Feb 16, 2010 8:30 pm
I have always wondered why everything just grows so much better after decent rain? Plenty of googling had the standard answer is that of more nitrogen in rainwater that gives plants/trees/grass a huge kick. But is that the whole truth? I find I can water something for weeks and it kinda grows slowly but after rain, bang it's off. Friends have plants and trees that only flower after soaking spring or summer rains. Moonsonal plants I figure like up north that only kick off in the wet season. Any ideas?
Re: Rain vs irrigation2
Feb 16, 2010 11:27 pm
It is mate. Nitrates are created via lightning activity in the air. Nitrogen makes things green but we try and copy that in the wrong ways with fertiliser
Water efficiency and the effects of water application on plant health.
University of Fu Manchu 2010
It also has to do with the way water is applied. This is something even most Horts are oblivious to and something a small few in Horticulture have studied or are studying. It is something that gets serious attention from irrigation designers who are at the forefront of their trade. In fact many government water authorities and regulators don't under stand it. In the end it is the very basis for water efficiency. If this was understood we would not have irrigation shelves filled with junk that wastes water and doesn't improve plant health. We would have much more water in the dams and ground water supplies as well. Much much more.
Irrigators have also long looked at this and created a few ways of mimicking the rain.
It is a passion of mine and many others to get people to understand how to water both with a hose and with irrigation.
Firstly there is the way we water. Hold hose in one place and watch water pool. Deep watering we think it is called. Soil can never absorb water at the rate we generally apply it. Rain applys it just right more times than not
Then take a look at what you water with. I can't stand seeing people at the end of a hot day standing there with a hose fitted with junk nozzles and waving it around. Turn the view side on and you will see a massive amount of misting from water pressure. Just going to waste. This also occurs with those junk multi function spray guns people can't get enough of Not only that but watering in that way at that time of day is a waste. By the time it is dark the water will have evaporated anyway. There are very few watering products/ applicators/ nozzles that can put a slow flow of water on the soil that is soft enough not to have a negative effect. The only two I know of are made by Gardena. I'll have to dig out some pics. Overall you want a soft flow that doesn't mist or get fine sprays through small holes.
Then when you have that you must keep the water moving. Wave it around or what ever. This allows the water to be applied slowly to the soil. A little bit at a time, it will be absorbed more efficiently. Take that a step further and turn the spray upward and feel the difference in the feel of the water. It falls at the rate of gravity instead of hitting the soil at the rate of water pressure. Watch the way it hits leaves and finds more effective path ways into the soil. Most foliage captures and channels water to the base of the plant. Ever seen a huge tree in pouring rain. It can be a torrent coming down the trunk. Turn the spray how you normally use it and watch the difference in the path ways it chooses More run off. Those who understand water efficiency acknowledge that hand watering is the most inefficient way to get water to a plant. Urban myth says otherwise.
Now lets look at irrigation.
The holy grail of irrigation is the rain drop.
A waterwise irrigation nozzle/sprinkler will output a medium rain drop sized water droplet. These junk popups and even some good sprays mist too much and exposed small droplets to the air and are not effectively applying the water. The most critical effect is the rate at which it is applied by them. Not cool. The soil can not possibly absorb that rate of water and that means run off.
That means less water in the soil.
So water efficient sprayer/ sprinklers will apply water slowly with as little pressure as possible. Gear driven sprinklers are good and one is the only one I know of to meet a water efficiency standard. The rain bird gear driven popup. The MP rotators also apply water that doesn't mist at a low pressure and over a long time.
Two houses could be next to each other. Both have irrigation. One has cheap junk pop up sprinklers. One has gear drives or MP rotators. They both apply say 10mm of water to the identical lawn areas at the same start times. The one with the cheap junk popups will do that in 10mins or less. Run off occurs and stains the road.
The house with sprinklers that mimic rain better apply it over 40mins or slightly less and have minimal run off or none. The difference in turf quality will be very noticeable.
Also if you can programme many short bursts of watering rather than one long burst. So 4 10min cycles will yield better results than one 40 min cycle. I wish nurseries both wholesale and retail, irrigation controller companies and home gardeners would understand this because the positive impact on our cities water use would be significant.
Then there is the different types of rain
Short showers that are not enough to wet the soil much are enough to cleanse leaves and improve the way a leaf works.
Then short intermittent showers have little run off and water absorption by the soil is maximised.
Then light to moderate steady rain is also absorbed well by the soil. (in the short term of course), has it got tropical origins? Does it have stormy origins? Then you get nitrates.
Heavy rain. Now heavy rain will really be laden with nitrates as a result of lightning activity higher in the cloud or previous in the history of that cell. It may have been a storm 1000's of ks away or even a couple of hundred. Has the rain originated from the tropics? It would heavy with nitrates. Melted hail (when you get fat drops of rain) will most certainly have good nitrates. The soil may not absorb the water that comes down so efficiently but the nitrates in it have a benefit Nitrates make things green in a basic way.
Does that help?
Oh and have a read of these too. It was a study done on nurseries a while back by the NGIA. (Nursery and Garden Industry Association)
http://www.ngia.com.au/Story;jsessionid ... ry_id=1158
Re: Rain vs irrigation6
Feb 17, 2010 2:00 pm
Wow that's a great in depth response Fu, thanks. I have been watching the garden closely and the storm rain especially brings everything to life. Funnily enough I have spent a few bucks on hand held water guns trying to get a better water flow/spread happening. What I also wonder about is the rainwater tank I have. I assume the nitrates in the stored water would be eaten by the microbes pretty quickly but I noticed the water still has that lovely earthy smell you get from spring/summer rain. I often water the trees and garden while it's raining so the tank overflow doesn't go to waste and everything gets a few more mm's than just the rain. Do you know of any info in regards to higher nutirent levels of stored rainwater?
And the other points you raise in regards to irrigation sprinkler drop size/rates etc how does drip irrigation fit into this as it doesn't mimick water falling from the sky at all? Half the process of the water making it's way to the roots is missing, is it a case that correct sprinkler choice is better than drip sometimes?
Re: Rain vs irrigation8
Feb 17, 2010 4:00 pm
you'd be able to get a freshwater aquarium test kit if you wanted to test water in a rain guage or caught if you were keen enough
Re: Rain vs irrigation11
Feb 17, 2010 8:28 pm
Forget the bucket, it has no place in water efficiency because it has no way to deliver water at a regulated rate. Just like hand watering. Hand watering only saves a city water because no one goes out and does it much. If everyone went and hand watered, the water level in dams would plummet. It is effective when viewed over the population. When viewed on it's direct use in individual cases it is obscene.
Re: Rain vs irrigation12
Feb 17, 2010 8:41 pm
how does drip irrigation fit into this as it doesn't mimick water falling from the sky at all? Half the process of the water making it's way to the roots is missing, is it a case that correct sprinkler choice is better than drip sometimes?
It fits by applying water slowly, at low pressure, and without exposing any water to the air. It is the most efficient means of delivering water. However this is not always the best. Having the leaves cleansed of dust and grime can be of a huge benefit to the plants ability to do it's thing with producing sugars for energy. It is a catch 22 and more often than not water efficiency wins. This is why if it is a lawn, gear driven sprinklers or MP rotators that meet a waterwise standard or are certified to be water efficient are the most cost effective means to water a lawn area. Then in garden beds we suggest drip irrigation. Over East summer rains are regular enough to cleans foliage. Over here we don't get such luxuries Must be done by hand watering the foliage but is the water worth it? Well not really.
The original question was why do plants look better though so my answer is based on that.
Things like micro sprays are an abomination for use in domestic gardens and should be banned from retail sale in the opinions of many experts. They are good in glass houses or controlled environments.
Re: Rain vs irrigation13
Feb 17, 2010 8:50 pm
Interesting facts about tropical train and nitrate. We had some good rain the other day in Melb. Is it possible to measure the amount of nitrate in the rain??
it is and those sorts of tests could be carried out by water testing labs. Just have a squiz in the yellow pages for water testing. Onc could suggest some places in the world of aquaponics as well
Re: Rain vs irrigation14
Feb 17, 2010 9:04 pm
What I also wonder about is the rainwater tank I have. I assume the nitrates in the stored water would be eaten by the microbes pretty quickly but I noticed the water still has that lovely earthy smell you get from spring/summer rain.
That is because it has some very beneficial microbes in there as well. They also do wonders and the great thing is they occur in very safe numbers and they don't need to be so numerous to have a positive effect on soil health and that then creates good plant health.
Re: Rain vs irrigation15
Feb 18, 2010 8:49 pm
Thanks again Fu, I have being using rainwater mostly on the plants I want to get going eg the hedges and they seem to be sending off shoots faster. Or I could be kidding myself and it's the summer storms we have been having. There must some serious money for the person that invents the perfect chemical balanced manmade rainwater and applicator.
Should also add I bought a holman water gun with the multi modes etc and the shower setting actually mimicks the application of water from a decent watering can. Bugger all spray and it doesn't actually throw far at all you just hold it over a plant like a watering can.
Re: Rain vs irrigation16
Feb 18, 2010 11:45 pm
hmmmm I am wondering if I come over there and "he biatch man slap" you or say well done for purchasing such a contraption
If you are satisfied it matches with what I have described then right on brother
Re: Rain vs irrigation17
Feb 19, 2010 4:50 am
Soooooo, if I use stored rainwater that may or may not have nitrates left in it, but may have some good microbes, and I pump that water through a hose that has a machine-gun looking 'junk nozzle' attached (it was a present, mmmkay?), but it is set to the gentle rain mimicing setting, and I briefly upturn it to wash the leaves, and I spend the rest of the time slowly watering the dirt, then I'm doing the right thing?
Geoff - Decophile.
Re: Rain vs irrigation18
Feb 19, 2010 7:22 am
nah Fu I bought it way before reading your lecture. I only hand water or, shudder, use a ol skool metal sprinker from the tank. All town water irrigation is through drippers with a bee's apendage of hand watering. To save the threat of copping one upside the head No chance you could recommend a hose connecting sprinkler that is water wise?
Re: Rain vs irrigation19
Feb 19, 2010 12:00 pm
it is set to the gentle rain mimicing setting, and I briefly upturn it to wash the leaves, and I spend the rest of the time slowly watering the dirt, then I'm doing the right thing?
As good as can be done but I'd get a better nozzle.
Slowly water yes, but not holding it in one spot. Keep the water moving over large areas. It means you should move around a bit as well and revisit areas of the garden several times with an application of a little bit of water.
If you get a better nozzle you can do with out the upside down bizzo but try it and feel the water, you'll see what I mean
There are two types i would suggest using and both are made by Gardena. I have not found a satisfactory one other than two of theirs.
I will have to post a pic and find part numbers for them for you guys.
Re: Rain vs irrigation20
Feb 19, 2010 1:55 pm
If you get a better nozzle you can do with out the upside down bizzo but try it and feel the water, you'll see what I mean
I've done that before. At our old house, I had one Cocos in a small raised bed in the corner of the yard, kind of like a miniature version of the garden I have now. I regularly tried to mimic tropical conditions when watering that garden by holding the nozzle upside down; to me it is important to water trees this way because this is what rain does in nature. In fact I have always thought it better to water the foliage instead of the soil and letting the structure of the plant distribute the water to the ground in its own way as long as conditions allow it. If I have a good layer of mulch that is doing its job, the soil stays damp in between waters anyway.
Here's a question - should I dump a drum of Seasol into my tank?
Geoff - Decophile.
Sign in or Join to reply to this Topic
11 more posts