ABSTRACT
Nano-gypsum was used in this study to reclaim the sodic soils collected from Kukkambakam village of B.N Kandriga (Mandal), Chittoor district during 2021-22. Nano-gypsum was synthesized and characterized in the Department of Soil Science and Agricultutal Chemistry, Regional Agricultural Research Station, Tirupati. Two amendments viz., nano-gypsum (NG) and conventional gypsum (CG) were used in a pot culture experiment that was set up using a completely randomized design (CRD). The treatments involves combination of primary nutrients (N, P2O5 and K2O) with two sources of amendments such as conventional gypsum and nano-gypsum are: Control (T1), RDF (30:40:50 kg N:P2O5:K2O ha-1) (T2), RDF + 100 % GR as conventional gypsum (T3), RDF + 25 % GR as nano-gypsum (T4), RDF + 50 % GR as nano-gypsum (T5), RDF + 75 % GR as nano-gypsum (T6), RDF + 100 % GR as nano-gypsum (T7) and replicated four times. The response of groundnut (Dharani) grown in the reclaimed soil was studied. The soil was non calcareous, non saline sodic with a pH of 8.79 and ESP of 35.05 Per cent.
The physical, chemical, spectral (SEM, TEM and FT-IR) and structural (XRD) properties of the synthesized nano-gypsum were studied. The surface area of the nano-gypsum is 900 m2g-1. Conventional gypsum appeared as scattered and sparse in the SEM picture while, nano-gypsum was clustered and consolidated. Gypsum was found to be loaded into the nano-clay according to the FT-IR spectra and according XRD pattern crystal structure was monoclinic.
The results of the percolation study revealed the significant displacement of Na+ from the exchangeable clay complex by the Ca+2 which was originated from the nano-gypsum. Maximum decline in the concentration of Ca+2 in the leachates over a period of time was clearly observed with the application of nano-gypsum.
In the pot culture experiment, sodic soil was analyzed for its initial parameters like, pH, EC, CEC, ESP, exchangeable Na+, Ca+2 and Mg+2 . The plant growth attributes viz., plant height, branches plant-1 and dry matter production were recorded at flowering and harvest stage of crop. Yield and the yield attributes viz., number of pods plant-1, 100 pod weight, 100 kernel weight, pod yield and haulm yield were recorded. The total nutrient content macronutrient (N, P, K, Ca+2, Mg+2 and S) and micronutrients (Fe, Mn, Zn and Cu) in the haulm were analyzed at flowering and harvesting stages and the nutrient uptake by plant was also determined. The post harvest soils were analyzed for the available macronutrient (N, P, K, Ca+2, Mg+2 and S), micronutrients (Fe, Mn, Zn and Cu) and soil organic carbon.
On reclamation, pH of the soil was reduced to 7.96 and ESP to 8.07 per cent with the application of RDF + 100 % GR as nano-gypsum (T7). Maximum concentration of Na+ in the leachates recorded by the application of RDF + 100 % GR as nano-gypsum (T7) indicates the successful reclamation of sodic soil. Reclamation with RDF + 100 % GR as nano-gypsum (T7) also improved the physical properties of the sodic soil by reducing the bulk density to 1.27 Mg m-3 from 1.32 Mg m-3 in the control (T1).
Groundnut responded well to the reclamation by gypsum application and recorded significantly higher number of pods plant-1 in RDF + 100 % GR as nano-gypsum (T7), when compared to control. The highest nutrient uptake (N, P, K, Ca+2, Mg+2, S and micronutrients) at flowering and harvesting was recorded with the application of RDF + 100 % GR as nano-gypsum (T7). Groundnut grown in the soil reclaimed with RDF + 100 % GR as nano-gypsum (T7) recorded the highest pod yield (42.50 g pot-1) and haulm yield (61.69 g pot-1). The application of RDF + 75 % GR as nano-gypsum (T6) was proven to be effective as it was comparable to RDF + 100 % GR as conventional gypsum (T3) at both the stages of groundnut crop.
The effectiveness of nano-gypsum at RDF + 100 % GR as nano-gypsum (T7) in recovering sodic soils was significantly higher than that of conventional gypsum at RDF + 100 % GR as conventional gypsum (T3) which can be attributed to its smaller particle size, greater surface area, and consequently greater solubility. Moreover, application of RDF + 75 % GR as nano-gypsum (T6) was comparable to RDF + 100 % GR as conventional gypsum (T3).
According to the findings of the current study, nano-gypsum can be considered as a viable alternative to conventional gypsum for reclaiming sodic soil at either 100 % or 75 % GR.