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2011 - 20122
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Subject: Soil Science × Start date: 2010 × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    Studies on Organophophorus Pesticide Residues in Paddy Ecosystem and Evaluation of Zn and Fe Content in Paddy Grains and Soils of Gangavati Taluka in North Karnataka
    (UAS Dharwad, 2012) Selvaraj S.; N.S. Hebsur
    The present studies were carried out to evaluate the organophosphorus pesticide residues in soil, water and plant samples of paddy eco-system. The soil, water and paddy grain samples were collected from five farmers' fields from each village in a cluster of twelve villages and analyzed for organophosphorus residues viz., chlorpyriphos, quinalphos, monocrotophos and dichlorvos. The soils were also analysed for different fractions of zinc and iron and their contents in paddy grains. The soils were neutral to strongly alkaline in reaction, non-saline, low to high in organic carbon status with enough calcium carbonate. The analytical results indicated that chlorpyriphos was the only chemical detected in grains. In soils, chlorpyriphos was below detection limit and chemicals such as quinalphos, monocrotophos and dichlorvos were not detected. In water samples also, the concentration of these chemicals were below detection limit. The fractionation studies indicated that the order of zinc fractions in soils were: Water soluble + exchangeable Zn < Amorphous bound Zn < Manganese oxide bound Zn < Organically bound Zn < Sesquioxide bound Zn < Residual Zn < Total Zn. And dominant iron fractions were: Water soluble Fe < Exchangeable Fe < Residual Fe < Crystalline bound Fe < Amorphous iron oxide bound Fe < Total Fe. Zinc content in paddy grains varied from 12.17 ppm in Basapatna sample to 37.43 ppm in Karatagi sample with mean value of 21.39 ppm. Iron content ranged from 86.41 ppm in Sangapura sample to 213.31 ppm in Karatagi sample with mean value of 115.49 ppm. In conclusion, chlorpyriphos chemical residue was only in organophosphorus pesticide quantified in grain samples (0.01 ppm MRL) in paddy ecosystem of Gangavati taluka.
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    ThesisItemOpen Access
    Potassium Dynamics and Response to Applied Potassium in Paddy-Paddy and Sunflower Bengalgram Cropping System Under Vertisols in TBP Command Area
    (UAS Dharwad, 2011) K. Narayana Rao; N.A. Yeledahalli
    soil samples of dominant cropping system of TBP command area for physico-chemical and mineralogical properties of the soils, quality and distribution of different forms of potassium, potassium reserves in textural fractions and its fixation. Field experiments were also conducted to study the response of applied potassium in paddy-paddy and sunflower-bengalgram sequence with farmer’s participation. The soils are low in water soluble K, medium to high in exchangeable K, which ranged from 78 to 238 mg kg-1 in surface and from 103 to 265 mg kg-1 in subsurface layers. The non exchangeable K varied between 342 to 602 mg kg-1 and 374 to 631 mg kg-1 in surface and subsurface layers, respectively. The amount of lattice K content in surface horizons varied from 2.90 g kg-1 to 9.88 g kg-1 and 3.25 to 11.0 g kg-1 in subsurface layers of both the cropping sequence. The total content ranged between 3.38 to 10.56 and 3.89 to 11.0 g kg-1 in surface and subsurface horizons, respectively. The different forms of K were positively correlated with each other in soils of paddy-paddy sequence indicating its dynamic equilibrium compared to soils of sunflowerbengalgram sequence where no dynamic equilibrium exists between different forms of K. The soils of paddy-paddy sequence had higher K fixation compared to soils of sunflower-bengalgram sequence. The mineralogy of soils revealed the dominance of smectite in the clay fraction in both cropping sequence. The paddy, sunflower and bengalgram crops have responded to potassium application in both kharif and rabi seasons in a cropping sequence involving paddy-paddy and sunflower-bengalgram. The potassium balance sheet was negative in soils of both the cropping sequences.