Ammonia volatilization from nitrogen fertilizers applied to sugarcane straw

ABSTRACT Maintenance of crop residues over soil surface under conservational systems limits incorporation of nitrogen fertilizers into the soil. Application of urea over crop residues enhance N-NH3 volatilization losses, justifying the usage of urease inhibitors or N sources less susceptible to volatilization under such conditions. This study aimed to evaluate volatilization losses from N sources applied over sugarcane straw. A field trial was carried out in a sugarcane field in Iracemapolis, Sao Paulo on a Typic Kandiudox in June 2014. We used a complete block experimental design, with seven treatments and four replications. Treatments included Control [CO], ammonium nitrate [AN], NS30TM (ammonium nitrate-75% and ammonium sulfate-25% fused mixture) [NS30TM], ammonium nitrate plus ammonium sulfate (ammonium nitrate-75% and ammonium sulfate-25% physical mixture) [AN-AS], urea [UR], urea treated with 0.4% Cu and 0.15% B [UR-CuB], urea treated with 530 mg kg-1 of NBPT [UR-NBPT]. Treatments were applied at rate of 100 kg ha-1 N (except CO). Volatilization losses were quantified up to 30 days after fertilization (DAF). Maximum N-NH3 occurred 16 DAF for UR and UR-CuB and 20 DAF for UR-NBPT. Accumulated N-NH3 losses ranged from 20% (UR), 17% (UR-CuB), and 14% (UR-NBPT) of applied N; non-amidic sources showed losses lower than 1%. Adding urease inhibitor to urea shows potential in reducing volatilization losses even under application over large amounts of straw.

摘要：保护性耕作体系下将作物残体覆盖于土壤表面，会限制氮肥向土壤中的施入。将尿素施用于作物残体表面会加剧氨态氮（N-NH3）挥发损失，因此在这类条件下使用脲酶抑制剂（urease inhibitors）或不易挥发的氮源具有合理性。本研究旨在评估施用于甘蔗秸秆表面的各类氮源的氨挥发损失情况。2014年6月，研究团队在巴西圣保罗州伊拉塞马波利斯的一块典型高岭湿润氧化土（Typic Kandiudox）甘蔗田中开展了田间试验。试验采用完全随机区组设计，设置7个处理、4次重复。处理组分别为：对照[CO]、硝酸铵[AN]、NS30TM（硝酸铵75%与硫酸铵25%的熔融混合物）[NS30TM]、硝酸铵与硫酸铵物理混合物[AN-AS]、尿素[UR]、添加0.4%铜与0.15%硼的尿素[UR-CuB]、添加530 mg·kg⁻¹ N-正丁基硫代磷酰三胺（NBPT）的尿素[UR-NBPT]。除对照外，所有处理的施氮量均为100 kg·ha⁻¹。研究在施肥后30天（DAF）内对氨挥发损失进行了定量测定。结果显示，尿素[UR]与UR-CuB的氨挥发峰值出现在施肥后16天，UR-NBPT的氨挥发峰值则出现在施肥后20天。累积氨态氮挥发损失占施氮量的比例分别为：UR为20%、UR-CuB为17%、UR-NBPT为14%；非酰胺态氮源的挥发损失均低于1%。即便在大量秸秆覆盖的施用条件下，向尿素中添加脲酶抑制剂仍具备降低氨挥发损失的应用潜力。