Monday 30 March 2015

"A period (long) of dry weather that is harmful to crops"

In this blog I am going to use the d-word aka drought; i.e. “A period (long) of dry weather that is harmful to crops”.

Canterbury (and parts of lower eastern North Island) has had weather conditions that are having (and have had) an adverse effect on plant growth since December 2014 - a drought.

Since November (and especially since December) ET has outstripped rainfall on a daily basis.  Setting aside an isolated 27mm rainfall on 22 February there have been only 10 days since 1 December when the daily rainfall has exceeded ET.  In that time a soil moisture deficit of more than 170mm has developed on a Lismore silt loam or about 3 months average rainfall.  
This season is not abnormal and is very similar to the El Niño event of 1997-98.  Do the seasons 1997-98 and 2014-15 have similar El Niño Southern Oscillation Indices (SOI)?  Comparison of the SOI for the two seasons shows strong similarity.  No question 1997-98 had much stronger SOI with index values, especially in December-March when they were in excess of -20 in.  While the index alone does not guarantee drought like conditions, most will remember the 1997-98 drought. 

The 2014-15 SOI is similar because it has been negative since June and greater than -6, the indicator of a strong event.  El Niño typically results in the lower than normal rainfall on the east coast - so it has been on the east coast of Canterbury and parts of the North Island. 

If the seasons continue to mimic each other it would appear there is still a wait till April or May for a significant rainfall and probably not until May before rainfall might exceed ET and start to attack to the soil moisture deficit. 

This insightful blog post was written by Dr Anthony Davoren from HydroServices Ltd

Tuesday 24 March 2015

Information Aplenty for Farmers at the Sustainable Irrigation Field Day

The Sustainable Irrigation field day last Wednesday saw an excess of 50 attendees interested in learning more about variable rate irrigation (VRI), electro-magnetic (EM) mapping and soil moisture measurement technologies. Hosts Peter Mitchell and Nick Webster of North Otago’s Mitchell and Webster Ltd noted that there was a strong contingency of farmers in the turnout which was very encouraging. Farmers are hearing about the benefits and thinking more seriously about precision ag technology as a means of helping them increase resource efficiency and revenue.

Jemma Mulvihill (Agri Optics New Zealand Ltd) discusses EM mapping and how the data can be used to make informed irrigation scheduling decisions.
The afternoon was held at the Mitchell and Webster Ltd’s Dairy farm in Enfield, inland of Oamaru, which was converted from cropping two years ago, with Growsmart Precision VRI systems installed on their two centre pivots covering 100 hectares of the property and EM mapping by Agri Optics Ltd for the majority of the farm. Peter and Nick started off the series of talks with a run through of the farming system and the use of precision ag technology on the farm. The farm covers 200 hectares and soils generally have a high clay content with drains installed across the property to both decrease waterlogging and negate the presence of seasonal springs.

Nicole Mesman (Lindsay NZ) presented the key findings from the joint Lindsay NZ (formally Precision Irrigation) and Agri Optics summer case studies carried out on the Mitchell and Webster Ltd Dairy and McCarthy cropping block. The studies showed that use of Growsmart Precision VRI on the dairy farm allowed for more efficient irrigation and resulted in enough water being saved to irrigate an additional 15 hectares using K-lines. Assuming an increase in production with irrigation of 6 tonnes DM per hectare, long term average payout of $6/kg MS and 15% DM wastage and 11.4 kg DM eaten to produce 1 kg MS additional revenue as a result of VRI was calculated to be $40,000. The cost for VRI and EM mapping on the property totalled $100,000 therefore this represents a 40% ROI. EM mapping has also allowed for identify soil zones to further increase irrigation efficiency and has allowed for identifying areas to put soil moisture sensors in.

Nicole and Peter installing soil moisture
sensors at the McCarthy cropping block.
On the McCarthy block the centre pivot with Precision VRI installed covers 82.5 hectares of rolling hillside and alongside EM mapping has resulted in a reduction in water usage from 34 l/s to 26 l/s. This is from avoiding irrigating 7.5 hectares of springs and ditches and varying irrigation application based on soil texture as well as topography and topsoil depth (influenced by aspect). Annual savings on the property total $39,500 due to both decreased water charges and increase in production.

Paul Reese, Projects Manager with Irrigation NZ discussed the findings of the Sustainable Farming Fund – Hill Country Irrigation project that concluded near the end of 2014. The research trial investigated irrigating hill country (slopes between 16° and 25°) and as a result produced a resource book ‘Irrigation on Hills’ from the findings (available from IrrigationNZ). Key findings include the need to recognise that runoff on hills takes place throughout the soil profile, not just on the surface. Therefore application intensity must equal or be less than the slowest permeable layer in the profile.
Environmental considerations for the region were presented by James White (Otago Regional Council, ORC) and Dylan Robertson (North Otago Irrigation Company, NOIC). The ORC Water Plan rules related to irrigation fall into three main areas:
  1. Discharges of effluent, silage or composting materials are prohibited directly to a waterway, to a bore or soak hole, to land 50 m of a river, to saturated soils, at a rate causing ponding.
  2. Surface water discharges – must ensure discharges to rivers comply with Schedule 16 thresholds and that nutrient levels in rivers also comply with Schedule 16 thresholds for 2020.
  3. Discharges to groundwater – landowner must identify what zone property is in, for instance 15, 20 or 30 kgN/ha/yr and monitor system nitrate leaching using Overseer in order to achieve compliance when these limits become compulsory in 2020.

Efficient and accurate irrigation is essential to achieving regional targets for water quality. More information on Schedule 16, Regional Water Plan can be found here. Landowners can also request a Fact pack with information regarding regional rules.

NOIC are proactive in encouraging shareholders to comply with regional environmental standards by providing assistance for those wishing to undertake water testing. They offer support to shareholders looking at completing Farm Environment Plans, a template is available to help ensure they meet requirements. 

Posted today by Nicole Mesman and Sarah Elliot from Lindsay NZ

Wednesday 11 March 2015

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 18th 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 18th 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 18th 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.

Tuesday 10 March 2015

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.

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