Reducing waste in the potato supply chain comes down to careful management of soil, seed and water, as James Andrews discovers

Potato processor Solanum is planning to dramatically reduce waste in the supply chain by improving quality in the field.

War on Waste is a five-year project which the firm started in 2008 to assess the level of waste produced in the potato supply chain and come up with practical solutions to reduce it.

The project found that for every 1000t of potatoes produced for a retail crop, just 583t made it to the consumer. That meant 42% didn’t make it to the end market it was grown for.

Inefficiencies occur throughout the supply chain, but the most important area to address is how the crop is grown and managed in the field, says Simon Bowen, the firm’s agronomy director.

Solanum is tackling waste by working closely with its team of 40 growers to make sure field operations are as tight as possible. In 2009 the processor managed cut waste by 4% and has set a target to slash it to 35% by the end of the project in 2013.

The company is leading the way with the 80ha potatoes it grows in its own right. Simon Faulkner, the firm’s senior agronomist, looks after the day-to-day running of the growing enterprise and hopes to meet the target by carefully managing soils, seed supply and water.

SOIL

Making sure crops are planted in suitable ground is the first consideration, as poor soil condition is the greatest contributor to waste, he says.

Soil structure and pest and disease pressure need to be examined before planting, but cropping history is looked at first. “We analyse cropping history before deciding which fields will be planted, the variety they will be planted with and the end market the crop will go into.”

To help with this, the firm is building a database of soil information across its grower group to keep tabs on how well crops are performing in each field.

All Solanum growers are given a planting programme, which takes soil type and condition into consideration. Understanding soil history and conditions means the right variety can be planted in the right field and they know how long the crop should be able to be stored.

Solanum has started to use soil diagnostic tools to give a more accurate picture of soil health, but further development is needed, he notes.

Soil structure is crucial and compaction is a key reason for poor crop consistency and loss of marketable yield, says Mr Faulkner.

Miss-shaped tubers are the main defect caused by poor soil structure, but scab risk is also increased, he says. “We dig down and look at the soil structure, or even better, we get an expert to come and have a look with us before planting.”

A large proportion of Solanum’s crops are grown on deep silt fenland soils, but compaction can still be a problem, he notes. All ground is currently ploughed to about 30cm, but the firm is hoping to trial some crops with minimum tillage cultivation.

Cultivation technique is varied according to the soil type and condition, he says. “You don’t want to underwork ground, but you don’t want to overwork it either. We adjust cultivations to suit each field.”

Timing of cultivation is even more important than technique and he does not travel on fields which are too wet.

SEED

Matching the right variety to the right soil is crucial for quality, says Dr Bowen. The firm is starting to grow more resilient varieties such as Melody and Mozart, which are less susceptible to disease than older varieties such as Estima and Romano.

Maris Piper is still grown for its taste and texture, but it is high maintenance and needs to be planted on the best ground, he says. “Maris Piper is high input. It suffers from scab and it is drought susceptible, so it needs to be placed vary carefully.”

Desiree and King Edward are also high maintenence and need to be managed accordingly, he adds.

Planting density is adjusted according to the end market with smaller tuber markets planted at higher densities. Chronological ageing is also used to plant seed at the correct physiological state for the market, says Mr Faulkner. “This can influence the number of stems the plant produces, so for King Edward we look for chronologically young seed.”

Geographical location of the seed source is also considered as this can influence maturity. For example, Scottish seed is often later maturing than seed from the Continent, he says. “To make sure you get the seed you want, you really need to be thinking about it 18 months before planting.”

For this reason, Solanum is working with its grower group to improve seed management and make sure the best seed is always being planted in the most suitable soil.

Seed dressings are a useful tool, but are not a replacement for good management, says Dr Bowen. “They can help, but we don’t rely on them. You need to tackle pests and diseases head on and not just cover them up.”

When applying seed treatments, it is essential to achieve good coverage, he adds.

The firm is migrating to varieties with better drought tolerance where possible, says Dr Bowen. “The market is still very driven by appearance and we have to select varieties according to taste, but drought tolerance is moving further up the agenda.”

This year Solanum is growing main crop varieties Maris Piper, King Edward, Desiree, Madeleine, Orchestra and Charlotte, says Mr Faulkner.

The company used to grow Charlotte as a salad crop, but challenges with early harvesting and skin set problems mean they have moved to the European model with tubers harvested at 60mm diameter.

“This is a good example of crop utilisation. The smaller tubers can go to the salad market and the larger ones for normal packing.”

Mr Faulkner is also growing a number of salad varieties, which helps to widen the harvesting window. “We try to spread harvest from mid-August to mid-October.”

Planting is scheduled for early March, but will be governed mainly by soil temperature, soil condition and weather, he notes. “There is no point planting into cold land and day length also needs to be considered.”

Ridge rolling is often used to reduce the risk of greens. Cambridge rolls are used to flatten the ridges and close up any cracks that could let light reach the tubers, he says. “Even running a quad bike down the ridges will do the job.”

Rapid store loading and locking of crops in the store help get the tubers to the right temperature and prevent temperature changes during unloading. “We also carry out detailed in-field examinations before the crop is lifted to highlight any potential problems which will need to be managed in-store.”

WATER

Solanum is improving irrigation management and is aiming to reduce its reliance on water. The company has opted for a trickle irrigation system as it improves water placement and, at the moment, requires no abstraction licence, says Mr Faulkner. “It seems more expensive to start with, but if you look at it in the balance sheet it works out about the same as the alternatives.”

Trickle irrigation also reduces drift and lowers the risk of drought stress, he says. “Moisture stress is one of the main drivers for miss-shaped tubers and I definitely think trickle irrigation increases marketable yield.”

Because soil is always moist, it prevents the crop going through a stop-start growing pattern, he says. “You need to have gentle uniform growth to prevent tuber miss-shapes.”

Soil 4 Life

Soil 4 life is a joint project between Solanum and Cranfield University to build up a database of soil information across the grower group.

Currently, 12 of the grower group are participating in the trial, but eventually it will be rolled out to the whole group.

The database will be interrogated to give an exact history of a particular field, says Dr Bowen. “It is a huge base of knowledge and we will be able to look back and understand the impact of putting a certain crop into the rotation, such as a brassica.”

It can also be used to understand why the most successful crops have done well, he says. “There will be some relationships out there that we have no idea exist.”

Solanum is six months into the three-year project.