Adsorption and Desorption Behaviour of Phosphorus as Influenced by Integrated Phosphorus Management Modules in Pigeonpea-Wheat System

Abstract

Sustainable phosphorus (P)-management is highly pertinent in the present day agriculture as global Preserve is highly limited. Adsorption-desorption studies help elucidate complex phosphorus chemistry influenced by management practices. The present investigation has been taken up to ascertain the Padsorption- desorption pattern in pigeonpea (PP) (Cajanus cajan (L.) Millsp.)-wheat (W) (Triticum aestivum L.) system under alkaline Fluvisol. Field experiment was conducted for three years (2019-2022) in randomised block design with four replication having six treatments namely: T1: PP0-W0 (subscripts denote the P2O5 rate applied to the crop, in kg ha-1); T2: PP60– W60; T3: PP36-W36 + 5 t farmyard manure (FYM) ha-1 T4: PP36-W36+ 1 t poultry manure (PM) ha-1; T5: PPP36-W36+ 50% wheat residue (WR) ; T6: PP36-W36+ 50% WR + phosphate solubilizing bacteria (PSB) at ICAR-IIPR. Experimental findings showed, available P content was highest in PP36-W36 + PM and langmuir adsorption parameters like maximum P adsorption capacity (b) and affinity constant (k) was noted maximum in PP0-W0 and the trend of ‘b’ in pigeonpea follows: PP36-W36+ WR > PP60-W60 ³ PP36-W36+ WR > PP36-W36 + FYM = PP36-W36 +PM. Low maximum P buffering capacity (MPBC) due to reduced P-fixation in plots received PM indirectly refers to the need of lesser P-fertilisers in both the crops. In case of desorption, higher value of ‘a’ in PP0-W0 (121.26 and 135 in pigeonpea and wheat respectively) refers to the marginal P-supplying potential as compared to PP36-W36 + PM (67.62 in pigeonpea) and PP36-W36+ FYM (81.54 in pigeonpea). Also, a higher desorption index (DI) in control plots indicates inability of crops to utilise soil P due to high bonding energy. In the end, application of PP36-W36+PM improved P-availability and has higher potential to supply P to crops.