Determining soil nitrogen (N) availability is essential in agriculture to minimise over-application, maximise growers’ returns and reduce potential environmental consequences. The present study assesses soil mineral N (nitrate-N and ammonium-N) using the diffusive gradients in thin-films (DGT) technique against the conventional potassium chloride (KCl) extraction. The DGT technique has demonstrated reliable predictability for plant-available P, Cu and Zn. However, the use of DGT to quantify soil N bioavailability is underreported and N measurements made with DGT have not been compared to plant growth responses or N uptake. A pot trial using wheat was performed to determine the suitability of the DGT technique to predict N plant uptake and plant biomass. Four contrasting soil types from South Australia were used, and four rates of N were applied to the soil. DGT devices and KCl extraction were used at sowing to measure soil mineral N. These data were then compared with plant relative yield (YR) and N uptake after harvesting the plants. Soil mineral N, as measured by both the DGT and KCl extraction techniques, demonstrated a significant positive correlation with YR, with an R2 value of 0.6; however, DGT-N extracted comparatively more nitrate (NO3–, >87 % of CN) than KCl-N (65 % of EN). Mineral N and NO3– extracted by both DGT and KCl significantly correlated with plant N uptake albeit this correlation was stronger for KCl (R2 = 0.8) than DGT (R2 = 0.6). The same parameters also positively and significantly correlated with YR, however in this case, both correlations were similar and only modest (R2 < 0.6 in all cases). These results are explained in terms of the differences between the pools of N accessed by these techniques and limitations related to soil N dynamics. In conclusion, KCl showed similar or better predictive ability for N uptake and yield response (YR) in wheat compared to DGT across four Australian soils. Given its low cost and ease of application, KCl presents a competitive advantage in this study.

中文翻译：

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植物对澳大利亚土壤中硝酸盐和铵态氮有效性的响应，通过薄膜中的扩散梯度 （DGT） 和 KCl 萃取来测量


确定土壤氮 （N） 的可用性在农业中至关重要，以最大限度地减少过度施用，最大限度地提高种植者的回报并减少潜在的环境后果。本研究使用薄膜扩散梯度 （DGT） 技术与传统氯化钾 （KCl） 提取评估土壤矿物氮（硝酸盐氮和铵态氮）。DGT 技术已证明植物可溶性 P、Cu 和 Zn 具有可靠的可预测性。然而，使用 DGT 量化土壤氮生物利用度被低估了，并且使用 DGT 进行的氮测量尚未与植物生长反应或氮吸收进行比较。使用小麦进行了盆栽试验，以确定 DGT 技术对预测氮植物吸收和植物生物量的适用性。使用了来自南澳大利亚的四种对比土壤类型，并将四种氮用量应用于土壤。播种时使用 DGT 设备和 KCl 萃取来测量土壤矿物质氮。然后将这些数据与植物相对产量 （YR） 和收获植物后的氮吸收进行比较。通过 DGT 和 KCl 提取技术测量的土壤矿物 N 与 YR 呈显著正相关，R2 值为 0.6;然而，DGT-N 提取的硝酸盐（NO3–，>87 % CN）比 KCl-N（65 % 的 EN）相对多。矿物氮和氮3– DGT 和 KCl 提取的 – 与植物氮吸收显著相关，尽管这种相关性对 KCl （R2 = 0.8） 比 DGT （R2 = 0.6） 更强。相同的参数也与 YR 呈正显著相关，但在这种情况下，两种相关性相似且仅适度（R2 < 0.6 在所有情况下）。这些结果是根据这些技术访问的氮池之间的差异以及与土壤氮动力学相关的限制来解释的。 总之，与DGT相比，KCl在四种澳大利亚土壤中对小麦氮吸收和产量反应（YR）的预测能力相似或更好。鉴于其低成本和易于应用，KCl 在本研究中表现出竞争优势。