干旱区生态环境知识资源中心

Four types of forages Bermuda grass (Cynodon dactylon), Bahia grass (Paspalum notatum), Star grass (Hypoxis hirsute), and Guinea grass (Panicum maximum) were collected from the Livestock Experimental Station Rakh Khaire Wala, located in the semi-arid region of central Punjab, Pakistan during two different seasons of 2003. Samples were collected and analyzed for iron (Fe), copper (Cu), zinc Zn), manganese (Mn), and selenium (Se) at eight sample dates after every two weeks during two consecutive seasons. No difference was found between winter and summer for forage Fe, Cu, Zn, Mn, arid Se. Forage Cu concentrations increased in summer for Bahia grass from 20.3 to 23.1 mu g/g. This species had the highest zinc concentrations 90.8 mu g/g in winter and had the highest forage Fe and Cu concentrations 130.0 and 23.1 mu g/g, respectively in summer. Star grass had the highest Mn concentrations 250.8 mu g/g in winter and its Se concentrations increased in summer from 0.033 to 0.042 mu g/g. Forage Se had the greatest increase in Guinea grass from 0.028 to 0.049 mu g/g in summer. The summer season did not show difference for concentrations of the five micro-nutrients. It is concluded that there is not a significant variation in micro-nutrient status of the forage due to seasonal changes. Only the forage Se concentrations increased in summer. However, the Se level was still insufficient to meet the requirements for grazing ruminants; while other four micro-nutrients in these forages were sufficient to meet the requirements.