Malaysian Journal Of Soil Science

Vol. 02 | April 1998

Tropical Crop Selection Advisory (TROPSEL): A Simple Expert System for Agricultural Land Suitability Evaluation

Pages 1-17
Sahibin Abdul Rahim and W.A. Adams

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Common practice in assessing land potential is to use a land capability or suitability evaluation The FAO Framework of Land Evaluation is often used This rates land according to suitability level, nature of limitation and management requirements It is complex technically and requires experts in the field to understand and to use. This paper discusses a simple computer program which processes data to identify suitable land uses without the need for technical expertise An expert system called TROPSEL was developed from CRYSTAL expert system SHELL computer software The program incorporates a knowledge base comprising the site and soil requirements of 28 tropical agricultural and forest crops obtained from gathered field data and published material Twenty land characteristics have been incorporated in the database. Suitable crops for agriculture are selected by matching crop requirement to known land characteristics TROPSEL provides a rapid and easy method to make an initial selection of suitable crops for a given land area It also allows the user to assess the effect of ameliorating readily altered soil properties on the range of suitable crops. Other crops with known requirements can he added to the knowledge base. No crop profitability or economic criteria have been included in the program, such factors would be considered at a later stage in land use planning An attempt was made to validate the program by relating crops in current production to land use characteristics in relevant areas This did not prove totally successful because economic considerations and the demand for staple foods can have an overriding effect on crop choice.

Keywords: TROPSEL, expert system SHELL, agriculture land, suitability evaluation

Impact of Agriculture on Chemical Properties of Soils on Basalt from Mindanao, the Philippines

Pages 19-29
R. Boniao, E. Van Ranst, J. Shamshuddin and G. Baert

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Uncultivated and cultivated soils from Mindanao, the Philippines were sampled and studied to determine the impact of agriculture on their chemical properties The results of the study showed that cultivated soils, having lost some organic matter due to oxidation, have a lower CEC and a higher point of zero charge (pH0). The capacity of these soils to retain cations has decreased to a certain extent. In the subsoils of both soil types, there is a tendency for soil pH to coincide with pH0, reflecting development of positive charge in the soil of that zone The sum of exchangeable bases and Al (ECEC) is found to be a good estimate of the EC of the soils.

Keywords: Cultivated and uncultivated soils, CEC, pH0, organic matter

Exchange Properties of Highly Weathered Soils of the Lower Congo

Pages 31-44
G. Baert and E. Van Ranst

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These soils of the Lower Congo, i.e. one Alfisol and two Oxisols, were investigated. objectives of this study were (1) to test different methods to determine the electrochemical properties, in particular the cation exchange capacity (CEC), (2) to discuss the variation in CEC with respect to the composition of the colloid fraction. The exchange properties of the soils were determined with 1 M NH4OAc, buffered at pH 7, and with two other methods, the ‘Charge Fingerprint’ the ‘Compulsive Exchange’ method, using an unbuffered solution of 0.002 LaCl2 and BaCl2, respectively, at soil pH. The soils contain predominantly kaolinite and sesquioxides in the clay fraction and little or no weatherable minerals the coarse fractions. The study highlights the impact of the organic matter content on the magnitude of the soils' capacity to retain nutrients. Topsoils rich organic matter may have a CEC several times the level of CEC in the subsoil. This emphasizes the necessity to orient soil management towards maintaining if possible, increasing the organic matter content. The NH4OAc method is commonly overestimates the CEC, compared to the methods measuring CEC under conditions. The NH4OAc method is commonly used in soil classification, has no practical value for fertilizer recommendations and the prediction of management practices Changes in methodologies for CEC determination would have serious implications for soil classification.

Keywords: Exchange properties, tropical soils, soil management, organic matter, Congo

Mineralogical and Charge Properties of Volcanic Ash Soils from West Sumatra, Indonesia

Pages 45-57
D. Fiantis, E. Van Ranst, and J. Shamshuddin

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Four volcanic ash soi1 from two toposequences along Mt Marapi and Mt Talaniau, west Sumatra were studied in order to characterize their mineralogical and charge properties. In all the soils, the silt fraction is composed mainly of gibbsite, cristobalite and feldspars, while the clay fraction is composed mainly of cristohalite, feldspars and halloysite. Gibbsite is only present in the clay fraction of the soils from Mt Talamau, while opal-A is only found in the clay of the soil from Mt. Marapi. Allophane contents, computed from Si and Al extracted by ammonium oxalate and pynophosphate, are lower in the surface horizons than in the subsoil This is related to higher amounts of organic matter in the topsoil Due to higher rainfall, the soils of Mt. Talamau are more weathered than those of Mt Marapi. This is reflected by lower allophane and higher ferrihydrite contents in the soils of Mt. Talamau. In all the soils, the surface horizons have lower pH0, value than die under lying B-horizons. The AEC is higher in the subsoil than in the topsoil, having values of 0.3 - 1.1 cmolc/kg soil.

Keywords: Volcanic ash soils, allophane, charge, selective dissolution

Nitrogen Fixation and Seed Yield of Winged Bean (Psophocarpus tetragonolobus (L.) DC) under Various Support Systems

Pages 59-73
M.R. Motior, Z.H. Shamshuddin, W.O. Wan Mohamad, and K.C. Wong

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A field experiment was carried out to determine the effects of support systems (0, 1, and 2-m height) on nodulation, nitrogenase activity, accumulation and partitioning of total nitrogen (N) and seed yield of a local cultivar of winged bean (Psphocarpus tetragonolobus (L) DC) Plants grown with 2-m supports produced substantial nodule mass, the highest rate of nitrogen fixation, increased nitrogen accumulation of the plant, and seed yield compared to those grown with 2-m supports and unsupported plants Nitrogenase activities increased and reached a peak at the onset of flowering i.e. 70 days of growth (D70) but declined during the pod formation stage in plants grown with a support system. On the contrary, unsupported control plants recorded a peak nitrogenase activities 14 days before flowering The descending order of total plant nitrogen accumulation at D140 was plants with 2-m supports (6.30 g N plant-1) > those with 1-m supports (4.06 g N plant-1) > control plants (2.10 g N plant-1), reflecting the beneficial effect of support systems on N9 fixation as mentioned earlier Supported plants contributed significantly higher leaf N at the vegetative stage Consequently, seed N was also significantly higher than in unsupported plants. There was a seven-fold increase in seed yield for plants grown on 2-m supports compared with unsupported plants The beneficial effects of08-Jan-2015 yield of winged bean are discussed.

Keywords: Nitrogen fixation, seed yield, winged bean

The Gaia Theory in Sustainable Land Use

Pages 75-81
E. Padmanabhan and J.M. Crabtree

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Gaia is a complex entity that seeks an optimal physical and chemical environment for life on this planet. The main function of Gaia is to ensure homeostasis. The inherent nature of Gaia in responding slowly to many changes raises deep concerns with regards to our manipulation of the environment. Preponderance on anthropogenic factors raises the issue of the tenacity of Gaia's main characteristics as well as the applicability of this theory in sustainable land management policies in agro-based systems. Preservation of a self-regulating mechanism (Gala) and the non-disturbance of the component processes constitutes the framework for sustainable land management systems. Individual components and interactions between components must be understood thoroughly in order to preserve Gaia. All sustainable land management systems are components of Gaia Sustainable land management systems have to consider ecosystems that are spatially bigger than the site-specific agro-ecosystems. Non-conformance to this causes degradation of Gaia. Gaia's resilience must be determined to ensure that sustainable land management policies are not working against Gaia. Research paradigms designed towards sustainable land resource management must, therefore, take a gaian approach (truly holistic) in order to ensure that the resources are preserved for future generations.

Keywords: Gaia, cycle, soil genesis, C content, global warming, sustainable land manamgement, soil resilience, research paradigm

Influence of Organic and Inorganic Soil Amendments on Corn Root Growth and Soil Chemical Properties

Pages 83-88
S.R. Syed Omar, I. Zubaidah and J. Shamshuddin

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One of the main constraints to corn production on a highly weathered acid soil is aluminum (Al) toxicity. High Al concentration in acid soils restricts root growth by inhibiting cell elongation and cell division. The objective of this study was to determine the effects of inorganic arid organic soil amendments on corn root growth and soil chemical properties A laboratory experiment was conducted using Bungor series soil (Typic Paleudult) surface sampled (0 - 20 cm) from Puchong farm. Aliquot of the soil (600 g) was treated with legume residues (1% w/w), chicken manure (1% w/w), GML (4 t ha-1), gypsum (4 t ha-1) and control The treated soils were moistened at field capacity (0.25 kg H20 kg-1 soil) and allowed to react for 7 days. Corn seeds (Zea mays L.) were sown and after 5 days root length was measured The results showed that soils amended with GML or chicken manure gave relatively high root length compared to other treatments. The GML and chicken manure treatments increased soil pH and decreased both the soil exchangeable Al and Al-saturation Chicken manure had an additional ameliorative effect over lime in that it increased soil exchangeable Ca, Mg and K.

Keywords: Aluminium, lime, chicken manure, acid soils, corn, amendments