Indo-Gangetic Alluvial Plains Research Articles

DIVERSITY AND DISTRIBUTION OF TERMITES (BLATTODEA: ISOPTERA) IN BHIWANI, HARYANA, INDIA

A comprehensive study was undertaken by collecting 51 samples of termites between July and October 2021 in three distinct zones within the Bhiwani district to analyze the termite diversity of the Bhiwani, Haryana region. The interplay of aeolian dunes characterizes the Bhiwani district?s ecological landscape. Nestled within the Indo-Gangetic alluvial plain, the Loharu Banger zone, and the ruggedness of the Aravalli Hills provide three distinct niches for termite diversity. The study sheds light on the intricate tapestry of termite life inhabiting these diverse ecological niches. Sample identification exhibited termites? affiliations to two prominent families, Termitidae and Rhinotermitidae and three subfamilies, Amitermitinae, Macrotermitinae, and Coptotermitinae. Further, delving into the taxonomy unveiled a total of ten termite species inhabiting the various locations across the three ecological regions of Bhiwani district including Coptotermes sp., Microtermes mycophagus Desneux, Odontotermes gurdaspurensis Holmgren and Holmgren, Odontotermes redemanni (Wasmann), Odontotermes obesus, Coptotermes kishori, Amitermes belli (Desneux), Microcerotermes sp., Odontotermes guptai Roonwal and Bose, and Odontotermes vaishno Bose. Various diversity indices, including species richness, Simpson?s diversity index, Shannon-Weaver index, and Pielou?s evenness index, were used to determine the relative abundance and distribution of termite species within each zone. These indexes offer a comprehensive view of termite community structure and ecosystem resilience. This pioneering research marks the first-ever documented record of termite biodiversity in Bhiwani district, Haryana. In a region where the study of termites had hitherto been scarce, this endeavor opens doors to a deeper understanding of these soil-dwelling architects of nature. It lays the foundation for future research and pest management strategies in this dynamic ecosystem.. KEYWORDS :Isoptera, Termite diversity, Taxonomy, Pest management, Soil ecology

Machine Learning Techniques for Phenology Assessment of Sugarcane Using Conjunctive SAR and Optical Data

Crop phenology monitoring is a necessary action for precision agriculture. Sentinel-1 and Sentinel-2 satellites provide us with the opportunity to monitor crop phenology at a high spatial resolution with high accuracy. The main objective of this study was to examine the potential of the Sentinel-1 and Sentinel-2 data and their combination for monitoring sugarcane phenological stages and evaluate the temporal behaviour of Sentinel-1 parameters and Sentinel-2 indices. Seven machine learning models, namely logistic regression, decision tree, random forest, artificial neural network, support vector machine, naïve Bayes, and fuzzy rule based systems, were implemented, and their predictive performance was compared. Accuracy, precision, specificity, sensitivity or recall, F score, area under curve of receiver operating characteristic and kappa value were used as performance metrics. The research was carried out in the Indo-Gangetic alluvial plains in the districts of Hisar and Jind, Haryana, India. The Sentinel-1 backscatters and parameters VV, alpha and anisotropy and, among Sentinel-2 indices, normalized difference vegetation index and weighted difference vegetation index were found to be the most important features for predicting sugarcane phenology. The accuracy of models ranged from 40 to 60%, 56 to 84% and 76 to 88% for Sentinel-1 data, Sentinel-2 data and combined data, respectively. Area under the ROC curve and kappa values also supported the supremacy of the combined use of Sentinel-1 and Sentinel-2 data. This study infers that combined Sentinel-1 and Sentinel-2 data are more efficient in predicting sugarcane phenology than Sentinel-1 and Sentinel-2 alone.

A knowledge-driven multi-criteria decision making- Analytical Hierarchy Process based geospatial modeling for the delineation of fluoride contamination zones in groundwater, Jamui district, Indo-Gangetic alluvial plains, India

This study presents a framework to delineate the potential fluoride contamination zones within the groundwater of the study area by employing GIS coupled with Multi-Criteria Decision Making-Analytical Hierarchy Process approach (MCDM-AHP). In this context, various groundwater contamination controlling hydrogeo-meteorological factors thematic layers were prepared in the GIS environment and assigned with an appropriate rating and weights. All the selected influencing factors were overlaid using a weighted overlaid index approach after normalizing the weights and ratings of the respective layers using the AHP technique and then computed the fluoride contamination zones (FCZs). The obtained results indicate that 61.50% (1101sq.km) of the total study area was delineated as a relatively safe zone (F < 1.5 mg/L) and the remaining 38.50% (689 sq. km) was demarcated under the unsafe zone (F > 1.5 mg/L). The proposed FCZs model corroborates a significant agreement of 85% with the 61 observed locations and thus testify to the model reliability. The present model requires local expertise for selecting influencing parameters and finalizing their importance towards model building.

Assessment and prediction of LULCC dynamics in a part of Indo-Gangetic Alluvial Plain (IGAP) using geospatial techniques on multi-temporal Landsat imageries

Assessment and prediction of LULCC dynamics in a part of Indo-Gangetic Alluvial Plain (IGAP) using geospatial techniques on multi-temporal Landsat imageries

Assessment of Potentially Toxic Elements Contamination on the Fertile Agricultural Soils Within Fluoride-Affected Areas of Jamui District, Indo-Gangetic Alluvial Plains, India

Assessment of Potentially Toxic Elements Contamination on the Fertile Agricultural Soils Within Fluoride-Affected Areas of Jamui District, Indo-Gangetic Alluvial Plains, India

Appraisal of Groundwater Quality with Human Health Risk Assessment in Parts of Indo-Gangetic Alluvial Plain, North India.

Groundwater contamination in the Indo-Gangetic alluvial plain has reportedly been affected by various factors, such as mineral dissolution, overexploitation, precipitation, and ion exchange. This study was designed to interpret the hydrochemical fluctuations in the groundwater sources of a rural area in Raebareli district. Groundwater is slightly alkaline and affected by the issues of fluoride, salinity, hardness, and nitrate. The Pollution Index of Groundwater significantly categorize 57% and 79% of the samples under the "insignificant pollution" category during pre-monsoon and post-monsoon periods. The Health risk assessment indicated the high susceptibility of children toward health risks. It also indicated that fluoride had greater impact than nitrate in the study area. The multivariate statistical analysis indicates that anthropogenic activities, such as agricultural practices, including excessive fertilizer application and improper domestic and cattle waste management, are probable causes of groundwater contamination through NO3-, Cl-, Na+, and K+. Furthermore, the base exchange index classified 71.43% samples in pre-monsoon and 78.57% in post-monsoon as Na-HCO3 type. The meteoric genesis index suggested that 78.57% and 85.71% of the samples belong to shallow meteoric water percolation type during pre- and post-monsoon periods, respectively. The Piper plots revealed that HCO3-Ca·Mg and SO4·Cl-Na + K type are the prominent facies in the area, with dominance of alkalis and weak acids. According to Gibbs plot, majority of the samples fall under "rock dominance" suggesting that "rock-water" interaction was the dominant natural process controlling the groundwater chemistry.

Enhancing rice productivity in sodic soils of Indo-gangetic plains through improved nursery management practices

The management practices for rice cultivation in salt-affected soils are obviously different than those in normal soils and for a short duration variety than those of a medium to long duration variety. Hence, experiment was planned and conducted at Central Soil Salinity Research Institute (CSSRI), Regional Research Station, Lucknow, Uttar Pradesh, India during 2011-12 to 2013-14 (kharif) hypothesizing that the combination of improved nursery management practices and high yielding salt tolerant variety would enhance productivity and profitability of rice in sodic soils. The results revealed that, improved nursery management practices like lower seed density, combined application of organic amendments and inorganic fertilizers in the seed bed (5 t/ha farmyard manures (FYM) followed by 100- 50-50 kg N-P2O5-K2O) and optimum age of seedlings enhanced seedling growth (shoot and root length, number of leaves, leaf area and dry matter) resulting higher grain yield and minimized production cost. Thirty-d-old seedling of salt tolerant variety CSR 36 raised using improved nursery management practices yielded 8.4% and 4.0% higher over 25 and 40d-old seedlings respectively. Salt-tolerant variety CSR 36 grown with improved nursery management options and followed by recommended dose of fertilizers (150-60-40-25 kg N-P2O5-K2O-ZnSO4/ha) in main field, could produce significantly higher grain yield than the yield level achieved using prevailing nursery management practices. This approach of combining cost effective nursery management and crop establishment options for salttolerant varieties can maximize the productivity and profitability of sodic lands in Indo-Gangetic alluvial plains.

Identification of artificial groundwater recharge sites in parts of Yamuna River basin India based on Remote Sensing and Geographical Information System

The Yamuna River is the part of vast Indo-Gangetic alluvial plain abides a huge scarcity of water in terms of both surface and groundwater resources. Artificial recharge is the most promising measure in the present scenario to improve the groundwater conditions of the area. In the present study artificial recharge sites were delineated using the important factors which plays a pivotal role in groundwater occurrence through Analytical Hierarchy Process (AHP) based modelling in Geographical Information System (GIS) environment. Datasets from different sources and Landsat-8 satellite images were used to assign the weightage for different parameters in accordance to their role in site selection for artificial recharging. The study shows that the sub-watershed-1 lies in the south-western upland of Agra district and sub-watershed-2 which is located in Firozabad district, occupies an area of 304 Km2 (42%) and 248 Km2 (35%) respectively, found under critical groundwater condition in terms of declining groundwater level. These sites are located mainly around the settlement areas of relatively higher elevation. Overall, 26% area (i.e., very low water level class in the study area) in the presented study exhibit poor groundwater conditions (i.e., 32–42 m bgl) and hence required an immediate treatment in terms of artificial technology in order to enrich the water stressed alluvial aquifers.

Drought Characterization Using Drought Indices and El Niño Effects

Droughts are extreme meteorological and hydrological events having severe impacts on the natural environment and socioeconomic conditions of the affected region. Drought characterization is vital in planning, design, and management of water resources systems. Drought indices such as standardized precipitation index (SPI) and standardized precipitation evapotranspiration index (SPEI) are generally used as a tool for monitoring changes in drought conditions. The variability of monsoon droughts over India is significantly influenced by the tropical sea surface temperature anomalies. A major portion of the drought variability is influenced by the El Nino–Southern Oscillation (ENSO). Drought characterization for Indo Gangetic alluvial plain demonstrates the efficacy of the present work. The values of SPI and SPEI are found in all the possible ranges representing mild, moderate, and severe drought events in the study area. Most drought events are observed in Raebareli District, as both SPI and SPEI indices showed 27 and 23 severe events. Also, correlation is found between observed drought periods, ENSO episodes, and drought indices.

Medical Geological assessment of fluoride contaminated groundwater in parts of Indo-Gangetic Alluvial plains

As drinking water is considered as a major pathway of exposure to fluoride in the human body, an endeavor has been made for the assessment of the non-carcinogenic health risk by using hazard quotient (HQ) of fluoride for males, females, and children separately in fluoride affected ground water areas of Indo-Gangetic Alluvial Plains. The study suggests that children groups are more prone to the non-carcinogenic risk of fluoride in the area as HQ for fluoride is more than unitary in 44% (Pre-monsoon) and 38% (Post-monsoon) samples respectively. Field survey conducted in fluoride-affected villagers of the study area portrays cases of mottling of teeth and bone deformities depending on the duration and dosage of fluoride consumption. Petrographic observations of host rocks coupled with molar ratios of chemical species studies exemplify that weathered material developed over the granite-gneiss, mica-schist, amphibolite, granitic intrusive and pegmatite veins due to weathering and extensive water-rock interaction resulting higher concentration of fluoride in groundwater. Likewise, the base exchange index (r1) and meteoric genesis index (r2) advocates that most of the samples belong to Na+-HCO3− type and meteoric origin respectively, and substantiate longer residence time of water along with solute acquisition processes are responsible for elevated fluoride in groundwater. It is, therefore, solar energy-driven electrolytic de-fluoridation technology ought to be provided on a priority basis to the affected inhabitants besides the implementation of rainwater harvesting schemes for mitigation/ dilution of elevated fluoride concentration.

Plant and Soil Responses to the Combined Application of Organic Amendments and Inorganic Fertilizers in Degraded Sodic Soils of Indo-Gangetic Plains

ABSTRACTSoil degradation due to salinization and sodication is the paramount threat in Indo-Gangetic plains. The studies on reclamation and management of such soils can provide a pragmatic solution for improving fertility and productivity of these soils. Lack of organic matter and poor availability of nutrients are the major factors for low productivity of sodic soils. Rice-wheat is a major cropping system in Indo-Gangetic alluvial plain region even in reclaimed sodic soils and farmers used inorganic fertilizers only to get higher yields. In this study, we used different organic sources of amendments in conjunction with different nitrogen (N) doses supplied through inorganic fertilizers to investigate the combined effect of organic and inorganic amendments on soil fertility and the productivity of rice- wheat system in sodic soils. Salt tolerant varieties of rice and wheat were grown in sodic soil (pH: 9.30, EC: 1.12 dSm−1 and exchangeable sodium percentage, ESP: 52) during 2014–15 to 2016–17 in a field experiment with 13 treatment combinations of organic and inorganic amendments (T1- (control) 100% of recommended dose of N (RDN), T2-municipal solid waste compost (MSWC) @10 t ha−1 + 50%RDN, T3- MSWC @10 t ha−1 + 75% RDN,T4- MSWC @10 t ha−1 + 100%RDN, T5-Vermicompost (VC) @10 t ha−1 + 50% RDN, T6- VC @10 t ha−1 + 75% RDN, T7-VC@10 t ha−1 + 100% RDN, T8- Farm yard manure (FYM) @ 10 t ha−1 + 50% RDN,T9- FYM@10 t ha−1 + 75%RDN, T10- FYM@10 t ha−1 + 100% RDN, T11-Pressmud (PM) @10 t ha−1 + 50% RDN, T12-PM@10 t ha−1 + 75%RDN, and T13- PM @ 10 t ha−1 + 100% RDN). Use of organic amendments supplemented with reduced dose of N through inorganic fertilizer has significantly improved soil bio-physical and chemical properties. Application of VC@10 t ha−1 + 100% RDN (T7) decreased soil bulk density, pH, EC, ESP and Na content to 2.0, 4.2, 26.5, 42.8, and 56.6% respectively and increased soil organic carbon by 34.6% over control (T1). Soil fertility in terms of available N, P, K, Ca, and Mg increased by 20.5, 33.0, 36.4, and 44%, respectively, over control (T1). Soil microbial biomass carbon, nitrogen, and phosphorus also improved significantly due to combined use of organic amendments and inorganic fertilizers over the only use of inorganic fertilizers. Decreasing in soil sodicity and increasing soil fertility showed significant increase (P < 0.05) in crop growth, growth indices, and grain yields of rice and wheat. The study revealed that combined use of VC or MSW compost @10 t ha−1 in conjunction with 75% RDN through inorganic fertilizers in sodic soils proved sustainable technology for restoration of degraded sodic soils and improving crop productivity.

Comparative Evaluation of Active Tectonics in Parts of the Frontal Region of NW Himalaya, India by Geomorphic Analysis and Geophysical Investigation

The Himalayan Frontal Thrust (HFT) is the southern-most boundary of Himalayan mountain belt. It represents a zone of active deformation between the sub-Himalaya and Indo-Gangetic alluvial plain. Morphometric analysis of five sixth order drainage basins along the HFT has been carried out for evaluating relative tectonic activity of the region. Based on the combination of various geomorphic indices such as drainage basin spatial asymmetry, drainage gradient, drainage cross profile and mountain front sinuosity indices, the relative tectonic activity in and around the test site drainage basins was evaluated. Where all the indices are not in agreement, the relative importance of the geomorphic indices was considered to evaluate relative tectonic activity which was then compared with the abundance of drainage anomalies and previously reported active tectonic features (including active faults and fractures). Finally, the results were corroborated with the spatial frequency distribution pattern of previous seismicity (>2.5 Mw). Geophysical investigation by multi-frequency, bi-static ground penetrating radar (GPR), conducted at selective locations in the piedmont-alluvial region of Solani and Markanda drainage basins, supports active deformation of sub-surface sediment layers. Well-defined offset and warping of near-surface sediment layers indicating the presence of active fault and deformation of sediment layers were observed in 40 MHz and 100 MHz radargrams near Biharigarh and Mujahidpur villages in Solani drainage basin (Uttarakhand and U.P.) and near Toka village in Markanda drainage basin (H.P.).

Geochemical signatures and isotopic systematics constraining dynamics of fluoride contamination in groundwater across Jamui district, Indo-Gangetic alluvial plains, India

A data set of 76 water samples are obtained from surface and sub-surface water bodies to investigate chemical parameters and stable isotopic signatures in order to drive factors leading to fluoride (F−) contamination in groundwater of parts of Jamui district, India. Hydrochemical facies reveals that F− concentration is lower in Ca2+-HCO3- facies representative of recharge area, while discharge area has a tendency towards Na+-HCO3- facies with elevated F− concentration. The ionic ratios Na+/Ca2+>1, Na+/Cl−>1, (Ca2++Mg2+)/HCO3−<1, Na++K+ = 0.5TZ+ and Ca2++Mg2+ = TZ+ witness silicate weathering by water-rock interaction coupled with ion exchange and prolonged residence time, are the principle factors for fluoride contamination (3.6 mg/L to 5.8 mg/L) in 67% of deeper bore wells. Geochemical modelling testifies excess of alkalinity due to the dominance of bicarbonate ion leading to calcite precipitation and dissolution of fluoride in solution contributing to fluoride contamination. The chemometric analysis reveals that the water chemistry of the study area is controlled by both anthropogenic and natural sources, and enrichment of fluoride in groundwater is possibly from geogenic source (fractured granite gneiss). The stable isotope plot shows that most of the samples fall along local meteoric water line indicating that the groundwater is originated from local precipitation with a possibility of evaporative enrichment. Groundwater enriched in δ18O is positively correlated with F− suggesting evaporation and longer residence time of water. Spatially elevated F− prevails in the eastern bank of Kiul River and along the groundwater flow direction, which is attributed to control of dynamics of hydrogeological conditions.

Modification of root properties with phosphate solubilizing bacteria and arbuscular mycorrhiza to reduce rock phosphate application in soybean-wheat cropping system

Inoculation of phosphate solubilizing bacteria (PSB) and phosphorus mobilizing arbuscular mycorrhiza (AM) with low quality rock phosphate (RP) can be an alternative source to one of the costliest phosphatic fertilizers in India, i.e. single superphosphate, by enhancing phosphorus influx and modification of root properties. Co-inoculation of PSB and AM may play a pivotal role to reduce phosphorus application through RP. Root properties and grain yield of irrigated soybean-wheat cropping system were evaluated with two levels of RP {100 and 50% recommended P (1.0 RP and 0.5 RP)} and different combinations of PSB and AM with 0.5 RP (0.5 RP+PSB, 0.5 RP+AM and 0.5 RP+PSB+AM) versus 100% recommended P application through soluble single superphosphate (1.0 SP) in the Indo-Gangetic plains. The P influx under 0.5 RP+PSB+AM and 1.0 SP were statistically at par with each other and the former treatment provided 0.6 and 3.2% higher value than the later in soybean and wheat, respectively. The root surface area density (RSAD) of soybean and wheat under 0.5 RP+PSB+AM (13.71 and 6.16m2m−3, respectively) and 1.0 SP (13.70 and 6.37m2m−3, respectively) were non-significant and almost equal with each other. The values of root cation exchange capacity and other root properties under 0.5 RP+PSB+AM and 1.0 SP were also non-significant. The improved root properties under 0.5 RP+PSB+AM provided statistically at par grain yield with 1.0 SP for both soybean and wheat crops. The yield under 0.5 RP+PSB+AM of soybean crop was 3.4% higher than 1.0 SP. The net returns US$−1 invested was significantly higher under 0.5 RP+PSB+AM compared to 1.0 SP for both soybean and wheat crops. Co-inoculation of PSB and AM with 50% of recommended P through RP could be recommended for better root properties and profitable grain yield of soybean-wheat cropping system in the Indo-Gangetic alluvial plains.

Groundwater Assessment in a Canal Command Area for Sustainable Irrigation in a Part of the Indo-Gangetic Alluvial Plain

The growing dependence of irrigation on groundwater and its excessive use for other purposes has an adverse impact on the resource domain. This has resulted in unsustainable over-extraction and subsequent lowering of the groundwater table. The present study shows that groundwater levels can be kept near stable even with more extraction for increased cropping intensity of up to 222% by opting conjunctive use, as against the present intensity of 163.1%. In addition, the groundwater sustainable area increased from 65% to 92% and the groundwater depletion area decreased from 30% to 7%. The waterlogged area also reduced from 5% to 1% in a period of three years, thereby increasing gross margins. Groundwater system simulation shows that groundwater level will remain sustainable even after 10 years at 222% cropping intensity by adopting conjunctive use of groundwater with canal water.

Groundwater quality analysis of quaternary aquifers in Jhajjar District, Haryana, India: Focus on groundwater fluoride and health implications

Several types of health problems in Jhajjar district of Haryana state are prevailing owing to groundwater quality problems such as high concentration of fluoride, chloride, salinity, TDS, etc. The objective of this work was to assess the overall groundwater quality of the district based on Water Quality Index (WQI), and find out the factors leading to continuous deterioration in groundwater quality. The study demonstrates that groundwater quality of Jhajjar district is totally unsuitable for drinking purposes and is directly or indirectly influenced by geogenic factors. About 60–70% of the samples analysed show high fluoride content. Other parameters such as hardness, electrical conductivity, Total Dissolved Solids (TDS), and Chloride are also above the permissible limits. Hydrogeologically the study area belongs to Indo-Gangetic alluvial plains, which are dominated by clay-silt, clay and grey micaceous sand formations. Clay rich formations are rich in fluorine and other salts and their weathering is most probably causing the continuous escalation in the fluoride and salinity concentration in groundwater. Several in-situ and ex-situ measures have been suggested for remediation and to prevent further escalation of water quality problems that are needed imperatively for the sustainable development of water resources.

Delineation and characterization of salt-affected soils in Varanasi district of Uttar Pradesh

Salt affected soils are primarily widespread over Uttar Pradesh especially in irrigated areas of the vast middle Indo-Gangetic alluvial plain of shallow water table depth and hot and dry moisture regions. Soil salinity and alkalinity are two of the main constraints present in these irrigated agricultural lands and the problem of salinity and alkalinity increases every year as a result of secondary salinisation and as a result of which the fertile productive land is gradually becoming unproductive. Varanasi district of Uttar Pradesh have been identified to the intensive area study site for this research work. Study area is a part of the vast alluvial expanse popularly known as Indo Gangetic plains. The study area lies in hot semi arid eco region 4.3, between geo-coordinates 25o 18’’ N and 83o 03’’ E covering 1, 535 sq km area a part of the vast Indo-Gangetic alluvial plain having sandy soil, which also coincides with low rainfall. The result indicated that the soil reaction is moderately to strongly alkaline. The organic carbon was reported to vary from 0.11 to 0.88%. Under saturation extract analysis, sodium ion was observed as dominant cation, followed by Calcium, Magnesium and Potassium and alkali soil having high pH are deficient in both soluble and exchangeable calcium.

Exploring Cost effective Herbicide based Weed Management options for Sunflower in NW India

Field experiment was conducted during spring 2009 and 2010 in the Indo-Gangetic alluvial plains to evaluate the efficacy of different pre-emergence herbicides alone or in combination with hand weeding for effective weed management in sunflower. Season long competitional stress with weeds reduced the mean seed yield of sunflower by 43.5% in comparison to conventional practice of two hand weedings (3 and 6 weeks after sowing). Herbicide based weed management increased the sunflower yield by 52.6–71.6% in comparison to weedy check. Irrespective of herbicide dose, yield improvement to the tune of 5.5–12.5% was observed with weed management through either of the pre-emergence herbicide (oxydiargyl/alachlor) when compared with recommended herbicide application of pendimethalin @ 0.75 kg/ha. Integrated approach involving herbicides with one hand weeding 4 WAS resulted in better seed yields (3.1–4.4% superiority) but the profit margin gets reduced due to higher wages of human labour incurred. Alone application of alachlor 1.5 kg/ha resulted in highest monetary benefits with highest B: C ratio of 3.49 followed by oxydiargyl 0.1 kg/ha (3.35) which was as good as two hand weedings done 3 and 6 WAS. This study identifies pre-emergence application of alachlor 1.5 kg/ha or oxydiargyl 0.1 kg/ha as economically viable weed management strategy in sunflower considering the present situation of labour scarcity, quality of weed control, productivity and profitability concerns.

Development of hyperspectral model for rapid monitoring of soil organic carbon under precision farming in the Indo-Gangetic Plains of Punjab, India

Degrading soil quality at an alarming rate as a result of high input agriculture under continuous rice-wheat cropping system in the Indo-Gangetic alluvial Plains of Punjab (India), a major food growing region of south-east Asia, has ushered the need of precision farming for which rapid site specific monitoring of soil organic carbon (an indicator of soil quality) is needed. In this study, visible-near infrared reflectance spectroscopy was evaluated for rapid prediction of soil organic carbon (SOC) contents in soils of the Indo-Gangetic alluvial Plains of Punjab, India. A total of 800 surface soil samples (480 for calibration and 320 for validation) from farmers’ field representing the districts of Ludhiana, Moga, Gurdaspur and Bhatinda in Punjab State, India were collected, ensuring sufficient variation in SOC content. Reflectance spectra were obtained from air-dried samples (<2 mm size) under controlled laboratory conditions using a hyperspectral ASD FieldSpecPro spectroradiometer. Part of the same samples was used for SOC determination by Walkley and Black titration method. The SOC value in the study area varies from 4.0 to 18.1 g kg−1 (mean 7.9 g kg−1 and standard deviation of 2.2 g kg−1) among the soil samples. Partial least squares regression technique was employed to examine the relationships between SOC and the reflectance spectra; and to identify the wavelengths sensitive to SOC variation. Among 15 spectral transformations used for calibration, SGF-2-3 transformation (transformation to 1st derivative with second order polynomial smoothing with 3 points using Savitzky-Golay filter) was the best for SOC modeling in the IGP soils as it showed highest validation r2 (0.81) and RPD (2.30) and the lowest RMSEP (0.116) with 6 PLS factors. The most important wavelengths for SOC prediction were 460, 470 and 550 nm in the visible and 1400, 1420, 1920, 2040, 2210, 2270, 2320 and 2380 nm in the near-infrared region. At this juncture of much awaited second green revolution envisaged to be based on sustainability and precision agriculture in one hand and the increased availability of high resolution hyperspectral satellite data on the other hand; our findings regarding rapid evaluation of SOC through hyperspectral model are encouraging as it might assist in real time evaluation of pre and post-scenarios of soil quality and sustainability under precision farming system.

Chemical fractions and bioavailability of nickel in alluvial soils

The present study was undertaken to sequentially fractionate nickel (Ni) in soils of divergent physicochemical char acteristics and evaluate the contribution of different fractions towards plant uptake. For this, fifteen bulk surface (0–15 cm) soil samples were collected from the cultivated fields of northwestern Indo-Gangetic alluvial plains. A pot experiment was conducted with these soils to assess the contribution of soil Ni fractions to plant uptake using soybean as test crop. Results showed that residual Ni was the most dominant fraction in soil constituting 3.19–63.6% of total Ni. The water soluble plus exchangeable Ni accounted for only 0.70–4.04% of total soil Ni. Organically bound Ni varied from 1.60–6.85% of total Ni; these values are relatively lower as compared to those reported for temperate soils. Correlation studies showed that the free iron oxide (Fe 2 O 3 ) and soil organic carbon correlated with various fractions of Ni in soil. Water soluble plus exchangeable and organically bound are the dominant fractions which contributed positively and manganese oxide (MnO 2 ) bound and residual fractions contributed negatively towards the phytoavailability of Ni in soil.