C-organik tanah pada perkebunan kelapa sawit dapat dijadikan salah satu parameter keberlanjutan ekosistem dan kesuburan tanah. Perubahan sifat kimia tanah yang dinamis tidak lepas dari proses biogeokimia dari mineralisasi dan pelapukan bahan organik menjadi C-organik tanah. Penelitian ini bertujuan untuk mengkaji status C-organik tanah serta kaitannya dengan sifat kimia tanah lainnya dalam kurun waktu 5 tahun dari tahun 2009 sampai tahun 2014 di perkebunan kelapa sawit Sumatera Utara, dengan jenis tanah Inceptisols dan Ultisols. Metode pengambilan sampel menggunakan purposive random sampling. Data dianalisis menggunakan uji komparatif T-paired antara kebun yang diamati pada tahun 2009 dan 2014 untuk melihat perubahan nilai C-organik, dan parameter sifat kimia tanah. Uji korelasi dilakukan untuk melihat keterkaitan antara C-organik dengan parameter sifat kimia tanah lainnya, yaitu kadar N, kejenuhan Al, pH, dan kapasitas tukar kation (KTK). Hasil penelitian menunjukkan bahwa dari 25 kebun pengamatan, nilai C-organik dari 3 kebun meningkat dan 6 kebun menurun secara signifikan, sedangkan 16 lainnya tidak berbeda nyata. Dalam periode 5 tahun, kandungan Corganik tanah cenderung fluktuatif namun tetap berada pada kelas yang sama dengan kisaran rendah hingga sedang (<1,75%). Peningkatan nilai C-organik hanya berkorelasi linier dan nyata dengan N pada tanah Inceptisols (r = 0,392). Sedangkan, pada tanah Ultisols, peningkatan Corganik tanah secara nyata diikuti dengan penurunan nilai pH (r =-0,141).
Waktu panen tandan kelapa sawit umumnya ditentukan berdasarkan warna tandan dan jumlah brondolan yang jatuh di piringan. Pembrondolan buah secara ilmiah disebut sebagai proses absisi yang dipengaruhi kondisi endogenous tanaman dan faktor lingkungan. Pendapat umum di lapangan menyatakan bahwa tandan matang lebih cepat dan brondolan lebih banyak ketika curah hujan tinggi. Penelitian ini dilakukan untuk menguji pendapat tersebut berdasarkan uji korelasi Pearson antara curah hujan harian pada lag-0 hingga lag-20 hari dengan jumlah brondolan yang jatuh per hari. Penelitian dilakukan pada tanaman umur lima tahun di Kebun Percobaan Sei Aek Pancur, Pusat Penelitian Kelapa Sawit (PPKS) pada lima rotasi panen (interval panen 10 hari). Hasil penelitian menunjukkan bahwa nilai dan sifat korelasi antara curah hujan dengan jumlah brondolan sangat bervariasi. Namun demikian, terdapat kecenderungan bahwa curah hujan optimal yang terjadi pada awal (lag-17 s.d. 20), pertengahan (lag-9 s.d. 12), dan akhir fase pematangan buah (1-3 hari menjelang tandan siap panen) dapat mempercepat pematangan tandan dan meningkatkan jumlah buah yang membrondol. Oleh karena itu, praktisi perkebunan sebaiknya mempersiapkan sarana dan prasarana panen yang memadai khususnya pada musim hujan ketika cadangan buah cukup tinggi dan peluang banyak tandan matang secara bersamaan lebih tinggi.
Maize (Zea mays) is one of the major crops and widely grown in Indonesia. On average, current maize yields are still below its potential. Thus, it needs to increase by good agricultural practices such as applying biofertilizer, which consists of beneficial bacteria. This research was aimed to find out the impact of the bacterial consortium of nitrogen-fixing bacteria (BPN) and phosphate solubilizing bacteria (BPF) on the maize growth. The study was conducted in the greenhouse and arranged in a completely randomized design (CRD) with treatments, i.e.: (1) negative control (no inorganic fertilizer and BPN-BPF); (2) positive control (100% inorganic fertilizer); (3) only BPN-BPF applied (no inorganic fertilizer); (4) 75% inorganic fertilizer + BPN-BPF; and (5) 50% inorganic fertilizer + BPN-BPF. The results revealed that the consortium of nitrogen-fixing bacteria and phosphate solubilizing bacteria significantly improved certain soil chemical properties, such as C-organic, cation exchange capacity (CEC), and the availability of nitrogen and phosphorus in the soil. Besides, the consortium of BPN and BPF also increased the maize growth and total biomass up to 19%. Further, a consortium of BPN and BPF increased the fertilizer efficiency by reducing the dosage of inorganic fertilizer up to 50%.
The present study aimed to test the efficiency of Hendersonia GanoEF biofertilizer against Ganoderma disease in the seedlings of oil palm (OP) Elaeis guineensis, and was carried out from February 2020 – January 2021 in Pulo Mandi Garden Nursery, at Medan, Indonesia. Experimental set up followed a completely randomized design with four treatments. Observation results showed that the percentage of root colonization by Hendersonia sp. in OP roots reached an average of 70.6% in the treatment with Ganoderma inoculation, and an average of 69.6% in the treatment without Ganoderma inoculation. The GanoEF treatment provided higher growth of seedlings and faster growth of bowl diameter when the seedlings were 9 months old. Three instances of GanoEF application had high potential to inhibit the development of Ganoderma on OP seedlings. Endophytic fungi Hendersonia sp. was capable of symbiosis with OP roots with a colonization rate reaching 70.6%. Disease incidence or percentage of plants infected with Ganoderma in GanoEF treatment reached 20.4% which was significantly (P<0.05) lower than under the control treatment (44.2%). Meanwhile, the level of severity of Ganoderma disease in seedlings with GanoEF treatment reached 5.23% which was significantly (P<0.05) lower than the control treatment (11.1%). The efficacy of Hendersonia GanoEF as a biocontrol method for the OP pathogen G. boninense to control the basal stem rot of E. guineensis seedlings was well proven in this field study.
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