Inter-plant competition for resources in maize crops grown under contrasting nitrogen supply and density: Variability in plant and ear growth |
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Authors: | M.A. Rossini G.A. MaddonniM.E. Otegui |
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Affiliation: | Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA), Departamento de Producción Vegetal, Facultad de Agronomía, Universidad de Buenos Aires, Av., San Martín 4453 (C1417DSE), Argentina |
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Abstract: | 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. a size-asymmetric competition for light). Contrarily, a size-symmetric competition has been proposed for the acquisition of soil resources 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 on that promoted by a high plant population density. Two maize hybrids with contrasting tolerance to crowding (tolerant AX820 and intolerant AX877) were cultivated under different combinations of stand densities (6, 9 and 12 plants m−2) and N supplies (0 and 200 kg N ha−1) without water restrictions. Variability in plant growth rate among plants was computed 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 in biomass partitioning to the ear (partition index; PI), ear growth rate during the critical period (EGRCP) and kernel number per plant (KNP) was also established. Reduced N supply increased the coefficient of variation (CV) of PGRER, PGRCP, EGRCP and KNP (0.05 < P < 0.10). The CVs of PGRCP, PI, EGRCP and KNP augmented (0.001 < P < 0.10) at the highest stand density. The CVs of PGRER, PGRCP, PI and KNP were larger for hybrid AX877 than for hybrid AX820 (0.001 < P < 0.10). N fertilization smoothed the initial plant-to-plant variability, but the extent of this benefit in a maize crop is genotype dependent; it was much larger in the hybrid tolerant to crowding stress than in the intolerant one. For the latter, the variability held during the critical period around silking and produced a high CV of KNP. |
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Keywords: | Maize Zea mays L. Inter-plant competition Plant population density Nitrogen Plant growth Ear growth Biomass partition |
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