96
7 Effects of Conservation Practices …
(Meng et al. 2001), and dense plant cover, good soil structure, high soil organic material (SOM) and biological activity were assumed to be the probable causes (Maass
et al. 1988). While on the steep hillside farm, the bench terrace was revealed to play
a more significant role in reducing soil and water loss compared to conventional
cultivation methods (Mills et al. 1992). In the Hekou-Longmen Region of the Loess
Plateau, check dam was of vital importance in retaining soil in all of the conservation
measures (Ran et al. 2002, 2004).
Erosion studies carried out at the catchment scale are more representative of the
natural processes than those at the plot scale. However, they are more difficult to
execute, due to the spatial-temporal variation of the sediment sources, as well as the
complex interaction between sediment sources, temporary and longer-term sediment
sinks and alluvial channels (García-Ruiz 2010; Owens 2005). Scaling effects existed
when data of the plot scale were extended to the catchment scale (Fang et al. 2008).
Up to the present, few retrospective assessments have been made to measure the
amount of the retained runoff and soil by the conservation practices for decades
at the catchment scale, especially the soil nutrients. Meanwhile, the data collected
from the field were only for short-term monitoring within several years (Minella
et al. 2009).
A tremendous difficulty in quantitatively calculating the effects of soil nutrients
lies in the fact that little information relates to soil nutrient budgets with altered
land-use and climate change settings. Other than soil nutrients, sediment yield was
monitored in most of the existing studies, as a parameter of assessing changes in
erosion and sediment mobilization resulted from the implementation of soil conservation practices (e.g., Li et al. 2010; Mohammad and Adam 2010; Shen et al. 2010;
Minella et al. 2009; Tian et al. 2008; Ran et al. 2004, 2002). Generally, the mean
annual soil nutrients retained on various lands were detected to evaluate the effects
of alternate land uses (e.g., Jiao et al. 2010; Tripathi and Singh 2009). Quite consistent information had been obtained on the effect of tillage practice and crop choice
with the plot studies, whereas that on the route of sediment transport and amount
of sediment and nutrients was still scarce, especially that could reach a watercourse
from the adjacent slopes (Veihe et al. 2003). Among all the researches, the quality
of groundwater in the catchment may be the most direct and convictive parameter.
Unfortunately, few results were obtained in the absence of field observation data of
nutrients in the groundwater regarding the frequency of occurrence of different erosion processes. Multiplying the rate of nutrient loss by the area of soil conservation
practice is another effective way to evaluate the amount of retained soil nutrient (Pan
et al. 2006). Nevertheless, only the observation data of soil nutrient loss from the
forestland, grassland, slope farmland and some other lands were currently recorded
(Zhao et al. 2006), while those from the terrace farmland and dam farmland under
different rainfall events were not collected.
Herein we perform a series of calculation on hydro-sediment and nutrient for a
period of 50 years undertaken in a representative catchment in the Loess Mesa Ravine
Region of the Loess Plateau. The objectives of this study are to (1) quantify the
effects of conservation management in terms of retaining soil, water, and especially
nutrients, and (2) recommend a preferred conservation practice on the Loess Plateau.
7 Effects of Conservation Practices …
(Meng et al. 2001), and dense plant cover, good soil structure, high soil organic material (SOM) and biological activity were assumed to be the probable causes (Maass
et al. 1988). While on the steep hillside farm, the bench terrace was revealed to play
a more significant role in reducing soil and water loss compared to conventional
cultivation methods (Mills et al. 1992). In the Hekou-Longmen Region of the Loess
Plateau, check dam was of vital importance in retaining soil in all of the conservation
measures (Ran et al. 2002, 2004).
Erosion studies carried out at the catchment scale are more representative of the
natural processes than those at the plot scale. However, they are more difficult to
execute, due to the spatial-temporal variation of the sediment sources, as well as the
complex interaction between sediment sources, temporary and longer-term sediment
sinks and alluvial channels (García-Ruiz 2010; Owens 2005). Scaling effects existed
when data of the plot scale were extended to the catchment scale (Fang et al. 2008).
Up to the present, few retrospective assessments have been made to measure the
amount of the retained runoff and soil by the conservation practices for decades
at the catchment scale, especially the soil nutrients. Meanwhile, the data collected
from the field were only for short-term monitoring within several years (Minella
et al. 2009).
A tremendous difficulty in quantitatively calculating the effects of soil nutrients
lies in the fact that little information relates to soil nutrient budgets with altered
land-use and climate change settings. Other than soil nutrients, sediment yield was
monitored in most of the existing studies, as a parameter of assessing changes in
erosion and sediment mobilization resulted from the implementation of soil conservation practices (e.g., Li et al. 2010; Mohammad and Adam 2010; Shen et al. 2010;
Minella et al. 2009; Tian et al. 2008; Ran et al. 2004, 2002). Generally, the mean
annual soil nutrients retained on various lands were detected to evaluate the effects
of alternate land uses (e.g., Jiao et al. 2010; Tripathi and Singh 2009). Quite consistent information had been obtained on the effect of tillage practice and crop choice
with the plot studies, whereas that on the route of sediment transport and amount
of sediment and nutrients was still scarce, especially that could reach a watercourse
from the adjacent slopes (Veihe et al. 2003). Among all the researches, the quality
of groundwater in the catchment may be the most direct and convictive parameter.
Unfortunately, few results were obtained in the absence of field observation data of
nutrients in the groundwater regarding the frequency of occurrence of different erosion processes. Multiplying the rate of nutrient loss by the area of soil conservation
practice is another effective way to evaluate the amount of retained soil nutrient (Pan
et al. 2006). Nevertheless, only the observation data of soil nutrient loss from the
forestland, grassland, slope farmland and some other lands were currently recorded
(Zhao et al. 2006), while those from the terrace farmland and dam farmland under
different rainfall events were not collected.
Herein we perform a series of calculation on hydro-sediment and nutrient for a
period of 50 years undertaken in a representative catchment in the Loess Mesa Ravine
Region of the Loess Plateau. The objectives of this study are to (1) quantify the
effects of conservation management in terms of retaining soil, water, and especially
nutrients, and (2) recommend a preferred conservation practice on the Loess Plateau.