Influence of methanol on sugarbeet yield and photosynthesis.

Foliar application of methanol has improved growth and productivity experimentally in a number of agricultural crops. To test the possibility that methanol application might improve sugarbeet yield, we conducted a replicated field study at Fort Collins, Colorado in 1994 with two commercial sugarbeet varieties (Monohikari, Beta 2398) and one public breeding line (FC709-2). Methanol was foliarly applied at about ten day intervals throughout the growing season starting at 40 dap. Plants were treated with 50% methanol plus 0.1% Triton-X surfactant, or 50% methanol plus 0.1% Triton-X plus 0.2% monosodium glutamate (MSG) as a nitrogen source. Control plants received no spray treatment. Two regimes of irrigation were included, one that provided water at a level typical of commercial growing practice and one in which about 50% as much water was applied on the same schedule, intentionally causing chronic water stress. Photosynthetic gas exchange was determined on August 26 and September 8 at mid-day on a subset of plots. Root yield and percentage root sucrose were determined at harvest, and sucrose yield was calculated from those values. The summer was warm and dry in 1994 and even plants in the higher irrigation regime were water-stressed (i.e., wilted at mid-day), and no significant differences in root yield, percent root sucrose, or sucrose yield occurred due to irrigation treatment. Significant differences for each of the three parameters occurred among varieties and for methanol treatments. Both methanol treatments resulted in significantly lower root weight and sucrose yield than the control, and methanol plus MSG application resulted in significantly lower root weight and sucrose yield than application of only methanol. Percentage sucrose was statistically similar in control and methanol treatments, but treatment with methanol plus MSG resulted in lower percentage sucrose. Photosynthesis was increased in methanol treated plots, but this result was not consistent. If methanol treatment resulted in higher photosynthesis in the short term, this may have resulted in greater above-ground growth at the expense of root growth and root sucrose storage, which could account for the observed lower root and sucrose yield in the treated plots. If early-season methanol application timing and concentration could be adjusted to stimulate early canopy formation, so that maximal light interception could be achieved earlier in the season, this might lead to increased sucrose yield at harvest.