PHYTOSOCIOLOGICAL ATTRIBUTES OF WEED FLORA IN MAJOR CROPS OF NORTH COASTAL ANDHRA PRADESH, INDIA

The cultivated fields of North Coastal Andhra Pradesh region are infested with a large number of weeds that result in heavy crop yield losses. Rice is the most dominant crop of this area. The rice variety i.e. Srikakulam sannalu (RGL-2537) having crop duration of 150-165 days (Srikakulam district), the groundnut crop variety i.e. JL-24 having crop duration of 105-110 days (Vizianagaram district) and sugarcane crop variety i.e. Viswamitra (87A 298) having a duration of 10 months (Visakhapatnam district) were selected for the phytosociological investigations. The studies were conducted before weeding during Kharif season (i.e. June-October, 2007). Random quadrat method was adopted for studying the phytosociological attributes of the weeds. In each field site, 20 quadrats of 100 cm2 size were laid down and hence a sum of 60 quadrats were randomly thrown for each crop in the three districts. A total of 200 herbaceous plant species (i.e. 65 in rice, 78 in sugarcane, and 57 in groundnut) occurred in the three major cropping systems. This number constitutes 70.8% of the total number of the weed species of the world. Wolffia globosa was most abundant weed species in the rice fields, Cyperus rotundus was the most important species in sugarcane and groundnut crops. The majority of the weed species encountered in the crop fields were recorded as A, B, C, and D frequency classes and hence the weed vegetation was declared as heterogeneous. Phytosociological attributes and ecology of the weeds of this region has to be communicated to the concerned public and private organizations, and farmers for effective weed management and better crop yields. It is also helpful for designing a suitable weed control technology for the studied area.