Spatial Distribution and Mapping of Available Nutrients in Paddy Fields of North Central Laterites of Kerala, India

Abstract

Soil fertility assessment is crucial for sustainable crop production, particularly in intensive rice-growing regions. The present study aimed to assess the spatial distribution of available nutrients across the rice-growing areas of the north-central laterite of Kerala and generating soil fertility maps to understand potential constraints. A total of 35 geo-referenced samples (0-15 cm depth) were collected, processed and analyzed for various soil properties. The soil pH varied from 4.09 to 6.22, averaging 5.15, indicating an acidic nature. Electrical conductivity remained low (0.03–0.37 dSm-1), ruling out salinity issues. Organic carbon content ranged from 04.20 to 30.0 g kg-1. Macronutrient analysis revealed that these soils were low in available nitrogen (56.45–169.34 kg ha-1) and potassium (30.24–119.24 kg ha-1) and mostly medium to high in available phosphorus. Available calcium (487.50–3318.75 mg kg-1) was sufficient in all samples, whereas 65.85% and 34.28% of samples were deficient in available magnesium and sulfur, respectively. Micronutrient assessment showed sufficient levels of available iron, copper, manganese, and zinc, while 62.85% samples were deficient in available boron. Nutrient index of nitrogen, phosphorous and potassium are categorised under low, medium and low classes, respectively. Spatial variability maps for available nutrients were generated using QGIS to visualize and interpret the nutrient distribution across the laterite rice-growing region. These maps revealed the prevalence of widespread multi-nutrient deficiencies in the north central laterite soils of Kerala. These findings provide valuable insights for optimizing nutrient management strategies to improve soil health and sustain rice productivity in north central laterites of Kerala.