Organic amendments to reduce N2O in subtropical horticulture systems

The aims of agricultural nitrogen (N) management are to
provide sufficient N to plants to maximize crop growth and
yield, whilst minimising negative environmental impacts such as
nitrous oxide (N2O), a potent greenhouse gas (GHG). The flux
of this gas from agricultural soils is correlated to the amount
of N fertilizer applied, as well as soil and environmental
conditions. Reducing the amount of synthetic fertiliser inputs
and promoting the storage of organic carbon through the use of
organic soil amendments may be an effective pathway to reduce
GHG emissions and improve N use efficiency. A fully randomized
block design was established on a black vertosol in a
subtropical horticultural cropping system to estimate the
efficiency and environmental impact of different types of raw
verses composted manure in combination with reduced synthetic
fertilizer inputs. The treatments consisted of all combinations
of raw and composted cattle feedlot (FM) and chicken manure
(CM) with synthetic nitrogen at commercial rates (100%) or
reduced rates (100% - N[org amend]). High temporal resolution
gas sampling (sub-daily) was conducted using automated gas
chambers on the CM treatment and manual gas sampling technique
(weekly) on the FM will be used to quantify the N2O dynamic
emission. Complementary soil nitrogen data will give a better
understanding of the effects of organic amendments in relation
to N2O emissions.

农业氮（nitrogen, N）管理的核心目标，是为作物提供充足氮素以最大化其生长与产量，同时尽可能降低一氧化二氮（nitrous oxide, N₂O，一种强效温室气体（greenhouse gas, GHG））等负面环境影响。农田土壤中该气体的排放通量，与施用的氮肥总量、土壤及环境条件均存在显著相关性。减少合成肥料投入，并通过施用有机土壤改良剂（organic soil amendments）促进土壤有机碳固存，或是降低温室气体排放、提升氮素利用效率的有效路径。本研究在亚热带园艺种植系统的黑色变性土（black vertosol）地块上设置完全随机区组设计（fully randomized block design），以评估不同类型未堆肥与堆肥粪肥配合减量合成氮肥的施用效率及环境影响。试验处理涵盖未堆肥与堆肥的牛场饲喂粪肥（cattle feedlot manure, FM）和鸡粪（chicken manure, CM），分别配合商品级常规用量（100%）或减量合成氮肥的所有组合，其中减量水平为100%标准用量减去有机改良剂携带的氮素量。针对鸡粪（CM）处理组，将采用自动化气室（automated gas chambers）开展高时间分辨率亚每日气体采样；针对牛场饲喂粪肥（FM）处理组，则采用每周1次的手动气体采样技术，以量化一氧化二氮的动态排放特征。配套的土壤氮素监测数据，将有助于更深入解析有机改良剂对一氧化二氮排放的影响机制。