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.