even though some research has shown no negative economic impacts (Daliparthy et al., 1995; Lloveras et al., Perennial forages like alfalfa (Medicago sativa L.) or various pe2004). Reasons for avoiding manure applications to alrennial grasses, which are cut several times during the growing season, falfa include increased weed incidence, stand damage could provide an alternative land base and tim...

Crop rotation is one of the oldest and most important approaches to the con­ trol of nematodes that feed on the roots of annual crop plants. The value of rotations often was recognized long before their effects upon the dynamics of nematode populations and communities were considered. As specific nema­ tode problems were identified and their economic importance demonstrated, attention usually w...

Nitrogen is abundant in the earth's atmosphere but, unlike carbon, cannot be directly assimilated by plants. The limitation this places on plant productivity has been circumvented in contemporary agriculture through the production and application of chemical fertilizers. The chemical reduction of nitrogen for this purpose consumes large amounts of energy and the reactive nitrogen released into ...

Nitrogen-fixing, plant-growth promoting bacteria are arguably the biotechnological tool of highest potential to improve agricultural productivity in short term. Nitrogen fixation and phytohormone production by these bacteria have been considered the most important factors for plant growth promotion. However, the underlying mechanisms responsible for productivity increases by associative bacteri...

The availability of Haber-Bosch nitrogen (N) has permitted agricultural intensification and increased the productive capacity of agroecosystems; however, approximately 50% of this applied fertilizer N is lost from agricultural landscapes. Extensive efforts have been devoted to improving the N use efficiency of these systems. Diversified crop rotations using cover crops to provide a variety of e...

Conversion of inorganic nitrogen by mutualistic nitrogen-fixing bacteria is essential for plant growth and reproduction, as well as the development of chemical and mechanical defenses. It is unclear, however, how these bacteria alter cooccurring symbioses at higher trophic levels; e.g., extrafloral nectary (EFN) induction, in response to herbivory, to attract defensive mutualists. We hypothesiz...

Plant viruses have an enormous negative impact on agricultural crop production throughout the world, and, consequently, agronomists and plant pathologists have devoted considerable effort toward controlling virus diseases during this century. Prior to the advent of genetic engineering, traditional plant breeding methodology was sometimes successfully applied to develop resistance to viruses of ...

garlic and onion are very important crops which are cultivated especially in autumn season in jiroft region, southeast of iran. one of the limiting factors for development of cultivation of these crops is fungal diseases such as leaf spot and blight. for identifying the causal agents of this disease, numerous onion and garlic fields were surveyed during 2001-2003 and infected samples were colle...