Penerapan Metode Irigasi Hemat Air Untuk Memberdayakan Sumur Air Tanah Dalam Pada Lahan Tadah Hujan Desa Ranakolo Kabupaten Ende

MARSELUS ECLESIANUS META, Ir. Joko Sujono, M.Eng, Ph.D.,

2012 | Tesis | S2 Mag.Pengl.Sumberdaya Air

Pembangunan jaringan irigasi air bawah tanah (JIAT) pada lahan tadah hujan Desa Ranakolo merupakan upaya pemerintah dalam meningkatkan pendapatan petani. Namun demikian petani tidak pernah memanfaatkan karena kuatir merugi akibat penambahan biaya produksi. Kekuatiran ini didasari perlakuan pemberian air metode tradisional (TRI) dengan penggenangan menerus, serta hasil produksi sawah irigasi regional yang hanya 4 ton per ha. Guna mengatasi persoalan tersebut, maka penerapan metode irigasi hemat air menjadi solusi terbaik. Metode yang diterapkan adalah Alternate wetting and drying (AWD) dan Semi-dry cultivation (SDC) yang dikombinasikan dengan mulsa, dengan cara tanam benih langsung (Tabela) dan bibit umur 9 hari. Parameter yang diteliti adalah produktifitas padi, penghematan dan produktifitas air, koefisien tanaman (Kc) berdasarkan rasio evapotranspirasi nyata pengukuran (ETc) dan Evapotranspirasi acuan (ETo), dan lama hari perkolasi. Berdasarkan Kc dan lama hari perkolasi dilakukan analisis kebutuhan air irigasi (KAI) pada setiap jadwal tanam. Penentuan pola tanam ideal menggunakan analytic hierarchy process (AHP), dengan pertimbangan efisiensi dan efektifitas pemanfaatan air berbagai aletrnatif jadwal tanam. Dari rasio ketersediaan air dan KAI pada jadwal tanam optimum ditentukan luas lahan yang dapat dibudidayakan. Perbedaan kebutuhan air irigasi metode hemat air dengan TRI, berdampak pada kesesuaian jaringan dan luas lahan, sehingga perlu disimulasi kinerja jaringan dengan bantuan software WaterNet Berdasarkan produktifitas padi, KAI, dan input produksi; dilakukan analisis ekonomi, guna memberikan gambaran net benefit yang diperoleh petani. Kesalahan perlakuan pintu air metode SDC menyebabkan kesamanan kondisi air SDC dengan AWD, sehingga hasil penelitian disimpulkan sebagai hasil AWD. Adanya larangan adat menyebabkan cara tabela tidak dapat diterapkan. Hasil penelitian menunjukan metode AWD dapat meningkatkan produktifitas padi rerata sebesar 147%, penghematan air rerata sebesar 31,6%, dan produktifitas air rerata sebesar 298%. Sistem pemberian air AWD berdampak pada penurunan nilai Kc. Kc AWD 0,5 bulan selama masa tumbuh sebesar 0,62; 0,75; 0,85; 0,93; 1,09; 1,19; 0,89. Pola tata tanam ideal adalah padi-padi dengan Musim Tanam (MT) 1 Desember minggu ke 1 dan ke 3, MT2 April minggu ke 3 dan Mei minggu ke 1. Luas lahan terairi MT1 Desember 1 dan 3 adalah 6,57 dan 6,61 ha dn MT2 April 3 dan Mei 1 adalah 6,7 dan 7,8 ha. Hasil simulasi WaterNet, jaringan alternatif dengan pompa Q 10 l/dt dan H 40 m dapat melayani kebutuhan tiap node dengan efisiensi pompa optimum 69,9%. Penerapan metode AWD dapat menghasilkan Net benefit optimum rerata Rp.14.477.160 /ha/MT.

The development of underground water irrigation networks (JIAT) in the rain-fed farm of Ranakolo village is a government's effort to increase farmers' income. However, farmers never use it to consider of losing money due to additional production costs. They concerned on traditional methods of water treatment (TRI) with continuous flooding, and the regional irrigated rice production results which only 4 tons per ha. To overcome the issue , then an application of water-saving irrigation methods seem to be the best solution. The applied method is Alternate wetting and drying (AWD) and Semi-dry cultivation (SDC) combinated with mulch by direct-seeded (Tabela) and 9 day old seedlings. The studied parameters were productivity of rice, water saving and productivity, crop coefficients (Kc) based on the real measurements of evapotranspiration ratio (ETC) and reference evapotranspiration (ETo), and percolation duration. Based on Kc and percolation duration, it then conducted an analysis of irrigation water demand (KAI) on each planting schedule. Determination of ideal cropping pattern was used the analytic hierarchy process (AHP), considering the various alternative of planting schedule. From the determined ratio of water availability and KAI on optimum planting schedule, it then specified the area of land that can be cultivated. Difference of water needs with water-saving irrigation methods TRI has an impact on the suitability and extensive network of land, therefore, it needs to be simulated the network performance by using the WaterNet software. Based on rice productivity, KAI, and production inputs, it then conducted an economic analysis to provide a figure of net benefit obtained gained by the farmers. Methods error treatment of water sluice by using the SDC method had caused similarity on SDC water conditions with AWD, therefore, it was concluded as an AWD result . Considering the customs restriction, it led the method of tabela/seeded rice can not be applied. The results showed such AWD method could improve, in average, the rice productivity of 147%, water savings of 31.6%, and average water productivity of 298% compared to TRI method. AWD watering systems had impacted on the Kc value . Kc AWD 0.5 months during the period had grew by 0.62; 0.75; 0.85; 0.93; 1.09; 1.19; 0.89. Ideal cropping pattern was the paddy-rice with the planting season (MT1) on December of 1st and 3rd week, MT2 on April of 1st and 3rd, and May of 1st week. With areas of the irrigated land for MT1 on december 1st and 3rd week were 6.57 and 6.61 ha and MT2 on April of 3rd and May 1st were 6.7 and 7.8 ha, respectively. For WaterNet simulation results, an alternative network with Q pump 10 l / dt and H 40 m could serve the needs of each node by optimum pump efficiency 69.9%. The application of AWD method had produced an optimum net benefits with mean Rp.14.477.160 / ha / MT.

Kata Kunci : JIAT, Irigasi Hemat Air, Simulasi Jaringan, Net Benefit.