How can farmers grow crops in more coarse soils?

Particles of sandy soils generally have a mean diameter between 0.05mm and 2mm. They are the largest of soil particle types – the smaller particles are called silt and clay. A soil that is good for farming consists of a mixture of these particles, allowing for healthy crops. Loam is a particularly good type of soil for farms. However, sometimes you must grow food with any soils that are available. That’s the case where I’m doing my research in Germany.

There are even types of soils that are coarser. These “stony soils” contain particles with diameters larger than 2 mm. The particles are actually fragments of rock that haven’t yet gone through the soil formation process.  In some cases, this type of soil can comprise 5-50% of soil in a farm.  

An important aspect of farming in stony soils versus loamy soils is how water moves through soil. As you could imagine, with larger particle soils, water moves more quickly through the soil. That means it isn’t available to plants easily. Loamy soils can hold water better, giving a fairly predictable supply of water to the crops. 

Onions atop coarse soil with the bulbs showing
A farmer’s field in lower Saxony Germany. Onions have shallow, fibrous root systems that allow them to grow in even stony soils. Farmers often adapt their crops to the soil they have in place; amending with compost can increase the types of crops they grow. Credit: Uniyal

Stony soils also don’t hold on to nutrients in the same way as loamy soils. The clay particles in loam – often lack in stony soils – hold and release nutrients and organic matter to plants.  Additionally, the fragments in stony soils can result in faster wear and tear of agricultural equipment.

How can farmers adapt to growing in stony soils?

Farmers study their farms soils before growing a specific type of crop. They determine nutrient content and irrigation scheduling based on their inspections. After getting a rough idea of soil types and conditions, they think about the crop which is generally best suited to their soil. This can even change from season to season – we are seeing this with a warming climate and changes in weather patterns.

Large field of canola (rapeseed)
Winter rapeseed fields nearby the onion farm (above). This can be an alternative crop under water-stressed conditions like stony soils. Credit: Uniyal

To help stony soils be productive, farmers can amend their farm soil with organic matter. Partly decomposed garden compost or straw manure helps hold soil moisture and nutrients during the growing season. Additionally, this organic matter helps to maintain healthy populations of soil microbes, worms and other living creatures in the soil.

In some areas of Germany, farmers have been successful growing winter wheat in stony soils. This is because winter wheat is tolerant to drought and it has a low nutritional requirement. Farmers can rotate this crop with crops that have short root systems– like onions, or parsley.

Wheat kernels in hand
Winter wheat is also a good crop for stony soils. This drought-tolerant crop can thrive in soils that don’t hold water well. Credit: Rafael Maeoka

Adapting what crops they plant, farmers can continue to provide food, while farming in a sustainable way. Even stony soils have hope to feed healthy and tasty plants – like onion, which is the number one consumed vegetable in the world!

Answered by Deep Chandra Joshi, Technical University Braunschweig, Germany

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