Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/2/2011
Publication Date: 11/1/2011
Citation: Rouquette, Jr, F.M., Anderson, W.F., Harris-Shultz, K.R., Smith, G.R. 2011. Stand maintenance and genetic diversity of bermudagrass pastures under different stocking intensities during a 38 year period. Crop Science. 51:2886-2894. Interpretive Summary: A long-term (38-year) cattle stocking management study was performed with bermudagrass [Cynodon dactylon (L) Pers] pastures consisting of ‘Coastal’ and common bermudagrass. On average, Coastal pastures were stocked with about 2.5, 4.5, and 7.5 cow-calf pair per hectare and common pastures were stocked at 2.0, 3.5, and 5 pair per hectare. From 1985 to 2005, these pastures were supplemented with either nitrogen fertilizer and overseeded with annual ryegrass (Lolium multiflorum Lam) or no nitrogen and only overseeded with clover (Trifolium sp). The persistence of both Coastal and common bermudagrass was negatively affected by increased stocking rates and with no nitrogen fertilizer. Bahiagrass (Paspalum notatum Flugge) and common bermudagrass types were the primary invasive plants within the higher stocked pastures. Whole plants of visibly different bermudagrass clones within each of the pastures were collected via whole plant-root cores and sent to USDA/ARS Tifton, GA. Growth traits were measured in a greenhouse. Each of the 125 cloned plants was fingerprinted using amplified fragment length polymorphism (AFLP) molecular genetic technology. Results indicated four distinct groups for Coastal and five groups for common plants along with intermittent, non-related clones. Phenotypes based on plant height, leaf length, leaf width, and leaf coarseness as well as plant inflorescence (heading amount, raceme number, and raceme length) also helped to differentiate between common and Coastal types. Bermudagrass pastures were most sustainable when stocked at moderate to low intensities and when receiving nitrogen fertilization.
Technical Abstract: Stocking management strategies can affect production and persistence of bermudagrass [Cynodon dactylon (L) Pers] (BG) pastures. ‘Coastal’ (COS) and common (COM) bermudagrass (BG) pastures were stocked at different controlled intensities (STK) during a 38-yr period which was initiated in 1969. On average, COS pastures stocking rates were about 2.5, 4.5, and 7.5 cow-calf pair ha-1 (700 kg/pair) and COM pastures were stocked at 2.0, 3.5, and 5 pair ha-1. From 1985 to 2005, fertility regimens of N + annual ryegrass (Lolium multiflorum Lam) (RYG) vs no N + clover (Trifolium sp) (CLV) were superimposed on each BG x STK pasture. Percent stand of both COS and COM BG was negatively affected by STK and no N fertilizer. Bahiagrass (Paspalum notatum Flugge) was the primary non-BG invasive species on non-N pastures. Invasive BG ecotypes (ECOT) were more abundant at 73 to 86% of stand on high STK of COS and CLV or RYG, respectively. On COM pastures, invasive ECOT were present at about 25% and 40%, respectively on CLV and RYG, but was not affected by STK. During October 2005, when visual phenotypic differences were evident, whole plant-root cores which exhibited ECOT were collected from pastures and transferred to USDA/ARS Tifton, GA. Growth traits were measured in a greenhouse. Each of the 125 ECOT plants were fingerprinted using AFLP markers, analyzed via coefficient of genetic similarity matrix, and clustered in genetically related groups. There were four distinct similarity groups for COS and five for COM with intermittent, non-related ECOT. The COS and COS-similar ECOT were different from COM and COM-similar ECOT in plant height, leaf length, leaf width, and leaf coarseness. Characteristics of plant inflorescence (heading amount, raceme number, and raceme length) ranked similarly to those of other plant characteristics. Bermudagrass pastures were most sustainable when stocked at moderate to low intensities and when receiving N fertilization.