3. Results
3.1. Growth of grass hedges and crops
During the experiments the density of grass hedges and crop coverage was monitored and results are listed in Table 2. For both grasses, it is shown that the grass density reached about 1000 plants m−2 in the second year after transplanting in 2005 and remained stable in the next three years. This shows that the growth of Pennisetum and Arundinella grass is very quick. For other grass species, e.g., vetiver grass, it seems that dense grass hedges may be formed after 2 or 3 years (Duchemin and Hogue, 2009 and World Bank, 1993). From Table 2, we can find that the density of Pennisetum hedges is slightly higher than Arundinella hedges. Some small gaps in Pennisetum hedges were found, due to plant discontinuity; but that was not found in Arundinella hedges. However no concentrated overland flow path (rills or small gullies) was found through the hedges during the experiment. Pennisetum hedges were denser than Arundinella, but they grow in clusters while Arundinella hedges are much more even.
Almost all the experiments were conducted when the crops thoroughly covered the soil. Table 2 shows that the coverage of crops during the rain simulation in all cases exceeded 70%; this implies that the influence of crops cover extent on runoff and soil loss may be ignored
3. Results
3.1. Growth of grass hedges and crops
During the experiments the density of grass hedges and crop coverage was monitored and results are listed in Table 2. For both grasses, it is shown that the grass density reached about 1000 plants m−2 in the second year after transplanting in 2005 and remained stable in the next three years. This shows that the growth of Pennisetum and Arundinella grass is very quick. For other grass species, e.g., vetiver grass, it seems that dense grass hedges may be formed after 2 or 3 years (Duchemin and Hogue, 2009 and World Bank, 1993). From Table 2, we can find that the density of Pennisetum hedges is slightly higher than Arundinella hedges. Some small gaps in Pennisetum hedges were found, due to plant discontinuity; but that was not found in Arundinella hedges. However no concentrated overland flow path (rills or small gullies) was found through the hedges during the experiment. Pennisetum hedges were denser than Arundinella, but they grow in clusters while Arundinella hedges are much more even.
Almost all the experiments were conducted when the crops thoroughly covered the soil. Table 2 shows that the coverage of crops during the rain simulation in all cases exceeded 70%; this implies that the influence of crops cover extent on runoff and soil loss may be ignored
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