Expert opinion

The soil paradox

The general concept in mainstream farming is that (inferior) soil conditions can be modified by interventions of physical or chemical nature.

This belief however is fading away, now that soils pay the toll of decades of ongoing mechanisation, treatments and maximised productivity. Soil quality is not restraint, it is a constraint. And smart farmers now create opportunities from that notion.

Site-specific farming

The term ‘precision agriculture’ was first coined in relation to site-specific farming: adjust cultivation practices to soil (site) conditions. But decades of ongoing mechanisation and enlargement of fields made us forget about these soil properties, in particular when cultivation practices came in fashion to ‘homogenise’ the soils or at least treat them as being homogenic.

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Simple properties as soil depth or clay content can already tell a lot about its usability. - Photo: Henk Riswick
Simple properties as soil depth or clay content can already tell a lot about its usability. - Photo: Henk Riswick

Decline in soil quality a major threat

But looking back, we now see that farming practices in many places in the world have been over-exploiting soils which has now gone beyond the soil’s own resilience and recovery capabilities. Soils suffer from compaction, nutrient degradation, salinity, loss of structure and loss of organic matter and organisms. The decline in soil quality is a major threat to agricultural productivity and to the livelihood of farmers. But what to do about it?

Simple properties as soil depth or clay content can already tell a lot about its usability

There are basically 2 ways to approach this. First of all we can adjust agricultural practices to the capabilities of the soil: accepting the soil and it’s quality properties as a constraint to agricultural production. With the aid of sensor systems, network infrastructures, knowledge rules and deterministic models the quality of the soil and its capacity can be monitored and guide cultivation practices.

‘Land evaluation’

Simple properties as soil depth or clay content can already tell a lot about its usability. Research from the 50’s of last century into land evaluation als soil suitability analysis is more actual then ever. Using the latest technologies in satellite remote sensing, in situ sensors and models, e.g. for weather prediction make “land evaluation” an important field of expertise today to indicate what type of agricultural activity can take place at what location.

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Soils suffer from compaction, nutrient degradation, salinity, loss of structure and loss of organic matter and organisms. - Photo: Henk Riswick
Soils suffer from compaction, nutrient degradation, salinity, loss of structure and loss of organic matter and organisms. - Photo: Henk Riswick

The alternative approach is that we capitalise on our engineering and technology successes and adjust the soils to our needs: in analogue to what takes place in greenhouses, we can adjust the soil to become a medium or substrate. This leads to what is sometimes called the “outdoor factory”: Instead of a factory floor with static machines, the machines are moving around and make their adjustments to the soil and crop.

Conditions tuned to production optimisation

Analogue to Industry 4.0 and its concepts of process improvements, conditions are tuned to production optimisation. Soil structure can be improved by a diversity of materials, from organic compost to selections of urban waste. Soil chemistry can be improved by adding nutrients and pH regulators to get the right composition for growth.

Water management

This anthropocene vision on agriculture is already reality when we look at water management: irrigation and drainage systems help farmers to create optimal hydrological conditions for their crop growth and cultivation practices. In fact, in many places agriculture would not even take place if it wasn’t for irrigation and/or drainage.

Another example of anthropogenic soils are the fields near villages with integrated agricultural practices, where the stables were cleaned and the mix of hay and manure was spread on the fields. 1000 years of these practices provide very fertile soils, but not very extensive amounts of land.

Soil qualities for agriculture are in particular in the soil physical and soil chemical properties

Now soils are the top thin layer of the planet where life takes place. Soils are formed by millions of years of weathering, (re)distribution of minerals and biological processes changing these soils and leaving residue that enables other life to take place. Soil qualities for agriculture, or the ecosystem services as it is sometimes called, are in particular in the soil physical and soil chemical properties.

Location important for agricultural production

But more important for agricultural production nowadays is the location: favourable conditions for agriculture are not solely dependent on weather or soil, but include the distance to markets, infrastructures and labour. So, it is quite understandable that we want to adjust the physical and chemical properties of land in this ideal location to the needs for agricultural production.

This concept is worked out already in greenhouse agriculture, where we are for instance capable of increasing temperatures, light and CO2 levels and protect crops against adverse (weather) conditions. In greenhouses, soils are replaced by substrates that just form a habitat for plant roots and a buffer for plant nutrients and water.

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Collecting data from sensors help farmers to monitor relevant soil properties and act accordingly. - Photo: Mark Pasveer
Collecting data from sensors help farmers to monitor relevant soil properties and act accordingly. - Photo: Mark Pasveer

Continuous supply of inputs at high costs

Soil fabrication in the open field could be useful in creating the right ‘substrate’ in the right place. But soil fabrication in real life is a huge logistical challenge. A truck load of 10 tons of soil is a layer of only 0,3 mm. So a root zone of 30 cm/ha requires 1000 trucks. It makes you think if this is practical. Also, both the first and second approach require a continuous supply of inputs at high costs, in particular in terms of water, nutrients, crop protection agents and machines (and labour) to apply all these inputs.

Also read: What is the cost of vertical farming?

Improve existing soil properties

So, before we should even think about that, a third more practical approach seems appropriate: adjust our cultivation practices to maintain (or better: improve) existing soil properties. The concepts of smart farming provide means to make decisions that have positive impact on soil quality.

This is not only about precision agriculture, it is also about strategic choices in crop types, varieties, production targets and compliance to many quality assurance aspects, both from societal (license to operate) and from food-chain (license to produce) point of view.

Smart farming provides a list of favourable practices to improve soils

Smart farming – also called data-driven, or evidence based farming – will provide the insights on how certain cultivation practices impact on soil quality. In other words, it provides a list of favourable practices to improve soils. And a list of deteriorating practices too, logically. Collecting data from sensors help farmers to monitor relevant soil properties and act accordingly. Farmers will feel empowered by new data sources to do the right thing and to do things right.

Robotisation in agriculture

Furthermore, the upcoming robotisation in agriculture enables us to go back to small scale farming practices. The (economic) need to treat a field in an homogeneous way will no longer be a condition. With smaller, lighter and smarter robots, guided by data and sensors, farmers can still a sufficient acreage to make a living.

Strip cropping, intercropping, selective harvesting etc and all kinds of practices that are more dedicated to the individual condition of a piece of soil or a plant become in sight. This will help us keeping soils in good condition and productive.

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