Inter-plant variation of grain yield components and kernel composition of maize crops grown under contrasting nitrogen supply

Abstract

High intra-specific competition pressure, which is common at most maize ( Zea mays L.) cropping conditions, promotes inter-plant variation and the appearance of extreme plant hierarchies with different ability to capture scarce resources (i.e., dominant and dominated plants) within a stand. The objectives of the current work were to analyze (i) inter-plant variation of grain yield per plant (GYP), GYP components (KNP: kernel number per plant; KW: kernel weight), and kernel composition, together with those of their physiological determinants, i.e., plant growth (PG) rate around silking (PGR S), PGR S per kernel (PGR S KNP −1) and PG during the effective grain-filling period per kernel (PG GF KNP −1), under contrasting N supply and (ii) the contribution of dominant and dominated plants to changes in inter-plant variation and mean values of the studied traits. For these purposes two maize hybrids previously characterized by their contrasting inter-plant variation under N stress (low: AX820 and high: AX877) were cultivated at high stand densities (9 and 12 pl m −2) at two N supplies (N 0: control and N 200: 200 kg N ha −1) without water restrictions. For AX820, PGR S data set at both N levels explored a similar range (1–7.4 and 1.2–7.4 g pl −1 d −1 for N 0 and N 200, respectively) with a positive skewness in N 0, and an almost normal distribution of data in N 200. In contrast, for AX877, inter-plant variation of PGR S exhibited a normal distribution in both N levels, and N fertilization only produced a displacement of data to higher PGR S values (0–4.3 and 0.7–5.7 g pl −1 d −1 for N 0 and N 200, respectively). The effect of inter-plant variation of PGR S on the coefficient of variation (CV) of KNP was of a greater magnitude in AX877 than in AX820 due to the more linear KNP response to PGR S of the former. For both hybrids, mean values of KW increased and the CVs decreased in response to high N supply. Differences among plants and N levels in KW were related to the duration of the effective grain-filling period. Inter-plant variation of protein and starch concentrations was higher in N 0 than in N 200, but that of oil concentration was not affected by N supply. The analysis of plant hierarchies resulted useful to understand changes in mean values and frequency distributions of several agronomic traits.