A five-year assessment of corn stover harvest in central Iowa, USA

Abstract

Sustainable feedstock harvest strategies are needed to ensure bioenergy production does not irreversibly degrade soil resources. The objective for this study was to document corn (Zea mays L.) grain and stover fraction yields, plant nutrient removal and replacement costs, feedstock quality, soil-test changes, and soil quality indicator response to four stover harvest strategies for continuous corn and a corn-soybean [Glycine max. (L.) Merr.] rotation. The treatments included collecting (1) all standing plant material above a stubble height of 10 cm (whole plant), (2) the upper-half by height (ear shank upward), (3) the lower-half by height (from the 10 cm stubble height to just below the earshank), or (4) (2005, 2007, and 2009). Compared to harvesting only the grain, collecting stover increased the average N-P-K removal by 29, 3 and 34 kg ha −1 for continuous corn and 42, 3, and 34 kg ha −1 for rotated corn, respectively. Harvesting the lower-half of the corn plant (Treatment 3) required two passes, resulted in frequent plugging of the combine, and provided a feedstock with low quality for conversion to biofuel. Therefore, Treatment 3 was replaced by a "cobs-only" harvest starting in 2009. Structural sugars glucan and xylan accounted for up to 60% of the chemical composition, while galactan, arabinan, and mannose constituted less than 5% of the harvest fractions collected from 2005 through 2008. Soil-test data from samples collected after the first harvest (2005) revealed low to very low plant-available P and K levels which reduced soybean yield in 2006 after harvesting the whole-plant in 2005. Average continuous corn yields were 21% lower than rotated yields with no significant differences due to stover harvest. Rotated corn yields in 2009 showed some significant differences, presumably because soil-test P was again in the low range. A soil quality analysis using the Soil Management Assessment Framework (SMAF) with six indicators showed that soils at the continuous corn and rotated sites were functioning at an average of 93 and 83% of their inherent potential, respectively. With good crop management practices, including routine soil-testing, adequate fertilization, maintenance of soil organic matter, sustained soil structure, and prevention of wind, water or tillage erosion, a portion of the corn stover being produced in central Iowa, USA can be harvested in a sustainable manner. KeywordsSingle-pass stover harvest system, Biofuel feedstock, Nutrient removal, Sustainability, Soil Management Assessment Framework (SMAF), Renewable energy assessment project (REAP) Disciplines Agriculture | Bioresource and Agricultural Engineering CommentsThis article is from

Corn stover harvest and tillage impacts on near-surface soil physical quality

“…Negative effects of corn stover harvest on Bd under no-tillage were also reported by Blanco-Canqui et al (2006, who consistently found lower structural stability and consequently an increased susceptibility to compaction. However, other studies have reported no effects of stover harvest on Bd (Karlen et al, 1994(Karlen et al, , 2011bVillamil et al, 2015). We hypothesize that leaving corn stover on the soil surface reduced Bd through a combination of effects including protection against soil compression by machinery wheel traffic as verified by Braida et al (2006), reduced axel load associated with machinery used for alfalfa production, and perhaps preservation of active organic carbon fractions involved in stabilizing soil aggregates resulted in lower average Bd values for the no-tillage treatment.…”

“…Corn stover has been identified as a potential feedstock for biofuel production because of its high cellulosic content, large volume of production and generally wide availability (Karlen et al, 2011b in the USA and other countries around the world. However, as the amount of corn stover left on the soil surface is diminished, organic C inputs are reduced, which over the time can potentially decrease soil organic matter -SOM (Karlen et al, 2011a;Jin et al, 2015) and thus affect soil structure formation and stability (Six et al, 2000).…”

Multilocation Corn Stover Harvest Effects on Crop Yields and Nutrient Removal

“…Yields were adjusted to a constant water content of 155 g kg −1 for comparison among studies. Stover yields were also determined in several different ways including (1) collecting samples from a 2-m length of row and fractionating the biomass into (a) plant parts above the ear shank, (b) below the ear shank, (c) cobs, and (d) grain; (2) attaching a canvas tarp to a commercial-scale combine to collect all residue from each plot, weighing all of the residue, and then dividing and returning a portion to each plot to create removal rates of 0, 50, or 100 % of the biomass; (3) harvesting with a single-pass combine designed to simultaneously collect grain and stover [15]; (4) collecting stover with a Hesston Stackhand 1 after combining the grain; or (5) collecting stover with a commercial fail chopper after combining the grain. Stover mass was calculated using dry weights from the hand samples, or for the mechanically collected material, it was determined by weighing, subsampling, and drying a representative sample to a constant weight, so that the quantities of stover removed could be compared among sites at a water content of 0 g kg −1 .…”

“…However, the decision to harvest corn stover for bioenergy or bioproduct development is not that simple, because stover also supports many ecosystem services [12][13][14] and its harvest will increase annual nutrient removal [15][16][17]. Several reviews [e.g., 18] and workshops (e.g., www.swcs.org/roadmap) have stressed the importance of corn stover for protection against wind and water erosion, improving soil aggregation and structure, increasing infiltration and water retention, and mitigating soil temperature fluctuations.…”

Dedicated Energy Crops and Crop Residues for Bioenergy Feedstocks in the Central and Eastern USA

“…Mourtzinis et al [69] showed that harvesting the above-ear corn plant fraction, while leaving the remaining stover in the field for soil erosion protection and soil organic matter maintenance, is a potential option for corn stover harvest in the Southeast. Other research concluded that harvesting the upper half of standing stover with cobs produced the highest quality feedstock and maintained soil productivity as determined by the soil management assessment framework (SMAF) [70,71]. Total precipitation and average air temperature during the growing season were strongly correlated with stover chemical composition, and the above ear portion of stover was more desirable due to lower lignin and higher cellulose content [72].…”