5. Conclusions
The impacts of conservation tillage on crop yield and SOC concentration
are affected by site environmental characteristics. In the cold area
(MAT 0 - 3°C) of NEC, crop yield decreased under NT compared with CT,
and in these environments, RT may be the better tillage practice.
However, as temperature increases, crop yield increases compared to CT
when using NT practices. ST was also observed to have a positive impact
on yield when rotated with other conservation tillage measures, thus
confirming that this practice can be safely implemented if it is
necessary to loosen compacted layers. Conservation tillage measures had
a significant impact on SOC sequestration rate and thus contributed to
greater SOC concentrations, especially in a continuous cropping pattern
under NT. Additionally, SOC effect under NT was significantly correlated
with TN, C/N, and soil bulk density. Below a SOC concentration of 20 g
kg-1, maize yield was found to increase linearly as
SOC increased under NT, and magnitude of the yield increases under ST
tended to be larger the longer ST had been in operation.
Overall, our data suggest that the appropriate use of different
conservation tillage measures in different area in NEC could result in
the win-win situation of crop yield increase and carbon sequestration,
and will help protect soils from degradation and stabilize crop yield in
NEC.