Caryopsis Weight and Planting Depth of Blue Grama. II. Emergence in Marginal Soil Moisture

Abstract

Blue grama [Bouteloua gracilis (H.B.K.) Lag. ex Steud.] has not been able to establish itself, or to be successfully planted, from seed on abandoned croplands of the Central Plains. The objectives of this study were to test blue grama plant material under limited moisture and develop methods for improving emergence and establishment of blue grama seedlings. Experiments were conducted in the greenhouse and at the Central Plains Experimental Range near Nunn, Colorado, with 3 accessions. Under limited moisture conditions in the greenhouse, seedlings emerged better from planting depths of 2.0 and 2.5 cm than from depths of 0.5, 1.0 or 1.5 cm. Higher caryopsis weight was associated with a significant increase in percentage emergence at all planting depths. Accession PM-K-1483 had greatest emergence, followed by 'Hachita' and 'Lovington'. Under favorable soil moisture conditions in the field (2 cm of water applied at planting dates in June and July 1981), deep planting resulted in decreased emergence. Averaged over all planting depths, percentage emergence increased nearly 2-fold with an increase in caryopsis weight from 39 to 59 mg/100. When soil moisture conditions were marginal (only 1 cm water added), satisfactory emergence was obtained only when high-weight seeds were planted at a depth of 2 cm. Soil at a planting depth of 1 cm dried quickly and prevented emergence. Genetic improvement of caryopsis weight combined with planting at depths of about 2.0 cm should improve the emergence and establishment of blue grama seedlings.