Sustainable Irrigation Field Day - North Otago

We would like to invite you to attend a field day at The Mitchell Webster Group’s dairy farm on Wednesday the 18^th of March. The Mitchell Webster Group are well known for their forward thinking and sustainable farming practices, which they were recognised for in 2013 winning the Ballance Farm Environmental Supreme Award for the Otago region.

On Wednesday the 18^th we will be focusing on the technologies and practices employed that help ensure efficient and sustainable irrigation on their properties. The field day is applicable for dairy, cropping and sheep and beef farmers. Topics covered will include:

        -   Efficient irrigation technologies and management practices
       -   Variable rate irrigation
       -   Soil moisture sensing
       -   Electromagnetic (EM) mapping
  -   Economic and environmental benefits
  -   Sustainable Farming Fund - Hill Country Irrigation project findings
  -   Environmental considerations and requirements for Irrigators

Where: Mitchell Webster Group Dairy Farm

190 Coalpit Road, Enfield, Oamaru

Fonterra #36174

When: Wednesday 18^th March at 12:15

There will be a BBQ lunch kindly provided by ANZ.

Everyone is welcome, so we look forward to seeing you there.

If you have any questions please contact Sarah Elliot from Lindsay NZ on 021 811 266.

The Irrigation, Grazing Game - In more depth

This time, a little bit more juice from my research. 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. 

Blog post by Nicole Mesman - BSc (Hons) Soil Science

The Irrigation, Grazing Game

In this week’s H2Grow blog post we are pleased to introduce our first guest contributor - Nicole Mesman.

My name is Nicole Mesman and last year, since finishing my honours in soil science at Lincoln University, I have been working for Lindsay NZ to review the benefits that farmers are receiving from their Growsmart Precision VRI systems. My honours project looked at the effect of grazing and irrigation on soil porosity. While university projects are often published in journal articles I feel like research can sometimes take a long time to make its way to our farmers and end users, those who we are trying to help with this research in the first place. I am very happy that I am able to explain my findings to an audience that might be able to make use of this information.

I wanted to find out what, if any, effect irrigation was having on soil porosity and water holding capacity. From both my findings and the research of others I was able to suggest that a combination of irrigation and cattle grazing led to a decrease in soil macroporosity and those micropores holding water in the range readily available to plants. Also that there is an increase in very small micropores storing water that plants are unable to access.

Macropores are the largest pores, they don’t store water for the plant but provide aeration for the soil, space for root growth and allow water to infiltrate through them to the small micropores that the plant draws water from. Reduction in macropores can result in decreased root and plant growth and an increase in waterlogging and surface run-off as water is unable to infiltrate into the soil and instead pools and runs off the surface.

Macropores allow water to pass quickly through them and are occupied with air unless the soil is waterlogged. Micropores store water for plants to access, some micropores are so small that plants are unable to draw water out of them.

The result of a decrease in micropores is less water held between field capacity and refill point; readily available water for plants. In order to ensure plants have optimum water available to them irrigation volumes should be decreased but made more frequent to ensure neither overwatering or water stress is occurring. Once compaction of soil and decrease of microporosity has occurred it is easier for damage to continue. Soils take longer to dry out after irrigation and subsequent grazing events are more likely to damage the soil again.

When a soil becomes compacted under a combination of irrigation and grazing events the available water decreases as soil particles are compressed together. This means there is less water available to the plant and irrigation volumes should decrease while frequency increases to maintain water content.

If you think you may be seeing the negative effects of decreased macroporosity and microporosity on your property then there are steps you can take to avoid further damage:

• Soil moisture sensors that are calibrated for your soil type allow you to identify when your different soils require irrigating and mean that you can change your irrigation volumes according to your field capacity. Reduction in micropores may mean that soils retain a higher moisture content for longer and are more susceptible to further damage when grazed. Moisture sensors will also allow you to monitor areas that have been irrigated and determine when moisture content has decreased below field capacity and stock could be moved back to graze the area, avoiding further damage to soil structure. 
• Decreased macroporosity can be countered by leaving a paddock under pasture, allowing roots and organic matter additions to create structure while using variable rate technology to adapt your irrigation. Irrigation can be altered to avoid areas where decreased macroporosity has resulted in ponding, this can help the area dry out and encourage grass growth.

That’s all for now but please watch this space for my next post where I will tell you about the specifics of my trial, quantify the changes in macroporosity and microporosity that myself and others have measured, explain the role of these properties in soil quality and natural capital and how their importance in this system can be assessed.  

Blog post by Nicole Mesman - BSc (Hons) Soil Science

Tools For Growing Farm Profitability

Today I’m taking writer’s liberty and changing tack slightly. While we’ve been talking about variability and how to manage it and irrigation efficiency I’m going to share some insights from the knowledgeable Jim Wilson of Soil Essentials in the UK who is currently out in NZ sharing his almost 20 years of Precision Agriculture (PA) insights from the other side of the world with us.

This morning the Foundation for Arable Research held a field day at Craige Mackenzie’s place near Methven to talk about ‘Practical use of Precision Agriculture: A global perspective’. One of the main questions from farmers this morning was “where do I start with PA?”. While there are many different places that someone can start their PA journey depending on what they’re most interested in and where they see the most benefit the moral of the story today was to start where you’d see the most benefit or return from your investment. If the biggest expense to your business is fixed costs (eg labour, diesel etc for planting etc) then GPS and Autosteer is the likely starting point for you. If your biggest cost is your fertiliser bill then, grid sampling and variable rate fertiliser is likely the best starting point for you and if the cost of water and irrigation one of the biggest costs to your business, then EM Surveying and variable rate irrigation are likely your starting point. The key is to know your business and where your biggest & fastest gains can be made from utilising these PA techniques. Precision Ag at the end of the day is about fully utilising all of these tools and technologies to MAXIMISE ON FARM PROFITABILITY.

Jim Wilson & Craige Mackenzie up the Mt Hutt skifield access road

 assessing the variability over the Canterbury Plains.

Another key theme that came from today was the use of yield mapping. While Jim said that adoption of yield mapping is still growing with his customers and in the UK in general, he emphasised that it was one of the most important layers of information on a cropping farm to help identify and quantify areas of yield variability and what that variability is. He said it was also a really important layer particularly for Scottish farmers (as you could imagine) they don’t like to spend money where it doesn't make them any. The yield maps enable them to identify areas of interest and manage them accordingly.

Jim Wilson talking at FAR’s field day on Precision Agriculture with soil variability

 and topography variability in the background.

Other PA techniques that are used widely in Jim’s area of the world are grid soil sampling and variable rate seeding. Grid soil sampling is where a soil core is taken in a uniform fashion across a paddock at either 4 samples per hectare for pH or 1 sample per hectare for phosphorus, potassisum  magnesium,  calcium & sulphur. This allows them to then variable rate apply fertiliser based on these soil test results.  Variable rate lime application based on pH test results is very common in the UK and has a significant return on investment, usually resulting in savings of lime of approximately 50%. Variable rate seeding on the other hand is where the seeding rate is varied according to soil type and the soil’s yield potential. Heavier soil typically gets a higher seed rate than lighter soil where less seeds are planted to allow less competition between the plants and optimally more seed fill per plant.

All of these techniques talked about today by Jim are by no means new to New Zealand’s precision ag scene, however some are done to varying degrees here.

So, what’s the take home messages from today?

1. Start your Precision Ag journey with what will give you the biggest financial change
2. Use your yield maps and turn them into something other than pretty wallpaper – talk to someone in the know on how they can be made useful J

Regular Farm Irrigation Assessments Pay-Off

The current soil moisture deficit conditions in many areas of New Zealand should prompt irrigators to assess the efficiency of their irrigation system and management practices. The information that this blog is beginning to build upon hopes to increase understanding and awareness of technologies so these improvements can be implemented.

What is yet to be defined is Irrigation System Efficiency, while you will find many variations in the wording of definitions in a nut-shell it is the ration of irrigation water available for plant growth to the total amount of irrigation water delivered to the farm. So 80% Irrigation System Efficiency means that 80% of the water delivered to the farm has been applied and stored in the crop root zone and therefore available for plant growth.

Recent roadside assessments of irrigation systems show there are some very simple irrigation management modifications that can be made with only the basic level of knowledge.

Irrigating the road = 0% irrigation efficiency as well as being a safety hazard. However much irrigation you put on the road it’s still not going to grow grass!

If your irrigator has an end gun control function then contact your irrigation dealer to find out how to program the end-gun to turn off at any point it is irrigating outside the boundary of the growing area. If your irrigator does not have an end-gun control function than you may consider a GPS End Gun Controller, for more info click here or contact your local Zimmatic Dealer.

Ensuring that the staff that are charged with managing your irrigation as well as those that occasionally help out are adequately trained is really important. If there is not the time or resources to carry out the training in-house there are courses run through IrrigationNZ and many online resources that are very helpful. Considering a guidance system for shifting K-line’s could resolve many issues and result in a significant increase in your irrigation efficiency.

Regular maintenance of your irrigation system can save wasted water as well as forgone growth from under-watering. As an example a blocked sprinkler near the end of a 500m centre-pivot could be causing ~5ha of your property to be under-watered. Many of these maintenance issues are easily identified provided staff are aware of what to look out for.

Limitations of irrigation infrastructure can be a constraint to improving your irrigation efficiency. As seen in the image above the irrigation water being applied within the ditch is not contributing to pasture growth, and is likely to cause wheel rutting and potentially a stuck pivot. Should your centre-pivot or linear-move irrigator run over non-productive areas, roads, tracks or water-ways then variable rate irrigation technology would allow you to avoid irrigating these areas. This not only will save you water and potentially energy costs but also prevent the other issues that arise.

Future blog posts will discuss variable rate irrigation technology in more detail and the many applications in addition to avoiding irrigating certain areas where the technology offers benefits.