The semi-arid areas of China are mainly characterized by a hilly landscape, and its agricultural development level is relatively low. Although terrace farming is rapidly expanding, there is limited information regarding how to quickly improve soil organic carbon (SOC) and soil fertility in newly-built terraces under fertilizer management.
Researchers from Xishuangbanna Tropical Botanical Garden (XTBG) and Lanzhou University conducted a study to evaluate the effects of adding manure on SOC sequestration, soil aggregate distribution, C/N ratio of enzyme in newly-built terraces. The study was carried out over 7 growing seasons from 2004 to 2010 on the semi-arid Loess Plateau of China.
Experimental treatments including CK (control treatment with no fertilizer), NP (nitrogen and phosphorus), M (manure) and MNP (manure, nitrogen and phosphorus) were employed with a field pea–spring wheat–potato cropping system.
The researchers found that SOC and total nitrogen built up faster in the manure treatments than without manure. The largest size aggregates (>2 mm) have important implications for C sequestration. Application of fertilizer alone could not form the largest aggregates (>2 mm). Manure application significantly increased SOC content in all soil aggregate size classes compared to no manure treatments.
Manure treatments improved soil C/N ratio, while fertilizer treatment (NP) decreased soil C/N ratio. Manure treatments significantly increased activities of alkaline phosphatase and β-glucosidase compared with no manure treatments.
Significant positive correlations were observed between all tested enzyme activities and SOC, total nitrogen, total phosphorus, available phosphorus, microbial biomass C, and mineral N.
The results showed that adding manure is essential in improving soil fertility and accelerating the build-up of fertility in newly-built terraces in a semi-arid environment. The soil available phosphorus is very deficient in newly-built terraces, and it is necessary to apply more P fertilizer to them.