A study on crop weed competition in field crops

A weed is important biological factor in crop production that cause yield reduction and it contributes around 45% of crop yield loss. Weed life cycle similar with crops and some weeds have same morphological character with crop plants and farmers difficult to identify it at early crop growth stage. So the main concern of this review is to know critical time for crop weed competition, effect of weeds on plant growth and development, physiological changes, yield performance weeds studies includes density, different weed floras and its dry matter accumulation, finally why and purpose of weeds compete with crops. Increasing initial weed competition period reduces crop germination and at later stage of crop growth reduces the growth and development parameters like plant height, dry matter accumulation, leaf area index, physiological parameters like CGR, RGR, NAR, Chlorophyll content, leaf thickness are reduces. Similarly, increasing weeds competition reduces crop yield drastically.