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Fluid Journal : Spring 2016
10 The Fluid Journal Spring 2016 S, and K supply as close as possible rates compatible with removal quantities, while keeping the costs at reasonable levels with expected profitability. Nutrients. Tables 6 and 7 show the average nutrient removal in each site, assuming the concentrations in grain indicated by Heckman et al. (2003) and the actual yields of the experiments, averaging the three seasons in each location. At Pergamino, only higher rates showed positive balances for P, as indicated by applied/removal rates over 100%, while in Mercedes only lower rates had negative balances for this nutrient. This site received noticeably lower rates than required in potassium and would indicate the need to modify the ratios to supply something less in P and higher in the K starter. However, given the small differences between treatments, relative yields (less than 10%), the cost of the nutrients, and the proximity to a positive balance would indicate the most convenient grade and rate to recommend and use for corn production. Summing up There was a significant response to starter fertilization in five of six experiments as indicated by the contrast between the check and the fertilized treatment. Fluid sources were not different from granular at the same rate and P:N ratio The P:N ratio 1:1 performed better than 1:1.5 only in the Mercedes site, indicating the need of less N compared to P. In the Pergamino site the treatment effect was reverse, since the 1:1.5 ratio was better than 1:1, thus showing more N need than P, regardless of the rate. Only in one trial in Mercedes was the Figure 2. Treatment means of grain yields of corn affected by the different base fertilizer at planting across locations and years. (P2O5 is shown as P). Pergamino 2011-12 Pergamino 2012-13 Pergamino 2013-14 Mercedes 2011-12 Mercedes 2012-13 Mercedes 2013-14