Geospatial Assessment of Chilling Requirements for Temperate Fruit Cultivation in Meghalaya, India
Abstract
Chilling hour (CH) accumulation is a critical climatic factor influencing dormancy release and flowering synchronization intemperate fruit crops. In this study, the spatial variability of chilling hours across Meghalaya, a northeastern hill state of India, has been assessed to evaluate the agro-climatic suitability for seven temperate fruit crops: apple, apricot, kiwi, persimmon, blueberry, peach, and walnut. Using ERA5-Land hourly gridded temperature data (9 kmresolution), average annual CHaccumulation was calculated over a 20-year period (2003–2023). The state was stratified into seven chilling hour zones based on cumulative CHthresholds relevant to crop-specific chilling requirements, determined in consultation with the Department of Horticulture, Government of Meghalaya.
Results revealed that 55.33% of the state receives <100 CHannually, rendering these areas unsuitable for most temperate crops. However, higher-elevation districts such as West Khasi Hills and East Khasi Hills exhibit favorable chilling regimes, supporting the potential cultivation of low-and moderate-chill crops. Suitability analysis indicates that peach (CH >100) has the highest spatial suitability (45.25%), followed by blueberry (150–600 CH; 33.04%), kiwi and persimmon (CH >200; 28.98% each), apple and apricot (CH >300; 21.52% each), and walnut (CH >600; 4.00%).
The study provides the first comprehensive chilling hour-based agro-climatic zoning for Meghalaya and presents a scalable framework for site-specific temperate horticultural planning in subtropical highland regions. The findings support the horticulture department of the state in decision-making for varietal selection, land-use allocation, and horticultural diversification under changing climate scenarios.
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Introduction
Chilling requirements are a critical factor in the successful cultivation of temperate fruit crops. These requirements refer to the cumulative number of hours during which temperatures remain between 0°C and 7.2°C (32°F to 45°F) during the dormant period of deciduous fruit trees. This cold exposure is essential for breaking dormancy and ensuring proper flowering and fruiting in the subsequent growing season. In India, varying climatic conditions across regions influence the accumulation of chilling hours, thereby affecting the viability of temperate fruit cultivation.
The concept of chilling requirements has been essential for temperate fruit cultivation. Weinberger (1950) first emphasized the need for adequate winter chilling to ensure successful bud break indeciduous fruit trees. Since then, several models have been developed to estimate chilling accumulation, including the Chilling Hours Model (CU Model), the Utah Model, and the Dynamic Model (Fishman et al., 1987), each varying in their sensitivity to temperature fluctuations and regional adaptability. Globally, chilling hour mapping has gained importance in light of climate change, which has led to significant reductions in winter chill in traditional temperate fruit-growing regions (Luedeling et al., 2009). For instance, studies in California, Spain, and Chile have documented how declining winter chill affects both the geographical range and productivity of temperate fruit crops. To address this, researchers have increasingly turned to gridded climate datasets and geospatial tools for assessing chilling patterns at regional and sub-regional levels (Campoy et al., 2011).
In the Indian context, the Himalayan states—particularly Himachal Pradesh, Jammu & Kashmir, and Uttarakhand—have been focal points of research on chilling hour distribution and its impact on apple and pear cultivation (Singh & Pal, 2014). Traditional high-chill varieties of apples, pears, and plums thrive well in the Himalayan regions, due to the ample accumulation of chilling hours. For instance, studies in Himachal Pradesh have reported chilling hours ranging from 779 to 1,155 hours, depending on the specific location and microclimate (Conversely, in the subtropical plains of Punjab, Haryana, and Uttar Pradesh, the accumulation of chilling hours is significantly lower, ranging between 150 to 350 hours (Tyagi et.al, 2022). This variation necessitates the selection of appropriate cultivars suited to the local chilling conditions. However, in the Northeastern Region (NER), particularly Meghalaya, very few studies have explored the application of chilling-based agro-climatic zonation for temperate fruit crops.
Meghalaya, a state located in the northeastern hill region of India, is characterized by varied elevations, topographic complexity, and a subtropical highland climate, which together create microclimatic conditions suitable for diversified horticulture. While traditionally dominated by crops suited to humid subtropical environments, interest in cultivating temperate fruits has grown due to rising market demand and favorable high-altitude pockets. However, systematic agro-climatic zoning based on chilling hour accumulation is lacking in the region. Most decisions related to temperate crop cultivation are based on elevation alone, overlooking the temporal and spatial variation in actual chilling accumulation.
Earlier assessments in Meghalaya focused largely on altitude-based suitability, rainfall, slope and soil characteristics for horticultural development (Borthakur et al., 2015, NESAC, 2021). While useful, such approaches lack temporal climate resolution. Recent advancements in remote sensing and the availability of reanalysis datasets like ERA5 have opened opportunities for high-resolution agro-climatic modeling. Studies utilizing ERA5-Land data in Mediterranean and South American regions have demonstrated its utility inaccurately estimating chilling accumulation over complex terrains (de Melo-Abreu et al., 2004; Luedeling & Brown, 2011).
Despite these advancements, a gap remains in applying these tools in the Northeast Indian context. Moreover, crop-specific chilling thresholds must be localized, as cultivars and growing conditions vary widely. By integrating ERA5-Land temperature data with chilling hour models and expert inputs from the Meghalaya Horticulture Department, this study presents a novel, region-specific approach to temperate fruit crop planning.
Conclusion
This study provides a comprehensive geospatial assessment of chilling hour distribution and its implications for temperate fruit cultivation in Meghalaya. The analysis reveals that over half of the state (55.33%) falls under the very low chill zone (<100 CH), rendering it unsuitable for most traditional temperate fruits. Only about 13.9% of the total area receives more than 400 chilling hours, confining the cultivation of high-chill crops such as apple, apricot, and walnut to a few high-altitude pockets. Conversely, low-to moderate-chill crops such as peach, blueberry, kiwi, and persimmon show broader adaptability, particularly in mid-altitude zones. The inverse relationship between chilling requirement and suitable area underscores the importance of selecting crop varieties based on localized climatic conditions. District-wise analysis identifies West Khasi Hills and East Khasi Hills as the most promising regions for temperate horticulture, with both low-and high-chill zones present. Ri Bhoi and West Jaintia Hills offer moderate potential, while East Jaintia Hills and SouthWest Khasi Hills are less suitable due to inadequate chilling accumulation.
Strategic crop selection, focusing on low-chill cultivars and site-specific planning, will be essential to realize the temperate horticulture potential in Meghalaya undercurrent and future climatic conditions. The successful introduction and cultivation of low-chill temperate fruit varieties in Meghalaya highlight the potential for expanding horticultural activities in the region. Continued research and development, along with farmer training and support, are essential to optimize cultivation practices and improve yields. By leveraging the state'sunique agro-climatic conditions and adopting suitable cultivars, Meghalaya can enhance its temperate fruit production, contributing to agricultural diversification and economic growth.
