Effects of earthworms on soil properties and rice production in the rainfed paddy fields of Northeast Thailand

Earthworms play an important role in soil fertility because of their effects on soil properties, and especially the creation of casts that usually have different properties than the surrounding soil. If the influence of earthworms on soil properties and plant growth has been extensively studied in aerobic ecosystems, their effects remain largely unknown in partially flooded environments such as paddy fields. The aim of this study was to describe the potential influence of earthworms on soil properties and rice yield in Northeast Thailand.Westudied the abundance of aboveground casts produced by Drawida beddardi in two paddy rice systems (transplanting: TP and direct seeding: DS) and we measured the soil physicochemical properties of casts and their influence on rice growth and yield. Cast abundance was low (250 casts per ha) and not different in TP and DS. Casts appeared as patches of fertility with more fine particle sizes and organic matter contents, a higher CEC, as well as a much higher concentrations of mineral elements (N, P and K). As a consequence, our results suggest that earthworm activity lead to a significant higher rice yield. These results stress the importance earthworms could have in the regulation of rice productivity in paddy fields. More research is now needed to understand the ecological mechanisms that regulate earthworm abundance and activity in these environments

Termite mounds and dykes are biodiversity refuges in paddy fields in north-eastern Thailand

Paddy fields in north-eastern Thailand are heterogeneous agro-ecosystems that can be described as mosaics of paddy rice plots, dykes and termite mounds. The aim of this study was to determine if this heterogeneity influences soil macrofauna biodiversity. While biodiversity did not vary as a result of different rice management practices (direct seeding and transplanting), dykes and mounds were vital to the maintenance of soil macrofauna biodiversity. Diversity and density were higher in termite mounds and field dykes, compared to rice plots, especially during the rainy season. Consequently, termite mounds and dykes can be considered to be biodiversity hotspots that behave as refuges for other soil macrofauna during the rainy and dry seasons, providing protection against flooding and dryness. The importance of these patches of biological activity in terms of ecosystem functioning and services are discussed

Effects of earthworms on soil properties and rice production in the rainfed paddy fields of Northeast Thailand

Earthworms play an important role in soil fertility because of their effects on soil properties, and especially the creation of casts that usually have different properties than the surrounding soil. If the influence of earthworms on soil properties and plant growth has been extensively studied in aerobic ecosystems, their effects remain largely unknown in partially flooded environments such as paddy fields. The aim of this study was to describe the potential influence of earthworms on soil properties and rice yield in Northeast Thailand. We studied the abundance of aboveground casts produced by Drawida beddardi in two paddy rice systems (transplanting: TP and direct seeding: DS) and we measured the soil physicochemical properties of casts and their influence on rice growth and yield. Cast abundance was low (similar to 250 casts per ha) and not different in TP and DS. Casts appeared as patches of fertility with more fine particle sizes and organic matter contents, a higher CEC, as well as a much higher concentrations of mineral elements (N, P and K). As a consequence, our results suggest that earthworm activity lead to a significant higher rice yield. These results stress the importance earthworms could have in the regulation of rice productivity in paddy fields. More research is now needed to understand the ecological mechanisms that regulate earthworm abundance and activity in these environments

Different effects of earthworms and ants on soil properties of paddy fields in North-East Thailand

As soil engineers, earthworms and ants play major roles in soil functioning, especially in modifying soil physical and chemical properties. This study was conducted in a very constraining environment, i.e., paddy fields which have anoxic conditions (approximately four months per year), and which are affected by soil salinisation during the dry period (approximately eight months per year). This study points out that despite those very adverse conditions, soil invertebrates must be taken into account in the dynamic of soil organic and mineral properties in paddy fields. The effects of one earthworm species, Glyphodrillus sp., and an ant species, Epelysidris sp., on soil physical and chemical properties were determined through elemental soil physical and chemical properties (texture, pH, conductivity, C and N contents) and near infrared reflectance spectroscopy (NIRS) in order to evaluate their ability to influence soil organic matter quality. PCA processed with NIRS data clearly showed that biogenic structures (ant sheetings and earthworm casts) were separated from the control surrounding soil. Earthworms and ants affected differently soil properties. Glyphodrillus sp. increased the SOM content and decreased the pH on the surface of the soil. These effects were attributed to an increase in fine particle content (clay). Conversely, Epelysidris sp. only increased the content of coarse particles (sand) and did not influence either soil pH or SOM content. Soil conductivity was found to be very variable but was not significantly affected by soil invertebrates. These results show the potential of soil macro-fauna to create heterogeneity at small spatial scale and to modify the quality of surface soils even under adverse conditions like saline paddy fields

Special section on insects and the UN sustainable development goals

Termites are amongst the main macroinvertebrate decomposers in tropical ecosystems and they exert additional impacts through the creation of biostructures (mounds, galleries, sheetings, etc.) with different soil physical and chemical properties, thereby impacting positively on numerous ecosystem services for humankind. Unfortunately, this positive or 'bright' role of termites is often overshadowed by their 'dark' side, that is, their status as pests threatening agriculture and constructions. This article assesses advances in our knowledge of the impact of termites on several sustainable development goals (SDGs 1 'no poverty', 2 'zero hunger', 3 'good health', 9 'innovation', 11 'sustainable cities', 13 'climate action' and 15 'life on land'). Finally, using the Indian myth of Valmiki as a parable, we illustrate that a reconciliation between the termite's dark and bright sides is needed if we want to reduce our dramatic impact on biodiversity and more generally achieve SDGs