Development of reflectance-based crop coefficients for corn
Christopher, MUN; Walter, CB; Dale, FH
| HERO ID | 10287468 |
|---|---|
| In Press | No |
| Year | 1990 |
| Title | Development of reflectance-based crop coefficients for corn |
| Authors | Christopher, MUN; Walter, CB; Dale, FH |
| Journal | Transactions of the ASAE |
| Volume | 32 |
| Issue | 6 |
| Page Numbers | 1891-1899 |
| Abstract | Concurrent measurements of reflected canopy radia-tion and the basal crop coefficient (K^b) for corn were conducted throughout a season in order to develop a reflectance-based crop coefficient model. Reflectance was measured in Landsat Thematic Mapper bands TM3 (0.63 - 0.69 um) and TM4 (0.76 - 0.90 um) and used in the calculation of a vegetation index called the normalized difference (ND). A linear transformation of the ND was used as the reflectance-based crop coefficient (Kcr). The transformation equates the ND for dry bare soil and the ND at effective cover, to the basal crop coefficient for dry soil evaporation and at effective cover, respectively. Basal crop coefficient values for com were obtained from daily evapotranspiration measurements of corn and alfalfa, using hydraulic weighing lysimeters. The Richards growth curve function was fitted to both sets of data. The K^b values were determined to be within -2.6% and 4.7% of the K^^ values. The date of effective cover obtained from the K^b data was within four days of the date on which the ND curve reached its maxima according to the Richards function. A comparison of the Kcr with basal crop curves from the literature for several years of data indicated good agreement. Reflectance-based crop coefficients are sensitive to periods of slow and fast growth induced by weather conditions, resulting in a real time coefficient, independent from the traditional time base parameters based on the day of planting and effective cover. |
| Doi | 10.13031/2013.31240 |
| Wosid | WOS:A1989CR28800011 |
| Is Certified Translation | No |
| Dupe Override | No |
| Is Public | Yes |
| Language Text | English |