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Ohio State University (2015)

Agronomic and Physiological Responses of Modern Drought-Tolerant Maize (Zea mays L.) Hybrids to Agronomic Production Practices

Lindsey, Alexander Joseph

Titre : Agronomic and Physiological Responses of Modern Drought-Tolerant Maize (Zea mays L.) Hybrids to Agronomic Production Practices

Auteur : Lindsey, Alexander Joseph

Université de soutenance : Ohio State University

Grade : Doctor of Philosophy (PhD) 2015

Résumé
The potential of climate change to impact crop production has increased farmer interest in new drought-tolerant maize (Zea mays L.) hybrids. However, limited research on the physiology and agronomic management of these hybrids has been published. Three separate field studies were conducted from 2012 through 2014 at Hoytville, South Charleston, and Wooster, OH to evaluate the physiological and morphological responses of two non-transgenic drought-tolerant hybrids (P0210 and P1352) and two conventional hybrids (P0448 and P1184) to nitrogen application rate (0, 67, 134, 202, and 269 kg N/ha), plant population (59,000, 74,000, 89,000, 104,000, and 124,000 plants/ha), planting date (May or June), and watering treatment (rainfed plus irrigation and water exclusion). Studies in which gas exchange was measured on P1352 and P1184 found drought-tolerant hybrid maintained or increased net photosynthetic rates relative to the conventional hybrids while reducing or maintaining a similar level of stomatal conductance. The ratios of chlorophyll fluorescence were greater for the drought-tolerant hybrid during the vegetative growth stages. The drought-tolerant hybrid also exhibited a greater leaf area index (LAI) and specific leaf area (SLA) as compared the conventional hybrid. The relative chlorophyll content (RCC) was lower in the drought-tolerant hybrids, and P1352 exhibited lower chlorophyll and ear-leaf N concentrations compared to P1184 as was hypothesized. The drought-tolerant hybrids also exhibited a shorter anthesis-silking interval (ASI). The grain starch content was generally similar in the drought-tolerant hybrids compared to the conventional hybrids, but the drought-tolerant hybrids had greater oil content and less protein content than the conventional hybrids. All hybrids exhibited similar responses to population, including a decrease in RCC and an increase in ASI and LAI, and similar changes in grain protein, oil, and starch content. The grain yield at the agronomic optimum nitrogen rate (AONR) was similar regardless of hybrid (<5%), but the AONR was greater (3-11%) for the drought-tolerant hybrids. This higher N rate determined from regression analysis may be due to an increase in water use efficiency, which could decrease N use efficiency. The optimum plant population (OPP) was lower by 3,600 plants/ha and maximum yield at the OPP was greater by 0.2 Mg/ha for the drought-tolerant hybrids compared to the conventional hybrids when planted in May across all locations. When planting was delayed until June the maximum yield was 0.1 Mg/ha less but the OPP was 16,400 plants/ha less for the drought-tolerant hybrids compared to the conventional hybrids. When the conventional hybrid yield was less than 12.2 Mg/ha, a yield advantage was observed in 66% of our observations when a drought-tolerant hybrid of similar maturity was grown under identical conditions. However, when the conventional hybrid yielded greater than 12.2 Mg/ha, 60% of the time the drought-tolerant hybrid produced less grain than the conventional counterpart. These results suggest that the physiological traits of drought-tolerant hybrids may positively contribute to yield when yield potential is depressed, but under favorable conditions the traits of the conventional hybrid may be more advantageous for yield production.

Mots clés : corn ; drought ; tolerant ; drought-tolerant ; agronomic ; physiology ; plant population ; plant density ; planting date ; nitrogen ; photosynthesis ; stomatal conductance ; water exclusion

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Page publiée le 7 septembre 2015, mise à jour le 25 décembre 2018