sclerotinia stem rot (ssr), caused by sclerotinia sclerotiorum, is one of the most important diseases of canola (brassica napus) in golestan province, the leading canola producer in iran. in order to assess the yield loss of canola caused by ssr, 80 fields were surveyed in four different regions of the province (gorgan, ali abad, kalaleh and gonbad) during 2006-2007, and ssr intensity was recor...

The environmental impacts of land use vary regionally. Differences in geomorphology, climate, landscape structure, and biotope inventories are regarded as the main causes of this variation. We present a methodological approach for identifying regional responses in land use type to large-scale changes and the implications for the provision of habitat for farmland birds. The methodological innova...

1. Introduction Systems approach has been used by engineers since the 1950's for the study of complex and dynamic processes but their use by scientists working in biological fields is relatively recent. A system is defined as any well delineated part of reality which may contain a number of interrelated elements forming the systems structure. These functioning components interact in various way...

abstract radiation, water and co2 are three major resources requirement for crops growth and development and within a wide range, increasing each of them would increase the biosphere productivity. higher usage of fossil fuels is increasing the atmospheric co2 and according to known crop physiological functions, such conditions should increase the crops production. however there is a possibility...

crop simulation models are mathematical representations of plant growth processes as influenced by interactions among genotype, environment and crop management. using crop simulation models can be an efficient complement to experimental research. models are being used to understand the response of crops to possible changes in crop, cultural management and environmental variables.while there are...

H Harvest index (HI), ratio of seed yield to aboveground dry matter, is a very important parameter for estimating seed yield in several crop models. In this study, the importance, definition, variability and estimation methods of HI in crop models were discussed. HI estimation methods are categorized into two groups including: (i) complex methods that estimate HI from the beginning of seed gro...

The next advance in field crop productivity will likely need to come from improving crop use efficiency of resources (e.g., light, water, and nitrogen), aspects of which are closely linked with overall crop photosynthetic efficiency. Progress in genetic manipulation of photosynthesis is confounded by uncertainties of consequences at crop level because of difficulties connecting across scales. C...