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Welcome to The Turf Zone podcast. This episode is investigating effects of Antisalt and CalPlus on creeping bentgrass quality and physiological fitness under salt stress. Written by Xunzhong Zhang, Mike Goatley, Maude Focke, Taylor Motsinger, Berit Smith, and Graham Sherman.

Introduction and Objective

Salt stress is one of the major limiting factors in turfgrass management in many areas. Various agronomic and chemical approaches have been used to alleviate salt-induced injury to turfgrass. Antisalt and CalPlus are two products which have been documented to improve plant tolerance to salt stress. The objective of this study was to investigate if foliar application of Antisalt and CalPlus at two different rates affects physiological fitness and quality of creeping bentgrass under salt stress conditions.

Research Procedure

Mature ‘A4’ creeping bentgrass plugs (4-inch diameter) were collected from field plots and transplanted into 6-inch pots filled with fine sand with 10% calcined clay in mid-September 2024. The bentgrass was maintained at 0.6 inch and fertilized biweekly. After about four weeks of non-stressed growth under optimum temperature, water, fertilizer, and light conditions, the grass was treated with the two products at two rates of the products each on October 8, 2024. There were 6 treatments with 4 replications. The product solution (rates listed below) was applied to the canopy, and the same amount of water was applied to the controls (treatments #1 and 6). The treated grass was grown in a controlled environment growth chamber at 71.6 ºF day (12 h)/64.4 ºF night, light intensity at 400 µmol m-2 s-1, 12 h photoperiod, and 65% relative humidity. After 12 h of the initial treatment, we initiated salt stress treatment. Sodium chloride (NaCl) solution at 2 ds/m concentration was added first, and then 4 ds/m concentration, and 6 ds/m concentration, and finally 8 ds/m concentration at 48 h after initiation of salt stress treatment. The salt concentration in the growth media was maintained at about 8 ds/m level during the trial by monitoring the salt concentration with a portable TDR-300 meter. The grass was irrigated with salt water and fresh water alternatively in order to maintain water content near field capacity and EC level at about 8 ds/m during the trial.

The treatments include

1. Fertilized control (0.15 lb N/1000 ft² biweekly) + salt stress;
2. Antisalt at 3 fl oz/1000 ft² biweekly + salt stress;
3. Antisalt at 9 fl oz/1000 ft² biweekly + salt stress;
4. CalPlus at 3 oz/1000 ft² biweekly + salt stress;
5. CalPlus at 9 oz/1000 ft² biweekly + salt stress; and
6. Fertilized control, non-salt stress. Flobond LX50 Antisalt was provided by SNF Inc. (Riceboro, GA) and CalPlus was from Harrell’s (Lakeland, FL).

The rate of N fertilization (from 28-8-18) for treatments #2, 3, 4, and 5 was the same as control treatments #1 and 6.

Measurements

The stress period of the trial lasted for 8 weeks with a total of 4 treatment applications. Bentgrass growth and physiological responses were measured biweekly. Root growth characteristics and viability were measured at the end of the trial. In addition, leaf tissue nutrient levels (N, P, K, Na, Ca, S, Mg) were determined with the ICP method. The data were subjected to an analysis of variance and where appropriate, mean separations were performed with a protected Fisher’s least significance difference test at a 5% probability level.

Results and Discussion

Leaf color and green leaf percentage (GL)

Salt stress reduced leaf color ratings. CalPlus application at the two rates improved leaf color ratings relative to the control as measured from day 14 through day 56. Application of Antisalt also improved leaf color rating at 3 fl oz/1000 ft² at day 14, 28, and 56 when compared to the control.

The GL declined in response to salt stress. CalPlus application at the two rates improved GL as measured at day 28, day 42, and day 56. Antisalt at 3 fl oz/1000 ft² also improved GL when compared to the control as measured at day 42 and 56.

Clipping production and relative clipping weight

Salt stress reduced plant growth and clipping production. Application of Antisalt and CalPlus at the two rates alleviated clipping reduction as measured at day 56.

Salt stress reduced relative clipping weight, and Antisalt and CalPlus treatments has greater relative clipping weight than the salt control as measured at day 56.

Leaf chlorophyll and carotenoids

Salt stress reduced chlorophyll and carotenoids content. Application of CalPlus at the two rates increased chlorophyll content relative to the salt control at day 42 and 56. Antisalt treatment at the two rates also increased chlorophyll content relative to the salt control at day 42.

Similarly, application of CalPlus at the two rates increased carotenoids content relative to the salt control at day 42 and 56. Antisalt treatment at the two rates also increased carotenoids content relative to the salt control at day 42.

Leaf photochemical efficiency (PE) and antioxidant SOD activity

Salt stress reduced PE. CalPlus treatments improved PE relative to salt control as measured from day 14 through day 56. Antisalt treatments also improved PE as measured at day 28, 42, and 56.

Application of Antisalt and CalPlus at the two rates improved antioxidant enzyme SOD activity when compared to the salt control measured at day 42 and 56.

Leaf nutrients (N, P, K, Ca, S, Mg)

Application of Antisalt at 3 fl/1000 ft² and CalPlus at 9 fl oz/1000 ft² improved leaf N and S content relative to the control. Antisalt increased P content and CalPlus at both rates increased leaf Ca, S, and Mg content relative to the control.

Root growth characteristics, relative root weight (RRWT) and viability

Antisalt and CalPlus at 9 fl oz/1000 ft² increased root biomass, length, surface area, volume, viability, and relative root weight when compared to the salt control. Antisalt and Calplus at 3 fl oz/1000 ft² also improved root viability relative to the salt control.

Summary. Applications of CalPlus at 3 and 9 fl oz/1000 ft² and Antisalt at 3 fl oz/1000 ft² improved leaf color, clipping production, photosynthetic pigments, photochemical efficiency, antioxidant SOD activity, and root growth and viability. Antisalt at 9 fl oz/1000 ft² also increased clipping production, photochemical efficiency, leaf chlorophyll, carotenoids, SOD activity, root biomass, and viability relative to the salt control at selected sampling dates. Antisalt at the low rate increased leaf N, P, and S content relative to the control, and CalPlus at both rates increased leaf Ca, S, and Mg content and also leaf N content at the high rate. In general, no consistent differences were observed between the two rates of CalPlus. Antisalt at 3 fl oz/1000 ft² tended to have better effects on leaf color and physiological fitness, and Antisalt at 9 fl zo/1000 ft² tended to have greater effects on root growth. Overall, the results of this study indicated foliar application of Antisalt and CalPlus at the two rates may improve salt stress tolerance by enhancing physiological fitness, leaf color, and root growth in creeping bentgrass.

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