PENILAIAN KESESUAIAN LAHAN UNTUK IRIGASI

EVALUASI LAHAN UNTUK IRIGASI Di daerah iklim arid dan semi-arid, di daerah penelitian, menurut hasil klasifikasi iklim, metode yg paling relevan untuk memperbaiki produksi pertanian adalah “IRIGASI”. To decide where and how to irrigate, natural conditions, available types of crops and technology, previous experience, costs and benefit analysis, should be considered. Untuk meminimumkan dampak negatif akibat praktek irigasi, seperti erosi tanah dan salinisasi, maka diperlukan sistem evaluasi untuk tujuan irigasi. Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm

EVALUASI LAHAN UNTUK IRIGASI Metodologi Sistem Parametrik digunakan untuk mengevaluasi kesesuaian lahan bagi penggunaan irigasi (Sys et al., 1991); metode ini didasarkan atas granulometrical baku dan karakteristik fisika dan kimia tanah. Evaluasi dilakukan untuk estimasi kesesuaian lahan untuk irigasi permukaan sekala kecil, sehingga tidak melibatkan teknik-teknik seperti “drop irrigation”, yang mungkin akan memberikan hasil evaluais yg berbeda. Only potential land characteristics were taken into account but nothing is here reported about effective irrigation possibilities, i.e. about irrigation water availability. Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm

EVALUASI LAHAN UNTUK IRIGASI Faktor-faktor yg mempengaruhi kesesuaian tanah untuk irigasi dapat dikelompokkan menjadi empat golongan: Ciri-ciri Fisika tanah, that determine the soil-water relationship in the soil such as permeability and available water content (both related to texture, structure, soil depth and calcium carbonates status); Ciri-ciri Kimia Tanah, that interfere in the salinity/alkalinity status, such as soluble salts and exchangeable Na; Ciri-ciri Drainage; Faktor Lingkungan, seperti lereng. Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm

EVALUASI LAHAN UNTUK IRIGASI The different land characteristics that influence the soil suitability for irrigation are rated and a capability index for irrigation (Ci) is calculated according to the formula: Ci = A/100 * B/100 * C/100 * D/100 * E/100 * F/100 dimana: Ci: Indeks kapabilitas untuk irigasi; A: nilai tekstur tanah; B: nilai kedalaman tanah; C: nilai status CaCO3 ; D: nilai salinitas/alkalinitas; E: nilai drainage dan F: nilai slope. Kelas kapabilitas didefinisikan menurut nilai indeks kapabilitasnya (atau kesesuaian) (Ci) (Table 28). Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm

EVALUASI LAHAN UNTUK IRIGASI Indeks Kapabilitas Class Definition Table 28 - Capability indexes for the different capability classes Indeks Kapabilitas Class Definition Symbol >80 I Excellent S1 60-80 II Suitable S2 45-60 III Slightly suitable S3 30-45 IV Almost unsuitable N1 <30 V Unsuitable N2 Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm

EVALUASI LAHAN UNTUK IRIGASI For slope class, texture, soil depth, calcium carbonate status, salinity and alkalinity, drainage, a weighted average was calculated for the upper 100cm of the soil profile then the considered factors were rated according to Table 29-Table 34. Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm

Slope class (%) Rating Non terraced Terraced 0-1 100 1-3 95 3-5 90 5-8 EVALUASI LAHAN UNTUK IRIGASI Table 29 - Rating of slopes (after Sys et al., 1991) Slope class (%) Rating Non terraced Terraced 0-1 100 1-3 95 3-5 90 5-8 80 8-16 60 85 16-30 50 70 >30 30 Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm

EVALUASI LAHAN UNTUK IRIGASI Table 30 - Rating of textural classes for irrigation (after Sys et al., 1991) KELAS TEKSTUR TANAH Rating <15% Gravel 15-40% 40-75% Clay – LIAT 65 55 Loam – LEMPUNG 90 80 70 Sand – PASIR 30 25 Silt – DEBU Sandy clay loam 95 85 75 Silty clay loam 100 Loamy sand – PASIR BERLEMPUNG 50 45 Sandy clay – LIAT BERPASIR 60 Silty clay – LIAT BERDEBU Clay loam – LEMPUNG LIAT Silt loam – LEMPUNG DEBU Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm

EVALUASI LAHAN UNTUK IRIGASI Table 31 - Rating of soil depth (after Sys et al., 1991) Table 32 - Rating of CaCO3 (Sys et al., 1991) Soil depth (cm) Rating CaCO3 (%) <20 30 >50 20-50 60 25-50 50-80 80 10-25 85 80-100 90 0.3-10 100 >100 Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm

Table 33 - Rating of salinity and alkalinity (after Sys et al., 1991) Na+ (%) Electric conductivity (mS) 0-4 4-8 8-16 16-30 >30 0-8 100 100* 95 90* 90 80* 85 70* 80 60* 8-15 75 50* 15-30 70 40* 65 30* (*) Clay, Silty clay, and Sandy clay Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm

Clay, silty clay, sandy clay, silty clay loam other textures Table 34 - Rating of drainage classes (after Sys et al., 1991, modified)Results and discussion Kelas Drainage Rating Clay, silty clay, sandy clay, silty clay loam other textures Excessively drained 100 Somewhat excessively drained 80 Well drained 85 95 Moderately drained 65 Somewhat poorly drained 55 70 Poorly drained 45 Very poorly drained 30 50 Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm

EVALUASI LAHAN UNTUK IRIGASI Figure 24 - Land suitability for irrigation Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm

EVALUASI LAHAN UNTUK IRIGASI Table 35 - Absolute and relative extent of different classes of suitability for irrigation Class Land unit Area km2 % S2 10, 12, 22, 23, 6, 31 42,65 6,59 S3 1, 8, 9, 11, 13, 14, 18, 34 229,73 35,51 N1 7, 4, 17, 19, 20, 21, 25, 26, 27, 28, 29, 32, 35, 37, 33 157,55 24,35 N2 2, 3, 5, 15, 16, 24, 30, 36 168,40 26,03 Not Relevant U, R, Q 12,04 1,86 Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm

EVALUASI LAHAN UNTUK IRIGASI Di lokasi penelitian tidak ada area yg sangat sesuai untuk irigasi. Moderately suitable land units are located in the alluvial valley (western part of the study area), and in the forest of Ben Slimane, where, of course, irrigation transformation is purely theoretical. The largest part of the agricultural areas were classified as marginally suitable, the most limiting factors being physical parameters such as slope, soil texture, and soil depth. This does not exclude the presence of small favoured areas where conditions can be much better. Faktor kimiawi seperti salinitas dan kandungan CaCO3 umumnya bukan faktor pembatas di lokasi penelitian. Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm

EVALUASI LAHAN UNTUK IRIGASI Pada lokasi dataran, banyak area yang tidak sesuai karena faktor pembatas sifat fisika tanah : Faktor pembatas tidak dapat diatasi dengan tingkat pengelolaan yanag ada sekarang, tetapi masih dimungkinkan untuk irigasi dengan menerapkan teknik-teknik mirigasi lainnya. In fact, some scattered spots of trees and vegetable orchards with drop irrigation are occasionally present, demonstrating the feasibility of these techniques. In the eastern escarpments, steep slopes and shallow soils lead to permanent unsuitable conditions for surface irrigation. Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm

EVALUASI LAHAN UNTUK IRIGASI . Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm