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.