Sandy Soil Amended with Clay Soil: Effect of Clay Soil Properties on Soil Respiration, Microbial Biomass, and Water Extr
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Sandy Soil Amended with Clay Soil: Effect of Clay Soil Properties on Soil Respiration, Microbial Biomass, and Water Extractable Organic C Muhammad Riaz 1,2 & Petra Marschner 2 Received: 29 May 2020 / Accepted: 29 July 2020 # Sociedad Chilena de la Ciencia del Suelo 2020
Abstract The low organic C (OC) sequestration and low water and nutrient holding capacities of sandy soils can be improved by amendment with clay soils. However, the effect of clay soils may depend on clay soil properties, including cation exchange capacity (CEC) and clay and OC contents. Two experiments were carried out. In the first experiment, sandy soil was mixed with two high clay content soils (Sodosol and Vertosol) at 10% and 40% (w/w). The soil was left unamended or amended with wheat straw, to assess if the effect of clay soil addition was influenced by OC addition. In the second experiment, sandy soil was mixed with two low-clay content soils which differed in CEC without wheat straw amendment. In experiment 1, compared with sandy soil alone, amendment with Sodosol (low OC) reduced cumulative respiration more strongly than addition of Vertosol. Without wheat straw addition, both clay soils increased microbial biomass C (MBC), whereas with wheat straw, they reduced microbial biomass C (MBC) compared with sandy soil alone. Sodosol amendment reduced water-extractable OC (WEOC) without wheat straw but increased it with wheat straw. In experiment 2, only the high CEC clay soil reduced cumulative respiration, MBC and WEOC compared with sandy soil alone. Clay soil addition to sandy soil will result in the greatest OC sequestration if the added soil has high clay but low OC content and its CEC is high. Keywords Clay . Sandy soil . Soil respiration . MBC . WEOC
1 Introduction Sandy soils often have low organic C (OC) content because of poor plant growth, thus low input and rapid OC decomposition rates. Plants often grow poorly in sandy soils because they are limited by water and nutrient availability (Walpola and Arunakumara 2010). Due to the low cation exchange capacity (CEC), organic C (OC) remains readily available for decomposing microbes. The low plant input and high decomposition rates result in low OC content of sandy soils (Wada 1996; Strong et al. 2004). Clay soils, on the other hand, are
* Muhammad Riaz [email protected] 1
Department of Environmental Sciences & Engineering, Government College University Faisalabad, Allama Iqbal Road, Faisalabad 38000, Pakistan
2
School of Agriculture, Food and Wine, The University of Adelaide, Adelaide, South Australia 5005, Australia
characterised by a high proportion of micropores and high CEC, thus high water and nutrient retention and OC binding capacity (Baldock 2007; Hamarashid et al. 2010; Hassink 2016). Addition of clay soils to sandy soils has been shown to increase crop growth and OC content (Davenport et al. 2011; Schapel et al. 2017; Ye et al. 2019). However, the effect of clay soil addition on OC content has been variable. Field studies by Schapel et al. showed that
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