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Title: Effects of crop rotation on properties of a Vietnam clay soil under rice-based cropping systems in small-scale farmers' fields

item LINH, TRAN - Can Tho University
item GUONG, VO - Can Tho University
item TRAN, VO - Can Tho University
item KHOA, LE - Can Tho University
item Olk, Daniel - Dan
item CORNELIS, WIM - Ghent University

Submitted to: Soil Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/23/2016
Publication Date: 10/3/2016
Publication URL:
Citation: Linh, T.B., Guong, V.T., Tran, V.T., Khoa, L.V., Olk, D.C., Cornelis, W. 2016. Effects of crop rotation on properties of a Vietnam clay soil under rice-based cropping systems in small-scale farmers' fields. Soil Research. 55:162-171. doi: 10.1071/SR16123.

Interpretive Summary: Crop growth can be affected by the physical condition of the soil. The Mekong Delta is the most important rice-producing region of Vietnam, where two or three crops of rice are grown each year. We found that the physical properties of the rice soils there have worsened during decades of continuous rice production. Their physical condition was shown to improve when growing crops occasionally that do not grow in flooded conditions and require less intensive soil preparation than does rice. Our results provide one explanation why rice appears to grow better and provide more grain yield if it is rotated occasionally with other crops. These results will help local rice farmers obtain higher grain yields and better manage their soil resources. The results will also be useful to scientists who study soil management.

Technical Abstract: In tropical deltas, intensive monocultures with three rice crops per year have been the standard for decades. In recent years, though, rice-based rotations with one or more upland crops per year are being adopted by several farmers. Their trends of increasing grain yields raise the question whether the introduction of upland crops affects surface properties of an alluvial clay paddy soil. A study was therefore conducted at 40 selected farms in the Vietnamese Mekong Delta, with four different cropping systems (thus 10 farms per system) on paddy rice soils: intensive rice monoculture with three rice seasons (RRR), crop rotation with two rice and one upland crop seasons (RUR), crop rotation with one rice and two upland crop seasons (RUU), and upland crop monocultures with three upland crop seasons (UUU). Soil samples were collected at depths of 0-10, 10-20 and 20-30 cm. Most of the tested soil properties showed significant differences between intensive rice monoculture and rice-upland crop rotations or mono upland crop monocultures. Rotations with upland crops (RUR and RUU) and upland crop monocultures (UUU) alleviated soil compaction, resulting in reduced penetration resistance and bulk density and increased total and macroporosity at 20-30 cm depth. Also aggregate stability index and plant available water capacity were higher for RUR, RUU and UUU at the 20-30 cm depth as compared to RRR. The average SOC stocks ranged from 59.3 t ha 1 in UUU to 66.4 t ha 1 in RRR system. The other systems (RUR and RUU) showed SOC stock values (72.3 and 68.3 t ha 1) that were non-significantly different from that of the RRR system. Chydrolysable was 74-84% greater in rice-upland crop systems (RUR and RUU) or upland crop monocultures (UUU) than the prevailing rice monocultures. Rice-upland crop systems may help in alleviating soil degradation resulting from continuous mono cultivation systems.