Nitrogen Fertilizer Application Effects on Switchgrass Herbage Mass, Nutritive Value and Nutrient Removal

Abstract

Switchgrass (Panicum virgatum L.) can provide summer forage when forage production from cool‐season grasses is limited. This experiment was conducted over two growing seasons (2014 and 2015) to determine nitrogen (N) fertilizer application rate and time of harvest effect on switchgrass herbage mass, nutritive value, and nutrient removal. Treatments consisted of a split‐plot arrangement of five N rates (0, 45, 80, 135, and 180 kg ha−1) applied annually as main plots and harvest time (harvested in July for forage or October for biomass) as subplots in a randomized complete block design with three replications. Nitrogen rate × time of harvest interaction had no effect on herbage mass or nutritive value. Increasing N application rates increased herbage mass, crude protein, in vitro dry matter digestibility, and neutral detergent fiber concentrations, but not acid detergent fiber. A quadratic function described the relationship between herbage mass and N rate, with maximum yield occurring at 151 kg N ha−1. The economic optimum N rates ranged from 90 to 120 kg N ha−1 and depend on switchgrass hay price and N fertilizer costs. Generally, herbage mass was greater for switchgrass harvested for biomass, but nutritive value and nutrient removal were greater when switchgrass was harvested for forage. Switchgrass herbage mass and nutrient removal were greater in 2014 than in 2015. Our findings showed that N fertilizer rates for switchgrass under rain‐fed conditions need to be adjusted on the basis of expected herbage mass produced, hay value, and prior year N removal rates.

Perennial Energy Grasses: Resilient Crops in a Changing European Agriculture

“…NUE was maximized at a fertilization rate of 60 kg N ha −1 year −1 as compared with 120 kg N ha −1 year −1 . In switchgrass NUE decreased as well when N was raised from 45 to 180 kg ha −1 [38]. Small increments (about 9 kg of biomass per kg of nutrient applied) were registered by Lemus et al [39] at N fertilization from 0 to 270 kg N ha −1 , showing also for switchgrass the general pattern of NUE decreases with increasing N supply.…”

Productive potential of superior genotypes of Paspalum notatum Flügge in response to nitrogen fertilization

“…The 36N genotype presented the highest NUE when N was applied at 60 kg N ha -1 , but 60% and 80% reductions were observed for the levels equivalent to 180 and 360 kg N ha -1 , respectively. Obour et al (2017), who evaluated Panicum virgatum L. at increasing levels of N fertilization (0, 45, 90, 135, and 180 kg N ha -1 ), observed a linear reduction in NUE. The reduction in efficiency can be explained by the reduced capacity of the plant to absorb and use the nutrient for production, as well as possible soil leaching.…”

“…According to Seepaul et al (2016), several factors contribute to the amount of N removed by plant biomass, including the genotype and amount of N applied.NUE has been used to describe a plant's ability to acquire and use N to produce biomass, and is expressed as the yield of biomass produced per unit of N applied (Seepaul et al, 2016).In this sense, including this information as a tool for selecting genotypes of this species in forage breeding programs is important. Indirect calculation of NUE has been widely used owing to its practicality and low cost (Silveira et al, 2013;Obour et al, 2017). The most commonly used source of N in Brazil is urea; however, research data indicate volatilization losses of up to 30% of N. Measures that increase the NUE should be implemented in order to promote the management of an economically sustainable, forage quality production system with minimal negative environmental impact.…”

Soil microbial community structure and enzymatic activity responses to nitrogen management and landscape positions in switchgrass (Panicum virgatumL.)

“…In particular, little information is available on the response of soil microbial communities and soil enzyme activities to nitrogen rates and landscape positions. Proper nitrogen (N) management is required for efficient forage production (Obour, Harmoney, & Holman, 2017). Studies show that N is the most limiting nutrient for forage productivity, and application of N improves yield and nutritive value in warm season grasses (Agyin-Birikorang, Newman, Obour, & Kasozi, 2012;Silveira et al, 2015).…”