Abstract: Background and Objective: Soil quality assessment is one way to formulate strategies to improve the quality and sustainability of land and productivity of the crop. This study aimed to determine parameters of soil quality that affect the yield of cloves, cocoa and cardamom in the agro-forestry system in Menoreh mountains area. Methodology: The stratified random sampling method was used during the research by stratifying the types of soil stratification in Menoreh mountains area, Samigaluh district, Kulonprogo regency, i.e. Yogyakarta, Indonesia that were Lithic Eutrudept, Vertic Haplustalf and Typic Hapludult. The observations were made on 24 physical, chemical and biological properties of soil and the yield of clove, cacao and cardamom. The determination of soil quality indicator was done by using one-way ANOVA at α 5%, factor analysis and standardized stepwise regression. Results: The result shows that the highest dry weight of clove flowers is produced in the soil type of Vertic Haplustalf, sequentially followed by soil types of Typic Hapludult and Lithic Eutrudept. The highest dry weight of cocoa beans and cardamom bulb is produced in the soil type of Vertic Haplustalf, sequentially followed by soil types of Lithic Eutrudept and Typic Hapludult. Conclusion: The dry weight of clove flowers is affected by the percentage of silt fraction of the soil. The dry weight of cocoa beans is influenced by the content of CEC, Ex-Ca and Ex-Na, while the dry weight of cardamom bulbs is influenced by the content of Ex-Ca.
INTRODUCTION
Menoreh mountains area is a mountainous area that stretches in the West of Kulonprogo regency, East of Purworejo regency and a part of Magelang regency. People in Menoreh mountains area are mostly dry land farmers due to limited irrigation flow. Farmers try to meet various needs: Food, fuel, building timber, animal feed and non-timber forest products with agro-forestry1.
Plant commodities that are the mainstay of the community in the mountains are clove, cocoa and cardamom in the agro-forestry system. In general, agro-forestry practices that are developed by the community are still considered not productive and innovative. This is reflected in the variation of clove, cocoa and cardamom. One of the most decisive factors of clove, cocoa and cardamom is soil quality2.
An understanding of soil quality is important to identify problem areas, assess sustainable agricultural management and provide early warning signs of adverse trends3-5. Soil quality indices are tools for adaptive soil resource management that can help farmers and their advisors to determine soil health trends and thereby indicate whether one or more changes in practice are necessary6. Soil quality is the basis for improving sustainable land use management7,8, evaluating the sustainability of soil management practices9,10, providing early warning signs of adverse trends11 and an estimation of the potential reduction in costs was carried out12.
The assessment of soil quality could not be done directly; therefore knowing indicators of soil quality is important. Indicators of soil quality can be measured from the physical, chemical and biological properties of the soil. Physical, chemical and biological properties of the soil that can influence soil production and are sensitive to environmental changes are typically chosen as soil quality indicators12,13. Biological and microbial indicators, in particular, have recently attracted more attention, owing to their use in evaluating the short-term effects of environmental changes on soil function14,15. Several soil quality indicators together produce a comprehensive soil quality measurement known as the minimum data set (MDS)16.
Specialists have agreed to search for a MDS to reduce the cost of soil quality assessment17,18. Qi et al.8, evaluated soil quality at a county scale and showed that using an integrated quality index and MDS method can adequately represent the total data set and save time and money. Meanwhile, more attention should be focused on farmers’ local knowledge, which is crucial to maintain soil quality and developing sustainable land management19,20. MDS is applied to compare the effect of land management systems on soil quality in various locations21.
Various studies on soil quality assessment indicators using MDS have been conducted22, each study producing MDS for different land valuation indicators. Differences in MDS combination are due to the diversity of location, scale and purpose of the study23. On the basis of this consideration, in the case of different land management, the combination of MDS used to assess the quality of the soil also varies.
The assessment of soil quality determinants is a promising tool for monitoring and evaluating the effects of different soil types on the crop performances in terms of both biological and economic yields. This study aimed, therefore, to determine the soil parameters that could be used to relate and furthermore to predict the productivity of clove, cocoa and cardamom, especially in the agro-forestry system on Menoreh mountains area, Indonesia.
MATERIALS AND METHODS
Study area: This study was conducted in Menoreh mountains area, Samigaluh district, Kulonprogo regency, special Province of Yogyakarta, Indonesia. The study period starts from September, 2013 until August, 2014. Menoreh mountains area is located ±40 km to the West from downtown Yogyakarta, Indonesia. The height of the Menoreh mountains area varies from 250-1000 m above sea level. The average air temperature ranges between 25-28°C and the average rainfall ranges from 2000-2400 mm/year. The soil moisture regime belongs to the udic group2.
Soil sampling and analysis: Soil sampling is conducted on 3 dominant soils in Menoreh mountains area at a depth of 0-60 cm. Each type of soil consists of 6 strata. Soil sampling is done randomly as many as 6 samples in each stratum before being composited. The observations were made 4 times a year from September, 2013-August, 2014. The observation variables include the physical, chemical and biological properties of the soil. The observations were conducted directly in the field and at the General Soil Laboratory, Faculty of Agriculture, Universitas Gadjah Mada, Yogyakarta, Indonesia. Detailed components of each variable and its protocol indicated in Table 1.
Observations at clove, cacao and cardamom harvest: Clove observation was conducted on the dry weight of clove flowers, dry weight of cocoa beans without pulp and on dry weight of cardamom bulb.
| Table 1: | Protocol of measurements for each indicator |
The observation of dry weight of clove flower and dry weight of cardamom bulbs was done at harvest time in July-August. The observation of dry weight of cocoa beans without pulp was done during June-August, which is the peak of cacao harvest. The observations were made on 10 samples of clove, cocoa and cardamom plants and repeated 6 times.
Statistical approach: The stratified random sampling method was used during the research by stratifying the types of soil stratification in Menoreh mountains area, Samigaluh district, Kulonprogo regency, Yogyakarta, Indonesia, which were Lithic Eutrudept, Vertic Haplustalf and Typic Hapludult. Comparative analysis of clove, cocoa and cardamom yields on each soil type was performed with one-way ANOVA at 5% and followed by HSD-Tukey at α 5%39. The production of clove, cacao and cardamom was done visually by Prism 5 software. The approach used to determine the relationship between soil parameters and the common factor (soil quality) was with the analysis factor on soil parameters which showed a real difference and has a coefficient of diversity <40% based on the result of one-way ANOVA at α 5%. The number of components were determined by the eigen value-one criterion40. Moreover, a Scree test was performed to corroborate primer results41. A varimax rotation was performed to enhance the interpretability of the uncorrelated components42. Furthermore, standardized stepwise regression on soil parameters of screening results of factor analysis was also performed16.
RESULTS AND DISCUSSION
Selection of key soil quality indicators: Determination of key indicators of soil quality that affect the yield of clove, cacao and cardamom is started with screening using analysis of variance at α 5% then continued with factor analysis and standardized stepwise regression. The results of analysis of variance on physical, chemical and biological variables of the soil showing significant differences and having a coefficient of variation <40% is maintained for continued factor analysis.
Based on the results of analysis of variance on soil properties of land tax variables that show significant differences (p<0.05) are the percentage of silt and clay, bulk density (BD), available soil moisture (ASM) and soil permeability (Perm). The soil chemical properties variables that show significant differences p<0.05 are pH H2O, cation exchange capacity (CEC), electrical conductivity (EC), exchange calcium (Ex-Ca), exchange magnesium (Ex-Mg), exchange sodium (Ex-Na), exchange aluminium (Ex-Al) and exchange iron (Ex-Fe) (Table 2).
Multivariate statistical techniques are often appropriate and useful to choose the most representative properties that account for the highest variability in the total data set from large existing data, to obtain much more information from soil data9,43,44. In this study, the multivariate analysis used factor analysis and standardized stepwise regression. Determination of relationships between parameters and factors which become common factor in pattern of correlation between variables can be known by factor analysis. Factor analysis is the commonly used because of its ability to group related soil properties into a small set of independent factors and to reduce the original data set45.
The result of factor analysis shows 2 set of the quality factor of soil formed (Table 3). Factor 1 consists of Ex-Ca, pH H2O, Ex-Al, CEC, BD, Ex-Fe, ASM and Ex-Na. Factor 2 consists of Ex-Na, silt, clay, perm and EC. The first and second factors show the Ex-Ca and silt having the highest positive value of 0.990 and -0.983, respectively (Table 3).
| Table 2: | Analysis of variance (ANOVA) of physical, chemical and biological properties of soil |
Number followed by the same letter in the same column were not significantly different by HSD-Tukey α 5%. The bars was indicated Standard Error of Mean (SEM) | |
| Table 3: | Factor analysis after varimax rotation method |
| *Significant soil’s parameters in each soil set factor | |
Andrews et al.45 and Imaz et al.46 obtained a minimum data set of indicators from a total data set using factor analysis and reported a high consistency in soil quality evaluation between the two data sets. The final result of the factor analysis informs that all parameters are eligible to proceed to the stepwise regression analysis since it has a communality value of higher than 0.542.
The end point of this study is to determine the soil quality by separating the effect of soil properties that have clove, cocoa and cardamom. Soil quality is the result of physical, chemical and biological properties. The result of the factor analysis is used to determine the parameters used for the stepwise regression analysis. The result of standardized stepwise regression shows that clove yield is influenced by the percentage of silt fraction. Cocoa yield is influenced by CEC, Ex-Ca and Ex-Na contents in the soil, whereas cardamom yield is influenced by Ex-Ca content in soil (Table 4).
Yield of clove, cocoa and cardamom: The results show that there were significant differences in the yields of cloves, cocoa and cardamom. The dry weights of clove flowers in Vertic Haplustalf were significantly higher (p<0.05) than Lithic Eutrudept and Typic Hapludult (Fig. 1). The dry weights of cocoa beans in Vertic Haplustalf were significantly higher (p<0.01) than Lithic Eutrudept and Typic Hapludult (Fig. 2). The dry weights of cardamom bulb in Vertic Haplustalf were significantly higher (p<0.05) than Lithic Eutrudept and Typic Hapludult (Fig. 3).
The difference is due to different types of soil in the study sites. Based on the results of the soil horizon interpretation on each soil profile, it indicates that the soil at the study site is included into the type of Lithic Eutrudept, Vertic Haplustalf and Typic Hapludult. Lithic Eutrudept have a cambic horizon. These soils are the base saturation of >60% in the upper 75 cm or free carbonates throughout the soil, that has a lithic contact within 50 cm of the mineral soil surface47.
| Table 4: | Standardized stepwise regression analysis |
| **Significant at α 5%. *Significant at α 1% | |
| Fig. 1: | Dry weight of clove flowers. LE: Lithic Eutrudept, VH: Vertic Haplustalf, TH: Typic Hapludult |
| The bars was indicated Standard Error of Mean (SEM) | |
| Fig. 2: | Dry weight of cocoa beans. LE: Lithic Eutrudept, VH: Vertic Haplustalf, TH: Typic Hapludult |
| The bars was indicated Standard Error of Mean (SEM) | |
Vertic Haplustalf have an argillic (clay accumulation) horizon with a significant decrease (p<0.05) in clay content within a depth of 150 cm. These soils are the more or less freely drained Alfisol that has seasonally well-distributed precipitation (udic moisture regime) and cold to warm temperature regimes. Vertic Haplustalf have cracks within 125 cm of the mineral soil surface that are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years and slickensides or wedge-shaped peds in a layer of 15 cm or more thick that has its upper boundary within 125 cm of the mineral soil surface47.
| Fig. 3: | Dry weight of cardamom bulbs. LE: Lithic Eutrudept, VH: Vertic Haplustalf, TH: Typic Hapludult |
The bars was indicated Standard Error of Mean (SEM) |
|
Typic Hapludult has an argillic (clay accumulation) horizon and a significant decrease in clay content within a depth of 150 cm. These soil are the more or less freely drained, humus-poor Ultisol in humid areas with seasonally well-distributed precipitation (udic moisture regime). Most have light-coloured upper horizons and commonly a greyish horizon that rests on a yellowish brown to reddish argillic (clay accumulation) subsoil horizon47.
Lithic Eutrudept has the main rock consisting of a conglomerate, marl and lime stone with lignite inserts. These rocks are formed in the lower Miocene tertiary period that is about 11-25 million years ago. Vertic Haplustalf and Typic Hapludult have a parent rock with Alluvium type. These rocks formed during the upper Oligocene period up to the lower Miocene i.e. about 25-40 million years ago48.
The dry weight of clove flowers is influenced by soil texture, especially the percentage of silt fraction. Lithic Eutrudept shows the highest percentage of silt and significantly different from Vertic Haplustalf and Typic Hapludult (Table 2). The low dry weight of clove flowers on Lithic Eutrudept was due to the high percentage of silt (59.81%). This result causes low available soil moisture and many nutrients are lost due to leaching.
Soil texture is the relative proportions of sand, silt and clay and also includes particles larger than sand in soil. These proportions describe the classes of soil texture with a textural triangle. It has a large influence on water holding capacity49,50, water conducting ability, soil structure51, chemical soil properties and the relative stabilization of soil organic matter52-54. Moreover, the proportions of sand, silt and clay can significantly correlate diversely with crop yield55,56.
The dry weight of cocoa beans is influenced by the soil chemical properties of CEC, Ex-Ca and Ex-Na, whereas the dry weight of cardamom bulb is influenced by Ex-Ca. CEC and Ex-Ca on Vertic Haplustalf showed the highest value, followed by Lithic Eutrudept and Typic Hapludult. Ex-Na highest in Vertic Haplustalf compared to Lithic Eutrudept and Typic Hapludult.
CEC is used as a measure of soil nutrient retention capacity and the capacity to protect groundwater from cat-ion contamination57. It buffers fluctuations in nutrient availability and soil pH58. Plants obtain many of their nutrients from the soil by an electrochemical process called cat-ion exchange. This process is the key to understanding soil fertility59. Nutrients that are held by charges on a soil are termed 'exchangeable' as they become readily available to plants59.The higher the CEC of soil, the more nutrients it is likely to hold and the higher will be its fertility level60.
Cui et al.61 reported that the higher the smectite content in bentonite, the higher the cation exchange capacity (CEC) of the soil. The results of X-Ray Diffraction (XRD) show that Lithic Eutrudept is dominated by clay type smectite minerals. Vertic Haplustalf and Typic Hapludult is predominantly by kaolinite clay minerals2.
The role and function of Ca in the development and growth of plants especially in the participation of many processes, such as formation of the cell wall and plasma membrane cell growth and secretion62. If the CEC of the soil is too high, the Ca in the pore solution of the stabilized soil does not reach the saturation level and further cat-ion exchange would then consume the Ca2+ ions which should be originally used to generate calcium silicate hydrate, thus resulting in the poor strength of the stabilized soil63.
Sodium cycling through plants and the overall environment can be a critical factor influencing the productivity of biological systems64. Sodium appears to play a critical role in the regeneration of phosphoenolpyruvate (PEP) in mesophyll chloroplasts of Amaranthus tricolor65. Also, for many C4 plants, Na has been reported to take part in chlorophyll synthesis66. Sodium deficiency has been reported to impair this conversion of pyruvate to PEP, which takes place in the mesophyll chloroplasts67.
Over the past few decades, fertilizer addition has been widely used as an intensive management practice in clove, cacao and cardamom in Menoreh mountains area and fertilization application is expected to continue to increase68.
CONCLUSION
The dry weight of clove flowers in Vertic Haplustalf was significantly higher than Lithic Eutrudept and Typic Hapludult. The dry weight of cocoa beans in Vertic Haplustalf was significantly higher than Lithic Eutrudept and Typic Hapludult. The dry weight of cardamom bulb in Vertic Haplustalf was significantly higher than Lithic Eutrudept and Typic Hapludult. The dry weight of clove flowers is influenced by soil texture especially the percentage of silt fraction of the soil. The dry weight of cocoa beans is influenced by soil chemical properties especially CEC, Ex-Ca and Ex-Na while the dry weight of cardamom bulb is influenced by Ex-Ca. The application of organic materials should be done as a strategy for yield improvement of clove, cacao and cardamom agro-forestry system in Menoreh Mountains Area, Indonesia.
SIGNIFICANCE STATEMENT
The results of this study can be used as information to determine appropriate, practical and efficient land management practices to improve the productivity of cloves, cocoa and cardamom in Menoreh Mountains Area.
ACKNOWLEDGMENT
The author would like to express his profuse thanks to Agency for Research and Community Service Universitas Gadjah Mada which has funded this research through the University grant-in-aid scheme (No: LPPM-UGM/869/LIT/2013).