Emergence of Medicago tribuloides on moderately acid soils

Abstract

Field establishment of Medicago tribuloides Desr. on moderately acid, light textured soils varied from 98% to less than 10% of untreated viable seeds sown.

Seed and seedling mortality occurred mainly in the pre-emergence stage. Where emergence was poor, under conditions of low temperature or high soil moisture, or both, considerable improvement resulted from using a seed fungicide or a soil fumigant, or coating seeds with alkaline inorganic materials, of which calcium carbonate was the most effective. Under adverse conditions of temperature and rainfall, improved emergence occurred at higher soil pH values.

The results indicate that pathogenic soil organisms caused pre-emergence seed and seedling mortality, and that temperature, rainfall, soil pH, and seed coating (through its pH effect) influenced pathogen activity or the susceptibility of the seedling to pathogenic attack.