Effect of Foliar Ferrous Sulphate Application on Alfalfa (Medicago sativa L.) Leaf Fe Content, Photosynthetic Capacity and Yield

Alfalfa (Medicago sativa L.) is a vitally important forage crop. Due to its perennial characteristics, a gradual decline of soil nutrients (especially micronutrients) leads to a reduction of grass quality. Numerous studies have reported a direct relationship between ferrite levels and physiological function of plants. The present study investigates the impact of ferrite levels on alfalfa and tests five ferrous sulphate concentrations and three spraying frequencies. To investigate the influence of iron on alfalfa photosynthesis and iron uptake, we measured photosynthetic capacity and hay yield of alfalfa on iron deficient soil. We furthermore investigated the effects of iron on alfalfa yield and explored its mechanism of action. The results revealed that the wiron fertilizer sprayed at the appropriate concentration (0.6%-0.8%) increased the F_v/F_m and F_v/F₀ of the photosystem II complex. Spraying furthermore increased electron transport rate and photochemical quantum yield, reduced non-irradiative energy dissipation, and hence increased the photosynthetic rate and hay yield of alfalfa. Two applications of 0.6% ferrous sulphate spray increased the chlorophyll concentration of alfalfa by 26%. Three applications increased hay yield by 22% compared with check. Two applications of 0.8% spray increased photosynthetic rate by 42% and three applications increased the iron content of leaves by 117%. These results indicated that applying Fe (foliar-applied) from seedling to squaring stage improved the photosynthetic capacity and yield of alfalfa.