Wednesday, 28 June 2017

Water, water, not everywhere  – water use and conservation at SPot East this season

By Teresa Meadows, KE Manager, SPot Farm East

With the hot, dry weather experienced across the country and in particular in East Anglia, thoughts at the first SPot East meet of the 2017 season turned to the mitigation of the impact of the dry weather on the potato crops and the social responsibility that comes with managing irrigation.

Andrew Francis, Farm Manager at Elveden Farms, takes water seriously and that is water in all respects. Andrew manages everything, from the accurate timing of water to the crop, through to ensuring that this water is used efficiently to minimise risk of common scab and does not cause soil erosion and diffuse pollution through loss of N or other actives from the site.

Of the five demonstration areas at SPot East for 2017, three are concerned with water use. There is more detail on each below:

N and Irrigation

Developing the findings of the trials that took place at Elveden Estate last year is the focus of this demonstration in 2017. Key questions include:

• What is the best rate of N to use to maximise efficacy of take-up and reduce loss of N through the soil profile? 
• What irrigation scheduling should be used in order to avoid drainage events?  
The replicated trials are beginning to show the effects as the season starts.

At the field walk on 22nd June, there were differences in colour between the trials beginning to show between the standard (18mm at 18mm deficit) and over-watered (25 mm at same deficit) demonstrations.

• Will this difference develop through the season?
• Can we use remote sensing applications or aerial technology to look at how this difference develops?

Follow the blog to find out more as the season develops.

The sensors through the soil profile will also show how the N has moved through the profile and whether that is related to irrigation or rainfall events through the season.   Ideally, the data from this trial will allow for a more predictive system to be developed, answering many potato growers’ burning question of…”do I need to top up after this heavy rain?”

One treatment in this trial has also received only 160kgN/ha.   Even for this late variety, Brooke, there is the thought that this might be insufficient to get it through to the end of September.  However, will further N need to be applied for yield later on in the season?   There is the possibility that this lower rate might compromise longevity later in the season, though it does not appear to have had an effect on expansion to-date.  A decision on whether to top-up this base amount will be made in early July.

Common Scab Control

2017 looks to be a ‘good’ season for testing irrigation regimes and their link to common scab control!  Building on the work at SPot East last year, this year a range of varieties are being used to look at two different irrigation treatments for scab control to find the ideal irrigation response on different soil types per variety.   The two treatments which are being trialled at SPot East this year include:

 1. Standard: 15 mm doses at 12-15 mm soil moisture deficit
 2. Infrequent: larger (25 mm) doses every alternate application of ‘Standard’

Owing to the shorter emergence period in 2017 compared with 2016, this season is looking likely to require a shorter scab control period than the normal 4 weeks for maincrop varieties.    This highlights the essential need to know your emergence dates and tuber initiation timings.

Attendees on the June Farm Walk asked: “When is your scab period over?”  Dr Mark Stalham shared that this is typically when the majority of the crop reaches 35-40mm in diameter, then the risk is significantly reduced.    The recommendation is to ensure that the soil in the ridge is wet from 1 week to 3 weeks after tuber initiation, since this is the critical period when pathogen populations build up rapidly in dry soils.  Irrigating outside of this critical period will still improve scab control in most varieties but the key target period should be kept in mind in hot weather and when irrigation application capacity is stretched.

Run-off Trial

The desire to keep soil and water in the field has led to a partnership being formed between a large range of organisations this year, to look at ways to ensure no diffuse pollution occurs when growing a potato crop.   With the Elveden Estate situated in the Cam and Ely Ouse catchment and with a number of Safeguard Zones across the Estate, ensuring no diffuse pollution takes place is a key consideration for Andrew and the team.

Using a field with a 4° slope on the Elveden Estate, three pieces of machinery have been trialled this year to act as tramline disruptors and contain water between the rows and allow for filtration back into the soil.   The Creyke, Wonderwheel and Briggs machines have all been trialled in two locations – one that has had controlled wheelings (only had the de-stoner and planter through) and another that has been trafficked four times to mimic the sprayer passes.

These have then also been irrigated to two different ways – firstly with an intense boom event (18mm single pass) and the second with a rain gun (18mm but over a longer period of time).
Early signs of this work look like the treatments are inhibiting the flow of this water down the slope – come along to our Open Day on 6th July to see the treatments in action under irrigation and compare their effectiveness.

Keep an eye out for the next blog post, looking at the results as they develop from our herbicide programme post-linuron and manipulating tuber numbers trial.

Hope to see you on the 6th July at our SPot East Open Day,
Teresa Meadows
AHDB Knowledge Exchange Manager

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