Conservation Tillage
- Objectives:
- Increase understanding of the benefits of conservation tillage.
- Increase understanding and application of best management practices.
- Key Points:
- With conservation tillage, at least 30 percent of the soil surface is covered with crop residue after planting.
- Maintaining residue on the soil surface increases water infiltration, reduces erosion, increases organic matter, reduces weed pressure, saves and reduces costs.
- Best Management Practices with regard to soil compaction, fertilizer application, weed control, roller choppers, closing wheels, planting moisture, water, earthworms, stalk spreaders and narrow rows are essential to conservation tillage.
- Assess your knowledge:
- Define conservation tillage and list its benefits.
- Explain how organic matter affects soil compaction with regard to conservation tillage.
- Describe how tillage affects weed control.
- Explain how conservation tillage reduces runoff.
- Discuss the implications of the best management practices for conservation tillage on corn, sorghum, cotton and wheat.
Because of increased crop production costs, most farmers have to re-evaluate how they till and consider conservation tillage practices. With conservation tillage, at least 30 percent of the soil surface is covered with crop residue after planting. Maintaining residue on the soil surface increases water infiltration, reduces erosion, increases organic matter and reduces weed pressure. Economic advantages also result from having less labor, less fuel, fewer repairs and less maintenance, better field accessibility, lower capital investment and lower equipment horsepower requirements.
- Fundamental Best Management Practices for Successful Conservation Tillage
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Soil compaction
The primary cause of compaction comes from heavy equipment traffic crushing air spaces out of moist soil. Top soils typically contain approximately 50 percent of pore space by volume. Pore space may be filled with water or air; so, when weight is applied to a moist soil, the soil aggregates are crushed, and some of the pore space is destroyed. Traffic patterns must be controlled, and proper tire pressure on equipment must be maintained. Generally, the potential for compaction increases as the percent of clay in the soil increases and as the organic matter content decreases. Reduced tillage leaves residue on the soil surface, which decreases the rate of decomposition and increases organic matter in the surface horizon.
Fertilizer placement and application
Surface applications of fertilizer can result in nitrogen loss from volatilization and cause phosphorus and other immobile nutrients to accumulate near the soil surface. Nutrient deficiencies are likely to occur in no-till or stale seed beds.
Because placement and timing of phosphorus applications are important, thefollowing practices are recommended:
- Phosphorus should be applied before or at planting to ensure that it is available early in the season.
- In corn and sorghum production, it is important to apply a starter fertilizer or place all phosphorus fertilizer close to the developing seedling to prevent nutrient deficiencies.
- Where a starter or a well-placed high-phosphate fertilizer is used, grain crops grow better and mature faster although yields may not be higher. This is also true if you use a pop-up, or seed placed fertilizer, that is applied directly to the seed.
- While pop-ups have not helped cotton, they are more likely to increase yield and to establish stands quickly in grain crops. The amount of phosphorus in the pop-up should be subtracted from the total amount that is needed for the crop to prevent over-fertilization.
- To slow stratification, phosphorus and other immobile nutrients should be banded 5 to 6 inches below the surface where possible. Placing the nutrient close to the planted row will also increase fertilizer efficiency.
Weed control
Weeds compete with the crop for moisture, fertilizer and light and can be greatly reduced if the soil is not tilled. It is easier and generally better to control weeds under no-till and reduced tillage systems. These are some other practices that help with weed control:
- Use herbicides in the winter and during the growing season.
- Applying transgenic technology, such as Roundup Ready® and LibertyLink® products, has made conservation tillage much easier.
- A hooded sprayer is important for weed control in sorghum (particularly for grass control) and in cotton (for lay-by applications of herbicides).
- Pre-emergence herbicides are still important. Weed control before planting prevents weeds from depleting valuable soil moisture and from creating a haven for insects.
Roller choppers or rolling stalk choppers
Stalk choppers are found to be more effective in continuous cotton crops or where ridge-tillage is done farther north in Texas. The stalks are left standing all winter and spring to protect the soil against wind erosion, and are chopped in late winter or early spring when beds are remade. These choppers proved to be of no extra benefit in no-tillage in south Texas. They were ineffective in breaking surface compaction, but did a good job of chopping residue. Residue managers on the planter adequately removed un-chopped stalks at planting time.
The closing wheels or closing system
Using closing wheels or a closing system on the planter might mean the difference between a good stand and a poor stand. Because of varying conditions at planting, you should have several types of closing wheels. Schlagel Manufacturing wheels and closely spaced spiked closing wheels have been the most effective in tests with loose soil under most planting conditions.
It is important to break any side wall compaction caused by disc openers, to firm the seed in the bottom of the seed trench and to leave the surface slightly roughened to prevent crusting and baking. The seed must be firmed into moist soil and properly covered (as with conventional tillage) to achieve a good stand. Double disc planters tend to leave smooth, slick side walls that reduce root penetration.
Planting moisture
If a small bed is made before the onset of winter, moisture should be more consistent at planting time. You can then use a bed to remove dry soil and will not need to plant “in a hole” to find moisture.
Make sure the bed is not a high ridge, but rather only a low, rolling hump formed without burying residue. Meanwhile, keep the bed covered with as much residue as possible. Flat planting and “busting out” the dry soil on the surface to get to moisture will cause deep planting in a trench. It also will bury the seed if a heavy rain comes before stand establishment. Try to maintain as much residue on the surface as possible to increase water penetration.
Water
Covering the soil with residue rather than tilling it clean improves water infiltration. The impact of rain on base soil destroys small aggregates, or clods, causing the soil to seal over. Residue breaks the impact of rain drops, “wicks” or moves moisture into the soil, and reduces runoff.
Earthworms
Just because a field is under conservation-tillage does not automatically mean you will have a large number of earthworms, which can do a tremendous amount of tillage. Their populations rise and fall with moisture, number of roots and amount of organic matter (their food source) in the soil. Water soaks into the soil through worm tunnels, which also helps soil gas exchanges.
Stalk spreaders
Stalk spreaders are important for distributing the residue rather than pushing it into wind rows. This is particularly true for combines with larger headers, but less important for smaller combines.
Narrow rows
Making rows 30 inches instead of 38 to 40 inches can help shade the soil faster (close the crop canopy faster) and reduce weed growth. In research around the state, sorghum yields have consistently been higher with narrow rows.
- References