EFFECT OF SOWING DEPTH ON SEEDLING EMERGENCE, GROWTH AND DEVELOPMENT IN BARLEY AND WHEAT

Crop prediction models often assume a 'standard' sowing depth but this may vary both between and within crops. This paper reports response of time of seedling emergence and plant development to sowing depth. Spring barley was sown at depths of 50, 100 or 200 mm in a glasshouse experiment and the growth of the coleoptile, elongating sub-crown internodes, leaves and roots were measured from germination until emergence of the fourth leaf. Winter wheat was sown in a continuous gradient of 0-150 mm in a sandy loam in the field. Seedling emergence and establishment were measured and emerged leaves were counted until flag leaf appearance. Lengths of the coleoptile, sub-crown internodes and leaves were measured and plant development was assessed. Time to wheat seedling emergence increased with increasing sowing depth and linear regression of thermal time to seedling emergence on depth of sowing accounted for 99% of the variation. Reported functions of response to sowing depth tended to underestimate time of seedling emergence. In both barley and wheat, length of elongating and primordial leaves was shorter when sown deeply. Final dry mass of the seminal root of barley, which was attained soon after emergence, was reduced by deep sowing. In barley, elongation of the sub-crown internodes was related to the elongation of the associated leaf, so that in deeply sown seedlings, adjustment of crown depth might continue until the third leaf is fully grown. Shoot apex stage and culm elongation of wheat were affected by depth of sowing. The depth at which seeds are sown, both between and within crops, may be a significant factor both in assessing crop development for crop management and for predicting crop stage.