Evaluating the Tolerance of Young Hybrid Poplar Trees to Recycled Waters High in Salinity and Boron

Abstract

The successful adoption of water recycling strategies in many arid regions will require crops able to tolerate poor-quality waters. We evaluated different clones for salt and boron (B) tolerance within each of seven genetically distinct genomic groups (e.g., deltoides, deltoides × nigra, trichocarpa × deltoides, trichocarpa × deltoides × maximowizcii, trichocarpa × deltoides × nigra, trichocarpa × nigra, trichocarpa × maximowizcii). During each evaluation period, different clones within each of the groups were irrigated with high sodium chloride (NaCl) salinity (i.e., 10–30 dS m⁻¹) and B (i.e., 10 mg L⁻¹) water up to a maximum of 150 days, for a 4-year testing period under micro-field plot conditions. Excessive accumulation (up to 6%) of chloride (Cl) likely caused toxicity symptoms (necrosis of the leaves) observed in the less tolerant clones, while leaf B concentrations rarely exceeded 300 mg kg⁻¹ DM in any clone. Increased soil salinity likely hindered the uptake of B by the clones. Our results show that a wide range of selected Populus clones, of parentage trichocarpa × nigra, followed by deltoides × nigra show potential salt and B tolerance as young trees to recycled waters high in salinity and B.

KEY WORDS:

• poplar trees
• recycled water
• salinity
• boron

ACKNOWLEDGMENTS

The authors extend their gratitude to John Diener of Red Rock Ranch. We would like to dedicate this manuscript to Dr. Jon Johnson who passed away after an extended illness.

Notes

^†Treated for 32 days.

^‡A total of 6,750 mL of good quality water was used for growing control clones (K°), while a total of 1,200 mL of 10 dS m⁻¹, 900 mL of 20 dS m⁻¹ and 2,100 mL of 10 mg B L⁻¹ was applied for growing salt/B treated clones; a total amount of 8.8 g of salt (5 g of Cl) and 21 mg of B was applied.

^§Performance ratings defined in Materials and Methods.

^†Treated for 148 days.

^‡A total of 26,250 mL of good quality water was used for growing control clones (K°), while 2,250 mL 10 dS m⁻¹, 8,750 mL of 20 dS m⁻¹, 1,800 mL of 30 dS m⁻¹, and 12,800 mL of 10 mg B L ⁻¹ water was applied for growing salt/B treated clones; a total amount of 161 g of salt (92 g of Cl) and 120 mg of B was applied.

^§Performance ratings defined in Materials and Methods.

^¶Tested for the second time.

^†Treated for 75 days.

^‡A total of 18,000 mL of good quality water was used for growing control clones (K°), while 12,400 mL of 10 dS m⁻¹ 900 mL of 20 dS m⁻¹, and 13,300 mL of 10 mg B L⁻¹ water was applied for growing salt/B treated clones; a total amount of 91 g of salt (48 g of Cl) and 133 mg of B was applied.

^§Performance ratings described in Materials and Methods.

^†Treated for 132 days.

^‡A total of 26,200 mL of good quality water was used for growing control clones (K°), while 4,500 mL of 10 dS m⁻¹, 6,800 mL of 20 dS m⁻¹, 5,400 mL of 30 dS m⁻¹, and 16,700 mL of 10 mg B L⁻¹ water was applied for growing salt/B treated clones; a total amount of 220 g of salt (126 g of Cl) and 167 mg B was applied.

^§Performance ratings defined in Materials and Methods.

^¶Tested for the second time.

^#Tested for the third time.

^†Treated for 122 days.

^‡A total of 45,700 mL of good quality water was used from growing control clones (K°), while 8,800 mL of good quality water, 6,800 mL of 10 dS m⁻¹, 13,800 mL of 20 dS m⁻¹, and 20,600 mL of 10 B L⁻¹ water was applied for growing salt/B treated clones; a total amount of 220 g of salt (123 g of Cl) and 206 mg B was applied.

^§Performance ratings defined in Materials and Methods.

^¶Tested for the second time.

^#Tested for the third time.

^†Saline solution composition of water used for irrigation of poplar clones throughout the individual evaluation studies.

^†Precipitation that occurred during respective growing seasons.

^‡Maximum (Max) and minimum (Min) air temperatures that occurred during respective growing seasons.

^†Treatments S/B (salinity and B) and K° (control) are described in Tables 2–5 footnotes and in Materials and Methods.

^‡Soil samples were collected at preplant from ‘control’ soil before placing tree seedlings into pots; mean ECe values were 0.8 (0.1) dS m⁻¹ and B values were 0.1(0.02) mg L⁻¹.

^§Values represent the means from six replications with the standard deviation in parenthesis.