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20202
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Subject: Soil Sciences × End date: 2020 × Start date: 2020 × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    Effect of different cropping systems on manganese availability and transformations in soils
    (Punjab Agricultural University, Ludhiana-, 2020) Mittal, Shreyansh; Saini, Sat Pal
    The present research study was conducted to investigate the transformation and depth-wise distribution of manganese (Mn) in soils under different cropping systems viz. rice-wheat (RWCS), maize-wheat (MWCS) and cotton-wheat (CWCS). A total of 150 surface (0-15 cm, 50 samples per cropping system) and 18 profile (0-15, 15-30, 30-60, 60-90 cm, 6 per cropping system) samples were collected from three different districts viz. Ludhiana (for RWCS), Ropar (for MWCS) and Mansa (for CWCS) in Punjab (India). In addition, 150 plant leaf (flag leaf of rice, fully extended leaf of maize and a fully matured leaf of cotton (50 each for crop) and 150 wheat leaf samples were collected from each soil sampling location. Soils of MWCS had significantly higher mean DTPA-Mn and other fractions of variable solubility, compared with the soils of other two investigated cropping systems. On the other hand, DTPA-Mn and the concentration of different chemical fractions in soils under RWCS were significantly lower. The soils under CWCS had significantly (p<0.05) higher soil pH, E.C. and CaCO3 as compared to other cropping systems. The DTPA-Mn was lowest in the surface (0-15 cm) soil layer, and increased significantly with depth in RWCS, in contrast to a decrease in soils under other two cropping systems. The different fractions of variable solubility viz. WSEX-Mn, SpAD-Mn, OX-Mn, AFeOx-Mn, CFeOX-Mn, OM-Mn and residual-Mn showed significant linear relationship (p<0.05) with soil organic C (SOC) and soils’ fine fraction (silt and clay). The Res-Mn fraction comprised the largest proportion (67-70%) while the WSEX-Mn + SpAD-Mn fraction was the smallest Mn fraction in soils under different cropping systems. Data pooled for different locations revealed that leaf Mn concentration in wheat leaves was highest in crop sown in MWCS, followed by CWCS and the lowest in RWCS. Leaf Mn concentration showed a significant relationship with DTPA-Mn and different Mn fractions. Foliar application of Mn significantly influenced the wheat grain yield, Mn uptake and Mn use efficiency in wheat grown in different cropping systems. A significant response of foliar application of Mn at different growth stages (vegetative as well as ear initiation stage) was observed in all the three cropping systems. A quadratic response of relative grain yield to DTPA-Mn after harvest of wheat revealed that 90% of the maximum yield was achieved with foliar Mn application at 2.98, 3.69 and 3.82 mg DTPA-Mn kg-1 soil for RWCS, MWCS and CWCS, respectively. Soil and foliar application of MnSO4 (25 and 50 ppm) either alone or conjointly with FYM and PM (0.5%) in a pot experiment significantly increased the growth parameters and productivity of wheat cultivars (PBW 725 and PDW 314) and Mn fractions in soil. Soil application of MnSO4 either alone or conjointly with organic manures significantly increased the concentration of DTPA-Mn, totalMn, WSEX-Mn, SpAd-Mn, Ox-Mn, AFeOX-Mn and CFeOX-Mn, OM-Mn and Res-Mn. The relative preponderance of occurrence of different Mn fractions in soil followed an order: OM-Mn
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    Geochemical assessment and remediation of arsenic in south-western Punjab
    (Punjab Agricultural University, Ludhiana, 2020) Jyoti; Kuldip Singh
    Geochemistry and assessment of arsenic (As) in groundwater and soil is an important factor for effective management of the groundwater resource. One hundred twenty groundwater samples, 60 soil samples and 120 paddy straw samples were collected from southern-western districts of Punjab, India: Mansa, Muktsar and Bathinda, during pre- and post-monsoon seasons. Significant and positive correlations were observed between As and RSC content of groundwater in premonsoon season. The paddy straw As content was positively and significantly correlated with As, RSC, redox of groundwater, total and available As content in soil. The available As was significantly and positively correlated with total soil As content. A laboratory investigation was carried out to examine the mechanism of As mobilization under flooded conditions (24 and 240 h) in 10 alluvial soils. Total dissolved As increased from a range of 3.14–16.14 µg l-1 (mean 8.95 µg l-1) to a range of 34.2–1768 µg l-1 (mean 871.5 µg l-1) with the increase in flooding period from 24 to 240 h. The amount of As mobilization varied depending upon redox potential (pe) created by flooding conditions. After 24 h of flooded conditions, pe of soil-water suspension ranged from 2.11 to -0.64 (mean -1.25), whereas, it decreased in the range of -5.23 to -2.55 (mean -3.52) after 240 h of flooding. A loamy sand and a clay soil were used to study adsorption behaviour of arsenate (AsV) by equilibrating soil with range of added concentration (50-2500 mg AsV kg-1 soil) in presence of background electrolyte 0.01 M NaNO3, under two temperatures (278 0K and 308 0 K) and two solution pH (5 and 8.5). Arsenate adsorption was found to increase with increase in temperature as well as with decrease in solution pH, however, amount of AsV adsorbed was relatively higher in clay soil as compared to loamy sand soil. Arsenate adsorption was highest at solution pH 5, 308 0K and lowest in solution pH 8.5, 278 0K, irrespective of soil. Arsenate adsorption data were well described by Langmuir and Freundlich isotherms. To study effect of added anions on AsV adsorption, at each added AsV concentration, 1000 mg anion kg-1 soil was also added. The addition of anions reduced the amount of AsV addition at both temperatures and pH in two soils in the order: phosphate > silicate > sulphate > bicarbonate. For removal of AsV from groundwater, effectiveness of iron-coated sand and iron-coated strips was investigated. Ironcoated strips were found to have relatively higher capacity to remove AsV as compared to ironcoated sand. To study kinetics of AsV adsorption by loamy sand soil, clay soil, iron-coated sand and iron-coated strips, the data were fitted to four kinetic models: Pseudo-first order, pseudosecond order, elovich and intra-particle diffusion models. Among these four kinetic models pseudo-second order gave best fit with high R2 value as well as lower error.