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  • Author or Editor: A. Renukadevi x
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Fifteen major soil series at the rate of three for each soil group, namely red non-calcareous, red calcareous, black calcareous, brown calcareous and alluvial soils, were studied for the vertical distribution of different forms of potassium. The total potassium content varied from 515-5513 ppm and generally increased with depth. It was positively related with clay, silt, CaCO3, CEC and total Ca. Non-exchangeable K ranged from 340-1326 ppm and did not exhibit any uniformity in its distribution in soil profiles. The exchangeable K varied from 45-684 ppm and was positively related to organic carbon. NH4OAc-K ranged from 15-298 ppm. Soil properties like clay, silt, CaCO3 and organic matter were positively related to available K. Water-soluble K varied from 2-33 ppm and was found to decrease with the depth of the soil profile. It was positively correlated with organic carbon and negatively related to clay plus silt. Studies on the relationship between the above forms of potassium indicate that, except for total K, the other forms were closely related, indicating the possibility of predicting one from the other.

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Field experiments were conducted at the Agricultural Research Station, Bhavanisagar, Tamil Nadu, India during 1999 to 2000 in Inceptisols to evaluate boron fertilizers (borax, boric acid, Agribor) and to assess the effect of the mode and level of B application on the total B uptake and yield of sunflower and green gram. The experimental field was found to be deficient in available B (0.35 mg kg-1). Sunflower was raised as the main crop. Different B levels (0.5, 1.0, 1.5and 2.0 kg B ha-1)as soil application and two levels of foliar spray (0.2% and 0.3%) were compared with the control. The treatments were superimposed on the recommended dose of NPK. After harvestingthe main crop of sunflower, the residual effect of B was studied by raising green gram on the same field. The results revealed that the application of all the levels of B resulted in a significant increase in the B uptake and yield of sunflower as compared to the control. The highest yield was recorded for the soil application of B at a rate of 2.0 kg ha-1. The yield increase of sunflower was 3.6 to 15.8% and 7.2 to 18.9% over the control for seed and stalk, respectively. The green gram grain yield increased by 4.2 to 13.5% after the application of 1.0 and 2.0 kg B ha-1 to the main crop. No residual effect was observed for the lowest level of B application (0.5 kg ha-1). Agribor is equally as effective as borax in influencing the B nutrition of both the crops.

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Sunflower necrosis virus (SFNV) has a wide host range, which includes many cultivated crops and weed hosts. Fifteen plant species belonging to Fabaceae, 3 plant species belonging to Malvaceae, 6 plant species belonging to Cucurbitaceae, 3 plant species belonging to Solanaceae and one plant species each belonging to Caricaceae and Moringaceae were found to be additional hosts for SFNV. Besides, weeds such as Trianthema portulacastrum, Priva leptostachya, Digeria arvensis, Clitoria ternatea, Solanum nigrum, Vernonia cineraria, Trichodesma indicum and many other species were found to act as hosts for SFNV.

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