Tillage represents a significant part of the cost of crop establishment and growth and, when correctly applied, delivers increased yields.
Tillage is intended to:
• Change the soil structure to meet the requirements of the planted crop.
• Enhance the efficiency of applied nutritional and agronomic treatments.
• Deal with the remaining residue of the preceding crop, when necessary.
If not done correctly, it is possible to incur high tillage costs without providing a positive effect for the crop. Compaction of soil structure is possibly the most significant byproduct of ineffective tillage practices, and of intensive farming worldwide.
A shovel is the most important tool to assist in maintaining good soil structure. Without digging soil profiles to see the current structure, it is difficult to determine how to correct problems. Furthermore, if soil is not in an appropriate state when tillage is carried out, then tillage efforts are unlikely to be entirely successful.
The following surface symptoms may indicate problems with soil structure:
Typical surface ponding (above, left) indicates poor drainage and blocked water movement. Surface capping and ponding (above, right) indicates potential surface cultivation issues.
Note the worked soil is wet, but the capped surface crust is dry. In spring, this can prevent the sufficient drying of the profile, and tillage passes could then damage the wet soil below the crust. Additionally, surface erosion often indicates surface capping and deeper drainage problems.
Much of the damage caused by ponding could be prevented if more farmers employed tillage systems focused on optimizing the land’s ability to absorb water. Many fields have layers about 10-11 inches below the surface, which prevents the penetration of water, causing lateral water flow on or below the surface. This removes valuable nutrients and chemicals that may enter shears and rivers, resulting in erosion.
Plant indicators can often pinpoint soil structure problems. Crops with sensitive root systems clearly illustrate barriers to root growth. The roots to the left have been stunted by a density-change layer, while the roots on the right have grown down into a structured, uniform soil profile. Crop yield can be compromised for the fields with compaction by up to 50%.
Plant indicators include:
• Relative growth differences–often indicates a near surface structure issue at establishment time.
• Leaf-color variations–indicates potential availability of nutrients and trace elements.
• Early senescence–lack of deeper water in a dry summer potentially means deeper compaction.
These should be taken in the light of other field effects (for example, available soil N, trace elements, soil acidity, and general climatic and crop physiological effects).
Indicators at harvest include general crop yield when compared to other similar fields, and relative yield differences in the field when consistently measured. While yield can also be influenced by soil type, plant physiology, and nutrient balance, the combine's yield monitor is a general indicator in determining where further investigation of the soil may be needed.