Accurate predictions of crop yield are critical for developing effective agricultural and food policies at the regional and global scales. We evaluated a machine-learning method, Random Forests (RF), for its ability to predict crop yield responses to climate and biophysical variables at global and regional scales in wheat, maize, and potato in comparison with multiple linear regressions (MLR) serving as a benchmark. We used crop yield data from various sources and regions for model training and testing: 1) gridded global wheat grain yield, 2) maize grain yield from US counties over thirty years, and 3) potato tuber and maize silage yield from the northeastern seaboard region. RF was found highly capable of predicting crop yields and outperformed MLR benchmarks in all performance statistics that were compared. For example, the root mean square errors (RMSE) ranged between 6 and 14% of the average observed yield with RF models in all test cases whereas these values ranged from 14% to 49% for MLR models. Our results show that RF is an effective and versatile machine-learning method for crop yield predictions at regional and global scales for its high accuracy and precision, ease of use, and utility in data analysis. RF may result in a loss of accuracy when predicting the extreme ends or responses beyond the boundaries of the training data.

Soil amendment with biochar is thought to confer multiple benefits to plants including induction of systemic resistance to plant pathogens. Pathogens in the genus Phytophthora cause damaging diseases of woody species throughout the world. The objective of this study was to test 1) whether biochar amendment induces resistance to canker causing Phytophthora pathogens; and 2) how this resistance is related to the amount of biochar amendment in two common landscape tree species: Quercus rubra (L.) and Acer rubrum (L.). Seedlings of Q. rubra and A. rubrum were planted in peatmoss-based potting mix uniformly amended with 0%, 5%, 10%, or 20% biochar by volume. Plants in each treatment group were stem wound-inoculated with an isolate of Phytophthora cinnamomi Rands (host: Q. rubra ) or P. cactorum (Leb. and Cohn) Schröeter (host: A. rubrum ) using standard agar-plug inoculation procedures. Amendment of potting media with 5% biochar reduced horizontal expansion of lesions in both hosts, whereas the same treatment significantly reduced vertical expansion of lesions in A. rubrum ( P < 0.05). In addition, 5% biochar resulted in a higher midday stem water potential in Q. rubra ( P = 0.066) and significantly greater stem biomass in A. rubrum compared with inoculated control plants (0% biochar, P < 0.05). Our results suggest that biochar amendment has the potential to alleviate disease progression and physiological stress caused by Phytophthora canker pathogens and there is likely an optimal level of biochar incorporation into the root media beyond which the effects may be less pronounced.

Essential nutrients, including carbohydrates, proteins, fats, vitamins, and minerals, are required for human health and development. Inadequate intake can negatively affect development and result in a wide range of adverse health outcomes. Rice, maize, and wheat provide over 60% of the world’s food energy intake. Atmospheric carbon dioxide (CO₂), water, nitrogen, and soil micronutrients are the basis of this plant material. Since 1850–1900, CO₂ concentrations have increased about 50%, with most of that increase since 1950. Higher CO₂ concentrations increase photosynthesis, which then increases plant biomass, but also alters the nutritional quality of wheat, rice, and other C3 plants. We review the possible impacts of rising CO₂ concentrations on human health, highlight uncertainties, and propose a research agenda to maintain the nutritional quality of C3 plants. We also synthesize options for addressing this critical challenge to nutritional safety and security. A complete research agenda requires addressing data and knowledge gaps surrounding plant biology and policy responses. Data on key nutrients are lacking, leading to a limited mechanistic understanding of the response of the plant ionome to elevated CO₂ concentrations. Regular data are largely missing on nutritional status and food safety in low- and middle-income countries, limiting assessments of the magnitude of the risks. Research opportunities to fill gaps in data and understanding include herbaria studies, field-based natural and manipulative studies, leveraging natural plant variability, and innovations in seed quality. Improved models of cereal crop nutritional quality can project the magnitude and direction of possible future challenges; incorporating the effects of climate change into those models can further improve their robustness. Transdisciplinary research involving at least ecologists, plant physiologists, economists, and experts in human nutrition is essential for developing a systems-based understanding of the potential impacts of rising CO₂ concentrations for human nutrition and the attendant consequences for achieving the sustainable development goal on food security.