Keep Carbon In The Picture: Modifying The Cut And Carry System

By Christopher Graham

Insights from Ethiopia

After a recent trip to Ethiopia, I began thinking about how farming on the steep, terraced hillsides of the rural highlands there might relate to agriculture across the rolling plains of South Dakota. As part of the Farmer-to-Farmer Program, jointly sponsored by USAID and Catholic Relief Services, I had the opportunity to speak with nearly 300 smallholder farmers about fertility and soil health. On its face, agriculture in central Ethiopia could not be more different to that in South Dakota and much of the United States. The former farm on a few acres or less of terraced land straight up the hillside. They have limited access to fertilizer, perform all tillage with oxen, and broadcast their seed. At this point, mechanization of their operations is nearly impossible because of the rugged terrain. Most farmers believe that tillage is essential because their soils won’t retain the early-season rains that the crops depend on. In a sense, their soils are addicted to tillage and the farmers do not have the ability to absorb the yield reductions that are often experienced in the transition to reduced/no-till practices. Most farmers absolutely understand the value of maintaining or increasing carbon in their soils, but many are caught in the age-old ‘cut and carry’ system in which all of the grain/produce is eaten or sold and the straw is removed from the field and fed to animals or used as fuel.

Figure 1. Steep, terraced landscape of the Ethiopian highlands.

S.D. Soil Challenges

In contrast, farmers in South Dakota are entirely mechanized, with many farming hundreds or even thousands of acres in long-term, no-till systems. However, these two seemingly disparate systems do share at least one common feature and that is the farmer’s reliance on animals as an integral part of the farming operation. Moreover, much of the biomass produced in both systems is removed and fed to animals in a separate location. Along with that biomass goes an enormous amount of nitrogen, phosphorus, potassium, water and carbon (among other micronutrients). These are all elements that must be replaced in a sustainable ecosystem. A recent iGrow article pointed out the value of returning crop residue to the soil. The authors note that in every ton of wheat stubble, there are 10 pounds N, 3 pounds P2O5, 31 pounds K2O, and 2 pounds S. The combined value of these nutrients is about $26.00 per ton of wheat stover. This figure, however, doesn’t even begin to encompass the full value of returning residue to the soil when one tries to enumerate the additional benefits from reduced soil erosion, increased soil organic matter and improved soil water retention.

In many ways, both groups of farmers are stuck in the same cut and carry system. As I drive across the state, I see countless bales of hay rotting in neat rows alongside the barn or fenceline. To be sure, the majority of the hay that is baled is used to feed animals during winter months, but there is certainly a sizeable portion that goes unused each year, perhaps as insurance for leaner years to come. But in the meantime, farmers lose the valuable nutrients once contained in that biomass and the value it has on the land.

Figure 2. Aging bales of alfalfa hay. As the decomposition process proceeds, this hay continues to lose its feed value, which could have been more profitably left in the field.