Fall rye reduced residual soil nitrate and dryland spring wheat grain yield
© 2017 Her Majesty the Queen in Right of Canada as represented by the Minister of Agriculture and Agri-FoodLimited information about how cover crop management impacts the agronomic performance of succeeding annual crops in semiarid regions constrains cover crop utilization. Therefore, over 2 yr we quantified how cover crop species (fall rye [Secale cereale L. ‘AC Remington’] or oilseed radish [Raphanus sativus L. ‘Tillage radish’]) and nutrient source (compost or inorganic fertilizer) affected cover crop biomass and N uptake, soil nitrate N (NO3 –N) and ammonium N (NH4 –N), and the agronomic performance of the succeeding spring wheat (Triticum aestivum L.) test crop. Fall rye reduced pre-plant NO3 –N by 2 to 18 times compared with oilseed radish, and reduced spring wheat grain yields by 38 to 58% compared with amended soils with no cover crop and oilseed radish. Inorganically fertilized soils led to 21% greater pre-plant soil NO3 –N concentrations than the compost-amended soil in 2013–2014 but nutrient source did not significantly affect NO3 –N concentrations in 2014–2015. A quadratic function explained 93% of the variability between pre-plant soil NH4 –N plus NO3 –N (0–7.5-cm depth) and spring wheat grain yield in 2014, indicating that the N supply limited spring wheat grain yield. We conclude that fall rye scavenged residual NO3 –N better than oilseed radish during the non-growing season, particularly during the spring period when this perennial species assimilates N, but under semiarid conditions it may decompose and mineralize too slowly to supply N at the right time for the subsequent crop, while oilseed radish tended to boost spring wheat grain yield.
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