Radiation interception, radiation-use efficiency and dry matter partitioning in garlic (Allium sativum L.)

Despite the importance of garlic (Allium sativum L.) among vegetable crops, very little information is currently available on the physiological determinants of crop growth and yield. The objective of this work was to determine the main components of a garlic crop model in terms of radiation interception, radiationuse efficiency (RUE) and dry matter (DM) partitioning. Experimental data (radiation interception, leaf area index (LAI) and biomass) were collected in two commercial crops of garlic grown in Cordoba (Spain) during 1999-2000. The parameters of an ellipsoidal leaf angle distribution were fitted to measured light transmissivity, showing a rather vertical leaf distribution with clumped distribution of foliage elements. A model of radiation interception was developed and validated with independent measurements. The model was then used to estimate the extinction coefficient of garlic, for diverse conditions of LAI and sun angle. Calculated RUE was around 2.9 g (MJ PAR)-1 for most of the growing season, but it was lower at the start and at the end, with whole-season average value around 2.0 g (MJ PAR)-1. Partitioning of DM showed four distinct phases with predominant growth of leaves, pseudostem, storage in leaves and bulbs. Harvest Index was around 0.55 due to the large clove growth rate, which was also supported by translocation of carbohydrates from storage organs.