The Rise of Superfoods Is Inevitable; Chia Agronomy.
Reports on agronomic management of chia are only just starting to appear in the scientific literature; most of them are based on experiments and observations conducted in the areas of origin of South and Central America and focus mainly on the response of different genotypes to growing environments in terms of phenology, yield, and quality of seeds (Ayerza and Coates 2009a, b; Ayerza 1995, 2010, 2011, 2013; Lobo Zavalia et al. 2011).
Chia prefers sandy, well-drained soils and with a pH of around 6 (Yeboah et al. 2014). According to some authors this crop has low salt tolerance, and salinity can significantly reduce the seed oil yield (Heuer et al. 2002). However, chia plants adapt well to soils belonging to other texture classes provided they have good drainage and are not too wet (Mu~noz et al. 2013; Lobo Zavalia et al. 2011; Baginsky et al. 2014). This crop is semi-tolerant to acid soils, drought and it is sensitive to frost (Mu~noz et al. 2013; Baginsky et al. 2014).
Furthermore, Chia is a drought-resistant crop, and it has been suggested as a choice for cropping systems in semi-arid environments (Ayerza and Coates 2009a, b). This plant can grow in arid environments, and it has been proposed as an alternative to existing forage crops (Peiretti and Gai 2009). Minimum and maximum growth temperatures of this crop are 11–36oC, with an optimum range between 16 and 26oC. It is well known that this plant is very sensitive to low temperature, and it cannot produce seeds since it is killed by frost before flowers set (Ayerza and Coates 2005). The duration of the crop cycle in most cases ranges from 140 to 180 days (de Kartzow 2013; Coates and Ayerza 1996), but being chia sensitive to day length, the growing cycle strictly depends on the latitude where it is planted as it relates to the heat unit accruable (Coates 2011).
While being able to grow in dry conditions (Baginsky et al. 2014), Salvia hispanica L. benefits from rainfall events ranging from 300 to 1,000 mm during the whole growing season (Yeboah et al. 2014; Coates and Ayerza 1996). The optimal distribution of precipitation for this crop allows a good supply of rainfall during the first phenological phases corresponding to vegetative growth, while drier conditions are required during subsequent phases, especially seed maturation (Yeboah et al. 2014). The crop can be grown in rain fed or irrigated conditions (Coates and Ayerza 1996).
Chia grows well in soils with a good amount of nutrients, while low soil nitrogen content seems to strongly reduce yield (Coates 2011). Coates and Ayerza 1996 reported amounts of nitrogen applied in field settings ranging from 21 to 45 units and Pozo Pozo (2010) reports amounts as high as 115 units. According to de Kartzow (2013), though, the recommended doses of N, P2O5, and K2O are 51, 43, and 60 units, respectively; applying 50 units of calcium sulphate is also advisable.
First results of research conducted in Basilicata, Southern Italy, has shown that after organic fertilization at sowing, nitrogen topdressing has not improved yield, in connection with a higher incidence of lodging (Bochicchio et al. 2015). Hence sole basal fertilisation is enough once done sufficiently because top dressing might favour unnecessary vegetative growth. Amato et al. (2015) also showed that mineral fertilization increased free acidity, chlorophyll, and carotenoids in seeds, whereas it reduced p-anisidine value, phenols, and oxidative stability. It also seemed to affect the amount of secondary metabolites in leaves.
As for many crops, the early stages of growing are critical times for weed competition; this is especially true for chia since no herbicide has been found to be fully satisfying for weed control so far. The critical control point is within the first 45 days because the pressure of weed is high at a time when the growth rate of chia is very low compared with common weeds. Poor control intercrop to weed competition and controlling weeds after the first 45 days not contribute to any yield improvements. Indeed Coates (2011) indicates that the first 45 days are very sensitive because the pressure of weed is high at a time when the growth rate of chia is very low compared with common weeds. After a good establishment of chia plants, it is possible to control weeds manually and mechanically until canopy closure (Coates 2011). There is an important need to investigate weed control in relation to plant density as highlighted in a study by Pozo Pozo (2010). In a pesticide trial conducted in Chile, Villegas et al. (2012) compared different herbicides and concluded that linuron showed the best behaviour in terms of weed control and conservation of chia. In another study metribuzin and haloxyfopmethyl-R were used to control weeds with good results (Pozo Pozo 2010).
Disease and Insect Control According to Pascual-Villalobos et al. (1997) chia leaves contain essential oils capable to carry a repellent action against insects and thanks to this characteristic Mu~noz et al. (2013) report previous observations that this crop can be grown without pesticides or other chemical compounds. Other authors, though, observed insect attacks in particular foliage beetles able to provoke a significant insect infestation of the plant (Yeboah et al. 2014). Moreover, in Southern Italy during the crop seasons 2013 and 2014 (data not shown), insect attack on leaves by whiteflies and aphids were observed. In a recent experimental trial (Yeboah et al. 2014) Fusarium wilt infection on chia has also been observed. Moreover, recently the presence of two viruses infecting chia plants was reported, and the infection was able to determine severe disease symptoms (Celli et al. 2014). Also, Celli et al. (2014) confirmed that the virus was transmitted by whiteflies, and this confirms the presence of species of Aleyrodidae family on this crop as was observed in our field trials in Southern Italy. Such reports of the occurrence of common diseases highlight the need to assess the appropriate control methods, including pesticides useful for the pests and pathogens identified on this crop.
Harvesting Salvia hispanica L. seeds are harvested mechanically. In low input conditions, average yield is around 600 kg ha-1 but can be up to 1,200 kg ha-1 (Coates 2011), while in high input conditions with irrigation and fertilization, yields as high as 2,500 kg ha-1 have been shown in some experimental trials in Argentina (Coates 2011). During harvest a great problem is the scalarity of flowering and maturation: the central flower head matures and dries out while inflorescences on side branches are still green. Waiting until all seeds are dry can increase the risk of seed loss to rain, wind, or birds (Jamboonsri 2010).
