DESIGN, CONSTRUCTION AND TESTING OF A NON- WEIGHING DRAINAGE LYSIMETER

DESIGN, CONSTRUCTION, AND TESTING OF A NON-WEIGHING DRAINAGE LYSIMETER

ABSTRACT: A drainage lysimeter was designed, constructed and tested. The lysimeter will be tested, by using it to estimate crop evapotranspiration of a vegetable crop in Agricultural and Bio-resources engineering farm in Nnamdi Azikiwe University Awka. The vegetable crop to be planted will use water from rain (Precipitation) and the lysi1meter will be used to monitor rainfall, drainage and soil moisture. The daily data that will be generated will be used to calculate crop evapotranspiration from the water balance equation. The generated result from the drainage lysimeter will be compared with the empirical methods.

CHAPTER ONE

1.1 BACKGROUND OF THE STUDY

The non-weighing lysimeters (reconstructed or repacked) are tanks filled with soil in which crops are grown under-examined conditions to measure the amount of water by “evaporation and transpiration” (Jensen et at., 1990). Accurate crop evapotranspiration (ET) data from a lysimeter are required to improve agricultural water resources management (Payero et al., 2003; Todd et al., 2000). However, Lysimeters are considered as the standard method to directly measure evapotranspiration. Lysimeters have a long history of development as such different designs have been developed and used (Howel et al., 1998). The shapes include square (Schneider et al., 1998), circular (Maeshkat et al., 1991) and rectangular (Schneider et al., 1998). The size of the lysimeter is a function of the intended use and the desired result. In monolithic lysimeter, the soil inside the lysimeter is intact (undisturbed or undefiled) soil. (soyfried et al., 2001). In reconstructed or repacked lysimeter, the soil inside the lysimeter is disturbed (excavated) soil, I.e repacking the soil in the lysimeter again to try and mimic the characteristic of the intact soil (Yang et al., 2003).

Lysimeter can be weighing and non-weighing. The non-weighing types are used to determine ET as a residual by measuring all other components of the soil water balance, including water input (rain and Irrigation), output (drainage and runoff), and change in soil water storage (Garcia et al., 2004). Non-weighing lysimeters are also called percolation or drainage lysimeters, are used in percolation and solute transport (Klocke et al.,1993). The knowledge of lysimeter is greatly important for accurate ET measurement. Schneider and Howell (1998) indicated that lysimeter accuracy was directly proportional to the surface area and the data collected.

In drainage or non-weighing lysimeter, changes in water balance are measured volumetrically daily or weekly. No accurate daily estimate can be obtained. Pebbles are placed at the bottom of the lysimeter to aid in easy drainage. Excess water is collected with the aid of a container below a suitable distance. A number of crops can be grown in a concentric pattern around a central drainage chamber. A tube with a small diameter is placed through the soil to the layer of the pebbles to collect excess water at frequent intervals (Okechukwu and Mbajiorgu, 2008).

Evapotranspiration and crop water requirement was a major factor limiting the growth of agricultural practice. The crops are grown either waterlogged to the root zone or the groundwater recharge became depleted thereby leading to the death of crops (Migliaccio et al., 2006). Hylckama (1980) reported that John Dalton in 1796 was the first to construct lysimeter for evapotranspiration studies by figuring the difference between water input and output; while (Kohnke et al., 1940) reported that the first lysimeter study for water use was by Dela Hire of France in the late 17^th  century. Today, lysimeter design has been duplicated for various research interest and no one construction is regarded as standard. The proper design can be made only by having an accurate knowledge of both the purpose of the experiment including geologic and climatic conditions (Okechukwu et al., 2008). The cost of constructing and installing a lysimeter vary considerably and mainly affected by its size and type of material used and the management of limited water resources is a sure way to proffer solutions to water wastage, food shortage, and poor crop yield. Lysimeters are the most reliable research tool for direct evaluation of evapotranspiration (Burman and Pochop, 1994).

1.2   Justification of the Study

In agricultural land, there is continuous effort to upgrade and improve on overall efficiency of crop. The practical importance of the study can be deduced from the positive effect it will have on farmers since it will enlighten them on evapotranspiration and crop water requirement and will increase the efficiency of the crop grown.

The lysimeter fabricated will accurately assess the crop water requirement of vegetables as well as other field crops.

1.3   Objective of the Study  

The objectives of this study are:

1. To design and construct a non-weighing lysimeter for ET studies.
2. Installation and testing of a drainage non-weighing lysimeter.

1.4 Scope of this Project

This study is limited to the design, construction, and testing of a drainage lysimeter.

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TABLE OF CONTENTS

CHAPTER ONE: INTRODUCTION

• Background of Study 1
• Justification of Study 3
• Objective of Study 3
• Scope of Study 4

CHAPTER TWO: LITERATURE REVIEW

2.1   Hydrologic Cycle                                                      5

2.2   Empirical Method of Predicting Evapotranspiration 6

2.2.1        Temperature Method                                               8

2.2.2        Radiation Method                                                    9

2.2. 3 Penman combination formula                                       12

2.2.4        Blaney Criddle method                                             15

2.3   Field Method of Lysimeter                                        16

2.3.1        Non-Weighting Method                                            18

CHAPTER THREE:

MATERIALS AND METHODS                

3.1   Study Area                                                                       20

3.2   Design of the Lysimeter                                                    21

3.3   Construction of the Lysimeter                                          26

3.4   Installation of the Lysimeter                                            27

3.5   Testing of the Lysimeter                                                   30

Chapter four:

 Results and Discussion

4.1   Data Presentation and Analysis                                               32 Chapter Five:

 Conclusion and Recommendation

5.0   Conclusion                                                                      38

5.2   Recommendation                                                             39

Reference                                                                                 41

Appendix                                                                         44

LIST OF TABLE

Table 4.1 Crop Evapotranspiration data                                  32

Table 4.2 Data from crop wat model                                                34

Table 4.3 Comparison of ET_C Lysimeter AND ET_C Penmann    35

LIST OF FIGURES

FIG 2.1 Hydrologic Cycle                                                          6

Fig 3.1Front View                                                                     22

Fig 3.2   Side View                                                                   23

Fig 3.3 Plan view                                                                      24

Fig 3.4 Isometric Lysimeter                                                      26

Fig 4.1 Graph of ET_C Lysimeter against ET_C Penmann             36

NOMENCLATURE

Et = Evapotranspiration

ET_o = Reference Evapotranspiration

ET_c = Crop Evapotranspiration