ABSTRACT
The soil samples were collected from the soils of Long Term Fertilizer Experiments that have been fertilized for the last 25 years from a) control plot (receiving no fertilizer/FYM); b) plot receiving 100% NPK fertilizer application and c) Plot receiving 100% N in the form of FYM, to study the changes in nature and amount of organic matter and these were compared with a similar adjacent soil under natural vegetation. The soil samples were collected from 0-15 cm (surface) and 15-30 cm (sub surface) layers. The humic substances were fractionated by Tyurins method. The total N and available N content was determined and C/N ratio was calculated. The humic acid was isolated, purified and analyzed for oxygen containing functional groups and spectral properties. It was observed that the soil under natural vegetation had a higher total N while the soil under continuous cultivation had higher available N. The C/N ratio of soil under natural vegetation was high compared to the soil under continuous cultivation. These values were high in surface layers compare to sub surface layers. The oxygen containing functional groups in Humic acid (HA) were high in soil under natural vegetation compared to the soil under continuous cultivation. The total acidity and COOH content of surface layers was high compared to sub surface layers in soils under both situations. Phenolic OH groups of subsurface layer was high in soil under natural vegetation and continuous cultivation indicating that this group in sub surface layers and high potential for interaction with clays and metal ions. The higher contents of total acidity and –COOH groups in soil under natural vegetation could be attributed to the difference in chemical composition and molecular weight of humic substances. The E4/E6 ratios of HA’S were less than 5.0 indicating high degree of condensation of aromatic humic acid. The potentiometric titrations of humic acids with standard 0.1 N NaOH indicated a gradual increase in pH with the addition of base thus indicating a high buffering capacity of humic acid. The potentiometric titration curves were sigmoid in nature indicating an apparent mono basic character and had a single break suggesting weak acidic character of humic acids. The conduct metric titrations of humic acids showed a slow increase in the initial stage followed by a steep increase at later stages. The apparent pKa values calculated from potentiometric titration data using Henderson-Hassebalch equation varied from 5.24 to 5.68.
ABSTRACT
Adsorption of atrazine was studied on two Vertisols and two Alfisols varying in their physicochemical properties. Soils were equilibrated with various concentrations of atrazine using batch techniques. Adsorption affinity for atrazine was approximated by Freundlich constant (Kf), which is a measure of the strength or degree of adsorption. Kd values were calculated for atrazine despite some non-linearity in adsorption on both Vertisols and Alfisols. The Kd values are greater for Vertisols than Alfisols and increased with organic carbon content. Correlations were worked out between extent of adsorption and soil properties and were positively correlated with organic carbon (r = 0.688), clay content ( r = 0.712) and clay + organic carbon (r = 0.708). KOC values were calculated taking into account the organic carbon content for both Vertisols and Alfisols.
ABSTRACT
An experiment was conducted with four dates of sowing (Second fortnight of May, First fortnight of June, Second fortnight of June and First fortnight of July) and four Varieties (TMV-2, JL-24, Narayani and Abhaya). There was wide variation in the weather conditions that prevailed over the cropping periods between the two years of experimentation. During the first year (2006) a continuous dryspell of 51 days prevailed which coincided with different growth stages of groundnut under different dates of sowing. This dry spell has not favoured the growth and development of crop, instead, it has increased the crop duration of different varieties of groundnut studied under the present investigation. The crop duration was 139-146 days in early sown crop to 110-125 days in normal sown crop compared to normal duration of 105 to 120 days. However, the second year (2007) is normal with better temporal distribution of rains and the crop duration ranged from 104-120 days in early sown crop to 108-121 days under normal sown crop. The length of growth period in 2006 is due to receipt of continuous rains after dry spell of 51 days from seed development phase to physiological maturity. In 2007,the crop which received heavy rains (22 June sown crop ) from 90 DAS to harvest was adversely affected resulting poor filling and low yields. The results revealed that Sowing during July first fortnight was found to be optimum time for groundnut during drought year, while during normal year advancing the sowing date by one month may also favour good crop provided there were good rains. The performance of Abhaya cultivar was better than the Narayani, TMV-2 and JL-24 under different kinds of environments like extreme moisture stress, stress free or even under moderate stress conditions. However, in normal year TMV-2 and JL-24 performance was also good compared to drought year.