Scott A. Staggenborg

Tapping unsustainable groundwater stores for agricultural production in the High Plains Aquifer of Kansas, projections to 2110

Significance Society faces the multifaceted crossroads dilemma of sustainably balancing today’s livelihood with future resource needs. Currently, agriculture is tapping the High Plains Aquifer beyond natural replenishment rates to grow irrigated crops and livestock that augment global food stocks, and science-based information is needed to guide choices. We present new methods to project trends in groundwater pumping and irrigated corn and cattle production. Although production declines are inevitable, scenario analysis substantiates the impacts of increasing near-term water savings, which would extend the usable lifetime of the aquifer, increase net production, and generate a less dramatic production decline. Groundwater provides a reliable tap to sustain agricultural production, yet persistent aquifer depletion threatens future sustainability. The High Plains Aquifer supplies 30% of the nation’s irrigated groundwater, and the Kansas portion supports the congressional district with the highest market value for agriculture in the nation. We project groundwater declines to assess when the study area might run out of water, and comprehensively forecast the impacts of reduced pumping on corn and cattle production. So far, 30% of the groundwater has been pumped and another 39% will be depleted over the next 50 y given existing trends. Recharge supplies 15% of current pumping and would take an average of 500–1,300 y to completely refill a depleted aquifer. Significant declines in the region’s pumping rates will occur over the next 15–20 y given current trends, yet irrigated agricultural production might increase through 2040 because of projected increases in water use efficiencies in corn production. Water use reductions of 20% today would cut agricultural production to the levels of 15–20 y ago, the time of peak agricultural production would extend to the 2070s, and production beyond 2070 would significantly exceed that projected without reduced pumping. Scenarios evaluate incremental reductions of current pumping by 20–80%, the latter rate approaching natural recharge. Findings substantiate that saving more water today would result in increased net production due to projected future increases in crop water use efficiencies. Society has an opportunity now to make changes with tremendous implications for future sustainability and livability.

Grain Sorghum Water Requirement and Responses to Drought Stress: A Review

Abstract Because sorghum is a drought-tolerant crop, it is often preferred by producers in cases of expected water stress. The objectives of this review were to summarize the water requirements, effect of water stress, and hybrid variation in drought tolerance of grain sorghum, and to suggest possible solutions that could help narrow the gap between potential and actual dryland sorghum yield. We reviewed more than 70 reports in peer-reviewed journals, extension publications, books, and websites. Grain sorghum tolerates and avoids drought more than many other cereal crops, but the drought response of sorghum does not come without a yield loss. Water stress at the vegetative stage alone can reduce yield more than 36%, and water stress at the reproductive stage can reduce yield more than 55%. Eighty percent of sorghum production in the world is under dryland conditions. We deduced that by focusing on techniques that can improve water availability in sorghum growing season alone, we can double the current dryland sorghum yield with the existing genetic potential. Results of this review suggest the existence of genotypic variation in drought tolerance among sorghum hybrids due to possible physiological differences or vice versa. We concluded by presenting possible management options to reduce the effects of water stress in dryland conditions and suggesting possible areas of research.

Extracting Machinery Management Information from GPS Data

GPS data obtained during yield mapping operations for 23 fields were used to glean machinery management information. Yield monitor data were exported into the Ag Leader advanced format and GPS time, logging interval, mass flow, and distance were used to help assess combine performance. Field efficiency and capacity were determined. Time required to harvest, turn, and unload the crop were estimated. The relationship between efficiency and crop yield or unloading time was weak. Turning and efficiency were moderately correlated. Optimizing field traffic patterns to minimize turns appeared more opportunity for increasing field efficiency than unloading on the go.

The Simple Script Wrapper for OpenMI

Integrated environmental modeling enables the development of comprehensive simulations by compositing individual models within and across disciplines. The Simple Script Wrapper (SSW), developed here, provides a foundation for model linkages and integrated studies. The Open Modeling Interface (OpenMI) enables model integration but it is challenging to incorporate scripting languages commonly used for modeling and analysis such as MATLAB, Scilab, and Python. We have developed a general-purpose software component for the OpenMI that simplifies the linking of scripted models to other components. Our solution enables scientists to easily make their scripting language code linkable to OpenMI-compliant models fostering collaborative, interdisciplinary integrated modeling. The simplicity afforded by our solution is presented in a case study set in the context of irrigated agriculture. The software is available online as supplementary material and includes an example that may be followed to employ our methods.

Evaluation and characterization of sorghum biomass as feedstock for sugar production.

Conversion of cellulosic biomass, such as agricultural residues, to biofuels offers significant economic, environmental, and strategic benefits. Sorghum is an important energy crops in the U.S. It is a renewable resource and is currently grown on about 10 million acres in the U.S. However, at present, there is a lack of scientific information and knowledge about the use of sorghum biomass for biofuel production. The objective of this research was to evaluate and characterize sorghum biomass as a feedstock for sugar production. Five types of sorghum biomass (brown midrib sorghum, forage sorghum, grain sorghum, photoperiod-sensitive sorghum, and sweet sorghum) were characterized and evaluated for sugar production. Pretreatment with dilute acid was used to increase yield of fermentable sugars. Effects of sulfuric acid concentration, treatment temperature, and residence time on yield of fermentable sugars were studied. Accellerase 1000 was used to hydrolyze cellulose into glucose at 50°C and pH 4.8 for 96 h. A high percentage of enzymatic conversion of cellulose (ECC) was observed for sorghum biomass that was pretreated under severe pretreatment temperature (85% to 98% ECC for biomass pretreated at 165°C for 10 min; 65% to 82% ECC for biomass pretreated at 140°C for 30 min). However, mass recovery and cellulose recovery of the solid fraction after pretreatment decreased under severe pretreatment conditions (70% to 85% cellulose recovery for sorghum biomass pretreated at 140°C for 30 min; 31% to 58% cellulose recovery for sorghum biomass pretreated at 165°C for 10 min).

EFFECT OF PLANTER SPEED AND SEED FIRMERS ON CORN STAND ESTABLISHMENT

Proper planter adjustment and operation play an important role in uniform stand establishment for corn. A two-year study was conducted to assess the impact of planter speed and a seed-firming device on corn stand establishment and grain yield. A planter equipped with a vacuum metering system and commercial seed firming devices was used in this study. Corn was seeded in a randomized complete block experiment at three speeds at two locations in Kansas (USA). Plant stand was counted at regular intervals after the first plant emerged to determine emergence rate. Plant spacing within each treatment was measured after complete emergence. Mean plant spacing, standard deviation in spacing, and four spacing indices (miss, multiple, quality of feed, and precision) were calculated to evaluate the plant spacing data. The miss and multiple indices indicate the number of skips and doubles. Planter performance as measured by these indices and standard deviation in plant spacing decreased as planter speed increased. The seed firmer reduced plant spacing standard deviations at a rate equivalent to the standard deviation increase observed when planter speed increased approximately 1.6 km/h (1 mph). Corn yield was reduced as planter speed increased at one location, but not the others. This response was the result of lower plant densities at the higher planter speeds, suggesting that one of the goals of the planting process should be to establish adequate plant densities. The seed firmer had no impact on corn yield.

Features and Fermentation Performance of Sweet Sorghum Juice after Harvest

As demand for and production of fuel ethanol increase to unprecedented levels, feedstocks for ethanol production will become more diverse. Sweet sorghum is an ideal feedstock for fuel ethanol production in the Southeast and Midwest. Sweet sorghum juices usually contain approximately 16-18% fermentable sugar, which can be directly fermented into ethanol by yeast. Technical challenges of using sweet sorghum for biofuels are a short harvest period for highest sugar content and fast sugar degradation during storage. This study showed that as much as 20% of the fermentable sugars can be lost in 3 days at room temperature because of activities of contaminated bacteria, which lead to significant increases in bacterial count and decreases in pH values. No significant changes in pH value, sugar contents, and profiles were observed in juices stored in a refrigerator. Fermentation efficiencies of fresh juice, autoclaved juice, and concentrated juice with 20% sugar were higher than 93% in the laboratory shake flask batch process. Fermentation of concentrated juices with 25% and 30% sugars were not complete. A significant amount of fermentable sugars remained in the finished beer of these high sugar concentrated juices. Glycerol contents in finished beers from high sugar content concentrated juices were higher than in beers from normal juices. These results help identify the most important factors affecting the quality of sweet sorghum juice under different processing and storage conditions, enabling development of effective strategies to process the juice, preserve fermentable sugars, and retain the processing properties of the juice during processing, transportation, and storage.

Using Yield Monitors to Assess On-Farm Test Plots

Farmer test plots have become a staple for production agriculture. These plots can range from simple side-by-side demonstration plots to a replicated research study. The rush of harvest often creates a challenge for harvesting these plots. Yield monitor data were collected from field scale plots in multiple states to assess ability to measure on-farm research. Grain mass was also measured for each plot with a weigh wagon or certified scale. The variability of yield monitor error (standard deviation) was not correlated with the magnitude of the error (mean). Thus calibration in and of itself will likely not result in more consistent yield monitor error. Determining if treatments or observations from non-replicated studies are different will be challenging. Depending on the chosen probability level, this data indicate that distinguishing a 3 to 9 percent difference was possible. Statistical analysis of replicated trials results in similar conclusions with reference and yield monitor data. Mass flow rate is one factor impacting yield monitor error.

Impact of pelleting and acid pretreatment on biomass structure and thermal properties of wheat straw, corn stover, big bluestem, and sorghum stalk.

Agricultural residues and energy crops are considered potential feedstocks for bioethanol production because of their high availability and energy potential as well as relatively low cost. Previous studies have shown that pelleting biomass feedstocks could increase their bulk density, thus increasing ease of handling and decreasing cost of handling and transportation. The pelleting process has also been shown to have a positive impact on the sugar yield of biomass. However, the effects of the pelleting process on biomass structure have not yet been studied. Therefore, the objective of this study was to investigate the impact of dilute acid pretreatment and the pelleting process on biomass structure of cellulosic materials, including crystallinity index (CrI,%) measured by the x-ray diffraction (XRD) method, structure of constituents and chemical changes determined by Fourier transform infrared spectroscopy (FTIR) and solid-state cross-polarization/magic angle spinning (CP/MAS) 13C NMR spectroscopy, morphological structure determined by scanning electron microscopy (SEM), and thermal properties determined by thermogravimetric analysis (TGA). Wheat straw, big bluestem, corn stover, and photoperiod-sensitive sorghum were used for this study. Pelleting did not have a significant effect on the pattern of FTIR spectra and solid-state 13C NMR spectra of biomass. XRD analysis showed that biomass crystallinity increased after dilute acid pretreatment and the pelleting process. Based on SEM analysis of biomass, dilute acid pretreatment and pelleting enhanced the removal of the softened surface region of biomass. TGA analysis showed that the decomposition temperature of pelleted biomass was slightly higher than that of corresponding unpelleted biomass, indicating that the pelleted biomass was more thermally stable than the unpelleted biomass.

Evaluating Surface Energy Balance System (SEBS) using Aircraft data collected during BEAREX07

Evapotranspiration (ET) is an essential component of the water balance and a major consumptive use of irrigation water and precipitation on cropland. Remote sensing based surface energy balance algorithms are now capable of providing accurate estimates of spatial-temporal ET. Uses of these spatial ET estimates are innumerable including hydrological modeling, irrigation scheduling, drought and flood monitoring and global climate change studies. The objective of this study was to evaluate the ability of the Surface Energy Balance System (SEBS) to estimate hourly ET fluxes using very high resolution (0.5-1.8 m) aircraft images acquired during the BEAREX07 (Bushland ET and Agricultural Remote Sensing Experiment 2007). Accuracy of the predicted ET fluxes were investigated using observed data from 4 large weighing lysimeters, each located at the center of 4.7 ha field in the USDA-ARS Conservation and Production Research Laboratory, Bushland, Texas. The uniqueness and the strength of this study come from the fact that it evaluates the SEBS for irrigated and dryland conditions simultaneously with each lysimeter field planted to irrigated forage sorghum, irrigated forage corn, dryland clumped-grain sorghum, and dryland row-grain sorghum. Eleven images acquired during early and mid cropping seasons (June 24 - July 27) were used in the study. SEBS algorithm performed equally well for both irrigated and dryland conditions in estimating the hourly ET with overall mean bias error and root mean square of -0.01 and 0.11 mm h 1 (-1.53% and 20.27%), respectively.