Effects of N-carriers and K-levels, on P-uptake in corn

Abstract

A study, was made on the effects of N-sources (N₁ - 100 ppm N-NO₃ x N₂ = 100 ppm NH₄) and K levels (32 and 64 ppm) on dry matter accumulation, P-uptake, root volume, and rhizocylinder pH (pHr) of corn (Zea mays L.). Plants (cv. Centralmex) were grown in 5 liter pots, and harvested at 15, 30 and 45 days after-emergence. NH₄ - plants showed reduced growth at the first harvest, K overcame that effect. This effect of NH₄ was attributed either to soluble-N accumulation in tissues or to NH₄ - phosphate complexes in the soil. The beneficial effect of K on plant growth should then be due to development of K-NH₄ - phosphate complexes. NO₃ and K affected positively root volume. There was a decrease in pH_r between 15 and 45 days, and NH₄-N pots had the lowest pH. In the NO₃-N treatments, decrease in pH_r could be attributed to the small N + P/K relationships (0,8 for N₁ plants and 0,66- 0,90 for N₁K₁ plants at 30 and 45 days). There was a negative relationship between pH and P-uptake (except for NH₄ - only treatments).