ABSTRACT

Soil salinity and seasonal dynamics are typical soil characteristics along the west coast of India. The low-to-high soil/water salinity are classified based on the nature, content and composition of salts: the salinity (SAR) and sodicity (ESP, RSC) hazards. Soil salinity has been characterized based on typical reflectance in 427, 487, 950, 1414, 1917, 2206, 2380 and 2460 nm bands using hyper-spectral remote sensing (HRS). The inverse relation between soil salinity and spectral reflectance indicated the hygroscopic properties of dominant salt. Recent studies on spectral properties of saline soils (EC 3.2 to 30.46 dS m⁻¹) have revealed an increasing trend from visible to SWIR1 and a dip at SWIR2 bands. Spectral properties of saline–sodic soils in IGP revealed i) a higher spectral response from dry-barren surface of a strongly (pHs >10) sodic soil and ii) a change in spectral response pattern due to vegetative cover and higher moisture content in irrigated soils. The results suggest for further validation of spectral data using natural salts. Studies on technical grade salts have indicated a relatively high reflectance of NaCl and CaCO₃ than Na₂CO₃, NaHCO₃, Na₂SO₄, CaSO₄.2H₂O (gypsum) and pyrite (FeS) salts; the later show a decreasing trend at higher wavelengths. Hygroscopic salts have shown prominent energy absorption of water molecules at 1400, 1900 and 2250 nm. The reflectance from surface soils varies with colour, texture, structure and surface roughness. Statistical and index-based models have also been successfully used for the diagnosis of soil salinity. The recommended methods for soil analysis, the available forms of nutrients and spatial variability studies are suggested for better salinity appraisal.

摘要

土壤盐分和季节动态是印度西海岸典型的土壤特征。从低到高的土壤/水盐度根据盐的性质、含量和组成进行分类：盐度 (SAR) 和钠度 (ESP, RSC) 危害。使用高光谱遥感 (HRS) 根据 427、487、950、1414、1917、2206、2380 和 2460 nm 波段的典型反射率表征土壤盐度。土壤盐分与光谱反射率的反比关系表明了优势盐的吸湿性。最近对盐渍土光谱特性的研究（EC 3.2 至 30.46 dS m ^-1) 显示了从可见到 SWIR1 的增加趋势和 SWIR2 波段的下降。IGP 中盐碱土的光谱特性显示：i）来自强（pH > 10）钠质土壤的干燥贫瘠表面的更高光谱响应和 ii）由于植被覆盖和灌溉中较高的水分含量而导致光谱响应模式的变化土壤。结果表明使用天然盐进一步验证光谱数据。对工业级盐的研究表明，NaCl 和 CaCO ₃的反射率比 Na ₂ CO ₃、NaHCO ₃、Na ₂ SO ₄、CaSO ₄ .2H _2高O（石膏）和黄铁矿（FeS）盐；后者在较高波长处显示出下降趋势。吸湿性盐在 1400、1900 和 2250 nm 处显示出水分子的显着能量吸收。表层土壤的反射率随颜色、质地、结构和表面粗糙度而变化。基于统计和指数的模型也已成功用于土壤盐分的诊断。为更好地评估盐分提出了土壤分析的推荐方法、养分的可用形式和空间变异性研究。