Agronomic and economic performance of 26‐year corn–soybean rotation affected by tillage and fertilization in eastern Canada

Abstract

Adoption of conservation practices such as no‐tillage (NT) may benefit soil properties and related yields. However, magnitude of changes is dependent upon time scale, soil characteristics, and climatic conditions, which has received little attention in eastern Canada. A 26‐yr field experiment was conducted on a clay loam soil at L'Acadie, southwestern Quebec, to evaluate the effect of NT vs. moldboard plow (MP) and mineral N (0, 80, and 160 kg N ha–1) and P (0, 17.5, and 35 kg P ha–1) fertilization on grain yields, soil properties, and annual net returns of a corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotation. Tillage was performed every year, while fertilizers were only applied to the corn phase. Throughout the years, the site responded well to N fertilization but not consistently to P. Tillage system did not affect corn grain yield in the first 10 yr, but yield gradually declined under NT and produced 2.3 Mg ha–1 less than MP with recommended N rate in the last 8 yr. By contrast, NT reduced soybean yield in the first decade (0.32 Mg ha−1) but not thereafter. After 24 yr of implementation, NT largely increased organic matter and Mehlich‐3 P and K in the 0‐to‐5‐cm surface layer, but this did not translate into higher yields. Compared with NT, MP achieved CAN$200 ha–1 more revenue during last years at recommended N rate despite higher operation costs. Results demonstrated that under northern latitudes, this clay soil was not appropriate for NT.

Weed communities after decades of mineral fertilization and tillage treatments in a corn–soybean rotation

“…Further analyses of the 2016 data indicate that the fertilization effect on corn yield is due to the higher nitrate rates, while phosphorus rates had no effect on corn yield (data not presented), as observed by Légère et al (2008) and Ziadi et al (2014) in the same plots. In a recent study, Gagnon et al (2022) also reported a significant and consistent effect of nitrogen fertilization on corn yield over a 26-yr corn–soybean rotation, whereas the effect of phosphorus fertilization was inconsistent. The lowest corn yields were observed in unfertilized weedy plots, and adding fertilization increased yields to levels close to those observed in plots where weeds were controlled (Figure 5), implying competition for nutrients by weeds.…”