Climate change is predicted to shift temperature regimes in most agricultural areas with temperature changes expected to impact yields of most crops, including rice. These temperature-driven effects can be classified into point stresses, where a temperature event during a sensitive stage drives a reduction in yield, or seasonal warming losses, where raised temperature is thought to increase maintenance energy demands and thereby decrease available resources for yield formation. Simultaneous estimation of the magnitude of each temperature effect on yield has not been well documented due to the inherent difficulty in separating their effects. We simultaneously quantified the magnitude of each effect for a temperate rice production system using a large data set covering multiple locations with data collected from 1995 to 2015, combined with a unique probability-based modeling approach. Point stresses, primarily cold stress during the reproductive stages (booting and flowering), were found to have the largest impact on yield (over 3 Mg/ha estimated yield losses). Contrary to previous reports, yield losses caused by increased temperatures, both seasonal and during grain-filling, were found to be small (approximately 1-2% loss per °C). Occurrences of cool temperature events during reproductive stages were found to be persistent over the study period, and within season, the likelihood of a cool temperature event increased when flowering occurred later in the season. Short and medium grain types, typically recommended for cool regions, were found to be more tolerant of cool temperatures but more sensitive to heat compared to long grain cultivars. These results suggest that for temperate rice systems, the occurrence of periodic stress events may currently overshadow the impacts of general warming temperature on crop production.

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Autoclaved‐citrate extractable (ACE) soil protein is included in some soil health assessments as a biological indicator. Furthermore, soil protein contents may be related to the ability of a soil to make nitrogen (N) available for plants by mineralization. The main objective of this study was to evaluate the correlation between ACE protein and potential net N mineralization in undisturbed soil cores from 57 fields in California under annual crops. Total N in the soils ranged from 0.65 to 12.5 g kg−1, and the sites represented eight Soil Taxonomy orders. Soil ACE protein concentrations ranged from 1.0 to 45.2 g kg−1 soil. Although the correlation between ACE protein and potential net N mineralization was positive, ACE protein explained only 21% of the variability in potential net N mineralization across all sites, which was less than total N. Under the assumption that proteins contain 16% N, ACE protein‐N accounted for 28% of total N across all sites. However, in some soils with a high total N content, ACE protein accounted for up to 67% of total N. Because autoclaving is expected to denature some proteins, these values seem very high and are likely caused by the interference of coextracted humic substances. Our results do not suggest that ACE protein is a better predictor of potential net N mineralization than total soil N, which may be at least partly due to an apparent interference of coextracted humic substances with the protein assay. Core Ideas ACE protein concentrations ranged from 1.0 to 45.2 g kg−1 soil. ACE protein and N mineralization were positively correlated (r = 0.46). The correlation was weaker than between N mineralization and total soil N. Co‐extracted humic substances appear to interfere with the protein assay.

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