The gypsum (CaSO 4 .2H 2 O) from diverse sources (mined vs. commercial) is commonly used for the reclamation of sodic soils around the world. The efficiency of soil reclamation differs widely with sodicity levels (slight, moderate, and strong), soil depth (surface vs. subsurface), and texture (coarse to fine) and also with irrigation water quality (good to saline with Sodium Adsorption Ratio [SAR] > 13) or sodic (Residual Sodium Carbonate [RSC] > 2.5 me L −1 ). Abrupt application of gypsum caused variable results of soil reclamation at the farm level. Based on the comprehensive reviews on the diverse outcome of gypsum‐based soil reclamation for the complex sodic (higher content of alkaline salts), saline‐sodic (rich in both alkaline and neutral salts), and calcareous soils (saturated with alakaline calcium salts) in the IGP, an attempt was made to synthesize a clear guideline for the field application of gypsum following the Gypsum Requirement (G.R.) method. The recommended method includes a thorough mixing of a suitable grade of powdered (mined) gypsum (in tons ha −1 ) with the topsoil layer (0–30 cm depth), raised field boundary during plowing (to vaoid losses of amendment), and ponding at least for 15 days with irrigation water (preferably ECe < 0.4 dS m −1 ) to complete the neutralization of carbonate and bicarbonate salts. The experimental data showed the significant reduction in soil pH (from more than 10.0 to less than 8.5), ESP (from 89.8 to less than 15), ECe (from 26.1 to less than 4.0 dS m −1 ), and the neutralization of Na 2 and NaHCO 3− to Ca 2 +, Mg 2 +, and salts and the increase in organic carbon content (due to the higher root biomass), followed by gypsum application in a strongly saline‐sodic soil (pH more than 9.5, ECe less than 15 dS m −1 ) at surface (0–30 cm) and subsurface (beyond 30 cm) depths, respectively. Spatial analysis data revealed significant areas (56%) of reclaimed sodic soils in Haryana state of the IGP. The block (micro‐)‐level database was also developed to precisely assess sodic areas for further soil reclamation at the farm scale. The reviews also revealed that the supplementary addition of farm and green manures performed well for the reclamation of highly complex calcareous (rich in concretionary and nodular calcium carbonate) and saline‐sodic soils in the IGP, respectively.
Soil is a highly complex and heterogeneous system resulting from the interaction of multiple environmental processes that act simultaneously over time and exhibit variable responses to anthropogenic influences. Soil texture is a fundamental property that exerts direct and indirect control over several geotechnical and eco‐hydrological attributes, strongly influencing the physical and mechanical performance of soils under different environmental conditions. Consequently, spatially distributed information on soil texture is essential for engineering investigations, land use planning, and environmental management. In Sorocaba (SP, Brazil), where the pedological classes Ferralsols and Podzols predominate, technical and scientific information regarding soil composition and hydrological dynamics is limited. Therefore, this study addressed soil texture, liquid limit, plastic limit, and plasticity index, seeking to establish relationships between these parameters and geotechnical or eco‐hydrological characteristics. Soil samples were collected at georeferenced locations and at two different horizons, followed by laboratory analyses and geostatistical interpolation of sand, silt, and clay fractions using variogram‐based geoprocessing techniques. The results demonstrated a predominance of sandy‐textured soils (71.3% and 70.9% in the surface and subsurface horizons, respectively), indicating increased susceptibility to erosion and influencing water infiltration and retention patterns, thereby providing valuable support for civil and environmental engineering projects associated with regional climatic seasonality. These findings also contribute to an improved understanding of soil performance and sustainable territorial and hydrological resource management strategies.
Water scarcity, climate variability, poor soil water retention, and nutrient loss are major concerns in agriculture. Hydrogels have emerged as promising candidates in countering these issues owing to their ability to absorb, retain, and release large quantities of water through their three-dimensional polymeric networks. These can withhold and release water, fertilizers, nutrients, and others and thus have the potential to improve water and nutrient management of soil. This review provides an overview of the fundamental principles governing the agricultural hydrogels, including their composition, physicochemical characteristics, swelling behavior, water retention and release mechanisms, gel fraction, biodegradability, soil–water relationships including matric potential, and the influence of environmental factors such as salinity and irrigation water quality on their performance. It also gives an outline of the classification of hydrogels and their advantages and limitations. This review further examines the diverse agricultural applications of these materials, such as soil conditioners, seed coatings, water retention agents, and carriers for fertilizers. Additionally, it analyzes the challenges that continue to limit their large-scale application, including scarcity of data on long-term field validation, incomplete understanding of soil and environmental factors, variability in degradation behavior under field conditions, and the need for crop- and soil-specific hydrogel formulations. Moreover, this review highlights the need for future research on field-scale validation, stimuli-responsive materials, environmentally sustainable and biodegradable hydrogel systems, the use of renewable and agricultural waste-derived feedstocks, and the practical and economic factors, including deficit irrigation and fertigation compatibility and the cost of adoption, that will determine real-world implementation.
Soil temperature regime (STR) controls soil biogeochemical cycles, hydrological processes, and crop suitability; however, no national–scale, multidecadal STR baseline has been developed for Nepal or for any Himalayan country due to limited soil temperature monitoring networks. Furthermore, studies on the shift of STR with the rise in air temperature amidst changing climate are limited in Himalayan regions across the globe. This study developed a national-scale soil temperature baseline for Nepal from 1970 to 2024 using ERA5-Land reanalysis accessed through Open-Meteo API, with bias correction and validated against the observed data from seven agrometeorological stations of the Department of Hydrology and Meteorology (DHM) spanning 129–2655-m elevation. ERA5-Land exhibited a cold bias of 2.1°C–2.6°C across all validated stations and depths, which was corrected using empirical quantile mapping. The bias-corrected result showed close agreement with observation at all four validated soil depths of 5, 10, 20, and 50 cm (MBE ≈ 0°C; NSE = 0.87–0.90; Willmott’s d = 0.97–0.98), which was further supported by the Bland–Altman plot. Soil temperature was vertically interpolated to standard depths using natural splines, and mean annual soil temperature (MAST) at 50 cm was classified and mapped by downscaling ERA5-Land (∼9 km) to 1-km resolution using regression-kriging with elevation as a covariate (LOOCV RMSE = 1.83°C, R2 = 0.965). Warm temperature regimes dominate low to mid elevations, with thermic and hyperthermic regimes comprising 58.79% of Nepal’s area, whereas pergelic and subgelic regimes (9.03%) occur at high elevations. Based on bias-corrected data, national mean soil temperature increased by 0.103°C per decade from 1970 to 2024 (Mann–Kendall p<0.001), accompanied by a 2.87% expansion of warm regime areas, which suggests an upward shift of the thermic regime along the elevation gradient. In marginal regressions, MAST was explained by both elevation (−0.53°C per 100-m elevation shift; R2 = 0.96) and air temperature (increased 0.85°C soil temperature per 1°C air temperature rise; R2 = 0.95). The baseline supports STR-informed agroecological zoning and climate impact assessment in data-limited mountain regions.
Irrigation water shortages during dry seasons have posed significant challenges to pomelo cultivation in recent years in the Vietnamese Mekong Delta. This study evaluated the effects of organic compost, biochar, and rice straw mulch on soil physicochemical properties and irrigation efficiency in pomelo orchards. A field experiment was conducted from December 2022 to May 2024 using a randomized complete block design with seven treatments and four replications. The treatments included conventional irrigation (control), water-saving irrigation, and water-saving irrigation combined with different organic amendments (rice straw mulch, organic compost, and biochar) in various combinations and quantities. Results showed that integrated irrigation and amendment treatments significantly improved soil pH, organic matter, porosity, water holding capacity, and saturated hydraulic conductivity while reducing soil bulk density (p≤0.05). Notably, water-saving irrigation combined with rice straw mulch (T3), compost (T4), biochar (T5), compost + biochar (T6), or compost + biochar + rice straw mulch (T7) significantly reduced irrigation water requirements during the dry season compared with conventional irrigation without organic amendments (control treatment). The reduction ranged from 42% to 59% across treatments, with the greatest reduction observed in T7. At the final assessment, T4, T6, and T7 produced significantly higher pomelo yields than T1 and T2, whereas T3 and T5 did not differ significantly from T1. These findings indicate that soil-moisture-based irrigation combined with organic amendment packages may improve soil conditions and reduce irrigation requirements in mature pomelo orchards under the nonsaline dry-season conditions measured at the experimental site.
