Delineation of Cumin (Cuminum Cyminum L.) Production Zone Beyond Boundaries in India Based on Climate Analogues, Soil Suitability and Rainfall Analysis


 Here, we attempted to identify ideal ecological niche for cumin cultivation in India in the future climate scenario by adopting an integrated approach of climate analogues and soil suitability. This will help policy makers for area expansion to generate more revenue as cumin has huge export potential. Climate analogues tool, a web-based tool developed by the Research Programme on climate change, agriculture and food security (CCAFS) helps to identify, connect and map sites with statistically similar climates across space and time. Efficient cumin production zones in India were identified based on relative spread index and relative yield index which were used as the input/reference site for finding the analogues sites. Rainfall and temperature were the main climatic variables used in the study under SRES A1B emission scenario. The results showed a total of 453 analogues sites (districts) identified by 14 reference sites used in the study. The analogues sites identified by the tool were further corroborated with the soil suitability of the location and refined analogues sites which included soil suitability for cumin cultivation (337 analogues sites out of 453) were identified. Rainfall trend analysis from the rainfall data of past 110 years indicated that analogues sites are showing the rainfall trend suited for cumin cultivation. This is the first report on the use of climate analogues tool to identify analogues sites with soil suitability and rainfall trend analysis of the identified analogues sites.


Introduction
India has an old history of cultivation of spices and takes bene t of being the largest producer, exporter and consumer of spices in the world. There are about 63 spices which are grown in India out of which 20 have been classi ed as seed spices. The major seed spices grown in India are cumin, fenugreek, coriander and fennel. Cumin (Cuminum cyminum L.) is an important spice commodity cultivated in a large area in arid and semi-arid regions of Rajasthan and Gujarat which have favourable soil and climatic conditions for its cultivation (Dubey et al. 2016) and India contributes to 70% of world's cumin production (Sharma et al. 2019). Study by Aiswath et al. (2016) indicated that out of 3564000 ha total study area in Rajasthan, 4% was moderately suitable for cumin cultivation with little limitations of soil and water whereas 74% was marginally suitable with limitation of soil and water. Gujarat and Rajasthan together contribute more than 90% of total cumin production in the country.
Cumin is a drought-tolerant, tropical, or subtropical crop. It has a growth duration of 100 − 120 days. Optimum temperature requirement is 20-30°C and it can grow in an annual rainfall range of 30 to 270 cms. Cumin is vulnerable to frost damage, especially at owering and early seed formation stages. The optimum growth temperature range is between 25 and 30° C. The crop can be grown well in soils having pH in the range of 6.5 to 8.5. However, for higher productivity of the crop and quality seed production, it is suggested that pH should be in the range of 6.5-7.5 with more than or equal to 0.6 per cent organic carbon and less than 10 per cent calcium carbonate content (Sharma et al. 2010). Cumin can tolerate even moderate salinity.
The Mediterranean climate is most suitable for its growth. Cultivation of cumin requires a long, hot summer of three to four months. At low temperatures, leaf colour changes from green to purple. High temperature might reduce growth period and induce early ripening. High  Indian agriculture as India is primarily an agricultural economy. This entails an urgent evaluation of risks for major food crops critical to food security (Brown,et al. 2008). Moreover, Kahrizi et al. (2011) reported that cumin yield and aroma are better under moderate climate compared to tropical climate, indicating that climate change in cumin growing regions of India is likely to decrease cumin yields and bring down aroma. Thus, it is essential to identify alternate sites for cumin production as the existing sites of cumin cultivation may become unsuitable due to climate change. A systematic and scienti c appraisal of natural resources especially climate and soils and their database are important pre requisites for augmenting cumin production on a sustainable basis. It is important that impact of climate change are studied to get prepared for maintenance of food security. Climate analogues is one simple tool to assess crop suitability as analogues locations are expected to have the future climatic conditions of the reference site which is favourable for the crop cultivation (Haussmann et al. 2012). Thus, the main objectives of the present study were to identify e cient cumin producing zones in India; to identify climate analogues sites for cumin growing in future (2020-2049); to analyse rainfall trend in climate analogue sites and to integrate soil suitability to climate analogues sites to have better prediction of suitable sites.

Collection of data
The o cial records on area and production of cumin in India were used to identify e cient producing zones as suggested by Kanwar (1972) and geo-referenced. The geographical co-ordinates of the selected reference sites were used for identifying the climate analogues against the search range of India. In this study, the analogues sites generated by the tool were based on the two climatic variables i.e. mean temperature and precipitation. We further selected the most suitable sites by incorporating soil information. The soil data available in the relevant sources like Central Ground Water Board and Central Research Institute for Dryland Agriculture (ICAR-CRIDA), Hyderabad were used to identify the soil type of analogues sites. Correlation and test of signi cance of correlation coe cient were conducted to analyse the rainfall trends using the past climate data (110 years) collected from Indian Meteorological Department, Pune, Maharashtra.

Identi cation of e cient production zones
The data on area, production and productivity of cumin in major cumin growing states of India viz. Gujarat and Rajasthan was collected from Spices Board, Govt of India and e cient cropping zones of cumin were identi ed based on relative yield index (RYI) and relative spread index (RSI) (Kanwar 1972) using the formula, RYI = Mean yield of a particular crop in a district (kg/ha) / Mean yield of the crop in the State × 100 RSI = Area of particular crop expressed as % of total cultivable area in the district / Area of particular crop expressed as % of total cultivable area in the State × 100 Five years data (2011-12 to 2015-16) on area and production of cumin were collected and it was averaged to calculate RYI and RSI using the above formula. Criteria used for e cient cropping zone is presented in Table 1. RYI and RSI were used to categorize each district in selected states into different zones of production and the categories are represented in Table 2.

Climate analogues tool
We used the climate analogues tool of Climate Change, Agriculture and Food Security (CCAFS) which allows to analyse data (identify analogue sites) in three temporal directions, i.e., (i) Future to Present, (backward direction), (ii) Present to Future, (forward direction), and (iii) Present to Present/Future to Future, (no temporal direction, i.e. none). In this study, we used forward direction to identify analogues sites based on the two climatic variables, monthly mean temperature and monthly precipitation.
The geographical co-ordinates of reference sites selected were input into the spatial analogues tool. For each site the inputs used were the ensemble of climate models for the Global Climate Model (GCM) and A1B, SRES for the emission scenario. In the analysis settings, Grid-analysis was selected to compare one single location with the whole geographic domain and output generated for any geographic region at any resolution will be equal to or above one km. Regarding similarity index, the CCAFS model calculates dissimilarity as a weighted Euclidean distance between the variables vectors for the reference (f). Based on this, target (p) scenarios were selected, and nally the optimum growing period of different regions were also input into the tool. The spatial analogues were determined on the basis of both, mean temperature and precipitation in case of climatic variables. Regions with high similarity were selected from the output grids produced by the tool and their geographical coordinates were derived. The analogues sites obtained using the tool were again classi ed on the basis of probability of matching i.e. highly likely (similarity value of 0.75-1) and moderately likely (similarity value of 0.5-0.75).

Mapping
ArcGIS (ESRI, India) was used for mapping. ArcMap allows exploring data within a data set, symbolizing features accordingly, and creating maps. This was used for giving boundaries to the climate analogues maps generated by the climate analogues tool and also for designing soil maps of the analogues sites.

E cient cropping zones of cumin in Gujarat
Cumin is cultivated in 21 districts of Gujarat in an area of 352657 ha with production of 307702 tons. The highest area of 95176 ha under cumin cultivation was observed in Surendranagar followed by 67710 ha in Banaskantha and 49082 ha in Patan. Similar trend was observed in production scenario of cumin in the state. Highest production was recorded in Surendranagar (98282 t) followed by Banaskantha (66793 t) and Patan (41411 t). Among the major producing districts, highest productivity of 1033 kg/ha was recorded in Surendranagar, well above the state productivity of 872 kg/ha. Banaskantha recorded 986 kg/ha and Patan 844 kg/ha.
Based on relative yield index and relative spread index, the different districts in the state are categorised as follows: e cient zone (Panchamahal); e cient zone with little year to year variation (Banaskantha, Jamnagar + Devbhumi, Porbandar, Patan, Rajkot + Morbi and Surendranagar); e cient zone with medium year to year variation (Kutch); e cient zone with great year to year variation (Bhavnagar, Junagadh, Kheda and Mehsana); not e cient zone with greater variation (Ahmedabad + Botad) and not e cient zone with little variation (Amreli, Anand, Gandhinagar and Sabarkantha + Aravalli) (Fig. 1).

E cient cropping zones of cumin in Rajasthan
Cumin is cultivated in 28 districts of Rajasthan with a total area of 443582 ha and a production of 164751 tons. The major districts cultivating cumin in the state are Barmer (122751 ha), Jodhpur (104199 ha), Jalore (83647 ha), Nagaur (47196 ha), Jaisalmer (23281 ha) and Pali (13465 ha). The highest production of 45180 t was recorded in district of Jodhpur followed by Jalore (37180 t) and Barmer (34897 t). The state productivity of cumin was 371 kg/ha while the highest productivity of 565 kg/ha was observed in Karauli and the least in Churu (220 kg/ha).
Based on relative yield index and relative spread index, the different districts in the state are categorised as follows: most e cient zone (Nagaur); e cient zone (Dausa, Dholpur, Dungarpur Jhunjhumn, Karauli and S Madhopur); e cient zone with little year to year variation (Barmer, Jaisalmer, Jalore and Jodhpur); e cient zone with medium year to year variation (Ajmer, Pali and Sirohi); e cient zone with great year to year variation (Baran, Bhilwara, Bikaner, Bundi, Chittorgarh, Jaipur, Jhalawar, Kota, Pratapgarh, Rajsamand, Sikar, Tonk and Udaipur) and not e cient zone with little variation (Churu) (Fig. 1).
3.3 Identi cation of climate analogues sites for cumin cultivation in future using CCAFS climate analogues tool

Reference sites
For identifying the climate analogues, the most important aspect is the selection of reference sites.
E cient districts which contributed to 90 % of country's cumin production and among e cient districts, those which contribute more than 10000 t production were selected as reference sites. This comprised of 14 districts from the states of Gujarat and Rajasthan (Table 3).  Fig. 2).

Soil suitability
As the soil data is not included in the tool, soil suitability data was also incorporated to the identi ed analogues sites. The results showed that out of 453 analogues sites identi ed by the tool, 337 sites showed the soil suitability for cumin cultivation (  (Fig. 2) reveals that the reference sites Jalore and Barmer have shown a wide spectrum of highly likely climate similarity sites. In the moderate range of climate similarity, same analogues sites are identi ed for all the reference sites covering the entire tracts of central and the northern plains of the country including Telangana. This is due to the fact that the climatic conditions of the places in these regions are not greatly altered. Southern and North Eastern parts fo India on the other hand were found unsuitable for extension of cumin cultivation except for some parts of central and northern Karnataka and Andhra Pradesh as precipitation and temperature of these places do not support cumin cultivation.
The uncertainty in climatic projections is mainly due to 'the non-linear character of the climate system, future emissions of greenhouse gases, internal variability, model parameterization etc. (Gornall et al. 2010). However, climate analogues approach could still be used as it provides valuable information on the climate which is very useful for strategic planning (Grenier 2013 Fig. 3) also to make climate analogues sites identi ed by the tool little more realistic.

Climate analogues with soil suitability
All types of soils are suitable for cultivation of this crop. However, sandy loam to medium heavy soils having plenty of organic material with better fertility status is most suitable. The soil should have better drainage facility because stagnated water and excessive moisture are very harmful for successful cultivation of cumin and such soils should be avoided. Soil suitability including desert soil, alluvial soil and some parts of black soil are identi ed as suitable among analogue sites obtained. The crop can be grown well in soils having pH in the range of 6.5 to 8.5. However, for higher productivity of the crop and quality seed production, it is suggested that pH should be in the range of 6.5-7.5 with more than or equal to 0.6 per cent organic carbon and less than 10 per cent calcium carbonate content (Sharma et al. 2010). Loam, clay loam, silty clay loam are highly suitable while massive clay and coarse sand are not suitable for cumin cultivation (Sharma et al. 2019). Based on the soil requirement for cumin cultivation, the soil maps obtained for analogue sites were analysed and the distribution of soil types of most of the analogues sites were found complementing the required range of pH of 6-8 and well drained texture of sandy to loamy. However, some of the climate analogues sites were found to have unsuitable soils for cumin cultivation. Out of 453 analogues sites identi ed by the tool, 116 sites were found to have unsuitable soil for cumin cultivation ( Table 4). Most of the analogues sites identi ed in the states of Chhattisgarh, Odisha, Jharkhand, Karnataka and Kerala have shown non-suitability of the soil as per the soil data of these states. By taking these unsuitable sites in to account, re ned map depicting only the climate analogues sites with soil suitability was prepared (Fig. 3). It is clear from the map that the central part covering Madhya Pradesh, Maharashtra, Telangana, northern parts covering Delhi, Uttar Pradesh, Punjab, Haryana and eastern parts covering Bihar and West Bengal are mostly suitable for cumin cultivation in future climate (2020-2049). Analogues sites could be helpful to identify matching sites for germplasm exchange for future adaptation (Chaudhary et al. 2016). This will help in planning for exotic germplasm collections targeting the most suitable analogues sites so as to step up the production and to meet the demands of domestic as well as export market.

Rainfall trend
Correlation analysis of rainfall trend revealed that more than half the number of existing sites invariably follow a positive trend of rainfall for cumin cultivation with signi cant positive trends for four sites. Contrarily, 22 sites showed negative trend in existing sites of which, 2 were found signi cant. Cumin grows and yields well under dry weather conditions and more than half of the existing sites are showing positive trend indicate that many of the existing sites are slowly becoming non-suitable for cumin cultivation as these sites are receiving more rainfall. Cumin requires comparatively less irrigation water (218 mm) than other tropical plants. Seed quality is affected if there is rainfall during the harvesting period (Rao et al., 2010). Cumin can be cultivated in rainfall and temperature ranges of 30 to 270 mm and 9 to 26 o C respectively. However, rainfall of 250 mm and a mean temperature of 13-22 o C during growing cycle are highly suitable (Sharma et al. 2019). Nimisha Agarwal and Anindya Sinha (2019) identi ed the future climate analogues of current wheat production zones in India based on CCAFS climate analogues tool. They compared the present and future predicted yields in analogues sites. In this study, among climatic parameters, only temperature was considered in the climate analogues tool. They opined that for comprehensive understanding, other factors such as soil type, rainfall etc. are also important. Our study addresses soil characters as well as rainfall trend of the analogues sites. This is the rst study as per our understanding which addressed the issue of soil character as well as rainfall trend of the analogues sites.
Thus, the present study employed CCAFS climate analogues tool to identify climate analogues of cumin. The analogues sites identi ed by the tool were further corroborated with the soil suitability of the location. Rainfall trend analysis of the existing and analogues sites indicated that existing sites are becoming less suitable while the analogues sites are showing the rainfall trend suited for cumin cultivation.

Declarations
Funding This research work was funded by National Initiative on Climate Resilient Agriculture (NICRA), ICAR-Central Institute of Dryland Agriculture, Hyderabad, India.

Authors contribution
Krishnamurthy, Kandiannan and Alagupalamuthirsolai contributed to the study conception and design and supervision, data collection and analysis were performed by Faras Bin Muhammed, Swetha Sudhakaran and Jayarajan. The rst draft of the manuscript was written by Swetha Sudhakaran, Krishnamurthy edited the draft and prepared the nal version after receiving the comments from all the authors. All authors read and approved the nal manuscript. Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors. Climate analogues of selected reference sites using CCAFS Climate analogues tool for cumin production in 2020 -2049 (Red indicates highly suitable and green moderately suitable) Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.

Figure 3
Climate analogues sites with suitable soils for cumin cultivation Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.