ANNUAL VOLUMES NEED TO BE USED JUDICIOUSLY

In an El Niño spring and summer water for irrigation is a precious commodity.  As expected irrigation started earlyish – like September - and with current predictions is likely to continue through to April.  That means irrigation will be required on a regular (aka daily) basis and will likely result in two potential issues for irrigating farmers:

a)     Groundwater users could have self-limiting bores.  This occurs when water levels drop to the point where cavitation (sucking air) occurs and/or the head required to lift water to the surface falls outside the optimum for the pump.  Both circumstances result in a reduction in L/s that can be pumped.

b)     Of greater concern is that the season is likely to be greater than the 9/10 (or 90-percentile) demand season and annual volume could be exceeded.  Therefore it is essential every effort is made to use water judiciously.

Judicious use does not include irrigating hard surfaces (aka roads).  I thought we had left the “cleaning of roads” behind – it is such an obvious waste of water and is a misdemeanour, in some cases “fineable”.  All in all not a bright use of water!

My first example is an old one and is thanks to a colleague in Hawkes Bay.  It dates back to early 2000’s, maybe 2006ish.  We have used this photo endless time to emphasise this is not the wisest use of water, and in this case a dangerous use of water.  Can you imagine riding a motorcycle and being hit by the stream of water from the high pressure gun!!  It will wash your windscreen though you could run off the road by the time you recover from the shock of the water hitting the windscreen and the wipers have been able to clear 25L/s of water.

My second example is very recent – November 2015.  No doubt the lane closest to the hedge has been well washed.  While this irrigator is less likely to result in a deluge of water on a windscreen or affect a motorcyclist as badly. It is nonetheless a waste of irrigation water.

The volume of water irrigated onto the roads is relatively small in the scheme of things.  But in a season where every drop will undoubtedly be worth $$$ in return, cleaning roads is not an effective way to make the water pay.  Quite the contrary, in both examples the water has been pumped from bores (a lost cost) and has not added any value to crop intended.

Dr Anthony Davoren, http://www.hydroservices.co.nz

My Soil Moisture Sensors Are Spot On – Yeah Right!

There is a misconception that all soil (moisture) sensors are precise and tell you the exact soil moisture content.  Not so.  HydroServices runs a trial site where a number of soil moisture sensors are installed for comparison – for both the “calibrated” soil moisture content and any long term trends.  A boring looking trial site because the sensors are installed toward the small gap in the trees.  In all there are 8 sensors – neutron probe, Decagon 5TM and GS1, Acclima, AquaCheck and two (2) Aquaflex.  The Decagon 5TM, GS1 and Acclima sensors are installed at 10cm, the shallow Aquaflex on a slope from 10-25cm, and the neutron probe and AquaCheck can measure at 15 and 10cm respectively.

Sensors are provided with a factory calibration, usually one for silt loam, clay loam and sandy loam soil types.  These are generic and may or may not truly measure the soil moisture content at your location because (for example):

a)    Your soil is unlikely to be the same as the generic soil type;

b)    The sensor is poorly installed (especially if there is not perfect contact between the sensor and the soil); and

c)    The soil is loose (cultivated) and perfect contact is not possible

While the traces of soil moisture content are sort of similar, none (with their generic calibration) read the same soil moisture content, as shown in the plot of all sensors.  (Note the GS1 Sensor is a recent addition and no data is available for the dates compared).

The only sensor that has been calibrated against true soil moisture content (gravimetric laboratory analysis) is the neutron probe.  Knowing that Field Capacity at this location and soil type should be about 40%; only the neutron probe and Aquaflex measure soil moisture content at this level.  The other three sensors measure field capacity 10% less than the true field capacity. Disconcertedly two sensors measure soil moisture content between irrigation events (the vertical rise in the traces) at or very close to wilting point – approximately 17-18%.  This is not the case; the pasture never died nor showed any sign of being close to wilting point.

What is to be taken home from the comparison?  If you want sensible and realistic soil moisture measurements the sensors must be field calibrated.  The simplest and easiest way to field calibrate is by neutron probe – click on http://www.hydroservices.co.nz/index.php?option=com_content&view=featured&Itemid=308 for more details.

Good Old Spring Weather

In the past seven days we have had a bit of everything, 10 to 29 degree days, 100km per hour NW winds, rain through to hail and bitterly cold southerly winds reminding us that spring is upon us!

Whilst forecasters don’t always get the rainfall amounts correct, they are pretty accurate when it comes to predicting strong winds.  After the wind on Sunday, it only took two minutes after leaving home to see some damage caused by the strong NW winds.

With a long dry irrigation season predicted, a broken irrigator can take a long time to fix leading to reduced yields in crops and lost dry matter in pastures. This can be avoided by having a simple plan in place for windy conditions, whether it be securing pivots to a heavy roller or parking a Rotorainer in a sheltered position on the farm.

Rainfall

Measuring and recording rainfall through the season is also key, rain gauges are cheap and may help save valuable water, especially in the shoulder seasons.  Turning irrigators off for a couple of days here and there may not seem like it making a big difference at the time, but those days all count at the end of the season if water allocations are getting tight.

Weather forecasts

The forecasters are predicting cold and wet weather on Tuesday this week, perhaps an opportunity to save a round or two with the pivot if they are correct.

http://www.yr.no/place/New_Zealand/Canterbury/Ashburton/

Happy Irrigating!

Mark Fitzgibbon

Hydroservices

WHO SAID IRRIGATING WAS EASY?

Being an Irrigating Farmer has many benefits with increased land value and production to less reliance on rainfall events being at the top of the list.

But with these benefits comes responsibilities and duties to ensure success at being an irrigating farmer.  So, what is involved?

1. Regular System Maintenance

1.       Irrigation System checks should be undertaken pre-season and at least twice over the irrigation season.  This involves doing pressure tests, checking sprinklers and nozzles, cleaning out filters, checking and fixing leaks.  Click on the link below for checklists and guides.

http://irrigationnz.co.nz/news-resources/irrigation-resources/irrigation-system-checklist/

2. Irrigation Evalulations

Irrigation Systems need to be evaluated much like getting a vehicle Warrant of Fitness.  Evaluating your system allows you to check that it is working to the design specifications and performing as you would expect.  High distribution uniformity (how evenly the system applies water) is the key to achieving an efficient and effective irrigation system.  

Ideally, irrigation systems should be ‘farmer’ evaluated annually using the ‘Irrig8lite’ guide - http://www.pagebloomer.co.nz/resources/irrigation-calibration/irrig8lite/.  

Should your system show low performance, a full system evaluation should be undertaken by a qualified evaluator: http://www.hydroservices.co.nz/index.php?option=com_content&view=featured&Itemid=271.

3. Measuring Soil Moisture

Measuring your soil moisture is the BEST way to manage and schedule your irrigation efficiently.  If you don’t know what your soil moisture content is, it is likely you are either under irrigating or over irrigating which can be detrimental to your crop and/or the environment.  There are a number of options when it comes to measuring soil moisture whether it be an on farm service or telemetered continuous soil moisture sensors.  

Find out more at: http://www.hydroservices.co.nz/index.php?option=com_content&view=featured&Itemid=268.

The Irrigation Season has already arrived for some and is fast approaching for others.  If you haven’t completed your pre-season system maintenance checks already, now is the time to do it!