Assistant Professor of Environmental Studies Dartmouth College Hanover, NH, United States
Abstract: Rice is an economically important crop in the Dominican Republic and is often grown in monocultures with high levels of chemical inputs and irrigation. In the northwestern part of the country, the nonprofit AgroFrontera encourages rice farmers to adopt sustainable rice cultivation practices including integrated pest management to reduce pesticide use and economic water management such as irrigation with recycled water to reduce adverse impacts on adjacent mangroves and increase profits. This study aims to understand the effects of the adoption of sustainable pest-management and irrigation practices by rice farmers on insect abundance and diversity. We hypothesized that farms with extended time in sustainable rice production practices would have a higher number and diversity of insects due to the reduced pesticide inputs, while farms using recycled water would have more insects due to accumulated nutrients and inter-rice paddy connectivity. We sampled insects with sticky traps in eighteen farms which use fresh or recycled water for irrigation, and are either conventional, transitioning (less than 1 year in the adoption of sustainable rice cultivation practices), or sustainable rice production for 1 year or more. A total of 4677 insects in 156 morpho-species were present, ranging from 68 to 1111 insects at each farm. Shannon’s diversity index for insect diversity was calculated for each farm, and two-way ANOVA were run to determine effects of sustainable practices and irrigation water on insect abundance and diversity. Irrigation methods significantly affected insect abundance and diversity, with a higher number and lower diversity of insects in farms with recycled water. Levels of adoption for sustainable rice practices had no statistically significant effects, nor were there any effects of the interaction between production practices and irrigation. Our results show that sustainable rice practices with reduced chemical inputs have a similar control on insect abundance with less sustainable practices and no effect on diversity. Since sustainable practices still include pesticides, reduced chemical input levels may not have a strong impact on insect populations. Recycled water appears to have a larger effect on insect abundance and diversity, which suggests the importance of socio-ecological connectivity mediated through irrigation networks in rice ecosystems. Further work examining the insect community composition, and the relationship between recycled water irrigation, nutrients and insect populations can better inform pest management for sustainable practices in rice production in DR.
