Strategies for Increasing Rhizoma Peanut Contribution to Productivity and Ecosystem Services of Low-Input Pasture Systems

Strategies for Increasing Rhizoma Peanut Contribution to Productivity and Ecosystem Services of Low-Input Pasture Systems

Summary

A series of experiments was established to develop technologies for incorporating rhizoma peanut (RP) into low-input pasture systems in the SE USA. A two-year establishment study illustrated that Florigraze RP has the greatest potential for incorporation into strip-planted bahiagrass systems. Grazing of RP strips reduced the establishment rate compared to haying after two years of management. Evaluation of the grazing tolerance of newly released RP genotypes was initiated in 2012 and will be continued in 2013 to quantify management recommendations. Continuing research will be conducted in 2013 to evaluate the contribution of RP and bermudagrass-based management systems to soil C and N accumulation.

Objectives/Performance Targets

1. To quantify the effects of growth habit of rhizoma peanut (RP) and defoliation management during the establishment year on ground cover and rate of spread of RP cultivars following strip planting into bahiagrass pasture
2. To measure the effect of grazing intensity and frequency on forage accumulation, persistence, and nutritive value of four RP cultivars differing in plant growth habit
3. To quantify the effect on soil organic carbon and nitrogen accumulation of forage systems based on RP or nitrogen-fertilized bermudagrass

Accomplishments/Milestones

In March 2012, the second year of the RP establishment study was planted at the UF Beef Research Unit (Gainesville, FL) to evaluate the impact of perennial peanut growth habit and sward management on rate of establishment and overall establishment success using a strip-planting approach in existing bahiagrass pastures. Total sprout emergence (# sprouts/m2) was recorded until 12 weeks after planting. In June, defoliation management was implemented. Ground cover and frequency of RP occurrence was measured prior to each defoliation event for each entry. Bahiagrass herbage mass was measured throughout the growing season from June to October. Total RP spread was measured at the end of the growing season in October. Year-after-establishment effects were evaluated on the establishment study area previously planted in 2011. Management treatments were imposed on these plots, and ground cover, frequency, and RP spread were quantified at the end of the 2012 season.

The grazing intensity and frequency study was planted in 2010 using four different RP ecotypes and was allowed to establish through the 2010 and 2011 growing season. Defoliation management treatments were imposed on this experiment in June 2012. Treatments included a factorial combination of grazing intensity (50 or 75% canopy removal) and grazing frequency (3- or 6-wk grazing interval). Pre- and postgraze herbage mass was estimated throughout the season using a double-sampling technique as a measure of RP production potential. Ground cover, weed frequency, sward canopy botanical composition, and rhizome mass were estimated at the beginning and end of the grazing season (October 2012) to estimate RP persistence under a range of management strategies. Pregraze canopy light interception and postgraze residual leaf area index were quantified during August and September 2012 to determine the effects of grazing management on sward canopy responses. A second year of this study will be conducted in summer 2013 to determine the effects of grazing management on persistence, production, and nutritive value of various RP genotypes.

In 2011, a soils study was established at the Plant Science Research and Education Unit (Citra, FL) to quantify the effect of forage management systems on soil C and N. Initial soil cores were taken from each plot prior to forage establishment to quantify total C, N, and bulk density in March 2011. In November 2011, plots with winter management treatments were overseeded with Florida 401 rye and allowed to establish until January 2012. Beginning in January, management treatments were imposed and rye was either clipped or grazed monthly until March 2012. Grazed and hayed plots were sampled monthly for herbage mass and nutritive value. At the end of the winter growing season in March 2012, plots were sampled for residual herbage mass as an indicator of potential aboveground C and N pools. Beginning in May 2012, management treatments were imposed on RP and bermudagrass plots for the first time. Grazed and hayed plots were sampled monthly for herbage mass and nutritive value. In October 2012, plots were sampled for residual herbage mass and root mass to quantify their potential contribution to soil C and N. Soil samples were collected in October 2012 to quantify potential surface changes in soil organic matter (OM) after one year of management (winter 2011 and summer 2012). Soil cores were collected in each plot to a 20-cm depth to quantify light and heavy fraction OM associated with short term changes in OM, total C, N, and bulk density. In November 2012, plots were overseeded with rye and the second year of the study began in January 2013 with the initiation of the winter management season.

Impacts and Contributions/Outcomes

Results of the RP establishment study indicate that strip-planting RP in bahiagrass swards may be a viable option for pastures in the SE USA. Although defoliation management effects were not significant in Year 1, the year-after-establishment study illustrated reduced RP cover and spread into bahiagrass for grazed compared to hayed plots, likely due to animal preference for RP when they grazed the planted strip. Florigraze emerged as the genotype with the greatest cover, frequency, and spread across the two-year establishment study. These results will provide needed recommendations to reduce establishment costs of RP, decrease the need for commercial fertilizer, and increase NV of grazed pasture systems.

The first year of the grazing management evaluation of RP genotypes illustrated favorable sward responses for the 6 wk grazing frequency and 50% canopy removal treatments. A second year of this study will be conducted to further quantify potential management recommendations. No studies have evaluated the grazing tolerance of these newly released genotypes; thus, this research is expected to provide RP management recommendations for producers.

Data from the RP experiments at the Beef Research Unit were a key focus of a producer-based Perennial Peanut Field Day in Gainesville, FL in July 2012. Seventy-five attendees viewed the described experiments and complementary experiments that were designed to provide systems recommendations for management of RP in pastures. A post workshop evaluation suggested that 97% of the surveyed population planned to utilize the information presented during the field day.

A second year of the soils study is currently being conducted. This experiment is expected to quantify the potential of forage management systems in Florida to improve soil quality while maintaining pasture productivity. Winter overseeding of RP with rye will provide recommendations on minimally evaluated management options for RP pastures. Increasing soil quality and utilization of these pasture-based systems may lead to economically and environmentally sustainable practices which can be implemented by producers in the region.

Scientific and Extension-Related Presentations (all given by M.K. Mullenix)

Mullenix, M. K., M. Castillo, and L. E. Sollenberger. 2013. Improving warm-season pastures with perennial peanut. Georgia Cattlemen’s Convention. April 4, 2013. Perry, GA.

Mullenix, M. K., L. E. Sollenberger, D. L. Rowland, J. M. B. Vendramini, A. R. Blount, M. L. Silveira, A. Vaccarro. 2013. Sward responses of rhizoma peanut cultivars under a range of grazing management strategies. ASAS Southern Section Meeting, Feb 4, 2013. Orlando, FL.

Mullenix, M. K., L. E. Sollenberger, A. R. Blount, M. Castillo, J. M. B. Vendramini, and M. L. Silveira. 2012. Growth habit of rhizoma peanut cultivars affects establishment and spread when strip-planted in bahiagrass sods. ASA-CSSA-SSSA Annual Meeting. Oct 20-24, 2012. Cincinnati, OH.

Mullenix, M. K. 2012. Growth habit of perennial peanut affects spread into bahiagrass sod. 12th Annual Perennial Peanut Producer’s Association Field Day. Gainesville, FL.

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