Effects of “plant-fish” integrated farming system on the growth and quality of Nelumbo nucifera Gaertn and Trapa acornis Nakano in the lowland areas

As an innovative farming system, integrated “plant-fish” farming has since 2010 developed rapidly in the lowland areas of North Zhejiang Province. This region generally lies in very low altitudes. To optimize integrated aquatic vegetable cultivation in “plant-fish” farming systems, a comparative experiment was carried out in two farms. The growth, quality and food security of Nelumbo nucifera and Trapa acornis in different integrated aquaculture farming systems were analyzed. The results showed that the growth and development, commodity feature and quality of N. nucifera improved in integrated “plant-fish” farming systems. Compared with monocropping system of N. nucifera (control), “plant-fish” integrated farming systems increased N. nucifera leaf length, leaf width and petiole length by 1.2%~38.2%, 8.6%~30.9% and 10.1%~33.2%, respectively. Similarly, N. nucifera commodity features improved under integrated “plant-fish” farming systems. Total tuber weight and maximum tuber node weight of N. nucifera in “plant-fish” integrated farming systems increased by 19.0%~77.8% and 22.0%~77.5%, respectively, compared with the control. N. nucifera nutritional quality also improved. N. nucifera contents of starch, protein and total amino acids in “N. nucifera-Pelteobagrus fulvidraco and Misgurnus anguillicaudatus” farming system increased by 34.0%, 47.3% and 48.7%, respectively, compared with the control. Also those in “N. nucifera-Carassius auratus and P. fulvidraco” system were respectively 23.3%, 5.4% and 11.3% higher than those in the control. In “N. nucifera-Ophicephalus argus” system, N. nucifera starch content was 31.1% higher than that in the control. However, the contents of protein and total amino acids decreased respectively by 20.4% and 5.3% over the control. The results also showed that in “T. acornis-Trionyx sinensis” system, growth, development and commodity features of T. acornis increased significantly. T. acornis leaf and phyllome size was larger than that of the control (monocropped T. acornis in fishpond). Also T. acornis fruit fresh weight was 6.2% higher than the control, but contents of rough protein and total amino acids were 16.0% and 17.0% lower than the control. Under “T. acornis-O. argus” farming system, T. acornis growth and development were lower than those of the control. However, commodity features and nutritional quality were higher, with rough protein and total amino acids contents 3.8% and 2.7% higher than the control. In terms of food security, no significant difference in pesticide residue and heavy metal toxicity in N. nucifera and T. acornis products between integrated “plant-fish” farming and monocroppong systems was noted.