Soil Impedance and Field Emergence in Calabrese

Abstract

Calabrese seeds were sown in the field on four occasions and seeded rows were subjected to combinations of compaction and watering treatments. Plots were protected from natural rainfall. Soil crust strength (peak force needed to break through the crust) and integral impedance (work done in penetrating the soil to 15 mm depth) were obtained from penetrometer traces. For watered plots there were high negative correlations between percentage emergence and both peak force and integral impedance. There was also a high negative correlation between percentage emergence and integral impedance in non-watered plots when the penetrometer traces did not yield patterns giving distinct peak forces. No significant difference was found in the relationship of percentage emergence and integral impedance between watered and non-watered plots. Simple multiple regression models involving soil surface moisture content, level of compaction and watering amount explained over 90% of the variation in seedling emergence and integral impedance. Increased soil strength was also found to delay seedling emergence and to decrease the uniformity of seedling emergence and subsequent growth.