Abstract Accurate estimates of light (Photosynthetically Active Radiation or PAR) absorption, in addition to other interactions is imperative to quantify growth, productivity, energy and water balance and other physiological and biophysical processes in any vegetative surface. Currently, a comparative assessment of light interaction patterns across row crops is lacking, especially under current levels of productivity achieved in the U.S. High Plains. Here, we continuously measured canopy light balance components at high-frequency (15 min) to characterize transmittance (R), reflectance (R), fraction of intercepted PAR (fIPAR), fraction of absorbed PAR (fAPAR), light extinction coefficients (k), and light use efficiency (LUE) comparatively across maize, soybean, sorghum and winter wheat under optimal growth conditions. While maximum fAPAR was 88-96% of incoming PAR in all crops, mean fAPAR varied from 82% in sorghum to 46% in winter wheat; while k ranged from 0.36 (winter wheat) to 0.48 (sorghum and soybean), and these differences reflect highly crop-specific signatures. Conversion factors among fIPAR and fAPAR and LUE based on either component (LUEi and LUEa) were quantified that were substantially different from the conventionally used values; especially during early and late growth stages. A commonly employed approach of solar-noon light sampling was evaluated, and it was found that early and late stages of crop growth experience greater potential errors (as high as 110%) under this sampling approach, and hence should be avoided. LUEa was the highest for maize (5.3 g MJ−1), followed by sorghum (4.1 g MJ−1), winter wheat (4.0 g MJ−1) and soybean (3.1 g MJ−1). The datasets measured, analyzed and interpreted here present unprecedented quantities of biomass productivity and canopy light use parameters for four major cropping systems, and hence, should be accounted for in crop growth and productivity modeling applications to enhance predictive accuracy and robustness.

中文翻译：

---

最佳生长条件下行作物冠层的光相互作用、使用和效率

摘要 准确估计光（光合有效辐射或 PAR）吸收以及其他相互作用对于量化任何植被表面的生长、生产力、能量和水平衡以及其他生理和生物物理过程是必不可少的。目前，缺乏对中耕作物间光相互作用模式的比较评估，尤其是在美国高平原目前实现的生产力水平下。在这里，我们在高频（15 分钟）下连续测量冠层光平衡分量，以表征透射率（R）、反射率（R）、截获 PAR 的分数（fIPAR）、吸收的 PAR 的分数（fAPAR）、消光系数（k )，以及最佳生长条件下玉米、大豆、高粱和冬小麦的光利用效率 (LUE)。虽然所有作物的最大 fAPAR 是传入 PAR 的 88-96%，但平均 fAPAR 从高粱的 82% 到冬小麦的 46% 不等；而 k 的范围从 0.36（冬小麦）到 0.48（高粱和大豆），这些差异反映了高度特定的作物特征。基于任一成分（LUEi 和 LUEa）的 fIPAR 和 fAPAR 和 LUE 之间的转换因子被量化，与常规使用的值有很大不同；尤其是在早期和晚期生长阶段。对一种常用的正午光采样方法进行了评估，发现在这种采样方法下，作物生长的早期和晚期经历了更大的潜在误差（高达 110%），因此应避免。LUEa 最高的是玉米（5.3 g MJ-1），其次是高粱（4.1 g MJ-1）、冬小麦（4.0 g MJ-1）和大豆（3.1 g MJ-1）。