Aggregation, carbon, nitrogen, and natural abundance of ¹³C and ¹⁵N in soils under no-tillage system fertilized with injection and surface application of pig slurry for five years

Abstract

Injection of pig slurry (PS) into soils under no-tillage system (NTS) is more efficient for improving soil chemical and physical attributes, and reducing C and N emissions, than surface applications. This study evaluated the effect of using injection and surface application of PS, compared to NPK and control treatments, on the soil aggregate, C and N contents, and isotopes ¹³C and ¹⁵N. The NTS consisted of rotations of summer (maize) and winter (black oat and wheat) grasses from 2011 to 2015. The treatments were PS injected into the soil (PS_I), PS applied on the soil surface (PS_S), chemical fertilization (NPK), and control (CTRL). The following soil properties were evaluated in the 0–5, 5–10, and 10–20 cm layers: aggregate stability (geometric mean diameter – GMD; aggregate mass distribution); total organic carbon (TOC) and total nitrogen (TN) in macroaggregates (8.0–0.25 mm), microaggregates (<0.25 mm), and bulk soil (<2.0 mm); and isotopes ¹³C and ¹⁵N in macro and microaggregates. The application of PS_I improved the soil physical attributes, presenting higher GMD (0–5 cm) than the PS_S, NPK, and CTRL treatments. In the 5–10 cm layer, the PS_I treatments were more efficient in increasing the GMD and macroaggregate mass than the NPK. PS_I also was more efficient in increasing TOC and TN when compared to PS_S, and generated a higher GMD, which are protectors of these elements in the soil. The natural abundance of ¹⁵N denoted the lower soil organic matter decomposition in the PS_I treatment when compared to the PS_S. The natural abundance of ¹³C showed less-negative values in macroaggregates than in microaggregates, denoting that the soil management practices and crops used (grasses) affected positively the abundance of ¹³C. After seven applications of PS in maize-oat-wheat rotation in NTS, the application of PS_I was more efficient in improving the soil physical and chemical attributes than the application of PS_S.

Keywords:

• Injection of pig slurry
• macroaggregates
• soil organic matter
• isotopic composition

Acknowledgment

The authors are grateful for the financial support of the Fundação Agrisus (PA 2494/18).

Disclosure statement

No potential conflict of interest was reported by the authors.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.