Effects of crop rotation on enhanced occurrence of arbuscular mycorrhizal fungi and soil carbon stocks of lowland paddy
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ARTICLE
Effects of crop rotation on enhanced occurrence of arbuscular mycorrhizal fungi and soil carbon stocks of lowland paddy fields in seasonaly dry tropics T. M. Paranavithana1 · Svini Marasinghe2 · G. A. D. Perera2 · R. R. Ratnayake1 Received: 3 December 2019 / Revised: 14 August 2020 / Accepted: 13 November 2020 © The International Society of Paddy and Water Environment Engineering 2020
Abstract The impacts of crop rotation systems on the arbuscular mycorrhizal fungal (AMF) spore density, mycorrhizal colonization of rice roots, soil C fractions and C stocks in seasonally dry climatic zone of Sri Lanka were examined in Rice–Soybean (RS) and Rice–Onion (RO) crop rotation systems during the subsequent rice cultivation season and, compared these with a rice monoculture, i.e. Rice–Rice (RR). The study also examined the correlations between AMF occurrence and soil carbon stocks. Results revealed that RS crop rotation system significantly enhances the occurrence of AMF spores in soil with a higher fraction of large sized spores, the total organic C (TOC), microbial biomass C (MBC), water soluble C (WSC), labile C and a high AMF colonization in rice roots in the subsequent rice cultivation season. The diversity of AMF morphospecies were also the highest in RS. Reduction in AMF density in the soil in RR crop rotation system may be due to prolonged anaerobic conditions prevailed. The growth of onion has drastically reduced the AMF colonization in rice and soil C contents. Soil carbon stocks showed positive correlations with % root colonization and AMF spore number in soil. Thus, the study confirmed that C stocks in paddy soils can be improved by intercropping with AMF supporting plants like soya bean. This is the first report that shows positive correlations of AMF sporulation and % root colonization in lowland rice with soil carbon stocks. Keywords Carbon sequestration · Mycorrhiza · Onion · Rice · Soybean · Sri lanka
Introduction Being the major staple food of more than half of the world population (FAO 2004; FAO 2003), rice has become an economically important crop worldwide. Rice, (Genus Oryza) which belongs to the family Poaceae, is widely grown throughout the tropics, especially in Asian countries including Vietnam, Laos, Bangladesh, India, Sri Lanka, Myanmar, Cambodia as well as in West Africa and in South and Central America (Muthayya et al. 2012). The versatile distribution of this crop is due to its ability to perform well in diverse environmental conditions. It is of substantial importance for food security and socioeconomic development, especially in * R. R. Ratnayake [email protected] 1
National Institute of Fundamental Studies, Hantana Road, Kandy, Sri Lanka
Department of Botany, Faculty of Science, University of Peradeniya, Peradeniya, Sri Lanka
2
low-income-generating countries with food deficits (FAO 2004; FAO 2003). However, in the recent past, stagnation of rice yields has been reported from several Asian countries (FAO 2003). Depletion of nutrients due to prolonged cultivation and h
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