Clipping of Bidens pilosa L. var. radiata Sch. Bip. Effect on Compensatory Growth for Soil Management

Bidens pilosa L. var. radiata Sch. Bip. is a common weed in the low altitude area in Taiwan. Its advantages on perennial life cycle, flowering in all seasons and vegetative reproductivity make it is listed as one of the most twenty noxious invasive plants in Taiwan. This study works on the influence of clipping on its growth of vegetative organs to consider the the contribution to soil fertility of by the return of clipped shoot to the soil. We study on the influence of clipping on the root growth and death in different depth to consider the possibility of providing soil organic matters through the management of clipping B. pilosa var. radiata. And we also study on the relationship between wild B. pilosa var. radiata growth and the soil organic matters to estimate its contribution to soil organic matters. There are three experiments. The first experiment is a pot-culture experiment. To analyze the influence to B. pilosa var. radiata, we compare the biomass in leaves, roots and stems and the difference in organic matters, leaf area and Nitrogen, Phosphates, Potassium concentrations between the control and the clipping treatment with unpaired t-test. In the second experiment, we plant the B. pilosa var. radiata in the rhizotrons and observe the root length. We recorded the full root length, dead and alive separately, in the depth of 0-30 cm, 30-60 cm and 60-90 cm, and compare the difference between the lengths before and after clipping with Duncan’s test. The third experiment, through the field research, compares the soil quality, organic matters, pH value, conductivity, on-site volune wetness and bulk density, of living regions between the B. pilosa var. radiata and Ipomoea pes-caprae. The multiple regression analysis of the numbers of B. pilosa var. radiata and the soil parameters were also done to study on the relationship between soil parameters and B. pilosa var. radiata. The results show that, compared to control, the cliping treated plants have a very significant decrease in the porpotion of stem and a significantly higher leaf porpotion but having no differences in leaf area. This may resulted from its tendency to increasing leaf area by leaf growth in order to harvest more light energy. The clipped stem and leaf of B.pilosa var. radita have a higher Nitrogen , Phosphate and Potassium concentration, indicates that the clipped B. pilosa var. radiata has a higher shoot nutrient. From observing the rhizotron we noticed that, in the 14 days after clipping, the root systems in three depths remained growing, it means that it can continues to provide organic matters in the three soil depth. The dead root length in 0-30 cm and 30-60 cm increased significantly, it means that the dead root systems can be the source of the soil depth, increasing its soil organic matters. In both before and after clipping, B. pilosa var. radiata have most of the root length in 0-30 cm. Through the field research, compared to the living region of Ipomoea pes-caprae, the living region of the B. pilosa var. radiata has a very significantly higher soil organic matters. We can conclude that B. pilosa var. radiata has a better performance on increasing soil organic matters than Ipomoea pes-caprae. The multiple regression analysis shows a significant positive correlation between the number of B. pilosa var. radiata and the soil organic matters. It can be concluded that the more B. pilosa var. radiata plants growing has a significant correlation with higher increase of soil organic matters.