Global Maize Initiative, Colombia

After three years of activities in the Valle del Cauca in Southern Colombia, the global maize (GM) project was relocated to the Meta Department in Eastern Colombia. The Meta Department is part of a large expanse of semi-arid savannas (the Llanos) with important areas planted to soybean and corn rotations under no-till management. An important trait of Llanos is the seasonal drought that normally occurs from November to February. The soils at the new site are sandy Ultisols with pH 6, very low available P (1.2 ppm Bray II), very low K (0.06 cmol/kg), but relatively high Mg (1.6 cmol/kg). Total Cation Exchange Capacity (CEC) of the experimental soil is only 5.1 cmol/kg, but soils in the experimental region do not suffer from aluminum (Al) toxicity, which is a serious issue in neighboring areas. The first phase of GM-Colombia was arranged as a single crop experiment with different N management scenarios. Using the experience of the GM sites in Brazil as our guidance, in the second phase we introduced either regular managed corn ("Farmer Practice" FP) or Eco-intensified corn (EI) as part of several rotation systems with soybean, rice or Crotalaria (Sunn hemp) as alternatives to increase the accumulation of residues. We organized a split-plot experiment with crop rotations as the main plot (six levels) and three N application rates within the corn as sub-plots. Three replicates of the main plots were used for a total of 54 plots. The experiment is arranged to have a clear comparison of FP management (i.e., soybean-corn or corn-corn rotations with conventional fertilization of maize receiving 60 kg P₂O₅ and 80 kg K₂O/ha plus micronutrients) with EI corn management (i.e., soybean-corn; corn-soybean; or soybean-corn-sunhemp rotations with applications of 120 kg P₂O₅, 140 kg K₂O, 50 kg S and 1.5 kg B/ha in maize). The N application rates evaluated for corn in both FP and EI in the first year were 42, 146, or 250 kg N/ha.

In both 2013 and 2014, the dry season was longer than usual. In 2013, the first crop was planted only in April 2013, with one FP corn and one EI corn, plus other crops in rotations, where necessary. The second planting took place in August 2013 with two EI corn and two FP corn treatments. Overall, the grain yields with the lowest rates of N in both FP and EI corn treatments were significantly lower than yields in plots receiving the mid and high N rates. The low N treatments had maize yields of 2.5 t grain/ha, while the highest yield was obtained with the highest N application rate (250 kg N) at 10.2 t grain/ha.