Possibility of quinoa production under South-Khorasan climatic condition as affected by planting densities and sowing dates

Introduction
Introducing of new crops which are adapted to environmental stresses is one of the most effective methods for sustainable crop production and food security in arid regions. Accordingly, the possibility of quinoa (Chenopodium quinoa Willd) production as a drought- and saline-tolerant, pseudocereal has high importance (Bagheri, 2018). This plant is able to develop even in regions where the annual precipitation is between 200–400 mm. The planting season of quinoa varies from August in the Andean highlands, extending through December, and in some areas from January to March. Quinoa sowing density may vary according to the region. For example, it has been reported to range from 0.4 to 0.6 g m2 in Bolivian Altiplano, and from 0.8 to 1.4 g m2 in Ecuador (Jancurova et al., 2009; Ruiz et al., 2014). Considering the possibility of high adaptation of quinoa to the dry climatic conditions of Iran, the aim of this study was to evaluate the possibility of its cultivation in Birjand region, and in the first step the effects of planting date and density were investigated on its growth and yield.

Materials and Methods
In this research the effects of sowing date (5th, May, June and July) and plant density (15, 30, 45 and 60 plant per m-2) was studied on vegetative and reproductive growth of quinoa (Titicac cultivar) using factorial experiment based on a randomized complete block design, with three replications, in Birjand, Iran, during 2017. Planting was done in rows with 30 cm distances and the variable intervals on the row based on the related density. Irrigation was applied in time intervals of 10 days and 130 kg ha-1 Urea (46% pure N) also was used during plant growth. In the last of vegetative phase six plants were sampled randomly and then some vegetative (plant height, plant dry weight, number of lateral branches) and reproductive (panicle number, length and dry weight, grain number per plant, 1000-grain weight) traits were measured. The remained plants were used to measure grain yield, biological yield and harvest index. Data analysis was done using SAS 9.2 and means were compared by LSD test in 5% level of probability.

Results and Discussion
The simple and interaction effects of planting date and density was statistically significant on most vegetative and reproductive indices of quinoa including plant dry weight, number of lateral branches per plant, biological yield, number of panicle (cluster) per plant, length and weight of panicle, grain number per plant and grain yield. Plant dry weight decreased with increasing plant density up to 60 plant per m2 and planting in July. The number of panicles (cluster) per plant decreased due to the increase in plant density from 15 to 60 plant per m2 (by 19%) and movement from spring cultivation to summer planting (by 75%). This decrease was somewhat moderated by increasing the number of sub-cluster per cluster. The highest number of grain per plant (806 grain) was obtained in density of 15 plant per m2 and planting in early May. The highest and the lowest grain yields were obtained from May planting date with a density of 45 plants per m2 (380 kg ha-1) and planting in July with a density of 15 plants per m2 (25 kg ha-1), respectively. Against grain yield, planting in July had no negative effect on biological yield, so that, its maximum value (1968 kg ha-1) was obtained from mentioned planting date and density of 45 plant per m2. The main reason for reduction of grain yield in June and July planting dates was the occurrence of high temperatures during pollination period of the plant.

Conclusions
Overall, density of 45-60 plants per m2 and sowing of quinoa in May brought the best conditions for its growth and yield. However, grain yield in this treatment was also considerably lower than the actual yield of the plant, and therefore evaluation of other autumn, winter and summer planting dates is require. Observations showed that the approach of the quinoa pollination period to a high temperatures, disturbed pollination and consequently grain production declined sharply.
Keywords: Harvest index, Lateral branch, Panicle, Plant height, Grain yield.