To effectively apply a protein hydrolysate solution produced with 6N HCl to plants, you should first dilute the solution to an appropriate concentration. Then, carefully apply it to the plant's roots or foliage. Ensure the pH of the solution is adjusted to a plant-friendly level (usually around pH 6-7) using a suitable buffer. Additionally, consider conducting a small-scale test before widespread application to monitor the plant's response and adjust the dosage accordingly.@Abdul sami

Atta Ur Rahman Can you tell me what concentration we should consider? or how much we should dilute it?

Directly adding 6N HCl is probably going to kill your plants. Adjust the pH to 6.8-7.2 or so (use KOH as NaOH will add lots of Na, which most plants don't tolerate well). I would suggest using a concentration dilution series. Use 0 (the buffered HCl solution) as your control, your solution straight up at the current concentration as the high end experimental, then diluted 10X, 100X, and 1000X. It will give you a place to start.