Interactive Effect of Phosphorus and Boron on Their Temporal Soil Availability under Black Gram [Vigna mungo (L.) Hepper] Cultivation and Nodulation in Acid Inceptisol

Background: Meghalaya soils are highly acidic and phosphorus and boron are poor in supply leading to poor crop productivity. Low availability of phosphorus in these soils is due to fixation of phosphorus by Fe and Al oxides. Deficiency of boron in acidic soils of Meghalaya is due to coarse texture and leaching. The current study was conducted to find out the interactive effect of phosphorus and boron on their temporal soil availability, number of nodules in black gram and their dry weight. Methods: A field experiment comprising of four levels of phosphorus i.e. 0, 25, 50 and 75 kg P2O5 ha-1 and four levels of boron i.e. 0, 0.5, 1.0, 1.5 kg B ha-1 was conducted during 2019 taking black gram cv. PU-31 as test crop. The treatments were laid out in split plot design with main plot as phosphorus and sub plot as boron with 16 different treatment combinations and replicated three times in humid sub tropical climate of Meghalaya with acid Inceptisol having pH 4.99, available phosphorus 13.68 kg ha-1 and available boron 0.054 ppm. Result: The result revealed that temporal soil availability of phosphorus and boron increased with increase in phosphorus and boron doses, whereas it declined with progressive time intervals. Further, number of nodules in black gram and their dry weight show decrease with increase in time. Both these parameters increased significantly with increasing phosphorus and boron doses up to highest level. The optimum levels were recorded with combined application of 50 kg P2O5 ha-1 and 1.0 kg B ha-1 for number of nodules and 50 kg P2O5 ha-1 and 0.5 kg B ha-1 for dry weight of nodules.