Nutrient Pools in Bermudagrass Swards Fertilized at Different Nitrogen Levels

Abstract

Nitrogen (N) fertilization affects grassland herbage accumulation and nutritive value, but its effect on the distribution of nutrients among soil and plant nutrient pools is less understood. This 2‐yr study determined the effect of N fertilization levels of rotationally stocked ‘Tifton 85’ bermudagrass (Cynodon spp.) pastures on nutrient concentration and content in soil (top 20 cm), live root‐rhizome mass, live herbage mass, and aboveground plant litter pools. Treatments were 50, 150, and 250 kg N ha−1 yr−1. Greater N fertilization increased N concentration in all plant nutrient pools and potassium (K) concentration in live herbage and plant litter, but plant‐pool phosphorus (P) concentrations changed little across N levels. With increasing N fertilization, live herbage (118–159 kg ha−1) and plant litter (8–14 kg ha−1) K pools increased linearly, but the Mehlich‐1 extractable soil K pool decreased linearly (182–139 kg ha−1); live herbage (50–92 kg ha−1), plant litter (30–49 kg ha−1), and root rhizome (63–95 kg ha−1) N pools also increased with increasing N fertilization. The proportion of K in various pools was affected more by N fertilization than were proportions of N, P, or carbon. Soil was the dominant pool for all nutrients, with the exception of K in pastures fertilized at the greatest N level. Increasing N fertilization increased the proportion of K and N contained in plant pools and decreased the proportion in soil. Although N fertilization affected quantity and proportion of nutrients in pools in Tifton 85 pastures, changes occurred to a limited extent, with the exception of plant and soil K pools.

Potassium and Nitrogen Fertilization Effects on Jiggs Bermudagrass Herbage Accumulation, Root–Rhizome Mass, and Tissue Nutrient Concentration

“…The increase in K content was due to greater root–rhizome mass at greater levels of N fertilization. Liu et al (2017) observed that N fertilization levels from 44 to 223 lb/acre did not change root–rhizome K concentration in Tifton 85 bermudagrass; however, increased N levels resulted in increases in K content and overall plant demand for K. There was no effect of N fertilization on root–rhizome K content at 0K, 18K, and 36K, but linear and quadratic responses were observed at 72K.…”

Physiological responses and forage accumulation of Marandu palisadegrass and Mombaça guineagrass to nitrogen fertilizer in the Brazilian forage‐based systems

“…Nitrogen accounts for 40%–70% of the total leaf nitrogen, being a constituent of many cell components, including chlorophyll, proteins and enzymes associated with the photosynthetic process (Taiz et al., 2017). Therefore, radiation‐use efficiency and its conversion into carbohydrates in a given forage genotype (Pedreira, Pedreira, & Lara, 2015) will depend on the soil (Luo et al., 2015) and tissue (Liu, Sollenberger, Silveira, Vendramini, & Newman, 2017) nitrogen status.…”

Soil organic carbon sequestration calculated from depth distribution

“…estimated from soil depths of 0–30, 30–60, and 60–90 cm was 3.3 ± 1.7, 0.9 ± 0.5, and 0.9 ± 0.5 Mg ha –1 , respectively (Adams et al., 1966). In other studies, root mass to 20‐cm depth only was 6.7 ± 1.2 Mg ha –1 under a variety of warm‐season grasses in Florida (Siqueira da Silva et al., 2019), 9.4 ± 1.5 Mg ha –1 under bermudagrass with different N fertilizer levels (Liu et al., 2017), and 2.5–5.5 Mg ha –1 under bermudagrass (Alderman et al., 2011). Warm‐moist conditions persist throughout the year in this region and lead to high decomposition rates, contributing to relatively low SOC concentrations.…”