| Summary: | 博士 === 國立臺灣大學 === 農業化學研究所 === 83 === The C/N of P. lapathifolium was 29. Plant residue equivalant to 2% of soil was added to soil and incubated for 21 weeks. The results showed that the mineralization rate of P. lapathifolium in the soil is slow.
The pot experiment showed that P. lapathifolium had lower ability of suppling plant nutrients than the traditional green manures. However, the effect of P. lapathifolium on rice grain yield and N, P, K content in plant were similar to that of trad-itional green manures. In the field experiment,the effect of green manures on rice grain yield were in the order of B.napus >P.lapa-thifolium > T. alexandarium > no green manure.
Fresh P. lapathifolium seeds were buried in the spring of 1994.
They were in a state of conditionally dormant. More than 96% of buried seeds remained in a state of enforced dormancy in a water logged condition and survived. But they loss their viability during 1 year in upland soil. The seeds buried in wet land break the dormancy in autumn asthe soilis plowed and drained.
The field was treated by land-plowing, crop residue burning and land-mulching. Two months after the treatments,land-plowing had the highest number of plant per unit area. Land-burning got the biomass yield of 15 tons/ha. Land-mulching had the lowest plant number and the lowest biomass.The amount of nutrients absorbed by P. lapathifolium during growth period were 40 Kg/ha nitrogen, 10 Kg/ha phosporous and 80Kg/ha potassium.
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