Biodiversity utilization and productivity in agriculture
Biological simplification and chemical reliance in modern agriculture has highlighted the concerns of biodiversity utilization in intensive agriculture. Biodiversity has been successfully used in traditional agricultural systems and has contributed to food and livelihood security throughout the world for centuries. Among the successful traditional agricultural systems, legume-cereal intercropping (in uplands), rice-fish co-culture (in paddy fields), and agroforestry are the three of the more important examples. Recognizing the effects of species diversity on the crop yield in these traditional agricultural systems may help us develop novel methods of sustainable agriculture. Here, we synthesize the current advances in our understanding of how traditional agriculture systems with co-cultured species can ensure sustainable food production while minimizing environmental damage by conducting a meta-analysis. Crop yield in legume-cereal intercropping or rice-fish co-culture or agroforestry, and the corresponding monoculture was used in the meta-analysis. Papers published in the past twenty-years (1990-2012) were search in the public database using key words legume-cereal intercropping, or rice-fish, or agroforestry. The effect size was calculated as the natural log of the response ratio (R, the mean of intercropping, or rice-fish, or agroforestry divided by the mean of monoculture). A positive effect size with confidential intervals (CIs) that do not overlap zero would indicate that the crop yield in intercropping, or rice-fish, co-culture or agroforestry than with monoculture.
Our results from meta-analysis indicated that legume–cereal intercropping significantly increased cereal yield but did not affect legume yield. The positive effect size on cereal yield was greater with pesticide use but was not influenced by the other five factors (climate, planting pattern, irrigation, fertilization, or weed control). For legume yield, the effect size was not influenced by any of the six factors. Although our meta-analysis showed that legume-cereal intercropping only significantly increased cereal yield, many studies indicated that legumes and cereals benefited each other in the legume–cereal intercropping systems. On one hand, legumes benefit cereals by N