Purple nutsedge (Cyperus rotundus) was one the most widely distributed and troublesome perenial weeds around the world. It infested and cost severe yield losses in both paddy rice and upland crops in the Kingdom of Saudi Arabia. The field experiments were conducted at Al-Hassa research farm of the Chinese Agricultural Technical Team to see (1)the influence of cutting period and time to the population density of purple nutsedge; (2) the influence of purple nutsedge to different growth condition and (3) the seasonal dynamics variation of purple nutsedge.
It was found that continuous cutting to above-ground parts were very effective in the controlling of purple nutsedge by depleting nutrients deposited in the tubers. The population of purple nutsedgt depressed to 1/3-1/2 after 3-4 cutting compared to non-cutting treatments, while two cutting each month were taken. The plant height and percentage of water content were higher in purple nutsedge grown on paddy field and shaded place. But plants grown on upland and shining place had higher dry weight and more total green leaves. In general, germination of tuber began on March, then the growth of above-ground parts increased rapidly and until October or November, the density decreassed fast to almost zero. The most density population could be found on the months of June, July, August and September. On the other hand, the formulation of tubers was from September to January. The dry weight of tuber began to decrease, when the plant began to germinate on February. There, however, were a lot of tubers dorminated in the soil during summer season. Most of purple nutsedge flowered from July to October. Flowering during winter time was seldom discovered.