Effects of Variety, Nitrogen Levels and Their Interactions on Some Growth Parameters and Fibre Fractions of Two Sorghum Varieties

Abstract

Sorghum (Sorghum bicolor L. Moench) is an important cereal and forage crop in Nigeria's semi arid regions due to its drought tolerance and adaptability to low-fertility soils. Optimizing nitrogen fertilization for different sorghum varieties can improve growth and forage quality, addressing feed shortages for ruminant livestock. This study evaluated the effects of variety, nitrogen levels (0, 60, and 120 kg N/ha), and their interactions on growth parameters (stem diameter, leaf width, tiller number) and fibre fractions (acid detergent fibre (ADF), neutral detergent fibre (NDF), lignin (LIG) of two sorghum varieties (Sweet sorghum and SAMSORG-17). A split-plot design with three replications was conducted at the National Animal Production Research Institute (NAPRI), Shika, Nigeria, during the 2024 rainy season. Results showed significant (p<0.05) Variety and Nitrogen interactions for stem diameter and leaf width. Samsorgh-17 exhibited a pronounced increase in stem diameter (4.43 - 7.02 cm) and leaf width (4.70 - 5.19 cm) with nitrogen application, whereas sweet sorghum showed minimal morphological response. Tillering number was unaffected by variety or nitrogen. Sweet sorghum showed improved forage quality with nitrogen, as ADF (30.68 -30.23%), NDF (70.30 - 68.42%), and lignin (8.23 - 6.98%) decreased progressively. Conversely, SAMSORG-17 showed negligible or negative responses, with ADF slightly increasing (31.20 - 32.12%) and NDF and lignin remaining unchanged. Fibre fractions also exhibited significant interactions. These findings indicate that nitrogen fertilization enhances forage quality in biomass-oriented varieties like sweet sorghum but provides limited benefits for grain-oriented varieties like SAMSORG-17. For optimal forage quality, sweet sorghum should be cultivated with 120 kg N/ha, while Samsorgh-17 performs best under moderate nitrogen inputs (60 kg N/ha) for stable forage and grain production. Variety-specific nitrogen management is recommended to maximize sorghum productivity, improve livestock feed quality, and enhance sustainable crop livestock systems.