Expansion of maize production in a semi-arid region of Argentina: Climatic and edaphic constraints and their implications on crop management

The Southwestern Pampas (SWP) is a semi-arid region of Argentina with the presence of a widespread caliche layer that limits soil depth. In this region, maize production has recently expanded with scarce information on appropriate management practices. The objective of this work was to provide an agro-climatic and eco-physiological framework of cultural changes of maize cropping systems of the SWP and the main implications of the climatic and edaphic constraints on crop management decisions. The work combined i) public data of regional maize cultivated area for the period 2008-2015 alongside with farmers' cropping management trends related to sowing dates and plant population density (PPD); ii) on-field experimental data generated from trials in different sites in the SWP sown at different dates, soil depths and PPDs; and iii) a crop water-economy characterization with a probabilistic approach by means of historical climatic series (identifying the El Nino Southern Oscillation (ENSO) phases) in three locations in the SWP across a longitudinal range between the 800 mm and 600 mm isohyets. In the 2008-2015 period, maize area increased five-fold, median sowing date delayed one month and PPD decreased from ca. 7.2 pl m(-2) to 3.4 pl m(-2). Late-sown crops (7564 kg ha(-1); CV = 19%) out-yielded earlysown crops (5888 kg ha(-1); CV = 42%) with less variability across environments. Crop evapotranspiration during the cycle (ETacycle) slightly decreased (P50 = 3-32 mm lower) with the delay of sowing, but the proportion of crop evapotranspiration during the reproductive period was significantly higher. ETacycie of late crops did not vary within PPD, but transpiration per plant decreased with PPD and increased in deep soils, especially at low densities. The impacts of sowing date and PPD did not vary among ENSO phases, not supporting the use of ENSO as a decision criterion for maize management in the SWP.