Development and utility of a lab-based, field relevant methodology to evaluate crop emergence in restrictive soils

Abstract

Abstract Aims Improving crop emergence is a particular challenge in small-seeded species such as canola ( Brassica napus L.), where establishing a uniform and viable plant stand remains a challenge under field conditions. This study developed and tested a simple, high-throughput screening protocol under controlled environmental conditions to identify critical thresholds to seedling emergence in field soils. Methods Soil water retention curves and early canola development responses to soil water potential were assessed prior to developing a tube-based system in which soil conditions could be manipulated. The system was tested by assessing the response of canola seedling emergence to soil strength (0–5.5 kg/cm 2 ) above the seed and sowing depth (2, 5, 10 cm) across different soils using the variety ‘Regiment XT’. Reduced strength x depth treatments derived from this were then used to screen the emergence of novel genotypes (long- and short hypocotyl). Results The non-limiting water threshold for maximum germination and cotyledon emergence across soil types was -250 kPa. Critical soil strength values, 4.8 kg/cm 2 in sand, and 2.5 kg/cm 2 in a loam were established at a 2 cm sowing depth but declined in both soils to < 1 kg/cm 2 as depth increased below 5 cm. The methodology confirmed previously established differences in emergence between long- and short hypocotyl canola varieties. Conclusions A controlled-environment, tube-based system in which several soil, environmental, management and genetic variables were manipulated to establish critical thresholds for canola emergence was effective for studying factors influencing seedling emergence, and providing a field-relevant rapid screening methodology.