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Canopy reflectance informs in‐season malting barley nitrogen management: An ex‐ante classification approach
Agronomy Journal ( IF 2.1 ) Pub Date : 2020-08-04 , DOI: 10.1002/agj2.20397
Taylor S. Nelsen 1 , Mark E. Lundy 1, 2
Affiliation  

Malting barley (Hordeum vulgare) requires precise nitrogen (N) fertilizer management to achieve a narrow range of grain protein content (∼9–10.5%) while maintaining yields, but practical tools to accomplish this are lacking. This study hypothesized that canopy reflectance (Normalized Difference Vegetation Index (NDVI)) measured at tillering (Feekes 2–3) and expressed as a sufficiency index (SI), can estimate the likelihood of a site‐specific response to in‐season N fertilizer in malting barley. Canopy reflectance was measured from plots at tillering with a GreenSeeker and unmanned aerial vehicle (UAV) borne multispectral cameras in trials across heterogeneous California agroecosystems. Field experiments included a range of N fertilizer application rates (0–168 kg N ha−1) and timings (pre‐plant, tillering, or evenly split), and resulted in a range of crop N sufficiency/deficiency. NDVI‐based SI measurements were categorized into one of three quantitative categories (low, medium, and high) without additional experimental context using Gaussian mixture modeling. Despite that 85% of variation in protein yield was due to site‐year, the reflectance‐based categories indicated whether N fertilizer applied in‐season would increase protein yield (p < .01). Nitrogen application at tillering increased yield and protein for plots in the “low” and “medium” SI categories (45 and 4% for yield and 16 and 12% for protein, respectively) (p < .05), while “high” SI plots had neither yield (p = .23) nor protein (p = .26) increases. Importantly, the broader agronomic conditions of a site primarily determined whether response to in‐season N manifested as increased yield or protein.

中文翻译:

冠层反射率告知季节大麦制氮管理:事前分类方法

麦芽大麦(Hordeum vulgare)需要精确的氮(N)肥管理,以在保持产量的同时实现狭窄的谷类蛋白质含量(约9-10.5%),但是缺少实现这一目标的实用工具。这项研究假设,在分till时(第2–3周)测得的冠层反射率(归一化植被指数(NDVI))可以表示为充足指数(SI),可以估算针对季节施氮的特定地点响应的可能性在麦芽大麦中。冠层反射率是使用GreenSeeker和无人驾驶飞机(UAV)承载的多光谱相机从分at时的地块中测得的,这些摄像机在加利福尼亚州不同类型的农业生态系统中进行了试验。田间试验包括一系列氮肥施用量(0–168 kg N ha -1)和时机(播种前,分split或均匀分裂),导致作物的氮素充足/不足。基于高斯混合模型,基于NDVI的SI测量可分为三个定量类别(低,中和高)之一,无需额外的实验环境。尽管蛋白质产量的85%的变化是由于地点年造成的,但基于反射率的类别表明,在季节内施用氮肥是否会增加蛋白质产量(p  <.01)。分low施氮增加了“低”和“中” SI类别(分别为45%和4%的产量和16%和12%的蛋白质)的地块的产量和蛋白质(p  <.05),而“高” SI地块既没有产量(p  = 0.23)也没有蛋白质(p = 0.26)增加。重要的是,该位点的更广泛的农艺条件主要决定了对季节N的反应是否表现为产量或蛋白质的增加。
更新日期:2020-08-04
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