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EFFECTIVENESS OF PITCHER FERTIGATION ON BUSH PEPPER PLANTS
Abstract and Figures
Pitcher is a bottlelike emitter made of porous baked-clay that is designed to be able to release water through its wall into the surrounding soil. In irrigation practice water level inside the pitcher is maintained by means of a constant water level supplier, or mariotte tube. This research looks at how the pitcher can also release nutrients when filled with dissolved fertilizers. For this purpose, we measured hydraulic and hydro-dynamic properties of the pitcher, and simulated solute transport using the convective-dispersive equation, and observed the effectiveness of fertigation in which NPK fertilizers were used on bush pepper plants. The results showed the pitcher was capable to release dissolved solution. Soil water content played significant roles in distributing the dissolved solution. These three nutrients have different distribution patterns. Nitrogen was well distributed, Phosphor was accumulated close to the pitcher's wall, and Potassium increased gradually with distance. These difference patterns were caused by the difference of hydrodynamic coefficients in which Nitrogen was the largest value among the others. The diffusion coefficient ranged at 1.01x10 -7 – 4.1x10 -3 cm 2 /day for NaCl, and 6.7x10 -6 -3.5x10 -3 cm 2 /day for NPK fertilizers. Bush papers planted surrounding a pitcher enabled to extract the nutrients as shown by the progressive growth of the crops: height, branches, leaves and flowers, which were monitored daily. After unearthed, roots of the bush pepper developed only in the wetter soils. This showed the water as well as the dissolved solution were resided concentrically around the pitcher's wall, and were all available to use by the plants effectively.
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In the previous chapters, the phenomena of transport in porous media have been described by mathematical models. The complete description was made up of a partial differential equation, or a system of several partial differential equations, together with initial conditions and boundary conditions. In order to solve a given groundwater problem, this system of equations must be solved, for the specific data of that problem. This can be done by using analytical methods, or numerical techniques. For most problems of practical interest, because of the irregular shape of the boundaries, the spatial variability of the coefficients appearing in the equations and in the boundary conditions, the nonuniformity of the initial conditions, and the nonanalytic form of the various source and sink terms, analytical solutions are virtually impossible, except for relatively simple problems. Solutions of most problems can be obtained only by numerical methods. Hence, in this book numerical methods of solution are used almost exclusively. They provide a most powerful and general tool for solving problems encountered in practice. In this chapter, some general aspects will be discussed. In Chapters 9–13 specific problems will be solved, and actual numerical models will be presented.
The molecular diffusion coefficients of salt were measured in Shonai sand dune sand and Kanto loam soils over a wide range of water contents using a transient state method. The measured relative diffusion coefficient, D-r, the ratio of diffusivity of salt in soil to the diffusivity in bulk water, varies from 0.31 to 2.98 x 10(-3) for Shonai dune sand as volumetric water content decreases from 31.74% (0.00215 MPa) to 2.13% (5 MPa). For Kanto loam soil it varies from 0.17 to 6.25 x 10(-3) as water content decreases from 60.89% (0.0021 MPa) to 20.22% (3.11 MPa suction). The relationship of D-r with water content in soil shows a linear relationship on log-log scale at higher water contents for both soils. However, it shows a break point at the water content that corresponds to a matric suction of about 0.09 MPa for both soils. The respective slopes of D-r(theta) for Shonai dune sand and Kanto loam are 0.75 and 1.25 at higher water contents (> break point) and 3.99 and 4.1 at lower water contents. The relationship of D-r with matric suction is found to be less dependent on the soil texture.
A quantitative description of water flow and solute transport in the unsaturated zone of the soil is required to predict the impact of human influences on the environment. This paper starts with the basic concepts of the mathematical descriptions of transport processes in homogeneous media. However, water flow and solute transport in natural soils are significantly influenced by the occurrence of (1) macropores and structured elements (micro-heterogeneity), (2) spatial variability of soil properties (macro-heterogeneity) or (3) a combination of (1) and (2). In these cases, the classical representations of water flow and solute transport are not adequate. The paper presents an overview of some recent modelling concepts dealing with water flow and solute transport in heterogeneous media. For each model, we first introduce the underlying physical concept, and then translate the concept into a mathematical model. Each model is illustrated for a specific water flow and solute transport problem. Finally, some applications of the models are discussed. At this moment, it is difficult to specify which model should be used to solve a particular problem since no extensive validation of the models has been performed. Additional research is required to develop accurate and rapid measurement techniques for the necessary input parameters. To be useful in real environmental problems, modelling concepts for micro- and macro-heterogeneity should be coupled in one overall mathematical framework.
Because of salinity, many areas with irrigated farmland have suffered from reduced food and fiber production, especially where irrigation water or soil contains large amounts of soluble salts. In those areas, ridge-furrow tillage is a common practice and furrow irrigation is a popular irrigation method. Effects of water content, temperature, and solute concentration on transport phenomena in soil are hard to predict without complex models. The geometry of a ridge-furrow surface contributes to complexities in heat and vapor transport, and hence, in the distribution of water, temperature, and salt in soil. To improve understanding of water, heat, and solute transport in furrow-irrigated and salt-affected soil, we developed a two-dimensional mechanistic model using the Galerkin finite element method (FEM). The model was designed to consider interactive effects of water content, temperature, and solute concentration on water, heat, and solute transport. To simulate field conditions, an energy balance equation was applied to the ridge-furrow surface to provide boundary conditions for water and heat transport. To utilize a single FEM solver, equations governing transport of water, heat, and salt in soil were generalized as a diffusive-convective type equation. Numerical schemes for the model were tested by comparing simulated results with analytical or semianalytical solutions. Good agreements between FEM and analytically calculated soil water content, temperature, and solute concentration were obtained.
When solving water flow in a soil using Darcy-Richards' equation, information about the unsaturated hydraulic conductivity of the soil is necessary. However, direct measurement of unsaturated hydraulic conductivity is time consuming and expensive. Therefore, instantaneous profile methods and/or models to estimate the unsaturated hydraulic conductivity from water retention data are preferable. However, results of the instantaneous profile methods are often influenced by how precise we express the relation of measured volume wetness with time and the relation of measured hydraulic heads with soil depth. Here, we introduce three regression functions for expressing these relationships. In addition, an empirical model relating the measured unsaturated hydraulic conductivity with volume wetness was also developed. Evaluations of Burdine and Mualem models to predict the unsaturated hydraulic conductivity from the water retention curves were conducted. The results show Burdine and Mualem models can estimate the unsaturated hydraulic conductivity better for the tested soils at lower volume wetness.
(C) Williams & Wilkins 1993. All Rights Reserved.
Microirrigation techniques can be used to improve irrigation efficiency on vegetable gardens by reducing soil evaporation and drainage losses and by creating and maintaining soil moisture conditions that are favourable to crop growth. Water balance experiments in Zimbabwe showed that over 50% of the water applied as surface irrigation on traditional irrigated gardens can be lost as soil evaporation. This result gives an indication of the potential improvement in irrigation efficiency that can be achieved by adopting irrigation methods that reduce soil evaporation at the same time as minimising losses due to drainage and canopy interception. During the period 1985 to 1995, irrigation trials and experiments were carried out in south-east Zimbabwe and northern Sri Lanka with the main aim of comparing and quantifying the benefits of using simple microirrigation techniques on traditional vegetable gardens. This paper reviews the results of these trials and experiments. Microirrigation techniques that were evaluated included low-head drip irrigation, pitcher irrigation and subsurface irrigation using clay pipes. Of these methods, subsurface irrigation using clay pipes was found to be particularly effective in improving yields, crop quality and water use efficiency as well as being cheap, simple and easy to use. The comparative advantages of subsurface irrigation were maintained for a range of crops grown under different climatic conditions. Good results were also obtained with subsurface irrigation when irrigation was carried out using with poor quality irrigation water.
Viability of Pitcher Irrigation
- A R Soomro
Soomro, A.R. 2002. Viability of Pitcher Irrigation. DAWN-Business, 06 May 2002.
www.dawn.com.
Pitcher Irrigation System for Horticulture in Dry Lands. Proceeding of water and land resources development and management for sustainable use II-A. The Tenth Afro-Asian Regional Conference
- B I Setiawan
- E Saleh
- Y Nurhidayat
Setiawan B.I., E. Saleh, and Y. Nurhidayat. 1998. Pitcher Irrigation System for
Horticulture in Dry Lands. Proceeding of water and land resources development and
management for sustainable use. Vol. II-A. The Tenth Afro-Asian Regional
Conference. ICID-CIID, INACID, Denpasar-Bali. Indonesia. 10 p.