Soil Carbon and Nitrogen Fraction Accumulation with Long‐Term Biosolids Applications

Abstract

global sustainability depends on the recycling of organic wastes, containing carbon and plant nutrients, back into food production. Biosolids are capable of building total soil organic matter, but their ability to build stable organic C and n fractions is less well understood. The sequestration of stable soil C and replacement of energy-requiring commercial fertilizers both have implications for greenhouse gas mitigation. Our aim was to assess the effectiveness of biosolids amendments to store labile and stable soil C and n fractions while supplying crop n needs. Three rates of anaerobically digested biosolids were incorporated following wheat harvest every 4 yr in a wheat-fallow system over 20 yr, and compared to a no-fertilizer check and a standard commercial fertilizer treatment. Increases in total soil C and n correlated to cumulative application rates of total and acid-resistant, non-hydrolyzable (nH) C and n, with 91% of added biosolids C efficiently retained in soil. The soil accumulated light fraction (LF) C and n in biosolids treated plots, whereas the LF pools of the control plots decreased and LF pools in the commercial fertilizer plots stayed relatively constant. Total soil n correlated with cumulative biosolids n, with 35% of added biosolids n retained in the soil of which only 4% was stored in the soil nH n fraction. Anhydrous ammonia increased wheat yields by 27% over the 0-fertilizer check, without increasing soil n. Biosolids markedly elevated total, stable and LF soil C and n pools in semiarid conditions, while maintaining comparable wheat productivity to commercially fertilized wheat-fallow.

Soil carbon response to long‐term biosolids application

“…In our study, long‐term (20‐yr) biosolids application increased SOC in the top 30 cm of soils in three agroecosystems in California. This finding is consistent with studies in other regions that have documented beneficial reuse of biosolids as a strategy to sequester C in soils in surface soils (Brown et al., 2011; Hamdi et al., 2019; Nicolás et al., 2014; Pan et al., 2017). There are number of factors that improve SOC in soils, including improvements in soil quality, agronomic productivity, and the enhancement in soil microbial diversity (Lal, 2014).…”

“…Although the benefits of biosolids application are evident in many agricultural soils, most studies sample only the top 30 cm or less of soil (Pan et al, 2017;Pitombo et al, 2015;Stewart et al, 2012;Tian et al, 2013Tian et al, , 2009. There have been relatively few soil C studies that have examined deep soil C, regardless of the management practice examined.…”

Integrating Historic Agronomic and Policy Lessons with New Technologies to Drive Farmer Decisions for Farm and Climate: The Case of Inland Pacific Northwestern U.S.

“…The close proximity offers opportunities for processed manure and biosolids to be imported into this fallow zone, which will reduce fertilizer nutrient requirements. This would also build up the low SOM levels as has been demonstrated in a long-term manure trials at Pendleton, OR (Machado, 2011) and biosolids trials near Okanogan, WA (Cogger et al, 2013;Pan et al, 2017b).…”

Soil Nitrogen Sorption Using Charcoal and Wood Ash

“…The chemical forms of organic matter added and subsequent form can affect the long term soil C and N sequestration efficiency [293]. Wang et al [294] revealed that soil C is the principal energy source to soil microorganisms and enzymes whereas the soil C/N ratio influences their activity.…”