Cropping Systems: Applications, Management and Impact

Increased Soil Fertility ... 111

The soil sampling depth is shallower in the present sudy (20 cm) than in
the previous study (100 cm), which to some extent results in the relatively
lower fertilizer-N retention but higher fertilizer-N loss (minusing fertilizer-N
retention in soil and fertilizer-N uptake by aboveground plant parts from N
application rate) in this study. In addition, we speculate that N loss
characteristics in rice production may vary with different rice-based cropping
systems, because the magnitudes of differences in fertilizer-N retention and
loss rates between the two studies are smaller under the N rates of 120 and 90
kg ha–^1 than under the N rate of 150 kg ha–^1. This might also be a reason for
the large difference in fertilizer-N loss rate under the N rate of 150 kg ha–^1
between our study and the previous study. It is highlighted the need for greater
fundamental understanding of the effects of long-term rice-oilseed rape
rotation on N loss pathways in rice production.

CONCLUSION

Our study suggests that long-term rice-oilseed rape rotation can increase
soil fertility and consequently reduce the dependence on external N inputs and
the impact on environments in rice production.

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