Agricultural soils are in peril. Multiple lines of observational and empirical evidence suggest that we are losing the world’s fertile soils at an alarming rate, worsening the on-going global food crisis. It is increasingly clear that the risk of soil crises driven by erratic precipitation, warming air, and farming mismanagement is coming sooner rather than later. At this critical time, society cannot avoid looking for ways to curb soil crises. We argue that now is the right time for science-based mitigation strategies and new insights to protect soils. We offer four research priority areas that society needs to address. Arresting and reversing the ongoing soil degradation are tantamount to safeguarding humanity and the environment. To the extent that we continue to treat soil crises as a problem for farmers only—not as a global challenge—we only escalate the scale to which the problem will grow in time and complexity.

Core Ideas: We present a semiautomated framework for large‐scale calibration of capacitance soil moisture sensors. Soil‐specific calibrations are needed for accurate moisture measurements in nearly all soil types. Transparent, traceable, and complete uncertainty estimates provided for entire approach. Technological advances have allowed in situ monitoring of soil water content in an automated manner. These advances, along with an increase in large‐scale networks monitoring soil water content, stress the need for a robust calibration framework that ensures that soil water content measurements are accurate and reliable. We have developed an approach to make consistent and comparable soil water content sensor calibrations across a continental‐scale network in a production framework that incorporates a thorough accounting of uncertainties. More than 150 soil blocks of varying characteristics from 33 locations across the United States were used to generate soil‐specific calibration coefficients for a capacitance sensor. We found that the manufacturer's nominal calibration coefficients poorly fit the data for nearly all soil types. This resulted in negative (91% of samples) and positive (5% of samples) biases and a mean root mean square error (RMSE) of 0.123 cm ³ cm ⁻³ (1σ) relative to reference standard measurements. We derived soil‐specific coefficients, and when used with the manufacturer's nominal function, the biases were corrected and the mean RMSE dropped to ±0.017 cm ³ cm ⁻³ (±1σ). A logistic calibration function further reduced the mean RMSE to ±0.016 cm ³ cm ⁻³ (±1σ) and increased the range of soil moistures to which the calibration applied by 18% compared with the manufacturer's function. However, the uncertainty of the reference standard was notable (±0.022 cm ³ cm ⁻³ ), and when propagated in quadrature with RMSE estimates, the combined uncertainty of the calibrated volumetric soil water content values increased to ±0.028 cm ³ cm ⁻³ regardless of the calibration function used.

Potential seed size in many crops including major cereals is determined during early seed developmental stages. However, the stage at which final seed size is determined in soybean (Glycine max [L.] Merr.) under field conditions is not known. Hence, this study was conducted with the main objective to assess seed growth dynamics under controlled and increased assimilate supply conditions during different seed filling periods using two maturity group soybean cultivars. Treatments consisted of a control, and a de-podding (pod removal) treatment at weekly intervals after the beginning of the seed filling stage up until physiological maturity. Only four to six pods were maintained per plant in de-podding treatments in order to provide a higher assimilate supply to remaining seeds. A higher assimilate supply until around the mid-seed filling stage increased unit seed weight in both the cultivars, indicating that the maximum seed size in soybean crops is determined during the mid-seed filling stage. The increase in seed weight under higher assimilate supply was associated with an extended seed filling duration and a uniform seed filling rate over a longer period. The results also suggested a possible source limitation during the early seed filling stage in soybean, indicating opportunities to improve its yield using supplemental inputs and other improved crop cultivation practices.

We examined how plant traits related to growth and resource use have evolved during hybrid speciation and specialization into stressful habitats. Two desert sunflower species of homoploid hybrid origin are endemic to habitats with lower soil nutrient levels than those of their ancestral parent species. We hypothesized that the hybrid species would exhibit greater tolerance to low levels of soil nutrients than their parental species. The 2 hybrid species, Helianthus anomalus and H. deserticola, and their parental species, H. annuus and H. petiolaris, were compared for plant traits and growth through reproduction under 3 nutrient levels in a greenhouse study. An additional seedling study compared species for maximum seedling relative growth rate under optimum conditions. The hybrid species did have greater tolerance of nutrient limitation than the parental species, demonstrated by a resistance to change in stem height and diameter growth across treatments. A similar trend was observed in total biom...