Reprinted from the Journal of Natural Resources and Life Sciences Education Vol.25, no. 1 (Spring 1996)
Liming Material Selection by Computer Spreadsheet Zhi-Cheng Li, I P. G. Widjaja-Adhi, T. S Dierolf, and R. S. Yost* ABSTRACT Lime selection considerations are complex and may be simplified with the aid of a computer spreadsheet with optimization capability. A mathematical model was formulated using linear programming techniques that included lime-quantity, liming depth, lime cost, lime quality (calcium carbonate equivalence and fineness), amount reacted after 3 'ino, Ca content, Mg content, distance of transport, and transportation cost per unit distance for each of five liming materials. Program results were tested with situations and data from previous experience in Sitiung, Indonesia. The prediction and associated sensitivity analysis was useful in planning liming operations and should provide a useful tool to explore lime management options. The spreadsheet model should aid learning about the various components and complicating factors important in selecting liming materials and techniques to merge the considerations into a single lime recommendation.
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OIL ACIDITY CONTINUES to limit agricultural productivity in the tropics because of inherent acidity and intensive cropping. Although modern approaches to acidity management include acid tolerant germplasm and, in some cases, the use of organic materials to reduce acidity, the need for limestone neutralization of acidity continues. An estimated 33% of soils of the tropics are Oxisols and Ultisols, many of which need limestone applications to alleviate yield restricting effects of acidity (Sanchez, 1976). Lime recommendations for highly weathered tropical soils are commonly based on reducing soil aluminum saturation, (extractable Al + H)/(effective cation exchange capacity) x 100, below a critical level for a given crop. The Acidity Decision Support System (ADSS) (TropSoils, 1991) is an expert system that determines lime requirements for various crops grown on highly weathered tropical soils based on Al saturation of the soil and Al tolerance of the crop. However, the process of making lime recommendations is complicated by additional factors such as maintaining adequate soil Ca and Mg levels within a range of Ca/Mg ratios (Souza and Ritchey, 1988; Cochrane, 1989), cost and availability of liming and fertilizer materials, and cost of transportation. The average individual would have difficulty accounting for all these factors while attempting to minimize cost. We show, however, that spreadsheet and linear programming tools available in many commercially available spreadsheets such as Quattro Pro, Excel, and Lotus 1-2-3, can simplify this problem. Usually Ca/Mg ratios have little importance when soil acidity is neutralized and sufficient Ca and Mg levels are
Z.-C. Li, Univ. of Hawaii, 1910 East West Road, Honolulu, HI 96822; I P.G. Widjaja-Adhi, Centre for Soil and Agroclimate Research, Bogor, Indonesia; T.S Dierolf, Jalan Kehakiman no. 283, Bukit Tinggi, Sumatra, Indonesia; and R.S. Yost, Univ. of Hawaii, 1910 East West Road, Honolulu, HI 96822. Hawaii Inst. for Tropical Agric. and Human Resources Technical Paper No. 4117. Received 26 July 1994. 'Corresponding author (
[email protected]). Published in J. Nat. Resour. Life Sci. Educ. 25:26-30 (1996).
26 • J. Nat. Resour. Life Sci. Educ., Vol. 25, no. 1, 1996
ensured (Lopes, 1983; Souza and Ritchey, 1988; Cochrane, 1989). Nevertheless, some acid soils of the tropics contain such small amounts of Ca and Mg that imbalances can occur. In the Brazilian Cerrado the least productive vegetation group, cerrados, was characterized by Ca/Mg ratios 3.0 (Cochrane, 1989). On an acid Oxisol, neutralization of acidity with MgCO3 resulted in soybean grain yields of less than 100 kg ha"1 while neutralization with CaCO3 produced average yields of 2100 kg ha~" (Souza and Ritchey, 1988). These authors suggested that low yields where acidity was neutralized with MgCO3 was due to excessive soil Mg in relation to soil Ca that resulted in a Ca/Mg ratio
