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Development of a hemp (Cannabis sativa L.) simulation model 1.General introduction and the effect of temperature on the pre-emergent development of hemp

S. N. Lisson, N. J. Mendham and P. S. Carberry

Australian Journal of Experimental Agriculture 40(3) 405 - 411 Published: 2000

Abstract

In recent times, there has been a revival of interest in hemp (Cannabis sativa L.), principally as a source of fibre in paper and pulp manufacture. Studies assessing the production potential and optimum crop management of hemp could benefit from the use of a simulation model that captures crop growth and development processes in response to management, genotypic, soil and climate factors. Such a model would complement the more traditional agronomic field trial programs by helping to identify the need, extent and nature of such trials, and by extrapolating limited field results across both temporal and spatial dimensions.

The hemp model described in the final paper in this series, divides crop phenology into 5 phases, the first of which includes the pre-emergent processes of germination and the subsequent elongation of hypocotyl and radicle. This first paper reports on a study into the response of these pre-emergent processes to temperature. The primary objectives were to establish a simple model for predicting the duration from sowing to emergence and to obtain estimates for the cardinal temperatures of hemp growth and development. Cardinal temperatures are required for the estimation of thermal time, which drives phenological development and canopy expansion in the hemp model.

The germination response of the hemp cultivar Kompolti was measured at 13 different temperatures in incubators set between 1 and 55˚C. Similarly, the response of radicle and hypocotyl elongation to temperature was measured at 8 different temperatures in incubators set between 10 and 40˚C. Development rates for each phase of pre-emergent development were then calculated from time response plots of germinant number, hypocotyl and radicle length. Finally, piecewise linear models were fitted to plots of development rate versus temperature in order to calculate thermal time durations for each phase and cardinal temperatures for hemp growth and development. Estimates of the optimum and maximum temperatures from the elongation study were relatively consistent, with average values of 28.6 and 40.7˚C, respectively. Base temperature estimates were less consistent, ranging from 1.4˚C for the hypocotyl linear phase, to 6.2˚C for the radicle lag phase. This variability made it difficult to identify a common base temperature for use in the hemp model. However, there was some evidence to support previously reported base temperature estimates ranging from 0 to 2.5˚C. Assuming a common base temperature of 1˚C, the average thermal time requirements for germination and the lag and linear phases of hypocotyl elongation were 24.1˚Cd, 44.5˚Cd and 1.34˚Cd/mm, respectively.

Keywords: hemp, model, phenology, germination, radicle, hypocotyl, APSIM.

https://www.publish.csiro.au/an/EA99058

Development of a hemp (Cannabis sativa L.) simulation model 2.The flowering response of two hemp cultivars to photoperiod

S. N. Lisson, N. J. Mendham and P. S. Carberry

Australian Journal of Experimental Agriculture 40(3) 413 - 417 Published: 2000

Abstract

The duration from sowing to flowering is an important determinant of fibre yield potential in hemp, since maximum stem yield occurs shortly after flowering. As a short-day plant, daylength has a key influence on the timing of flowering in hemp. This paper reports on studies into the effect of photoperiod on the thermal time duration from sowing to flowering for 2 hemp cultivars, and develops parameters to enable simulation of post-emergent phenology in the hemp model described in the final paper of this series.

The hemp model divides the post-emergent period into a vegetative phase that ends at floral initiation, aflower development phase (FDP) between flower initiation and appearance, and a short phase between first flower appearance and harvest maturity (male anthesis). The vegetative phase is further divided into a temperature-dependent basic vegetative phase (BVP) and a daylength-dependent photoperiod induced phase (PIP). For a short-day plant, the duration of PIP is assumed to be zero degree days at daylengths below a base or maximum optimum photoperiod (MOP). Daylengths in excess of the MOP lead to an increase in thermal time within PIP, the duration of which is determined by a genotype’s photoperiod sensitivity (PS).

Two hemp genotypes, Kompolti and Futura 77, were exposed to 6 different photoperiod regimes ranging from 8 to 16 h in a growth chamber. Thermal time durations from emergence to flower initiation and first flower formation (harvest) were calculated from thermograph plots.

The flowering responses for the 2 cultivars were typical for a short-day plant, with flowering occurring rapidly in daylengths less than about 14 h and with increasing delay at longer photoperiods. With the exception of a longer thermal time duration from flower formation to harvest maturity in the case of Kompolti, the 2 cultivars had similar values for the key phenology parameters. Respectively, for Futura and Kompolti: BVP was 383˚Cd and 390˚Cd, MOP was 14 h and 13.8 h, PS was 266˚Cd/h and 252˚Cd/h, and FDP was 76.8˚Cd and 80.2˚Cd.

Keywords: hemp, model, phenology, flowering, photoperiod response.

Article Development of a hemp (Cannabis sativa L.) simulation model ...

To my knowledge it is not available in the current APSIM version. I'm developing a hemp model in DSSAT, if you have any data from field trials and are interested feel free to reach out [email protected]