© 2002 Plant Management Network. 
Accepted for publication 19 April 2002. Published 29 April 2002.

Effects of Foliar Fertilizers and Growth Regulators on Alfalfa Yield and Quality

Marvin H. Hall, Robert C. Stout, and W. Scott Smiles, Department of Crop and Soil Sciences, Pennsylvania State University, University Park, PA 16802

Corresponding author: Marvin H. Hall. mhh2@psu.edu

Hall, M. H., Stout, R. C., and Smiles, W. S. 2002. Effects of foliar fertilizers and growth regulators on alfalfa yield and quality. Online. Crop Management doi:10.1094/CM-2002-0429-01-RS.

Abstract

Alfalfa (Medicago sativa L.) requires relatively high quantities of nutrients to achieve optimum yields. Commercially available foliar applied fertilizers and growth regulators reportedly provide adequate nutrient levels and increase alfalfa stem number, yield, and quality. The objective of this research was to determine the effectiveness and profitability of several commercially available foliar fertilizers and growth regulators to stimulate shoot development and increase forage yield and quality on high fertility soils in Pennsylvania. Eight treatments including controls of no soil additives and lime were compared to foliar applied treatments including water, liquid fertilizer, and four commercial products at four location-year environments. None of the foliar applied products increased stem density, yield, or quality of alfalfa in environments where initial or adjusted soil pH 6.5. Consequently the additional cost of foliar applied products was not recovered in yield or quality increases of alfalfa compared to maintaining adequate soil pH and fertility through traditional lime and fertilizer amendments.

Introduction

Fig. 1. Alfalfa field (click image for larger view).

High-yielding alfalfa (Fig. 1) is a high consumer of plant nutrients in that each ton removes approximately 60 and 20 lb per acre of K₂O and P₂O₅, respectively (1). Traditionally, these nutrients have been provided to the plants through applications of manure or dry fertilizer to the soil. Recently however, companies have been marketing liquid fertilizers and growth regulators that are foliar applied to alfalfa. These foliar applied fertilizers augment or replace traditional fertilizer applications.

Application of the plant growth regulator cytokinin can stimulate plant growth (2,6,10,12,14). Tompkins and Hall (12) reported that cytokinin application to alfalfa stubble increased the number of shoots and DM yield per plant in both greenhouse and field studies. In low density alfalfa stands, commercial use of this growth regulator may stimulate shoot development and temporarily maintain herbage yields. However, commercial use of cytokinins to enhance crop yields has been limited. Kinetin, a form of cytokinin, is labeled by the U.S. Environmental Protection Agency for use on small grains, vegetables, and oil seed crops (9). Commercial cytokinin application to alfalfa plants has not been reported; however, application to another legume, pea (Pisum sativum L.), caused dormant lateral buds to rapidly elongate into fully developed shoots (8).

Foliar application of macro- and micronutrients to alfalfa, either alone or in combination with a plant growth regulator, is currently available to farmers as a method for improving yield and forage quality. However, there is limited unbiased information available regarding the effectiveness or profitability of these products. Consequently, this research was undertaken to determine the efficacy and profitability of commercially available foliar fertilizers and growth regulator products on alfalfa.

Experiments and Results

In October of 1999, uniform stands of established alfalfa at two locations (Farm 1 and Farm 2) were divided into four replicates of eight 6-x-15-ft plots in a randomized complete block design. Similar plots were designated at another location (Farm 3) in October of 2000. The three locations were within 3 miles of each other near Rock Springs, PA (40°48’N, 77°52’W, elevation 1220 ft) and were on a Hagerstown silt loam (fine-loamy, mixed, mesic Typic Hapludalfs) soil. Soil pH and fertility at Farm 2 and 3 were in the “optimum” to “high” range according to soil tests (Table 1). Soil pH was low at Farm 1 so lime was added to bring pH up to 6.5 in seven of the eight plots. The alfalfa stand was older at Farm 1 and had only about 30% plant density relative to the other sites (Table 1).

Table 1. Alfalfa stand age, plant density, and soil nutrient levels prior to initiation of the studies at three locations in Pennsylvania.

* Determined using the Mehlich 3 method (13).

In 2000, foliar treatments were applied in accordance with company recommendations to the plots at Farm 1 and 2 (Table 2). In 2001, thin stands at Farm 1 resulted in the alfalfa field being rotated to corn; however, the treatments were applied at Farm 2 again and also at Farm 3. Precipitation and average daily temperatures during the 2000 and 2001 growing seasons were within 4.5 inches and 0.5°F, respectively, of the previous 20-year average. Dimethoate insecticide (0,0-dimethyl S-[N-(methylcarbamoyl)methyl] phosphorodithioate) was applied as needed to control potato leafhopper (Empoasca fabae Harris) throughout the studies. Alfalfa was harvested four times each year at a 3-inch stubble height from all treatments when the average maturity was late vegetative to first flower based on the mean stage count method described by Kalu and Fick (5). At harvest, a 3-x-15-ft strip was removed from the center of each plot with a flail-type mower. Approximately 2 lb of the harvested material was dried in a forced air oven for dry matter determination.

Table 2. Lime and foliar treatments applied to alfalfa at three locations over a 2-year period.

* Lime was applied only at Farm 1 in the fall prior to initiating the foliar treatments to raise pH up to 6.5. Consequently, this treatment was not tested at the other locations.

† Foliar treatments were applied in a water solution at 20 gal per acre except for Conklin Company’s product which was applied in a water solution at 5 gal per acre in compliance with product application instructions.

‡ Includes cost for foliar applied material and a charge of $5 per acre per application but does not include cost for lime.

Before the third harvest each year, two randomly-selected 1-x-1-ft areas within each plot were hand-harvested three inches above the soil surface. Alfalfa herbage from the two areas within a plot was combined. Leaves and stems were separated and stem number determined. Leaves and stems were dried in a forced-air oven at 140°F for 48 h, weighed and then combined before being ground to pass a 0.04 inch screen prior to analysis. Only the third harvest each year was hand-sampled for morphological and quality determinations because previous studies had shown that differences in these parameters were greatest in summer growth (4).

Forage quality was predicted using near-infrared reflectance spectroscopy (NIRS). In 2000, 42 samples were selected from the complete set of 64 samples using the SELECT computer program described by Shenk and Westerhaus (11) and analyzed for crude protein (CP), acid detergent fiber (ADF), and neutral detergent fiber (NDF). Crude protein was determined as Kjeldahl N x 6.25, and ADF and NDF concentrations were measured using the procedures of Goering and Van Soest (3). These 42 samples were used to create a calibration equation to predict constituents of all samples collected in 2000. The coefficients of determination (r²) exceeded 0.968 for all NIRS prediction equations. In 2001, quality constituents were predicted using the equation developed in 2000.

Data were subjected to exploratory analysis to determine if the assumptions of analysis of variance held. Homogeneity of variance was tested using Hartley’s F-max test (7). As a result of this test, data from each location-year environment were analyzed separately. All statistical analyses used SAS Institute (SAS Inst., Cary, NC) software. Tukey’s multiple comparison procedure was used for mean separations. Differences reported in this paper are all at the P £ 0.05 level of significance.

Differences in yield between treatments occurred in only one of the four location-year environments. At Farm 1, the no-lime treatment yielded less than all the other treatments (Table 3). When lime was added, yields were not different regardless of foliar fertilizer or growth regulator treatments. This difference in yield at only one location-year environment can be attributed to the low pH at that location. When pH was at acceptable levels (Farm 2 and 3) or adjusted to an acceptable level (Farm 1), other treatments had no effect on yield. Yields at Farm 2 and 3 averaged 6.4 and 8.3 tons per acre, respectively.

Table 3. Season-total dry matter yield and third-harvest plant morphology at Farm 1 in 2000.

Number of stems per unit area and leaf:stem ratio were not affected by treatment at any location-year environment. The average number of stems per unit area at Farm 1 was 42 stems per ft² and the other locations averaged of 68 stems per ft². These differences can be attributed to fewer plants per ft² at Farm 1. It was assumed that the greatest impact of foliar applied products would be the increase in stem numbers in thin alfalfa stands like that at Farm 1, but in fact none of the products had any effect on stem numbers.

There were no treatment differences at any location-year environment for the forage quality parameters measured. Crude protein, ADF and NDF were 22.2, 32.6 and 42.9% of dry matter, respectively, when averaged across all treatments, locations, and years.

The foliar-applied products used in this research did not increase alfalfa yield or quality, or alter plant morphology when soil pH and fertility were at recommended levels. Consequently, the additional cost of these products ($60 to $234 per acre per year) cannot be justified over maintaining adequate soil pH and fertility through traditional liming and fertilization practices.

References Cited

1. Beegle, D. B. 1995. Soil fertility management for forage crops: Maintenance. Agron. Facts 31-C, Penn State University, University Park, PA 16802.

2. Davies, F. T. Jr., and Moser, B. C. 1980. Stimulation of bud and shoot development of rieger begonia leaf cuttings with cytokinins. J. Amer. Soc. Hort. Sci. 105:27-30.

3. Goering, H. K., and Van Soest, P. J. 1970. Forage fiber analysis: apparatus, reagents, procedures, and some applications. USDA-ARS Agric. Handb. 379. U.S. Gov. Print. Office, Washington, DC.

4. Hall, M. H., Smiles, W. S., and Dickerson, R. A. 2000. Morphological development of alfalfa cultivars selected for higher quality. Agron. J. 92:1088-1080.

5. Kalu, B. A., and Fick, G. W. 1981. Quantifying morphological development of alfalfa for studies of herbage quality. Crop Sci. 21:267-271.

6. Massengale, M. A., and Meddler, J. T. 1958. Some responses of alfalfa to different lengths of day and growth regulators in the greenhouse. Agron. J. 50:377-380.

7. Milliken, G. A., and Johnson, D. E. 1984. Analysis of messy data, Vol. 1: Designed experiments. Lifetime Learning Publ., Belmont, CA.

8. Pillay, I., and Railton, I. D. 1983. Complete release of axillary buds from apical dominance in intact, light-grown seedlings of Pisum sativum L. following a single application of cytokinin. Plant Physiol. 71:972-974.

9. Saulk, P. L., and Parker, L. W. 1987. Soil `Triggrr' and foliar `Triggrr': plant growth regulators containing cytokinin. Proc. Plant Growth Regulator Soc. Amer. 14:369-376.

10. Sharif, R., and Dale, J. E. 1980. Growth regulating substances and the growth of tiller buds in barley: Effects of cytokinins. J. Exp. Bot. 31:921-930.

11. Shenk, J. S., and Westerhaus, M. O. 1994. The application of near infrared reflectance spectroscopy (NIRS) to forage analysis. Pages 406-409 in: Forage Quality Evaluation and Utilization. G. C. Fahey, et al., eds. ASA, CSSA, and SSSA, Madison, WI.

12. Tompkins, J. P., and Hall, M. H. 1991. Stimulation of alfalfa bud and shoot development with cytokinins. Agron. J. 83:577-581.

13. Wolf, A. M., and Beegle, D. B. 1995. Recommended soil tests for macronutrients: phosphorus, potassium, calcium, and magnesium. Pages 25-34: Recommended Soil Testing Procedures for the Northeastern United States. J. Thomas Sims and A. Wolf, eds. Northeast Regional Bulletin #493. Agricultural Experiment Station, University of Delaware, Newark, DE.

14. Yeh, K. J., and Bingham, E. T. 1969. Vegetative and floral response of three alfalfa genetic stocks to growth regulators. Crop Sci. 9:835-837.