Effects of soil and climatic conditions on emergence of grain amaranths

Amaranth is a pseudocereal of potential economic interest in Europe, but due to its small seed size it requires shallow sowing and maintenance of optimal soil surface conditions for sufficient and uniform emergence. In this study, two experiments in a glasshouse, and two in a growth chamber were conducted to determine the effect of various factors on percentage of live seed emergence (PLSE) and seedling weight of four amaranth species: Amaranthus mantegazzianus Paserini, A. hypocondriacus L. cv. G5, A. cruentus L. cv. G6 and A. caudatus L. Emergence factors included soil texture (loam, silt loam, sandy loam and sand), sowing depth (0, 5, 15, 30 and 45 mm), soil water regimes (water potentials of -10 to -20, -40 to -50 and -60 to -70 kPa), temperature (from 11 to 25degreesC in 2degreesC increments) and light regimes (photoperiod 0, 12 and 24 h). The 15 mm sowing depth gave the highest seedling weight on sand and the highest PLSE on loam. On the sandy loam the PLSE was not affected by sowing depth up to 15 mm. A. caudatus gave the highest PLSE whereas A. cruentus gave the lowest PLSE but the heaviest seedlings. PLSE was severely reduced on the loam where topsoil crusting occurred after a decrease in soil moisture content from field capacity to -60 to -70 kPa, but not on the silt loam even when dry conditions were maintained throughout the experiment. PLSE was above 80% with temperatures > 21 degreesC. Light regime with 12 It illumination gave the highest PLSE. (C) 2002 Elsevier Science B.V. All rights reserved.