The Effects of Partial Root Zone Drying and Growing Bed on Yield and its Components of Quinoa (cv. Titicaca)

Since the agriculture is the main water consumer, it is necessary to increase water use efficiency. As a management practice, deficit irrigation strategy is applied to cope with water shortages, especially during drought periods. A greenhouse experiment was conducted to investigate the impact of water and salt stress on Quinoa plants (Chenopodium quinoa Willd.), Aly et al (2) showed that quinoa plants can tolerate water stress (50% FC) when irrigated with moderately saline water (T1 and T2, respectively). The results of some studies showed that Amaranth was the most responsive plant to water. Quinoa showed the best performance in the treatment with the upper-middle water level among the other evaluated species. Millet showed thermal sensitivity for cultivation in the winter, making grain production unfeasible; however, it showed exceptional ability to produce biomass even in the treatment with higher water deficit. Water stress can affect plants by reducing the plant height, relative growth rate, cell growth, photosynthetic rate, and the respiration activation. Cultivated plants have several mechanisms of adaptation to water deficit, but the responses are complex and adaptation is attributed to the ability of plants to control water losses by transpiration, which depends on the stomatal sensitivity and greater capacity of water absorption by the root system, among other factors. In PRD method, half of the root zone is watered and the other half is kept dry intermittently. The objective of this research was to study yield and yield components of Quinoa (Chenopodium quinoa Willd.) Titicaca cultivar, using PRD irrigation method in three growing bed, under greenhouse conditions.

This research was conducted to study the effects of water stress on yield and its components of Quinoa under the different growing beds in the experimental research greenhouse of Ferdowsi University of Mashhad during 2018. Titicaca cultivar of Quinoa was planted and experimental design was factorial, based on complete randomized design and three replications, included two irrigation managements (FI, full irrigation and PRD, partial root-zone drying method) and three levels of growing bed (S1, silty clay, S2 clay loam and, S3 sandy loam). Research station is located in north-east Iran at 36° 16' N latitude and 59° 36' E longitude and its height from sea level is 985 meters. The seeds of Quinoa were planted at a depth of 1.5 centimeters in the soil of each pot and were irrigated with tap water. Plants were harvested after 4 months and plant height, branches number, panicle number, thousand kernel weights, grain yield, biomass; steam, leaf, and panicle dry weight panicles were measured. Physical and chemical properties of irrigation water and soil were determined before the beginning of the experiment. The obtained data analyzed using the statistical software of SAS (Ver. 9.4) and the means were compared using LSD test at 5 % percent levels.

Results showed that the highest plant height (84.4 cm) was in FI treatment and the shortest plant height (82.5 cm) was in PRD treatment. The highest and the lowest 1000 kernel weights and grain yield were measured in FI (4.0 and 19.7 g per plant) and PRD (3.6 and 17.7 g per plant) treatments, respectively. With a 50 % reduction of water in PRD compared to FI treatment, 1000 kernel weights were decreased by 9.1%. Grain yield was decreased by 10.2% (changing from FI to PRD). The highest and the least grain yield (20.2 and 18.4 g per plant) were obtained in S1 and S2,3 soils, respectively. Silty clay soil with 1000 kernel yield of 4.12 g had higher than clay loam and sandy loam soil, which produced 3.78 g and 3.78 g, respectively.

In general, the effect of the PRD irrigation method on reducing water use in the greenhouse production of Quinoa was positive and recommendable. Silty clay soil with 1000 kernel yield of 4.12 g had higher than clay loam and sandy loam soil, which produced 3.78 g and 3.78 g, respectively.