The Effects of Phosphorus Application and Cover Cropping on Soil Aggregate Stability



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Soil aggregation is the clumping of multiple particles, forming one individual piece of soil. The stability of these aggregates impacts many factors such as preventing erosion, maintaining nutrients, and holding water. This study is conducted in the field at the Kansas Agricultural Watershed (KAW) and is testing the effect of three phosphorus applications, either fall broadcast, spring injection, and none, as well as having cover crops or no cover crops, on the soil aggregate stability. Three samples from 18 plots total are taken of the topsoil (0-5cm) and subsoil (5-10cm.) Next, when samples are dried, the Slakes application is used on a phone or tablet with a camera. The phone is held by a stabilizing device with the camera facing down. Three aggregates of a sample are taken and placed on a petri dish, then placed in a well-lit area that the camera can focus on. After setting up, water is introduced to the petri dish, submerging the aggregates. A timer of 10 minutes is started on the application. When the timer ends, the application produces a number, giving you the Slakes Stability Index, measuring aggregate stability in water. This process is repeated for all 54 samples. Using an SAS analytics software, with a two-way analysis of variance, the data shows all three factors of individual cover crops, individual P application, and the combination of both, have no significant difference regarding aggregate stability. This means there is no need to add either input to maintain healthy soil aggregation.



soil aggregation, Kansas Agricultural Watershed, Slakes Stability Index, phosphorus, cover crop