Estimation of Corn Leaf Area Index and Ground Cover With Vegetation Indices as a Result of Irrigation Dose

Abstract

New technologies have been implemented in the agricultural sector to improve crop production and resource management including irrigation water. A three-year long project was conducted to determine whether vegetation indices (VIs) could be used to estimate the leaf area index (LAI) as well as the soil cover fraction (fc) at different crop growth stages in order to use these parameters in a future study concerning irrigation through drones. A low cost unmanned aerial vehicle (drone) and a multispectral camera were used to calculate different VIs of corn (Zea mays). The irrigation scheduling based on the FAO Penman-Monteith equation and the drip irrigation method were used. Three treatments were organized in three replications and the irrigation doses were equal to 100%, 75%, and 50% of the daily evapotranspiration respectively. The Simple and Multiple Regression analysis were used and different equations were formed where the VIs were the predictor variables and the LAI and fc the predicted ones. According to the two-year period data (2018-2019), during 2018 the average maximum LAI in the full irrigation treatment (100%) was 4.1. In the medium irrigation treatment (75%) the LAI was 4.0. The LAI in the third treatment (50%) was 3.9. In 2019, the LAI was 3.7 (100% treatment). In the second treatment, the LAI was 3.3. The LAI in the third treatment was 3.0. According to the results different VIs and prediction equations could be used to estimate the LAI values with high accuracy with the in situ measurements as well as the soil cover fraction.

The effects of high temperature and low humidity on crop water stress index of seed pumpkin plants (Cucurbita pepo L.) in semi-arid climate conditions

“…However, this relationship is sensitive to water stress. Under water deficit conditions, limited nutrient transport from roots to leaves restricts chlorophyll production and slows leaf expansion, significantly decreasing LAI and CC [Papanikolaou and Sakellariou-Makrantonaki 2020]. Decreased canopy greenness and photosynthetic potential can significantly impact plant growth and productivity.…”

“…A portable chlorophyll meter (Minolta SPAD-502, Osaka, Japan) was used to measure chlorophyll content (CC, SPAD). The leaf area index (LAI) was determined using an LI-COR LAI-2000 sensor and plotter [Papanikolaou and Sakellariou-Makrantonaki 2020].…”

Estimation of corn coefficients with vegetation indices using multispectral camera and drone

“…As a depletion fraction, a value of 0.50 was used according to Allan et al (1998). The practical applied irrigation dose was found to be equal to 51 mm which was used to calculate the maximum irrigation interval for the most crucial month of the irrigation period (Papanikolaou and Sakellariou-Makrantonaki 2020b). Following this procedure, the maximum irrigation interval was calculated as the quotient of the division between the practical applied irrigation dose and the average ET o of the crucial month for the Central Greek conditions (July, ET o ≈ 6.3 mm•day -1 ), based on recorded data, and was found to be 8 days.…”

“…Vegetation indices are used to assess the health of cultivated plants in open field conditions (Papanikolaou and Sakellariou-Makrantonaki 2020a). However, they are also used in the estimation of various crop characteristics, such as the leaf area index (Potgieter et al 2017), the estimation of the soil cover by the foliage of cultivated plants (Toureiro et al 2017;Papanikolaou and Sakellariou-Makrantonaki 2020b), and the estimation of biomass production (Latifi et al 2015;Papanikolaou and Sakellariou-Makrantonaki 2020a).…”

“…In the present research corn was chosen because it is one of the most important cultivated plants for the agricultural economy of Greece as it has great nutritional value (Papanikolaou and Sakellariou-Makrantonaki 2020b). Secondly, the Greek farmers are already experienced in corn cultivation techniques and they have already made large investments in agricultural equipment used in corn cultivation.…”