No-tillage and fertilization effectively improved soil carbon and nitrogen in a subtropical Ferralsol.

The capacity of no-tillage and fertilization to promote soil organic carbon (SOC) accumulation and the impacts of occasional tillage on that SOC are topics of current debates. We quantified (i) the SOC and total nitrogen accumulations resulting from the adoption of long-term (23 years) no-tillage relative to conventional tillage by plowing, (ii) the impact of occasional chiseling every three years on SOC and total nitrogen stocks and (iii) the improvement in SOC and total nitrogen stocks due to normal fertilization relative to reduced fertilization (suppression of P and K application) in a subtropical Ferralsol of a field experiment in southern Brazil. After 23 years under normal fertilization, no-tilled soil stored significantly more carbon and nitrogen than conventional tillage soil, either to 30 cm depth (85.5 vs 71.3 Mg C ha‐1; and 6.12 vs 5.13 Mg N ha−1; P < 0.10) or to 100 cm depth (185.0 vs 163.2 Mg C ha−1; and 11.99 vs 10.32 Mg N ha−1; P < 0.10), which means that no-tillage significantly accumulated 0.60 Mg C ha−1 year−1 and 0.04 Mg N ha−1 year−1 compared to conventional tillage to 30 cm depth, and 0.93 Mg C ha−1 year−1 and 0.07 Mg N ha−1 year−1 to 100 cm depth. Those results indicate the capacity of no-tillage to promote SOC and total nitrogen accumulation in this Ferralsol, despite its aboveground residue being not significantly higher than that in conventional tillage (9.22±0.46 vs 8.47±0.44 Mg DM ha−1 year−1, normal fertilization), and also indicate that it might be useful to assess SOC and total nitrogen to 100 cm depth. Occasional chiseling did not significantly change SOC and total nitrogen stocks to 100 cm depth compared to no-tilled soil (180.4 vs 185.0 Mg C ha−1, and 11.02 vs 11.99 Mg N ha−1; P > 0.10), but this result should not serve as pretext to chiseling, a practice to be cautiously used only when and where needed. Across tillage systems, normal fertilization promoted SOC accumulation compared to reduced fertilization at rates of 0.04–0.25 Mg C ha−1 year−1 in the 0–100 cm, rates that were lower compared to those obtained with no-tillage relative to conventional. Overall, no-tillage system was efficient to accumulate SOC and total nitrogen, and therefore should continue to be encouraged, as well as the application of fertilizer; while occasional chiseling seemed not to change those stocks relative to no-tillage in this Ferralsol. • C and N measured to 1 m depth in a Ferralsol under tillage and fertilization systems. • Over 23 years, no-tillage sequestered 0.93 Mg C ha−1 and 0.07 Mg N ha−1 annually. • Occasional chiseling did not significantly change C and N stocks compared to no-till • Fertilization sequestered 0.04–0.25 Mg C ha−1 year−1 compared to reduced fertilization. • It might be useful to assess C and N to 100 cm depth, not only to 30 cm. [ABSTRACT FROM AUTHOR]