Abstract
Whether species coculture can overcome the shortcomings of crop monoculture requires additional study. Here, we show how aquatic animals (i.e. carp, crabs, and softshell turtles) benefit paddy ecosystems when cocultured with rice. Three separate field experiments and three separate mesocosm experiments were conducted. Each experiment included a rice monoculture (RM) treatment and a rice-aquatic animal (RA) coculture treatment; RA included feed addition for aquatic animals. In the field experiments, rice yield was higher with RA than with RM, and RA also produced aquatic animal yields that averaged 0.52-2.57 t ha-1. Compared to their corresponding RMs, the three RAs had significantly higher apparent nitrogen (N)-use efficiency and lower weed infestation, while soil N contents were stable over time. Dietary reconstruction analysis based on 13C and 15N showed that 16.0-50.2% of aquatic animal foods were from naturally occurring organisms in the rice fields. Stable-isotope-labeling (13C) in the field experiments indicated that the organic matter decomposition rate was greater with RA than with RM. Isotope 15N labeling in the mesocosm experiments indicated that rice used 13.0-35.1% of the aquatic animal feed-N. All these results suggest that rice-aquatic animal coculture increases food production, increases N-use efficiency, and maintains soil N content by reducing weeds and promoting decomposition and complementary N use. Our study supports the view that adding species to monocultures may enhance agroecosystem functions.
Highlights
Biological simplification and reliance on chemicals have increased the concern with the low levels of biodiversity in modern, intensive agriculture (Li et al, 2007; Smith et al, 2008; Kremen et al, 2012; Ren et al, 2014; Brooker et al, 2021)
We found that rice yield was significantly higher in the rice-aquatic animal (RA) treatment than in the rice monoculture (RM) treatment in the rice-carp experiment (F1,10=7.828, p = 0.019), the rice-crab experiment (F1,10=5.957, p = 0.035), and the rice-turtle experiment (F1,10=12.472, p = 0.005) (Figure 1a)
Compared to the corresponding monoculture, average rice yield over the 4 years in the RA treatment was 9.13% ± 3.11% higher for rice-carp, 12.05% ± 1.16 higher for rice-crabs, and 8.69% ± 1.74 higher for rice- turtles
Summary
Biological simplification and reliance on chemicals have increased the concern with the low levels of biodiversity in modern, intensive agriculture (Li et al, 2007; Smith et al, 2008; Kremen et al, 2012; Ren et al, 2014; Brooker et al, 2021). Ecology eLife digest Monoculture, where only one type of crop is grown to the exclusion of any other organism, is a pillar of modern agriculture. This narrow focus disregards how complex inter-species interactions can increase crop yield and biodiversity while decreasing the need for fertilizers or pesticides. Many farmers across Asia introduce carps, crabs, turtles or other freshwater grazers into their rice paddies This coculture approach yields promising results but remains poorly understood. It is unclear how these animals’ behaviours and biological processes benefit the ecosystem
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