Abstract
In the study two field experiments, two pot experiments and one seed germination experiment were conducted at Henfaes Research Farm, Bangor, North Wales, UK. Climatically, this area is marginal for forage maize, due to low summer temperatures and a short growing season for this tropical crop . A series of experiments were conducted on various aspects of the effects of elevated temperatures upon maize growth.An initial series of the experiments were conducted to study the effect of different temperature levels (7/5°C, 9/7°C, 11/9°C, 13/11 °C, 15/13°C, 17/15°C) on seed germination on four varieties in an incubator. During 1996 in a field experiment the effect of plastic film mulch on growth and yield on four varieties of maize (LG2080, Agio, Melody and Pursan) was studied. In the same season a pot experiment was conducted to study the effect of two periods of early heating in a glasshouse (3 and 5 week) on the growth of the same four varieties. In the following year 1997, another a field experiment, expanded in scope, was conducted to study the effect of plastic film mulch on the performance of three maize varieties (LG2080, Agio and Melody), with three sowing dates (15 April, 1 May and 15 May). Also a pot experiment was conducted to study the effect of three periods of early heating (0, 2, and 4 week) on three maize varieties (LG2080, Agio and Melody).
In both field experiment the effect of mulch was raise to the soil temperature at 5cm depth generating a maximum temperature difference between with mulch (+M) and without mulch (-M) of 5 °C. Plastic film mulches enhanced the rate of germination and establishment of seedlings was advanced by one week compared to unmulched treatments. The number of leaves, leaf area index, population density, and dry matter content all were greater under mulch, which contributed to a greater dry weight per m2 compared to unmulched treatments. Leaf length and breadth and leaf area were greater response to heating or mulching, and mulching increased the rate of leaf extension per Ontario Heat Unit (OHU) accumulated.
In both pot experiments shoot dry weight increased with increased period of heating from 0, 2, 3, 4 and up to 5 weeks. Tasseling and silking was also advanced when heating period was increased. Similarly in the field experiments tasseling and silking were advanced in mulched treatments, by 10 days in 1996 and between 5 to 7 days in 1997. Area per leaf and rate of growth were increased by early heating, even though plants spent most of their lives outside. As far as varieties were concerned, across all the experiments LG2080 produced average yields and higher dry matter content, while Agio produced a higher yield but lower dry matter content, and variety Melody produced high yield and dry matter along with early maturity. Variety Pursan was not suited to this location due to climatic factors.
In the incubator when temperature levels were decreased from 17/15 °C to 7/5 °C the germination of seeds was delayed and the total germination success also decreased in all varieties. Overall the seed germination rate in variety Melody was significantly higher followed by Agio and then LG2080. Pursan gave a very poor response even at 17/15 °C. Conversely Melody was the most cold tolerant, which supported results subsequently found in pot and field experiments. It was concluded that mulch effects were similar to those of heating, and that residual effects lasted throughout the life of the plants. Plastic mulches are able to significantly shorter the growing period to maturity of forage maize. The effect of early heating influence maize plant response to thermal time OHU, in that plants grew more rapidly well after the heating effect had ceased. Early heating was a more important determinant of crop dry weight and dry matter content
than cumulative OHU. As the simplest method of applying heating early in the season is plastic mulch, this raises the possibility of growing forage maize successfully in climatically marginal areas.
| Date of Award | 26 Nov 1998 |
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| Original language | English |
| Awarding Institution |
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| Sponsors | Winrock International |
| Supervisor | Robert Brook (Supervisor) |