching the nitrogen supply rate to the plant nitrogen demand. ammonium was applied at a re...