Shrimp–vegetable rotational farming system: An innovation of shrimp aquaculture in the tidal flat ponds of Hangzhou Bay, China

Abstract

This study was conducted to explore the feasibility of an integrated rotational farming system with shrimp Limpenaeus vannamei and three vegetable species (i.e., broccoli [Brassica oleracea], cole [B. napus], and potherb mustard [B. juncea]) in the tidal flat ponds of Hangzhou Bay, China. A six-month (November to May) vegetable planting experiment without the addition of fertilizer was conducted followed by a five-month (May to October) shrimp culture experiment. Results show that the concentrations of soil total nitrogen significantly decreased in the three vegetable rotational farming systems by the end of the experiment (P < .05), whereas a significant reduction in soil phosphorus was only observed in the broccoli and cole farming systems (P < .05). The straw fresh weight of broccoli, cole, and potherb mustard were 38.25 ± 1.29, 45.26 ± 3.03, and 30.75 ± 1.98 tons hm−2, respectively. The amount of removed nitrogen and phosphorus for the three vegetable rotational farming systems were 416.16 kg and 130.33 kg, 538.12 kg and 108.63 kg, and 17.70 kg and 19.68 kg per hectare, respectively. The nitrogen and phosphorus content in the pond water demonstrated significant variations (P < .05) in the three rotational systems at the 30th and 60th days of the experiment (P < .05). The phytoplankton species, abundance, and biomass in these rotational farming systems were significantly lower than those in the control group. The shrimp production in the rotational systems was also higher than that in control group. However, no statistical differences were observed among these groups (P > .05). The condition factor was higher in the rotational farming systems than in the monoculture group (P < .05). The shrimp costs in the rotational farming systems were similar to those in the monoculture group, whereas the shrimp returns in rotational farming systems (26,381.8 US$, 27,180.2 US$, and 26,880.6 US$ for broccoli, cole, and potherb mustard, respectively) were higher than those in the monoculture group (24,410.5 US$). The rotational farming systems of vegetables produced economic benefits for broccoli, cole, and potherb mustard (12,351.6 US$, 8699.6 US$, and 7092.7 US$, respectively). As expected, the profits of rotational farming systems were approximately 1.63 to 2.26 times higher than those of shrimp monoculture. The ecological and economic effects of different shrimp and vegetable combinations revealed that the rotational farming of shrimp and vegetables (i.e., broccoli, cole, and potherb mustard) is a feasible and sustainable development model that fits well with the conditions of shrimp ponds in the coastal tidal flats of Hangzhou Bay, China. The findings of this work have broad prospects in promoting the development of shrimp culture and in exploiting and utilizing coastal tidal flats.