For the last three weeks our team of interns and the Agricultural Water Management team have been busy collecting field research data from our Conservation Learning Lab sites. To gather baseline measurements of soil health, we collected bulk density samples last fall and are in the process of measuring water infiltration and soil aggregate stability.
Both the Story County and Floyd County locations have five fields participating in the project, representing 50-68% of the watershed. We are collecting data from three samples points in each soil type within the field for a total of 36 samples sites per watershed. We will compare these measurements in three years to those taken after the addition of cover crops to all fields and a decrease in tillage (transition to strip-tillage) for half of the fields.
Healthy soil has adequate pore space to receive and retain rainwater. By increasing the infiltration potential of soil, we can reduce runoff and soil erosion during rain events. Healthy soil also has better water holding capacity during periods without rain.
Using the Cornell Sprinkle Infiltrometer, we are looking to find out how much water is able to permeate into the soil. The infiltrometer–essentially a portable rainfall simulator–connects to a 9.5 inch metal ring that has been installed in the ground. We calibrate the infiltrometer to “rain” about 0.5cm/minute within the metal ring.
After recording the time of first runoff, we record the height of the water in the infiltrometer and the volume of runoff every three minutes. We continue this process until a steady state is achieved in the volume of runoff (about an hour).
Each runoff sample is poured into a cylinder for measurement. Calculating the difference between how much water is gone from the infiltrometer and how much has runoff, we can compute how much of the water that has infiltrated into the soil.
Collecting Samples for Aggregate Stability
Aggregate stability is a soil health indicator that provides a measurement of the soils ability to resist erosion, especially from water. It is desirable to have stable aggregates to withstand rainfall and water movement compared to weak aggregates that can seal the surface of the field and decrease infiltration. The weak aggregates can also create a crust that can make it difficult for seedlings to emerge.
Check back for updates as the team begins to process the soil samples that were collected near the infitrometer sites.