Study of the seed bank of Echinochloa crus-galli (L.) Beauv. in the soil of rice fields in Gharb (Morocco).
Estimates of numbers of viable caryopses of E. crus-galli were made on soil samples taken from 26 rice fields in Gharb, chosen according to soil type, rotation and number of yr under rice. On av. there were 1285 caryopses/m2 in the top 60 cm of soil, comprising 7.2% of the total seed bank. The effects of soil type in a rotation of 3 rice crops and 3 other crops and of rotation (3 rice crops/3 other crops or 3 rice crops/ 1 other crop) on merja soil were analysed. 85, 12.5 and 2.5% of the E. crus-galli caryopses were in the 0-20, 20-40 and 40-60 cm soil horizons. Field emergence from harvest to sowing of the following crop represented 0.65% of the seed bank.