Oil palm plantations are not environmentally friendly as they do not conserve soil or water.

Perkebunan kelapa sawit bukanlah tanaman yang ramah lingkungan karena tidak memiliki kemampuan konservasi tanah dan air.

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Oil palm plantations have three mechanisms to protect soil and water. The three mechanisms are canopy land cover, oil palm plantation area management and oil palm root systems.

First, the layered leaf structure of mature oil palm trees is able to cover land by nearly 100 percent. Besides functioning as the photosynthesis mechanism of oil palm trees, such a leaf structure also functions to protect land from the direct blow of rainfall. During rainfall, the blows of raindrops do not directly hit the soil because it has been protected by the layered leaf structure.

Second, land management in oil palm cultivation conserves soil and water. The technical standards of oil palm plantations, starting from planting to crop tending, uses soil and water conservation principles. Starting from zero/minimum tillage, crop cover during young crop tending (aged zero to 4 years), the making of terracing systems on sloping areas, the making of horseshoes, the placement of oil leaves (pruning) as contour terraces made of organic materials in spaces among trees, the return of empty bunches and liquid waste to the land and others are parts of the mechanism of soil and water conservation in oil palm plantations.

Third, the massive, wide and deep root system of mature oil palm trees can reach a radius of 4 meters around the base and a depth of up to 5 meters beneath the soil surface that forms micro and macro soil pores (Harahap, 1999, 2007), which can be called natural bio-pores. The natural bio-pores of the oil palm are mostly located near or around the base of the palm trees (Figure 1). The soil micro and macro pores become more numerous and larger as the palm trees mature.

Natural bio-pores increase the water holding capacity of oil palm plantation areas through the enhancement of rainfall infiltration into the soil, thereby reducing run-off by storing the water reserves in the soil. The larger the amount of oil palm natural bio-pores (namely near the base of the trunk), the higher the rate of infiltration of soil surface water to fill the bio-pores. The rate of infiltration will increase in line with the age of the plants (Figure 2) so that erosion and water run-off could be controlled.

The three oil and water conservation mechanisms are built-in systems in the oil palm trees and plantations, so that managing oil palm plantations for economic objectives will at the same time manage soil and water conservation in three ways. Moreover, the three soil and water conservation mechanisms of oil palm plantations are long term, equal to the economic age of the oil palm plantation (average 25 years).

Therefore, oil palm plantations have their own soil and water conservation systems. Oil palm plants even meet the requirements of being soil and water conservation plants. (Harahap,1999, 2007).

Kebun sawit memiliki tiga mekanisme yang secara sinergis berfungsi dalam melindungi tanah dan air. Ketiga mekanisme yang dimaksud adalah yakni mekanisme struktur dan naungan kanopi (canopy land cover), mekanisme tata kelola lahan kebun sawit dan mekanisme sistem perakaran kelapa sawit.

Pertama, mekanisme struktur pelepah daun pohon kelapa sawit yang berlapis-lapis mampu menaungi lahan (land cover) mendekati 100 persen saat dewasa. Struktur pelepah daun yang demikian selain berfungsi sebagai “dapurnya” (fotosintesis) kelapa sawit, juga berfungsi melindungi tanah dari pukulan langsung air hujan. Jika hujan datang, pukulan air hujan tidak langsung mengenai tanah namun terlindungi oleh struktur pelepah daun berlapis-lapis tersebut.

Kedua, mekanisme konservasi tanah dan air berikutnya adalah melalui tata kelola lahan dalam budidaya kelapa sawit. Standar kultur teknis kebun sawit mulai dari penanaman dan pemeliharaan tanaman menggunakan asas-asas konservasi tanah dan air. Mulai dari zero/minimum tillage, penanaman tanaman pelindung (cover crop) pada masa pemeliharaan tanaman belum menghasilkan (umur 0-4 tahun), pembuatan sistem teras pada lahan miring, pembuatan piringan/tapal kuda, penempatan pelepah tua (pruning) sebagai guludan bahan organik pada gawangan, pengembalian tandan kosong dan limbah cair ke lahan dan lainnya merupakan bagian dari mekanisme konservasi tanah dan air kebun sawit.

Ketiga, sistem perakaran serabut pohon kelapa sawit yang massif, luas dan dalam. Perakaran kelapa sawit dewasa dapat mencapai radius 4 meter sekeliling pangkal dan dengan kedalaman sampai 5 meter di bawah permukaan tanah yang membentuk pori-pori mikro dan makro tanah (Harahap, 1999, 2007) yang dapat disebut biopori alamiah. Biopori alamiah sawit tersebut terbanyak berada pada sekitar/dekat pangkal pohon sawit (Gambar 1). Pori-pori mikro dan makro tanah tersebut makin banyak dengan makin dewasa tanaman kelapa sawit.

Biopori alamiah tersebut meningkatkan kemampuan lahan kebun sawit dalam menyerap/menahan air (water holding capacity) melalui peningkatan penerusan (infiltrasi) air hujan ke dalam tanah sehingga mengurangi aliran air permukaan (runoff) dan menyimpan cadangan air di dalam tanah. Semakin banyak biopori alamiah sawit (yakni dekat pangkal batang) semakin tinggi laju infiltrasi air permukaan tanah mengisi biopori. Laju infiltrasi tersebut juga semakin meningkat dengan meningkatnya umur tanaman (Gambar 2) sehingga erosi permukaan tanah (water runoff) makin terkendali.

Ketiga mekanisme konservasi tanah dan air tersebut terikat dan menyatu (builtin) pada tanaman dan kebun sawit, sehingga mengelola kebun sawit untuk tujuan ekonomi juga sekaligus mengelola ketiga konservasi tanah dan air tersebut. Selain itu, ketiga mekanisme konservasi tanah dan air kebun sawit tersebut berjangka panjang sama dengan umur ekonomi kebun sawit (rata-rata 25 tahun).

Dengan demikian perkebunan kelapa sawit memiliki sistem konservasi tanah dan air. Bahkan tanaman kelapa sawit memenuhi syarat sebagai tanaman konservasi tanah dan air (Harahap, 1999, 2007).

Figure Bio-pore percentage of oil palm plant root system

Bio-pore percentage of oil palm plant root system

Source : Harahap, 1999, 2007; Harianja, 2009

Figure Rate of water infiltration into oil palm plantations rises in line with the age of oil palm trees

Rate of water infiltration into oil palm plantations rises in line with the age of oil palm trees

Source : Harahap, 1999, 2007; Harianja, 2009

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