Soil aggregates, aggregate-associated carbon and nitrogen, and water retention as influenced by short and long-term no-till systems

Abstract

No-till (NT) management can improve soil aggregate formation and stability, porosity, and organic carbon (SOC) through the addition of crop residues and less soil disturbance. However, conventional-till (CT) can deteriorate soil structure and cause loss of SOC. This study aimed to quantify the impacts of long-term (NTL) and short-term NT (NTS) on changes in soil aggregate stability, aggregates associated SOC and total nitrogen (TN), bulk density (ρb), glomalin related soil protein (GRSP), pore-size distribution, and water retention compared to the long-term CT treatment at three different locations (Garretson, Crooks, and Beresford). The treatments included: CT (>20 years), NTS (<7 years), and NTL (>25 years). The mean weight diameter, geometric mean diameter, and wet aggregate stability of NTL were greater than the CT at Garretson and Crooks. Long-term NT had a significantly higher concentration and preservation capacity of SOC under different aggregate fractions than the CT treatment. The NT reduced soil ρb compared to the CT treatment at all the three sites for 0−10 cm depth. At Crooks and Beresford, the SOC was 33.3 and 13.7 % higher under NTS compared to that under CT, respectively, at 0−10 cm depth. The GRSP content in bulk soil was significantly higher under NTL and NTS treatments compared to that under CT at Garretson and Crooks. At saturation (0 kPa), the NTL had significantly higher (p < 0.05) soil water retention compared to the CT at all three sites. The NTL increased the proportion of coarse and fine mesopores and had a significantly higher proportion of >4, 2, and 1 mm aggregates than the CT at Crooks and Beresford. These results demonstrate the short- and long-term beneficial effects of the NT treatment on soil water retention and physical quality compared to the CT treatment.