Optimizing application of biochar, compost and nitrogen fertilizer in soybean intercropping with kayu putih (Melaleuca cajuputi)

ABSTRACT Waste resulted from the distillation of kayu putih leaves is a problem in almost all kayu putih refineries throughout Indonesia due to its enormous availability and un-utilization. It has potential to be used as an organic fertilizer source due to its nutrient content (macro and micro) which is higher than organic fertilizer from animals. The use of kayu putih waste is useful to complement and increase the efficiency of nitrogen fertilizer in soybean intercropping with kayu putih . This study aimed to determine the optimum values of kayu putih waste and nitrogen fertilizer based on three scenarios: economic, environmental, and eco-environmental. A two-year experiment (2018-2019) was carried out in a central composite design (CCD) with two replications as the response surface methodology (RSM) at the Menggoran Forest Resort, Playen District, Yogyakarta Forest Management, Indonesia. The treatments consist of biochar and compost levels made from kayu putih waste (0, 2.5, and 5.0 t ha-1) and nitrogen fertilizer levels supplied by ammonium sulfate (0, 50, and 100 kg ha-1) as independent variables. The observations conducted on nitrate reductase activity (NRA), total chlorophyll (TC), leaf photosynthesis rate (LPR), nitrogen loss (NL), nitrogen use efficiency (NUE), and seed yield (SY). The response variables were fitted in a full quadratic polynomial model. The results showed that the resource-based on the eco-environmental scenarios was the most favorable cropping strategy for the soybean production intercropping with kayu putih with the optimum value of 2.890 t ha-1 of biochar, 2.27 t ha-1 of compost, and 67.85 kg ha-1 of ammonium sulfate. This recommendation can reduce the use of ammonium sulfate by 32.15 % and increase of NRA, TC, LPR, NL, NUE, and SY by 12.96, 2.80, 17.18, 21.66, 7.23, and 17.29 %, respectively, compared to the single application of ammonium sulfate fertilizer.

摘要 印尼全境几乎所有白千层（kayu putih）叶蒸馏加工厂均面临白千层叶蒸馏废弃物的处理困境：该类废弃物产量庞大且长期未得到有效资源化利用。因其富含大量及微量营养元素，且含量高于动物源有机肥，该废弃物具备开发为有机肥源的潜力。将白千层蒸馏废弃物应用于白千层与大豆间作体系，可辅助补充氮肥并提升氮肥利用效率。本研究旨在基于经济、环境与生态环境三类情景，确定白千层废弃物与氮肥的最优配施用量。试验于2018-2019年在印尼日惹森林管理局普莱恩区蒙戈兰森林度假区开展，采用响应面法（response surface methodology, RSM）框架下的中心复合设计（central composite design, CCD），设置2次重复。试验自变量为白千层废弃物制备的生物炭与堆肥施用量（0、2.5、5.0 t·ha⁻¹），以及以硫酸铵为供氮源的氮肥施用量（0、50、100 kg·ha⁻¹）。观测指标包括硝酸还原酶活性（nitrate reductase activity, NRA）、总叶绿素（total chlorophyll, TC）、叶片光合速率（leaf photosynthesis rate, LPR）、氮素流失量（nitrogen loss, NL）、氮素利用效率（nitrogen use efficiency, NUE）与籽粒产量（seed yield, SY）。采用全二次多项式模型对各响应变量进行拟合。结果表明，针对白千层与大豆间作种植体系，基于生态环境情景的配施方案为最优种植策略，其最优用量为生物炭2.890 t·ha⁻¹、堆肥2.27 t·ha⁻¹及硫酸铵67.85 kg·ha⁻¹。与单施硫酸铵相比，该推荐方案可减少32.15%的硫酸铵用量，同时分别使硝酸还原酶活性、总叶绿素含量、叶片光合速率、氮素流失量、氮素利用效率及籽粒产量提升12.96%、2.80%、17.18%、21.66%、7.23%及17.29%。