Changes in soil organic C, N, labile-C pool and soil microbial biomass-C in the lowland of Cambodia

The research aims (i) to investigate the impact of tillage (plow-based and no-till) and cropping systems on rice yield, (ii) to evaluate the impact of conventional tillage and CA systems on total soil organic C, nitrogen and labile-C pool, and (iii) to quantify the impact of tillage and cropping systems on soil microbial biomass-C.

Leng Vira (Msc): Tokyo University of Agriculture and Technology, General Directorate of Agriculture and Conservation Agriculture Service Center (CASC).

Partners: Kimura Sonoko Dorothea and Tanaka Sensei, Tokyo University of Agriculture and Technology (TUAT); Tran Sopheak (CASC), Rada Kong (CASC), Stéphane Boulakia and Florent Tivet (CIRAD/CASC).

The experiment of an area of 2.6 ha is located on the Block S2B8 nearby Boeng Lvea village (12°32’55” N and 105°08’47” E) in the Stung Chinit irrigation scheme. The location was chosen for its poor soil fertility, 70-80 % of sand and less than 1 % of organic matter (0-10 cm), offering among most adverse situation encountered in the fully irrigated part of the irrigation scheme (Boulakia et al., 2013).

The current experiment was initiated in 2011 and the experimental design consists of four main paired-plots which are briefly described as follows: Block 1; intensive rice production of Conventional Tillage (CT) compared with Conservation Agriculture Practice Systems (CAPS) with three times of short cycles (sc) rice (var. IR 504) per year, Block 2; CT compared with CAPS with two times of rice per year; a counter season rice (IR 504) from April to July followed by a main cycle with photosensitive (ps) rice (var. Phkar Romdul) from early July to the end of November, Block 3; CT compared with CAPS with two times of rice per year; a main cycle with photosensitive (ps) rice (var. Phkar Romdul) from June to the end of November followed by spring cycle (IR 504) from December to March, and Block 4; CT compared with CAPS with only one main cycle with photosensitive (ps) of rice (var. Phkar Romdul) per year (Boulakia S. et al., 2013).

Four composite samples per plot were collected in December 2014 after 4 years of cultivation at 0-5, 5-10, 10-20, and 20-40 cm depths.

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