Determining of the suitable sowing and harvest periods of the plants according to regions is of great importance for a profitable and high yielding roughage production. However, there is no study on the Mountain spinach (Atriplex nitens Schkuhr) considered as alternative forage resource based on different sowing and growth periods in field conditions. With the present study, the effect of different sowing (mid-April, late-April, early-May, mid-May) and harvesting periods (end of vegetative period, beginning of flowering, full flowering period) on herbage yield and components was tried to be determined. For this purpose, a study was planned according to randomized complete block in split plots with three replications in Iğdır irrigated conditions in 2019 and 2020. The results showed that the years (except plant height, number of branches and crude protein yield), sowing times and harvest periods (except crude protein yield) had a significant effect on the parameters studied. As a result of the study, it was determined that the examined parameters increased as the harvest period was delayed and decreased as the sowing time was delayed (except leaf ratio). In addition, in the correlation analysis; It was determined that there was a very significant and positive relationship between all the examined variables (except leaf ratio) and dry herbage yield. As a result, it was concluded that sowing should be done at the first opportunity (mid-March) and harvesting should be done at the full flowering period for high fresh herbage (14503.0-16947.2 kg da-1), dry herbage (4489.1-4906.9 kg da-1) and crude protein yields (386.1-469.3 kg da-1).