Grain straw contains a type of silicon that increases the soil's water retention capacity. This effect of silicon was discovered by scientists in field experiments on drought-prone sandy soils. They argue that incorporating straw residues after grain harvest is beneficial because otherwise, the soil content of this amorphous silica decreases and the soil moisture content decreases.
According to them, water holding capacity is becoming increasingly important as growing seasons become drier due to climate change. Cereals and grasses absorb a significant amount of silicon from the soil. This silicon is stored as amorphous silica, a type of silicon dioxide.
Amorphous silica increases crop resistance to diseases, pests, and other stresses. This silica returns to the soil through straw residues and benefits the next crop. Amorphous silica from straw residues improves the soil's water retention capacity. Crops have more water at their roots as a result, making it easier to bridge dry periods.
This property of amorphous silica was discovered by scientists in experiments on drought-prone sandy soils in eastern Germany. According to the researchers in the popular science magazine Plant nutrition courier, incorporating straw residues after grain harvest is a good way to improve the soil's water holding capacity. They also discovered that spring wheat evaporates less water on soils rich in amorphous silica. The most recent findings of this study into the role of amorphous silica in soil were published in the digital magazine Plant nutrition courier.
In sand and clay minerals, amorphous silica differs from silicon. This silicon cannot be absorbed by plants and does not weather well. Farmers who remove straw deplete the soil's amorphous silica content. However, regular liming of the soil masks this loss of amorphous silica. Increasing the pH of the soil speeds up the biodegradation of siliceous crop residues and other organic matter.
Crops absorb the released silica, and it eventually disappears from the field. As a result, the soil's amorphous silica content is decreasing. According to German scientists in the Plant nutrition courier, this will reduce the soil's water-holding capacity in the long run. They value water holding capacity because growing seasons are becoming drier as a result of climate change.
Scientists from the Leibnitz Centre for Agricultural Landscape Research, as well as the universities of Bayreuth and Potsdam, conducted silica research. They have tested industrially produced amorphous silica as a soil amendment in addition to grain straw. This material has the same effect as amorphous silica derived from straw, but it is many orders of magnitude more expensive.
The researchers have yet to discover an affordable industrial alternative, as well as a clean waste stream containing sufficient amorphous silica. Cereal straw is thus by far the most affordable source of this moisture-retaining silica.
