how to swale a sloping olive grove

Hi, I'm a little new so forgive me if this is obvious. I'm working a piece of Land in portugal and have inherited a sloping olive and mixed fruit orchard, with heavy clay soil. Summer temperatures can reach 40 here, and water is scarce so I figured swaling was essential. But is the abundance of water created going to be bad for the olives or will they only take what they need? And how can I compensate for the heavy clay soil.....?
Any tips appreciated!

How much rain does the area get at one time?  If it isn't a flooding amount with water that stands a long time, it may be fine.

Is the soil usually left bare between the trees, or do you use any kind of cover crop?  Something suitable for the area, temperatures, soil and any water limitations, preferably a perennial or an annual that reseeds well could be a good idea.

Are you new to that area?  What to the other farms do?

A good soil test may suggest some changes to make, as long as they wouldn't interfere with the olives and fruit currently growing there.  Some forms of calcium may help open the soil to drainage without raising the pH.

One soil laboratory here in the U.S. accepts soil samples from all over the world.  They only sell information, not products, so they wouldn't be tipping the results to get you to buy their soil amendments, as many others do.

Kinsey Agricultural Services, http://kinseyag.com/Contact.htm

Sue

Hi Sue, and thanks for the good advice. Yes, I am new to the area, being British, but quickly learning as I go. The other farms are pretty traditional, and tend to simply grow olives with no cover crops other than wild native grass. I was thinking something like red clover could work well for me - what do you think?

Also it rains quite a bit at this time of year, and then stops entirely until autumn. But the rains are apparently lessening every year, and being on a steep hill our olive groves must have the water quickly run off them.

The other thing is that, up and till now, the olives have been drip irrigated - for about 15 minutes every evening. So the other reason I wanted to swale is to do away with this irrigation and let the trees fend for themselves...

Good tip with the soil analysis. I think I will do also that because the information is bound to be useful...

Can you include a pic?

My impression is that olives need it to be dry - so if you make it wet, you could kill the tree.

I think I would focus on some ponds in the area to increase general humidity (and, thus, morning dew). 

I wonder why they do a drip irrigation in the evening and not in the morning?  Oh well - you are right - that really should go. 

I think the first thing to do is to study the tree.  And if the trees have been spoiled on water, you might need to wean them off of the water for a while. 

Rather than build your swales of earth, you might just stake out pruned branches and add some mulch upslope.  If you decide to dig later, piling spoil on top of the wood won't hurt anything.

I was wondering if you had considered coppicing.  A family friend had good success with coppiced olives.  The link below says it can rejuvenate old trees and reduces alternate bearing, and that it isn't as tricky as traditional pruning methods.  I kind of wonder why whole sections were coppiced at the same time, though.

http://books.google.com/books?id=ao6oF5eJDAAC&pg=PA121&lpg=PA121

If a few old trees aren't producing, and you decide to coppice them, you might consider planting broom in the clearings, and maybe along the logs or swales.  It will put down taproots, fix nitrogen, and provide lots of seeds that I understand chickens enjoy.  And as the olive suckers come up, the broom will not like the shade.  Apparently they acidify the soil, though, which I hear olives don't appreciate...your new neighbors will probably know more about the local variet(y/ies) of broom.

As polyparadigm alludes to, you can obtain swaleing effects without digging a conventional -- sometimes all too permanent -- swale.  A swale, then, can be anything that slows the flow of water down a slope and lets it sink underground.  For instance, ripping a line through, or laying hay bales or mulch grass along, a contour can be a temporary swale.  Check out this quote from Garden Len, a frequent Australian poster on the Garden Web Permaculture board.  This is from his terrific website:
http://www.lensgarden.com.au/permaculture_essay.htm

"If you live in heavy clay soil areas you need to be aware that once clay saturates, water no longer penetrates it. Just ask the blokes who build dams.  They need a clay (be it reactive volcanic clay or non-reactive sandstone clay) for the bottom of the dam so that the dam will hold water. Yes I know the designists say to mulch along the swale trench and in time this will make the clay more permeable to soaking in water.  How much time?  Well, that is the big question.  If you are so locked into the comfort zone of constructing this type of swale, and you are in clay soil, then might I suggest a good dose of gypsum (no limit to how much can be used really, buy the good quality stuff, that is determined this way, the more like talcum powder it looks the better the quality).  [Place it] along the bare swale surface and over the berm before laying the mulch. This can have the effect of spreading up the amending process. To go one step further maybes consider cutting a rip along the bottom of the swale, after all you are trying to get water down into the sub-soil..."

That essay was pretty good.  I enjoy a nice rant. 

I completely disagree with him on the topic of strawbale, rammed earth, and other types of construction.  Does mining iron damage the earth less than digging up some dirt for cob or adobe?

Overall, it could use a proof-reading.

paul wheaton wrote:My impression is that olives need it to be dry - so if you make it wet, you could kill the tree.

Olives tolerate dry but I've had one survive two winters outside here on Skye where it is anything but dry!