Exposure to soils contaminated with heavy metals can pose human health risk to children through ingestion of contaminated soil. Soil properties such as soil pH, reactive Fe and Al oxide content, clay content, soil organic matter (SOM), and cation exchange capacity (CEC) can reduce contaminant bio-accessibility and exposure. In vitro bio-accessibility (%IVBA) of As and Pb in 19 soils was determined using U.S. EPA Method 1340. Soil properties reduced the bio-accessibility of As by 17–96.5% and 1.3–38.9% for Pb. For both As and Pb, bio-accessibility decreased with increasing Al and Fe oxide content. Al oxides were found to be the primary driver of As and Pb bio-accessibility. Multiple regressions with AlOx, soil pH, %clay and/or FeOx predicted %IVBA As (p < 0.001). The multiple regression including log (FeOx + AlOx) and %clay explained 63% of the variability in %IVBA Pb (p < 0.01). Fe and Al oxides were found to be important drivers of As and Pb bio-accessibility, regardless of in vitro method. These findings suggested soil pH should be used in addition to reactive oxides to predict bio-accessible As. Risk-based adjustments using soil properties for exposure via incidental ingestion should be considered for soils contaminated with As and/or Pb.

Gypsum is an excellent source of Ca and S, both of which are required for crop growth. Large amounts of by-product gypsum [Flue gas desulfurization gypsum-(FGDG)] are produced from coal combustion in the United States, but only 4% is used for agricultural purposes. The objective of this study was to evaluate the effects of (1) untreated, (2) short-term (4-year annual applications of gypsum totaling 6720 kg ha⁻¹), and (3) long-term (12-year annual applications of gypsum totaling 20,200 kg ha⁻¹) on alfalfa (Medicago sativa L.) growth and nutrient uptake, and gypsum movement through soil. The study was conducted in a greenhouse using undisturbed soil columns of two non-sodic soils (Celina silt loam and Brookston loam). Aboveground growth of alfalfa was not affected by gypsum treatments when compared with untreated (p > 0.05). Total root biomass (0–75 cm) for both soils series was significantly increased by gypsum application (p = 0.04), however, increased root growth was restricted to 0–10 cm depth. Soil and plant analyses indicated no unfavorable environmental impact from of the 4-year and 12-year annual application of FGDG. We concluded that under sufficient water supply, by-product gypsum is a viable source of Ca and S for land application that might benefit alfalfa root growth, but has less effect on aboveground alfalfa biomass production. Undisturbed soil columns were a useful adaptation of the lysimeter method that allowed detailed measurements of alfalfa nutrient uptake, root biomass, and yield and nutrient movement in soil.

On-farm research (OFR) has become popular as a result of precision agriculture technology simplifying the process and farm software capabilities to summarize results collected through the technology. Different OFR designs exists with strip-trials being a simple approach to evaluate different treatments. Common in OFR is the use of yield monitors to collect crop performance data since yield represents a primary response variable in these type studies. The objective was to investigate the ability of grain yield monitoring technologies to accurately inform strip trials when frequent yield variability exists within an experimental unit. A combination of six sub-plot treatment resolutions (TR) that differed in length of imposed yield variation (7.6, 15.2, 30.5, 61.0, 121.9, and 243.8 m) were harvested at combine ground speeds of 3.2, 6.4, 7.2, and 8.1 kph, depending on study site (three study sites total). Intentional yield differences in maize (Zea mays L.) were created for each sub-plot by alternating the amount nitrogen (N) applied: 0 or 202 kg N/ha. Yield was measured by four commercially available yield monitoring (YM) technologies and a weigh wagon. Comparisons were made between the accumulated mass of the YM technology and weigh wagon through percent differences along with testing the significance of the plotted relationship between YM and weigh wagon. Results indicated that yield monitoring technology can be used to evaluate strip trial performance regardless of yield frequency and variability (error < 3%) within an experimental unit when operating within the calibrated range of the mass flow sensor. Operating outside of the calibrated range of the mass flow sensor resulted in > 15% error in estimating accumulated weight and overestimation of yield by 23%. Finally, no significant differences existed in estimating accumulated weight values between grain yield monitor technologies (all p-values ≥ 0.54).