Biochar and manure alter few aspects of prairie development: A field test

Biochar and composted manure can impart benefits, such as improved nutrient cycling, increased productivity, and carbon sequestration, when they are applied to agricultural soils. There are limited data, however, on how these additives effect mixed perennial communities. We compare plant and soil community responses by using factorial applications of Royal Oak biochar (0%, 2.6%, and 5.2%) and composted manure (0 and 4.5 kg m−2) in a tallgrass prairie restoration in Iowa. We found that biochar contributed to ecosystem function by increasing total carbon in the soil. We also found that biochar increased plant species richness and the 5.2% biochar treatment increased the biomass of plant species in the seed mix. Phosphorus cycling was altered by both the biochar and manure treatments; in soils with manure, biochar addition reduced phosphorus (P) availability compared with the control, but in soils without manure, biochar increased P availability. Belowground, the biochar and manure treatments affected the relative density of gram-negative bacteria, the relative density of actinobacteria, and root colonization by mycorrhizae. Contrary to our hypotheses, however, the biochar and manure treatments did not change total plant cover, total aboveground peak biomass, overall plant community, soil pH, inorganic nitrogen concentrations, extractable soil K, plant tissue N, soil microbial biomass-carbon, nematode density, and overall microbial community composition. Overall, we found several benefits and few externalities associated with biochar and composted manure addition to tallgrass prairie. However, these products can vary considerably and their interactions with soil, plants, and microbes can be situation specific. More study is needed to identify the characteristics of biochar that can affect mixed perennial communities prior to widespread use.