Wind erosion is best controlled by keeping a protective soil covering with crop residues or a growing cover crop. Maintaining standing crop residue is important to reducing wind velocity at the soil surface and to trapping soil particles. Stover removal could eventually result in less soil aggregate stability and reduced size making the soil more erodible. Soil Water. Crop residue affects soil water by reducing evaporation, catching snow and reducing runoff.
Soil water loss associated with increased stover removal may be the greatest short-term cost of corn stover harvest.
Under water limiting conditions, a corn crop is expected to produce approximately 7 bushel of corn per inch of available water. Soil water losses to evaporation may be increased by 1 to 5 inches, depending on the amount of residue left in the field Figure 1. The snow trapping effect of erect crop residues may also equal one or more inches of water.
Good ground cover often will result in reduced runoff and increased infiltration for further improvement in soil water availability. In water deficit situations, the reduced soil water conditions with stover harvest could often result in yield decreases of more than 40 bushel per acre the following year. In irrigated situations, pumping costs will be increased. Some of the negative effect of stover harvest can be overcome with regular manure application so nutrients are returned to the soil.
Manure is highly variable but the amount of carbon added to the soil with an application of 10 tons per acre of feedlot manure, dry weight, may be similar to the carbon removed in the harvest of 5 tons of stover.
Manure application is valuable for improving soil physical properties, resulting in improved water infiltration, reduced runoff and reduced erosion. Biomass can be stored after harvest in several ways including on-farm open-air, on-farm covered, or storage in a centralized covered facility. Open air storage could be unprotected on the ground or on crushed rock or covered by reusable tarp.
The covered storage could be a pole frame structure with open sides on crushed rock or it could be an enclosed structure on crushed rock. The loss in biomass is highest when biomass is left unprotected and lowest in the enclosed structure. These losses depend on the number of days the biomass is stored and need to be weighed against the costs of installation, land, labor, and materials as well as the biomass quality that is needed by the bio-refinery.
A centralized covered storage facility could be shared by many farms but would require producers to incur biomass handling and transportation costs to move the biomass from their farms. The optimal choice of storage facility is likely to depend on the volume of biomass and the length of time that it has to be stored, the price of biomass, the quality of biomass required, and the weather conditions within the region.
Tables 1 and 2 summarize a range of different scenarios for stover production and their associated break-even stover prices, or the minimum price the farmer would need to receive to justify harvesting the stover residue on the farm. These results suggest that farmers who have the opportunity to market corn stover to a bioprocessing facility may have incentives to use no till over conventional tillage practices. Comparing the continuous corn rotation to a corn-soy rotation assumes higher corn and, therefore, stover yields.
This also increases the variable costs associated with stover harvest, but ultimately result in lower breakeven stover prices. However, under both tillage practices the breakeven stover price is lower with the corn-soy rotation. This suggests that the ability to sell stover may not provide incentives to farmers to switch to crop rotations that are more corn intensive.
Table 2 summarizes the same scenarios for a lower productivity farm with expected corn yields of bushel per acre in a corn-soy rotation and bushels per acre in a continuous corn rotation. Here, the lower corn yields reduce the amount of stover that is harvested and available to sell by the farmer. While the lower stover yields result in lower variable costs of nutrient replacement and harvest, the net effect is an increase in the breakeven stover price in all four management scenarios.
Similar to the high productivity case, no till practices are associated with a lower breakeven price for stover. Again, this suggests that the ability to sell stover may incentivize farmers to adopt no till practices over more conventional tillage.
Also similar to the high productivity case, the breakeven price of stover is higher for the continuous corn rotation compared with the corn-soy rotation, suggesting that stover removal may not lead to more intensive corn rotational practices among farmers. The use of corn stover for bioenergy is appealing since it does not divert land from food crop to fuel production or require investment in dedicated feedstocks by farmers and biorefineries.
However, its production does require additional costs of harvesting, baling and storage and additional fertilization expenses to replace nutrients removed with the residue. The profitability of harvesting corn stover will depend on whether the price of biomass is high enough to cover these additional costs.
Our estimates show that total production costs decline as the harvestable yield increases, implying lower break-even stover prices. This can create incentives for harvesting stover from fields that use no-till systems where residue removal rates can be higher, and may even create incentives for farmers to switch from conventional tillage to no-till systems if the costs associated with switching tillage practices are lower than the potential for more profitable stover removal.
Higher potential profits can also create incentives to increase residue removal rates above those considered here. However, this could have adverse consequences for long term soil fertility as well as contribute to loss of soil organic matter and soil erosion. In contrast, our estimates do not suggest a financial incentive for farmers to switch from corn-soy rotations to more intensive continuous corn rotations.
Using this grain yield, it is estimated that there would be 4. Likewise, a bushel per acre corn crop would produce 4. Thus, varying corn grain yields will result in varying corn stover amounts available for harvest in different crop years.
The amount of stover that can be removed is a factor of how much stover is produced, the soil erosion potential, and the tillage system used.
Soil health is an important component that needs to be maintained to ensure high productivity. Degradation of soil health over time can limit the productivity of the field. Soil health is determined by several factors, including soil organic matter, soil compaction, soil structure, water infiltration, and water and wind erosion.
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