Effects of Residue Management on Decomposition in Irrigated Rice Fields Are Not Related to Changes in the Decomposer Community

Abstract

Decomposers provide an essential ecosystem service that contributes to sustainable production in rice ecosystems by driving the release of nutrients from organic crop residues. During a single rice crop cycle we examined the effects of four different crop residue management practices (rice straw or ash of burned straw scattered on the soil surface or incorporated into the soil) on rice straw decomposition and on the abundance of aquatic and soil-dwelling invertebrates. Mass loss of rice straw in litterbags of two different mesh sizes that either prevented or allowed access of meso- and macro-invertebrates was used as a proxy for decomposition rates. Invertebrates significantly increased total loss of litter mass by up to 30%. Initially, the contribution of invertebrates to decomposition was significantly smaller in plots with rice straw scattered on the soil surface; however, this effect disappeared later in the season. We found no significant responses in microbial decomposition rates to management practices. The abundance of aquatic fauna was higher in fields with rice straw amendment, whereas the abundance of soil fauna fluctuated considerably. There was a clear separation between the overall invertebrate community structure in response to the ash and straw treatments. However, we found no correlation between litter mass loss and abundances of various lineages of invertebrates. Our results indicate that invertebrates can contribute to soil fertility in irrigated paddy fields by decomposing rice straw, and that their abundance as well as efficiency in decomposition may be promoted by crop residue management practices.

Soil Macroinvertebrate Response to Paddy Rice Farming Pathways in Mpologoma Catchment, Uganda

“…Soil invertebrates range in size from the small microfauna (average size < 0.2 mm), such as nematodes, through the medium-sized mesofauna (0.2-2 mm), such as microarthropods and enchytraeids, to the largest macrofauna (>2 mm), such as arthropods, molluscs, annelids, and crustaceans [13,14]. By decomposing organic matter, modifying soil structure, and mediating nutrient cycling, among other functions, soil invertebrates enhance soil quality for sustainable crop production [13][14][15][16][17][18][19]. However, conservation of soil invertebrates continues to be a challenge in agricultural landscapes.…”

Rice ecosystem services in South-east Asia

“…Their efficiency was shown to be highest near the field borders indicating a positive effect of surrounding structures on decomposer invertebrates. Further, crop residue management practices were found to significantly influence the decomposition activity of invertebrates and alter their community structure (Schmidt et al 2015b). However, invertebrate abundance showed no correlation with decomposition rates.…”

The LEGATO cross-disciplinary integrated ecosystem service research framework: an example of integrating research results from the analysis of global change impacts and the social, cultural and economic system dynamics of irrigated rice production

“…crop residue management, application of agrochemicals) affect the diversity and abundance of the aquatic as well as the soil fauna, including their effects on decomposition dynamics (Paoletti and Bressan 1996;Peters et al 2013;Schmidt et al 2015b). In LEGATO, we analysed such practices and their impacts on decomposition and invertebrate diversity on this scale with experimental designs allowing us to integrate specific questions into the large framework of the LEGATO studies.…”

“…We could also show that landscape structures next to rice fields accelerate the rice straw decomposition by the invertebrate fauna (Schmidt et al 2015a). Further, using rice straw as organic fertiliser significantly increased invertebrate abundances, especially in the aquatic phase of the fields (Schmidt et al 2015b). …”