Doctoring a diseased, unproductive soil

When you are tired or hungry, you’re not as productive. You may need to rest or eat. If you push yourself too far, you may get ill. Soil gets tired and hungry, too. How do growers know that? When the fields are not as productive or maybe when yields are down, or diseases infect the plants. The soil can become too compact. It can lack nutrients needed to grow good crops. It may be more prone to erosion or have other physical problems.

Leaving a field fallow, or resting it, means the field is empty for a season or more. The field does not provide income for the grower but the continued fertilization, or feeding, is expensive. A bare field also runs the risk of erosion. Conservation agriculture uses alternative methods to fallow and fertilization to revive soil while still nurturing the overall environment. Just like a doctor prescribes different treatments for different patients, scientists often recommend different methods for returning soil to health, depending on the soil’s characteristics.

Lars Munkholm and research teammates at Aarhus University studied the impact of conservation agriculture techniques over a span of 11 years on two different farms. The fields they studied are in Denmark, and have sandy loam soils. An ideal soil for farming is usually a type of loam, with a good mixture of sand, silt, and clay particles. But sandy loam soils have less clay to hold the soil together. “Very few Danish soils have greater than 15% clay in the topsoil,” Munkholm observes. “The clay content varied a bit at both farm sites, which significantly affected a range of soil properties. The studied soils were probably too sandy as compared to the ‘ideal’ situation even though they are very productive.”

The typical Danish farmer needs to successfully grow food and feed on these soils, making this study important for the nation’s agribusiness industry. A further challenge for Danish farmers with regard to no-till or reduced till is the humid environment. “Denmark is located in a cool and humid climate where soil compaction is a major problem,” says Munkholm. “Intensive soil loosening is typically needed to aerate the soil and stimulate drying of the surface soil. However, there is a steadily increasing interest in reduced tillage and no tillage in Denmark.”