Root Traits of Cover Crop Monocultures and Mixtures.

The 2015-2016 Cover Crop Survey from SARE reports that 83% and 51% of farmers use cover crops to increase soil organic matter (SOM) and to integrate diverse root systems. If farmers are planting cover crops to build SOM, cover crop selection should be evaluated based on root traits in addition to aboveground biomass production. Given the growing popularity of cover crop mixtures, we compared the root traits of cover crop mixtures with their component monocultures to test whether cover crop mixtures could improve root biomass production and root distribution. The cover crops were planted in rows spaced 17.8 cm apart following a wheat crop in August 2016 in central PA. In November 2016 and May 2017, we sampled cover crop treatments at in-row and between-row locations and measured root biomass, root distribution, and root C/N ratio. The four cover crop treatments were three monocultures: triticale, crimson clover, and canola and a five species mixture that contained all three species. In fall and spring, triticale had approximately three times more root biomass in the between-row space than crimson clover, canola, and the 5 species mixture from 0-40 cm. By spring, triticale exhibited greater root biomass than the other cover crop treatments. Although triticale produced the least aboveground biomass in fall, it displayed the highest root to shoot ratio of .85. Each cover crop treatment had a characteristic proportion of >2mm and <2mm roots. The five species mixture produced more <2mm roots than canola in surface layers. Understanding the root traits of different cover crops has the potential to improve cover crop mixture design for enhanced SOM building.