Tillage options: Refining our view on tillage operations (May 2020)

BBRO is frequently asked questions about the impact of adopting reduced tillage operations on the UK sugar beet crop. There had been work undertaken and reviews completed historically by BBRO (see report on strip tillage at the end of this article) but the STAR project gave us the chance to revisit our work, taking into consideration long-term crop rotation. 

As a subject, tillage will never stand still.  Machinery developments constantly present new options but also, as more data becomes available, we can hone and improve on best practice. Whilst trials have shown that beet yields can be challenging to maintain under reduced tillage, the impact and value can be very dependent on soil type, rotation and of course, cultivation strategy across the whole farm enterprise.

The STAR project is delivered through NIAB TAG, supported in part by The Felix Thornley Cobbold Trust, The Morley Agricultural Foundation and historically by the Chadacre Agricultural Trust.  The aim is to examine different cultivation systems for sustainable arable production. There are specific objectives to examine different rotation systems and to explore how they interact with cultivation systems and required inputs, and to demonstrate to Suffolk farmers on Beccles/Hanslope series clay soil, alternative systems of cultivation across the rotation.

The long-term trial (pictured above) was established in autumn 2005 at Stanaway Farm, Otley (Suffolk) and was named the STAR project (Sustainability Trial in Arable Rotations).  This experiment was established in Nelson field as a fully replicated, large plot (36 m x 36 m), trial on a Beccles/Hanslope soil (which is representative of many farms in the region).  The large plot system ensures that modern techniques and farm scale equipment can be utilised to reflect local farm practice, unlike many previous experiments.  Four cultivation techniques and four rotations are employed, resulting in 16 treatments.  These treatments are outlined in the Table 1.

Rotation key – 1 winter cropping, 2 spring cropping 3 continuous wheat, 4 Alt fallow + cc / herbal ley

Cropping key – ww (winter wheat), wosr (winter oilseed rape), soats (spring oats), sbn (spring bean), wbn (winter bean), sln (spring linseed), fal+scc (fallow with spring cover crop), fal+slcc (fallow with season-long cover crop), herbal ley (3 year herbal ley)

Cultivation and equipment used to establish each treatments in 2018/19 were as follows:

 Adding sugar beet to the rotation.

Sugar beet (variety Sabatina) were drilled on 2/4/19 at 1.3 units/ha and grown as per standard farm practice before harvesting on 14/10/19. BBRO monitored the plots and undertook replicated yield  digs in each. So, how did the sugar beet perform? 

Plant populations were variable across all treatments ranging from 81,000/ha (deep) to 101,000/ha (plough), with the shallow and managed approaches gaining intermediate results. Canopy cover in the sugar beet, assessed in July, showed no difference between tillage approaches, all being at 60% of full canopy growth stage.

However, sugar beet yields were significantly different (P=0.05) between deep tillage and the managed approach with yields of 83.4 t/ha and 73.9 t/ha respectively. Whilst yields were lower in the shallow and plough treatment, they were not statistically significant.

Differences in yield reflected through into the gross margin, with the highest margin obtained from deep tillage (£1044/ha) and the lowest margin of £848/ha in the managed approach. For comparison, in the continuous winter wheat margins, the plough and managed approaches were £688/ha and £706/ha respectively.

The table below shows the deep tillage approach as the clear leader regarding yield and financial benefit.

Plant populations were variable across all treatments ranging from 81,000/ha (deep) to 101,000/ha (plough), with the shallow and managed approaches gaining intermediate results. Canopy cover in the sugar beet, assessed in July, showed no difference between tillage approaches, all being at 60% of full canopy growth stage.

However, sugar beet yields were significantly different (P=0.05) between deep tillage and the managed approach with yields of 83.4 t/ha and 73.9 t/ha respectively. Whilst yields were lower in the shallow and plough treatment, they were not statistically significant.

Differences in yield reflected through into the gross margin, with the highest margin obtained from deep tillage (£1044/ha) and the lowest margin of £848/ha in the managed approach. For comparison, in the continuous winter wheat margins, the plough and managed approaches were £688/ha and £706/ha respectively.

The table below shows the deep tillage approach as the clear leader regarding yield and financial benefit.

So, how does this shape and refine our view on reduced tillage and sugar beet ?

The broad concensus from previously published scientific work was, that reduced tillage on sugar beet had been linked to the following, although not in all cases:

• More variable plant populations
• Increased soil resistance and bulk density (poor root penetration)
• Reduce available pore space (less water and air availability)
• Reduced yields

The STAR work in 2019 allows us to refine our views on the subject and whilst the impacts listed above are possible, they may be more likely to be related to the use of shallow reduced tillage options, whereas deeper reduced tillage options can work well, if not better than ploughing. This aligns with other research in Europe, that indicates soil structure issues in reduced tillage practice can limit sugar beet yields and an element of deeper lossening of the soil is important to maintain high yields.

We have to be mindful that these results represent just one year of sugar beet production in this long-term trial. However, it does show that sugar beet production in a situation when ploughing is replaced by a deep till option can work well. We know that reducing the occurrence and frequency of disruptive tillage such as ploughing is associated with improvement in soil health properties and is  certainly worthy of further discussion and investigation.

For more information regarding the STAR project please go to: https://www.niab.com/research/agronomy-and-farming-systems/farming-systems/sustainability-trial-arable-rotations-star

Previous outcomes from BBRO research into strip-tillage for sugar beet production.