Growing Degree Days Research Articles

Straw Mulching and Weather Conditions Affecting the Trade-Off Between Grain Yield and Agronomic Traits of Maize

Straw mulching (SM) plays an important role in promoting the grain yield (GY) of maize under no-tillage conditions. However, there is still a lack of deep understanding on the interactive impact of SM and weather conditions on agronomic traits and the contributions to GY. This study selected a cornfield in the North China Plain as the research object and set up a straw management experiment, including SM and no straw mulching (NSM). The GY and agronomic traits of maize from 2018 to 2020 were monitored, and the relationship of agronomic traits with GY and the weather conditions were analyzed. The results show that SM promoted maize GY by 20.44%. Straw mulching increased the plant height, ear diameter, and ear height by 8.43%, 1.99%, and 12.65%, respectively. A correlation analysis showed that the ear length and ear height were the main factors affecting maize yield. Ear length was significantly correlated with kernel numbers per ear in SM. Growing degree days, hot dry wind, and air temperature significantly affected kernel numbers per ear and plant growth. This study highlights the contributions of agronomic factors to maize GY under SM and variable weather conditions and is helpful to improve cropland management.

Changing climate risks for high-value tree fruit production across the United States

Abstract Climate change poses growing risks to global agriculture including perennial tree fruit such as apples that hold important nutritional, cultural, and economic value. This study quantifies historical trends in climate metrics affecting apple growth, production, and quality, which remain understudied. Utilizing the high-resolution gridMET dataset, we analyzed trends (1979-2022) in several key metrics across the U.S. – cold degree days, chill portions, last day of spring frost, growing degree days (GDD), extreme heat days (daily maximum temperature >34°C), and warm nights (daily minimum temperatures >15°C). We found significant trends across large parts of the U.S. in all metrics, with the spatial patterns consistent with pronounced warming across the western states in summer and winter. Yakima County, WA, Kent County, MI, Wayne County, NY—leading apple-producers—showed significant decreasing trends in cold degree days and increasing trends in GDD and warm fall nights. Yakima county, with over 48,870 acres of apple orchards, showed significant changes in five of the six metrics - earlier last day of spring frost, fewer cold degree days, increasing GDD over the overall growth period, and more extreme heat days and warm nights. These trends could negatively affect apple production by reducing the dormancy period, altering bloom timing, increasing sunburn risk, and diminishing apple appearance and quality. Large parts of the U.S. experience detrimental trends in multiple metrics simultaneously that indicate the potential for compounding negative impacts on the production and quality of apples and other tree fruit, emphasizing the need for developing and adopting adaptation strategies.

Climate data integration into wheat performance evaluation reveals large inter-varietal responses

Abstract There is an urgent need to adapt crop breeding strategies to boost resilience in the face of a growing food demand and a changing climate. Achieving this requires an understanding of how weather and climate variability impacts crop growth and development. Using the United Kingdom (UK) as an example, we evaluate changes in the UK agroclimate and analyse how these have influenced domestic wheat production. Here we quantify spatial and temporal variability and changes in weather and climate across growing seasons over the last four decades (1981-2020). Drawing on variety trial data, we then use statistical modelling to explore the interaction between genotype and agroclimate variation. 
We show that changes in the UK agroclimate present both risks, and opportunities for wheat growers, depending on location. From 1981-2020, in Wales, the West Midlands, large parts of the North West, and Northern Ireland, there was an overall increase in frost risk in early spring of 0.15 additional frost days per year, whilst in the East early frost risk decreased by up to 0.29 days per year. Meanwhile, over the period 1987-2020, surface incoming shortwave radiation during grainfill increased in the East by up to 13% but decreased in Western areas by up to 15%. We show significant inter-varietal differences in yield responses to growing degree days, heavy rainfall and the occurrence of late frost. This highlights the importance of evaluating variety-climate interactions in variety trial analyses, and in climate-optimised selection of crops and varieties by growers. This work provides guidance for future research on how climate change is affecting the UK agroclimate and resulting impacts on winter cereal production.

Effects of sprigging date and sprigging rate on establishment of two saltgrass lines

AbstractSaltgrass [Distichlis spicata var. stricta (L.) Greene], native to the western United States, is a dioecious, warm‐season halophyte. CO‐1 and AZCO‐1 are two elite inland saltgrass lines that have potential as a turfgrass and for revegetation use on saline sites. The objectives of this study were (i) to determine the effect of sprigging date, sprigging rate, and sprig storage time on the establishment of CO‐1 and AZCO‐1 in the field and (ii) to determine the accumulative growing degree day (GDD) requirements for saltgrass to establish adequate coverage (≥75%). Sprigging dates were 22 May and 19 June. Saltgrass rhizomes (sprigs) were harvested from existing field plots. Harvested saltgrass sprigs were stored in sealed plastic bags and kept in temperature below 30°C for 1 or 2 days. Sprig storage time (1 or 2 days) did not affect establishment. Saltgrass sprigged in May established adequate coverage (≥75%) by the end of September at all the rates tested (18, 27, and 54 metric t ha−1). For plots sprigged in June, only the high and medium sprigging rates established adequate coverage (≥75%) by the end of September. Plots sprigged in June using the low rate (18 t ha−1) failed to establish adequate coverage by the end of September. Regression analysis predicted that a sprigging rate of 23 t ha−1 was needed to achieve ≥75% coverage by the end of September for plots sprigged in June. The accumulated GDD to achieve adequate coverage was 1531 and 1703 for 54 and 27 t ha−1 sprigging rates, respectively.

Growing-degree-days (GDDs) in a uniform phenology scale (BBCH) for two walnut (Juglans regia L.) cultivars

ABSTRACT Descriptors are widely used for monitoring the phenology and pomology of plants. Among them, the BBCH (Biologische Bundesanstalt, Bundessortenamt und Chemische Industrie) scale is the most important. We evaluated the growth of ‘Chandler’ and ‘Persia’ walnut cultivars to create a BBCH descriptor for the crop, and estimate the growing-degree days (GDDs) of different growth stages. The GDDs (°C-days) were measured using 0°C as a base temperature (Tb) for male flowering and 5.5°C for other phenological stages in both cultivars. Growth stages were divided into eight principal stages, each with multiple substages. Stage 0 includes the bud sprouting, while stage 9 occurs when the leaves develop and the tree enters the dormancy. Both cultivars had a similar heat unit requirement at the bud quiescent stage (84 and 71°C-days for ‘Chandler’ and ‘Persia’, respectively); however, ‘Chandler’ needs higher GDDs accumulation to reach the harvest (3876°C-days compared to 3539°C-days for ‘Persia’). The results suggest that ‘Persia’ can be cultivated in colder areas at higher altitudes or latitudes compared with ‘Chandler’.

Assessment of sowing environment for wheat cultivars and evaluation of growing degree days for phenological stages in the Northwest Himalayan region of Himachal Pradesh

BackgroundThe date of sowing is a non-monetary input factor that plays a crucial role in field crop management. Based on the sowing time, management practices of crop production affect crop growth, development, and yield. Under varied environmental conditions, this factor may be useful in addressing low yields and combating/escaping stresses either due to diseases or due to any unfavourable environment.ResultsA field experiment was conducted during the rabi season of 2017–18 and 2018–19 to study the accumulated growing degree days (GDD) and performance of six wheat cultivars (HS 562, HD 2967, HD 3086, HI 1544, MACS 6222 and WR 544) under four sowing dates (5th November, 25th November, 15th December and 5th January). The study revealed that 5th November is the best date for sowing resulting in higher pooled grain yield of 4.85 Mg ha−1 and 3.94 Mg ha−1 at Bajaura and Malan, respectively. Significant reductions in the grain yield and yield attributes were observed when the date of sowing was set beyond 5th November. Among the cultivars tested, HS 562 gave a significantly higher pooled grain yield of 4.46 and 3.75 Mg ha−1 at Bajaura and Malan, respectively. Pooled data on physiological maturity revealed that variety HS 562 took the highest calendar days (168 days) and GDD (1573.42 °C days) to attain physiological maturity at Bajaura while at Malan HI 1544 and HD 3086 took the highest calendar days (156 and 155 days, respectively) and GDD (2055.41 and 2051.81 °C days, respectively) to attain their physiological maturity.ConclusionFrom the study, it can be concluded that the early date of sowing provides the crop with ample duration to accumulate growing degree days resulting in a higher accumulation of photosynthates resulting in significantly higher yield attributes and grain yield. Therefore, 5th November is recommended as the best time for sowing of wheat crop whereas the sowing must not be delayed beyond 25th November. HS 562 was superior among the cultivars and is recommended for Malan and Bajaura regions for attaining higher yield.

Cider Terroir: Influence of Regionality on Australian Apple Cider Quality

Understanding how regionality influences the key characteristics of cider will assist the industry to produce a premium and consistent quality product. Three dessert apple varieties were sourced from three (minimum) orchards per region from nine major growing regions across Australia over two seasons. Ciders produced from these apples were analysed for base quality characteristics, including total phenolic content (TPC), pH, total soluble solids (TSS) and titratable acidity (TA). Across both seasons, region had a significant influence on TPC, with the region model explaining approximately 25% of the variation in TPC. TSS and TA were significantly influenced by an interaction between variety and region, with the model accounting for approximately 60% and 75% of the variation, respectively, over both seasons. An interaction between variety and region influenced pH results in the first season, with only mean effects in the second season. A climate model was developed using average rainfall data and growing degree days (GDDs). Differences in climate accounted for most, but not all, of the regional variation observed in cider quality measurements. These results demonstrate that the apple growing region can significantly impact the resulting cider quality. Such findings are critical for supporting cider producers to make informed decisions when sourcing fruit.

Impacts of nitrogen (N), phosphorus (P), and potassium (K) fertilizers on maize yields, nutrient use efficiency, and soil nutrient balance: Insights from a long-term diverse NPK omission experiment in the North China Plain

Context or problemSoil nutrient deficiency is one of the significant challenges in grain production, particularly nitrogen (N), phosphorus (P), and potassium (K). These deficiencies not only reduce crop yields but also cause associated environmental issues, such as soil structure deterioration and ecosystem services diminution. ObjectivesThis research aimed to investigate the long-term effects of NPK fertilizers on soil nutrient properties and maize phenology, further on the grain yield, and to evaluate the nutrient use efficiency and soil nutrient balance under different fertilization managements. MethodsA long-term field experiment was initiated in 1990 in a summer maize field in the North China Plain, including five fertilizer treatments: CK (control), NP, NK, PK, and NPK. The soil nutrient properties, maize yields, crop nutrient uptake amount, nutrient recovery efficiency (NRE), nutrient harvest index (NHI), and soil nutrient balance were annually evaluated from 2005 to 2022. ResultsSignificant improvements in maize yields were found under NPK (9081 kg ha−1), NP (6426 kg ha−1), and PK (2668 kg ha−1) compared with CK (1809 kg ha−1) and NK (1656 kg ha−1). The yield increase was mainly attributed to: (1) enhancing in soil nutrient properties, such as soil organic carbon, soil total N (TN), available N (AN), total P (TP), available P (AP), and available K (AK), and (2) the shortened vegetative period, leading to greater sunshine hours (SH) and accumulative growing degree days (GDD) during the reproductive period. Furthermore, a random forest analysis quantified their importance to grain yield, showing that the edaphic factors (mainly SOC, TN, AK, AN, TP, AP, C:N, and N:P) explained a much greater proportion of yield variation compared with phenological factors (mainly GDD during tasseling and physiological maturity stages, and SH during tasseling stage). Additionally, the significantly higher response ratio of both N and P to NRE and NHI implied that N and P fertilizers having a more pronounced impact on improving nutrient use efficiency than K fertilizer. In terms of soil nutrient balance, a most relative soil nutrient balance was detected under NPK treatment, avoiding either substantial nutrient depletion or accumulation under any nutrient deficiency conditions. ConclusionsSoil deficiencies in N and P had more severe impacts on maize yields and nutrient use efficiency compared with K deficiency. Additionally, a balanced NPK fertilizer regime effectively managed soil nutrient balance. Implications or significanceThese findings elucidate the roles of N, P, and K fertilizers in maize production and soil nutrient conditions from a long-term field experiment, which could provide valuable insights for optimizing fertilization management strategies.

Effect of Sowing Dates and Wheat Cultivars on Agro Meteorological Indices of Wheat under Conditions of North-western Himalayas, India

Climate change in recent times have presented a scenario of elevated susceptibility of wheat to rising temperatures. Agro-meteorological indices can present a scenario of variable response of wheat to diverse conditions. A field investigation was conducted in rabi season of 2016-17 at Research farm, Department of Agronomy, CSK Himachal Pradesh Krishi Vishvavidyalaya, Palampur to evaluate the influence of sowing dates and wheat cultivars on agro-meteorological indices such as growing degree days, photothermal units, Helio thermal units and phenothermal index of wheat crop. The field investigation involved five sowing dates (15th October, 30th October, 15th November, 30th November and 15th December) and wheat cultivars (HPW-349 and HPW-155) which were studied in a factorial randomized block design with three replications. The results of the investigation revealed that timely sown crop i.e., on 15th October recorded the highest values for agro-meteorological indices for both the wheat cultivars such as growing degree days, Helio thermal units, photothermal units and phenothermal index across various wheat development stages such as complete emergence, crown root initiation, tillering, ear emergence and physiological maturity. Therefore, timely sowing of wheat by 15th October was concluded to be the best for optimized agro-meteorological indices such as growing degree days, photothermal units, Helio thermal units and phenothermal index under conditions of North-Western Himalayas.

Monitoring Crop Condition at Gield Scales and at a Daily Time Step Using Synthetic Aperture Radar (SAR)

Operations that rely on optically-based Normalized Difference Vegetation Index (NDVI) to track crop productivity, are negatively impacted by cloud cover. In this research, parameters from Synthetic Aperture Radar (SAR) imagery were calibrated to NDVI with the targeted outcome to integrate SAR into Canadian crop monitoring services. Data from fully polarimetric RADARSAT-2 and dual-polarization Sentinel-1B imagery were calibrated to Sentinel-2 NDVI. Random Forest Regression (RFR) and Least Squares Boosting (LSBoost) were tested to calibrate SAR to NDVI (SARcal-NDVI) for six crops (corn, canola, soybeans, wheat, oats and barley). RADARSAT-2 provided the best fit with R2 exceeding 0.84 for canola, 0.87 for wheat and 0.90 for corn and soybeans. Correlations were lower for oats (R2 of 0.72–0.77) and barley (R2 of 0.43–0.64) due to a limited number of fields. Although a global model yielded lower correlations (R2 of 0.80), this model would be easier to implement into operations. Total power, the first and second eigenvalues and VH backscatter were important in reducing model error. The SARcal-NDVI and Growing Degree Days were then integrated into a Crop Structure Dynamic Model to produce daily estimates of crop condition, at field scales. The next step is to test if these daily estimates of crop condition can improve crop yield forecasting for the Canadian agriculture sector.

Climate change is likely to favour polyvoltine and invasive insect species, leading to more damage in the mid-latitude vineyards of Neuchatel

Climate change has major impacts on viticultural ecosystems worldwide, affecting wine production. Apart from direct impacts, the increase in temperature during the development season is likely to favour insect species, including polyvoltine ones, leading potentially to more damage in the vineyards. In this study, we examined the extent to which changes in mean temperature over the development season (March through September) can potentially increase the voltinism change the phenology and influence the reproduction of pest species in the vineyard area of Neuchatel (Switzerland). We first analysed long-term daily mean temperature data from 1970 to 2022 at the meteorological station of Neuchâtel. Then we used two climate scenarios (RCP4.5 and RCP8.5) to analyse daily mean temperature during the period 2023–2099. For both of these periods, we computed the number of growing degree days (GDDs) above 10 °C, as it is the base development temperature for many polyvoltine pest species. We then used specific bioclimatic models for two major pest species, namely the European grapevine moth (Lobesia botrana) and the American grapevine leafhopper (Scaphoideus titanus) to compare the current and future suitability of these two species to the air temperature conditions in Neuchâtel. Our results show an increase of about 425 GDDs since 1970 (+85 GDDs per decade). According to our models, values will continue to rise during the next decades, with a trend ranging from +28 GDDs per decade (RCP4.5) to +100 GDDs per decade (RCP8.5). This could lead to additional generations of polyvoltine pest species. A third annual generation can be expected in one year out of four for the European grapevine moth by the middle of the 21st century. While temperature conditions are currently moderately favourable for the American grapevine leafhopper, they are predicted to become highly favourable by the middle and the end of the century under both scenarios. These trends mean that climate change is likely to increase pest damage risks in the vineyards of Neuchatel in the future. Pest regulation will remain crucial in limiting major impacts on wine production.

Unveiling Phenotypic and Environmental Dynamics: Exploring Genetic Stability and Adaptability of Faba Bean Cultivars in Norwegian Climates

ABSTRACTThis study evaluated 22 spring‐type faba bean cultivars in the main areas for cultivation of faba bean in Norway to assess the variation of 14 faba bean traits due to cultivar (G), environment (E), and their interaction (G × E), and to assess their stability across environments by using the additive main effects and multiplicative interaction (AMMI) analysis and coefficient of variation (CV). Significant G, E, and G × E effects were found for most traits, with environment accounting for much of the variance in yield and the growing degree days (GDD) to different developmental stages. Yield was highly correlated with thousand kernel weight (TKW) and GDD to BBCH 89 (maturation). The stability of the cultivars was studied for yield, TKW, and GDD to BBCH 89. Stability analysis using the AMMI stability value, yield stability index, CV, and the average sum of ranks identified Birgit, Stella, Bobas, and Macho as the most stable high‐yielding cultivars across environments, achieving a mean yield of 6–6.4 tons ha−1. Bobas, Macho, Stella, and Yukon had the most stable TKW (612–699 g) and Bobas, Capri, Trumpet, and Vertigo were the most stable regarding GDD to BBCH 89 (1257°C days, with a base temperature of 5°C). These stable cultivars can be utilized in breeding programs to achieve high and stable faba bean yield in the main growing areas of Norway and other Nordic‐Baltic countries.

Hedging irrigated maize crop yields using temperature derivatives in Malawi

Agriculture production yield varies with weather changes. This causes farmers incur loses. For instance, extreme temperature leads to low maize yield. This study describes incomplete temperature weather derivatives in agriculture markets and applies risk management hedging techniques. It focuses on hedging crop yield against extreme temperatures during irrigation, farming which is done without greenhouse. This study's primary goal is to hedge irrigated maize crop yields using temperature derivatives. This is achieved firstly by modelling a daily average temperature stochastical model. Then, deriving statistical properties of the model based on 1990–2020 Kasungu District Temperature historical data. Lastly, pricing temperature derivatives to hedge maize crop yield. This study uses 1990–2020 Kasungu District Temperature historical data. Then a stochastically Ornstein-Uhlenbeck process with the time-varying speed of reversion, seasonal mean, and local volatility that depends on the local average temperature was proposed. Based on the average temperature model, down and output barrier option pricing models for average temperature and growing degree day (GDD) are applied. The study results shows that when the GDD is above the barrier level the barrier option does not knock out. Hence gives the holder the right to buy the underlying asset since it does not reach or fall below a predefined level over the option's lifetime. If the GDD does not exceed the barrier level, then the farmer will not have to pay the premium because the option is invalid. On the same note, the farmer will have to exercise his right by paying the premium of calculated premium when the GDD exceeds the barrier level. In return for this, the farmer gets paid off which happens to be the difference between GDD and barrier multiplied $1. In line with Malawi's 2063 Millennium Development Goals (MDGs), this study acts as an eye opener for the government to put a policy on whether derivatives should be practised in our country hence, increase cash holding by improving the situation of the farmer and country.

Drought alters the physiological quality of runner-type peanut seeds during seed formation

Sub-optimal water supply during crop development, especially during peak flowering and pod filling, affects the quality of the produced seeds, generally resulting in poor seed quality. The goals of this study were to identify the acquisition pattern of physiological components in peanut seeds as well as to assess the impact of drought during peanut seed development on its physiological quality. The research was conducted at the USDA-ARS National Peanut Research Laboratory in Dawson, GA for three consecutive years (2019, 2020, and 2021) using field conditions under two water regimes, well-watered control and drought stress. Rainout shelters were used to prevent rain in the drought-stressed block for 30 d, starting 80 d after planting. The well-watered block received supplemental irrigation when soil water potential reached -40 kPa. Peanut pods from the cultivar Georgia-06G were harvested at 2500 growing degree days, and the peanut maturity profile board was used to classify the pods into different maturity classes. Germination, vigor, desiccation tolerance (DT), and longevity tests were performed on seeds from each maturity class and both water regimes. The acquisition pattern for the physiological components of seed quality was developed for seeds grown under well-watered and drought conditions. Maximum germination occurred in ‘brown 1’ and ‘brown 2’ under drought and well-watered conditions, respectively. Both water regimes reached maximum vigor in the 'brown 1'; however, under well-watered conditions, vigor had a rapid decline after ‘brown 1’ while under drought stress, the decline in vigor was slower. Maximum DT was achieved between ‘orange’ and ‘brown 1’ under drought conditions, whereas under well-watered conditions, maximum DT was achieved between ‘brown 2’ and ‘black 1’. Seeds from immature classes had lower capacity to be stored compared with mature seeds. Overall, drought stress promoted greater physiological quality in the peanut seeds than the well-watered treatment. Maximum physiological quality was achieved in the transition from ‘orange’ into ‘brown 1' under drought conditions, and in the transition from ‘brown 2’ to ‘black 1’ class under well-watered conditions. Also, drought stress preserved seed quality for a longer period.

Warm Index and Growing Degree Days as Indicators of Climate Changes for Growth of Quercus Eagilops and Pistacia Khinjuk Trees in the Dohuk Region

Warm Index and Growing Degree Days as Indicators of Climate Changes for Growth of Quercus Eagilops and Pistacia Khinjuk Trees in the Dohuk Region

Genetic and environmental drivers of legume cover crop performance: Hairy vetch

AbstractAmong 50 environments in the United States, we screened 35 hairy vetch (Vicia villosa Roth.) lines for traits of interest to cover cropping. We analyzed the influence of genotype, environment, and the genotype‐by‐environment interaction (G × E) on biomass, vigor, winter survival, emergence, flowering time, and nitrogen fixation. To explore how environments and G × E impacted each trait, we associated environment predictions and G × E loadings with weather and soil parameters. Environment had the largest influence on all traits, representing more than half of the variance. Environment predictions were significantly associated with weather and/or soil parameters for each trait. Biomass was associated with growing degree days, winter survival with freezing degree days without snow cover, growth stage with shortwave radiation, and emergence with soil texture. The G × E interaction was larger than genotypic variance for all traits except for winter survival and flowering time. The G × E interaction loadings were associated with soil sand content for biomass, air temperature for fall vigor and emergence, and snow cover for winter survival. Although it represented the smallest proportion of total variance, genetic effects were significant for all traits except for emergence, Ndfa, %N, and C:N. New hairy vetch breeding lines were superior to all commercially available lines for biomass and winter survival. Biomass harvest timing did not significantly change line rank, indicating that top‐performing lines can be used in diverse management systems. To select for high nitrogen contribution to subsequent crops, breeding programs can indirectly select for biomass rather than expensively evaluating symbiotic nitrogen fixation.

Remote Sensing Detection of Growing Season Freeze-Induced Defoliation of Montane Quaking Aspen (Populus tremuloides) in Southern Utah, USA

Growing season freeze events pose a threat to quaking aspen (Populus tremuloides Michx.), leading to canopy defoliation, reduced vigor, and increased mortality, especially for declining montane populations western North America. Detecting the spatial distribution and progression of this damage is challenging due to limited in situ observations in this region. This study represents the first attempt to comprehensively resolve the spatial extent of freeze-induced aspen canopy damage in southern Utah using multispectral remote sensing data. We developed an approach to detect the spatial and temporal dynamics of freeze-damaged aspen stands, focusing on a freeze event from 8–9 June 2020 in southern Utah. By integrating medium- (~250 to 500 m) and high-resolution (~10 m) satellite data, we employed the Normalized Difference Vegetation Index (NDVI) to compare post-freeze conditions with historical norms and pre-freeze conditions. Our analysis revealed NDVI reductions of 0.10 to 0.40 from pre-freeze values and a second flush recovery. We introduced a pixel-based method to evaluate freeze vulnerability, establishing a strong correlation (R values 0.78 to 0.82) between the onset of the first flush (NDVI > 0.50) and the accumulation of 100 growing degree days (GDD). These methods support the potential for retrospective assessments, proactive forest monitoring, and forecasting future risks.

Four decades in the vineyard: the impact of climate change on grapevine phenology and wine quality in northern Italy

The wine sector, among the most profitable agricultural segments, has been markedly affected by the ongoing climate change impacts, such as warmer climate conditions with higher frequency of extreme temperatures and a trend of decreasing precipitation. All this results in higher evaporative demand and therefore higher occurrence of water stress events leading to advancement of temperature-sensitive phenological stages (e.g., budburst and ripening). Such negative effects eventually affect berry development and quality, especially in historically valuable viticultural areas, forcing winegrowers to work within a compressed harvest period to maintain wine typicity. In this work we examined the relationship between environmental variables (air and soil temperature, relative humidity, precipitation, and solar radiation), phenology, berry, and wine quality for the two varieties (Chardonnay and Teroldego) in Trentino Alto-Adige/South Tyrol (Italy) over 36 years. Huglin Index (a bioclimatic heat index), growing degree days (measure of heat accumulation), and overall mean temperature showed linear increase (p < 0.001) in the last years, while no variations were recorded for precipitations. Despite no major effects being observed for phenological interval lengths, the onset of most of the phenological stages for both varieties had significantly (p < 0.001) advanced. However, i) early budburst pushed the budburst-flowering interphase by -1.2 days every two years toward putative colder periods with increased late frost probability and potential slower phenological progression towards flowering, and ii) early veraison shifted the veraison-ripening interphase by 0.25 day per year into warmer periods that oppositely impose faster phenological advancement. Hence, a substantial equilibrium in the seasonal growing length over years was maintained. Potential carry-over effects from the previous season were observed, particularly associated with heat requirements to unlock early phenological events, raising additional concerns on the additive effects of climate change to viticulture. Generally, white wine quality increased (p < 0.05) over the years, while red and sparkling wines remained unaffected. This was putatively related to accurate harvest date decision-making dictated by berry quality parameters: sugar-to-acidity ratio for Chardonnay and bunch sanitary status for Teroldego. Overall, this work provides evidence of the dynamics involved in climate change, and, to our knowledge, its overlooked effects on viticulture, thus providing new insights that can contribute to further developing adaptive strategies.

Optimizing ethephon application timing for ‘Meyer’ zoysiagrass seedhead suppression

AbstractZoysiagrass (Zoysia spp. Willd.) is a desirable, low‐input turfgrass species used on golf courses. However, prolific zoysiagrass seedhead production in the spring can increase golf course maintenance costs and reduce aesthetics. Previous research demonstrates that a single autumn ethephon application can suppress zoysiagrass seedhead production the following spring, but the optimum application timing is not well‐defined. The objective of this research was to determine the optimum window for an effective ethephon application for ‘Meyer’ zoysiagrass seedhead suppression. Small‐plot field research was conducted in Indiana, Kansas, Arkansas, and Tennessee. Seedheads were suppressed up to 99% depending on application timing. In Indiana, applications made on September 19 provided 99% seedhead suppression. In Kansas, applications between August 30 and September 18 yielded >64% seedhead suppression. In Arkansas, applications between October 3 and October 17 yielded >52% seedhead suppression. In Tennessee, applications between September 19 and October 23 provided >78% seedhead suppression. Applications made outside these windows resulted in more seedhead production at each respective location. Interestingly, optimum application timing was approximately 2 weeks later in Arkansas and Tennessee compared to Indiana and Kansas. Using growing degree days, a nonlinear Gaussian model was fit to predict the optimum ethephon application timing. In addition to data from this research, the proposed model accurately predicted observed zoysiagrass seedhead suppression in previously published research. This research better characterizes the optimum autumn application timing for Meyer zoysiagrass seedhead suppression across the transition zone.

455 Evaluating the effect of a phenology-based timeline on the interpretation of enteric methane emission results

Abstract The methodology of analyzing methane emissions in cattle grazing native rangeland is imperative for producing reliable and repeatable estimations of total enteric emissions on an individual and herd basis. However, due to seasonal differences in climate from year to year, there are distinct differences in forage biomass availability and nutrient composition on extensive rangelands. Thus, our objective was to evaluate the differences in methane emissions using phenological forage phases compared with specific time periods. Yearling Angus steers (n = 127) were allocated to one of six pastures grazed from June to September (2023) at the South Dakota State University Cottonwood Field Station (Cottonwood, SD). Each pasture was equipped with a GreenFeed (C-Lock Inc., Rapid City, SD) pasture system to measure individual animal CH4 emissions. A subset of CH4 data from two cool-season-dominated pastures were aggregated from the overall study. We used two methods to segment CH4 by either 1) month (June, July, August) or 2) phenology (vegetative, reproductive, and senescence) to derive average CH4 (gּ animalּ -1ּ d-1) for each period. Western wheatgrass (WWG), a cool-season native, was used as a proxy for cool season grass development. On May 28th, 2023, the growing degree days (GDD) reached 632, representing the 3.5 leaf stage. WWG has been documented to reach maturity at approximately 1,100 GDD, which occurred on June 20th, 2023. Nutrient content of the forage (i.e., lignin) was used to approximate the start of senescence on August 11th. These developmental markers created estimates of the vegetative, reproductive, and senescence periods within our emissions data. Differences in enteric emissions for each approach were analyzed using a linear mixed effects model in R, and post-hoc contrast between methods was assessed using the lsmeans package. There were no statistical differences in CH4 by month (P > 0.05), and the means for June, July, and August were 217, 214, and 211 ± 4, respectively. By phenological phases, there was a difference (P < 0.05) between maturity and senescence, with means for vegetative, reproductive, and senescence as 214, 219, and 206 ± 4, respectively. Methane intensity (gּ animal-1ּ d-1) per period was then multiplied by the number of days in each month or phase to estimate total emissions for the entire grazing season (86 d). The monthly approach totaled 18,383 g CH4 per animal, while phenology totaled 18,504 g for the grazing season. This is a difference of 0.654% between the same data segmented by month or by phenology. Therefore, because of the dynamic nature of forage and cattle production, it is likely that accounting for phenology will provide greater clarity for GHG on rangeland systems rather than arbitrary periods of time and will require the use of dynamic models to handle the complexity of enteric emissions of grazing animals.