Evaluating ephemeral gully erosion impact on Zea mays L. yield and economics using AnnAGNPS

Ephemeral gully erosion causes serious water quality and economic problems in the Midwest United States. A critical barrier to soil conservation practice adoption is often the implementation cost, although it is recognized that erosion reduces farm income. Yet few, if any, understand the relationship between cost of conservation practice implementation and potential economic benefit gained from erosion control practices, especially as related to ephemeral gully erosion. The objectives of this research are to: (1) evaluate the soil loss and corresponding topsoil depth reduction due to annually ephemeral gully filling; and (2) estimate the economic loss associated with the crop production reduction attributed to topsoil thinning. Surface runoff and watershed sediment yield were flume measured at the approximately 1-ha drainage scale in Iowa. Sediment yield of the developing ephemeral gully was partitioned from measured total watershed sediment loss, by modeling ephemeral gully development with the Annualized Agricultural Non-Point Source Pollution model (AnnAGNPS), and subtracting this soil loss value from the flume measured watershed total. Topsoil thinning in the adjacent area used to fill the ephemeral gully was calculated based on the corresponding ephemeral gully sediment yield. The effect of A horizon thickness on corn yield obtained from published literature was used to calculate the corn (Zea mays L.) yield reduction due to topsoil thinning. Ephemeral gully erosion negatively impacts farm economics in the long term and implies that soil conservation measures should be carefully designed and well maintained. However, this evidence suggests that costs associated with establishment and use of structures such as grass waterways to minimize or eliminate ephemeral gully formation will not be recuperated in the short term through yield potential maintenance.