Comparison of Four Nondestructive Techniques for Estimating Standing Crop in Shortgrass Plains

Abstract

placed on clipping, using it only for calibration and validation within trials. Nondestructive standing crop estimators are important for efficientThe canopy analyzer (CA) (LI-COR, Lincoln, NE) monitoring of native and agronomic systems. This study evaluated is a fast, nondestructive instrument that indirectly estiplot and pasture estimates of standing crop using LAI-2000, visual mates leaf area index (LAI; Welles and Norman, 1991). obstruction, canopy height, and weighted plate measurements. Research was conducted in Lubbock County, Texas, in 1999 on areas Direct measurements of LAI using the LAI-3000 area dominated by Amarillo fine sandy loam (fine-loamy, mixed, thermic meter (LI-COR, Lincoln, NE) have shown a positive Aridic Paleustalfs). Five hundred plot estimation samples were collinear relationship between leaf area and SC (Engel et lected for each method along 25 transects, and each transect mean was al., 1987). Since the CA measures foliage area per unit used for the pasture estimation trials. Coefficients of determination of ground area, we hypothesized a positive relationship improved as we moved from plot (0.34, 0.85, 0.37, and 0.70) to pasture would exist between CA measurements and SC.(0.67, 0.87, 0.59, and 0.83) estimation for LAI-2000, visual obstruction,

A Combination of Plant NDVI and LiDAR Measurements Improve the Estimation of Pasture Biomass in Tall Fescue (Festuca arundinacea var. Fletcher)

“…Trotter et al [9] provides a review of these techniques which include visual assessment, pasture height recording devices, weighted plate meters, combinations of height and weighted plate meters, electrical capacitance probes, pendulum sensors as well as active optical sensors (AOS). Each of these techniques have their own advantages and disadvantages, however common issues included limited accuracy when dealing with spatially-variable phenology, morphology, species composition and green vs. dry fraction, e.g., [10][11][12][13].…”

“…The height of the vegetation canopy has been used to measure plant volume and to infer biomass with success in the past [11,12,[22][23][24][25][26]. Of particular interest is the work by King et al [22], who reported that the sward height was linearly related to both the LAI and biomass over a range of 2 cm to 8 cm in two ryegrass dominant swards.…”

Developing in situ Non-Destructive Estimates of Crop Biomass to Address Issues of Scale in Remote Sensing

“…In addition, with a high density of biomass estimates generated by these techniques, transects can be made that account for uncertainties over heterogeneous canopies for remote sensing applications [12]. Reviews of in situ non-spectral methods pertaining to crops and rangelands can be found in [13][14][15]. These techniques involve: visual assessment (e.g., [16]), crop height (H) (e.g., [17]), fraction of absorbed photosynthetically active radiation (FAPAR) derived from a ceptometer, fraction of vegetation cover (FVC) derived from red-green-blue (RGB) band photographs (e.g., [18]), electronic capacitance probes (e.g., [19]), weighted discs (e.g., [20]) or pendulum sensors (e.g., [21]).…”

Calibration of a capacitance probe for measurement and mapping of dry matter yield in Mediterranean pastures

“…Systematic manual plant sampling has been used to analyse spatial distribution of dry matter yield and plant nutrient concentration and to predict its variability on grassland (Bailey et al 2001). This method requires great effort and expense to collect enough samples to accurately represent a pasture (Sharrow 1984;Hanna et al 1999;Ganguli et al 2000). Similar problems occur during the evaluation of large-size pasture yields, which require a high number of destructive samples to obtain sufficient accuracy of the estimate (Franca et al 2003).…”