Effects of Limited Irrigation and Nitrogen Rate on the Herbage Yield, Water Productivity, and Nutritive Value of Sorghum Silage
Ali Farhadi, Farzad Paknejad, Farid Golzardi, Mohammad Nabi Ilkaee, Fayaz Aghayari
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).