Raised beds, water deficits, and poorly draining soils

In my area (near the gulf coast), raised beds or mounds for planting are often beneficial because the soil can be relatively poor and not well draining. I’m planning a raised area for planting some trees in rows and have been thinking about the interesting threads here discussing water deficits for increasing brix.

Water Deficit Fruit Production info for real nerds
Nectarines just better

@fruitnut’s control over irrigation in his greenhouse is also motivating and has me wondering if there are other ways to reduce water to the trees. Has anyone ever tried covering the soil in a raised bed with plastic to divert rainwater away? The issue I see here is that water doesn’t simply move downward due to gravity but can be drawn horizontally (even even upward) as capillary forces dominate (see Water movement in soils). Maybe this would be an exercise in futility as rainwater would simply migrate into the raised bed and defeat the purpose.

That would seem to be true for the greenhouse as well but @fruitnut gets significantly less rainfall than I do and his soil is probably better draining. Steve, do you notice an increase in soil moisture in the greenhouse after a heavy rain?

Anyone have thoughts on this and whether it’s even worth exploring further?

1 Like

I do not see much moisture increase from rain and I have to water regularly.

1 Like

If these are like apples water is not the key, nitrogen is.

For cider apples nitrogen deficient soils are conductive to measurable higher sugar content in the fruit. Nitrogen drives the processes by which fruit cell walls hold water; less water in them fruits translate into a higher sugar content. Depriving your trees of water is all sorts of counterproductive. If the same metabolical process applies to your fruit I would take that angle instead.

Be mindful that this produces smaller and less pretty fruit. For cider it doesn’t matter because it all gets grinded but for table fruit looks are an intrinsic part of the experience.

No, but the roots extend outside the GH so pick up water that ran off the roof after big rains. A root barrier would be necessary to cut the GH trees off from outside water. I’ve only noticed this effect for fig trees right next to the outside walls. For stone fruit trees even 5ft from the outside I never noticed any effects from rain.

1 Like

Sugar beets are the same. To increase sugar, lower nitrogen not water. I don’t apply much if any nitrogen to my stone fruit. For stone fruit water also has a large effect on brix. I’m positive of that and it’s becoming widely recognized.

Don have you ever reduced water to your cider apple trees? Or are you just controlling what you can control?

Thanks Steve, that’s encouraging. I’ve seen elsewhere that peach roots are pretty shallow (3 feet or less) so maybe it’s worth trying. Worst case is it doesn’t work and I just have the trees planted on a raised area. I’ve grown trees in pots and have had some nice tasting fruit but container trees can be a lot of work to maintain, the fruit yield is relatively low and of small size, and in this climate, the pots go back and forth between two extremes: flood/saturated after watering and then bone dry as the summer heat and sun takes its toll through the day. Some also struggle with vigor as well and I’ve lost a few trees over the years.

If a raised bed is really cut off from rain, you’d need drip under the covering. That’s what I’m doing with my greenhouse. You don’t want the trees to get really dry and then a big rain that reaches the roots. That’s a recipe for cracked fruit.

1 Like

Yes, that would be the plan. Drip irrigation under the plastic to water in controlled amounts.

1 Like

I don’t think limiting water would be all that controllable. If you managed to pull it off you may end up stressing the tree in a bad way.

I’m blessed/cursed with really bad soils that are nothing but rocks and gravel. Basically the only real soil they get depends on how big a hole I dig and what I fill it with. That alone gives me dwarf trees on standard rootstocks. Currently I’m trying to get them to grow so I still applying fertilizer and expanding their holes. Once they are where I want them I can cut back on fertilizer and it should be a matter of time before they soak what is there already.