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The effects of density and harvest time on growth and yield of forage corn (Zea mays L.) Tarimo, Akwilin J. P.


A field experiment was undertaken to investigate the effects of planting density on growth and yield of forage corn (Zea mays L., cv. DK 24) using modern methods of plant growth analysis and yield component analysis. A complete randomized block design was used with four planting densities and five harvests. The four planting densities were 49383, 67204, 87796 and 111111 plants per hectare. Replicate plants were harvested at 21 days after emergence (DAE), 42 DAE, 63 DAE, 85 DAE and 115 DAE. At each harvest, data were recorded of several primary growth characteristics, including plant height, stem diameter leaf areas and dry weights of stems, leaves, leaf sheaths, tillers and reproductive structures. The recorded data, and indices and ratios derived from recorded data, were analyzed by the analysis of variance, cubic spline regressions and the two-dimensional partitioning technique of yield component analysis. Yield per hectare varied significantly among densities from the second harvest (42 DAE) until maturity. At the crop maturity stage (30.8% crop dry matter content), the yield per hectare increased with increasing number of plants per hectare. The mean yields were: 15.1, 15.9 and 17.1 MT per hectare from the lowest planting density to the highest planting density, respectively. Conversely, yield per plant decreased linearly with increasing number of plants per hectare from 306.4 to 154.1 g/plant. All the primary plant growth characteristics were highly affected by the planting density treatment, and these effects increased with plant age. Thus, the variability in yield per plant among planting densities was accounted for by the variability of those growth characteristics. The plant growth indices showed that crop growth rate, leaf area index and biomass density were major contributors to yield variability per hectare among planting densities. Yield component analysis showed sporadic contributions by yield components depending on age and the direction of the two-dimensional partitioning technique of yield component analysis. The relative growth rates of yield and yield components did not clearly show the effects of planting density but strongly showed the time course trends of the relative growth rates within stand densities. All of the techniques used in this study complemented each other in the analysis of corn growth and productivity.

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