Rainfall Simulation Studies to Estimate Soil Erosion as Influenced by Rainfall Intensity and Slope in Four Distinct Soils Conservation of soil and other natural resources is critically important for all stakeholders in today's society. The work of Dumanski (2009) reports that soil conservation importance along with the control and mitigation of land degradation are more highly recognized now than at any time in the past." The significance of this study is first, the additional knowledge that will be applied to the already existing base of knowledge on soil conservation practices. This study specifically examines the estimation of foil erosion rates based on (1) rainfall intensity; and (2) slope in four distinct soils. This study has three primary objectives: (1) The first objective is to conduct a study of soil conservation in the Caribbean through investigating the effect of slope angle and rainfall intensities on soil erosion under controlled conditions using four distinct soil types; (2) The second objective is to compare the data through use a cropped plot; and (3) The third objective is to highlight an approach for estimating erosion risk and nutrient loss for Trinidad and Tobago.

Rainfall Simulation Studies To Estimate Soil Erosion As Influenced By Rainfall Intensity and Slope in Four Distinct Soils

I. Statement of the Problem

Conservation of soil and other natural resources is critically important for all stakeholders in today's society. The work of Dumanski (2009) reports that soil conservation importance along with the control and mitigation of land degradation are more highly recognized now than at any time in the past."

II. Significance of the Study

The significance of this study is first, the additional knowledge that will be applied to the already existing base of knowledge on soil conservation practices. This study specifically examines the estimation of foil erosion rates based on (1) Rainfall intensity; and (2) Slope in four distinct soils.

More specifically the study will take place in the Caribbean locations of Trinidad and Tobago.

Introduction

Agricultural regions throughout the world deal with the issue of soil erosion and how to best mitigate the challenges of soil erosion. One such region of the world is that which are referred to as the Caribbean karsts characterized by such as "…natural vegetation, surface watersheds, caves, and groundwater aquifers…" which is presently threatened environmentally including that of soil erosion which negatively affects all plant life in the region. Day (2010) states of the agricultural region that the Caribbean karst is characterized by "changing environmental conditions…may well be a portent for the overall environmental health of the region, and the karst thus represents a potential barometer of human ability to respond to the very real challenges to environmental sustainability." (Day, 2010)

Research Objectives

This study has three primary objectives.

(1) The first objective is to conduct a study of soil conservation in the Caribbean through investigating the effect of slope angle and rainfall intensities on soil erosion under controlled conditions using four distinct soil types;

(2) The second objective is to compare the data through use a cropped plot; and (3) The third objective is to highlight an approach for estimating erosion risk and nutrient loss for Trinidad and Tobago.

I. The Importance of Soil Conservation

The conservation of soil is important as it is "the most fundamental and basic resource" and while "erroneously dubbed as 'dirt' or perceived as something of insignificant value, humans cannot survive without soil because it is the basis of all terrestrial life." (Blanco and Lal, 2010, p. 1) In addition, soil is a resource of a vital nature as it makes the provision of "food, feed, fuel, and fiber" possible and as well soil "underpins food security and environmental quality…" (Blanco and Lal, 2010, p. 1) Soil is a resource that is non-renewable over the scale of human time and as well, soil is reported to be "dynamic and prone to rapid degradation with land misuse." (Blanco and Lal, 2010, p. 1)

The two primary agents of soil degradation are those of wind and water with water erosion affecting approximately 1,100 million hectares (Mhs) worldwide, stated to represent approximately 56% of the total degraded land while wind erosion affects about 28% of the total degraded land area." (Blanco and Lal, 2010) In addition, it is reported that soil participles are washed away from sloping and bare lands by runoff and loose and detached soil particles are blown by wind loosening these particles from lands that are flat or unprotected. Soil is also redistributed by erosion from plowing the solid as the soil is moved gradually downslope adversely affecting crop...

(Blanco and Lal, 2010) Two types of soil erosion are stated to be those of: (1) geologic; and (2) accelerated erosion. Geological erosion is reported as a normal process of weathering that takes place at low rates in all soils as part of the natural soil-forming processes." (Blanco and Lal, 2010) Geologic erosion occurs over a long geologic time frame and is not affected by the activity of humans. Geologic erosion is characterized by slow but continuous geologic erosion, which are critical to soil formation. Accelerated erosion is reported to be "triggered by anthropogenic causes such as deforestation, slash-and-burn agriculture; intensive plowing, intensive and uncontrolled grazing, and biomass burning." (Blanco and Lal, 2010)
II. Soil Conservation Strategies

Day (2010) writes that the karst land of the Caribbean, a sloped agricultural region must address the potential "severity of both climatic and other anthropogenic impacts within the karst…" and how it is that these can most successfully be reduced through "appropriate land management and sustainable land use planning, including the expansion and maintenance of protected areas. All elements of natural and human-modified ecosystems within the karst need to be taken into account." (Day, 2010) Karst landscapes in the Caribbean comprise approximately 130,000 km, which is more than fifty percent of the total land area of the region. The karst landscapes of the Caribbean include "cockpits, towers, dry valleys, do lines, blue holes and caves." (Day, 2010) The Caribbean karst lands are challenges to habitation of humans since they are characterized by a wide range of natural hazards that include "drought and flooding…risk of degradation and vulnerable to environmental change." (Day, 2010) The impact of humans to Caribbean karst lands has been of a significant nature. Land-use sustainability planning is required in appropriately managing the land and in planning for land use toward the goal of long-term sustainability. (Day, 2010) According to Day (2010) Karst soils are "extremely variable. Steep slopes may be bare, while thicker soils in depressions and valley bases are often associated with bauxitic infills. Vegetation varies from xerophytic scrub to wet tropical deciduous and coniferous forest, with many endemic species. Most of the original forest has been cleared, with only fragments remaining in remote karst areas." (Day, 2010) Additionally Day (2010) reports that drought and water supply are the primary sustainability issues in the Caribbean karsts and that the forest having been cleared aggressively has affected the karst profoundly. Agriculture is the primary land-use initiative in the Caribbean karst. Due to the clearing of forests in addition to agriculture the effects on the Caribbean sustainability requirements is harsh. Agriculture is on a steady increase and must address long-term and rigorous soil erosion, water-use and contamination and maintenance of protected areas. The Caribbean karst is best suited to small-scale farming although there are reported to be existing operations on a larger-scale where "feasible if tied to stringent conservation measures." (Day, 2010) The work of Ustun (2008) reports that soil loss determination method is comprised by two different "base phases": (1) the water phase; and (2) the sedimentation phase. Ustun states that at the water phase "kinetic energy of rainfall, overland flow and annual precipitation values and at the sedimentation phase rates of soil detachment by raindrop impact and transport capacity of overland flow values are calculated every pixel by generating maps for each input data" referred to as the 'Morgan model'. (Ustun, 2008) The input parameters and operating functions of this model are listed in 'Appendix A' of this study.

The work of Zheng, et al. (2004) reports that soil degradation caused by deforestation is one of the primary environmental problems globally. Zheng (2004) reports a study that examined the loss of nutrient as related to soil erosion in newly deforested lands in the Ziwuling region on the Locess Plateau of China. Reported is as follows:

"Eight field runoff plots, with various sizes to enable documentation different combinations of dominant erosion processes, were established on a hillslope. Results showed that the nutrient loss was dramatically affected by erosion patterns and erosion intensity." (Zheng, et al., 2004)

It is reported in the work of Wang, et al. (2005) that comprehension of the impacts of land use on soil and water loss is critically important and reports a study in which two catchments with land use differentiation were chosen to measure the moisture, runoff and nutrient loss in soul and the land use patterns…