Pengaruh Aplikasi Kompos dan Asam Humat Terhadap Produktivitas Tanah Pasir dan Pertumbuhan Sawi Hijau (Brassica juncea L.)

Abstract

Tanah pasir adalah tanah tidak subur dengan retensi air dan hara rendah. Tujuan penelitian untuk mengkaji pengaruh aplikasi kompos dan asam humat terhadap produktivitas tanah pasir serta pertumbuhan dan produktivitas sawi hijau. Penelitian dilakukan secara eksperimental di greenhouse dengan menumbuhkan semai sawi hijau pada tanah pasir yang diberi perlakuan aplikasi pembenah tanah. Terdapat tiga perlakuan yaitu kontrol (P0), aplikasi kompos (P1), dan aplikasi asam humat (P2). Parameter produktivitas pasir yang diukur meliputi: deskripsi konsistensi struktur tanah dan kandungan air kapasitas lapang. Dilakukan pengukuran terhadap persentase peningkatan jumlah akar, panjang akar lateral, bobot kering akar, jumlah daun, luas daun, bobot kering daun dan kandungan pigmen fotosintesis (klorofil a, klorofil b dan karotenoid) untuk mengetahui respon pertumbuhan dan produktivitas tanaman. Hasil penelitian menunjukkan terdapat perubahan struktur tanah pasir dari struktur lepas menjadi gembur dan lekat setelah aplikasi kompos, dan teguh setelah aplikasi asam humat. Aplikasi kompos dan asam humat menyebabkan peningkatan persentase kadar air kapasitas lapang. Persentase kadar air tanah P1 (52,6%) lebih tinggi dibanding P2 (10,7%) dan P0 (6,4%). Persentase pertumbuhan dan produktivitas tanaman sawi tertinggi terdapat pada P1 diikuti P2 dan P0 yaitu: 3,2%, 2,3%, 1,8% (panjang akar lateral), 59,4%, 47,2%, 33% (bobot kering akar), 21%, 19,6%, 14,5% (luas daun), 28,4%, 24,9%, 24% (bobot kering daun). Penurunan luas daun pada P2 dan P0 diimbangi dengan peningkatan kandungan pigmen fotosintesis untuk optimalisasi penyerapan cahaya. Secara umum aplikasi kompos dan asam humat dapat memperbaiki struktur tanah pasir. Aplikasi kompos lebih efektif meningkatkan retensi air dan pertumbuhan serta produktivitas tanaman herbaceous sawi hijau pada tanah pasir. Sandy soil is inherently infertile and has low water and nutrient retention capabilities. This study aims to evaluate the impact of compost and humic acid application on the productivity of sandy soil and the growth and productivity of mustard plants. The research was conducted experimentally in a greenhouse, where mustard seedlings were grown in sandy soil treated with soil amendments. Three treatments were employed: control (P0), compost application (P1), and humic acid application (P2). Soil productivity parameters measured included soil structure consistency and field capacity water content. Growth and productivity responses of the plants were assessed by measuring the percentage increase in root mass, lateral root length, root dry weight, number of leaves, leaf area, leaf dry weight, and photosynthetic pigment content (chlorophyll a, chlorophyll b, and carotenoids). Results indicated that the soil structure of sandy soil changed from loose to crumbly and cohesive after compost application and to firm after humic acid application. Both compost and humic acid applications led to increased field capacity water content, with P1 showing a higher moisture percentage (52.6%) compared to P2 (10.7%) and P0 (6.4%). The highest growth and productivity percentages in mustard plants were observed in P1, followed by P2 and P0, respectively: 3.2%, 2.3%, 1.8% (lateral root length), 59.4%, 47.2%, 33% (root dry weight), 21%, 19.6%, 14.5% (leaf area), and 28.4%, 24.9%, 24% (leaf dry weight). It increased photosynthetic pigment content to optimize light absorption and compensated for decreased leaf area in P2 and P0. Overall, applying compost and humic acid improved the structure of sandy soil, with compost being more effective in enhancing water retention and the growth and productivity of mustard plants on sandy soil.