I have vegetable plants in large pots. I often think of putting trays under the pots to save drained water and nutrients there in. But then every time drop the idea thinking that collected water will only keep the plant soggy and water will eventually evaporate without any benefit.
Would like to hear views and comments on the from the gardening community friends.

If when we water we don't water copiously, i.e., so a good measure (>20%) of the total volume of water used exits the drain hole, we run the risk of dissolved solids (salts) from fertilizer solutions and tapwater building up in the soil, and skewed nutrient ratios. A high level of salts in the soil limits uptake of water and nutrients, and a skewed nutrient ratio causes antagonistic deficiencies, which occur when too much of nutrient A limits uptake of nutrient B, and possibly C, D, and E. Example: Bloom-booster fertilizers (unreasonably high in P) used on containerized plants regularly cause antagonistic deficiencies of potassium, calcium, zinc, copper, and especially iron, and the excess P works as a synergist to increase magnesium uptake at the expense of calcium.

So, best practices would have us flushing the grow media of our plants very regularly to prevent these issues. Flushing salts from the grow medium and allowing them to collect in a collection saucer where they can be reabsorbed by the plant undoes the good growers do by flushing the medium. The effluent that exits the drain hole shouldn't have a pathway back into the soil. The best way to prevent that from happening is by A) Watering over the sink and returning the pots to the saucer after they have stopped draining, or B) lifting the pot above any effluent that collects in the saucer to prevent the salts from reentering the pot.


The primary take-away here is, the effluent that exits the drain hole shouldn't be considered as beneficial to your potted plants. It's fine to allow it to evaporate (I do that when plants are indoors for the winter), so long as it can't make its way back into the grow medium.

Al

I'm not nearly so scientific ^^^
I just like to put a container under plants so I can see whether they're getting more water than they need and to save the surface they're on from water damage.
If you have a buffer - stones, potsherds, styrofoam or whatever - in the bottom of the pot - or, as Tapla suggests, raise the pots - the excess water won't be re-absorbed anyway. And sometimes, if you're a bit negligent in watering, the plants might benefit from the option.
... so, it depends....
Saving nutrient by reusing the water might be more work than it's worth.