Effect of Graded Doses of Fluoride on Soil Microbial Activity, Growth and Yield of Okra (Abelmoschus esculentus L.) grown in Alfisols

Abstract

A field experiment was conducted at Department of Soil Science & Agricultural Chemistry, College of Agriculture, OUAT, Bhubaneswar in the year 2015 and 2016 to study the impact of different doses of fluoride on growth and yield of okra along with soil microbial activity like microbial biomass carbon (MBC), microbial biomass nitrogen (MBN) and dehydrogenase activity (DHA) in the post harvest soil. Graded doses of fluoride i.e. No fluoride, 100, 150, 200, 250 and 300 ppm F in form of hydrofluoric acid (HF) were applied as foliar spray. The highest fruit yield (34.5 q ha^-1) of okra was recorded with T₁ (No fluoride), whereas, the lowest yield (21.5 q ha^-1) was observed with T₆ (foliar spray of F @ 300 ppm as HF). The fruit yield decreased significantly with increasing doses of fluoride. The decrease in yield was the highest (37.7%) with T₆ (foliar spray of F @ 300 ppm as HF) over control where as lowest value of 23.5% was observed with T₂. Significantly highest total chlorophyll content (4.5 mg g^-1 fresh leaf) was observed with T₁ which decreased to the lowest value of 2.3 mg g fresh leaf (T₆) due to increasing doses of fluoride. Soil microbial carbon increased up to 30 days after sowing (DAS) and decreased thereafter up to 42 DAS irrespective of fluoride doses. Except control, microbial biomass nitrogen (MBN) increased with increased doses of F up to 150 ppm in all the growth stages except zero DAS. However, MBN value decreased in all the growth stages except zero DAS with increased dose of F from 150 ppm to 300 ppm. The soil dehydrogenase activity was increased due to application of graded doses of F irrespective of growth stages.