APPRAISAL OF TEMPORAL VARIATION IN SOIL AND FORAGE IRON AND ZINC IN A PASTURE UNDER SEMI-ARID ENVIRONMENTAL CONDITIONS

In the present investigation we determined the effect of sampling periods on iron and zinc contents of soil and forage of a pasture from Sargodha (Pakistan) consisting of plants mainly of Brassicaceae. Soil and plant samples were taken six times at a regular interval of 15 days. They were then wet digested and analyzed for Fe and Zn. The data showed that there was no significant influence of sampling periods on both soil and forage Fe and Zn contents. However, there was statistically non-significant variation in mineral contents of soil and forage showing an inconsistent pattern of fluctuation with sampling periods. The highest value of soil Fe was found at the 3 rd period and the lowest at the 5 th period of sampling. Mean values of soil Fe varied from 7.5-7.7 mg/kg at different periods of sample collection. The highest value of forage Fe was found at the 1 st period and the lowest at the 6 th period ranging from 57.85-64.67 mg/kg across all sampling times. Mean values of soil Zn varied from 0.36-0.15 mg/kg at different sampling periods. Forage shoot Zn concentration was the highest at the 1 st period and the lowest at the 5 th period during the whole investigation period. Forage Zn ranged from 13.22 to 23.92 mg/kg in leaves/shoots. There was an inconsistent variation in its concentration at different sampling periods. The concentration of Zn both in soil and forage were at severe deficient levels indicating the need of soil amendment with zinc containing fertilizers to enhance the Zn contents of the pasture soil and in turn availability of Zn to forage from soil. These Fe concentrations were within the marginal and severe deficient levels for the ruminant requirements. The naturally upset balance of Fe offers a potential hazard not only for both pastures, but also the Fe status of grazing ruminants therein.