Moisture and yield of corn stover fractions before and after grain maturity

Corn stover is a currently low-value product that has been suggested as an ideal pioneer cellulosic feedstock for conversion to chemicals and fuel because of its abundance and proximity to existing grain-to-ethanol conversion facilities. However, corn stover is high in moisture at the time of grain harvest. High-moisture corn stover is difficult to handle, spoils readily, is prone to spontaneous combustion, and is a safety hazard when moldy; thus, field drying becomes an important consideration. Data on field moisture content, quantity, and quality of the corn plant fractions are essential to the on-going analysis of the stover supply system. This study involved monitoring the in-field dry down and biomass yield in two corn hybrids, Pioneer 32K61 and 32K64 (Bt), grown under southeastern U.S. conditions. The standing corn was sampled over a 109-day period that was started roughly a week before estimated grain physiological maturity until several weeks after the grain had reached harvest moisture. The two hybrids seemed to have no visual differences in field drying rates; hence, their data were pooled for analysis. The stalk fraction had the highest moisture over the study period, but by the end, 213 days after planting, all components of the corn plant reached nearly the same moisture content of 10% to 13% w.b. Moisture content of the stover could be estimated by doubling the grain moisture content when the grain moisture was between 18% and 31% w.b. After physiological maturity, the dry matter content of the stalk and husk fractions declined steadily. The leaf fraction mass sustained substantial losses (about 74%) very rapidly, mainly due to wind and rain damage. The amount of dry stover was about 50% of the total dry plant material over the monitoring period with stalks comprising 50% of the stover dry matter at the time grain was harvested. These data for Tennessee conditions (southeastern U.S.) support use of the convenient 1-to-1 rule of thumb for estimating stover dry matter from grain dry matter, but strictly qualified to only when grain is at the typical harvest range of 30% to 18% moisture.