Is mineral nutrient concentration of soybean, maize, and wheat grain affected by cropping sequence and agronomic management?

Abstract

Producers in the Argentine Pampas often fail to fully replenish the nutrients extracted by crops, leading to unsustainable soil fertility management. The objectives of this study were to (i) evaluate grain yield, mineral nutrient concentration, and extraction for maize (Zea mays L.), wheat (Triticum aestivum L.), and soybean (Glycine max L. Merr.) under contrasting agronomic management systems and (ii) compare mineral nutrient concentration with nutrient removal values commonly used as reference in Argentina when assessing crop nutrient soil uptake. The study was conducted over 8 years in a field experiment located in the central Rolling Pampas, under three crop sequences: continuous soybean (Sy), a 2-year rotation alternating maize and soybean (Mz–Sy), and a 3-year rotation including wheat/soybean double crop, maize, and soybean (Wt/SyDC–Mz–Sy). In addition, these were evaluated with either fallow or winter cover crops (CCs) present under two agronomic systems: conventional management (CM) and intensified management (IM). The IM system included different genotypes, plant densities, fertilizer types, and rates. The IM increased yield for Mz by 1.25 Mg ha−1 (p < 0.01), Wt by 0.82 Mg ha−1 (p < 0.05), Sy1 (soybean full season crop) by 0.28 Mg ha−1 (p < 0.05), and SyDC by 0.39 Mg ha−1 (p < 0.05). The inclusion of a CC decreased yield for Mz by 1.20 Mg ha−1 (p < 0.01) and Sy1 by 0.34 Mg ha−1 (p < 0.05), only within CM and in the drier years. The IM increased nitrogen (N) and sulfur (S) concentrations for Sy but had no consistent effects on nutrient concentrations in other crops. Observed grain nutrient concentration values, despite their variability, could be used to estimate nutrient exports by these crops.