Does the application of silicon and Moringa seed extract reduce heavy metals toxicity in potato tubers treated with phosphate fertilizers?

Two field trials were carried out in two successive agricultural seasons to study the possibility of using silicon (Si) and Moringa seed extract (MSE) for reducing heavy metal contamination resulting from phosphate fertilizers addition to potato tubers. A randomized complete block design experiment was performed using three replicates. Various sources of phosphate fertilizers as ordinary super phosphate and rock phosphate were added at rate of 100 kg P ha-1 prior sowing. Silicon was added as potassium silicate (20% SiO2) at rate of 6 L ha-1, and MSE was also added at rate of 150 L ha-1 in three equal doses with the 2nd, 4th, and 6th irrigations during the last 10 min of drip irrigation. Results indicated that the addition of phosphate fertilizers increased fresh tuber yield, dry weight yield, NPK uptake, catalase, peroxidase, superoxide dismutase, and glutathione reductase of potato either alone or combined with silicon and MSE. The accumulation rate of Cu, Cd, and Ni in potato was higher with the single addition of rock phosphate fertilizer compared with single addition of super phosphate fertilizer. The highest reduction (P < 0.05) in heavy metal accumulation in potato leaves and tubers as well as soil was found with MSE treatment plus super phosphate fertilizer. It is recommended to add MSE at a rate of 150 L ha-1 along with fertilizing the potato crop with ordinary super phosphate fertilizer.