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

Abstract

Over 50 years of the Green Revolution since the 1960s, the global population has increased by 2.5 times, cereal production by 3.3 times and the use of N, P and K fertilisers by 9.4, 4.2 and 4.3 times, respectively. Information is still limited, however, on the influence of these impacts on the fertility status of agricultural soils. Here we investigated the influence of the Green Revolution on 142 paddy soils in three tropical Asian countries, that is, Thailand, the Philippines and Malaysia, during the given period by repeated soil sampling in the 1960s and 2010s at or near the same locations. We revealed that the phytoavailablility indices of three macronutrients – N, P and K, that is, available P, exchangeable K and total N, showed 743% (p < 0.01), 12% and 1% increase on average, respectively, while total C showed 9% decline. Comprehensive investigation of overall fertility status by factor analysis using 11 soil parameters suggested that only the factor scores associated with ‘available P status’ increased drastically in all the three countries (p < 0.01) whereas those associated with ‘organic matter and N contents’ and ‘inherent potentiality’ did not exhibit any consistent changes among the countries. In conclusion, intensive soil/fertiliser management systems under the Green Revolution have successfully improved the nutrient status, especially P status, of paddy soils with slight decrease of soil organic matter over the last 50 years, while a large amount of nutrients applied, especially N and K, has been released from soil to the outer environments. Conversion to a high‐efficiency system of external nutrient inputs with organic matter‐conserving strategies is, therefore, urgently required to secure sustainable food production while restoring the environment during the coming decades. Highlights Paddy soils from 142 locations in three tropical Asian countries were repeatedly surveyed in the 1960s and 2010s. Available P increased by 8.4 times, that of exchangeable K and total N showed 12% and 1% increase, while organic matter level showed 9% decline. Factor analysis indicated significant increase of the factor scores for those associated with ‘available P status’. A high‐efficiency system with organic matter‐conserving strategies is to be established for both sustainable food production and restoration of the environment.

Use of soil nonexchangeable potassium by paddy rice with clay structural changes under long‐term fertilizer management

“…This can be comparable to the findings that long‐term paddy rice cultivation in China induced decrease of neK coupled with the decrease of illite and muscovite (Han et al, 2019). The release of interlayer K from micaceous minerals in respond to the intensive uptake of K by paddy rice would be generally observed widely in temporal and tropical regions and can be linked with long‐term changes in paddy soil fertility in tropical Asia (Yanai et al, 2022).…”

Soil Fertility Evaluation in Long-term Paddy Field on Small Island: A Preliminary Research in Savana Jaya Village, Buru Island, Maluku Province, Indonesia

“…Nakao et al [23] and Yanai et al [9] reviewed that the levels of Nitrogen (N), Phosphorus (P), and Potassium (K) in soils of tropical Asia (Thailand, Philippines, Malaysia) were lower than compared to temperate soils. This discrepancy can be attributed to the relatively intensive weathering of soil minerals due to the warm and humid climate and the relatively low levels of past fertilizer application in tropical regions.…”

“…The phenomenon can potentially diminish soil fertility and pose a significant risk to the viability of soil-dwelling species, including earthworms and bacteria. Also, water pollution is a major environmental issue caused by the extensive use of inorganic fertilizers, resulting in the contamination of surface and groundwater sources [9]. The phenomenon can potentially diminish the overall quality of water and pose a significant risk to the viability of various aquatic creatures, including fish and plankton.…”

'Only One Earth' – Celebrating soil science on World Environment Day 2022

“…In another long-term experiment lasting 31 years in a highland agroecosystem, Su et al (2022) find that pure legume cropping can lead to increased microbial residues and SOC accumulation. At a continental scale, a repeated survey of Asian paddy soils in the 1960s and 2010s conducted by Yanai et al (2022) finds an increase in available phosphorus but a decline in soil organic matter. This Virtual Issue concludes with "hard talk".…”