Baanthonglaanglai farm is in Lat Bua Luang district of Phra Nakhon Si Ayutthaya province in the central plain region of Chao Phraya river basin. The name “Lat Bua Luang” in Thai means “Swamp of Sacred Lotus”, indicating native flora often found in the area. It has been almost three years since I started the dream project to convert monocrop of rice field into agroforestry. I think I should start observing and taking notes on flora and fauna succession during the early phase of the project between May 2016 and April 2019.
Having looked at the geological reports related to the site, I came across the literature on the soil in the southernmost of Chao Phraya river basin, the Bangkok Clay, published in 1983 by Chonglakmani and co-workers. The fossil oyster shell of the length of 30 – 40 cm found within the depth around 3 – 4 meters during the excavation could be the Crassosterea gigas. This species is commonly found in Bangkok Clay within the depth of 3 to 7 meters below ground level, similar species as the famous fossil at Wat Chedi Hoi (วัดเจดีย์หอย) 30 kilometers away. The carbon dating cited in the literature suggested the sedimentation compact of 5,500 years before present.
Fast forward to the present day, the land was used for monocrop plantation for more than fifty years, mostly for fruit trees until the 90’s. However, it has been used to grow paddy during the last 20 years. I guess the land has lost flora and fauna diversity due to the use of agro-chemicals such as herbicides and pesticides in monocrop plantation for a very long time. Only during the past 3 years that I could manage to stop using agro-chemicals for a 10-acre land plot to grow banana, mango, coconut, sour tamarind, fast-growing trees like rain tree, mahogany, neem, senna, bamboo, acacia and so on.
A long-time friend from Australian National Botanic Gardens came for a visit so I took him to the farm. We began to talk about native and new introducing plants that have not been in the area before. My new job is to observe if they are invasive and possible threats since we have a lot more birds and insects in the farm. The agroecology at Baanthonglaanglai site will be more dynamic in the future.
Ironically the invasive native plant is sacred lotus (Nelumbo nucifera). Before I started the project, the farmers already have a swamp of sacred lotus that they could not get rid of the plant. The fishes in the swamp could not breath due to limited oxygen especially in hot summer days. The rhizomes of the lotus has invaded the drainage groove in Baanthonglaanglai plantation area during rainy season in 2018. We’ll see how we could control the migration or make use out of this invasion. I may be able the increase the height of the rich top soil eventually.
For those who are interested in geological information of Bangkok Clay (soft marine clay deposited where Chao Phraya river interacted with marine process as a sea-level change during Holocene epoch):
Chonglakmani, C. Ingavat, R., Piccoli, G. and Robba, E. 1983. The last marine submersion of the Bangkok area in Thailand. Memorie Di Scienze Geologiche. Padova, v.XXXVI, 343 – 352.
Teerachaikulpanich, N. and Phupat, V. 2003. Geological and geotechnical engineering properties of Bangkok Clay. https://www.jstage.jst.go.jp/article/jiban/JGS38/0/JGS38_0_143/_pdf/-char/ja accessed 12 April 2019.