Creeping Bentgrass Putting Green Cultivation Recovery and Pre-Stress Conditioning with Liquid Fertilizer and Biostimulant Programs

Creeping Bentgrass Putting Green Cultivation Recovery as Affected by Pre-Stress Conditioning with Liquid Fertilizer and Biostimulant Programs in the Cool-Humid Region

Cale Bigelow, Department of Agronomy, Purdue University, West Lafayette, IN 47907; Erik Ervin, Xunzhong Zhang, and Adam Nichols, Crop and Soil Environmental Sciences, Virginia Tech, Blacksburg, VA 24061

Corresponding author: Cale Bigelow. cbigelow@purdue.edu

Creeping bentgrass (Agrostis stolonifera L.) putting greens are core cultivated multiple times annually to minimize excess organic matter and maintain surface firmness (1). This abrasive process induces turf stress and is traditionally conducted during periods of active growth to ensure rapid recovery and minimize surface disruptions. Although turf managers routinely apply fertilizer before and/or after coring to promote healing, research-based recommendations for nutrient applications are lacking. Besides nutrients like nitrogen, phosphorus, or potassium, many managers routinely incorporate plant hormone supplements from seaweed extract or humic acid into their programs. These supplements, or biostimulants, are added because they have been demonstrated to improve bentgrass stress tolerance (3). Information directly comparing traditional fertilizers and the potential benefit of biostimulants for alleviating stress and enhancing recovery after coring would prove useful to turf managers.

The objective of this study was to evaluate the effectiveness of a commercially available plant nutrient and biostimulant program when compared to generic nutrient and biostimulant ingredients applied alone or in combination with complete nutrient solutions for their ability to enhance creeping bentgrass recovery from spring cultivation. Field studies were conducted in 2009 on sand-based rootzones at Purdue University in West Lafayette, IN, and Virginia Tech in Blacksburg, VA. Treatments were:

(i) an unfertilized control;

(ii) a commercial liquid program (Floratine Inc., Collierville, TN) consisting of Per-4-Max at 3 oz/1000 ft² + Power at 6 oz/1000 ft² + Knife Plus at 3 oz/1000 ft² + Protesyn at 6 oz/1000 ft² supplying 0.18 lb N, 0.01 lb P₂O₅, and 0.11 lb K₂O per 1000 ft², along with various micronutrients and unspecified biostimulants;

(iii) a generic nutrient control designed to match the nutrients contained in the commercial program (Modified 1/10th-strength Hoagland’s nutrient solution + additional mineral N, P, K);

(iv) the nutrient control + generic biostimulants (seaweed extract, 3.3 oz/1000 ft² + leonardite humic acid, 15 g/1000 ft², + tryptophan, 1 g/1000 ft², + sucrose, 30 g/1000 ft²); and

(v) the generic biostimulants alone (Purdue site only).

All treatments were liquid applied to the foliage with a CO₂-pressurized sprayer delivering 2.0 gal/M spray carrier volume at 10 and 1 days prior to cultivation which corresponded to 24 April and 3 May and 1 and 10 May for the Virginia Tech and Purdue sites, respectively. Hollow tine core cultivation using 1/2-inch or 5/8-inch diameter tines and affecting approximately 6.5% of surface area, occurred on 4 or 11 May to mature stands of ‘Penn A-4’ or ‘Pennlinks’ creeping bentgrass at the Virginia Tech and Purdue sites, respectively. Each site had received minimal spring-applied N, ≤ 0.5 lb/1000 ft², and was immediately topdressed with a medium-coarse sand and brushed to completely back-fill the holes. Recovery was measured using digital image analysis using a uniformly illuminated photo-light box (2). Treatments were arranged in a randomized complete block design with four replications. All data were subjected to analysis of variance and significant treatment means separated at P = 0.05. Sites were mowed 6 times per week at 0.140 inches and irrigated to promote growth and recovery.

Significant treatment differences at Purdue were measured 3 days after coring (DAC), while differences at Virginia Tech were not evident until 12 DAC (Table 1). Recovery 11 to 14 DAC at both sites was similar with the fastest recovery associated with treatments ii, iii, and iv − which were the liquid commercial program − the generic nutrient control (Purdue site only), and the nutrient control + biostimulants (Fig. 1). In addition to faster healing, these treatments were darker green and more visually appealing (data not shown). The generic biostimulant ingredients alone, treatment v, did not enhance recovery or appearance.

Table 1. Percentage green bentgrass turf following hollow tine coring as affected by various pre-stress liquid applied plant nutrient and biostimulant supplement programs at Purdue University (PU) and Virginia Tech (VT).

Site	Trt	Description	Measurement date
			14 May	16 May	18 May	22 May	25 May
			Percentage green turf (0-100%)
PU	1	Untreated	95.7 b*	97.6 b	95.7 c	92.4 b	96.6 b
	2	Commercial liquid program	98.3 a	99.3 a	99.5 a	98.8 a	99.6 a
	3	Nutrient control	98.3 a	99.4 a	99.2 ab	99.1 a	99.7 a
	4	Nutrient control + generic biostimulants	98.4 a	99.5 a	99.5 a	99.1 a	99.7 a
	5	Generic biostimulants	95.8 b	97.7 b	97.1 bc	94.4 b	97.4 b
Site	Trt	Description	4 May	12 May	14 May	16 May	19 May
VT	1	Untreated	98.8 a	93.1 a	93.4 a	93.6 b	95.6 b
	2	Commercial liquid program	98.3 a	94.3 a	95.5 a	97.7 a	98.3 ab
	3	Nutrient control	97.5 a	93.8 a	95.6 a	97.7 a	98.6 a
	4	Nutrient control + generic biostimulants	97.5 a	94.0 a	94.4 a	96.7 ab	97.5 ab

* Means in the same column followed by the same letter are not significantly different according to Fisher’s protected LSD t-test (P = 0.05).

	A
	B
	C
	D
	E
		Fig. 1. Example of treatment difference on recovery from coring at five days after coring (left column) and fourteen days after core cultivation: (A) commercial biostimulant program; (B) generic complete nutrient control; (C) nutrient control + generic bio-stimulants; (D) generic biostimulants only; (E) untreated control.

In summary, these results emphasize the importance of turf nutritional status and supplemental fertilization, primarily from inorganic nutrients, during healing, and raise several future research questions regarding the influence of various nutrient sources, application rates, and timing. Future investigations should evaluate the effect of other biostimulants packages versus supplemental N alone when applied during summer heat stress possibly with plant growth regulators.

Literature Cited

1. McCarty, L. B. 2005. Best Golf Course Management Practices, 2nd Edn. Pearson/Prentice Hall, Upper Saddle River, NJ.

2. Richardson, M. D., Karcher, D. E., and Purcell, L. C. 2001. Quantifying turfgrass cover using digital image analysis. Crop Sci. 41:1884-1888.

3. Zhang, X., and Ervin, E. H. 2004. Cytokinin-containing seaweed and humic acid extracts associated with creeping bentgrass leaf cytokinins and drought resistance. Crop Sci. 44:1737-1745.