Evaluation of phosphogypsum as an ameliorant in acid soil under wetland ecosystem

Abstract

The present investigation entitled “Evaluation of phosphogypsum as an ameliorant in acid soil under wetland ecosystem” was conducted at the Dept. of Soil Science and Agricultural Chemistry, College of Agriculture, Vellanikkara, Kerala Agricultural University, Thrissur during 2018-2022. The study aimed to assess the suitability of phosphogypsum and its combination with liming materials or rock phosphate and organic manure, for the amelioration of soil acidity, management of iron and aluminium toxicity, enhancement of nutrient availability, and finally to increase rice productivity under wetland conditions. The investigation was conducted in four experiments viz., a soil characterization study, a pot culture experiment, an incubation study, and a field experiment. The first three experiments were conducted at the College of Agriculture, Vellanikkara, Thrissur and the field experiment was carried out in a farmer’s field at Elavathur in Mullasseri Kole land of Thrissur district. Initially, ten soil samples were collected from Pavutai Padashekharam of the Mullasseri panchayath before the cultivation of the crop and were characterized for its major physical, chemical, and biological properties. The pot culture experiment with rice as a test crop was carried out on the acid soil collected from Pavutai padashekharam to study the effect of phosphogypsum and its combination with liming material or rock phosphate and organic manure, on soil acidity and availability of nutrients with 13 treatments comprising T1 (PG), T2 (RP), T3 (Lime), T4 (Dolo), T5 (PG+lime+VC in the ratio 1:8:1), T6 (PG+Dolo+VC in the ratio 1:8:1), T7 (PG+RP+VC in the ratio 1:8:1), T8 (Dolo+RP+VC in the ratio 5:4:1), T9 (PG+lime in the ratio 1:3 ), T10 (PG+Dolo in the ratio 1:3), T11 (PG+RP in the ratio 1:3), T12 (Dolo+RP in the ratio 1:1 ) and T13 (Control). The combinations of amendments in different ratios were based on the Ca requirement of the soil. These treatments were applied to the soil for providing the required Ca quantity of 140 kg Ca ha-1 which is decided based on the soil pH and the added quantity of different amendments was decided based on the Ca content of the amendments. Phosphogypsum @ 823.09 kg ha-1, rock phosphate @ 605.68 kg ha-1, lime @ 197.07 kg ha-1 and dolomite @ 466.46 kg ha-1 were supplied in treatments with their sole application.