Sistem Usahatani Berkelanjutan Berbasis Dinamika Unsur Hara pada Lahan Kering Masam - I Gusti Putu Wigena; Andriati Andriati (Indonesian Center for Agriculture Land Resource Development, 2016)
Abstrak. Dari aspek sebaran dan luasan, lahan kering masam memiliki potensi sebagai sumber pangan, tetapi ketidak sesuaian sifat fisika dan kimia tanah dengan kebutuhan tanaman memerlukan teknologi pengelolaan yang spesifik. Sifat fisika tanah kering masam: kepadatan tanah tinggi, daya pegang air rendah, permeabilitas lambat, erosi dan aliran permukaan tinggi. Sifat kimia: kadar bahan organik, unsur hara, KTK dan KB rendah, kadar oxida besi dan aluminium tinggi. Pada kondisi yang demikian, tumpangsari merupakan sistem usahatani berkelanjutan alternatif melalui perbaikan sifat fisika dan kimia tanah. Perbaikan sifat fisika tanah antara lain penurunan BD, porositas, dan kapasitas lapang tanah pada tumpangsari ubikayu + jagung + kacang tanah masing-masing berkisar 2,18 g cm-3; 49,12%; dan 37,99%; pada monokultur berkisar 2,59 g cm-3; 42,35%; dan 28,24. Neraca karbon dan nitrogen pada tumpangsari masing-masing +1,5 t ha-1 dan + 10 kg ha-1 tahun-1; pada monokultur -7,0 t ha-1 tahun-1 dan -60 kg ha-1 tahun-1. Tanaman lorong (alley cropping) merupakan usahatani berkelanjutan alternatif lainnya melalui perbaikan sifat fisika dan kimia tanah seperti meningkatkan kemampuan dalam mengikat/menyediakan air/lengas untuk memperlancar dinamika unsur hara ke permukaan akar melalui proses aliran masa dan difusi, meningkatkan kandungan bahan organik tanah, dan sebagai sumber unsur hara. Perbaikan sifat fisika tanah antara lain B.D, ruang pori total (RPT), pori drainase cepat (PDC), air-tersedia pada tanaman lorong berkisar 1,08 g cm-3; 59,2%; 25,6%; dan 14,6%; tanpa tanaman lorong masing-masing berkisar 1,28 g cm-3; 51,7%; 13,7%; dan 11,3%. Neraca karbon dan nitrogen pada tanaman lorong berkisar 2,73 dan 0,20%; tanpa tanaman lorong berkisar 1,31 dan 0,07%. Hasil padi gogo, kacang tanah, dan kacang hijau pada tanaman lorong berkisar 12,8; 11,3 dan 5,3 ku ha-1 dan tanpa tanaman lorong masing-masing berkisar 7,7; 7,8; dan 2,9 ku ha-1.Abstract. Based on its wide and spread, acid dry land has a higher potential as food crops resources, but unsuitability condition of soil physical and chemical properties with crops requirement need the specific technology to provide the optimum crop yields. The soil physical properties are high compactness (BD >1.2 gr cm-3), low of water holding capacity, bed permeabilitiy, and rate of soil eorison and ruhoff is high. The soil chemical properties are low of organic matter content, nutrients content, cation exchange capacity, and base saturation, while concentration of iron and aluminum oxides are higher concentration. On this condition, mix cropping can be an alternative sustainable farming system through improvement of physical and chemical properties. Improvement of physical properties including BD, porosity, and field capacity on mix cropping of cassava + maize + peanut were around 2.18 g cm-3; 49.12%; dan 37.99%; while on monoculture around 2.59 g cm-3; 42.35%; and 28.24%. Carbon and nitrogen balance on the mix cropping farming system were around +1.5 t ha-1 year-1 and + 10 kg ha-1 year-1, while on monoculture around -7.0 t ha-1 year-1 and -60 kg ha-1 year-1. Alley cropping is another one of sustainable alternative farming system through improvement of physical and chemical properties such as increasing of water holding capacity to accelerate nutrients dynamic into root surface areas by mass flow and diffusion processes, soil organic matter, and as sources of plat nutrients. Improvement of soil physical including BD, total porous, drainage porous, and available wateron alley cropping were around 1.08 g cm-3;, 59.2%; 25.6%; dan 14.6%; while on non alley cropping system around 1.28 g cm-3; 51.7%; 13.7%; dan 11.3%. Carbon and nitrogen content on alley cropping were around 2.73 and 0.20%, while on non alley cropping system around 1.31 dan 0.07%. The upland rice, peanut, and mung bean yields on alley cropping system were around 12.8, 11.3, and 5.3 ku ha-1; while on non alley cropping system around 7.7, 7.8, and 2.9 ku ha-1.