Early season root growth, soil aggregation and stratification of nutrients and soil properties after six annual treatments of fertilizer rates and seeding systems

Abstract

Fertilizer application and tillage practices have been found to influence root growth and soil properties. The objectives of the current study were to assess the response of early season root growth of canola (Brassica napus L.) and barley (Hordeum vulgare L.), aggregates stability in the 0–7.5 cm of soil, and nutrient concentrations and soil properties in the 0–7.5, 7.5–15.0, 15.0–22.5 and 22.5–30.0 cm soil, to 6 years of different soil test-based fertilizer rates and seeding systems. Before these assessments, soil test-based fertilizer rates (0, 60, 100 and 140%) and seeding systems (direct seeding, DS; and minimum tillage, MT) had been used for six years (2010–2015) to grow crops on a clay loam soil in the southeast Peace Region (legal: NW7-77-20W5; GPS: 55°39′38.43″N, 117°6′10.64″W) of Alberta, Canada. The length, surface area, volume and number of tips for canola and barley roots in the early growing season (from May 11 to June 17) of 2015 were greater with the 100% than the 0% fertilizer rate. They also tended to be greater under the DS than MT system. The length, surface area and volume of roots were greater for barley than canola, while the number of tips for both crops were in a similar range. The stability of soil aggregate (after the 2015 growing season) showed positive effects of fertilizer application and reduced tillage intensity. Soil samples collected in the spring 2016 indicated increased stratification of some nutrients and soil properties from higher fertilizer rates. These trends were more evident under the DS than the MT seeding system. Organic matter content and P concentration declined with depth, while pH, Ca and Mg increased with depth, and the change with depth tended to be greater at the 100% than 0% fertilizer rate. No change in stratification of NO3-N and SO4-S was noticed as a result of fertilizer rates. Overall, 6 years of different fertilizer rates and tillage systems influenced the early season growth of canola and barley roots, the soil aggregates stability and the stratification of some nutrients and soil properties.