Effects of Limited Irrigation and Nitrogen Rate on the Herbage Yield, Water Productivity, and Nutritive Value of Sorghum Silage

ABSTRACT

To evaluate the herbage yield and silage quality of sorghum as affected by nitrogen and irrigation levels, a 2-yr experiment (2017–2018) was conducted in a semi-arid region of Iran. Three irrigation levels (supply 100, 75, and 50% of soil moisture deficit as I₁₀₀, I₇₅, I₅₀) and three nitrogen levels (150, 300, and 450 kg urea ha⁻¹ as N₁₅₀, N₃₀₀, N₄₅₀) were evaluated. Increasing nitrogen levels increased green herbage yield (GHY), irrigation water use efficiency (IWUE), lactic acid (LA), propionic acid (PA), digestible organic matter (DOM), crude protein (CP), and metabolizable energy (ME) but reduced the pH, dry matter content (DMC), neutral detergent fiber (NDF), and acid detergent fiber (ADF) of silage. The I₁₀₀ compared to I₅₀ treatment, resulted in higher GHY (69%), ADF (4%), NDF (2%), DMC (5%), ash (4%), and LA (13%) but reduced the IWUE (14%), CP (15%), DOM (3%), GP (4%), and ME (3%). Overall, the I₇₅× N₄₅₀ can be considered as the suitable treatment for sorghum silage production in semi-arid regions by saving 24% of irrigation water and producing high GHY (117.52 Mg ha⁻¹) with the maximum IWUE (23.64 kg m⁻³) and high content of CP (88.5 g kg⁻¹) and PA (0.34 g kg⁻¹). In conclusion, the I₇₅× N₄₅₀ is introduced as the superior treatment; however, in conditions of severe limitation of water resources, it is recommended to irrigate silage sorghum with the supply of 50% soil moisture deficit with the application of 150 kg urea ha⁻¹ (I₅₀× N₁₅₀).

KEYWORDS:

• Fertilizer
• drought stress
• water use efficiency
• feed value
• volatile fatty acids

Abbreviations

I₁₀₀, I₇₅, I₅₀, the supply of 100%, 75%, and 50% soil moisture deficit, respectively; N₁₅₀, N₃₀₀, N₄₅₀, application of 150, 300, and 450 kg urea ha⁻¹, respectively; GHY, green herbage yield; IWUE, irrigation water use efficiency; DMC, dry matter content, CP, crude protein; NDF, neutral detergent fiber; ADF, acid detergent fiber; LA, lactic acid; AA, acetic acid; BA, butyric acid; PA, propionic acid; GP, gas production; DOM, digestible organic matter; ME, metabolizable energy.

Disclosure statement

No potential conflict of interest was reported by the author(s).