Pengaruh Fluktuasi Muka Air Tanah Terhadap Pelepah Bawah Mengering (Low Frond Desiccation) Kelapa Sawit di Lahan Gambut Labuhan Batu, Sumatera Utara

Abstract

Masalah tanaman kelapa sawit berupa kering pelepah bagian bawah (low frond desiccation/LFD) sering terjadi pada lahan gambut. Kejadian ini umumnya dikaitkan dengan kondisi fluktuasi muka air tanah gambut yang berpengaruh terhadap kelembaban tanah gambut dan ketersediaan serta serapan hara oleh tanaman. Penelitian ini bertujuan untuk mengkaji permasalahan LFD, faktor-faktor penyebab dan upaya pencegahan atau pemulihannya. Kajian LFD telah dilakukan di perkebunan kelapa sawit di lahan gambut daerah Labuhan Batu, Sumatera Utara. Pengamatan meliputi fluktuasi muka air tanah, kondisi kelembaban tanah, sifat kimia tanah, serapan hara daun, pertumbuhan dan produksi tanaman dilakukan pada blok tanaman normal dan blok tanaman mengalami LFD. Hasil penelitian menunjukkan bahwa terjadinya penurunan muka air tanah gambut secara drastis pada saat bulan kering berdampak terhadap penurunan kelembaban gambut, bahkan hingga tanah gambut mengering. Kondisi pengeringan gambut menyebabkan ketersediaan hara dalam tanah dan serapan hara menurun secara nyata, sehingga memicu terjadinya LFD. Serapan hara tanaman yang mengalami LFD berat menurun dengan kisaran penurunan sebesar 25 – 41% untuk hara makro dan 22 – 53% untuk serapan hara mikro. Kondisi LFD berat secara nyata menurunkan pertumbuhan dan produksi tanaman kelapa sawit. Penurunan produksi dapat mencapai 27% per tahun dibandingkan dengan tanaman normal. Tanaman mengalami LFD dapat berangsur pulih dengan penerapan water management yang efektif, kontinyu dan terkontrol melalui pengelolaan muka air tanah pada kisaran kedalaman 40-60 cm pada blok tanaman.

Response of four oil palm varieties to low frond desiccation in the main nursery with water stress conditions on peat

“…Deeper roots at the surrounding moistened soil for continuing the grow of the plants. Thus, the root system reproduced itself to maximize soil water content [7,12].…”

“…Decreasing groundwater levels and water stress will affect nutrient transportation, assimilation processes and physiological cycles [11]. The incidence of LFD in oil palm plants reduces production up to 27% during one year, and declining number of bunches by almost 30% in a year [12]. The decreasing number of bunches is due to the water stress, which affects flower abortion, bunch failure, increased male flower formation and decreased female flower formation [13].…”

Does the exposure of water shortage in peat soil affect the nutrient uptake of seedlings between different oil palm varieties?

“…Some varieties were known to portray different drought tolerance in terms of morphological, physiological, and biochemical processes [7,[10][11][12]. For example, low frond desiccation (LFD) is known as one of morphological adaptation strategies in abiotic stress like drought, which is found either in oil palm cultivation on mineral soil [4] or peat soil [13]. Moreover, the presence of proline, nitrate reductase activity (NRA), chlorophyll content, and abscisic acid were known as physiological response for water shortage [7,9,14,15].…”

“…More than 1.7 ha of Indonesian oil palm plantations were cultivated on peat soil [20]. Peat soil is composed of organic matter and has high porosity, which tends to be more sensitive to changing water and soil moisture [13,21]. Presence of hydrophobicity traits or irreversible drying and higher soil acidity affects concentration of COOH and OH groups in soil, leading to decreasing the availability of soil nutrients [21,22].…”

“…Presence of hydrophobicity traits or irreversible drying and higher soil acidity affects concentration of COOH and OH groups in soil, leading to decreasing the availability of soil nutrients [21,22]. Hashim et al [23] and Winarna et al [13] found that retention ability will decline on dried peat soil condition and commence on nutrient leaching, decreasing nutrient availability and nutrient uptake. Deflation of soil nutrient uptake was not only ensued in macronutrients like Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca), and Magnesium (Mg), but also found in micronutrients like Cuprum (Cu), Zinc (Zn), Boron (B), and Iron (Fe).…”