Peningkatan Produktivitas Tanaman Ubi Kayu Melalui Peningkatan Status C-organik Tanah dan Dosis Pupuk NPK di Tanah Ultisol

Abstract

Tanaman ubi kayu merupakan tanaman yang dapat dimanfaatkan sebagai bahan pangan dan bioenergi. Tingginya permintaan ubi kayu tidak diimbangi dengan produksi umbi dari dalam negeri. Peningkatan produksi dapat dilakukan dengan peningkatan luas tanam (ekstensifikasi) dan produktivitas (intensifikasi). Peningkatan luas tanam dapat diterapkan di tanah ultisol dan peningkatan produktivitas dapat dilakukan melalui pemupukan. Tanah ultisol memiliki Carbon organik (C-org) tanah dan hara yang rendah, sehingga pemupukan organik untuk meningkatkan C-org dan pemupukan NPK untuk meningkatkan hara makro. Tujuan penelitian ini untuk mengetahui pengaruh C-org tanah dan pupuk NPK serta interaksinya terhadap pertumbuhan dan hasil tanaman ubi kayu di tanah ultisol. Percobaan dilakukan pada bulan September 2022 hingga Mei 2023 di Kebun Penelitian Jonggol AGH IPB, Kecamatan Jonggol, Kabupaten Bogor. Penelitian menggunakan rancangan petak terpisah. Perlakuan petak utama yaitu C-organik tanah terdiri atas 1,93%, 2%, 3%, dan 4%, sedangkan perlakuan anak petak yaitu dosis pupuk NPK terdiri atas 150, 300, 450, dan 600 kg ha-1. Bibit yang digunakan yaitu Varietas Mangu. Stek ditanam dengan jarak tanam 1 m x 0,8 m pada petak 5 m x 4 m setiap satuan percobaan. Peubah yang diamati meliputi pertumbuhan tanaman (tinggi tanaman, diameter batang, jumlah daun, bobot daun dan batang), hasil umbi (bobot, jumlah, panjang, diameter dan kadar pati), kadar hara NPK daun dan umbi, efisiensi agronomi, dan perubahan kimia tanah. Hasil penelitian menunjukkan pemberian pupuk kandang sapi meningkatkan kesuburan tanah (C-org, N-total, P tersedia, K-dd, dan kapasitas tukar kation tanah) pada siklus akhir tanaman. Perlakuan C-org 3% dan NPK 300 kg memiliki pertumbuhan terbaik meliputi (tinggi tanaman, diameter batang, jumlah daun, bobot daun dan batang). Pertumbuhan didukung dengan kehijauan, kadar hara N dan K daun yang lebih tinggi pada kedua perlakuan tersebut. Kadar P daun tidak dipengaruhi perlakuan C-org dan NPK. Produktivitas umbi ubi kayu meningkat sebesar 35,47% dari 35,39 ton ha-1 pada C-org 1,93% menjadi 47,80 ton ha-1 pada C-org 3%, dan 21,53% dari 37,45 ton ha-1 pada perlakuan pupuk NPK 150 kg menjadi 45,51 ton ha-1 pada perlakuan pupuk NPK 300 kg. Peningkatan jumlah umbi total dan komersial terjadi pada C-org 3% dan 4%, namun ukuran panjang umbi menjadi lebih pendek. Efisiensi agronomi N-P-K tertinggi terdapat pada C-org 2%. Neraca hara mengalami surplus pada C-org 3% untuk produksi umbi 40 dan 70 ton ha-1. Kadar hara N umbi tertinggi pada C-org 2% sebesar 0,643% dan NPK 600 kg sebesar 0,553. Kadar P umbi tertinggi pada C-org 4% sebesar 0,133% dan NPK 300 kg sebesar 0,118%. Kadar K tertinggi pada C-org 4% sebesar 1,183% dan NPK 600 kg sebesar 0,918%. Kadar pati umbi tertinggi terdapat pada perlakuan C-org 4% sebesar 17,279% dan NPK 300 kg sebesar 16,263%. Kadar hara N berkorelasi negatif dan P berkorelasi positif terhadap bobot umbi.

Cassava is a crop that utilized as food and bioenergy. The high demand for cassava is unbalanced by tuber production from domestic. Increasing production is by increasing the planting area (extensification) and productivity (intensification). An increase in planting area can be conducted to ultisol and an increase in productivity can be accomplished through fertilization. Ultisol soil has low soil organic carbon and nutrients, so organic fertilizer is to increase C-org, and NPK fertilizer is to increase macronutrients. This research aimed to determine the effect of soil C-org and NPK fertilizer and their interaction on the growth and yield of cassava in ultisol soil. The experiment was from September 2022 to May 2023 at the Jonggol AGH IPB Research Station, Jonggol District, Bogor Regency. The research used a split-plot design. The main plot treatment, namely soil organic C, consisted of 1.93%, 2%, 3%, and 4%, while the subplot treatment, namely NPK fertilizer doses, consisted of 150, 300, 450, and 600 kg ha-1. The cuttings were the Mangu variety. Cuttings were grown with planting distance of 1 m x 0.8 m in plots of 5 m x 4 m per experimental unit. Variables observed included plant growth (plant height, stem diameter, leaf number, leaf, and stem weight), tuber yield (weight, number, length, diameter, and starch content), NPK nutrient contents in leaves and tubers, agronomic efficiency, and soil chemical change. The results showed that the application of cow manure increased soil fertility (C-org, N-Total, P-available, interchangeable K, and soil cation exchange capacity) at the end of the crop cycle. The C-org 3% and 300 kg NPK treatment had the best growth involving (plant height, stem diameter, number of leaves, leaf and stem weight). Those growths were supported by higher greenness and N and K nutrient contents of leaves in both treatments. Leaf P content was unaffected by C-org and NPK treatments. Cassava tuber productivity increased by 35,47% from 35,39 tons ha-1 at C-org 1.93% to 47,80 tons ha-1 at C-org 3%, and 21,53% from 37,45 tons ha-1 at 150 kg NPK fertilizer to 45,51 tons ha-1 at 300 kg NPK fertilizer. The increase in the number of total and commercial tubers occurred at C-org 3% and 4%, but the tuber length became shorter. The highest N-P-K agronomic efficiency is found C-org 2%. The highest N nutrient content of the tuber was C-org 2% of 0,643% and 600 kg NPK of 0,553. The highest P content of the tuber was 4% C-org of 0,133% and 300 kg NPK of 0,118%. The highest K content of the tuber was C-org 4% of 1,183% and 600 kg NPK of 0,918%. The highest starch content of the tuber was 4% C-org of 17,279% and 300 kg NPK of 16,263%. The nutrient content of N has a negative correlation and P has a positive correlation with the starch content of the tuber.