Pembuatan bahan pembenah tanah karboksimetil selulosa (CMC)-asam humat dan aplikasinya pada pertumbuhan tanaman cabai keriting (Capsicum annum L) telah dilakukan. CMC disintesis dari selulosa yang diisolasi dari ampas tebu dengan variasi konsentrasi NaOH 5; 7,5; 10; dan 15 % (b/v), kemudian selulosa direaksikan dengan sodium monokloro asetat (SCA) pada perbandingan berat 1,2,3,4,5,6 dan 7 g. Asam humat pada penelitian ini diekstraksi dari kompos daun Tithonia diversifolia dengan metode dari International Humic Substance Society (IHSS). Pembuatan bahan pembenah tanah CMC-asam humat dilakukan pada perbandingan berat CMC:asam humat 1:5, 1:1, dan 5:1 kemudian ditambah 0,2 gr MBA. Keasaman medium reaksi diatur pada pH 2, 5 dan 7. Karakterisasi dilakukan dengan spektroskopi FTIR dan SEM, serta penentuan kapasitas tukar kation (KTK) dan pengujian kemampuan menyerap air. Aplikasi dilakukan dengan cara pengukuran pertumbuhan daun, batang, bunga, buah, akar, dan kebutuhan air tanaman cabai keriting. Karakterisasi dengan FTIR menunjukkan adanya kecocokan antar spektrum selulosa teknis (Sigma) dengan selulosa yang didapat dari proses ekstraksi dalam NaOH 5%(b/v). Hasil pengujian kemampuan menyerap air pada CMC memberikan penyerapan air terbanyak pada CMC hasil reaksi 5 g selulosa dan 2 g SCA. Spektrum FTIR menampakkan bahwa pencucian asam humat dengan HCl/HF sebanyak 4 kali, telah membebaskan gugus –COOH dari pengotornya. Kemampuan asam humat dalam menyerap air tidak sebaik CMC, namun kemampuan asam humat dalam menahan air lebih baik. Indikasi telah terjadinya ikatan silang antara CMC, MBA dan asam humat dapat diketahui lewat spektrum FTIR dengan berkurangnya intensitas serapan di bilangan gelombang 3300-2900 cm -1 untuk regangan C=C yang menunjukkan digunakannya C=C untuk pengikatan silang. Kemampuan menyerap air terbanyak didapat pada produk bahan pembenah tanah CMC-asam humat (5:1). Pengaturan pH reaksi tidak berpengaruh secara signifikan terhadap kemampuan menyerap air produk bahan pembenah tanah CMC-asam humat. Pengujian kapasitas tukar kation (KTK) menunjukkan bahwa peningkatan pH reaksi dapat menurunkan KTK produk bahan pembenah tanah CMC-asam humat. Penggunaan bahan pembenah tanah CMC-asam humat (5:1) yang disintesis pada pH 2 dalam media tanam terbukti mampu menekan kebutuhan tanaman cabai keriting akan pupuk dan air.

Synthesis of CMC-humic acid ameliorant and its application for the growth of chili pepper (Capsicum annum L) has been done. The CMC was synthesized from the isolated cellulose from bagasse by varying the concentration of NaOH 5; 7.5; 10; and 15% (w / v), then reacted with sodium chloroacetate (SCA) in the weight ratio 1,2,3,4,5, 6 and 7 g. Humic acid was extracted from the composted leaves of Tithonia diversifolia according to the method of the International humic Substance Society (IHSS). Synthesis of CMC-humic acid ameliorant was performed at CMC: humic acid weight ratio: 1:5, 1:1, and 5:1 and into the reaction mixture 0.2 g MBA was then added. The medium acidity was adjusted to pH 2, 5, and 7. Characterization was carried out by FTIR spectroscopy and SEM, and it was also conducted the determination of cation exchange capacity (CEC) and the ability to absorb water. The application is done by measuring the growth of leaves, stems, flowers, fruits, roots, and crop water requirements of chili pepper plant. The characterization with FTIR confirmed the similarity between the spectra of commercially available cellulose (Sigma) and the cellulose obtained from the extraction process in NaOH 5% (w/v). The highest ability to absorb water was shown by CMC obtained from the reaction of 5 g cellulose and 2 g SCA. FTIR spectra showed that The purification through 4 times washing using the mixed solution of HCl and HF yielded humic acid with COOH functional group was free from impurities. The ability of humic acid to absorb water was not as good as CMC, while its ability to hold water was better. The indication of the presence of cross linking among CMC, MBA and humic acid was shown by FT-IR spectra, i.e. the presence of intensity reduction at wavenumber 3300-2900 cm -1 for C=C stretching. The ability to absorb water was highest for CMC-humic acid ameliorant (5:1). The acidity of reaction medium did not affect significantly the ability of the CMC-humic acid ameliorant in absorbing water. Cation exchange capacity (CEC) of CMC-humic acid ameliorant decreased with increasing the pH of reaction medium. The application of the CMC-humic acid (5:1) ameliorant which was synthesized at pH 2 for the growth of chilli pepper plant was able to suppress the need of water and fertilizer.

Kata Kunci : bahan pembenah tanah, CMC, asam humat, cabai keriting (Capsicum annum L).