Intra-specific competition in maize grown under contrasting nitrogen offers: variability in plant and ear growth

ROSSINI, M. A., MADDONNI, G. A., OTEGUI

FIELD CROPS RESEARCH

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2011 vol. 121 p. 373 - 380

0378-4290

Increased plant population density in irrigated and fertilized maize crops, enhances plant-to-plant variability since early vegetative stages, because the most suppressed individuals of the stand, intercept less radiation per unit leaf area than the dominant ones (i.e. an asymetric light competition). Contrarily, a symmetric-size competition has been proposed for soil resources acquisition in a plant community (e.g, N capture per unit root length is similar among plants of different size). Hence, N fertilization effect on the variability of maize plants would depend on the initial plant-to-plant variability or that promoted by a the high plant population density. Two maize hybrids with contrasting tolerance to crowding (AX820 and AX877, as the tolerant and the intolerant hybrid, respectively) were cultivated under different combinations of stand densities (6, 9 and 12 plants m-2) and N offers (0 and 200 kg N ha-1) without water restrictions. Variability of plant growth among plants was recorded along the cycle, especially after fertilizer was applied (i.e. the early reproductive period; PGRER) and during the critical period around silking (PGRCP). Plant-to-plant variability of biomass partition (partitioning index; PI) to the ear, ear growth rate during the critical period (EGRCP) and kernel number per plant (KNP) was also recorded. Reduced N offer increased the coefficient of variation (CV) of PGRER, PGRCP, EGRCP and KNP (0.05 < P < 0.10). At the highest stand density the CVs of PGRCP, PI, EGRCP and KNP was augmented (0.001 < P < 0.10). The CVs of PGRER, PGRCP, PI and KNP were larger for hybrid AX877 than for hybrid AX820 (0.001 < P < 0.10). N fertilization reduced the initial plan-to-plant variability of AX820. Contrarily, N fertilization did not completely modify the initial plant-to-plant variability of AX877, which was sustained during the critical period around silking and reflected in the highest CV of KNP.