Impact of phosphorus levels and PSB dosages on soil microbial populationand enzymatic activities in a vertisol

Abstract

A pot culture experiment was carried out to study the impact of phosphorus levels and PSB dosages on soilmicrobial population and enzymatic activities in a vertisol during kharif 2018 at College of Agriculture, Raichur using maizeas a test crop. A total of eleven treatments that includes different levels of phosphorus which are studied either alone or incombination with two levels of phosphate solubilizing bacteria (PSB). These treatments were replicated thrice and arrangedin a completely randomized block design. The results revealed that soil application of PSB at 25 kg ha-1 along with completedosage of NPK showed a significant effect on total bacterial count (2.67 × 109 g-1 of dry soil). Moreover, it also recordedthe higher soil enzymatic activities viz., dehydrogenase activity (11.68 μg TPF g-1hr-1) and alkaline phosphatase activity(14.1 μg pNP g-1hr-1) and was at par with the treatment receiving 100 % NK + 75 % P + PSB @ 12.5 kg ha-1 and was superiorto other treatments. Apart from these 100 % NK + 75 % P + PSB @ 12.5 kg ha-1 showed a significantly highest PSB countin soil (6.50 × 104 g-1of dry soil). Lower soil microbial population and enzymatic activity were obtained in absolute controland thus indicated that application of inorganic phosphorus as well as treating the soil with PSB @25 kg ha-1 is beneficialin terms of higher microbial population and enzymatic activities in soil. A significant positive correlation was foundbetween available P with plant growth parameters indicating that with the addition of PSB more P was solubilized andpositively supported plant growth