TY - JOUR

T1 - Effects of rice-straw derived phytoliths on the surface charge properties of paddy soils

AU - Nguyen, Anh M.

AU - Tran, Chinh T.

AU - Nguyen, Van T.

AU - Vu, Trang T.T.

AU - Nguyen, Ly N.

AU - Dultz, Stefan

AU - Nguyen, Minh N.

PY - 2021/10/15

Y1 - 2021/10/15

N2 - Straw of rice (Oryza sativa), a high Si-accumulating plant, is typically composed of amorphous silica bodies (namely phytoliths) that are deposited within the plant tissues. Recycling of rice straw is a traditional agricultural practice that introduces phytoliths into soil in many paddy regions. While the role of phytoliths as a carrier for nutrients, e.g., K, P, or terminal sink of Si, has been reported, it remains unclear to what extent phytolith can carry charges and act as a charge-interchange constituent in soils. Therefore, it was hypothesized that soil phytoliths can be involved in charge-related interactions e.g., pH buffering, multivalent cation exchange, polymerization, colloid stability or reactive transports. Based on a polyelectrolyte titration technique, our study evaluated surface charge (SC) dynamics of straw-derived phytoliths and paddy soils in the Mekong river and Red river deltas to characterize the possible contribution of phytoliths to soil SC properties. Phytoliths were extracted by both dry and wet ashing techniques and the SC of the obtained phytoliths were measured in the pH range from 3.5 to 8.0. The SC was detected to vary from slightly positive at low pH to –78.5 mmolc kg−1 at slightly alkaline pH, suggesting that these materials carry variable charges and could be a significant source of charge when they are returned to soil in relatively large quantities. Multiple regressions indicated that phytoliths, to some extents, can together with other soil constituents such as clay minerals, organic matter and iron oxides, regulate the SC of paddy soils. Despite phytoliths being more or less soluble, their SC properties suggest that the annual recycling of rice straw to paddy soils, particularly after burning, can contribute to the negative SC system. The phytolith-derived charge in turn might affect soil cation exchange capacity (CEC), dispersibility of clay particles and transport of solutes.

AB - Straw of rice (Oryza sativa), a high Si-accumulating plant, is typically composed of amorphous silica bodies (namely phytoliths) that are deposited within the plant tissues. Recycling of rice straw is a traditional agricultural practice that introduces phytoliths into soil in many paddy regions. While the role of phytoliths as a carrier for nutrients, e.g., K, P, or terminal sink of Si, has been reported, it remains unclear to what extent phytolith can carry charges and act as a charge-interchange constituent in soils. Therefore, it was hypothesized that soil phytoliths can be involved in charge-related interactions e.g., pH buffering, multivalent cation exchange, polymerization, colloid stability or reactive transports. Based on a polyelectrolyte titration technique, our study evaluated surface charge (SC) dynamics of straw-derived phytoliths and paddy soils in the Mekong river and Red river deltas to characterize the possible contribution of phytoliths to soil SC properties. Phytoliths were extracted by both dry and wet ashing techniques and the SC of the obtained phytoliths were measured in the pH range from 3.5 to 8.0. The SC was detected to vary from slightly positive at low pH to –78.5 mmolc kg−1 at slightly alkaline pH, suggesting that these materials carry variable charges and could be a significant source of charge when they are returned to soil in relatively large quantities. Multiple regressions indicated that phytoliths, to some extents, can together with other soil constituents such as clay minerals, organic matter and iron oxides, regulate the SC of paddy soils. Despite phytoliths being more or less soluble, their SC properties suggest that the annual recycling of rice straw to paddy soils, particularly after burning, can contribute to the negative SC system. The phytolith-derived charge in turn might affect soil cation exchange capacity (CEC), dispersibility of clay particles and transport of solutes.

KW - Mekong River delta

KW - Paddy soil

KW - Phytolith

KW - Red River delta

KW - Rice straw

KW - Surface charge

UR - http://www.scopus.com/inward/record.url?scp=85107115803&partnerID=8YFLogxK

U2 - 10.1016/j.geoderma.2021.115234

DO - 10.1016/j.geoderma.2021.115234

M3 - Article

AN - SCOPUS:85107115803

VL - 400

JO - GEODERMA

JF - GEODERMA

SN - 0016-7061

M1 - 115234

ER -