Co-Cropping Indian Mustard and Silage Maize for Phytoremediation of a Cadmium-Contaminated Acid Paddy Soil Amended with Peat.

Sifan Wang,Jialin Li,Yong Liu,Huihua Zhang,Zed Rengel,Zhiqiang Zhu,Yuzhen Yuan,Fangbai Li,Khalil Kariman,Chuanping Liu,Yinglong Chen,Chongjian Ma

doi:10.3390/toxics9050091

Abstract

Co-cropping is an eco-friendly strategy to improve the phytoremediation capacity of plants growing in soils contaminated with heavy metals such as cadmium (Cd). This study was conducted to investigate the effects of co-cropping Indian mustard (Brassica juncea) and silage maize (Zea mays) and applying peat on the phytoremediation of a Cd-contaminated acid paddy soil via characterizing plant growth and Cd uptake in pot experiments. There were six planting patterns (Control: no plants; MI-2 and MI-4: mono-cropping of Indian mustard at low and high densities, respectively; MS: mono-cropping of silage maize; CIS-2 and CIS-4: co-cropping of Indian mustard at low and high densities with silage maize, respectively) and two application rates of peat (NP: 0; WP: 30 g kg−1). When Indian mustard and silage maize were co-cropped, the shoot biomass of Indian mustard plants per pot was significantly (p < 0.05) lower than that obtained in the mono-cropping systems, with a substantial reduction (55–72%) in the same plant density group. The shoot biomass of silage maize plants in the mono-cropping systems did not differ significantly from that in the co-cropping systems regardless of the density of Indian mustard. The growth-promoting effect of the peat application was more pronounced in Indian mustard than silage maize. Under the low density of Indian mustard, the co-cropping systems significantly (p < 0.05) decreased Cd uptake by silage maize. Additionally, soil amendment with peat significantly (p < 0.05) increased shoot Cd removal rate and Cd translocation factor value in the co-cropping systems. Taken together, the results demonstrated that silage maize should be co-cropped with Indian mustard at an appropriate density in Cd-polluted soils to achieve simultaneous remediation of Cd-contaminated soils (via Indian mustard) and production of crops (here, silage maize). Peat application was shown to promote the removal of Cd from soil and translocation of Cd into shoots and could contribute to enhanced phytoremediation of Cd-contaminated acid paddy soil.

Highlights

The analysis of variance (ANOVA) results revealed that the Pattern × peat application (Peat) interaction exhibited a significant (p < 0.05) effect on the diethylenetriaminepentaacetic acid (DTPA)-extractable Cd concentration in soil
Some studies have reported a negative relationship between pH and DTPA-extractable Cd in peat-amended soils [25,26], our results showed the application of peat significantly increased soil pH, but the DTPA-extractable Cd concentrations did not decrease as a consequence because pH remained below 5.0, ensuring relatively high Cd availability (Figure 1)
When Indian mustard and silage maize were co-cropped, the shoot growth of Indian mustard per pot was reduced considerably, as compared with that obtained in the mono-cropping systems

Summary

Introduction

According to Wang et al [3], during 2001–2010, anthropogenic activities such as smelting, mining, waste disposal, pesticide and fertilizer application, and emissions from motor vehicles led to a substantial increase in Cd contamination of soils in China. Quality Standard for Soils (GB 15618-1995), with Cd accounting for almost half (7%) of that increase, ranking the first among inorganic pollutants [4]. Recent Cd-related food safety incidents (“Cd rice” and “Cd wheat”) has generated widespread awareness of Cd contamination of farmland soils and the safety of agricultural products [5]. The remediation of Cd-contaminated farmland soils is a high-priority environmental challenge that must be urgently addressed

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