Depends on whether you want to grow the tree or try for high quality fruit. If quality, sweet and flavorful, fruit is your major goal then water only enough to avoid dropped leaves or shriveled fruit. You want the tree to slow or stop vegetative growth.

To grow a bigger tree water enough to keep it growing.

Yes, you failed to mention how old and large the trees were and their relative vigor. Exact or even approximate amounts of water will also depend on soil texture and evaporative issues which are influenced by dew, wind and temp. If you have adequate water, you want to soak the soil down at least a foot in the entire root zone when the decision to irrigate is made. Where water is limited more frequent shallow waterings can be more efficient.

Fruitnut's mantra is about less water and higher brix, which I largely agree with, but I wish I had some more precise information. Deficit irrigation is a science and I believe the results vary depending on when during the season it occurs and how it is done (such as the entire root zone or just part of it).

Do you have any more specific info on this Fruitnut? There is always a balance and trees need not only serve their fruit but also next years flowers. But that aside, I believe that benefits in sugar occur by timing the deficit late in the ripening process so you get both sugar and size.

Because I depend almost entirely on rainfall I haven't really researched this enough but I'm asking you to take the initiative Fruitnut because you are this forums deficit irrigation advocate.

Harvestman:

If one wants the full benefit then the deficit must be steady and long term. You can't have your cake and eat it too. Large fruit and maximum sweetness don't go hand in hand. But I have had several peach and nectarine this year that were mid 20s brix, at least on some fruits, and also 3.5 inches. That's a huge peach or nectarine, about 3/4 pound each.

Outdoors on my droughty soil the water deficit is often too severe resulting in small fruit with very high brix, often 30-35+, and off flavors. So everyone has to learn their own situation; weather, soil, and trees. We've had no rain in 10 months and I can hardly get anything to grow.

I'll stick by my suggestion above. I get my best fruit from peach, nectarine, and pluot when the tree slows or stops vegetative growth. Watch your trees and learn like I have if your fruit isn't sweet enough to suit.

Fruitnut, OK, so you're not interested in actual research on the subject- that's cool. But without studying it in a systematic way your advice will be narrowly anecdotal which is also completely cool.

I grow outdoors, so I have limited observational evidence of best methods of deficit irrigation because I live where it's humid.

Why would you imply that I don't watch and learn from my trees? The problem is that logical leap from limited observation leads to lots of mistakes. I watch fruit trees every working hour of every working day and still often come to very wrong conclusions.

Is the heat and drought making you cranky?

Harvestman:

This may be addressed to you but I'm writing to all those lurkers and regulars out there so it's not really addressed to you. It's addressed to any interested reader. I'm sure you do the same thing at times. Nothing I said above was meant to annoy or admonish you. And I'm a one finger typist so sometimes my style is cryptic.

I know that you watch your trees very closely and have nothing but respect for your observations. The thing is in a humid climate you are subjected to flood and drought neither of which usually lasts very long. I've learned more on this subject in the last 7 years with all the control I have than I would in 50 years outdoors.

If you really want to learn do what I've suggested before. Plant trees in pots and cover that with a high tunnel. This gives you control over the important variables, not mother nature. Have the same cultivars outdoors. You have lots of locations so already have some variability. That's the key. The same fruit in multiple environments and some where you can maintain some control of a water deficit.

There is some research out there on this subject. What I've seen is where there were water restrictions imposed by drought, reservoirs drop, and growers were forced to lower water. By and large commercial growers will never voluntarily restrict water like I've been doing. It's probably not economically viable except for a very few customers. As a result the research hasn't really been done either. The research has been a save the tree mentality not quality orientated.

I'm thinking I've probably worked about as hard on this the last 7 years as anyone anywhere. I'm confident in my observations and don't need someone backing me up. I did do University research for 30 years so I know what it takes to prove something statistically. That's not my goal. Better fruit is my goal and I've tried to share what I've learned.

Here's one example of the commercial growers/researchers mentality. Des Layne, SC peach researcher, has taken several trips to China to look at their 30,000 acres of stone fruit in greenhouses. He said that in all those trips they never broached the subject of fruit quality. Not one brix number to pass along. What more can I say.

Fruitnut, OK, maybe the heat has ME grouchy. I have seen some studies about deficit irrigation, most recently about grapes in GFM- grapegrowers are as obsessed with brix as anyone and have developed complicated irrigation strategies for that fruit.

I'm going to look into this further as I'm thinking about ways to limit water outside and planned to use plastic sheeting this year to keep the root zone of a peach tree dry to try to up its brix. Somehow I never got around to it this season and now we are in a mini-drought anyway. It's shaping up to be a high quality year.

I'm just wondering when the ideal time would be to spread the plastic. You seem to think I should stress the tree from very first growth but have you compared results from water stressing trees at various points of the season?

Right now I've stopped mowing under my bearing peach trees for the last several weeks, but there was so much resevoir they haven't even slowed growing, even though it's pretty dry the first few inches. It just got extremely hot this week, though, so stress will be coming soon if not soon enough.

I've never watered bearing age fruit trees in my own orchard. Funny though, I manage an orchard that is way over irrigated in an attempt to make the lawn look like a Scottish putting green and yet the plums are very high quality with as good a sugar as any I manage.

Excess water doesn't seem to affect plums in the same way as it does other fruit. Even on cool wet seasons the plums sugar up if you leave them on the tree long enough. I don't need a measurement to know when more sugar wouldn't improve the fruit.

Harvestman:

Sometimes I'm grouchy and not very diplomatic. Hope I wasn't too much above.

The trouble with uncontrolled experiments like I'm running is they can lead one astray. I just try to stay open minded and admit when I've been wrong, as hard as that is. My observations are open to revision at any time, or so I like to think.

Plums and pluot react to water deficit just like nectarine/peach for me. Over watered they are big, beautiful, soft, and fall off the tree as soon as ripe.

What I tried to allude to above is that outdoors in certain soil/climate/tree combinations the norm could be a built in deficit. My soil outdoors is too deficit unless I flood about twice a week, three times for sweetcorn.

The trouble with a poly soil cover to direct the water away from the roots is that it might need to be very large. And too dry is just as bad for tree health and fruit quality as too wet.

Yes, I realize that I'd have to be attentive to the tree and not take the deficit too far. Maybe next year I can tell you how it worked out.

This is a 3rd year peach tree fruiting for the 1st time. We had rain the past two nights and plenty of it.

The fruit should be ripe on this Reliance tree in about two weeks. Perhaps due to the intense heat and lack of moisture the fruit size appears smaller than I would have expect this late in the season. During the three week drought I went two weeks without watering, and then started watering modestly. We have sandy loam soil. I have some mulch around the tree which does not cover width of its canopy, in effort to help hold soil moisture; our soil does not hold moisture well.

My goal is not grow the perfect peach this year. My goal is to harvest good edible peaches this year and to try to grow a tree that is not so depleted so that it will get fruit next year.

I wouldn;t be scared to water. I'd rather have a strong return bloom then maybe have some sweeter peaches. We have enough issues with climate, bugs and disease then to worry about brix levels.

Yes, once trees are well plugged in and of the size you want to maintain them you can perhaps worry about getting best possible fruit. At first, anything you pick off your own trees is completely wonderful and a little more sugar
could not make you any happier.

The only reason I'm interested in getting more sugar in one particular peach is that it's quality has dropped off so much that the beautiful fruit is almost tasteless- and it's a Red Haven. I can't even give away the fruit- not that no one would take it, but because I'm just too ashamed!

Fruitnut: how do you prepare peach fruit samples for determining brix? Do you do your fruit all individually or composite 1+ peaches and then prepare for brix determination? I was involved in vegetable crop research for many years and understand the importance of proper sample preparation, garbage in, garbage out.

Oh BTW, I'm not interested in publishing papers in refereed journals, just getting a handle on brix as are you.

Thanks for your input on the subject.

FWIW, I judge when to water currently by taking a few soil cores from around the tree drip lines and checking the cores. The method has worked very well predicting when the trees are about to begin dropping leaves, that's when I irrigate. Wonder if anyone uses irrometers or gypsum blocks to monitor soil water status. Irrometers could be darned handy but my budget doesn't have room for any more extravagant spending on exotic horticultural supplies :) Surely there has been research done on the relationship between soil moisture status and brix in peach (and apple).

Just got a brix refractometer and the first fruit was ready to pick yesterday, let the harvest begin!

michael:

I do individual fruit except on small fruit where a composite sample gives more representative results. On the bigger fruit just slice off a thin section and squeeze juice onto the lens. Close the lid asap or evaporation will affect the result.

I used irrometers some but as I remember they are only useful in the wet end of soil water. Haven't used gypsum blocks. Mostly we took soil cores and some neutron tube. Leaf water potential would be useful but is too much trouble.

In the greenhouse I've got the schedule down for in-ground trees. That would be ~7 inches at the beginning of dormant season to leach salts and replenish the subsoil. Then as follows:

March 1.0 inch
April 2.0 inch
May-Sept 3.0 inch/month
Oct 2.0 inch
Total 27 inches

This for a nine month growing season. Average 0.10 inch per day. Not much water. I do have a weed barrier down so all water use is by the trees, not ground cover.

Let us know how your refractometer works.

My peach are fall od the trees how much water do they need day by day Helen Keeton