Soil texture is relative comparison of three major particle groupings in a soil mass. Singular grains are called soil particle whereas combinations of particles are called soil fractions. Clay fractions are soil fractions with very fine particles measuring (less than) < 0.002 mm. Silt fractions have a diameter of 0.002 – 0.05 mm while the biggest from is sand fractions with particle diameter of 0.05 – 2.0 mm. Soil mass particles can be made up of all three of these types of particles. Soil is considered having a rough texture where the mixture of particles is mainly sand and the proportion of the other particle types is negligible and can be ignored. In soil with medium texture the soil is dominated by silt particles and soil with a dominance of clay particles is classified as fine soil. These are the three simple soil texture classifications and these textures rarely vary. Because these characteristics are permanent these textures have become the basis for soil classification.The soil of Bali Island is dominated by soil of medium texture and that only minor areas have fine or rough texture. Soils with fine texture can be found at Nusa Dua while soil with rough texture can be found on the island of Nusa Penida which is still a part of Klungkung Regency.
The Latosol soil type covers 44.59% of the total area of Bali and is found in Denpasar City and the Regencies of Badung, Tabanan, Jembrana, part of Karangasem, Buleleng and Klungkung. Latosol soil is soil that has undergone intensive breakdown and development of advanced soil. Specifications: this soil is shades of red raging from red to a reddish yellow or to reddish brown with a pH of $.5 – 6.5, with a fine to medium texture and a structure which is crumbly to slightly sticky, with deep permeability and soil fertility which is low to medium.
Regosol soil which covers 39.92% of the area of Bali Island is divided into volcanic ash regosol (found around volcanoes), regosol sand hills (along the beaches) and regosol sedimentary rock (found around folded hill topography). Generally, regosol soil type is rich in phosphorous and kalium but poor in nitrogen. However the phosphor and kalium are in form which is not ready to be absorbed by plants because they have not yet broken down so that this soil needs organic fertilizer in the form of animal droppings or compost to speed up its breakdown. The acidic level or pH of regosol is around 6 – 7. As it ages the structure and consistency become increasingly solid and even sometimes forms a layer with a porosity and drainage capacity that is restricted or in other words, difficult for water to pass through. Generally this regosol soil type has not yet formed an aggregate so that it is sensitive to erosion. In Bali regosol can be found in the regencies of Gianyar, Bangli, most of Karangasem, part of Klungkung, Boleleng and Denpasar.
Mediterranean soil is classified as red soil type that has undergone soil formation for a long period. This soil has an alkaline character with a pH of 5.5 – 8.0. This soil type contains hardened calcium and iron, has deep permeability and sticky structure but in spite of this has medium to high fertility. This kind of soil can be found at Nusa Penida and Nusa Dua.Aluvial soil is land which has often or recently undergone a food so that it can be considered young and has not yet undergone horizontal differentiation. Because it has been formed by flooding the characteristic of the soil is depend on the level, origins and material types carried by the flood so that its level of fertility really depend on the material’s origins. Soil of this type only covers 4.87% of the land area of Bali and is mostly found in the western coastal areas.
The Andosol soil found around Lakes Buyan, Tamblingan and Brittan is of a type of Black soil. The word ando comes from the Japanese language and means dark or black. Andosol contains of high level of organic material with high carbon and nitrogen levels but a low level of phosphorous. Andosol has a high water absorption capacity so that it is always saturated if covered by vegetation. This soil type breaks up very easily but has resilient structure so that it is easy to handle. The high permeability is caused by the fact that it contains abundant micropores.
The interaction of soil and agroclimate
When it comes to growing things soil can become the sole factor in determining the suitability of an area for certain commodities. The interaction of soil and agroclimate which include the factor of air, humidity, light intensity and rainfall in the area become interacting factors that influence plant metabolism in order to produce the organs of a plant such as leaves, flowers and fruit. It’s the result of this metabolism which makes the final effect on the quality of a commodity and the taste of its fruit or vegetable.
The soil factor can be modified with soil treatment, fertilizing, applying lime and irrigation but the factor of climate can only be modified by building glass and plastics houses or shade houses to create a micro-climate around the plants. For the small farmer with limited capital these houses are of course not economical. The following is an explanation of how the interaction of soil and agroclimate in the regencies that makes them suitable for the planting of specific commodities.
Farming potentials of the Balinese soil and problems
A. Buleleng Regency
Buleleng Regency’s soils are dominated by Latosol and Regosol, and the area has a rainfall of 2.431 mm / year with an average temperature of 27 C making it an area that is potential for farming. Around 1975 Buleleng was making great headway with keprok Tejakula oranges (Tejakula being the name of the district in which they were grown). This condition was spurred on by the attack of the CVPD virus which destroyed orange trees in Java so that the numbers of trees in Buleleng reached 6 million trees. But in 1983/1984 the CVPD virus also attacked trees in Bali wiping them out completely. From then on there has been the development of grapes has spread in Buleleng so that until now Buleleng has become the centre for grape production in Bali.
Grapevines are suitable and grow well in areas from a height of 0 – 300 m above sea level, with temperatures of 25 – 31 C; a humidity of 40 – 80 %; rainfall 800 mm / year and in a sandy soil with a pH 6.5 – 7.0. If we see from the specifications for growth Buleleng should be suitable for growing grapes and the districts of Grokgak, Seririt and Banjar have become centres for grape growing. The problem faced by growers is attacks funguses in the wet season which result in the fall of fruit quality so that they fail to be competitive with imported grapes in the market. Beside this there is a lack of technology for turning the fruit into grape juice, raisins and other products. Wineries are also limited in number and these are mostly owned by foreigners. Formerly Buleleng was known for its rice which had nice flavor and texture and the emergence of vineyards has lead to a drop in its production so that it is difficult to find Buleleng rice in the market.
The village of Pancasari in Sukasada District of Buleleng Regency is a highland area on the shores of Lake Buyan and is most widely known for its strawberry production but this area also produces high quality, highland vegetables such as cauliflowers, cabbages, carrots, potatoes, and others. Strawberries (Fragaia veesca L) attain optimal growth in areas at a height of 1000 – 1500 m above sea level (asl), with a noon temperature of 22 – 25 C and overnight temperature of 14 – 18 C and with a humidity of 85 – 95 %. These condition need to be supported by porous soil with a high organic content and a pH of 5.8 – 6.5.
The soil around Lake Buyan is black, porous Andosol soil with high organic content and in combination with the height of Pancasari at 1.100 asl, a noon temperature of 23 – 26 C and night time temperature of 18 C it is in fact ideal for growing strawberries and it is not surprising that the strawberries in the supermarkets of Denpasar generally come from here. As well as this Chrysanthemums and orchids are also grown here. The orchid Phaphiopedilum and Cymbidium which cannot be grown in the low lands is brought to flower here sent to markets all over Bali, especially to Denpasar.
Buleleng Regency is also known for its production of Mangoes (Mangifera indica L.) The interaction of soil and agro climate make Buleleng very suitable for their growth and when the harvest time comes from October to June with its peak from November to December the mangoes of Buleleng dominate the supermarkets and traditional markets of Denpasar. It’s a pity that the farmer’s knowledge about the techniques for growing of commodities is not good because if the government were to provide impetus for the mango agribusiness Buleleng could become a major world producer of mangoes with suitable qualities and quantities.
B. Tabanan Regency
Tabanan Regency has medium textured Latosol soil, a rainfall of 2,723.5 mm / year an average temperature of 27 C and is the rice production centre of Bali as it produces 90% of Bali’s rice. Even though the area of rice fields in Bali has been reduced in the last 5 years, this area with its organized subak is still very productive especially in the Guama Subak in Marga District and the ‘Rejasa’nya subak in Penebel District which are both lowland areas and very suitable for rice production.
Tabanan Regency also has a highland area in Baturiti District which borders on Pancasari village in Sukasada District at a height of 1,100 m asl. This area is a centre for the production of highland vegetables of the Brassicaceae varieties such cauliflower, sawi, broccoli, cabbages and others. These highland vegetables, whether grown in Pancasari or Baturiti are facing the same problem of a reduction in quality caused by plant diseases and there is also a problem with the supply of seedlings. Only carrot seedlings can be produced locally and other seedlings must be bought at high prices from other countries. The problem of seeding production, especially for Brassicaceae varieties is a general problem in Bali as it is only possible to produce them with quality in areas with a high temperature fluctuation between night and day temperatures.
With soil and agroclimate conditions of Tabanan Regency it is also possible to plant mangostein (Garcinia mangostana L.). This flavored fruit with its unique shape is very popular everywhere making it an excellent prospect for export as a Balinese tropical fresh fruit.
C. Jembrana Regency
Jembrana Regency is an area dominated by medium textured Lasotol soil with an average annual rainfall 2,585 mm, a mean temperature of 28.4 C but until now it has not become known for the production of any specific commodity. In spite of this if we see the soil conditions and agro climate of the area are suitable for mixed cropping of corn and beans.
D. Karangasem Regency
Karangasem Regency is renown throughout Indonesia and the world as the area for the production of Salak Bali. This dry area having a rainfall of only 197 mm / year and average daily temperature of 27 – 50 C, and predominantly medium textured regosol soil has an agroclimate that is in fact highly suitable for the production of salak, especially the Salacca edulis salak which falls into the category of Palmae plant type.
As with other Palmae species the salak does not require intensive fertilizing as the salak only requires small amounts of organic fertilizers such as animal droppings. With prices for chemical fertilizers such as nitrogen, phosphate, and kalium being expensive this factor makes the salak really worthwhile for farmers. From the point of view of the environmentally friendly and prevents damage to the soil that would come from their use.
There are three salak producing areas in Karangasem including Duda, Manggis and Sibetan villages although Sibetan village is actually located in the District of Sidemen. It was from these villages that the Balinese salak first originated and which has now spread to other places in Bali. The interaction of agro climate and soil of an area are a specific factor in the production of commodity and it is for this reason that the Sibetan salak had a different flavor and was not as nice when it was tried in Pekutatan in Tabanan Regency.
Source: The Soil of Bali Island and Potentials for Farming by Rindang Dwiyani in Indonesian Geographical Expedition 2007, National Coordinating Agency for Survey and Mapping.
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