Biomass Yield and Nutrient Responses of Switchgrass to Phosphorus Application

Abstract

Increasing desire for renewable energy sources has increased research on biomass energy crops in marginal areas with low potential for food and fiber crop production. In this study, experiments were established on low phosphorus (P) soils in southern Oklahoma, USA to determine switchgrass biomass yield, nutrient concentrations, and nutrient removal responses to P and nitrogen (N) fertilizer application. Four P rates (0, 15, 30, and 45 kg Pha −1 ) and two N fertilizer rates (0 and 135 kg Nha −1 ) were evaluated at two locations (Ardmore and Waurika) for 3 years. While P fertilization had no effect on yield at Ardmore, application of 45 kg Pha −1 increased yield at Waurika by 17% from 10.5 to 12.3 Mg ha −1 . Across P fertilizer rates, N fertilizer application increased yields every year at both locations. In Ardmore, non-N-fertilized switchgrass produced 3.9, 6.7, and 8.8 Mg ha −1 , and N-fertilized produced 6.6, 15.7, and 16.6 Mg ha −1 in 2008, 2009, and 2010, respectively. At Waurika, corresponding yields were 7.9, 8.4, and 12.2 Mg ha −1 and 10.0, 12.1, and 15.9 Mg ha −1 . Applying 45 kg Pha −1 increased biomass N, and P concentration and N, P, potassium, and magnesium removal at both locations. Increased removal of nutrients with N fertilization was due to both increased biomass and biomass nutrient concentrations. In soils of generally low fertility and low plant available P, application of P fertilizer at 45 kg Pha −1 was beneficial for increasing biomass yields. Addition of N fertilizer improves stand establishment and biomass production on low P sites.

Switchgrass Biofuel Production on Reclaimed Surface Mines: I. Soil Quality and Dry Matter Yield

“…Schmer et al [17] measured annual average biomass yields of 5.2 to 11.1 Mg ha −1 of switchgrass when managed as a biomass energy crop on marginal cropland in the northern Great Plains, USA. Even greater yields on marginal lands in Oklahoma were shown by Kering et al [8], with switchgrass producing 16.0 Mg ha −1 during the fifth year of production. Along newly constructed highways in West Virginia with rocky soils, switchgrass achieved good cover and soil stabilization after 2 years, although yields were not measured [21].…”

“…Determining economically optimum N application rates will help switchgrass producers maximize profits with high yields while reducing fertilizer and environmental costs. Unfortunately, there is no consensus on the amount of nutrients, particularly N, to apply to a field for switchgrass growth [8,16] because the amount varies with soil type and location [7]. The amount of N required by switchgrass is a function of the desired yield, N concentration of the biomass, potential productivity of the site, soil nutrient supply, and management practices [27].…”

“…Without fertilization, one study in Georgia showed 8.6 Mg ha −1 of biomass production averaged over the first 4 years of switchgrass growth [9]. Kering et al [8] showed only an 18 % increase in Alamo production with an N fertilizer rate of 135 kg N ha −1 and a potassium (K) rate of 68 kg K 2 O ha −1 as compared to the no fertilizer control. This indicates that switchgrass grown on marginal lands may benefit from the addition of K along with N. Switchgrass can grow without fertilizer inputs, but it clearly responds positively to fertilizer [12].…”

Economic Evaluation of Switchgrass Feedstock Production Systems Tested in Potassium-Deficient Soils

“…This suggests that systems with N applications did not realize statistically greater yields .0001 † The letters represent harvest system, the first number is kg of N ha −1 and second number is kg of K 2 O ha −1 ‡ P values are based on Fisher's protected F tests § Means reported for yield, total cost, gross revenue, and net return for the feedstock production systems within a row marked with the same letter are not significantly different based on an LSD test (P <0.05) ¶ Costs of fertilizer was estimated assuming a base-case N price of $1.43 kg −1 and a K 2 O price of $1.17 kg −1 # Revenue was calculated using a base-case feedstock price of $83 Mg −1 than systems without N applications, which is in contrast to what was found by previous studies [7,14]. However, we point out that these studies were not conducted in K-deficient soils.…”

“…Extensive soil testing has revealed that a substantial percentage of acres in the southern Great Plains are deficient in potassium (K), primarily those in the eastern areas that are comprised of sandy soils and receive greater than 889 mm of rainfall each year [2]. At present, most switchgrass fertilizer management studies have mainly focused on the benefits and costs associated with nitrogen (N) fertilizer as the primary limiting nutrient [3][4][5] and a few studies have focused on phosphorus (P) fertilizer [1,6,7]. However, little information is available regarding the costs and benefits associated with N and K fertilization on switchgrass produced in K-deficient soils.…”