Annual productivity of cropping sequences: Responses to increased intensification levels

Abstract

Annual productivity of croplands can be increased by intensifying cropping sequences and fine-tuning agronomic management, improving the ratio between seasonal grain yield and annual available resources. The aims of this study were to evaluate, for different crop sequences and agronomic practices, (i) grain yield (GY), and energy of GY (EY) on annual basis; (ii) the relative contribution of each crop to the annual GY and EY of the crop sequences; and (iii) the maximum attainable annual EY. In a five-year field experiment at the central Rolling Pampa of Argentina, three crop sequences: soybean mono-cropping (Sy), a two-year rotation alternating maize and soybean (Mz-Sy), and a three-year rotation including wheat/soybean, maize, and soybean (Wt/Sy-Mz-Sy) were evaluated under the presence of either fallow (F) or cover crops (CC) during winter, and under two agronomic systems: conventional (CM) and intensified management (IM). For EY, Mz-Sy and Wt/Sy-Mz-Sy sequences greatly surpassed (P < 0.01) Sy (78% and 86% higher) across all years. The CC negatively affected (P < 0.001) the annual GY of the sequences by mostly affecting maize GY (−14% than under F), but this effect varied with the experimental year (rainfall levels) and CC composition (grass/legume proportion). The annual GY of the Mz-Sy (6.47 Mg ha−1) and Wt/Sy-Mz-Sy (6.69 Mg ha−1) sequences increased (P < 0.001) in the IM system compared to CM (5.33 and 5.64 Mg ha−1). In addition, under IM the penalty of CC on the annual GY of the crop sequences was lower (−7%) than under CM (−14%). From the combination of crop sequences and agronomic systems, the highest annual EY corresponded to the more intensified Wt/Sy-Mz-Sy sequence under IM (176 GJ ha−1), doubling the lowest EY obtained by soybean mono-cropping under CM (87 GJ ha−1). This result highlights the opportunity for intensification of cropping sequence and agronomic management to increase the annual productivity of the existing cropping area.