Optimizing germination of seven Mediterranean crops

• Published in: Journal of crop improvement Vol. 34; no. 2; pp. 164 - 189
• Main Authors: Andrade, José A., Cadima, Jorge, Abreu, Francisco G.
• Format: Journal Article
• Language: English
• Published: Philadelphia Taylor & Francis 03-03-2020; Taylor & Francis Ltd
• Subjects: Broad beans; Chickpeas; Cicer arietinum; Crop production; Crops; Dispersion; Germination; Germination rate; germination size; Helianthus annuus; Lupinus luteus; optimal germination; Optimization; Pisum sativum; Polynomials; Seeds; Soil moisture; Soil temperature; Sorghum; Sorghum bicolor; spread of germination; Sunflowers; Temperature; thermal time; Thermocouples; Vicia faba; Zea mays
• ISSN: 1542-7528; 1542-7536
• DOI: 10.1080/15427528.2019.1679311

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. This work 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 faba L.), sunflower (Helianthus annuus L.), corn (Zea mays L.) and sorghum (Sorghum bicolor (L.) Moench). Experiments used a thermogradient plate, with temperatures monitored by Cu-CuNi thermocouples. Thermal ranges [T
o1
sz
, T
o2
sz
] along which germination counts are nearly maximized were identified by the successful use of a flattened bell curve function. Thermal ranges [T
o1
sp
, T
o2
sp
], where germination speed is maximized, were defined using the plateau-shaped model for rate of germination vs. temperature relationship. Ranges [T
o1
sd
, T
o2
sd
], 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 (OTR
G
) for the germination of each crop. In most cases, OTR
G
begins at the lowest temperature that guarantees a maximum germination rate (T
o1
sp
) and ends at the maximum temperature that ensures minimal dispersion (T
o2
sd
). The endpoints and length of the OTR
G
were found to be crop-dependent. For each crop, OTR
G
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.