Both tillage and fertilizer management influence soil organic C (SOC) storage, but their interactive effects remain to be determined for various soil and climatic conditions. We evaluated the long‐term effects of tillage (no‐till, NT, and moldboard plowing, MP), and N and P fertilization on SOC stocks and concentrations in profiles of a clay loam soil (clayey, mixed, mesic Typic Humaquept). Corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] were grown in a yearly rotation for 14 yr. Our results showed that NT enhanced the SOC content in the soil surface layer, but MP resulted in greater SOC content near the bottom of the plow layer. When the entire soil profile (0–60 cm) was considered, both effects compensated each other, which resulted in statistically equivalent SOC stocks for both tillage practices. Nitrogen and P fertilization with MP increased the estimated crop C inputs to the soil but did not significantly influence SOC stocks in the whole soil profile. At the 0‐ to 20‐cm depth, however, lower C stocks were measured in the plowed soil with the highest N fertilizer level than in any other treatment, which was probably caused by a greater decomposition of crop residues and soil organic matter. Conversely, the highest SOC stocks of the 0‐ to 20‐cm soil layer were observed in the NT treatment with the highest N rates, reflecting a greater residue accumulation at the soil surface. When accounting for the whole soil profile, the variations in surface SOC due to tillage and fertilizer interactions were masked by tillage‐induced differences in the 20‐ to 30‐cm soil layer.
Soybean [Glycine max (L.) Merr.] is an important source of tocopherols which have health‐beneficial properties. A study was conducted to determine tocopherols concentration and stability in early maturing soybean genotypes and to determine their relationships to other important seed characteristics. Twenty soybean genotypes were grown in replicated trials in six environments of eastern Canada, and their total‐, α‐, γ‐, and δ‐tocopherol concentrations were determined by high‐performance liquid chromatography. Seed yield, 100‐seed weight, and crude protein and oil concentrations were concurrently determined. Genotype and environment main effects and G × E interactions were observed for all tocopherols. Variations in the ranking of genotypes were, however, limited. Across environments and genotypes, relative proportions of α‐, δ‐, and γ‐tocopherol were 6, 34, and 60%, respectively. Variation in α‐tocopherol among genotypes was significant, with concentrations ranging between 8.7 and 33.2 μg g−1 across environments. Differences between environments were significant, albeit minimal, for all tocopherols; there was a 42% average variation in α‐tocopherol concentration across environments. Stability of genotypes for α‐tocopherol was not linked to mean concentration; however, some genotypes with high stability and mean concentration were identified, including the cultivar Heron. No correlations were observed between α‐tocopherol and any of the other seed characteristics investigated. However, negative correlations were observed between the other tocopherols and seed yield, 100‐seed weight, and crude protein. Tocopherols were positively correlated with each other, except for a negative correlation between α‐ and δ‐tocopherol. The large variation observed among genotypes for α‐tocopherol, the relatively high stability of genotypes performance across environments, and the lack of negative correlation with other important seed characteristics suggest that selection for high α‐tocopherol could be possible.
Agricultural soil pests, including wireworms (Coleoptera: Elateridae), are managed primarily with pesticides applied directly to seeds before sowing. Seeds coated with neonicotinoids have been used widely in Quebec (Canada) for several years. To assess the agronomic and economic value of neonicotinoid seed treatments in soybeans and corn in Quebec, trials were conducted from 2012 to 2016 in 84 fields across seven regions in Quebec. We evaluated the effect of neonicotinoid seed treatments on soil pest densities, crop damage and yield. The results showed that 92.6% of corn fields and 69.0% of soybean fields had less than 1 wireworm per bait trap. However, no significant differences in plant stand or yield were observed between treated and untreated corn or soybeans during the study. This study shows that neonicotinoid seed treatments in field crops in Quebec are useful in less than 5% of cases, given the very low level of pest-associated pressure and damage, and that they should not be used prophylactically. Integrated pest management (IPM) strategies need to be developed for soil insect pests to offer effective alternative solutions to producers.
Soybeans are an important source of tocopherols, which have health-beneficial properties. Previous studies have demonstrated that environmental factors may affect soybean tocopherol concentrations; the impact of specific crop management strategies, however, remains poorly understood. Experiments were conducted for 2 years at three sites in Quebec to determine the impact on soybean tocopherol concentrations of seeding rate, row spacing, seeding date, cultivar, and P and K fertilization. Total and alpha-, gamma-, and delta-tocopherol concentrations were determined by high-performance liquid chromatography. Overall, alpha-tocopherol was the most responsive to the factors evaluated; the response of other tocopherols was often lower or inconsistent across environments. The seeding rate affected alpha-tocopherol concentrations in three out of five environments; seeding at a rate of 40 seeds m(-2) resulted in 4% higher concentrations than seeding at a higher rate. Wide row spacing (more than 36 cm) resulted in two out of five environments in 6% higher alpha-tocopherol concentrations as compared to narrower row spacing. The seeding date had a greater impact; mid- to late-May seeding across four environments resulted in 45% greater alpha-tocopherol concentrations than seeding at later dates. Phosphorus and K fertilization had a negligible impact on tocopherol concentrations. Across experiments, large differences were observed between environments; plants grown in northern environments consistently had lower concentrations of alpha- and gamma-tocopherols but higher concentrations of delta-tocopherol. Differences between cultivars were also consistent, ranging between 10 and 30%, depending on the tocopherol. Results demonstrate that soybean tocopherol concentrations are affected by crop management and thus suggest that specific recommended agronomic practices may need to be established for the production of soybeans for the functional food market.
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