The Carbon Positive programme continues. Our McCain Foods green bean crop has been successfully harvested and yield and quality data captured. Post-harvest, Alex and Oliva completed VSA tests in all the plots, and those and other data are being collated and processed.
All treatments achieved good yields, but we found significant differences between them. We harvested 1 m2 of crop from each of four sub-plots in each of our 12 plots. That gave us lots of beans which were then removed by hand, weighed and graded. We also got factory results from the different treatments. The box plot graph below shows the average yield (the Xs) and variability in each treatment as determined from our hand harvest plots.
The biggest cause of down-grading at the factory was pod damage associated with harvesting and transport. Other than that, we had a very clean crop.
So why the differences?
The regenerative plots had the biggest plants. This was seen throughout the season with the canopy ground cover always being ahead in the regenerative plots. Towards harvest, we found the conventional plots had two weeks when their growth appeared to be checked. We know it wasn’t soil moisture or nitrogen availability, but we can’t put a finger on a cause.
Both the conventional and hybrid areas were planted in process peas at the end of August. The soil was cold and wet and we noticed compaction from cultivation and machinery passes. The conventional plots were ploughed and disced, and the hybrid plots direct-drilled before the cover crop was mulched. The regenerative plots were kept in cover crop, which was mechanically terminated before a period of fallow.
All the plots were disc-ripped about three weeks before planting, then sprayed with glyphosate to achieve a stale seedbed before bean planting on 28 December. Both the conventional and hybrid plots received nitrogen fertiliser broadcast near full canopy. The regenerative plots did not receive solid fertiliser, but did get a foliar application as part of spraying for disease and caterpillars. The spray programmes were different from the pre-emergence herbicides through the crop protection programme.
We can’t say what made the differences to the yields that were achieved, because our trial is not set up that way. We are comparing the results of overall management policy over six years rather than assessing the effect of any single input.
So, we can’t say why. Maybe there was less disease pressure by missing peas? Maybe the better soil physical state by avoiding early cultivation and planting in the wet made a difference? Maybe the cover crop biomass was feeding the soil microbes or releasing nutrients? Maybe all of these? Maybe something else…
The VSA assessments appear to show differences developing in the different treatments. We need to keep monitoring and see a longer-term trend, but for now, the regenerative plots are starting to score a little better. The soil appears somewhat darker, suggesting it may be building soil carbon levels (we’ll be lab-testing soon so keep an eye out for that) and it has fewer large soil lumps (in our case mainly showing compaction damage). It does suggest that working the soil and driving over it when cold and wet in August had impact.
We expect to drill the winter cover crops in the first week of April. With continuing dryness, we have applied irrigation to make the soil moist enough for drilling. Our intention is to aerate after drilling to avoid compacting the soil again. Then we’ll leave everything alone until spring to allow the soil to breathe, microbes to do their thing, and roots and earthworms to explore as easily as possible.