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Journal of Production Agriculture Abstract - Research

Potential of ‘Savanna’ Stylo as a Stockpiled Forage for the Subtropical USA

 

This article in JPA

  1. Vol. 6 No. 4, p. 553-556
     
    Received: Sept 10, 1992
    Published: April 19, 2013


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doi:10.2134/jpa1993.0553
  1. M. J. Williams**,
  2. C. G. Chambliss and
  3. J. B. Brolmann
  1. U SDA-ARS, Subtrop. Agric. Res. Stn., Brooksville, FL 34605
    D ep. of Agronomy, Univ. of Florida, Gainesville, FL 32611
    U niv. of Florida Agric. Res. Educ. Center, Ft. Pierce, FL 34954

Abstract

Most tropical grasses are nutritionally inadequate during the fall to support weight gains in replacement heifers. The objective of this study was to determine how the newly developed, perennial tropical legume, ‘Savanna’ stylo [Stylosanthes guianensis (Aubl.) Sw.] PI 562697, when grown as an annual, would compare with the true annuals, alyceclover [Alysicarpus vaginalis (L.) DC] and hairy indigo (Indigofera hirsuta L.), as a stockpiled forage for the fall. Savanna, common alyceclover, and ‘Flamingo’ hairy indigo were planted in a replicated field trial in June 1989 and 1990. Growth rate (lb/sq yd/d), dry matter (DM) yield, crude protein (CP), and in vitro organic matter digestibility (IVOMD) were determined for each legume in August, September, October, and November of each year. At the August harvest in both years, DM yield of Savanna (≤ 1 ton/acre) was lower (P < 0.05) than the annual legumes, but by October or November of both years, DM yield of Savanna (2–3 tons/acre) was equal to or better than (P < 0.05) the annual legumes. Early season (planting to August) growth rate of Savanna (0.0045 lb/sq yd/d) was one-third to one-half that of alyceclover (0.0125 lb/sq yd/d) or hairy indigo (0.0093 lb/sq yd/d). Growth rate of Savanna was equal to or better than the annual legumes at all subsequent harvest dates, particularly when they started to flower (September for alyceclover and October for hairy indigo). At all harvest dates in both years, CP (10–17.1%) and IVOMD (68.9–51.5%) of Savanna was equal to or better than (P < 0.05) either annual legume. Our results suggest that Savanna stylo could be useful for replacement heifer development programs when grown as an annual for fall-stockpiled management systems.

Research Question

Despite numerous studies showing the economic advantages of calving replacement heifers at 2 yr of age, beef cattle producers in those areas of the USA where tropical grasses make up the primary forage base are the least likely group to use this management option. In part, this is because most tropical grasses do not have the nutritional quality (crude protein and digestibility) during the fall (September–November) to support weight gains in replacement heifers until winter-annual grazing is available. In preliminary legume evaluations, the newly developed, perennial tropical legume ‘Savanna’ stylo, when grown as an annual, had a period of vegetative growth that extended into the fall. The objective of this study was to determine how Savanna, when grown as an annual, would compare with the true annuals alyceclover and hairy indigo as a stockpiled forage for use during this fall forage gap.

Literature Summary

Developed as a perennial forage for south Florida, Savanna stylo failed to perennate or even reliably set seed in a preliminary, tropical legume evaluation in central Florida. In that trial though, it was noted that even during the establishment year Savanna grew well and appeared to remain vegetative longer into the fall than most other commonly used, tropical legumes, particularly annual species. Little was known about forage yield and quality of Savanna during the fall, and how this compared with other commonly available annual tropical legumes managed for fall feed reverses.

Study Description

Our study (Table 1) was conducted in central Florida at the USDA-ARS, Subtropical Agricultural Research Station (28 °37′ N, 82 °28′ W) on a Candler fine sand. Total rainfall during the growing season was similar to the 30-yr average.

Applied Questions

When grown as an annual, how much dry matter (DM) does stockpiled Savanna stylo yield in the fall and how does this compare with the yield of true annuals alyceclover and hairy indigo?

Forage yield of Savanna peaked later in the growing season (June–November) than either alyceclover or hairy indigo (Fig. 1). Alyceclover made 88% and hairy indigo 63% of their respective total growth before September, compared with 24% for Savanna. As a consequence, both annuals had more DM yield in August than Savanna, but at all subsequent harvests, DM yield of Savanna was equal or superior to that of either annual species. This was due to a combination of continued vegetative growth of Savanna in September, October, and November, and photoperiod mediated flowering and senescence of the annual species during this same period. Dry matter of Savanna continued to increase until frost or the onset of flowering in November.

Fig. 1
Fig. 1

Dry matter yield of June-planted ‘Savanna’ stylo, common alyceclover, and ‘Flamingo’ hairy indigo harvested at four dates in the fall (2-yr average).

 

What is the forage quality of stockpiled Savanna stylo during the fall and how does it copmare with alyceclover and hairy indigo?

Whole plant in vitro organic matter digestibility of Savanna stylo ranged from 68.9% in August to 51.5% in November (2-yr average). Digestibility of Savanna was equal to alyceclover and hairy indigo in August and September, but higher than both annual species by almost 20 percentage units in November. Crude protein content of Savanna for the 2 yr ranged between 17.1% in August of 1990 to a low of 10% in November 1989. As with digestibility, crude protein of Savanna was equivalent to the annual legumes in August and September, but was higher, often by 2 to 3 percentage units, than both annual legumes in October and November of each year.

Recommendations

This study suggests that Savanna stylo could be useful for replacement heifer development programs when grown as an annual for fall stockpiled management systems. In the range observed, whole-plant forage quality of Savanna stylo should provide between 0.5 and 1.0 lb/d gain in replacement heifers. Better heifer gains might be achieved if a first-last grazing system with heifers and dry cows were used. Fall-stockpiled Savanna should be managed so that the standing forage is consumed before frost, because, as with other tropical forages, palatability and forage quality decline rapidly after frost.


View Full Table | Close Full ViewTable 1

Planting date, seeding rate, and harvest date of ‘Savanna’ stylo, common alyceclover, and ‘Flamingo’ hairy indigo in 1989 and 1990.

 
Planting date Harvest date


1989 1990 Legume† Seeding rate 1989 1990
lb/acre
26 June 15 June Savanna 10 24 Aug. 28 Aug.
Alyceclover 20 20 Sep. 20 Sep.
Hairy indigo 20 25 Oct. 25 Oct.
21 Nov. 21 Nov.
All seed inocluated with alyceclover inoculant.

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Copyright © 1993. Copyright © 1993 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, 5585 Guilford Rd., Madison, WI 53711 USA