Reclamation of a Badarkhali hot spot of acid sulfate soil in relation to rice production by basic slag and aggregate size treatments under modified plain–ridge–ditch techniques

Abstract

A field experiment was conducted for the reclamation of a Badarkhali hot spot of acid sulfate soil manipulated by flash leaching followed by basic slag (BS) at 10 t ha^?1 (BS₁₀) and 20 t ha^?1 (BS₂₀) and aggregate sizes (A) of soil less than 20 mm (A₂₀) and less than 30 mm (A₃₀) treatments under two different techniques (Tech 1: pyrite layer at top, jarosite layer at middle and topsoil at the bottom of the ridge; Tech 2: topsoil at top, pyrite layer at middle and jarosite layer at the bottom of the ridge). Responses to two cultivars of rice (Pizam [local cultivar] and BR 14 [high yielding cultivar]) with the treatments were evaluated. The initial soil had a very low pH(H₂O) 4.0 and a high electrical conductivity (EC) of 1.4 m S^?1, and the pyrite content was 68 g kg^?1. The exchangeable Mg content of the soil was approximately twice that of Ca and the Al content was at a highly toxic level. The average soil data of all the treatments, except for the control plots (where no amendment was applied), after harvesting of rice increased by 1.1 units for soil pH and 17–524% for the contents of N, P, Ca and Mg, while the concentrations of Fe, Al, Na, Cl^? and SO₄ ^2– decreased by 30–94% compared with the initial soil. The maximum growth and yield of rice grains (4.4 t ha^?1) were obtained by the Pizam compared with the BR 14 (4.0 t ha^?1) in the A₂₀BS₂₀ treatment in the ridges of Tech 2. The lowest grain yields of 0.02 (BR 14) and 0.07 t ha^?1 (Pizam) were recorded for the control plots. The other treatments also resulted in significantly (P ≤ 0.05) improved performance on rice production. The highest N, P, K, Ca and Mg contents in the shoots of BR 14 and Pizam rice were obtained under the A₂₀BS₂₀ treatment followed by the A₂₀BS₁₀ ≥ A₃₀BS₂₀ treatments. Application of A₂₀BS₂₀ under Tech 2 is the most appropriate reclamation option and the local Pizam is the most suitable rice for this soil.