Two experiments in newly-culltivated slope land and upland with three treatments

Nil(CK)

NPK(NPK)

Straw NP(SNP)

were selected to analyze the effects of ex situ rice straw incorporation on the distribution of organic carbon and nitrogen in water-stable macro-aggregates of hilly red soils.Results showed that

ex situ incorporation of straw increased water-stable macro-aggregates and the concentrations of organic carbon and nitrogen increased with increase of water-stable aggregate-size;ex situ incorporation of straw significantly increased the concentrations of organic carbon and nitrogen in water-stable macro-aggregates by 10.1%~78.5% and 9.4%~63.6%(p<0.05)

and also increased the ratios of organic carbon and nitrogen in water-stable macro-aggregates(2~5 mm or 1~2 mm) to soil;Compared to inorganic fertilizer

ex situ incorporation of straw significantly increased the concentrations of organic carbon by 6.5%~46.1% in 0.5~1 mm

1~2 mm

2~5 mm

>5 mm water-stable aggregates and nitrogen by 8.7%~16.1% in 0.5~1 mm

1~2 mm

2~5 mm water-stable aggregates.Water-stable macro-aggregates have high potential to accumulate organic C and N

and ex situ incorporation of straw increased the concentrations and distributions of organic C and total N in water-stable macro-aggregates

which increased the ability of regulating soil fertility.Therefore

ex situ incorporation of straw was effective measure to improve soil structure

enhance and regulate soil fertility in hilly red soils.