Assessment of Suitable Extractant for Estimating Soil Available Potassium in Acidic Soils of Rice-Lentil Cropping System in India

Abstract

The productivity and sustainability of rice–lentil cropping systems in acidic soils are severely constrained by potassium deficiencies, exacerbated by intensive cropping and imbalanced fertilization. Potassium plays a crucial role in plant growth, yield, stress tolerance and nutrient use efficiency. However, the relationship between soil K dynamics, its availability to crops, and the impact on yield attributes remains inadequately explored in acidic soils. The present study was carried out to assess the relative suitability of extractants for predicting the available potassium status of rice - lentil cropping system soil in acidic condition. A pot experiment was conducted under the College of Agriculture, Central Agricultural University, Iroisemba, Imphal, Manipur to determine the K application response and the most suitable extractant in acidic soils of rice-lentil cropping system. A total number of 25 bulk soil sample (0–15 cm) were collected from rice–lentil fields of Thoubal District, Manipur, India using simple random sampling method. The soils were analysed for available potassium estimated by six extractants. The available K extracted using different extractants varies, with the strong positive correlation with potassium extracted by 1N NH4OAc (r = 0.924, p-value < 0.001) followed by Morgan’s Reagent (r = 0.802, p-value < 0.001), while others either overestimated or underestimated available K. This study suggests that the available potassium extracted with 1N NH4OAc is closely linked to higher yields, making it the most effective extractant for predicting plant response and yield. Further, also provides valuable diagnostic thresholds for guiding potassium fertilization in similar agro-ecological zones.