Does increasing plant population density alter sugar yield in high stalk-sugar maize hybrids?

Citation

Ma, B.L., Zheng, Z.M., Morrison, M.J. (2017). Does increasing plant population density alter sugar yield in high stalk-sugar maize hybrids?. Crop & Pasture Science, [online] 68(1), 1-10. http://dx.doi.org/10.1071/CP16393

Plain language summary

The World-wide reduction in non-renewable fossil fuel resources and the rising concentration of atmospheric carbon dioxide are stimulating the use of crop-based renewable energy. The physiological similarity between corn and sugarcane suggests that the energy units (EU; units of output energy per unit energy required for production) for ethanol production from corn stalks with high sugar concentration may be close to that of sugarcane and much higher than that of corn grain. The optimum plant population density (PPD) for silage corn may be different from grain corn, and it may vary with hybrid and region. Increasing PPD would lead to a larger source for assimilate production, causing partial or complete barrenness of the plant at high PPD due to insufficient sink demand or unbalanced source-sink relationships. Therefore, it was hypothesized that by increasing PPD, a smaller sink size or an unbalanced source-sink relation may benefit stalk-sugar accumulation and increase stalk sucrose yield. The objective of this study was to examine the effect of PPD on sugar accumulation, dry matter (DM) production, silage and sucrose yields of sugarcorn. The information generated will be useful for further development of sugarcorn as a dual-purpose bioenergy/high energy silage crop in short-season regions unable to grow sugarcane.

Our data indicated that increasing PPD led to the changes in source-sink relation, resulting in higher stalk sugar content in some of the sugarcorn hybrids. Silage DM, and silage yield after sugar extraction were affected by genotype and PPD, with significant differences exhibited between types of corn hybrids, and a decline from the target PPD of 100 K to 125 K plants ha-1. Stalk sucrose concentration and sucrose yields were mainly affected by genotype, with CO348xC103 exhibited the greatest stalk sugar concentration and fermentable sucrose yield , at the target PPD of 125 (or actual 118 + 7) K ha-1. Clearly, suitable PPD in corn was dependent upon the purpose of usage. The marginal effects and relationships of PPD on/with silage DM, silage yield and stalk sucrose yield suggest that the current recommended PPD (75 - 85 K plants ha-1) for commercial grain and silage corn production in the region, is likely applicable for sugarcorn for silage use. If the sugarcorn is designated as bioenergy crop or for dual-purpose use, the optimum PPD is likely to be around 107 K plants ha-1 or slightly higher. The information generated from this study is useful for further development of dual-purpose sugarcorn in short-season regions of Canada and elsewhere.

Abstract

Escalating demands for food and green energy have renewed interest in the dual-purpose use of maize (Zea mays L.) for a biofuel and high-energy forage crop. Recently, maize hybrids with high stalk-sugar (sugarcorn) have been developed. It is important to determine how agronomic practices, for example altering plant population density (PPD), affect stalk-sugar yields of these newly developed hybrids and to advance knowledge required for producing sugarcorn as a dual-purpose bioenergy-high energy silage crop in short-season regions unable to grow sugarcane. A field experiment was conducted for 3 years to assess the effect of PPD on stalk-sugar accumulation, dry matter production, silage and sucrose yields of sugarcorn compared with two commercial silage hybrids. Targeted PPD ranged from 75000 to 150000 plants ha-1 in increments of 25000 plants ha-1. We found that increasing PPD from 75000 to 125000 plants ha-1 increased stalk sugar concentrations by up to 25% in some of the sugarcorn hybrids, with minimum change in the conventional check hybrids. The sugarcorn hybrid CO348×C103 had the highest stalk sugar concentration (128gkg-1) and sucrose yield of up to 3.8Mgha-1 at the targeted PPD of 125000 (or actual 118000±7000) plants ha-1. By contrast, the check silage hybrids produced at most 2.0Mgha-1 of sucrose yield with much lower stalk sugar concentrations (53-65gkg-1). Sugarcorn hybrids had generally lower grain yield with greater plant barrenness (the failure of a plant to produce a normal ear) and severer head smut infestation than the conventional silage hybrids. Our results suggest that as a silage crop, the current recommended PPD of 75000-85000 plants ha-1 for commercial silage maize production in the region is likely suitable for sugarcorn, and a higher PPD is required if sugarcorn hybrids are designated as a biofuel crop or for dual-purpose use.

Publication date

2017-01-01