Phytoremediation potential of forage mulberry (Morus atropurpurea Roxb.) for cadmium contaminated paddy soils.

Mulberry is an important material to utilize the Cd polluted farmland in China and planting forage mulberry is a new development direction. This study aimed to investigate the changes of annual biomass and Cd content in shoot of Guisangyou 62, Guisangyou 12 and Yuesang 11 in field XT-C1, XT-X1 and ZZ-M1 under the pressure of Cd in 3 years. The Cd extraction ability of forage mulberry was analyzed, and the safety of forage mulberry was also discussed. The results showed that the annual biomass of each forage mulberry shoot could reach 64.52 ∼ 86.61 t/hectare (ha). The total harvest biomass of Guisangyou 12 was the highest, followed by Guisangyou 62 and Yuesang 11. In the same test area, for different forage mulberry varieties, there were no significant differences in Cd content in the shoot at each sampling time, and the Cd concentrations in shoot were in the range of 0.05 ∼ 0.66 mg/kg, meeting the hygienical standard for feeds (GB 13078-2017, China). Without considering the test area, the average Cd removal amount of each forage mulberry in a year was about 18.52 g/ha. Planting forage mulberry may become a new ecological economic model to achieve the safe utilization of Cd polluted farmland.Novelty statement Mulberry is one of the most important plants for safe utilization the Cd polluted farmland in China and planting mulberry as animal feed is a new development direction. This study investigated the effects of Cd on the shoot biomass of 3 forage mulberry varieties at 3 experimental areas in 3 years. It also examined how much Cd could be removed from soil by harvesting forage mulberry for 4 times a year. The Cd content in the shoot of forage mulberry and its safety were also evaluated.

Accumulation of Cd by three forage mulberry (Morus atropurpurea Roxb.) cultivars in heavy metal-polluted farmland: a field experiment.

A 3-year field experiment was conducted to evaluate the accumulation ability of 3 forage mulberry (Morus atropurpurea Roxb.) varieties (Guisangyou 62, Guisangyou 12, Yuesang 11) for Cadmium (Cd). The results showed that the shoot biomass of forage mulberry could reach to 64.51~69.58 t/ha in 2018. The total production of Guisangyou 12 was the highest among the tested 3 cultivars in each year. However, the biomass of the 3 varieties displayed without significant differences at every sampling time. In addition, the concentrations of Cd in the roots of the 3 mulberry cultivars were higher than those in the corresponding shoots in 2018. But in 2019, the Cd content in roots was near to that of shoots. The Cd concentrations in the roots of the forage mulberry showed Guisangyou 62 > Yuesang 11 > Guisangyou 12. And the Cd concentrations in shoots of all the 3 tested forage mulberry varieties were less than 1 mg/kg, meeting the hygienical standard for feeds (China). Though the 3 forage mulberry varieties were not hyperaccumulators for Cd, they could be used as alternative plants to make use of the Cd-polluted (< 1.0 mg/kg) paddy soils.

The mobility of cadmium and lead in the soil-mulberry-silkworm system.

Evaluation of the transportation of heavy metals in food chain has received a great deal of attention. In this study, the mobility of cadmium (Cd) and lead (Pb) in soil-mulberry-silkworm system was assessed. The results showed that bioconcentration factors for Cd and Pb were lower than 1 for all the three mulberry cultivars. Higher translocation factors (TFs) were observed in the levels from branch to leaf, larvae to excrement. The BCFs of Pb in root and silkworm excrement were higher than those in the other parts. Meanwhile, most of Cd accumulated from soils located in the root (48.00-54.40%) and only about 10% was in the leaf. But the Cd and Pb had significant effects on the ratios of cocoon shell with Yuesang 11 under different planting densities. For Yuesang 11 and Qiangsang 1, the Pb percentages were roots > branches > leaves > stems. The rates of ingestion (IR) and digestion (DR) were a little higher than those in the control at first and then decreased gradually with time. The IR reached the lowest values on 8th day while the DR arrived at the highest. Planting mulberry and raising silkworm could be a reasonable method for the utilization of heavy metal contaminated paddy soils.