Silicon Nutrition Effects on Growth, Yield and Metal Accumulation in Radish (Raphanus sativus L.) Grown with Municipal Wastewater

Abstract

Recent climate changes make the use of wastewater an emerging priority in many parts of the world to meet food security. However, wastewater use without adequate precautionary measures may deteriorate soil health as well as crop yield and quality due to the presence of heavy metals. The present study aimed to investigate the protective role of silicon (Si) against the harmful effects of wastewater on growth, yield, and metal accumulation in radish (Raphanus sativus L.). Experimental plan comprised of wastewater and six Si levels (0, 40, 80, 120, 160 and 200 mg Si kg soil -1 as potassium silicate), with five replications. Silicon as potassium silicate (K 2 SiO 3 ) was thoroughly mixed into soil before filling the pots. Recommended dose of Nitrogen (N), Phosphorus (P) and Potassium (K) fertilizers, 960 mg N pot -1 as urea, 960 mg P 2 O 5 pot -1 as triple superphosphate and 1200 mg K 2 O as potassium sulfate, were applied. Results revealed that all levels of added Si could alleviate the deleterious effects of wastewater on plant growth and yield characteristics, more pronounced protective effects at 120 mg Si kg -1 . There was an increase of 53.10% in shoot length, 113.74% tuber length, 50.0% tuber diameter and 68.63% tuber yield plant -1 with 120 mg Si kg -1 compared to wastewater irrigation without Si. It was found that N concentration improved by 37.60% in leaf and 37.58% in tuber, P 48.47% in leaf and 41.37% in tuber while K 39.11% in leaf and 36.38% in tuber with 120 mg Si kg -1 compared to wastewater irrigation without Si. Lead (Pb) concentration reduced by 27.24%, Arsenic (As) 33.89%, Nickel (Ni) 35.13%, Cadmium (Cd) 32.87%, and Chromium (Cr) 57.14% in radish leaves with 120 mg Si kg -1 compared to wastewater irrigation without Si. Moreover, plant available fraction of heavy metals in soil also markedly reduced with Si under wastewater irrigation. In conclusion, Si could protect radish plants against wastewater-induced metal toxicity by improving the concentration of N, P and K while decreasing Pb, As, Ni, Cd and Cr in plants. Wastewater could efficiently be used for growing radish by amending with Si, particularly at 120 mg Si kg -1 . However, future studies on wastewater utilization with Si can be extended to other vegetables.

Evaluation of the Effectiveness of Silicon Dioxide on Some Germination and Vegetative Growth Parameters of Radish Cultivars in Saline Conditions

“…It has been suggested that silicon also eliminates the harmful effects of heavy metal stress by precipitating heavy metals that accumulate in the soil. In this way, it provided tolerance to the harmful effects of heavy metal stress in radish (Ashraf et al, 2020). Considering that salinity affects germination by facilitating the uptake of toxic ions from the soil by germinating seeds (Yildirim et al, 2008), the curative effect of silicon in salty conditions may also be through this mechanism.…”