Nitrogen and phosphorus uptake, yield and agronomic traits of oat cultivars as affected by fertilizer N rates under diverse environments

The majority of oat (Avena sativa L.) production in the developed countries is used as forage in the feed market. Oat groats are, however, being recognized as health-beneficial food and increasingly used for human consumptions. In addition to its high dietary water-soluble fibre β-glucan level, oat groats contain more than 20 unique polyphenols called avenanthramides, which have showed strong antioxidant, anti-inflammatory, anti-proliferative, and anti-itching properties. Despite of being a field crop well adapted to marginal lands with poor soils, low rainfall and cool temperature environments, nitrogen (N) fertilization strongly affects both oat yield and grain quality, and is mediated by soil moisture, indigenous soil nutrients and cultivar lodging susceptibility. There is still a lack of information on the responses of diverse oat genotypes to N supply under distinct environment conditions in Canada.

The overall objective of this study was to determine the agronomic and quality responses of promising, milling industry-preferred oat cultivars to N fertilizer application under diverse mega-environments across Canada. In this paper, our specific objectives were to (i) assess the impacts of fertilizer N rates on oat phenological development, grain yield and yield components, (ii) determine plant N and P uptake patterns under diverse soil-climate conditions, and (iii) examine the relationship between crop lodging and nutrient uptake.

Our study revealed that crop lodging was the key trait limiting oat grain yield response to N application. However, lodging was site- and cultivar-specific. Straw P content, stimulated by high N supply, was likely associated with crop lodging, and lodging occurred only when straw P was > 13.6 kg P ha-1. Severe lodging was not observed at Normandin and Melfort sites, which is probably attributed to the straw P contents found at these two sites, being much below the change-point. Limited plant P uptake under lower pH soils and cooler environments at Normandin, and great translocation of plant P into filling grain at Melfort, resulted in a smaller straw P content at harvest at these sites. We speculate that high straw P content may behave similarly as N in reducing the strength of stem base and anchorage system, thereby rendering crops like oat susceptible to lodging under high N supply. In addition, nutrient interaction is a complex issue, some other nutrient elements, such as K, may play an important role in stimulating crop lodging resistance. Taking multiple nutrients and their interaction and balances into considerations is beneficial in illustrating the mechanisms of lodging resistance in future studies.