Archives Des Sciences Vol 65, No. 11;Nov 2012 752 ISSN 1661-464X Variability of Hydrocyanic acid in fresh leaves of forage Sorghum grown under different soil moisture regimes Ahmad Sher, Muhammad Ansar, Muhammad Azeem Malik, Allah Wasaya Department of Agronomy, Pir Mehr Ali Shah-Arid Agriculture University Rawalpindi, Pakistan. Ghulam Shabbir, Department of Plant Breeding & Genetics, Pir Mehr Ali Shah-Arid Agriculture University Rawalpindi, Pakistan. Rahmatullah Qureshi (Corresponding author) Department of Botany, Pir Mehr Ali Shah-Arid Agriculture University Rawalpindi, Pakistan. * Corresponding Author, email: rahmatullahq@yahoo.com Abstract The dry land farming faces drought that subsequently resulted as crop failure in these areas. Livestock provides alternate sustenance and certainty to livelihood for poor masses in rain-fed areas against adverse climatic and minimal water stress conditions. Sorghum is grown as Kharif crop that provides forage for livestock in dry land farming. However, this crop produces Hydrocyanic acid (HCN) toxin when it faces drought which could be fatal to animals if ingested in greater quantity. Keeping in view, a pot experiment was conducted to evaluate variability of HCN production under glasshouse condition during the summer 2009 in fresh leaves of forage sorghum grown under different soil moisture regimes. Three moisture regimes (30, 50 and 70% of the field capacity) were applied to three sorghum forage cultivars (JS-2002, Chakwal sorghum and Local sorghum following a completely randomized design with five repeats. The results revealed that HCN contents reduced consistently with the progressive increase in the soil moisture availability and crop growth stage. The soil moisture @30% field capacity produced on an average 26% higher HCN than soil moisture @70% filed capacity that clearly indicated the effects of drought on HCN production. Among the cultivars, JS-2002 produced 51.9, 55.1 and 59.2% less HCN contents in compared to local sorghum at 5 th leaf, pre-booting and 50% heading stage, respectively revealed the genetic variability in sorghum cultivars. The genotype chakwal sorghum and soil moisture @50% field capacity produced moderate HCN contents among tested cultivars and moisture regimes. It is evident from this study that sorghum forage cv. JS-2002 produced less HCN at all soil moisture regimes compared to other cultivars studied. The present study suggests that sorghum cv. JS-2002 proved as safest cultivar and dry land farmers are advised to grow for forage production and harvest at 50% heading stage for safe feeding to their livestock. Keywords: Forage sorghum, Moisture regimes, Hydrocyanic acid, Growth stages 1. Introduction In dry land farming, where mostly crops fail to grow, livestock is an alternate sustenance to rural communities in rain-fed areas against aberrant climatic and water stress conditions. Availability of green fodder is main problem in livestock production in rain-fed area and the animals are often fed crop residues