REKAYASA TANAH DASAR KOLAM INCEPTISOL MELALUI PENAMBAHAN ULTISOL DAN VERTISOL UNTUK MENINGKATKAN PERTUMBUHAN ALGA DASAR PAKAN LARVA NILA MERAH (Oreochromis sp.)

Saberina Hasibuan, S.Pi.,MT., Prof. dr. ir. Bambang Djadmo Kertonegoro, M.sc.

2011 | Disertasi | S3 Ilmu Tanah

Untuk mengatasi kesuburan tanah kolam Inceptisol yang rendah maka secara fisik dilakukan perbaikan tekstur tanah dari geluh pasiran menuju lempungan. Perbaikan dilakukan dengan cara pemarelan menggunakan bahan berkadar lempung tinggi, dalam hal ini lempung yang berasal dari Ultisol dan Vertisol. Penelitian dilaksanakan Agustus 2006 sampai September 2008 di persawahan Dusun Sewon Argomulyo, Cangkringan Sleman-Yogyakarta. Penelitian ini bertujuan untuk (1) mengkaji pengaruh bahan pemarel Ultisol dan Vertisol terhadap produktifitas tanah kolam Inceptisol; (2) mengkaji pengaruh pupuk basal terhadap peningkatan kesuburan TDK serta dampaknya terhadap pertumbuhan alga dasar, plankton dan larva ikan nila merah; (3) mendapatkan frekuensi pemberian pupuk kandang burung puyuh yang optimal terhadap keberlangsungan pertumbuhan alga dasar dan plankton sebagai pakan alami larva ikan nila merah; (4) mengkaji pengaruh pemampatan lapisan P (Parent layer/tanah asli Inceptisol) dan penambahan pupuk kandang burung puyuh terhadap ketersediaan hara pada Masa Tanam 1 dan efek residualnya terhadap produktifitas kolam pada Masa Tanam 2; (5) meningkatkan produksi benih ikan nila merah. Hasil penelitian menunjukkan pemarelan tanah Inceptisol-Ultisol dan Inceptisol-Vertisol dengan kandungan lempung antara 41-51% memberikan pengaruh nyata (P<0,05) terhadap peningkatan sifat kimia tanah dasar kolam. Sifat kimia atas dasar parameter: DHL, pH, bahan organik, KPK, Kejenuhan Basa, kadar Fe tersedia, K tersedia, nisbah C/N dan kadar Ca2+, Mg2+, K+ dan Na+ tersedia yang selanjutnya mempengaruhi kualitas air kolam. Kualitas air atas dasar parameter: DHL, pH, kadar oksigen terlarut, bahan organik di air, kadar CO2 terlarut, P total, SiO2, kesadahan dan alkalinitas total, kadar Fe larut air, amonia (NH3), kebutuhan O2 biologi (BOD) dan O2 kimiawi (COD), organik karbon total, dan kelarutan ion-ion di air, kadar nitrat, ammonium, dan fosfat terlarut reaktif. Kadar lempung > 40% memberikan kontribusi besar terhadap peningkatan kualitas TDK dan air kolam. Kesuburan tanah Inceptisol dirajai oleh mineral plagioklas (±92%) dan haloisit (±8%). Kadar mineral haloisit pada tanah campuran (I-U) berkisar antara 28- 50% dan kadar mineral montmorilonit pada tanah campuran (I-G) berkisar antara 28- 57%. Tingginya kadar mineral montmorilonit pada campuran I-G lebih disebabkan oleh kadar lempung pada bahan pemarel Vertisol yang tinggi. Dengan demikian TDK yang mengandung mineral montmorilonit dapat memperbaiki kesuburan kolam dan masih bertahan hingga MT-2. Produksi klorofil, kemelimpahan alga dasar dan plankton juga meningkat, selanjutnya akan memacu pertumbuhan larva nila merah. Biomassa total, rerata panjang total dan bobot pada dosis terbaik (30%:70%) untuk I-U dan I-G tanpa basal berturut-turut 68g dan 99g; 3,9 cm dan 4,6 cm; 1,23g dan 1,80g. Selama pemeliharaan larva nila merah kelulushidupan berkisar antara 69–76% dan faktor kondisi berkisar antara 1,61–1,87, pertumbuhan ikan berturut-turut mengikut pola b xxx = 3 berarti isometrik dan pola b>3 berarti allometrik. Penggunaan pupuk basal (2 ton/ha) pada kolam 30%I:70%U dan 50%I:50%G diperoleh biomassa total, rerata panjang total dan bobot berturut-turut 115g dan 99g ; 5,0 cm dan 4,6 cm ; 2,25g dan 1,96g. Selama pemeliharaan larva nila merah kelulushidupan berkisar antara 65– 75% dan faktor kondisi berkisar antara 1,63 – 3,06, pertumbuhan ikan berturut-turut mengikut pola b = 3 berarti isometrik dan pola b<3 berarti allometrik. Pemberian pupuk kotoran burung puyuh (1 ton/ha) secara bertahap terbaik pada kolam (30%I:70%U)F3 dan (50%I:50%G)F3 diperoleh biomassa total, rerata panjang total dan bobot berturut-turut 188g dan 217g; 5,2 cm dan 5,6 cm; 2,69g dan 3,43g. Selama pemeliharaan larva nila merah kelulushidupan berkisar antara 83-90% dan faktor kondisi berkisar antara 1,80–1,87, pertumbuhan ikan berturut-turut mengikut pola b = 3 berarti isometrik dan pola b>3 berarti allometrik. Produksi benih nila merah pada MT-1 tertinggi pada padat tebar 100 ekor/m2 (232,02g), sedangkan rerata panjang dan bobot tertinggi pada padat tebar 50 ekor/m2 adalah 4,6 cm dan 1,76g. Perlakuan pemampatan lapisan P, campuran (50%I:50%G), dan pemberian pupuk organik 5 ton/ha memberikan hasil terbaik untuk biomassa total berturut-turut 198g, 192g dan 196g; rerata panjang dari tiap perlakuan adalah 4,4 cm; rerata bobot berturut-turut 1,64g, 1,61g dan 1,65g, dan selama 42 hari pemeliharaan larva nila merah kelulushidupan berkisar antara 97–98%, faktor kondisi berkisar antara 1,75–1,86 serta pertumbuhan ikan mengikuti pola b = 3 berarti isometrik. Produksi benih nila merah pada MT-2 tertinggi pada padat tebar 100 ekor/m2 (227,01g), sedangkan rerata panjang dan bobot tertinggi pada padat tebar 50 ekor/m2 adalah 4,4 cm dan 1,59g. Perlakuan pemampatan lapisan P, dan residual pupuk organik MT-1 (5 ton/ha) memberikan hasil terbaik untuk biomassa total yaitu 186g dan 185g; rerata panjang tiap perlakuan adalah 4,3 cm; rerata bobot yaitu 1,49g dan 1,48g, sedangkan biomassa total (181g dan 173g), rerata panjang (4.2 cm) dan bobot (1.44g) pada campuran (50%I:50%G) tidak berbeda nyata dengan (30%I:70%U). Selama 42 hari pemeliharaan larva nila merah kelulushidupan berkisar antara 97–98%, faktor kondisi berkisar antara 1,78–2,07 serta pertumbuhan ikan mengikuti pola b = 3 berarti isometrik. Berdasarkan analisa lambung benih ikan nila merah selama penelitian ditemukan kesamaan antara pakan alami yang tersedia di kolam dengan yang dimakan yaitu larva menyukai Cyanophyta, Bacillariophyta, Chlorophyta, Plathyhelminthes dan sedimen.

This dissertation aims to overcome the low physical fertility of the pond bottom soil, which is made up of the sandy Inceptisols. Improving the soil physical quality can be achieved by modifying the soil texture from sandy loam to clay. This is achieved by physically mixing the Inceptisols with soils that have higher clay content, such as Ultisols and Vertisols. The mixing is proposedly meant marling. This research was carried out from August 2006 to September 2008 in a rice field at Sewon Village, Argomulyo, Cangkringan, Sleman, Yogyakarta. The objectives of this research are (1) To study the effect of mixing Ultisols and Vertisols on the productivity of the Inceptisols pond bottom soil, (2) To study the effect of basal fertilizer application on the pond bottom soil fertility and growth of benthic algae, plankton, and red tilapia larvae, (3) To find an optimal fertilization frequency by quail manure droppings on the growth of benthic algae and plankton as natural feed to red tilapia larvae, (4) To study the effect of Inceptisols Parent layer (P) compaction and the addition of quail manure fertilizer on nutrient availability during the first planting period (PP-1) and the residual effect on pond productivity in the second planting period (PP-2), and (5) To increase the red tilapia seed production. The results showed that the Inceptisols-Ultisols and Inceptisols-Vertisols mixture with clay content between 41-51% gave significant effect (P<0.05) on the chemical characteristics of the pond bottom soil, such as EC, pH, organic matter content, CEC, base saturation, Fe and K availability, C/N ratio, Ca2+, Mg2+ , K+ and Na+. It also provided a favourable pond water quality, such as water temperature, EC, and pH, O2 dissolved content, organic matter content, CO2 dissolved content, P, SiO2, total of alkalinity and hardness, content of dissolved and available Fe, ammonia (NH3), BOD, COD, total of water organic carbon, concentration of Ca, Mg, HCO3 - (bicarbonat) and CO3 2- (carbonate), concentration of nitrate and ammonium, and concentration of soluble reactive phosphate in pond water. Clay content > 40% resulted in a high contribution to the increase of pond bottom soil and water quality. The Inceptisols was dominated by plagioclase minerals (±92%) and halloysite (±8%). Halloysite content in the soil mixture (I-U) ranged from 28 to 50% and the montmorillonite content in the soil mixture I-G ranged from 28 to 57%. The high content of montmorillonite in the I-G mixture was due to the mixture with Vertisols. Therefore, pond bottom containing montmorillonite can improve the pond fertility and can be maintained until PP-2. Chlorophyll production, benthic algae and plankton abundances were also increased, which then stimulated the growth of red tilapia larvae. The total biomass, mean of length and weight at the best dose (30%:70%) for I-U and I-G without basal fertilizer were 68g and 99g; 3.9 cm and 4.6 cm; 1.23g and 1.80g, respectively. The survival rate started from 69 to 76%, and conditional factor was from 1.61 to 1.87. The fish growth followed isometric patterns (b=3) and b>3. Addition of basal fertilizer (2 ton/ha) in ponds with 30%I : 70%U and 50%I : 50%G resulted on total biomass 115g and 99g; mean length were 5.0 cm and 4.6 cm; and mean weight were xxxii 2.25g and 1.96g. The survival rate started from 65 to 75%, conditional factor was from 1.63 to 3.06. The fish growth followed isometric patterns (b=3) and b<3. Quail manure (1 ton/ha) droppings frequency in pond (30%I:70%U)F3 and (50%I:50%G)F3 gave the best results. The total biomass, mean of length and weight of each treatment were 188g and 217g; 5.2 cm and 5.6 cm; 2.69g and 3.43g, respectively. The survival rate started from 83 to 90%, and conditional factor was from 1.80 to 1.87. The fish growth followed isometric patterns (b=3) and b<3. The highest red tilapia seed production in PP-1 resulted from a density of 100 seed/m2 (232.02g), while the highest means of length (4.6 cm) and weight (1.76g) was found from treatment at density of 50 seed/m2. On the other hand, P layer compaction treatment, mixture of (50%I : 50%G) and treatment of 5 ton/ha organic fertilizer resulted in a high seed production. The total biomass was 198g, 192g and 196g, respectively. The average length of the fish for each treatment was 4.4 cm, and the averages of the weight were 1.64g, 1.61g and 1.65g, respectively. The survival rate started from 97 to 98%, and conditional factors was from 1.75 to 1.86, and the fish growth followed an isometric pattern b = 3. The highest red tilapia seeds production in PP-2 was found from density of 100 fries/m2 (227.01g), while a high mean of length (4.4 cm) and weight (1.59g) was found from the treatment with at density of 50 seed/m2. On the other hand, P layer compaction treatment, and the residual effect of organic fertilizer (5 ton/ha) in PP-1 resulted in high seed production. The total biomass was 186g and 185g, respectively. The average fish length for each treatment was 4.3 cm, and the average weight were 1.49g and 1.48g, respectively. While total biomass (181g and 173g), average length (4.2 cm) and weight (1.44g) at soil mixture of 50%I:50%G and 30%I:70%U were not significantly different. During rearing, the survival rate of the larvae started from 97 to 98%, and conditional factors was from 1.78 to 2.07, and the fish growth followed isometric pattern b = 3. Based on the fish stomach analysis, it was found that there was a similarity between natural feed in the pond and the feed eaten by fish. The feed were Cyanophyta, Bacillariophyta, Chlorophyta, Plathyhelminthes, and sediment.

Kata Kunci : Ultisol, Vertisol, kesuburan kolam, montmorillonit, sifat fisika dan kimia, kualitas tanah, pemarelan