Effect of Irrigation and Intensive Cultivation on Soil Properties: A Case Study on Calcareous Soils in Ganges-Kobadak (G-K) Irrigation Project in Bangladesh

Abstract

The effect of long-term irrigation and intensive cultivation on three soil series was investigated. These soils were from a calcareous belt in the G-Kirrigation project area in Bangladesh, which had experienced declining crop yields. In order to evaluate the effect, if any, of irrigation and intensive cultivation on soil properties, three soil series from irrigated and adjoining non-irrigated areas located in the same catena were studied. Soil properties such as organic carbon, CEC, electrical conductivity, potassium adsorption ratio, exchangeable sodium percentage, and ionic strength did not show any distinct changes between the investigated areas. The major changes identified between the irrigated and non-irrigated soils were pH, void ratio, maximum water holding capacity, water-soluble Na, ferrous iron, sodium adsorption ratio, available nitrogen, and free carbonate content. In this study, the correlations between the following soil properties were demonstrated in all the series: (i) exchangeable and water-soluble sodium, (ii) exchangeable and water-soluble potassium, (iii) void ratio and maximum water holding capacity. By applying t-test, the effects of cations on other cations, sodium adsorption ratio on free carbonate, and water-soluble sodium on water-soluble potassium were found to be insignificant. The present study indicated the necessity of further investigation of the relationship between the declining fertility and changes in soil carbonate.