To reveal the reason of rice yield promotion by rapeseed straw under multi-crop planting systems,
rapeseed-rice and wheat-rice rotation systems were investigated by simulative straw residue leachates effect on rice
growth. The leachates from straw in soil were used as materials under a randomized block design with 3 factors,
which included straw types, additive liquid types and leachate concentration. Straw type contains rapeseed and
wheat. Additive liquid types are distilled water and nutrient solution. Straw concentration includes control(0 g/L),
low(1 g/L), medium(5 g/L)and high(20 g/L), corresponding to the amount of straw incorporation of 0 kg/hm2, 1500
kg/hm2, 7500 kg/hm2 and 30 000 kg/hm2. Results showed that straw type, additive liquid type and concentration had
no significant impact on seed germination, but had significant influence on growth of rice seedlings. Dry weight of
rice seedlings for rapeseed straw residue leachate was significantly 10.7-44.4% higher than that of wheat straw in
distilled water. Dry weight of rice seedlings with rapeseed straw residue leachate was 2.2-12.1% higher than that of
wheat straw in nutrient solution at 1 and 5 g/L straw. Compared with distilled water, dry weight of rice seedlings in⁃
creased by 53.7-130.0% treated by nutrient solution. The dry weight and plant height of rice seedlings reached the
maximum at 5 g/L among different straw concentrations. Nutrient accumulation of rice seedlings showed a similar
trend with dry weight. The difference between nitrogen accumulation was the most significant with distilled water as
additive liquid. Only on the 12th day after sowing, the nitrogen and potassium accumulation of rice seedlings at 5 g/
L straw concentration showed significant differences in nutrient solution. Compared with distilled water, N, P, K ac⁃
cumulation of rice seedlings treated with nutrient solution increased by 2.0-3.0 times, 1.0-2.0 times and 1.4-1.7
times. The accumulation of nitrogen and potassium in rice seedlings was the highest at 5 g/L straw concentration,
with no difference in phosphorus. Compared with nutrient solution, the difference in sensitivity index between rape⁃
seed and wheat straw residue leachate was greater than those with distilled water as additive liquid. In conclusion,
both rapeseed and wheat straw residue leachates could promote rice growth. Comparing with wheat straw, rapeseed
straw residue leachate promoted rice growth better.