How does plant population density affect the biomass of ravenna grass?

Authors: Springer, Timothy

Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/7/2020
Publication Date: 10/15/2020
Citation: Springer, T.L. 2020. How does plant population density affect the biomass of ravenna grass? Global Change Biology. 13:175-184. https://doi.org/10.1111/gcbb.12767.
DOI: https://doi.org/10.1111/gcbb.12767

Interpretive Summary: Ravenna grass, Tripidium ravennae (L.) H.Scholz, is known to produce an abundance of biomass, but it is unknown how plant population density affects its biomass potential or other plant traits. A scientist at the Southern Plain Range Research Station, Woodward, OK studied the effects of plant population density on biomass yield; plant growth traits; nitrogen removal; and sucrose concentration in leaves and culms. It was found that the biomass yield of Ravenna grass was affected by plant population density in at least four ways. First, biomass yield increased as plant population increased, and the biomass yield reached a maximum of 16.2 megagrams per hectare at a plant population density of 10,640 plants per hectare. Second, plant population density effected the number of reproductive stalks per plant where low plant densities produced a greater number of reproductive stalks per plant. Third, sucrose concentration was affected by plant density, where low plant density produced higher concentrations of sucrose, and where stalks of larger diameters tended to produce higher concentrations of sucrose. And forth, plant density effected the amount of nitrogen removed with biomass. As biomass yield increased with plant density the removal of nitrogen also increased. The data suggest that further research was needed to determine the optimum nutrient requirement for Ravenna grass to sustain high biomass yields at a density of 10,000 plants per hectare.

Technical Abstract: Ravenna grass, Tripidium ravennae (L.) H.Scholz, is known to produce an abundance of biomass, but it is unknown how plant population density affects its biomass potential or other plant traits. The objectives of this research were to determine the effects of plant population density on biomass yield; plant growth traits; biomass'carbon, nitrogen, and ash concentrations; heating value; nitrogen removal; and sucrose concentration in leaves and culms. The treatments consisted of five plant population densities (1,250; 2,500; 5,000; 10,000; and 20,000 plants per hectare) in a randomized complete block design with four blocks. Plots were non'irrigated, unfertilized, and harvested once during the dormant season each year. Data were collected 2015'2019. Dependent variables that varied with plant population density (P < 0.05) were biomass yield, number of reproductive culms per plant, reproductive culm diameter, reproductive culm sucrose concentration, and nitrogen removal with biomass. Biomass yield ranged from 5.6 to 16.3 Mg ha'1 for plant densities of 1,250 to 20,000 plants per hectare, respectively. Combined over years, non-linear regression of the data showed the equation for biomass yield to plateau at 16.2 Mg ha'1 at a plant density of 10,640 plants per hectare. As plant density increased, the number of reproductive culms per plant, culm diameter, and culm sucrose concentration significantly decreased. At 1,250 plants per hectare, the number of reproductive culms per plant, culm diameter, and culm sucrose averaged 70, 10.2 mm, and 63.2 g kg'1, respectively. Nitrogen removed with biomass significantly increased as biomass yield increased with plant density. At a density of 10,000 and 20,000 plant per hectare, the amount of nitrogen removed annually in the harvested biomass averaged 88 kg ha'1. The data suggest that plant populations of 10,000 plants per hectare would product the greatest annual biomass yields; however, biomass yield declined significantly with production year suggesting that nutrient deficiencies at high plant densities constrains biomass yield. Research is needed to determine the nutrient requirement for Ravenna grass to sustain biomass production at a density of 10,000 plants per hectare.