Early drought may affect germination and early growth. Water stressed seedlings are more severely affected by other constraints and frequently have induced nutrient deficiencies.
What to look for
Paddock
Patchy germination and/or discoloured stressed young plants
Induced nutrient deficiency of soil-immobile nutrients that become unavailable to the plant when the topsoil is dry. Phosphorus, copper, zinc and manganese deficiency is most common. These deficiencies disappear when rainfall rewets the topsoil.
Plant
Dull-coloured or discoloured, shorter, stunted or spindly plants.
Older leaf yellowing (wheat, barley) or reddening (oats) then death that starts at the leaf tip.
Furled young leaves, wilting and death.
Where does it occur?
Seedling water stress is more likely to occur with very early seeding followed by dry weather, or dry seeding.
Very low water holding soils, such as coarse sands and gravels, very shallow soil over rock or impermeable layer.
Heavy clays that retain moisture near the soil surface, where it is more likely to be lost by evaporation in light, patchy rainfall seasons.
Soils with higher salt content such as morrel loams.
Water repellent soils.
Stubble retained areas combined with light rain events where the stubble acts as a thatch rather than a mulch.
Management strategies
No treatment. Applied nutrients have no effect.
How can it be monitored?
Unless the problem is obviously due to drought, dig a hole and examine the soil profile for:
