Strategies to Make Use of Plant Sensors‐Based Diagnostic Information for Nitrogen Recommendations

Abstract

Improvements of nitrogen use effi ciency (NUE) may be achieved through the use of sensing tools for N status determination. Leaf and canopy chlorophyll, as well as leaf polyphenolics concentrations, are characteristics strongly aff ected by N availability that are oft en used as a surrogate to direct plant N status estimation. Approaches with near-term operational sensors, handheld and tractor-mounted, for proximal remote measurements are considered in this review. However, the information provided by these tools is unfortunately biased by factors other than N. To overcome this obstacle, normalization procedures such as the well-fertilized reference plot, the no-N reference plot, and relative yield are oft en used. Methods to establish useful relationships between sensor readings and optimal N rates, such as critical NSI (nitrogen suffi ciency index), INSEY (in-season estimated yield), and the relationship between chlorophyll meter readings, grain yield, and sensor-determined CI (chlorophyll index) are also reviewed. In a few cases, algorithms for translating readings into actual N fertilizer recommendation have been developed, but their value still seems limited to conditions similar to the ones where the research was conducted. Near-term operational sensing can benefi t from improvements in sensor operational characteristics (size and shape of footprint, positioning) or the choice of light wavebands more suitable for specifi c conditions (i.e., genotype, growth stage, or crop density). However, one important limitation to their widespread use is the availability of algorithms that would be reliable in a variety of soil and weather conditions.

Dose de nitrogênio associada à produtividade de batata e índices do estado de nitrogênio na folha

“…O aumento do valor do índice SPAD devido à adubação nitrogenada mostra a relação entre o N e a intensidade de cor verde da planta, a maior síntese de clorofila (Taiz & Zeiger, 2009) e o aumento da atividade fotossintética, possibilitando o aumento da produção (Stone et al, 2002). Além disso, o clorofilômetro SPAD tem a capacidade de detectar o aparecimento da deficiência de N antes que seja visível ao olho humano e cedo o suficiente para corrigir essa deficiên-cia, sem redução na produtividade (Samborski et al, 2009), desde que não haja interrupção indesejada do ciclo e outros fatores não se tornem limitantes.…”

Using an unmanned aerial vehicle to evaluate nitrogen variability and height effect with an active crop canopy sensor

“…Passive sensors rely on the sun to illuminate the maize canopy, while active sensors use an internal light source. Each type of sensor has been documented as an appropriate way to correlate canopy reflectance with chlorophyll and N status of maize (Samborski et al 2009;Li et al 2010). Passive sensors require calibration and data handling techniques to account for sun angle, illumination, camera optics, rectification of imagery, and require specialized software to analyze the imagery (Berni et al 2009).…”

O desafio do manejo do nitrogênio no contexto da produtividade agricola e da vulnerabilidade ambiental

“…Como ejemplos de equipos electrónicos, se puede destacar el SPAD-502, que mide el intensidad del color verde de las hojas y el contenido en clorofila, relacionados con la concentración de nitrógeno. Ya equipos como el DUALEX 4 y el MULTIPLEX miden el contenido de flavonoles en hoja (SAMBORSKI et al, 2009), el cual es un indicador del estrés en la planta debido a una deficiencia de N (CARTELAT et al, 2005). Otros equipos como el Crop Circle ACS-470 y N-SENSOR miden la reflectancia de una pequeña superficie foliar en una área representativa del cultivo.…”