A new project was started in autumn 2015 to assess the impact of cover crops in conjunction with strip tillage for sugar beet, in a collaboration between Agrovista and The Morley Agricultural Foundation, on its home farm at Morley, Norfolk.
The farm's five-year rolling average adjusted sugar beet crop yield is 84 tonnes per hectare. Typically, the crop is grown after wheat, ploughed throughout the winter and drilled at the end of March.
Strip tillage would appear to be an attractive alternative as it uses less energy, and is potentially better for the environment and soil, yet has to balance with the ability to grow a reliable, profitable crop.
Previous experience with this cultivation method at Morley Farms has delivered variable results. The aim of these trials is to see if cover crops will help condition the soil to provide a more reliable outcome from strip tillage. The trial was carried out on a loamy sand soil, typical of that found across the farm. Large plots of various cover crops were drilled in summer2015, followed in April 2016 with sugar beet drilled using a strip tillage technique.
Cover crops chosen were Terra Life Biomaxx DT (white mustard, oat, phacelia, tillage radish, buckwheat, bristle oat, linseed, false flax), Chlorofiltre 25 (black oat and vetch), Chlorofiltre 31 (black oats, vetch and Berseem clover) and Chlorofiltre Vita Myc (black oats, Berseem clover, common vetch, crimson clover + mycorrhizal seed treatment) . One plot contained untouched stubble.
Trial layout
Large strips of the three black oat-based cover crop mixes and TerraLife Biomaxx DT were drilled in late August using a Kverneland tine seeder. An area was left as stubble for comparison.
Growth was initially slow due to the wet and cool August/ September period. However, the mild October and November kept crops growing and they provided even ground cover that was relatively weed free.
The three black oat-based mixes produced similar amounts of biomass. Competition between species was most noticeable in the TerraLife Biomaxx DT mix, which became dominated by white mustard and spring oats.
Cover crops were sprayed off with glyphosate + Companion Gold in early December or early March.
The two types of cover crop had very different levels of residue post-destruction and prior to strip-till and drilling in the spring, with the black oatbased mixtures leaving much less debris on the surface.
On April 22 the field was strip tilled to a depth of 20cm using a Cultivating Solutions RS3000 RapidLift. Bands of soil 10cm wide were cultivated, leaving 40cm of undisturbed soil in between.
The field was left to haze over for an hour before precision drilling with a Vaderstad Tempo drill at a seed rate of 1.15 units/ha. Although strip till and drilling could have been combined as a one-pass operation, less-than-ideal soil conditions meant the decision was taken to use two passes.
Three replicates of 2x10m row lengths of sugar beet were hand-harvested on November 28 in strip till plots with and without black oat and vetch cover crop, and in an adjacent field where the same cover crop had been ploughed in. The British Beet Research Organisation carried out weighing and quality analysis.
While the field yield exceeded that of nearby fields that suffered most in a wet June, it didn't quite match the yield of an adjacent field, where a black oat and vetch cover crop was established in the autumn and ploughed in.
However, growers have had years of experience to perfect use of machinery in a conventional plough-based system and it will take a number of years to perfect a different system.
Project conclusions
All cover crops established well. Terralife Biomaxx became dominated by brassica species and also attracted slugs.
Headlands looked much better than the other fields of sugar beet on the farm.
Early destruction of the cover crop did give more consistent results.
We suspect without brassicas in the cover crop and with slug monitoring there would be little timing effect.
On this occasion there was no difference in yield of strip tillage sugar beet with or without cover crops. This is only one year and there are many reports of cover crops enhancing subsequent crop yields.
The trial performed very well on one year's results.
With careful planning and execution, there are no negative effects from the techniques used and very respectable crop yields were achieved.
Further Work
Valuable lessons were learned which will be implemented in year two of the project:
Strip tilling is best carried out when soils are dry at depth (which was not in the case in spring 2016). In year two of the project we will compare autumn and spring strip till.
Slugs were not expected to be a problem on this sandy loam field so routine treatments with slug pellets were not carried out. However, in a cool wet spring, following cover crops, particularly one cover crop dominated by brassica species, slugs reduced crop establishment. In year two of the project we have replaced that brassica-based cover crop with a lower biomass (above ground) leguminous cover crop.
Early destruction of the cover crops was beneficial for both crop establishment and yield.
There was a risk that destroying the cover crop too close to drilling would limit early growth due to nutrient lock-up and plant residue could compromise the operation. If the cover crop was destroyed earlier (December) there was a risk we lose out on another two months' growth and biomass.
Both timings were tested. Following early destruction, a second application of glyphosate is necessary. In year two of the project we will compare a split-dose glyphosate (winter and spring) with a spring-only application.
Strip tillage should follow the same direction as planting of the previous crop and cover crop
The Aims of the project were to:
- compare the establishment and growth of different cover crops
- assess variations on more compacted areas
- identify the optimum time to destroy the cover crop
- assess whether cover crops help when establishing sugar beet with strip tillage
- compare yields with a plough-based system
- highlight negative consequences
Treatments 2017
The headland and remainder of the field will be black oat and vetch cover crop followed by strip-tilled sugar beet
Cover Crops
Cover Crop
Destruction
Strip tillage
Black oats and
vetch 25/ha
Winter and spring
Autumn and spring
Berseem clover
6kg/ha
Spring
Spring
Berseem clover
12kg/ha
Spring
Spring
Untouched
Stubble
Spring
Autumn and Spring
Year 1 Trial results
Adjusted yield and plant population (hand-lifted replicated plots)
Cover Crop
Destruction timing
Plant populations (‘000/ha)
Adjusted yield
STRIP TILL
Chlorofiltre 25
Spring
49.3
106.2
Chlorofiltre 25
Winter
84.3
116.3
None (stubble)
Winter
92
117.7
PLOUGHED IN
Chlorofiltre
Spring
95
126.0
Autumn cover crop
Relative sugar beet establishment (%) December destruction
Relative sugar beet establishment (%) March destruction
None – strip till only
100
49.3
Chlorofiltre 25
90
65
TerraLife BiomaxxDT
40
10
Chlorofiltre 31
90
65
Chlorofiltre Vita-Myc
90
65
For a full report on the trials outlined above, visit http://tmaf.co.uk/making-field-scale cover-crops-strip-tillage sugar-beet-work/