Investigation of the Effect Dryness Stress and Deficit Irrigation on Water Use Efficiency and Morphophysiological Factors in Two Festuca Grass Varieties

According to expantion of urbanization, it is necessary to create green space as the most important environmental factor in moderate cities. However in recent decades, shortage of water resources is one of the problems facing the expansion of green space especially grass type. Therefore, the application of management methods such as deficit irrigation is very important. Development of green space requires sufficient water supply and according to the climatic conditions of our country, finding alternative methods and resources for effective irrigation and utilizing all available capacities is one of the main goals of municipalities and water organizations.

This research was performed in a greenhouse with an area of 120 square meters located in the college of Agriculture of Shiraz university with longitude 52032’, latitude 29036’,1810 height above sea level, and in flower pots with dimensions of 30 * 30*30 in order to investigate the effect of water stress in the traditional irrigation method on morpho-physiological factors and water productivity in two variety long grass. The research was in the form of split plots based on a random full canton with three replication and three levels (%100 per) (w1), (%75 per) (w2), (%50 per)(w3) of water requirement. The grass used in this design is Festuca, arundinacea Schreb with two variety named Asterix and Talladega which are considered as cold grasses and has a root depth of 15-20 cm. The first 3 cm of sand (to create drain conditions) was placed in the bottom of the flower pot, and then 24 cm of soil was poured on it and compacted until it reached the required density. On April 10, two variety of grass seeds were poured manually on the pots (10 grams of seeds per pot). Then, 100 gr of rotten and screened animal dung was poured on the seeds in each flower pot and irrigated with a hose by a traditional (manual) system. Early cultivation was done manually due to the application of more water and the establishment of grass. In this way, every day for a week, two to three times irrigation and after the seeds germinate (10 days after cultivation), once-daily irrigation and until the seeds germinate completely (20 days after cultivation), the irrigation period was once between 7 until 15 days, and then water stress was imposed. The first grass mowing was done after the grass was completely established (30 days after cultivation). Also, in order to compensate for the shortage of nutrients in the soil after two months (July) 6 gr /m2  of urea fertilizer (0.54 gr/ m2  to each flower pot) was applied. The onset of stress was two months after cultivation (July 10), and the duration of stress was 45 days. To determine the water requirement a separate flowerpot among the other flowerpots was located, and provide the moisture to FC level. Every other day, the water lost by this flower pot compared to the initial weight (FC), the same amount of water was given to the flowerpots with 20% more as for the leaching requirement.

Analysis of experimental data was performed by SAS 9.4 statistical software, and Duncan’s multiple range experiments at 5% level were used to compare the means, at the level of 5% probability. Results and data analysis was investigated under water stress in two varieties.Dryness stress and water use efficiency: Water productivity in both varieties of grass and in different irrigation treatments did not change significantly at 95%. So decline in the amount of irrigation water has not affected water productivity.Interaction of dryness and grass quality: The results showed that water stress and the interaction of water stress and grass variety on the appearance quality of grass were not significantly different at 95% and in the second ten days of August, the appearance quality was more desirable than in the first half.Interaction of dryness and relative leaf water content of leaf: The relative water content of the leaf was weekly measured during the stress period. The results of comparing the mean relative water content (RWC) of leaf under water stress in two types of Festuca grass showed that the effect of water stress interaction was significant in Asterix grass variety on the relative water content of leaf at 95% level. The relative water content of the leaves is a good index of the water situation of the leaves, and its reduction in the leaves causes wilting and reduces the freshness and appearance quality of the grass and reducing the relative water content of the leaf has not affected the appearance quality of the grass.Interaction of dryness and leaf growth rate: The leaf growth rate was measured during the stress period (monthly) in three ten-day periods (August). The results of comparing the means showed that the effect of water stress interaction and two variety of grasses on leaf growth rate was not significant during the first ten days. In the second ten days, the effect of water stress was significant in both Asterix and Talladega grass and growth rate in irrigation treatments of 75 and 50% (percentage) of full irrigation was significantly different from full irrigation.

The results of this study showed that deficit irrigation could increase water use efficiency without reducing the quality of green cover. With less water consumption (half full irrigation), the appearance quality of the grass will be well maintained. The relative water content of the leaf decreased as dryness stress progresses and causing changes in the cell membrane and thus increasing electrolyte permeation from the cell. Considering that dryness stress has not reduced the appearance quality of the grass, reducing the relative water content of the leaf has not affected the appearance quality of the grass. Generally, the growth rate in all three decades was maximum in dryness stress 75% (percentage), which indicates the high photosynthesis of the plant in this stress.