Evaluating the Effect of Salinity Stress Due to Irrigation Water and Soil on Growth Characteristics of Purple Nutsedge (Cyperus rotundus L.)

Salinity is one of the most important abiotic stresses that cause severe effects on crop production around the world. Estimates indicate that more than 800 million hectares of arable lands in the world are affected by salinity. Salinity impacts on various aspects of growth from germination to seed production in plants. Plants′ responses to salinity, however, are different and depend on the toxicity, osmotic potential, as well as the stress duration. Purple nutsedge (Cyperus rotundus L.) is one of the noxious weeds. This weed belongs to sedge family, and is a C4 perennial plant which reproduce by sexual (seeds) and asexual (tubers and rhizomes) means. It can cause tremendous damage on summer crop fields such as onion, potato, maize, sunflower, and so on. Evaluation of weed growth responses to saline condition came about by water and soil can provide for us very important information by which we choose appropriate weed control strategies. Since a few experiments have been evaluated growth characteristics of purple nutsedge under salinity stress, this study was conducted to evaluate the salinity effects on growth characteristics of purple nutsedge.
Material and To evaluate the effect of irrigation water and soil salinity on growth characteristics of purple nutsedge, two separate experiments were conducted in a randomized complete block design with three replications in the greenhouse of Faculty of Agriculture at University of Birjand in 2013. The first experiment contained five salinity levels of water including 0, 3, 5, 7 and 9 dS.m-1 and in the second experiment, there were five salinity levels of soil including 1, 3, 5, 7 and 9 dS.m-1. The salinity levels of water were prepared through solving a certain amount of NaCl in water based on this equation: NaCl (mg. L-1) =EC (dS.m-1)×640.. Following determination of soil electrical conductivity, soil salinity levels were prepared by adding NaCl to the soil based on saturation moisture percent and field capacity. A tuber of purple nutsedge was planted at 2.5 cm depth in each pot. Experiments were terminated at the end of the vegetative growth stage of purple nutsedge (105 days after emergence). Measured traits were plant height, stem number per pot, leaf area, and tuber number per pot, shoot and underground dry weight. After collecting the data, ANOVA was performed using Genstat Ver. 9 and mean comparisons were performed using Fisher's least significant difference test at 5% significant level. In order to evaluate purple nutsedge growth response to salinity stress, an exponential decay model was used; Y=a*exp(-b*x), thta in this model, a and b represents the maximum amount of studied traits and the slope of curve according to the model estimation, respectively.
The results of both experiments showed that the growth characteristics of purple nutsedge (plant height, stem number per pot, leaf area, tubers number per pot, shoot and underground dry weight) were significantly affected under soil (P