Abstract
Knowing the total Nitrogen content (Nt) of forage maize (Zea mays) is important so that decisions can be made quickly and efficiently to adjust the timing and amount of both irrigation and fertilizer. In 2017 and 2018 during three growing cycles in two study plots, leaf samples were collected and the Dumas method was used to estimate Nt. During the same growing seasons and on the same sampling plots, a Parrot Sequoia camera mounted on an unmanned aerial vehicle (UAV) was used to collect high resolution images of forage maize study plots. Thirteen multispectral indices were generated and, from these, a Random Forest (RF) algorithm was used to estimate Nt. RF is a machine-learning technique and is designed to work with extremely large datasets. Overall analysis showed five of the 13 indices as the most important. One of these five, the Transformed Chlorophyll Absorption in Reflectance Index/Optimized Soil-Adjusted Vegetation Index, was found to be the most important for estimation of Nt in forage maize (R2 = 0.76). RF handled the complex dataset in a time-efficient manner and Nt did not differ significantly when compared between traditional methods of evaluating Nt at the canopy level and using UAVs and RF to estimate Nt in forage maize. This result is an opportunity to explore many new research options in precision farming and digital agriculture.
Highlights
Nitrogen (N), in both its organic and inorganic forms, is essential to promote leaf development and crop growth
Random Forest (RF) (with five and thirteen indices derived from Unmanned Aerial Vehicles (UAVs))
Chen et al [22], where they found a relationship between the TCARI/OSAVI and the Nitrogen content (Nt) in corn (R2 = 0.66), while Berni et al [10] reported that the TCARI/OSAVI index minimizes the effect of bare soil and variation of leaf area in olive trees, providing predictive relationships to estimate chlorophyll concentration using multispectral imaging
Summary
Nitrogen (N), in both its organic and inorganic forms, is essential to promote leaf development and crop growth. Nitrogen is present in the soil in two ways: the decomposition of plants naturally high in N such as legumes, buckwheat, and others (organic N; amino acids, proteins, and nucleotides), and the human application of fertilizer (inorganic N; (ammonium [NH4 + ], nitrates [NO3 − ], Nitrogen gas [N2 ], and nitrites [NO2 − ])). Maize (Zea mays) has one of the highest photosynthetic rates per unit of N [1] and is considered a C4 plant. The N content in maize determines the yield and quality of grain and must be available in the soil in adequate quantities throughout the growing season.
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.
