Corn Response to Fertilization in Tropical Soil of Brazil.

This research aimed to evaluate the growth of corn plant at 62 days of age in tropical soil of Brazil and the efficiency of nutrient use as a function of increasing levels of fertilization: 0, 1, 2, 4, 8, 16, and 32 g/plant of 4-14-8 (%nitrogen-phosphorus-potassium) at seeding and similar amounts of amonium sulphate at 34th day of age. Each level of fertilizer was applied to eight replicates and the plants were kept 20 cm distance among them in the row and 70 cm distance in the column. The plants height was 65, 81, 87, 99, 121, 129, and 127 cm; the diameter was 8.5, 12.8, 13.8, 17.2, 18.7, 21.0, and 21.4 mm, and the volume was 25, 70, 86, 153, 220, 297, and 305 cm³, respectively. The corn responses to fertilization showed hyperbolic curves and followed the Michaelis-Menten relationship. The highest efficiency of use of nutrients happened at low-level fertilization, showing logarithm decay with increase in fertilization. Although maximum crop productivity is always desirable, it demands elevated levels of nutrients, but the efficiency of nutrient use decreases drastically as the level of the nutrient increases (34, 22, 17, 14, 8, and 4 cm/g; 9, 5, 4, 3, 2 ,1 mm/g; and 89, 60, 64, 49, 34, and 17 cm³/g for height, diameter, and volume, respectively, comparing each level of fertilizer with the zero level). In addition, elevated levels of fertilizers in agriculture leads to fast exhaustion of nonrenewable natural resources and environmental pollution, such as water contamination with nitrate; soil acidification; and emissions of CO₂ and N₂O to atmosphere, with deleterious effects on global warming.