Keywords: root length, root surface area, root density, rate of root elongation, intensity of phosphorus absorption.
During the days following germination, when the seed’s reserves run out and root growth is slow, stress may occur due to a deficit of phosphorus (P), which has repercussions in later development of the plant and its yield. Plant species differ in their ability to absorb P, and this depends on the amount of available P in the soil and the capacity of the root system to acquire it. The objective of this study was to compare, under controlled conditions, the absorption of P, the morphological (length, surface area, and density) and physiological (intensity of P absorption) root characteristics of maize seedlings (cv. Batán-92) and potato (cv. FL795) when phosphate fertilizer is applied locally. The soil used in the experiment was a sandy loam-textured Andisol. The treatments were P localized at 2, 5, and 8 cm to one side of the seed (L), below the seed at 2, 5, and 8 cm deep (Pr), incorporated (I), and a control without P. The amounts of P were 81 and 54 mg.kg-1, in function of the forms of application. The maize was harvested at 17 and 30 days after germination, and potato was harvested 34 days after germination. The growth behavior of the maize and potato roots treated with P localized in the different forms was not the same. Potato developed an average ratio of radical density in the fraction fertilized with P, compared to the rest of the soil, 2.2 times higher than maize, i.e. potato depends more on P applied as a fertilizer than maize. The accumulation of P and the production of dry matter in maize and potato were in function of the root characteristics and the availability of P in the soil. The total mean root density in maize was 2.7 times higher than in potato. To compensate the lower root density and rate of root lengthening, potato required more available P in the soil than maize and developed a greater intensity of absorption of this element [100 nmol.cm-1 (34 days) vs. 24 nmol.cm-1 (30 days), respectively].