Changes of NaCl and NPK solutions inside and outside the pitcher 

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... four bush peppers were planted in the soil surrounding the pitcher in which NPK solution was inserted. Water level in the pitcher was maintained with mariotte tube. Changes of NPK solution in the soil were sampled and measured analytically, and growths of the plants, height, leaf, flowers, etc., were observed. Finally, the soil then excavated to observe the distribution of roots. These experiments were conducted in a green-house. Figure 1 shows changes of NaCl and NPK solution inside and outside the pitcher when immersed in the container filled with water. The inverse problem to solve Eq.1 with referred to Fig.1 gives D w in the range of 1.01 ∙ 10 -7 ~4.1 ∙ 10 -3 cm 2 /d for NaCl solution and 6.7 ∙ 10 -6 ~3.5 ∙ 10 -3 cm 2 /d for NPK solution, witch were varied with concentration in the form of D w =1∙10 -10 C 9.6832 for NaCl solution and D w =7∙10 -9 C 6.2739 for NPK solution. In both cases, the Saturated Conductivity of the pitcher was 1.01 ∙ 10 -4 cm/d. Hydrodynamic dispersion coefficient for NaCl solution soil, which was measured 2 with the inverse problem of Equation 2, varied in the range of 0.3 to 0.825 cm /d with volumetric water contents of the soil were 0.60  0.04 cm 3 /cm 3 . However, when Equation 2 was solved numerically, the value of the hydrodynamic coefficient had to be adjusted to get good conformity with the measured concentration of NaCl Solution. The best fitted 2 dispersion coefficient was 0.45 cm /d. Figure 2 shows changes of relative concentration of NaCl Solution with distance and time. Profiles of volumetric water content and velocity distribution were obtained by means of solving Darcy and Richa rds’ equation in cylindrical coordinate system. Figure 3 a shows a stable distribution of water content in the soil, which was approximately attained 12.74 days after the initiation of irrigation. Water content was gradually distributed along x- and z-axes, where those regions closer to the pitcher are wetter. With the influence of gravity, moving front to z-axes was longer then that to x-axes. It is clear that in all regions the volumetric water content never reached saturated condition, where in the closest region 3 3 to the pitcher, its value was about 0.67 cm /cm . These results were not far from those reported earlier (Setiawan, 1998) when the saturated conductivity of the pitcher was less then that of the soil. Velocity of water flow in x-and z-direction was obtained in each grid by means of dividing its related flux with the volumetric water content. The velocity varied with location and direction in the range of 0.18144 to 28.5984 cm/d. Correlation of numerical results ( θ m ) and data measured ( θ d ) in some points close to the pitcher obtained θ m = 0.913 ∙ θ d and R 2 =0.81. A cluster of data lower than 0.4 cm3/cm3 was overestimated by the calculation, while other data was well represented. Calculation of solute transfer (Equation 3) was carried out instantaneously after the stable condition of water content was reached as stated before. Figure 3b show concentration profile of NaCl solution in the soil matrices after reaching at a stable condition 8.34 days from the beginning of the application. The similar form of distributions of water content and NaCl concentration was very clear with which it figures out the important of water as the effective medium of the NaCl solution transfer in the soil matrices. Here again, NaCl solution moved farther in z-axes than that in x-axes. The concentration was larger in the regions closer to the pitcher. At 1 cm apart from the pitcher, the relative concentration reached 0.89 while at the moving front was about 0.10. Correlation of numerical results ( C m ) and data measured ( C d ) in some points close to the pitcher obtained C m = 0.874 ∙ C d and R 2 =0.81. Data was unevenly distributed in two clusters. One cluster was in the range of 0.2-0.4 while the other concentrated at 0.8. There was no data capable to measure between 0.4-0.8. Figure 4 shows irrigation rate from one pitcher surrounded by four bush peppers. The irrigation rate fluctuated with time. The lowest and highest rates were 0.56 and 1.30 l/d, respectively with the averaged was 0.81 l/d, which is equal to 2.33 mm/d. While, evapo-transpiration rate which was measured independently were 1.9 to 4.3 mm/d with the average was 2.8 mm/d. With these values indicate that the irrigation rates much or less equals to the evapo-transpiration of bush peppers, or could meet the water demand of bush peppers for their growth and developments. Wet regions in the soil matrices formed like a standing oval-ball with a longer radius of 25 cm and vertical length of 70 cm. Nitrogen content was distributed evenly in the soil matrices at ranges of 0.09 to 0.12%. Farther from the pitcher, Phosphor content decreased significantly, from 27 to 6.3 ppm. Potassium content changed abruptly but tended to decrease with distance, form 4.99 to 4.03 me/100g. Roots were concentrating up to depths of 15 cm and its density decreased with depth and there were no roots anymore at 65 cm. Up to the depth of 10 cm, cumulative wet roots amounted to 50 gram. Bush peppers grew rapidly to 60-70 cm heights in 30 weeks but then slow downed and only reached 65-75 cm in 5 days later. The maximum height was around 90-120 cm. Leaves development also followed these tendencies with the total number of leaves was 60-85 pieces. New branches started from 1 up to 35 weeks amounted to 13-16 branches. Flowers commonly appear when a new braches is coming out but old branches also produce flowers. Here, flowers increased linearly with time amounted to 7 flowers in 12 days but then constant up to 27 weeks, and amounted to 9 in 35 weeks. From these figures, the generative phase of bush peppers was higher than that of conventional farming using spraying irrigation. In another experiment when the dosage of NPK was decreased to 50%, there were no significant differences of bush peppers’ growth and developments. Thus, it is possible to save fertilizer that was commonly used conventionally. Pitcher fertigation has been examined for cultivating bush peppers in a green house. The pitcher which had saturated hydraulic conductivity 1.01 ∙ 10 -4 cm/d, diffusion coefficient 6.7 ∙ 10 -6 ~3.5 ∙ 10 -3 cm 2 /d for NPK solution could meet water demand and supply fertilizer sufficiently for the growth of the bush peppers. Water flow as well as solute transfers in the soil matrices could be determined theoretically using a combination of Darcy and Richards’ equation and the convection -dispersion equation. Water as well as fertilizer was concentrated and formed like a ball in the soil matrices surrounding the pitcher where most of the roots of bush peppers resided. Bush peppers could grow well as indicated by the developments of roots, leaves, branches and flowers. It is possible to reduce the dosage of fertilizer application that conventionally applied without the risk of decreasing yields. Batchelor Ch., L. Christopher, and M. Monica. 1996. Simple micro-irrigation techniques for improving irrigation efficiency on vegetable garden. Agricultural Water Management. Elsevier.32 : 37-48. Bear J, and A. Verruijt. 1987. Modeling Groundwater Flow and Pollution. D. Reidel Pub. Co. Tokyo, 414 p. Feyen J., D. Jacques. A. Thimmerman, and J. Vanderborght. 1998. Modeling water flow and solute transport in heterogeneous soils, A review of Recent Approaches. J. agric. Eng. Res. 70: 231-256. Hermantoro (2004). Affectivity of pitcher fertigation system: A case study on bush peppers. Dissertation. Graduate School of Bogor Agricultural University. In Mehta, K. B., Sho Shiozawa and Masashi Nakano. Measurement of Molecular Diffusion of Salt in Unsaturated Soils. 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On the determination of unsaturated hydraulic conductivity from soil moisture profiles and front water retention curves. Soil Science. 156: 389-395. 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. Stein, Th. M. 1997. The influences of evaporation, hydraulic conductivity, wall thickness and surface area on seepage rates of pitcher irrigation. Journal of Applied Irrigation Science (Zeitschrft fur bewasserungswirtscgaft) 32 (1): 65-83. In ...