Lai 2200c plant canopy analyzer

Five representative plants with similar growth were selected from each plot. Their plant height (natural vertical distance from the ground surface to the highest part of the maize leaf measured before VT, and the distance from the ground surface to the tip of the male ear of the main stem after VT) and ear height (height from the base of the cob to the ground) were measured using a ruler. A straightedge and vernier calipers were used to determine the internode lengths of the second and third nodes at the base of the sample stalks and the stalk thickness (measured on the broad side of the ellipse), respectively. Stalk strength was determined using the YYD-1 stalk strength tester (Zhejiang Top Cloud-agri Technology Co., Ltd., Hangzhou, Zhejiang, China).
LAI values were determined using the LAI-2200C Plant Canopy Analyzer (LI-COR, Lincoln, NE, USA) at each physiological period of the maize. SPAD directly reflects the relative chlorophyll content in the leaves, which is measured with a chlorophyll meter (SPAD-502 Plus, Konica Minolta Sensing, Inc., Sakai, and Osaka, Japan).

Cassava agronomic traits such as leaf area index (LAI), canopy height (CH), above-ground biomass (AGB) and below-ground biomass (BGB) were acquired as ground-truth measurements. Five plants per plot were measured using LICOR LAI-2200C Plant Canopy Analyzer [37 ] during trial two. CH was sampled from soil level to the upper canopy at all four important phenological stages: elongation (EL), early bulking (EBK), late bulking (LBK) and dry matter accumulation (DMA) in both the trials. Each phenological stage is defined in Table 1. CH of 21 and five plants per plot were measured in trial one and two, respectively. The AGB and BGB were measured at the harvest time in both the trials using a conventional scale with the accuracy of 1 g. For AGB, three and five plants per plot were sampled in trial one and two, respectively. For BGB, 15 and 45 plants per plot were sampled in trial one and two, respectively.

Weather data were gathered from the Oklahoma Mesonet station (http://www.mesonet.org/index.php/weather/local/elre) in El Reno (ELRE), OK. The Mesonet tower is located on the native tallgrass prairie used in this study at 35°32.9′N and 98°02.2′W. Data used from Mesonet measurements included average rainfall, maximum air temperate, average air temperature, and minimum air temperature. Similar weather data for croplands were collected from eddy covariance stations located in those fields. Soil chemical analysis was performed at the Oklahoma State University Soil, Water, and Forage Analytical Laboratory (http://soiltesting.okstate.edu/). Tests included topsoil nitrate, organic matter, total nitrogen, and ammonium. Gravimetric water content was determined by oven drying for ≥24 h at 65°C or until the weight no longer changed (17 (link)). Leaf area index (LAI) was measured nondestructively using an LAI-2200C plant canopy analyzer (LI-COR Inc., Lincoln, NE), and the percent canopy cover (Canopy%) was determined using the Canopeo app. The aboveground biomass was collected destructively from five randomly located 0.5 × 0.5 m² quadrats within each field at 2-week intervals during the active growing season. Dry biomass weights were recorded after drying samples in forced-air oven at 70°C for a minimum of 48 h (91 (link)).