Time to recover – British Potato Review
Andrew Goodinson, Agronomist and Potato Specialist at Hutchinsons, looks at soil health and resilience, and how to help it bounce back. ...
This autumn tested many fields above and beyond their limits and this month Andrew Goodinson, Agronomist and Potato Specialist at Hutchinsons, looks at soil health and resilience, and how to help it bounce back.
ONE bad year should not be a reason to abandon long-term soil health strategies. This is particularly important because soils which have been well managed are better placed to recover.
“Lifting – particularly for those who were lifting late – has been messy, but those fields are not going back into potatoes in 2024,” Andrew said.
“They need to be given time to recover. It is better not to do anything, even if you have deep wheelings, because if you go in to try and level it, you will end up creating yet more compaction as well as smearing the soil.
“If you have pooling in one area, then digging a channel to help it drain will be beneficial, but if not, then leave it alone until late spring when it is drier.”
He finds that spring-applied gypsum is useful for improving soil structure and permeability and will help solve problems.
“Field mapping and a high-definition soil analysis are also key to getting the most from the crop as they facilitate a tailored methodology rather than a flat-rate approach where some areas may get more than they need while others are left wanting.
“Soil mapping allows variable rate fertiliser and lime applications to optimise nutrition applications. These analyses help build long term soil management and/or resilience when done on your own land, but they are not so attractive on rented land, especially if rented on a short-term contract.”
Based in Herefordshire, Agronomist and Potato Specialist Andrew Goodinson has been working for Hutchinsons for 17 years and looks after nearly 8000 ha of farmland, including the Welsh borders, south Shropshire and Worcester. Most of the potato crops he looks after are destined for the crisping or processing markets.
This month he looks at the challenges growers faced this year, discussing some of the key ways these were addressed, and reflects on factors for consideration when planning for next year’s crop.
When it comes to planting this year’s potato crop, patience will be key. Spring cereals will be the traditional choice in fields not left in a poor state apart from being wet. If they are in very bad condition, he suggests growers should opt for a late planted crop such as maize, spring oats, or grow a cover crop to allow a good entry back into wheat.
“Returns on spring cereals are marginal, so on damaged land they are less likely to be pro table. If you are on rented land, you need to have some honest discussions with the owner about what happened and what is needed to help the land recover,” Andrew said.
In general, well-managed fields harvested well, particularly those that were lifted in September, while others never reached their potential. Either way, he recommends analysing what went well and what did not go so well from the strategy devised last spring.
“Soils for potatoes are subjected to so much cultivation to plant, and then to lift the potatoes, the soil is moved again, leaving a fairly low pore space. This year, because of the heavy rains, the pore space was soon filled with water, making drainage much more difficult,” said Andrew.
“Points to ponder include whether headlands were planted and the row direction in the field was aimed at minimising runoff and easing harvest. This year we have seen the impact of excess cultivations, and the effect this has had on soil health. “On the plus side, self-propelled harvesters did a better job than conventional harvesters, as they have a bunker and can unload onto trailers strategically placed on headlines, or sometimes even on the verge the other side of the hedge. “However, this does slow down operations, and can create a different challenge for potato growers whose operations are spread over a large area as they need more time to get round the crop, leaving their systems stretched when conditions are not ideal.”
The importance of trials to optimising profitable crops
Trials, when properly constructed, are key to moving forward with yield, quality attributes and therefore profitability, said Andrew.
“One of the areas we, as an industry, need to improve is to get the most from the potato plant in its early stages of development, particularly in the time leading up to tuber initiation. Trials to build better understanding of nutrition and the role of biostimulants as early growth promoters will help us get there.”
With so many different forms of nutrition, from base fertilisers to foliar sprays, he warns that it is too easy to just apply N to a crop but it is often not the right answer.
“We also need to move away from thinking that putting something on the crop at some stage during the growing season will be of help – especially if the rates used are made to fit the cost.”
He also notes that there are concerns about late blight resistance and how products work on the different blight strains.
“Since the demise of AHDB Potatoes, agronomists are key to unlocking the science of healthy production, and it is really important to work closely with colleagues and enhance our collective knowledge and avoid repeating work that has already been done,” said Andrew.
“Trials are an important way of doing this because it helps us build a better database from which we can work. They do, however, need to be done in the right way.”
On-farm trials play an important role as long as the potato crops being tested are planted in the same soil when replicated.
A recent trial Andrew did with one of his growers reviewed a number of potato seed treatments, assessing effectiveness on a number of parameters, including tuber number, average tuber quality, tuber weight and gross output per hectare. These findings were then evaluated for price effectiveness.
“If you have a higher number of tubers but they have quality issues such as growth cracks, something will need adjusting. Sometimes when we look at our trials results, we are surprised by the outcomes, and there have been times when the trials have shown us that the older best practice methods can be better than some of the newer innovations,” he said.
Other recommendations, such as seed rate guides, can be adjusted because variables such as the season and planting time can vary year-on-year. For example, soils that can hold moisture better than others may be able to support higher tuber numbers, but this needs to be tested before going ahead to reduce risk, he said.
Physiological age of seed potatoes can also differ, particularly after a stressful growing season such as 2022, so adjustments may need to be made here as well.
“If you do trials with the varieties you are growing, testing them in a range of different situations, it helps you really get to know how to get the best out of that variety whatever the season throws at you.”
Because of the moisture while soils were still warm, autumn 2023 had been good for establishing cover crops, Andrew said.
“We noticed that where cover crops had been planted in the margin, or had beetle banks, there was less run-off and soil erosion.”
He added: “As we have gained more experience with them, we have become better at balancing them for nutrient cycling and soil retention, which helps to retain nutrients such as nitrogen, potash, sulphur and phosphate, which occur when there is heavy rain and reduce subsequent run-off.”
He adds that leaf litter from a cover crop, by temporarily holding the water, gives the soil more time to soak it up. Slowing down the rate also allows water to percolate into groundwater reservoirs, so the soil can remain moist for longer.
“Each inch of rain weighs 2460t/ha (1000t / acre), so no wonder that after a wet season, bare fields can look slumped, compacted and wet.”
Generally speaking, cover crops need to be planted early – before mid-September – but if this has not been possible, he points out that home-saved spring oats, peas or beans are options because they will grow in the cooler temperatures.
In the west, stubble turnips have become popular because they can be used for grazing, and therefore provide an income from bare land.
“One of the questions I get asked is whether a cover crop used for grazing loses some of its benefits because the top biomass is removed.
However, the root structure underneath remains intact, helping to hold the soil together and preventing run-off, as well as increasing organic matter.”
Nonetheless, they need to be properly managed and have a run-back area so that the livestock can get out of the mud and wet, if necessary, he emphasises.
“Another option is a short-term ryegrass ley for winter grazing – and this can be particularly useful if you have brassicas and/or legumes in your rotation. For example, if you grow peas or beans, winter-grown legumes can increase the incidence of for bean seed y the following spring (important in veg crops).
“If you are growing vegetable brassicas or oilseed rape, not only you will need to assess whether the cover crop will increase the risk of club root but you may also see brown/white mustard volunteers in the crop.”
“Cover crops can be included as part of Sustainable Farming Incentive (SFI) schemes and using them means some useful income can be gained before planting potatoes. Additionally, growers have the option of using some bio-fumigant species in the cover crop mix to help manage PCN numbers.”
January and February are a good time to carry out potato cyst nematode (PCN) sampling, as long as the soils are not too soggy, as it can reduce accuracy. Testing for Free Living Nematodes (FLN) is best left until as close to planting as possible, he advises.
He also encourages growers to try biofumigants to help reduce PCN infestation levels. With the threat of losing some nematicides, cultural strategies for PCN management are likely to become ever more important.
Biofumigants need to be treated as a crop, they need to be established at the right time and the correct nutrition needs to be in place because first you need to establish a good crop. Its destruction – through the maceration and incorporation – is key.”
He said the tissues of brassica plants contain both glucosinolates and myrosinases. When the plant cell tissue is damaged, the two compounds react to produce the chemical fumes that can be toxic to some organisms, such as PCN, when they are incorporated into the soil.
Stubby root nematodes transmit Tobacco Rattle Virus (TVR), and one of the problems is that weeds from the same Solanum family, such as black nightshade, plus others including chickweed, can support and maintain populations of the virus.
“So, if you have these on your land, they will need good management.”
Partly driven by cover crops and less soil movement for combinable crops taking place in the autumn, wireworm infestations have been increasing.
Wireworm, which are the larvae of the click beetle, feed for around five or six months of the year, and populations are higher when potatoes are grown after a grass ley which has been laid for at least five years,” said Andrew. “The adults are attracted to grass strips and flower mixes, but the larvae do not like compacted, saturated soils or soil temperatures below 8degC”
The unfavourable late harvesting conditions in 2023 led to a threat of bacterial soft rots in store, and Andrew has seen at least one sample where the soft rot bacteria had infected the tuber through wireworm holes.
“We have also seen cases where the mother tubers had become infected with soft rot if seed was sprouting removal before planting but did not break down until later in the season, meaning we had bacterial soft rots in the field.”
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