Department of Soil Science and Agricultural Chemistry University of Agricultural Sciences, Bangalore – 560 065, Karnataka, India.
*Correspondence Author: Global Theme on Agro ecosystems, The International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru-502 324, Andhra Pradesh, India. Phone (O): 080-23330153 (Ext.-293), FAX (O): 080-3330277, Mobile: 9449779336, E-mail: rsraobk@rediffmail.com
The influence of decomposition products of paddy straw, Neem litter (Azadirata indica A. Juss.) and gliricidia litter (Glyricidia sepium Jacq.) after soil incorporation and flooding was determined on the growth response of rice (Oryza sativa L.). Two soils of contrasting physico-chemical properties were enriched with the carbon sources at zero, 2.5 per cent and 5 per cent carbon levels to study the influence of decomposition products on rice, accumulation of allelochemicals, histological response of rice root and to relate the root growth retardation with the levels of exogenous application of allelochemical mixture. Root and shoot growth inhibition response to the allelochemical accumulation in soil varied with organic carbon (C)) load given and source of C. Tree litters were more toxic than paddy straw. Histological study of roots revealed that larger doses of organic carbon sources could induce internal abnormalities, degeneration of epiblema and epidermis which was attributed to phenolic acids like p-hydroxy benzoic acid, p-coumaric acid, syringic acid and vanillic acid. Phenolic acid mixture prepared and spiked to two different soils confirmed the toxic role of phenolic acids on rice, based on the A50 values obtained and the quantity of phenolic acids accumulated in contact with rice roots when paddy straw, neem litter and gliricidia litters were soil incorporated.
Allelochemicals, exogenous application, flooding, histochemistry, rice
