Studies on Potential Supply of Soil Organic Matter Using Phragmites australis in Reclaimed Land

This research was conducted to investigate the possibility of reeds (Phragmites australis) application to increase the low organic matter content in the reclaimed soil. Reed is not only a perennial vegetation native growing in the reclaimed land and a plant promising for soil organic resources as it is regenerated every year and also has a lot of biomass. In order to establish the system to increase the soil organic matter content, the reed residue was put into the soil using a tractor in different periods. After the growth, the reed straw was put into the soil at mid-September, mid-November and mid-February of the following year during 1st, 2nd and 3rd year. Soil chemistry showed no difference in pH and EC was slightly higher at constant three years of return plot. Carbon content increased at all treatments with increasing the number of application regardless of the treatment season. The amount of soil organic content increased with increasing the number of application comparing to 4.65 g kg-1 in soil with the preserved reed. This also increased to 8.01 g kg-1, 6.85 g kg-1 and 7.02 g kg-1 when the treatment was continued at mid-September, mid-November and mid-February for three years, respectively. This clearly showed that the application of reed straw to the soil was effective to improve soil fertility. Therefore, in order to increase the organic content of the reclaimed soil, it would be effective that the body part of reed is returned to the soil at mid-September of each year after the growth of reed is completed. Soil chemical properties of top soil after the experiment. Application pH† EC N C Av. P2O5 Exch. cations Ca K Mg Na 1:5 dS m-1 mg kg-1 mg kg-1 mg kg-1 ----- cmol kg-1 ----- No treat. 6.62a 3.6c 0.05c 0.29c 23.50 1.10 0.51 2.54 0.44a Ⅰ‡ 6.17b 3.3c 0.06 0.30c 28.39 1.23 0.51 2.38 0.17b Ⅱ 6.30ab 3.8c 0.06 0.39b 30.24 1.24 0.56 2.33 0.17b Ⅲ 6.16b 4.8a 0.07a 0.46a 40.56 1.29 0.59 2.41 0.18b Ⅳ 6.31ab 3.4c 0.06 0.37b 29.01 1.15 0.51 2.27 0.29ab Ⅴ 6.20b 3.9c 0.06 0.38b 30.32 1.42 0.54 2.36 0.14b Ⅵ 6.13b 4.4ab 0.06 0.40a 37.95 1.28 0.58 2.41 0.14b Ⅶ 6.28ab 3.6c 0.06 0.32c 29.73 1.29 0.55 2.37 0.21b Ⅷ 6.57a 4.2c 0.07a 0.37b 28.39 1.13 0.53 2.50 0.42a Ⅸ 6.26ab 5.6a 0.07a 0.41a 35.42 1.32 0.57 2.52 0.25b ns ns ns ns †Means with same lettered superscripts of column’s are not significantly different at 5% level by Duncan’s multiple range test.‡reed residue soil input time. Ⅰ: Sept(2014), Ⅱ: Sept(2014 and 2015), Ⅲ: Sept((2014 to 2016), Ⅳ: Nov(2014),Ⅴ: Nov(2014 and 2015), Ⅵ: Nov(2014 to 2016), Ⅶ: Feb(2014), Ⅷ: Feb(2014 and 2015), Ⅸ: Feb(2014 to 2016).