Is soil suitable for this building plan?

There are great concerns about soil quality. On the one hand, from agricultural entrepreneurs who are concerned about declining levels of carbon and nutrients. On the other hand, from policymakers and advisors who seek a connection between social tasks and agricultural soil management.

During the  earlier article I have shown that the picture of declining soil quality is not in line with published trends and spatial analyzes of soil fertility in Dutch agricultural soils. Farmers take good care of their soil, partly because the value of their farm depends on its quality.

One of the causes of the negativity around soil quality, in my opinion, there is a non-concrete definition of soil quality, as well as a definition in which other goals overshadow the agricultural function of a soil. Many questions arose in response to both articles. What about my personal vision on soil quality?

If the agricultural soil is doing so well, are there no challenges for the future? And isn't there much more synergy to be gained from agricultural soil than we realize today? Those are good questions. That is why I briefly describe my vision on the (desired) quality of agricultural soil, where bottlenecks lie and how we (can) use the soil quality for both agricultural production and other social services.

An agricultural soil is there for crop production
An agricultural soil is used for growing crops, for human or animal consumption. A fertile agricultural soil is therefore one of the pillars of our food supply, for now and in the future. As far as I'm concerned, this is the first priority of an agricultural soil. This is reinforced today by the fact that land is very expensive. Yields must remain high in order to keep the company financially healthy in addition to the demand for food. Farming is an economic activity. 

A good quality agricultural soil facilitates this crop production by supplying water and nutrients and providing a nutrient medium in which to grow. Chemical, physical and biological processes play a role in this. Based on the principle of good entrepreneurship as well as stewardship, it is desirable to strive for a soil quality in which crop production is supported as much as possible by natural processes in the soil.

Fertilizers, irrigation or crop protection products should only be used to compensate for any deficiencies from the soil. In my opinion, this also means that these aids are in second place: the natural soil fertility is leading in this. An agricultural system that is completely dependent on external resources is very fragile and certainly not sustainable in the long term.

An agricultural soil needs to be fed
Good soil fertility cannot be taken for granted. The current good quality of our agricultural soils is the result of the interplay of natural geohydrological factors, soil management and fertilization of previous years. Because nutrients disappear through removed crops and natural processes break down the carbon present and acidify the soil, it is important to bring the soil into balance.

And in my view, this balance is not only aimed at carbon, nitrogen or phosphate, but also at the necessary soil structure and the living organisms in the soil. Soils by nature are not an infinite source of water and nutrients. An agricultural soil must therefore be managed. To ensure that the supply of nutrients remains in order.

To ensure that sufficient water is available and roots can grow into the depths without any worries. To ensure that the soil life is active to stir up the soil, to release nutrients and to prevent disease-causing organisms from emerging. This requires a complex interplay of fertilization, cultivation plan, drainage and soil management. Without fertilizer, the soil becomes barren.

Without drainage, the soil can become unworkable and crops cannot grow due to water stress. Without liming, the soil acidifies. The craftsmanship of the entrepreneur becomes visible in this interaction. Mind you, it also requires a continuous reassessment of 'Good Agricultural Practice'. Because the environment changes.

There is an increase in scale, climate change, crop breeding, and machines and equipment are becoming larger and more diverse. And it is precisely in this reassessment of Good Agricultural Practice that there are still major questions, in particular with regard to soil structure and biology: what is the minimum required to keep our agricultural soils in top condition?

An agricultural soil has limits
An optimally managed agricultural soil can also have negative effects on the quality of the environment. Excessive fertilization in the past has contributed to the undesirable enrichment of groundwater and surface water with nitrogen and phosphate, a situation that cannot be changed in an instant. A strong uniformity of the landscape and simultaneous agricultural activities (such as fertilising, mowing, spraying and plowing) seems to be linked to the strong decrease in above- and underground biodiversity. Just a few examples that show that the agricultural use of a soil can exceed the carrying capacity of the ecosystem.

An agricultural soil (as well as the agricultural holding) is part of a larger ecosystem and is connected to it. For example, through the transport of water and life above and below the ground. Climate change, for example, results in a longer growing season, which means that the harvest cannot always take place under good weather conditions and the cultivation of a second crop becomes more difficult. Structural decay is lurking, as is loss of nutrients.

Define borders
Precisely because of this connection with the environment, it is important to also set limits for the agricultural use of an agricultural soil. Because of the quality of that environment, but also because of the sustainability of agricultural production itself. Careless use of agricultural soil can in the long run also pose risks to crop production itself.

Certainly if there is a negative feedback loop that affects the soil processes that support crop production. It is even possible that this will lead to irreparable damage. This includes the effects of deep plowing, the accumulation of toxic substances, subsidence due to peat degradation or the loss of fertile topsoil due to erosion or bank erosion.

More energy in tillage
Every soil has natural boundaries, also around agricultural functioning. This aspect has received little attention in recent years. When choosing building plans, the question is rarely asked: 'is the soil here suitable for this building plan'? Practical experiences in Flevoland and Brabant show that tillage costs more and more energy, that crop yields are limited by subsoil compaction and that the increase in crop yields is leveling off.

The yields realized in practice do on average approach the maximum yield, but large differences between companies and plots show that profit can be achieved through sustainable soil management. Customization is the keyword here. Sensor technology and precision agriculture are increasingly making it possible to visualize this variation, making it possible to tailor-make management. And this does not only concern operational management, but also system changes related to construction plan and soil management. It is very likely that this will improve the use of land, water and nutrients.

An agricultural soil can feed more than crops
In 2020, various social and economic tasks will be translated into soil management, also for tasks that are not necessarily in line with a more sustainable agricultural soil. For example, the task to store substantial amounts of carbon in the Dutch soil (for the climate), the task to prevent nitrate leaching into the groundwater (for the quality of groundwater), the cultivation of biofuels (for the climate) and late mowing. or inundating plots to give meadow birds a place in the spring to forage or nest (for nature management).

Or when using agricultural plots to store excess water in emergency situations, so that flooding in urban areas is prevented (for water management). Something similar can be seen in the implementation of the manure policy: the limit values ​​for an agriculturally optimal P-state of the soil are artificially stretched in order to create more space for use and thus keep the manure problem manageable. The soil plays a role in all these tasks. They are soil services that are not by definition an extension of an agriculturally optimal soil.

In practice, these tasks mean that sacrifices are made in the field of agricultural production or agricultural sustainability. Many measures have a direct or indirect negative effect on the agricultural area or the yielding capacity of the soil. Or measures increase the leaching and run-off of nutrients, such as rewetting or high permissible P levels.

Integrity and customization are two crucial concepts that can make it possible to do the right things in every place. This is elaborated very nicely in the concept of the Opportunity Map: let every entrepreneur look at which assignments he/she can contribute based on his own company, make this contribution transparent and develop new revenue models to reward this contribution.

The agricultural soil needs more and more?
I don't have a clear answer to this question yet. I see that the requirements are increasing and that more and more will be demanded of the craftsmanship of the entrepreneur. Not only from politics, but also from the market. Demand from the market is growing, both in terms of quantity and quality (health). Locally, more and more issues relating to water quantity and quality, nature and agriculture, processed and unprocessed manure, energy and soil, biodiversity and climate are strongly linked in so-called business plans. For soil and water, for soil and nature, for soil and manure. In my view, this is a positive development, because the potential of the soil is maximized only through customization.

How that will be embedded within larger economic developments is still difficult to foresee. Will all land soon be managed by financial funds, creating more room for sustainable investments in soil quality? Will legislation and regulations regarding manure policy overrule all entrepreneurial freedom with 'voluntary' measures? What role will non-agricultural goals play in this? It's still coffee grounds to watch.

Soil quality is key
What I do see is that customization and goals are central to all these issues. I see these developments in, for example, the new GLB, the Delta Plan for Agricultural Water Management, (ground) water and soil management in the province of Brabant, Agricultural Nature and Landscape Management and the lease policy.

All in all, the quality of the agricultural soil is central. And that's beautiful. Here – ie on the agricultural plot – it becomes clear what opportunities there are to contribute to both the food issue and social challenges. And here entrepreneurs take action for a soil that actively contributes to the quality of the living environment. And in this commitment lies the future of sustainable agricultural soil. 

Gerard Rose

Senior project manager in soil, water and agriculture at the Nutrient Management Institute (NMI).

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