Application of UAV multispectral imaging for determining the characteristics of maize vegetation

M. Änäkkälä¹*, A. Lehtilä²³, P.S.A. Mäkelä⁴ and A. Lajunen¹

¹University of Helsinki, Faculty of Agriculture and Forestry, Department of Agricultural Sciences, Koetilantie 5, FI00790 Helsinki, Finland
²Natural Resources Institute Finland (Luke), Latokartanonkaari 9, FI00790 Helsinki, Finland
³University of Helsinki, Helsinki Institute of Sustainability Sciences (HELSUS), Yliopistonkatu 4, FI00100 Helsinki, Finland
⁴University of Helsinki, Faculty of Agriculture and Forestry, Department of Agricultural Sciences, Latokartanonkaari 5, FI00790 Helsinki, Finland
*Correspondence: mikael.anakkala@helsinki.fi

Abstract:

Interest in forage maize (Zea mays L.) cultivation for livestock feed has grown in northern conditions. In addition, it is important to develop methods and tools to monitor crop development and other characteristics of the crop. For these purposes UAVs are very efficient and versatile tools. UAVs can be equipped with a variety of sensors like lidar or different types of cameras. Several studies have been conducted where data collected by UAVs are used to estimate different crop properties like yield and biomass. In this research, a forage maize field experiment was studied to examine how well the aerial multispectral data correlated with the different properties of the vegetation. The field test site is located in Helsinki, Finland. A multispectral camera (MicaSense Rededge 3) was used to take images from five spectral bands (Red, Green, Blue, Rededge and NIR). All the images were processed with Pix4D software to generate orthomosaic images. Several vegetation indices were calculated from the five spectral bands. During the growing season, crop height, chlorophyll content, leaf area index (LAI), fresh and dry matter biomass were measured from the vegetation. From the five spectral bands, Rededge had the highest correlation with fresh biomass (R² = 0.273). The highest correlation for a vegetation index was found between NDRE and chlorophyll content (R² = 0.809). A multiple linear regression (MLR) model using selected spectral bands and vegetation indices as inputs showed high correlations with the field measurements.

Key words:

Biochar Dosage Impact on Physical Soil Properties and Crop Status

V. Novák¹*, K. Křížová¹² and P. Šařec¹

¹Czech University of Life Sciences Prague, Faculty of Engineering, Department of Machinery Utilization, Kamýcká 129, CZ16500 Prague, Czech Republic
²Crop Research Institute, Division of Crop Protection and Plant Health, Drnovská 507/73, CZ16106 Prague, Czech Republic
*Correspondence: novakvaclav@tf.czu.cz

Abstract:

In the context of climate change and the ongoing population growth, current agriculture inevitably faces many challenges. Long periods of drought are often followed by shorter periods of heavy precipitation and degraded soil is often unable to retain the rainfall water properly. Apart from common organic fertilizers, soil amendments are currently considered a promising solution that might improve soil quality. The most discussed one is biochar, a natural soil conditioner that might under certain conditions improve soil properties. This study is based on the experiment that was established in 2017 in order to determine the impact of biochar dosage and it’s effect over time. Four parcels approximately 15×30 m were designed in Rapotín, Czech Republic. Each of them was treated with a specific dose of biochar (15, 30, 45, 60 t ha^-1), and selected soil physical properties such as penetration resistance and reduced bulk density were then measured at the beginning of the cropping season 2019. In addition, vegetation properties were investigated with the use of handheld sensors repeatedly during the season on winter wheat. The dataset contained information about chlorophyll and nitrogen content as well as Normalized Difference Vegetation Index estimations. Acquired values were later compared with the results obtained from the fifth variant founded in 2014 with a 15 t ha^-1 dose and from the control variant. Although the dosage levels applied were quite substantial, no significant difference was found when evaluating selected soil properties. Crop response gave similar results. Any of the examined characteristics differed among the 2017 variants and control. Nevertheless, when compared to the 2014 variant, clearly different results were detected. Thus, this study concluded that the effect of biochar dosage is might not be as significant factor, however, the time effect likely is. Therefore, the study has to continue and soil/crop properties will be observed in the upcoming season as well.

Key words:

handheld sensor, penetration resistance, reduced bulk density, soil conditioner, vegetation index