The Effects of Different Cover Crop Species on Soil Aggregate Stability.

Cover crops have the ability to improve soil aggregate stability which results in better infiltration and retention of water in the soil. A field experiment was conducted at the Agronomy Center for Research and Education (ACRE) - Purdue University to examine the effects of four cover crop species on soil aggregate stability. The experiment included five treatments: four cover crop species (teff, pearl millet, hybrid sorghum sudangrass, and cowpea) and control (fallow plot) arranged in a randomized complete block design. All cover crops were planted in late May, 2010. Soil samples for aggregate stability analysis were taken on August 12, and November 01, 2010, using a flat-square-cornered spade. The Wet-Aggregate Size Distribution method was used to determine the aggregate stability of the soils, expressed as mean weight diameter (MWD).

The results of our study showed that there was no significant improvement in soil aggregate stability by cover crop species in August. However, the aggregate stability analysis in November showed that all cover crop species resulted in significantly greater aggregate MWDs than control plots (P < 0.05). Teff produced significantly greater aggregate MWD (4.5 mm) than all other treatments (P < 0.05), followed by sorghum sudangrass (4.0 mm), pearl millet (3.8 mm), cowpea (3.6 mm) and control plot (3.2 mm). The results of our study suggest that soil aggregate stability under cover crops improves over time, and grass cover crops with fine fibrous root structure can improve soil aggregate stability better than taprooted cover crops.