Long-term changes in paddy soil fertility in Peninsular Malaysia during 50 years after the Green Revolution with special reference to their physiographic environments

Abstract

The objective of this study was to investigate the current soil properties in lowland paddy fields in Peninsular Malaysia and to assess the long-term changes in the soil fertility status during 50 years after the Green Revolution. Forty paddy fields were selected close to the study sites surveyed in 1965 and grouped based on six physiographic environments: the brackish swamp (including acid sulfate soils), the brackish alluvium, the freshwater swampand the riverine alluvium in the west coast, and the riverine alluvium and the beach ridges interspersed with swales in the east coast. Soil samples from the depth of 0-15 cm were analyzed for the physicochemical properties. Despite similar fertilizer application rates over Peninsular Malaysia, several differences were found in the current soil properties between different physiographic environments, such as 1) higher levels of clay fraction, 1.4 nm minerals, CEC, exchangeable bases and available Si as well as Mg-and Na-rich status in the brackish environments, 2) higher levels of available N in the riverine alluvium environment in the east coast , and 3) the excessive P accumulation in the acid sulfate soils. The long-term changes well appeared in the dramatic increase of P availability and the alleviation of soil acidity. In addition, the composition of exchangeable bases changed toward Ca-rich and Mg-low status. Large reduction in soil organic matter was found in the swamp environments while those in the riverine alluvium environment in the east coast were increased. It could be concluded that despite the successful increase in rice yield after the Green Revolution, the long-term changes in the paddy soil fertility showed positive and negative aspects depending on physiographic environments. Appropriate fertilizer application schemes taking into account different soil characteristics in different physiographic environments should be required to achieve both efficient, sustainable rice production and environmental conservation.

Long‐term changes in paddy soil fertility in tropical Asia after 50 years of the Green Revolution

“…Among countries, the soils in Thailand showed a significant increase of total C from 12.4 to 17.3 g kg −1 ( p < 0.01), probably because the original level was relatively low and the incorporation of more crop residues reflecting a higher yield (Yadvinder‐Singh et al, 2004; Yanai et al, 2020). Contrastingly, total C in soils in Malaysia showed a statistically insignificant decreasing trend from 40.8 to 27.8 g kg −1 due to accelerated organic matter decomposition, probably reflecting considerable conversion of peaty marsh areas into farmland and the practice of burning rice straws after harvest (Tanaka et al, 2021). Reflecting the changes in total C and N contents, the C/N ratio showed significant decrease from 12.6 to 11.4 ( p < 0.01).…”

“…Based on the overall data in Table 1, an improvement in paddy soil fertility status, especially P, in these three countries during the last 50 years was revealed but a slight decrease in soil organic matter was also observed even though statistically insignificant. The long‐term changes in paddy soil characteristics and fertility status were discussed in detail each in Yanai et al (2020) for Thailand, Nakao et al (2021) for the Philippines and Tanaka et al (2021) for Malaysia, in relation to their physiography, climate and regionality.…”

“…The Philippines had relatively fertile soils, benefited from the influence of volcanic activities providing weatherable fresh minerals as the source of soil nutrients, and has been the centre of the Green Revolution for rice, as the location of the headquarters of the International Rice Research Institute (IRRI) (Carating et al, 2014; Nakao et al, 2021). Malaysia had moderately fertile soils with widely distributed peaty marsh areas and has introduced the Green Revolution technologies intensively based on rapid economic growth (Paramananthan, 2000; Tanaka et al, 2021). Because we were able to identify the original sampling locations based on both the descriptions shown in Kawaguchi and Kyuma (1977) and personal notes by Kyuma describing interviews with local farmers and officers, we placed the sampling sites in 2010s at or near the same locations as those of the original sites from 1964 to 1972 (the 1960s) (Figure 1a–c).…”

“…We could not collect soil samples on some locations due to conversion from paddy to other land uses reflecting urbanisation or due to inaccessibility to the locations by political instability. Detailed information on the soil samples in Thailand, the Philippines and Malaysia are available in Yanai et al (2020), Nakao et al (2021) and Tanaka et al (2021), respectively, in relation to geography, geology, soil classification and field management.…”

“…(b) Location of the soil sampling sites in the Philippines (Nakao et al, 2021). (c) Location of the soil sampling sites in Malaysia (Tanaka et al, 2021)…”