Amounts of stubbles left in paddy fields : evaluation from the viewpoints of C sequestration and soil fertility
2017
Jun-Jie, Lu | Ping Zou | Guang-hua Wang | Jian-rong Fu | Ho Ando | Makoto Kimura
Plant residues are the main source of organic materials maintaining soil fertility in paddy fields, among which rice stubble has been disregarded of its importance so far. This study highlighted the great amount of rice stubbles retained in paddy fields in comparison with that of corn stubbles. Height of rice stubbles was measured in paddy fields under harvesting methods by hand and harvested around Harbin and Shoxing City, China. The height of stubbles above the ground was 5.0 +-1.7 cm, 10.1 +- 2.3 cm and 28.7 +- 8.4 cm for rice fields harvested by hand and harvesters that left rice straw in the fields without and with cutting it into segments, corresponding to 18 � 25%, 25 � 32% and 47-60% of total top-part biomass (excluding ears), respectively. These results suggested that the biomass of stubbles left in paddy fields by the second-type harvesters was larger than that of rice straw. Mechanization in harvesting rice plants was 73% in 2014, and the estimated amount of stubbles left in paddy fields was at least 1514 to 1973 kg/ha. Comparable measurements of corn plants and stubbles in corn fields showed that the average height of corn stubbles harvested by hang was 9.1 +- 2.5 cm and the corresponding stubble biomass was only about 7-9% of the total top-part biomass (excluding ears) amounting the 413-639 kg/ha. This was the first study that quantitatively elucidated the importance of rice stubbles in C sequestration and soil fertility in paddy fields in recent China.
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