Digital Commons Network^™

Meteorological Models For Estimating Phenology Of Corn, C. S. T. Daughtry, J. C. Cochran, S. E. Hollinger

LARS Technical Reports

Knowledge of when critical crop stages occur and how the environment affects them should provide useful information for crop management decisions and crop production models. This research evaluated two sources of data for predicting dates of silking and physiological maturity of corn (Zea mays L.). Initial evaluations were conducted using data of an adapted corn hybrid grown on a Typic Agriaquoll at the Purdue University Agronomy Farm from 1979 to 1981. The second phase extended the analyses to large areas using data acquired by the Statistical Reporting Service of USDA for crop reporting districts (CRD) in Indiana and Iowa from …

Costs Of Measuring Leaf Area Index Of Corn, C. S. T. Daughtry, S. E. Hollinger

LARS Technical Reports

Leaf area index (LAI) is an important biophysical descriptor of crop canopies. Accurate measurements of LAI are laborious and time-consuming. Many methods of measuring LAI of corn (Zea mays L.) have been reported and vary greatly in their accuracy, precision, bias, and ease of measurement. We examined the magnitude of plant-to-plant variability of leaf area of corn plants selected from uniform plots and evaluated four representative methods for measuring LAI. The number of plants required and the relative costs for each sampling method were calculated to detect 10, 20, and 50% differences in LAI using 0.05 and 0.01 tests of …

Estimation Of Modulation Transfer Function Of Landsat-4 Sensors From Measured Imagery, C. D. Mcgillem, P. E. Anuta, K. B. Yu

LARS Technical Reports

Satellite-based multispectral imaging systems have been in operation since 1972 and the latest in the Landsat series of sensors was launched in July 1982. In order to verify that the Landsat-4 Thematic Mapper (TM) and Multispectral Scanner Systems (MSS) sensors are operating within specifications, it is necessary to estimate the system parameters by analysis of the measured data. One parameter of interest is the sensor modulation transfer function (MTF) or the point spread function (PSF) which determines the spatial resolution of the system.

This paper discusses two methods to determine the actual overall resolutions after launch. The problem is formulated …

Changes In Spectral Properties Of Detached Leaves, C. S. T. Daughtry, L. L. Biehl

LARS Technical Reports

A leaf begins to senesce as soon as it is removed from the plant and changes in metabolic processes and spectral properties are inevitable. If senescence can be delayed for several days without significant changes in spectral properties, then samples of leaves at remote test sites could be prepared and shipped to laboratories which have the equipment to measure spectral properties. The objective of this study was to determine the changes in spectral properties of detached leaves. Leaves from red birch (Betula nigra L.) and red pine (Pinus resinosa Ait.) were immersed for 5 minutes in water or 0.001 M …

Spectral Estimators Of Absorbed Photosynthetically Active Radiation In Corn Canopies, K. P. Gallo, C. S. T. Daughtry, M. E. Bauer

LARS Technical Reports

Most models of crop growth and yield require an estimate of canopy leaf area index or absorption of radiation; however, direct measurement of LAI or light absorption can be tedious and time consuming. The objective of this study was to develop relationships between photosynthetically active radiation (PAR) absorbed by corn (Zea mays L.) canopies and the spectral reflectance of the canopies. Absorption of PAR was measured near solar noon in corn canopies planted in a field experiment conducted at the Purdue University Agronomy Farm, West Lafayette, IN, on a Typic Argiaquol at densities of 50,000 and 100,000 plants/ha. Reflectance factor …

Variation In Spectral Response Of Soybeans With Respect To Illumination, View And Canopy Geometry, K. J. Ranson, L. L. Biehl, M. E. Bauer

LARS Technical Reports

Comparisons of the spectral response for incomplete (well-defined row structure) and complete (overlapping row structure) canopies indicated a greater dependence on sun and view geometry for the incomplete canopies. This effect was more pronounced for the highly absorptive red (0.6--0.7µm) wavelength band than for the near-IR (0.8--1.1µm) based on relative reflectance factor changes.

Red and near-IR reflectance for the incomplete canopy decreased as solar zenith angle increased for a nadir view angle until the soil between the plant rows was completely shaded. Thereafter for increasing solar zenith angle, the red reflectance leveled off and the near-IR reflectance increased. A "hot …

Comparison Of Classification Schemes For Mss And Tm Data, P. E. Anuta, L. A. Bartolucci, D. F. Lozano-Garcia, J. A. Valdes, C. R. Valenzuela

LARS Technical Reports

The launch of the Landsat-4 satellite in July 1982 provided the first full coverage from space of the .4-12 µm spectrum of the earth scene. In addition to the green, red, and near IR bands of the MSS, the TM provides a band in the blue, two in the middle IR, and one thermal IR. The paper describes spectral class analysis of coincident MSS and TM data to evaluate the contribution of the additional TM bands. In addition, various classifiers are available which were applied to the TM data. In the spectral class analysis, twice the number of separable classes …

Spectral Estimates Of Agronomic Characteristics Of Crops, C. S. T. Daughtry, K. P. Gallo, L. L. Biehl, Blaine L. Blad, John M. Norman, Bronson R. Gardner, E. T. Kanemasu, G. Asrar

LARS Technical Reports

If agronomic variables related to vigor and yield of crops could be reliably estimated from multispectral data, then crop growth and yield models could be implemented for large areas. The objectives of these experiments were to determine relationships of key agronomic characteristics and spectral properties of crops and to integrate spectral and meteorological data for forecasting crop yields. Reflectance data of corn, wheat, and soybeans were acquired with radiometers that simulate Landsat MSS and TM sensors. The spectral indices, greenness, and normalized difference were highly correlated with leaf area index (LAI) and absorbed photosynthetically active radiation (APAR). Grain yields were …