Part 1, Section 1: Soil Management
TILLAGE MANAGEMENT
No-tillage Management Intensity for Corn in Pennsylvania
No-till with maximum crop residue cover has many benefits. Adaptation of no-tillage crop production, however, has not been equally successful in all soils and climates. To give farmers direction as to the challenges they may encounter with no-till compared to other tillage systems, we developed no-till management intensity zones for corn in Pennsylvania based on results from long-term experiments in the Midwest and Northeast regions of the United States (Figure 1.1-6). These zones were developed assuming continuous corn cultivation in which all crop residue is left in the field. When moving from Zone 1 to Zone 6, there are increasing challenges to no-till corn production. In the zones with more challenges, modifications to equipment or crop rotations may be necessary to obtain comparative yields with no-till as with conventional tillage systems. The map created is based on the available soils and climate information, and is generalized to accommodate the scale of the map. There will be many exceptions that could not be captured in this map because of local soil and climatic variations.
The classification we developed for the Agronomy Guide employs the following criteria:
- Growing degree days (GDD). If the area has less than 2,800 GDD for corn, it is less conducive to no-till because slow warming of soils in spring is likely to reduce yields. While slow early growth of no-till corn is also common in the areas with more than 2,800 GDD, this is not likely to result in differences in yield.
- Drainage. On soils that are less than moderately well drained, no-till and mulch till usually result in yield reductions compared to conventionally tilled corn. If more than 20% of the area consisted of hydric soils, the area is classified as having poor drainage.
- Slope. If more than 30% of the land has slopes exceeding 8%, the area is classified as having high erosion potential. On these soils, high-residue systems such as no-till and mulch till have an advantage because of erosion control.
- Water-holding capacity of the root zone. If the water-holding capacity of the root zone is less than 6 inches, high-residue tillage systems such as no-till and mulch till have an advantage over conventional tillage because of their ability to conserve water.
- Rock fragment content. When an abundance of rock fragments is present, an area is judged to be less suitable to tillage. No-till has an advantage on these soils. High rock fragment zones are those where more than 30% of the area was mapped as sandy skeletal or loamy skeletal soils.
Zone 1
Most soils in this region are highly conducive to no-till. The growing season exceeds 2,800 GDD for corn, and the soils are predominantly well drained. The lower soil temperatures in spring under no-till should not lead to yield reductions in this zone. Erosion is a serious threat on these soils, many of which have slopes exceeding 8%. No-till helps to maintain the crop residue cover to limit erosion. The waterholding capacity of these soils is low, and maintaining permanent crop residue cover helps conserve water. Many of the soils in this zone contain high amounts of rock fragments. No-till helps to avoid the need of extensive rock picking.
Zone 2
Most soils in this zone are very suitable for no-till. The growing season exceeds 2,800 GDD for corn, and soils are well drained. The lower soil temperatures in spring under no-till should not result in yield reductions in this zone. Erosion is not as serious a threat on these soils as in Zone 1. The water-holding capacity of these soils is low, and maintaining permanent crop residue cover helps conserve water. Many of the soils in this zone contain high amounts of rock fragments. No-till helps to avoid the need for extensive rock picking.
Zone 3
Most soils in this zone are very productive and have few constraints for any tillage system. The growing season has more than 2,800 GDD for corn, with the exception of some of the more northern areas and those at high elevation. The soils are commonly well drained. Slopes are mostly less than 8%, limiting the danger of erosion. Most of these soils have high water-holding capacity, so the moisture-conserving benefits of no-till are of moderate importance. Rock fragments are rare and pose no great problem to tillage. Adjustments to equipment and careful crop rotations can make no-till successful in those areas of this zone where the growing season has less than 2,800 GDD for corn. Row cleaners and/or use of zone tillage to clean the row when planting, enable quicker warm-up of soils with high residue cover. Rotating crops producing a lot of non-fragile crop residue (such as corn) with crops producing lower quantities of fragile residue (such as soybeans) is another way to obtain equal yields with either no-till or conventional tillage.
Zone 4
This zone is located in the colder parts of the state with a growing season that has less than 2,800 GDD for corn. Cold soil temperatures are expected to depress early growth in no-till compared to a conventionally tilled corn. The soils are mostly well drained. The slopes are mostly less than 8% and have a reduced danger of soil erosion. However, these soils also have low water-holding capacity and tend to be droughty. Rock fragment content can be high in these soils. The moisture-conserving benefits of high residue cover should pay off and result in equal or higher yields for no-till crops compared with tilled crops. Row cleaning devices or rotations of high-residue with low-residue producing crops may help soils warm up faster in the spring in no-till.
Zone 5
This zone is in the colder parts of Pennsylvania with less than 2800 GDD for corn. The soils are mostly well-drained. Slopes are often greater than 8%, and the erosion potential is high. Crop residue cover should be maintained for soil conservation. The water-holding capacity of the soils in this zone is mostly high, so water conservation benefits due to no-till are not as crucial as in Zone 4. Rock fragment content can be high in these soils. Moving some residue prior to planting to enable warm-up of the soils in the spring while maintaining good residue cover for erosion control is recommended. Zone tillage seems to be a promising tillage system for this region. Row cleaners on the planter unit may help to improve soil warming in spring. Planting on the contour is recommended for erosion control.
Zone 6
This zone covers areas with both more and less than 2,800 GDD for corn. Most soils in this zone suffer from poor drainage. Slopes are generally less than 8%, and erosion potential is therefore moderate to low. The water-holding capacity is moderate to high. Rock fragment content is mostly low to moderate. These are the most challenging soils for high-residue tillage systems such as no-till and mulch till. The disadvantages of conventional tillage, such as erosion, water losses, and rock picking, are less pronounced when the soils are on relatively level land. It is possible to make conservation tillage successful in this zone, but extra effort is needed to achieve drying and warming of the soil. Zone tillage and row cleaners help to prepare a zone that is clean of residue in no-till. Rotation of high- and low-residue producing crops is an alternative means to boost yields on these soils with no-tillage.