INTRODUCTION
Green manure is a traditional organic manure in China
and has been used since ancient times. The planting area
using green manures in China is the largest in the world.
Production and application of green manure have played
an important role in food production and improving soil
fertility. Despite the long history of green manure in
China, farmers have had little enthusiasm to improve
soil fertility since the 1980s. This has been mainly due
to the low economic benefit of green manure in rice
production and the large labor force required for winter
planting of green manure. Meanwhile, the obvious benefits
of artificial fertilizers have been greatly promoted.
The yield increase from incorporating green manure in
the year of application is not as obvious with the same
investment in artificial fertilizer. Since the mid-twentieth
century, the area devoted to producing green manure has
lands in China and research on this soil has been long
considered of great importance. Reddish paddy soil at the
Key Field Monitoring Experimental Station for Red Soil
Eco-Environment of the Ministry of Agriculture, Qiyang
County, Hunan, China, was used in the present study.
In recent years, researchers have studied the effects of
winter planting of green manure on rice yield (Gao et al.
2013), weed species diversity (Xie et al. 2011), microbial
properties, enzyme activities (Yang et al. 2011a), quality
(Yang et al. 2011b) and physical properties (Yang et al.
2012) of reddish paddy soil. However, there have been
few studies of the distribution and storage of organic
C and N in water-stable aggregates in reddish paddy
soil with long-term winter planted green manure under
double-rice cropping system in the Yangtze River. This
study will provide a better understanding of how longterm
(28 yr) winter planting of rape (Brassica napus L.),
Chinese milk vetch and ryegrass (Lolium perenne L.)
affect the content, distribution and storage of organic C
and N in water-stable aggregates in the plowed layer of a
reddish paddy soil under a double-rice cropping system.