Diversity and functions of soil macrofauna in organic and conventional wheat ecosystems

Abstract

Conventional agriculture is one of the widely adopted agricultural practices globally with an aim to increase production. This practice effectually increases yields, but with a growing array of environment and health concerns. Organic agriculture is reflected as a "sustainable substitute" for conventional agriculture, this phenomenon was investigated in this study by comparing the patterns of diversity and community structure of soil macrofauna as well as their relations with soil properties in organic and conventional ecosystems. Macrofauna was selected as model organisms for this study because these fauna groups are sensitive to changes in their environment and changes in their community structure offer an integrative assessment of ecosystem effects. Soil macrofauna were sampled using standardised procedures of Tropical Soil Biology and Fertility, in organic, intercropped and conventional wheat agroecosystems. The results show that the studied soil macrofauna groups, with an exception of Hymenoptera termites, are negatively affected by the intensity of conventional management, the organic and the intercropped systems exhibited similarities in species distributions, this was attributed to the cultural management practices applied to these systems where livestock manures and mulches, as well as practices such as no-till, are incorporated into the soil. Results obtained from the soil characterisation and analysis revealed that the dissimilarities in agroecosystem management have a significant influence on soil physicochemical properties, which consequently influences the distribution of the macrofauna assemblages. Stable isotopes did not reveal any significant differences between the systems, however macrofauna taxa, plant and soil samples from the organic systems were rich in natural abundance stable isotopes signatures, this aspect needs further investigation through extensive sampling under long term experiments, to observe clear differences. The general results of this study show that organic farming as an agricultural management strategy is the most stable system that positively supports the diversity in the soil macrofauna community and soil physicochemical properties as compared to the conventional system. Macrofauna diversity and functioning in the soil are affected by conventional agriculture, this may have negative implications for nutrient cycling and soil health in ecosystems cultivated under conventional monoculture, tillage and chemical intensifications. Continual research would be imperative to discover how the soil macrofauna contributes to ecosystem function and how they affect the soil ecosystem itself.