Biomass and nitrogen-use efficiency of grain sorghum (Sorghum bicolor L.) with nitrogen and supplemental irrigation in Coastal Plain Region, USA

Authors: Sigua, Gilbert; Stone, Kenneth - Ken; Bauer, Philip; Szogi, Ariel

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2018
Publication Date: 2/13/2018
Citation: Sigua, G.C., Stone, K.C., Bauer, P.J., Szogi, A.A. 2018. Biomass and nitrogen-use efficiency of grain sorghum (Sorghum bicolor L.) with nitrogen and supplemental irrigation in Coastal Plain Region, USA. Agronomy. https://doi.org/10.2134/agronj2017.09.0533.
DOI: https://doi.org/10.2134/agronj2017.09.0533

Interpretive Summary: High-yielding grain crops, such as corn (Zea mays, L.) and sorghum (Sorghum bicolor, L.) require large application rates of nitrogen (N) fertilizer to reach optimal yields. Widespread use of irrigation, along with use of adapted hybrids and greater use of fertilizer, has greatly increased average yields of grain sorghum in Central and semi-arid Southern High Plains region of the United States. However, little is known about the response of grain sorghum to the combined effects of irrigation supply and N fertilization in humid Coastal Plains region of the United States. Hence, it is helpful to develop sound technologies for resource management that maximize the efficient use of water and nutrients to achieve sustainable agricultural production. The objective of this study was to determine the effects of N fertilization (0, 85 and 170 kilogram nitrogen per hectare (kg N ha-1) with supplemental irrigation (SI) (0, 50 and 100% of the full irrigation rate) on aboveground biomass (AB), nitrogen uptake (NU) and nitrogen-use efficiency (NUE) of two varieties (Var) of grain sorghum in Coastal Plain region of the United States. We demonstrated that our results support our hypothesis that the negative impacts of water stress and nutrient deficiency could be mitigated by supplemental irrigation and N fertilization in sorghum production. The following conclusions are drawn from this study: (1) among the plots with N treatments, the greatest aboveground biomass of grain sorghum was from plants treated with 170 kg N ha-1 (3,739.3±2,280 kg ha-1) followed by 85 kg N ha-1 (3,644.1±2,061 kg ha-1). The least amount of aboveground biomass was from plots with 0 kg N ha-1 (2,891.9±1,576 kg ha-1); (2) nitrogen uptake of sorghum biomass and sorghum grain when averaged across variety and years were both significantly affected by SI and N fertilization. Sorghum in plots with 100% SI had the greatest N uptake of sorghum biomass of 67.9±37 kg ha-1 and N uptake of sorghum grain of 52.8±19 kg ha-1; and (3) overall, the estimated increase in N-use efficiency between the 0 and 100% SI of about 79% from plots with 85 kg N ha-1 and 126% increase of N use efficiency from plots with 100 kg N ha-1. Our results suggest that effective use of water in irrigation and maintaining a sufficient amount of N will improve the biomass, N uptake and N-use efficiency of grain sorghum in humid Coastal Plain region of the United States.

Technical Abstract: Poor rainfall distribution and soil conditions such as high soil strength, low water holding capacity of soils and poor soil fertility in the humid Coastal Plain region may affect production of grain crops. Nitrogen insufficiency and water stress can both reduce crop yield, but little information is available on whether the interaction effects of supplemental irrigation (SI) and nitrogen (N) fertilization can alleviate both water stress and nutrient deficiency in humid region. A field sorghum study was conducted in 2013 and 2014 under a variable-rate center pivot. The objective of our study was to determine the combined effects of N fertilization (0, 85 and 170 kilogram, kg N per hectare, ha-1) and SI (0, 50 and 100 percent, % of the full irrigation rate) on aboveground biomass (AB), nitrogen uptake (NU) and nitrogen-use efficiency (NUE) of two varieties (Var) of grain sorghum in Coastal Plain region of the United States. Aboveground biomass and NU varied with SI (p=0.001) and levels of N (p=0.001). In irrigated treatments (50% SI and 100% SI), the rates of 85 and 170 kg N ha-1 resulted in significantly higher AB, NU and NUE. Averaged across years, Var, N and SI, grain sorghum applied with 170 kg N ha-1 and 100% SI had the greatest AB of 3,997 kg ha-1. Sorghum with 85 and 170 kg N ha-1 and 100% SI treatment had the greatest NUE of 60.5% and 57.1%, respectively. We demonstrated that our results support our hypothesis that the negative impacts of water stress and nutrient deficiency could be mitigated by SI and N fertilization. Our results further suggest that effective use of water in irrigation and maintaining a sufficient amount of N will improve the AB, NU and NUE of grain sorghum in humid Coastal Plain region of the United States.