The phytoextraction of Cu and Zn by elephant grass (Pennisetum purpureum) from tropical soil 21 years after amendment with industrial waste containing heavy metals

Abstract

Increased soil heavy metal concentrations are suggested to cause roots to work harder. This research was to study the growth and phytoextraction behaviors of elephant grass in soil amended with industrial waste. Soil samples were obtained from an experimental field treated with a heavy metal containing waste at 0, 15 and 60 Mg ha-1, CaCO3 at 0 and 5 Mg ha-1, and compost at 0 and 5 Mg ha-1. Soil samples were planted with elephant grass, 8 weeks after which the soil samples were analyzed for Cu and Zn. Plant roots and shoots were harvested and weighed for their dry-masses and analyzed for Cu and Zn. The results demonstrate that the Root/Shoot increased and show good correlations with the increase in soil Cu or Zn. The plant Cu or Zn increased with the increase in soil Cu or Zn but decreased with liming. Plant Cu and Zn in roots and the whole plants as well as their TFs were well correlated with soil Cu and Zn. These observations confirm that the root/shoot growth and Cu and Zn absorption by elephant grass are governed by soil Cu and Zn and elephant grass is a Cu and Zn phytoextractor.

The biochar-improved growth-characteristics of corn (Zea mays L.) in a 22-years old heavy-metal contaminated tropical soil

“…Analysis of variance (Anova) indicates that waste level significantly depressed the plant height and plant biomasses (roots, shoots, and the whole plant) and significantly enhanced the soil concentrations of Cu and Zn (Table 2). Our previous researches also showed that the waste borne Cu and Zn in the soils depressed the growth of several plants including corn plant, water spinach, caisim, lettuce, and napier grass [20][21][22]. The phenomena were also in accordance with various researches previously reported [14][15][16][17].…”

“…For examples, [21] reported that the dry weight of caisim decreased by 38.1%, while those of water spinach and lettuce decreased by 52% and 100%, respectively, in soil amended with Cu-containing waste at 60 Mg ha -1 . Several other soil workers also reported the negative effects of heavy metals on the growth and production of agricultural commodities and grasses like napier grass (Penissetum purpureum) [12,17,[22][23][24] . The above problem must be solved.…”

The Potential Roles of Biochar in Restoring Heavy-Metal-Polluted Tropical Soils and Plant Growth

“…The root/shoot was shown to positively and linearly correlate with the soil-heavy metal concentration. The writer in [64] stated that higher root weight may cause higher root cation exchange capacity (CEC) that may retain The growth of several plants in heavy metal contaminated soil (S1 control, S2 low heavy metals, S3 high heavy metals; lettuce dead in S3, WAP weeks after planting) (after [63] with permission). more heavy metal cations on the surface of plants' roots so that less heavy metals may move to plant shoots.…”

“…Higher CEC can be attained by increasing soil pH [2,65]. Plant roots also produce some exudates such as low molecular organic acids The relationship between the root/shoot and the soil DTPA extracted Cu and Zn (after [64] with permission).…”

“…The research result in [73] showed that the related analysis of variance (ANOVA) also indicated that the amended waste levels significantly enhanced the soil concentrations of heavy metals particularly Cu and Zn and significantly depressed the plant height and plant biomasses (roots, shoots, and the whole plant). Several previous research also showed that the waste-borne Cu and Zn in the soils depressed the growth of several other plants including caisim, corn plant, lettuce, Napier grass, and water spinach [63,64,73]. Elevated concentrations of heavy metals in soil system are detrimental to plants.…”