Soil Moisture Terms

In the last article we focused on soil moisture and how it is stored in the soil; adhesion, cohesion and capillarity. But how does this relate to the terms: saturation, field capacity and permanent wilting point?

When soil moisture is stored in the soil it is possible to measure both the amount (content V%) and the tension. The soil tension forms the basis of the following soil moisture parameters: saturation, field capacity and permanent wilting point.

Saturation

A soil is saturated when all pores (micro and macro) are filled with water and no air remains in the soil. At saturation there is free water in the soil profile. Gravity will cause water to drain from macro pores and saturation is therefore a temporary state.

Figure 1: Example of a soil reaching saturation point and the subsequent drainage period. 

This is how it appears on AquaCheck soil moisture plots. 

Field Capacity

When a soil is at field capacity, water is held by adhesion to soil particles and capillarity in micro pores. Field capacity is reached when rapid drainage decreases (Figure 1).

On your Vantage NZ soil moisture plots the field capacity is determined for each sensor depth, then summed to determine the l field capacity for the active root zone. This allows for soil texture changes throughout the profile and provides you with a field capacity unique to the sensor site.

Permanent Wilting Point

Evapotranspiration and drainage (to a much lesser extent) will cause the soil to dry below field capacity. During this process water is removed from all but the smallest micro pores. The permanent wilting point (PWP) varies depending on plant conditions, plant type and soil texture (Figure 2). Nevertheless, the soil water potential at which permanent wilting occurs is considered to be 1500 cba.

Figure 2: Illustration of saturation, field capacity and permanent wilting point for three different soil types. 

Available Water 

Available water (AW) is the amount of water held in the soil between field capacity and wilting point for a defined depth of soil and is expressed as V% or millimetres (mm). 

AW = FC - PWP

Readily Available Water

Not all the available water is equally (readily) available to plants. Water becomes more difficult for plants to extract the closer the water potential comes to permanent wilting point. This is because the reminding water is bound to the soil at increased tension.

Plants need to take up enough water to satisfy their transpirational demand and sustain optimum growth rates. For every kilogram of dry matter (DM) produced, a plant must transpire between 200 – 500 litres of water.[1] For plants to obtain this quantity of water from the soil, water needs to be readily available. Water is said to be readily available when plant growth is not restricted by water availability. Stress point is the point at which plants can no longer extract water at potential rates. On a soil moisture plot this will be demonstrated by a change in water use, i.e. a change in slope of the soil moisture trace (Figure 3).

Figure 3: A change in slope indicates a change in water use. This is how it appears on AquaCheck soil moisture plots. 

As water below the stress point is not readily available and not sufficient to meet potential daily plant demands, yield is lost. Water between the stress point and permanent wilting point is available to plants, but growth is adversely affected.

The key soil moisture parameters described above are essential in irrigation management. At Vantage NZ we strive to clearly determine and label these on your soil moisture plots (Figure 4) so you can make good irrigation management decisions. 

Figure 4: AquaCheck soil moisture plots clear labelling of key soil moisture parameters. 

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[1] McLaren, R.G. and Cameron, K. C. (2000). ‘Soil Science’, Sustainable production and environmental protection. Second edition, Oxford University Press. Page 99.

So, What is Soil Moisture

 

I recently heard a gardening segment on a NZ radio station. The gardening commentator was answering questions and providing advice on ‘how to irrigate your garden’. Her advice was: “Deep watering will encourage the roots to grow into the water table below. This is desirable as it allows the plants to be self-sufficient in accessing water.”

We all have our own perception of water and how it is stored in the soil, but the gardening commentator’s description isn’t an accurate description of what actually happens within the soil or what we are aiming to achieve through irrigation.

There are several processes at play when water is “stored” in the soil: 

·        cohesion - the attraction of water molecules (H₂O) to one another it causes water molecules to stick to one another and form water droplets;

·        adhesion – the attraction between water molecules and solid surfaces, in this case soil particles;

·        surface tension – as a result of the cohesive properties of water molecules and their attraction to other water molecules, a water surface behaves like an expandable film; and

·        capillarity – is a combination of cohesion/adhesion and surface tension forces and is the primary force that enables the soil to retain water and to regulate its movement.

In this article we will take a closer look at these terms and and apply the concepts to soil moisture storage.

To demonstrate or understand adhesion and cohesion, pick up a rock or stone, dip it into a pool of water, pull it out again. The water dripping off the rock is free water (lost to gravity, same as free water will be lost to drainage when soil is at saturation point). If you give the rock a shake you will free it of more water - this is the water “stored” by cohesion. The rock is still wet even after the shaking - the water left on the rock is “stored” by adhesion (Figure 1). Water is stored in this way on all soil particle surfaces, whether it be a clay, silt, sand or gravel particle.

Figure 1: Soil moisture is stored on soil particles like a film via adhesion. On this stone adhesion is demonstrated by dipping it into water solution containing blue dye.

Capillarity is the key to storage of water in the soil. It allows water to move upward (and through) soil pores against the force of gravity. The finer-textured the soil (silts and clays) the greater the ability to hold and retain water in the soil in the spaces between particles. The pores between small silt (less than 0.02mm diameter) and tiny clay (less than 0.002mm diameter) particles are known as micropores. Compare these to the larger pore spacing between larger particles, such as sand (0.2-2mm) and stones (larger than 2mm) which are called macropores. Micropores enable greater capillarity rise.

Capillarity can also be simply demonstrated by placing a dry sponge into water – it will progressively wet upwards through the sponge (Figure 2). The finer the sponge material the higher the water will wet the sponge.

Figure 2: Fine sponge placed into a dish with water solution containing blue dye demonstrating capillarity.

When we irrigate, we want the water to have the opportunity for adhesion and capillarity to take place; i.e. “coat” the soil particle surfaces with water and be retained in the micro pores by capillarity this is best achieved through low application rates and by matching the applied depth to soil moisture deficit.

Back to the garden commentator’s recommendation to practice deep watering and aim to push roots into a water table. Very few farmers/growers/irrigators will have a water table shallow enough for roots to reach the water table. When roots explore the soil profile, they form perfect contact with soil particles, via this contact they can extract the moisture stored on particle surfaces. Deep watering is accurate to an extent. We want roots to explore as much soil as possible as this allows them to access more water and nutrients. Roots will only grow in moist soil, so they’ll only explore the soil profile if it’s been wetted. However, it is unusual for the subsoil not to be moist enough for root growth as the plant advances through its growth stages. Irrigation should therefore only be aimed at wetting the soil within the active root zone.

Aquacheck sensors measure soil moisture at several depths. This depth profile is a very useful tool in managing your irrigation. It allows you to see if you are wetting the active root zone and whether the subsoil is wet enough to allow for root growth.

Jane Robb 

Vantage NZ Customer Support Specialist

"Action for Healthy Waterways" - What you need to know

Last year, the Government released its Action for Healthy Waterways discussion document. It outlined the much-anticipated proposed changes to our national freshwater management framework.  The discussion document resulted in over 12,000 submissions being received for consideration by a government appointed expert panel. 

The recommendations by the expert panel, and approved by Cabinet, were released at the end of May.  These are essentially a suite of broad policies.  They are final and therefore, no further opportunity exists to have input on them.  It would be fair to say that the recommendations overall result is a much more balanced, practical suite of changes, but there is still a lot of detail to come, as discussed later, and the odd quirk that wasn’t expected. 

The broad policies are as follows:

• Councils will be able to maintain water quality attributes below the national bottom line to “secure the benefits” of the existing structures in the Waikato, Tongariro, Waitaki, Manapouri, and Clutha hydro schemes.
• Limits will be defined and how they are to be expressed in planning documents.
• Water quantity limits must be linked to ecosystem health outcomes.
• Territorial authorities will be required to manage effects of urban land development on freshwater bodies and coastal marine environment.
• Clarification of what Te Mana o Te Wai means and how it is to be implemented, both nationally and regionally.
• Councils will be required to actively involve tangata whenua in council processes for policy and plan development and decision-making.
• Regional council policies and plans must include mahinga kai as a value.
• Amendments to ensure regional authorities manage all aspects of ecosystem health (not just water quality and quantity).
• New attributes with national bottom lines:
• Macroinvertebrates
• Submerged plants in lakes
• Dissolved oxygen
• Suspended sediment
• Deposited sediment
• E. coli at swimming sites during the bathing season
• New attributes without national bottom lines:
• Fish species
• Ecosystem metabolism
• Dissolved reactive phosphorous
• Existing national bottom lines for nitrate and ammonia toxicity attributes will be strengthened to protect 95% of species from toxic effects. Exceptions to this will be allowed in specific areas of the Pukekohe and Lake Horowhenua catchments, due to contribution to national food security (vegetable production).
• From mid-2020, technical standards, methods, and requirements for activities affecting streams and wetlands will be prescribed. This will include vegetation clearance, earthworks (including for drainage), and changes to water levels. Includes surrounding vicinity. Resource consents will be required for most of these activities.
• From mid-2020, minimum design standards for new weirs and culverts to provide for fish passage. Passive flap gates will be a non-complying activity. Regional councils will be required to gain information on current structures and adopt work programmes to address barriers to fish migration.
• Until 31 December 2024, resource consents will be required for:
• land-use change of more than 10 hectares to dairy
• land-use change of more than 10 hectares from woody vegetation or forestry to pastoral farming
• increases in irrigated pasture for dairy farming above 10 hectares
• increase in winter forage cropping area above annual highest 2014/15 – 2018/19
• increase in dairy support activities above highest annual 2014/15 – 2018/19
• From July 2021, there will be a national maximum of synthetic nitrogen fertilizer application of 190kg of nitrogen per hectare per year for dairy, dairy support, sheep, beef, deer farming. Dairy farmers must report applied amount to councils.
• From winter 2021, if you are winter grazing on areas that exceed the following thresholds, you will be require a resource consent:
• less than 50 hectares or 10% of property area (whichever is larger) is used for winter grazing
• minimum setback of five metres from waterways
• average slope of paddock 10 degrees or less
• Farm plans will be required for:
• pastoral farming totalling 20 hectares or more
• arable farming totalling 20 hectares or more
• horticulture totalling 5 hectares or more
• an agricultural purpose prescribed in the regulations (not yet determined)
• any combination of the above uses totalling 20 hectares or more.
• Water users with consents to take water over 5 litres per second will be required to measure water use every 15 minutes and provide electronic records to councils daily.

One thing that is notably missing is the national bottom lines for Dissolved Inorganic Nitrogen (DIN).  This was proposed to be a limit of 1 mg/L and caused a huge amount of debate.  It has been kicked for touch and the need for a DIN limit will be reassessed in the future.  Also kicked for touch is water allocation and iwi rights and interests.  This is not a surprise – a complex, fraught debate that no government to date has had the balls to address. 

The nitrogen fertiliser cap was one of the quirks.  What they are hoping to achieve with this, I am not sure.  You can reduce its use, but to make up the feed shortfall, supplementary feed is used, which is a form of imported nitrogen, so you reduce nitrogen in fertiliser only to replace it in imported feed.  Very non-sensical.

So, what happens next?  Some of the specific regulations are still to be drafted.  This includes the National Policy Statement for Freshwater Management and National Environmental Standards.  Councils must give effect to these new documents by 31 December 2024.  It is indicated that there will be consultation with stakeholder groups (for instance in relation to the requirements for mandatory farm plans with freshwater modules), but the regulations are due to be presented to Cabinet for consideration in July, so there is not a lot of time.  As if often the case, the devil can be in the detail, so there may still be some sting in the tail in the drafting of the regulations.  

Watch this space. 

Keri Johnston - Irricon Resource Solutions

Now Find H2Grow on Social

As Albert Einstein once said, “Life is like riding a bicycle, to keep your balance, you must keep moving.” 

With that in mind the H2Grow team have reflected on how we initiate conversations and share knowledge, and have decided to extend our presence to social media where so many meaningful conversations are being had by food and fibre producers and consumers. 

So come and join us on Facebook and Instagram, search for @H2Grow.NZ - we look forward to seeing you soon!

Note we will still also be posting longer, more in-depth information on our blog, and available for workshops and field days at request. Just click on the email links to any of the team if you would like to know more. 

Keri, Jemma and Sarah

Maximising the Value of Irrigation

The H2Grow Team are excited to introduce Carolyn Hedley as our guest contributor, it is with great pleasure that we can share with you her valuable expertise. Carolyn is a Soil Scientist with Manaaki Whenua, based in Palmerston North, and lives on a small Kairanga farm with husband, Mike. Carolyn has combined her interests in soil science, proximal soil sensing and precision agriculture with on-farm studies of precision irrigation and soil carbon mapping. She has led several nationally funded projects in irrigation and soil carbon, including current leadership of the MBIE funded programme “Maximising the Value of Irrigation”.

Maximising the Value of Irrigation  -  Carolyn Hedley

Early in the new millennium I found out about EM mapping and in 2004 published a method in the Australian Journal of Soil Research to rapidly EM map soil variability on a basis of soil texture. I realised that EM mapping was a really useful new technology to rapidly survey soil variability. The EM map had picked the difference between a Kairanga silt loam and a Kairanga clay loam, and this had management implications for the farmer because the heavier textured soil would compact sooner when grazed in wet conditions.

I could see great potential in this new technology and so embarked on a PhD in proximal soil sensing and this is when I started to relate the EM map to soil available water holding capacity and realised how useful this could be for irrigation scheduling. But critics commented that irrigation systems cannot irrigate to such a complex pattern (example shown in Figure 1 below). Enter Stu Bradbury and George Ricketts, who had worked with me on some EM mapping projects when they were students at Massey University. There was an engineering solution to this problem – control the sprinkler system on a pivot to irrigate to any pattern – which led to the development of the Precision VRI system. Precision VRI, the world’s first true variable rate irrigation system, turned the heads of the global irrigation giants and as a result Lindsay Corporation acquired the technology development company founded by Stu and George.

Figure 1: Available Water-holding Capacity map derived from an EM map for a 100-ha area irrigated by a VRI linear move irrigation system

There was still work to be done though and a proposal put to the Ministry for Business Innovation and Employment received six years funding in 2013 to further research methods to improve management of irrigated land. Now in its final year, the “Maximising the Value of Irrigation” programme has been able to refine methods to use proximal sensor data to create prescription maps for precision irrigation. It has developed soil and crop sensing methods that can inform in near real time the prescription map, and a prototype scheduling tool has been tested with participating farmers as a smart phone app. The in-field sensor monitoring methods have been used to support Lindsay further refine the software control features for the Precision VRI system, which is remotely managed through the FieldNET platform.

Ekanayake, J. and Hedley, C. (2018) Advances in Information Provision from Wireless Sensor Networks for Irrigated Crops. Wireless Sensor Network, 10, 71-92. 

Research into different soil management methods has identified correct tillage and soil surface management methods to store more water in the soil and reduce irrigation requirement and water losses. A spatial framework to run the APSIM model has been created to test the effect of different irrigation scenarios on yield, drainage and water use efficiency. Spatial-APSIM simultaneously runs the model for up to 1,400 grid cells for one irrigation system to compare results of different irrigation scenarios at spatial resolution < 50 m, over several decades.

The MBIE Programme “Maximising the Value of Irrigation” is now working closely with its industry advisory group to ensure that its findings are communicated effectively and to find ways to integrate new tools and support improved management of irrigated land in New Zealand.

Harvest 2019 is Upon Us!

Do you have yield mapping capabilities?

Are you storing your data in a secure location?

If your combine harvester is capable of yield mapping, do you use it? Yield map data is a powerful tool for making decisions on your farm. It is a record of how your crops reacted and performed under that season’s constraints. Constraints and variation may be apparent in your crops nutrient levels or application methods, or available water in the profile at critical times in the plant’s life cycle,and in most cases a combination of all the above!

I’ve been to many agronomy seminars where they always reiterate that when you sow your crop it starts at its maximum yield potential and everything from that point on reduces that potential. So, your yield data is a map of how well the crop has performed under that season’s conditions and how much variability there is in the soil profile within a paddock. Many arable farmers have paid for the technology but aren’t able to harness the power of the information that it provides. Agri Optics NZ are here to help with this.

Yield monitoring in any combine

One thing that isn’t stressed enough to growers with yield monitors is that they should capture the data regardless of whether they are able to use it at present or not. As having multiple years’ worth of data is far more useful than one year of data. The more years’ worth of data you have lessens the influence of a single seasons weather pattern or any out of the ordinary extremes. For example, in a wet year the lighter freer draining soils may be preferable for a higher yield and visa versa in a dry season. This process of compiling several years of data is called normalisation. Data is put into a relative scale and is compared across the years. Once data is normalised then we can identify common zones or production areas. These zones can be marked for future management decisions.

The difference between raw and processed data

Processing or “cleaning” the data is the key to successfully utilising the captured data. Raw yield points have a large amount of errors and “noise” that can significantly impact on the results. With these noisy bits removed and tidied up the data becomes more representative of the paddock. Some of the factors that impact on the data accuracy are cut width, flow delay and travel distance errors.

A processed yield map

Yield data can also be useful for identifying problems during the actual harvest of the crop. In one example a grower saw the results of him harvesting grass seed in the hottest part of the day. He was able to spot the mistake as recorded yield dropped in the swaths that he completed in the hottest temperatures. Ultimately the yield information informed him that the decision had cost him.

Making useful yield maps – the essential information

1. ‘Rubbish in equals rubbish out’ – you only get one opportunity to collect this data so ‘do it once and do it right’
2. Start the season with an empty data card - save a copy of all previous data to your computer and then ‘clean’ the card
3. Naming –use the same naming for the same paddock each year as this makes finding your data easier at the end of the season
4. Check the flow and moisture sensors – if these are not working properly then everything that follows may be a waste of time
5. Calibration – at the start of harvesting each grain type calibrate the flow sensor
6. Operation setup – make sure the cutter bar width is correct, as well as the flow delay is as accurate as possible
7. Card check and back-up – confirm data is being logged by importing it into your mapping software or sending it to your Precision Ag specialist once you start for the season...not at the end of this season! Backup the data as a raw format throughout the harvest season also.
8. If you collect the data as accurately as possible in the first place, then post-processing of the data to make it a useful resource is much simpler!

Yield data is the final measure of a seasons work. Yield data allows for insights into different management practices and the old adage “what gets measured gets managed” comes to mind. 

Have a good harvest!
Chris

Celebrating 10 years of Irrigation Innovation

It’s a classic story of Kiwi innovation.

One summer’s evening in 2004, two Massey University engineering graduates, Stu Bradbury and George Ricketts were working a summer job assembling irrigators on the South Wairarapa farm of Brian and Jo Bosch. 

Over a cuppa, Stu, George and Brian discussed the challenges on the Bosch’s farm caused by the limitations of the existing pivot irrigation system.

“Where the pivot went over the races was wet and mucky,” says Brian.  “We were also getting a number of lame cows, who got wet feet and bruising on the muddy race.”

Brian Bosch on his Wairarapa dairy farm

Blanket irrigation was the problem. They needed a way of irrigating specific areas that needed it but keeping vulnerable parts such as the race dry.

Back then nothing on the market could manage the water flow in targeted and controlled quantities, to specific parts of the farm depending on topography and soil type.

“We saw wet areas where crops weren’t growing, and dry areas without much water. So there was an obvious need for a system to specify where you needed water and how much,” says Stu.

Before long George had the solution and in 2006 they began developing the prototype that would become Precision VRI. VRI stands for variable rate irrigation, ensuring precise amounts of water or nutrients are delivered over multiple crops, soil types and terrains.

To make best use of the technology on paddocks with variable soil types and terrain electromagnetic (EM) soil mapping is recommended. EM mapping measures soil conductivity which is an indicator of soil texture (along with other characteristics) and therefore soil water holding capacity. The Precision VRI system can be easily programmed using the FieldNET app to customise irrigation according to the EM map.

The system can be used to ensure that only the areas that need water, get water, and at the right levels.

Over the past decade Precision VRI has enabled New Zealand’s farmers, food producers and agricultural contractors to achieve better results, driving efficiencies and saving money – to the benefit of agribusiness, not only for dairying, but in sheep, beef, horticulture and arable farming.

In 2011 global agribusiness leader Lindsay Corporation acquired the NZ company WMC Technology Ltd under which the Precision VRI technology was developed. Through doing so the not only gained the rights to market the award-winning technology but also provided significant backing for George, Stu and the team to continue developing irrigation solutions.

From the archives: George and Stu at a farm mapping job in 2010 (above). Stu, George and Paul (below) receiving the Supreme Award at the Manawatu Business Awards 2010, WMC Technology Ltd also won the Innovation Award and the Workplace Health and Safety Award.

“We are working on new iterations of the software,” says Stu.

“Now, everything needs to be mobile-friendly so that is where our efforts are focused.”

Future plans to market the system internationally will give farmers world-wide the advantages experienced by New Zealand farmers using the system.

To find out more about the Growsmart Precision VRI system call 0800 438 627 or visit www.lindsaynz.com.

New, Improved (and now award-winning) Irrigation Remote Management

Lindsay Corporation, global leaders in the development of innovative irrigation solutions, are keeping farmers ahead of the game with the latest enhancements to their FieldNET® mobile app. Available on Apple App Store® and Google Play™, the app is now more user-friendly with improved access, visibility and control of center pivots and lateral irrigation systems. Advancements to the variable rate irrigation control functions also make managing Growsmart Precision VRI systems even easier.  

The new app has been selected as an AE50 Award winner for 2019. Presented by the American Society of Agricultural and Biological Engineers, the award recognizes the year's most innovative designs in engineering products or systems for the food and agriculture industries.

The technology offers seamless remote monitoring and control, integrating a farmer’s irrigation tools and systems. It is compatible with almost any electric pivot brand and delivers real-time information so farmers can see exactly what their systems are doing and control them quickly and easily from a smartphone, tablet or computer.

Key features and new, real-time functionalities now available via the FieldNET mobile app include:

• The ability to enable/disable auto-restart and auto-reverse

• End gun controls including aerial views

• The ability to shut down multiple pivots simultaneously

• Displays time remaining for current circle or until the next stop

• An integrated pivot and VRI control dashboard

• VRI plan previews overlaying satellite imagery

• Increased VRI plan editing options

• Live VRI system status data

“The new app delivers many new features and enhancements to FieldNET customers, several of which come in response to past customer requests,” said Reece Andrews, director of FieldNET and Zimmatic controls at Lindsay Corporation. “The new FieldNET mobile app has an extremely intuitive and fast user interface, offering an enhanced level of mobility and precision that growers won’t find with other remote irrigation management solutions.”

FieldNET is one of the most cost-effective remote irrigation management tools on the market. Lindsay’s commitment to developing innovative irrigation solutions ensures farmers can stay ahead of the game by having more timely, useful information to aid decision-making, making the most effective use of time managing their irrigation, minimising the need to visit the pivot and improving water and energy use. 

For more information about FieldNET, talk to your local Zimmatic dealer or visit www.myfieldnet.com. 

Ashburton A&P Show

Agri Optics showcased their services at the 141^st annual A&P show in Ashburton on the 26^th and 27^th October, to catch up with existing clients and field enquiries from prospective clients. Despite the torrential rain while setting up on the Thursday, the show days themselves were thankfully a great deal better. I thought I’d write a blog about the sort of questions the team were answering as a point of interest to those who weren’t able to make it.

Picture 1: Nick Evans and Lucy Murray on a muddy Friday morning after finishing set up!

The theme of this year’s show was chosen by the President David Butterick and was “Irrigation – the life blood of mid Canterbury” – this is a great fit for Agri Optics’ services and solutions. It was also the topic we fielded most enquiries about!

Picture 2 & 3: The team answering clients enquiries.

There was much interest in EM surveying and how it can be used for variable rate irrigation to make better use of water, as well as a helping make more informed decisions on where to place your moisture probes.  We had people enquire about using their EM maps and VRI to conserve water and use that water elsewhere on the farm with potentially large savings to be made by not having to buy more water shares.

Picture 4 & 5: Areas of most discussion EM surveying and AquaCheck moisture probes!

The main point of discussion however was about moisture probes; from looking at the different options available to the different telemetry types and other sensors that can be added to the systems. From weather stations to milk vat monitoring to comply with the MPI Milk Cooling legislation that came into force in June 2018.

We ran many clients through their AquaCheck graphs and explained what they were seeing, things to avoid like getting spikes going through all the profile layers and how much water to put on and where the moisture trace should be sitting at different times of the year, which was very similar to the workshops we ran a couple of months ago. If you are unsure of what your AquaCheck Web graphs are telling you then please get in touch and we can help run you through the data, or if we are in your area we are happy to come and see you to go through it all. So just get in touch as making informed decisions is of paramount importance.

We will be at the Innovation Vineyard field day in Blenheim, which is run by the Marlborough Grape Growers Cooperative on the 14^th November, the NZ Effluent expo at Mystery Creek on the 27-28 November, and at the FAR Crops event in Chertsey on 5^th December. We look forward to catching up at one of these or other events in the coming months.

Chris Smith

Agri Optics

Is your irrigator due for a service?

Regular maintenance, just like servicing your car, will help ensure your irrigation system is running at full capacity when the heat comes on. Irrigation system checks and servicing should be undertaken at scheduled times over the irrigation season (the more hours your irrigator runs for the more regularly these checks should be carried out). 

In many cases you can refer to your irrigation systems instruction manual for details on servicing and maintenance checks.

Many simple checks and servicing like lubricating joints, replacing oil in gearboxes and looking for signs of fatigue can often be carried out by farm staff. However, should you be unsure or think that you might have detected an issue don’t hesitate to contact your irrigation dealer. 

Grafton Irrigation (Zimmatic dealer based in South Canterbury) have put together a handy checklist to guide you through the checks and maintenance that will help prevent mid-season issues. The checklist covers your intake, pump shed and mainline, and pivot, hard hose, soft hose, K-line and G-set (solid set) type irrigation systems. Print yourself a copy using the link below.

Pre-Season and Maintenance Check Sheets - By Grafton Irrigation

This post has been written by Sarah Elliot from Lindsay NZ - thanks to Grafton Irrigation for your input!

Irrigation Evaluations (aka Bucket Testing) - Including tips for testing VRI systems

Spring is here but we are seeing all four seasons rolled into one some weeks which is not an anomaly. The soil moisture levels in our region have had a healthy boost in the last few days but if the media reports are true we may be in for a dry summer - please don't shoot the messenger, I'm only relaying what I have heard.

Should this transpire then that is even more reason to ensure that our irrigation systems are applying water as efficiently as possible so that we are maximising the amount of water applied that is available for plants to grow. An irrigation evaluation is a way to assess the efficiency and distribution uniformity of your irrigation system to ensure it is performing as expected.

An irrigation evaluation will help identify causes of any poor performance and (sometimes with the assistance of a qualified professional) show how these can be resolved. Increasing irrigation effectiveness and efficiency will allow you to grow more for less.

An irrigation evaluation (often referred to as a bucket test) is simple enough to carry out yourself, there are several good guides freely available to walk you through this process. For more information check out:

IrrigationNZ - Bucket Testing Resources
DairyNZ - Irrigation Evaluation Guide

The guides recommended above will walk you through how to carry out a standard bucket test however before you begin you need to consider any additional technologies that enhance your irrigation system. For instance if your system has variable rate irrigation (VRI) technology then you will need to take this into account when planning your bucket test. Lindsay NZ, the developers of the Growsmart Precision VRI system, have created a step-by-step guide that explain these additional considerations in more detail.

Growsmart Precision VRI - Bucket Testing Tip Card

If you are not in favour of the DIY irrigation evaluation option then consider contacting an accredited evaluator, this would also be recommended if your own test identifies potential issues that warrant further investigation. If you have additional technology such as a VRI system then ensure that whoever is carrying out the test is aware of this and that they carry out the recommended additional steps. If you need further help then contact your irrigation dealer, many dealers also have accredited evaluators on hand.

Irrigation system checks and maintenance should be undertaken at scheduled times over the irrigation season (the more hours your irrigator runs for the more regularly these checks should be carried out). Recommended irrigation system maintenance will be covered in more detail in the next H2Grow blog post, this will include a checklist that you can download and print off to help you with this task.

Keep an eye out for the next post or subscribe by entering your email in the box to the top right of the screen to ensure that you don't miss it!

Today's blog was written by Sarah Elliot from Lindsay NZ - I hope you have found it useful!

Key Learnings from the IrrigationNZ Study Tour to Nebraska

I was part of a 24-person group who went to Nebraska at the start of September 2018.  The tour was organised by IrrigationNZ and was an amazing opportunity to go and see how another part of the world deals with the same issues that we have here.  Below is an overview of my key learnings from the tour.  

Governance of Water

The governance of water in Nebraska is complex. There is Federal legislation, such as the

Endangered Species Act, which the state has to abide by. Alongside this there are also Federal agencies, such as the Bureau of Reclamation that control most of the surface water through storage and diversion infrastructure. The state then sets its own laws around how it will manage its water.

In Nebraska the surface water is manged at state level by the Department of Natural Resources, but groundwater is managed by Natural Resource District’s (NRD) at a local level. For a number of surface water bodies, there are also interstate pacts that determine how much water must remain in the river to reach downstream states.

The NRD’s have a Board that is democratically elected, and are often dominated by rural people including farmers. Despite this, the farmer representatives have been proactive in driving practical change among their peers.  

The NRD system in Nebraska has been very successful in managing groundwater. All takes are controlled through a well permit system that allows for a given number of hectares to be irrigated per well.

Both of the NRD’s that we visited had invested heavily in science to help them better understand their resource. They also look for solutions as both a farm and catchment level, the latter including raising capital to build environmental infrastructure such as that required for augmentation projects.  

Conjunctive Management

‘Conjunctive management’ is a recent development in Nebraska that has largely come about through the management of ground and surface water takes in ‘conjunction’ to achieve interstate pacts. This has involved the NRD’s (the managers of the groundwater) working closely with irrigation districts and the Department of Natural Resources to ensure downstream flows are achieved.

This has included restriction of individual water takes (wells) – controlling any new ones, limiting the irrigated area from existing ones and in some cases placing a seasonal limit on usage. Alongside the implementation of environmental infrastructure such as Managed Aquifer Recharge and Stream Augmentation projects.

Managing Water Quality

Nitrates in groundwater are of significant concern in the heavily irrigated districts of central Nebraska. In some areas over 50% of the land is now under irrigated crop-farming. Historic poor nutrient management (type and timing) and poor irrigation practice resulted in nitrate concentrations being frequently observed over 30ppm – well over the US drinking water standard of 10ppm.

However, in recent years there has been a significant declining trend, with relatively few areas now exceeding 20ppm. This has largely been brought about by a non-regulatory approach.

State law requires the production of water quality and quantity management plans that identify the issues and then require the development of an implementation plan to address them. All the NRD’s have a rule framework, but most of the rules are currently focused on managing water takes and farming practice reporting. Incentives, knowledge and enabling peer to peer learning in combination with environmental infrastructure is currently seen as the way forward for water quality.

The widespread move from surface flood to centre pivot irrigation has been instrumental in reducing nitrate losses to groundwater. This has enabled soils to be irrigated on an ‘as and when’ basis to minimise nitrate leaching. There is now also a push towards the more widespread adoption of fertigation, as it allows ‘as and when’ nutrient applications – significantly reducing the risk of leaching from rainfall events.

Public perception

Despite the widespread use of intensive farming methods, and the water quality and quantity challenges facing Nebraska, the one issue currently not facing farmers at the state level is pressure from the anti-farming lobby or environmental groups.

Of the almost 2 million people living in Nebraska, the majority understand the role of crop farming and ranching in providing for their social-economic well-being. The Nebraskan economy is based on the irrigation of almost 4 million hectares of corn and soy beans and this is widely understood. 

The University of Nebraska research and extension service runs an outreach programme to attract the next generation to agriculture. This currently interacts with one in every three school age children in the state, providing an agriculture ‘101’ and highlighting the exciting career opportunities that exist within it.

Keri Johnston, Irricon

Natural Resources Engineer

It's starting to get dry...

Other than this slightly cooler snap we've had over the last couple of days you'd have to say spring is well and truly here! And with these nor-west winds (in Canterbury anyway) and warmer days things are starting to dry out and there's not much rain on the horizon. The seasonal weather outlook from NIWA suggests that we're in for a dryer than average season in most places (https://www.niwa.co.nz/climate/seasonal-climate-outlook/seasonal-climate-outlook-september-november-2018) and at this point I'd have to say they're about on the money. 

The joys of being a farmer or in the ag industry is that everything you do hinges on the weather, so we get really good (for the most-part) at managing timings and inputs and reading the signs to optimise what we do on farm. Now is no different. Whether you're an irrigated farmer or a dryland one now is the time to be installing your soil moisture probes if you haven't done so already so that you can accurately measure and manage your soil moisture and timings of related inputs on farm. 

Soil moisture probes allow you to know whats going on under your feet and make accurate and timely decisions to set yourself, your farm, your crops and your livestock up to perform to the best of their ability for the coming season. Soil moisture is one of the key drivers for plant growth so it's important that we know where we're currently sitting in terms of soil moisture levels so we can react to it accordingly. Decisions around fertiliser (and other input) timings, timing and amount of irrigation, stock carrying-capacity decisions etc can all be driven by more accurate information regarding soil moisture levels. 

If you want to find out more about some of the leading soil moisture probes in the NZ market have a look here: https://bit.ly/2OyeVj1 

And if you're wanting to get some installed for the coming season please pick up the phone and give the Agri Optics team a call now before you run out of time and you're left carrying a spade in the back of your ute or ruining the tip of your good pocket knife for the upcoming summer. 

All the best for an upcoming and prosperous season ahead! 

Cheers, 

Jemma

The Irrigation, Grazing Game - Digging Deeper

Following on from last week our guest contributor Nicole Mesman digs a little deeper into the findings from her research that looked at the effect of grazing and irrigation on soil porosity.

Soil natural capital and soil health may seem like unnecessary concepts, names that you already know the meaning of without having to learn them. However I will outline them briefly and how they relate to my findings so that you are, in turn, able to relate to them if you come across them in environmental plans, legislation or elsewhere in the future.

Soils are referred to as a stock of properties or natural capital which yield a flow of valuable ecosystem goods or services into the future. Both soil health/ quality and natural capital are similar in that they use soil indicators and parameters to determine the state or function of a soil system. However soil natural capital provides a more holistic analysis of the resource as it takes into account not only the state of the soil itself (through soil indicators) but also the effect of this state on the products and services that soils provide and the human needs that are catered for by soils.

In the soil natural capital framework macroporosity is identified as the key physical attribute. This is because macroporosity determines: water flow, solute transport and drainage through soil. As a result macroporosity influences ecosystem services such as flood mitigation and filtering of nutrients. Macroporosity and associated soil physical properties provide important services and it is important for land managers to be aware of the potential to change these properties and the ecosystem services they provide.

Research has been carried out to determine the effect of land use practices on other soil physical properties such as bulk density, aggregate stability, soil carbon and water holding capacity however macroporosity remains the main indicator of soil physical natural capital and health because of its sensitivity to intensification.

My research found that on average for the 0-30 cm increment macroporosity was significantly lower on the Dairy site (9 ± 1%) than both the Sheep farm (19 ± 1%) and the Control site (15 ± 1%). This suggests that intensification is having a significant effect on the Dairy site. Furthermore on the Dairy site the 0-10 cm and 10-20 cm depth increments both have values for macroporosity < 10%. Other researchers have proposed that macroporosity values of > 10% are needed to maintain pasture production near optimum.

Target ranges for macroporosity are given in Table 1 as part of the National Soil Quality Indicator Programme. Here, for soils under pasture, macroporosity values < 8% are considered low and could restrict pasture growth. Macroporosity for the 10-20 cm depth increment on the Dairy site was 7 ± 1%, a level where less than optimum production could be expected. Results from an AgResearch trial found similar values for and changes of macroporosity with stocking intensity.

Table 1 – target values for macroporosity for pasture, cropping & horticulture and forestry

I did not find any changes in water holding capacity within the plant available range with increasing land use intensification. This result in itself was interesting as it shows that intensifying land use practices did not have a measureable impact on the readily available water (RAW, that available to plants) of the soil. In comparison other studies have found that there is a significant decrease in RAW with irrigation and increased compaction.

Finally my study did find that there was an increase in small micropores holding water at suctions too great for the plant to overcome. These findings all highlight the importance of on farm soil testing to determine the RAW of the specific soil textures and under different land uses to increase management efficiency.

Bulk density values were found to be significantly higher on the Dairy site (1.40 ± 0.02 g cm^-3) than both the Sheep farm (1.26 gcm-3± 0.02) and the Control site (1.31 ± 0.02 g cm^-3), indicating increased compaction on the DF in agreement with macroporosity values. Bulk density is not as sensitive an indicator of compaction as macroporosity and this can be seen by the large target range 0.7–1.4 gcm^-3 that has been identified for Pallic soils (Table 2). Therefore it is not recommended as an indicator for determining the effect of land use intensification on soils.

Table 2 – target ranges for bulk density are large indicating that this is not as sensitive an indicator as macroporosity for determining the effect of land use intensification on soils.

Landcare Research has developed a tool which can be used by everyone to determine the quality of their soil based on a number of indicators.

sindi.landcareresearch.co.nz

The tool allows you to measure your soil against current understanding of optimal values for: Macroporosity, bulk density, Total N, Total C, Mineraliseable N, pH and Olsen P

It will tell you about the effect each indicator has on soil quality alongside some general management practices that can be used to improve your soil.

In addition to thinking about the effect of these indicators on your soil quality I encourage you to take a step back and also think about the long term effect of the state of these indicators/ properties on your farm’s functions and the importance of each of these functions to your profitability. 

Thanks to Nicole Mesman (BSc (Hons) Soil Science) for the content of this post!