Numerous plant species are considered weeds in agronomic cropping systems. Weeds have many attributes undesirable to crop producers, not the least being the ability to reduce crop yields through competition for resources such as sunlight, water, nutrients, and space. Weeds also may harbor insects and provide a host for certain plant pathogens. Some weed species, such as wild garlic and eastern ...

The critical period for weed control (CPWC) is the period in the crop growth cycle during which weeds must be controlled to prevent unacceptable yield losses. Field studies were conducted in 2005 and 2006 in the University of Birjand at the south east of Iran to determine CPWC of corn using a randomized complete block design with 14 treatments and four replications. The treatments consisted of ...

In order to determine the responses of morphological characteristics, yield and yield components of rapeseed (Brassica napus L.) to plant density and weed interference duration, a factorial experiment was conducted using a randomized complete block design with 3 replications at the Rice Research Institute of Iran (RRII) in Rasht, in the 2008 growing season. The factors comprised plant density a...

Charles Darwin [1,2] handed us a picture of competition as a constructive process responsible for adaptation to the environment, as well as the evolution of striking sexual displays and weapons. Darwin believed that sexual competition promotes adaptation by helping to weed out poor-quality males from the breeding pool and bringing about assortative pairing between high-quality males and females.

Weed interference in annual cropping systems can be highly variable from year-to-year, as well as spatially heterogeneous. These factors have confounded efforts to develop simple methods for predicting competitive outcomes early in the growing season. A 2-year study was conducted with maize in competition with four annual weed species (Setaria faberi, Abutilon theophrasti, Chenopodium album and...

weed's behaviors differ in a multiweed-crop competition system compare to a mono weed-crop competition system. the present investigation was carried out in mashhad, iran, to study the effect of weeds, which emerged naturally in a multi species community along side with melon, on quantitative and qualitative characteristics of the crop during 2007. thirty five plots were selected randomly in a g...

Two factors limiting successful recruitment of planted blue oak (Quercus douglasii) seedlings are dry soils and animal damage. Many approaches have been used to mitigate these factors including several types of protective cages and alternative methods of weed control. This study examined how treeshelters, screen cages and varying intensities of weed removal affect the establishment and growth o...