Abstract
Although hyperspectral remote sensing techniques have increasingly been used in the nutritional quantification of plants, it is important to understand whether the method shows a satisfactory response during the various phenological stages of the crop. The aim of this study was to quantify the levels of phosphorus (P), potassium (K), calcium (Ca) and zinc (Zn) in the leaves of Vigna Unguiculata (L.) Walp using spectral data obtained by a spectroradiometer. A randomised block design was used, with three treatments and twenty-five replications. The crop was evaluated at three growth stages: V4, R6 and R9. Single-band models were fitted using simple correlations. For the band ratio models, the wavelengths were selected by 2D correlation. For the models using partial least squares regression (PLSR), the stepwise method was used. The model showing the best fit was used to estimate the phosphorus content in the single-band (R² = 0.62; RMSE = 0.54 and RPD = 1.61), band ratio (R² = 0.66; RMSE = 0.65 and RPD = 1.52) and PLSR models, using data from each of the phenological stages (R² = 0.80; RMSE = 0.47 and RPD = 1.66). Accuracy in modelling leaf nutrients depends on the phenological stage, as well as the amount of data used, and is more accurate with a larger number of samples.
Highlights
The cowpea (Vigna unguiculata (L.) Walp.) is a crop that originated in Africa and is commonly used as a primary source of protein [1]
The use of reflectance data obtained by spectroscopy allows for the quantification of nutrient content; the degree of precision of the models varies according to the phenological stage of the crop and the quantity of data utilised, being more precise with a greater quantity of information and with the utilisation of data from all stages studied
The partial least squares regression associated to the spectroscopy shows the great potential for the development of predictive models of nutrients in Vigna unguiculata (L.) Walp
Summary
The cowpea (Vigna unguiculata (L.) Walp.) is a crop that originated in Africa and is commonly used as a primary source of protein [1]. The crop generates employment and income for the smallholders responsible for its production [4]. At least 300 mm of rain is necessary for production to be viable, which must be well distributed throughout the crop cycle so that water is available to the plants at all stages of their development [5]. Climatic requirements when cultivating the cowpea are not high, and as such, it can be grown at various altitudes from latitudes 40◦ N to 30◦ S [6]; crop development is best in temperatures ranging from 18 to 34 ◦C. Nutrient availability is directly related to crop development [7]; to assess whether the adopted soil management has a positive result on the plant, leaf analysis is used
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
