Optimizing germination of seven Mediterranean crops

摘要

Crop establishment is a major factor determining crop productivity. Successful crop establishment requires generalized, fast and concentrated germination. Final germination counts (size), speed and spread depend on soil temperature and moisture. Thiswork seeks to determine, under non-limiting water conditions, optimal temperature ranges for the germination of seven common Mediterranean crops, viz., pea (Pisum sativum L), lupine (Lupinus luteus L), chickpea (Cicer arietinum L), broad bean (Vicia fabaL), sunflower (Helianthus annuus L), corn (lea mays L) and sorghum {Sorghum bicolor (Lj Moench). Experiments used a thermogradient plate, with temperatures monitored by Cu-CuNi thermocouples. Thermal ranges [To1sz, To25z] along which germination countsare nearly maximized were identified by the successful use of a flattened bell curve function. Thermal ranges IToisp- To2sp], where germination speed is maximized, were defined using the plateau-shaped model for rate of germination vs. temperature relationship. Ranges [Toisd- To2sd], along which dispersion is nearly minimized, were successfully identified using even-degree polynomials. The intersection of these three thermal ranges provided an optimal temperature range (OTRG) for the germination of eachcrop. In most cases, OTRG begins at the lowest temperature that guarantees a maximum germination rate (T0lsp) and ends at the maximum temperature that ensures minimal dispersion (To2sd). The endpoints and length of the OTRG were found to be crop-dependent. For each crop, OTRG also depended on the fraction of germinated seeds and on the level of dispersion that is considered acceptable. The results allow farmers to choose between different crops and to optimize their germinations.