Estimating Plant Nitrogen Concentration of Maize Using a Leaf Fluorescence Sensor across Growth Stages

Abstract

Nitrogen (N) is one of the most essential nutrients that can significantly affect crop grain yield and quality. The implementation of proximal and remote sensing technologies in precision agriculture has provided new opportunities for non-destructive and real-time diagnosis of crop N status and precision N management. Notably, leaf fluorescence sensors have shown high potential in the accurate estimation of plant N status. However, most studies using leaf fluorescence sensors have mainly focused on the estimation of leaf N concentration (LNC) rather than plant N concentration (PNC). The objectives of this study were to (1) determine the relationship of maize (Zea mays L.) LNC and PNC, (2) evaluate the main factors influencing the variations of leaf fluorescence sensor parameters, and (3) establish a general model to estimate PNC directly across growth stages. A leaf fluorescence sensor, Dualex 4, was used to test maize leaves with three different positions across four growth stages in two fields with different soil types, planting densities, and N application rates in Northeast China in 2016 and 2017. The results indicated that the total leaf N concentration (TLNC) and PNC had a strong correlation (R2 = 0.91 to 0.98) with the single leaf N concentration (SLNC). The TLNC and PNC were affected by maize growth stage and N application rate but not the soil type. When used in combination with the days after sowing (DAS) parameter, modified Dualex 4 indices showed strong relationships with TLNC and PNC across growth stages. Both modified chlorophyll concentration (mChl) and modified N balance index (mNBI) were reliable predictors of PNC. Good results could be achieved by using information obtained only from the newly fully expanded leaves before the tasseling stage (VT) and the leaves above panicle at the VT stage to estimate PNC. It is concluded that when used together with DAS, the leaf fluorescence sensor (Dualex 4) can be used to reliably estimate maize PNC across growth stages.

Canopy Fluorescence Sensing for In-Season Maize Nitrogen Status Diagnosis

“…Simulated by a crop model (CERES-Maize) based on field experiments and historical weather information, the long-term economic optimal N rate in this study site was found to be 198 ± 35 kg ha −1 [51]. However, after reaching the optimal N level, little excessive N was accumulated by luxury N uptake, and the N concentration in maize plants did not change significantly [35]. This led to the indistinctive variation of the fluorescence indices under the two high N rates.…”

“…Among them, the application of the normalized N sufficient index (NSI) is a very common procedure that has been used in many studies [18,32,34]. A recent study proposed a modified approach to estimate maize PNC across growth stages based on the use of days after sowing (DAS) [35].…”

Mycorrhiza improves plant growth and photosynthetic characteristics of tea plants in response to drought stress

“…The ratio of chlorophyll to flavonoids is the nitrogen balance index, which is an important indicator of the nitrogen status in plants and reflects the growth of plants and the degree of absorption and utilization of proteins by the organism (Dong et al, 2020). DS can inhibit the absorption of nitrogen by plants, resulting in insufficient nutrient supply in plants (Sarhadi et al, 2020), while AMF can improve the absorption of nitrogen and maintain normal nutrient supply (He et al, 2018).…”

Evaluation of Three Portable Optical Sensors for Non-Destructive Diagnosis of Nitrogen Status in Winter Wheat

“…Leaf and plant N concentrations (LNC, PNC) have been used as vital parameters of crop N status [ 5 ]. However, N concentrations are dependent on the plant biomass, such that two different plants with the same N concentration but differ in plant biomass.…”