IS THE EFFECT OF SOWING DEPTH ON EMERGENCE AND EARLY SEEDLING DEVELOPMENT SIMILAR IN AFRICAN INDIGENOUS AND EXOTIC LEAFY VEGETABLES?
Both amaranth and Cleome are indigenous leafy vegetables that are gaining popularity among rural households of the semi-arid areas of South Africa. Although vegetable seedlings are best raised in trays, many small-scale farmers opt to sow directly into a seedbed. Depth of sowing can affect early crop establishment due to poor seedling emergence. This study investigated the effects of sowing depths (1.5, 3.5, 7, 10, 15, 20, 25, 30 mm) on seedling emergence and development of two each of indigenous (Amaranthus hybridus and Cleome gynandra) and exotic (Spinacae oleracia and Brassica hapus) leafy vegetables. The ANOVA showed highly significant interactive effects of sowing depth and vegetable species. Exotic vegetables had significantly higher (P<0.05) seedling emergence (95%) than indigenous ones (63%). Among the indigenous species, Cleome gynandra had a higher emergence (67%) than Amaranthus hybridus (61%). There were no significant differences on emergence amongst the exotic vegetables. Exotic vegetables also had significantly higher (P<0.05) average plant height (8.6 cm) than the indigenous vegetables (3.4 cm) after four weeks of growth. In all the species, both emergence and plant height decreased with deeper sowing. There were significant differences (P<0.05) among the biomass yields of the vegetable species at the different sowing depths. Generally, significantly higher biomass yield (6.4 g plant-1) was obtained in exotic vegetables compared with indigenous vegetables (2.2 g plant-1) after four weeks of growth. The significantly high correlation coefficient (r=0.79, p<0.05) between soil depth and penetrometer resistance implies that emerging seedlings experienced high soil resistance with deep sowing. The results suggest that indigenous vegetables were more sensitive than exotic ones to deeper sowing. It is concluded that seeds of indigenous vegetables should be sown at shallow depths (1-5 mm) in order to ensure rapid emergence and establishment of the seedlings.
Seeiso, T.M. and Materechera, S.A. (2013). IS THE EFFECT OF SOWING DEPTH ON EMERGENCE AND EARLY SEEDLING DEVELOPMENT SIMILAR IN AFRICAN INDIGENOUS AND EXOTIC LEAFY VEGETABLES?. Acta Hortic. 979, 703-711
crop establishment, soil strength, indigenous leafy vegetables, seedling emergence, household food security, small-scale farming