Crop rotation, seaweed extracts, lime, and a range of organic materials can all improve soil health and crop yields. Professor Geoff Dixon shows you several ways to improve your soil.
Rapidly rising costs of living are affecting all aspects of life. Increasing costs of fertilisers are affecting food production, both commercially and in gardens and allotments.
Wholesale prices of fertilisers have jumped four-fold from £250 to £1,000 per tonne within six months. All forms of garden fertilisers are now much more expensive. Crops, especially vegetables, only thrive if provided with adequate nutrition (see nitrogen-deficient lettuce below). Consequently, fertiliser use must become more efficient.
Nitrogen deficiency in lettuce.
Healthy, fertile soils achieved through good management are key to this process. That ensures roots can take up the nutrients needed in quantities that result in balanced, healthy growth.
Soil pH is a major regulator of nutrient availability for roots. Between pH 6.5 to 7.5, the macro nutrients, nitrogen, phosphorus, and potassium are fully available for root uptake. Below and above these values, nutrient absorption becomes less efficient.
>> How much soil cultivation do you need for your vegetables? Find out more in Prof Dixon's blog on cultivation.
As a result, soluble nutrients are wasted and washed by rainfall below the root zones. Acidic soils can be improved by liming in the autumn. Sources of lime derived from crushed limestone require up to six months to cause changes in soil pH values. Lime should be used in ornamental gardens with caution as it can result in micronutrient deficiencies.
Iron deficiency in wisteria.
Soil health and fertility are greatly increased by adding organic materials such as farmyard manure and well-made composts. Increasing soil carbon content helps mitigate climate change while raising fertiliser use efficiencies.
Beneficial soil biological life such as earthworms, insects, benign bacteria and fungi are greatly encouraged when you increase soil humus content. Using crop rotations, which include legumes, raises natural levels of soil nitrogen. This is a result of legumes’ symbiotic relationships with nitrogen-fixing bacteria.
Leafy vegetables such as brassicas require large amounts of nitrogen and, hence, should follow legumes in a rotation. Avoiding soil compaction encourages adequate aeration, benefiting root respiration and providing oxygen for other organisms.
Organic materials are of great value in ornamental gardens when applied as top dressings in late autumn or early spring. This provides two benefits: a slow release of nutrients into the root zones as decomposition occurs, and prevention of weed growth.
Inorganic fertiliser use can be further minimised by using proprietary seaweed extracts. These contain macro- and micro-nutrients plus several natural biostimulant compounds that aid healthy ornamental plant growth and flowering (illustration no 3 rose Frűhlingsgold).
Written by Professor Geoff Dixon, author of Garden practices and their science.
Think of Earth as an apple and the soil as the peel. Now, imagine that more than 70% of this apple’s surface is covered in water. That veneer of peel suddenly seems very small indeed.
Dig beneath the surface and you realise that the world’s soil resources aren’t as plentiful as you first thought. When you take into account all of the uninhabitable, non-arable land on our planet, including the snow-bound poles and deserts, you’re left with just 3% of total landmass to grow all the fruit and vegetables we eat.
After reminding her listeners of some stark facts at the Soil resources in the UK: overlooked and undervalued? webinar, Jane Rickson, Professor of Soil Erosion and Conservation at Cranfield University, reminded us that soil is a precious, finite resource. “We’re dealing with a very thin resource that has to deliver all of these goods and services.”
You just need to think of your breakfast, lunch, and dinner to realise just how important soil is. Of all the food we eat, 97% comes from terrestrial sources. However, in recent decades, the many benefits brought by soil have been taken lightly. Apart from providing food, animal fodder, and a surface for football, it plays a vital role in climate change mitigation.
‘Soil is excellent for climate change mitigation,’ said Professor Rickson, recipient of the prestigious Dr Sydney Andrew Medal for 2021. ‘We know that healthy soils can support vegetation and crops and plants in taking out atmospheric CO2.’
A cross section of soil layers. Unless you live on fish and seaweed, it’s likely that almost all of your food sources will come from terrestrial sources.
However, she and her colleagues at Cranfield University have unearthed some unsettling facts about the state of our soils. She mentioned that 12 million hectares of agricultural land worldwide is lost each year due to soil degradation. In the UK, soil erosion rates can be as high as 15 tonnes per hectare per year, with soil formation rates only compiling at a rate of 1 tonne per hectare per year; and, based on current rates of erosion, some soils could disappear completely by 2050.
So, what is being done to arrest this problem? The obvious mammoth in the room is climate change, with extreme weather events such as flash floods precipitating a huge amount of soil erosion. Obviously, climate change mitigation measures on a national scale would help, but adjustments to farming practices could also improve soil resilience on a more local level.
A lot of work is also being done to reduce the intensity of farming to improve soil health. The aim, according to Rickson, is to maintain a fertile seedbed while retaining maximum resistance to soil degradation. There are lots of different ways to do this.
One approach being taken is cover cropping, whereby a crop is grown for the protection and enrichment of the soil rather than for immediate sale. This enriches the soil and helps prevent soil erosion. Another approach is strip-tillage – a minimum tillage system that disturbs only the portion of the soil that contains the seed row, with the soil between rows left untilled. She also mentioned the benefits of soil improvement, with poultry manure and mushroom compost used to improve soil health by Benedict Unagwu among others.
Cover crops such as vetch and oats improve the structure and fertility of the soil.
It is difficult not to have sympathy for farmers at the moment. Climate change falls heavily upon their lands, and they must battle flooding and drought to keep their farms financially viable. Professor Rickson often speaks to the farming community about soil health, with the focus placed on realistic solutions. As one farmer told her: ‘It's hard to be green when you’re in the red.’
Perhaps soil doesn’t capture the imagination the same way as an oak forest or a field ablaze with wildflowers, but its mismanagement is costing us a fortune. She estimated that the combined annual economic cost of soil degradation in England, Scotland, and Wales is £1.5 billion.
According to Professor Rickson, the US is probably the home of soil conservation following the harsh ecological lessons learnt from the Dust Bowl disaster of the 1930s. However, she believes the UK has plenty of knowhow in the area.
‘The UK has an opportunity to be world-leading in this,’ she said. ‘I think we are as good as anyone. Our scientific community understands soil and is really pushing the boundaries in terms of soil science.’
Soil is a very precious asset whether it be in your garden or an allotment. Soil has physical and chemical properties that support its biological life. Like any asset understanding its properties is fundamental for its effective use and conservation.
Soils will contain, depending on their origin four constituents: sand, clay, silt and organic matter. Mineral soils, those derived by the weathering of rocks contain varying proportions of all four. But their organic matter content will be less than 5 percent. Above that figure and the soil is classed as organic and is derived from the deposition of decaying plants under very wet conditions forming bogs.
Essentially this anaerobic deposition produces peat which if drained yields highly fertile soils such as the Fenlands of East Anglia. Peat’s disadvantage is oxidation, steadily the organic matter breaks down, releases carbon dioxide and is lost revealing the subsoil which is probably a layer of clay.
Cracked clay soil
Mineral soils with a high sand content are free draining, warm quickly in spring and are ‘light’ land. This latter term originates from the small number of horses required for their cultivation. Consequently, sandy soils encourage early spring growth and the first crops. Their disadvantage is limited water retention and hence crops need regular watering in warm weather.
Clay soils are water retentive to the extent that they will become waterlogged during rainy periods. They are ‘heavy’ soils meaning that large teams of horses were required for their cultivation. These soils produce main season crops, especially those which are deeply rooting such as maize. But in dry weather they crack open rupturing root systems and reducing yields.
Silt soils contain very fine particles and may have originated in geological time by sedimentation in lakes and river systems. They can be highly fertile and are particularly useful for high quality field vegetable and salad crops. Because of their preponderance of fine particles silt soils ‘cap’ easily in dry weather. The sealed surface is not easily penetrated by germinating seedlings causing erratic and patchy emergence.
Soil finger test
Soil composition can be determined by two very simple tests. A finger test will identify the relative content of sand, clay and silt. Roll a small sample of moist soil between your thumb and fingers and feel the sharpness of sand particles and the relative slipperiness of clay or the very fine almost imperceptible particles of silt. For a floatation test, place a small soil sample onto the top of a jam jar filled with water. Over 24 to 48 hours the particles will sediment with the heavier sand forming the lower layer with clay and silt deposited on top. Organic matter will float on the surface of the water.
Soil floatation test
Transferring plants between countries was a profitable source for novel commercial and garden plants until quite recently.
Potato crop: Geoff Dixon
Potatoes and tomatoes are classic examples arriving in Europe from South America during the 16th century. Substantial numbers of new plants fuelled empire expansion founding new industries such as rubber and coffee. One of the earliest functions of European botanic gardens was finding potentially valuable new crops for colonial businesses. At home selecting orchids and other exotics from imported plants brought fame and fortune for head gardeners managing the large 19th century estates such as Chatsworth. Commercially seed merchants selected by eye and feel new and improved vegetables, fruit and flowers.
The rediscovery of Mendel’s laws of inheritance brought systematic science and formalised breeding new crops and garden plants. Analysing the effects of transferring physical, chemical and biological characters identified gene numbers and their functions.
Colour range in Gladioli: Geoff Dixon
As a result, varieties with improved colourfulness, fruitfulness, yield and pest and pathogen tolerance fill seedsmen’s catalogues. Breeding increased food supplies and added colour into the gardens springing up in suburban areas as affluence increased.
Greater plant reliability and uniformity arrived with the discovery of F1 hybrids.
Hybrid Sunflowers: Geoff Dixon
Selected parental lines each with very desirable characters such as fruit colour are in-breed for several generations. Then they are crossed bringing an explosion of vigour, uniformity and reliability (known as heterosis). Saving seed from the hybrid lines does not however, perpetuate these characters; new generations come only from remaking the original cross. That is a major boon for the breeder as competitors cannot pirate their intellectual property.
Knowledge at the molecular level has unravelled still further gene structure and functioning. Tagging or marking specific genes with known properties shortens the breeding cycle adding reliability and accuracy for the breeder. Simplifying the volume of genetic material used in crosses by halving the number of chromosomes involved adds further precision and control (known as haploidisation).
Opportunities for breeding new plants increases many-fold when advantageous genes are transferred between species. Recent developments of gene-editing where tailored enzymes very precisely snip out unwanted characters and insert advantageous ones is now offering huge opportunities as a non-transgenic technology. Breeding science makes possible mitigation of climate change, reducing for example the impact of soil degradation brought about by flooding.
Flood degraded land: Geoff Dixon
Russian researchers have developed new fertilisers based on nanopowders of transition metals. In field trials on agricultural crops, harvests increased by more than a quarter, compared with conventional fertilisers.
Iron, cobalt and copper affect a plant’s level of resistance to pests and diseases. These microelements are typically introduced into the soil as soluble salts, but rain and irrigation can wash them away, requiring further applications. They also have potential to disrupt local ecosystems as they pass into the groundwater.
An irrigation system in Idaho, US. Image: Jeroen Komen@Wikimedia Commons
The team, led by the National University of Science and Technology (NUST) in Moscow, has developed a group of fertilisers that are applied as a powder to plant seeds, without losses to the soil or water systems. In this way, ‘the future plant is provided with a supply of necessary microelements at the stage of seeding,’ reports Alexander Gusev, head of the project at NUST’s Department of Functional Nanosystems.
‘[It’s] a one-seed treatment by a product containing the essential microelements in nanoform. These particles of transition metals – iron, copper, cobalt – have a powerful stimulating effect on plant growth in the initial growth phase.’
Gusev reports improved field germination and increased yields of 20-25%.
The main difficulty was to produce a powder from the nanoparticles, which tended to quickly stick together as aggregates, says Gusev – a problem they solved by using organic stabilisers and then subjecting the colloidal solutions to ultrasonic processing.
Gusev now wants to discvover how the new fertiliser acts in different soils, and in relation to different plant cultures. Its environmental safety also needs to be evaluated before widespread use, he adds.
But Steve McGrath, head of sustainable agricultural sciences at Rothamsted Research, is sceptical. Plants are adapted to take up ionic forms of these microelements, not nanoparticles, he says. ‘Also, seeds do not take up much micronutrients. Roots do that, and depending on the crop and specific nutrient, most uptake is near to the growing ends of the root, and throughout the growing season, when the seed and nearby roots are long gone.’
Critics are skeptical of the efficacy of the new kind of fertiliser. Image: Pexels
If there is an effect on crop yield, he thinks it is more likely to be due to the early antifungal and antibacterial effects of nanoparticles. ‘They have a large and highly reactive surface area and if they are next to membranes of pathogens when they react they generate free radicals that disrupt those membranes. So, in a soil that is particularly disease-infected, there may be some protection at the early seedling stage.’
Platinum is one of the most valuable metals in the world. Precious and pretty, it’s probably best known for jewelry – and that is almost certainly its oldest use. But its value has become far greater than its decorative ability; today, platinum powers the world. From agriculture to the oil markets, energy to healthcare, we use platinum far more than we realise.
1. Keep the car running
Platinum is needed to make fuel for transport. Image: Pixabay
Platinum catalysts are crucial in the process that converts naphtha into petrol, diesel, and jet-engine fuel, which are all vital to the global economy. The emissions from those petroleum fuels, however, can be toxic, and platinum is also crucial in the worldwide push to reduce them through automotive catalytic converters. In fact, 2% of global platinum use in 2016 was in converting petroleum and 41% went into reducing emissions – a circle of platinum use that’s more impressive than a ring.
2. Feed the world
Nitric acid is a by-product of platinum which is used in fertilisers. Image: Pixabay
Another vital global sector that makes use of platinum catalysts is agriculture. Without synthetic fertilisers, we would not be able to produce nearly as much food as we need. Nitric acid is essential for producing those fertilisers and platinum is essential for producing nitric acid. Since 90% of the gauzes required for nitric acid are platinum, we may need to use more of it as we try to meet the global food challenge.
3. Good for your health
A pacemaker. Image: Steven Fruitsmaak@Wikimedia Commons
Platinum is extremely hard wearing, non-corrosive, and highly biocompatible, making it an excellent material to protect medical implants from acid corrosion in the human body. It is commonly used in pacemakers and stents. It is also used in chemotherapy, where platinum-based chemotherapeutic agents are used to treat up to 50% of cancer patients.
4. The fuel is clean
In addition to powering the cars of the present and reducing their environmental impact, platinum might well be crucial to the future of transport in the form of fuel cells. Platinum catalysts convert hydrogen and oxygen into clean energy, with water the only by-product.
5. Rags to riches
The Spaniards invaded the Inca Empire, South America, in 1532. Painted by Juan B Lepiani. Image: MALI@Wikimedia Commons
Amazingly, despite all this, platinum was once considered worthless - at least in Europe. In fact, it was considered a nuisance by the Spanish when they first discovered it in South America - as a corruption in the alluvial deposits they were earnestly mining and they would quite literally throw it away. It wasn’t until the 1780s that the Spanish realised it might have some value.
Because platinum is essential to so many aspects of our economy, there are concerns about supply meeting demand – particularly as nearly 80% is currently mined in South Africa, which has seen its mining industry repeatedly crippled by strikes in recent years.
Two Rivers platinum mine, South Africa. Image: Wikimedia Commons
Some believe the solution to the issue of supply is space mining, arguing the metal could be found in asteroids.
Others, such as researchers at MIT, are working to create synthetic platinum, using more commonly found materials. Neither approach is guaranteed to work but, given our increasing dependence on this precious metal, we could be more reliant on their success than we realise.
A world with a rapidly increasing population needs a rapidly increasing food supply. However, with a limited amount of land to work with, farmers must maximise agricultural production on the land they have available.
Modern-day intensive agriculture techniques include mechanical ploughing, chemical fertilisers, plant growth regulators, pesticides, biotech, and genetic modification.
1. Crop production has rapidly expanded in the past few centuries
Farming has drastically changed since the time this picture was taken at the California Manzanar Relocation Centre in 1943. Image: Ansel Adams
Worldwide, the amount of cultivated land increased 466% between 1700 and 1980, with global food production doubling four times between 1820 and 1975. In 1940, the average farmworker supplied 11 consumers; in 2006, each supplied 144 customers. Two out of five American labourers were farmers in 1900, but now only one in 50 work in agriculture. In 1830, five acres of wheat took 250-300 hours of work to produce. By 1975, it only took 3¾ hours.
2. Crops can be grown without soil
Organic hydroponic culture in Ho Chi Minh, Vietnam. Image: Frank Fox
Using a crop-growing method called hydroponics, instead of putting plants in soil, a mineral solution is pumped around the roots. This makes it possible to grow crops in regions with low-quality soil or none at all, increasing the amount of space that can be used for agriculture. This technique also allows for the nutrients to be effectively recycled and eliminates the risk of soil organisms that cause disease.
3. At least 90% of the soy, cotton, canola, corn, and sugar beets sold in the US are GMOs
Since the 1970s, scientists have been working on genetically modifying crops to make them tougher, disease-resistant, more nutritious, and higher yielding. Though the first commercially available GMO came onto the market just 23 years ago, global markets have already been transformed by the ground-breaking innovation.
4. Regenerative grazing increases the health and productivity of pastures
Image: Tom Koerner/USFWS
Regenerative grazing - staggering grazing on different plots of land according to a calendar – has proven to increase soil health. By allowing plots to rest after grazing, the soil and anything living in it is able to recover before the next time it is used. Regenerative grazing cultivates fields with less bare soil and increases populations of earthworms and soil organisms. Not only that, it also eliminates the need for chemical fertiliser, increases grass growth by 14%, and causes a 10% decrease in carbon footprint per litre of milk.
5. Agricultural robots are transforming the industry
If you’re interested in the issues surrounding global food sustainability, you can watch the full video of Sir John Beddington’s recent SCI Andrew Medal Lecture: ‘Global Sustainability Challenges: Food, Water, and Energy Security’, here.