Effects of Plant Densities and Irrigation Regimes on Yield, Physiological Parameters and Gas Exchange of Sugar Beet Under Transplanting and Direct Seeding Methods

In arid and semi- arid regions selecting the appropriate planting method and irrigation regime along with optimum plant density are three critical factors that affect the yield and physiological characteristics of sugar beet. Therefore, in order to find the optimum field managements in sugar beet cultivation the split-split plot arrangement was used to examine the effects of three irrigation regimes as 100, 75 and 50% of full irrigation (FI), four plant densities as 180,000, 135,000, 90,000, and 45,000 plants ha(-1) and two planting methods as direct seeding and transplanting on physiological growth and gas exchange of sugar beet for two growing seasons at experimental field of Shiraz University, Shiraz, Iran located in a semi-arid environment. Results showed that the mean values of leaf and root dry matter decreased by 41% and 26% from 100%FI to 50%FI, respectively. Transplanting method has more tolerance to water stress than direct seeding and increased the average root dry matter and crop water productivity (WUEET) as 7% and 45%, respectively. The highest value of photosynthesis rate (A(n)), transpiration rate (T-r) and stomata conductance (g(s)) were obtained in transplanting method under the density of 90,000 plant ha(-1) and 100%FI, with no significant difference between I100 and I75 for A(n) and T-r. The highest value of transpiration efficiency (WUEt) and intrinsic water use efficiency (WUEi) were obtained in 75%FI and 50%FI, respectively in density of 90,000 plant ha(-1). Therefore, the transplanting method due to alleviating the adverse effects of water stress on yield and physiological response of sugar beet along with plant density of 90,000 plant ha(-1) under moderate deficit irrigation (75%FI) can be suggested as an efficient field management in sugar beet cultivation.