Effect of nitrogen and phosphorous fertilizers on forage production of saltbush (Atriplex canescens) under saline conditions

The present study was aimed to elucidate the effects of nitrogen and phosphorous fertilizers on A. Canescens as a forge halophyte plant. The treatments; three rates of nitrogen fertilizer (0, 25 and 50 kg N ha-1 in the form of ammonium nitrate) and phosphorous fertilizer (0, 25 and 50 kg ha-1 in the form of triple superphosphate), arranged in a split plot design with three repelication. Each experimental unit consisted a pot with 1 m height and 45 cm diameter. Plants were irrigated with irrigation water salinity of 14 dS m-1 using bubler irrigation system. The results showed the negative effect of age on forage production. At first year, 19.2 ton ha-1 of shoot fresh weight was produced but it was decreased to 14.8 and 11.49 ton ha-1 at second and third years, respectively. In addition, the results showed the positive effect of nitrogen fertilizer on forage production. Application of nitrogen at a rate of 25 and 50 kg ha-1 increased shoot fresh weight from 7.91 to 15.13 (91%) and 21.85 (176%) ton ha-1. While the same trend was found for total dry weight, leaf and stem dry weight, nitrogen application had not significant effect on leaf to stem ratio. It should be noted that phosphorous application had not significant effect on A. Canescens performance. Overall, application of nitrogen fertilizer at a rate of 50 kg ha-1 is recommended for improving A. Canescens performance irrigated with saline waters with electrical conductivity of 14 dS m-1. The results showed that forage production significantly decreased with increasing plant age. While fresh forage equaled to 19.21 ton/ha at first year, it decreased to 14.18 and 11.49 ton/ha at second and third year of experiment. While application of nitrogen was essential for halphyte production, application of phosphorous fertilizer did not affect plant performance. Applicaton of nitrogen at a rate of 25 and 50 kg/ha urea increased forage productin at a rate of 91 and 176 percent respectively. Overall, it was concluded that productin of halophytes such as Atriplex canescens under saline calcareous soils of Yazd province for forage productin is possible and urea fertilizer improves plant performance.