E3S Web of Conferences 559, 01015 (2024) https://doi.org/10.

1051/e3sconf/202455901015
ICSTCE 2024

Impact of Climate Fluctuations on Paddy Yield:

A Case Study in Kollengode Village, India
K. R. Sreeni1 and Nirmala Vasudevan1*
1 Department
of Physics, School of Physical Sciences,
Amrita Vishwa Vidyapeetham, Amritapuri, India

Abstract. Paddy cultivation, a vital source of rice for billions globally,

faces numerous challenges, including water scarcity, pest and disease
outbreaks, soil degradation, and changing weather patterns. This study
investigates the factors contributing to declining paddy yield in Kollengode
village, located in Kerala State, south India, to inform strategies for
ensuring resilient rice production in vulnerable regions. Over the past two
years, Kollengode has witnessed a two-week delay in monsoon arrival,
prompting adjustments in traditional agricultural practices, such as a shift
in seed sowing time. The study examines how factors like rainfall patterns,
temperature variations, and agricultural practices influence paddy yield
decline. Through analysis of climate data, soil properties, and farmer
interviews, the findings reveal a significant decrease in rainfall during the
crucial growing season, likely contributing to the observed yield decline.
Furthermore, rising minimum temperatures suggest a potential decrease in
diurnal variation, which could—based on existing literature—impact rice
plant respiration and yield potential. This research highlights the
vulnerability of agricultural practices in the region to changing weather
patterns and emphasises the need for adapting cultivation strategies to
ensure long-term sustainability. The findings can inform local water
management practices and guide the development of climate-resilient
agricultural solutions for paddy cultivation in Kerala.

Keywords. Agriculture, paddy yield, rice cultivation, rainfall, temperature,

Kollengode, Palakkad, Kerala, India.

1 Introduction
Rice is the world’s most widely consumed crop, providing sustenance for nearly half of the
global population [1]. As the leading exporter of rice, India plays a crucial role in global
food security [2]. Rice cultivation thrives under diverse climatic and soil conditions; thus it
is grown in almost every state of India [3, 4]. In the south Indian state of Kerala, Palakkad
district cultivates rice on over 300 km2 of land, contributing significantly to the state’s
agricultural output with an annual yield of around 200,000 tons [5].
Kollengode is one of the major agricultural villages in Palakkad, where wetland rice
cultivation plays a vital role in supporting the livelihoods of the community. Rice is

*Corresponding author: nirmalav@am.amrita.edu

© The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative
Commons Attribution License 4.0 (https://creativecommons.org/licenses/by/4.0/).
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typically cultivated in two distinct seasons: Kharif, the monsoon season from June to
October, and Rabi, the winter season from November to March [6]. The seeds for the Kharif
season are normally sowed in late May in anticipation of the southwest monsoons that start
on 1 June. However, during the past two years, delayed monsoon onsets have necessitated a
shift in seed sowing and harvesting dates. Additionally, there has been a concerning decline
in paddy yields in Kollengode, prompting investigations into the underlying causes.
Our project aims to understand the challenges faced by farmers in Kollengode and
surrounding areas. By engaging with the farming community, we intend to gain a deeper
understanding of their specific concerns, such as declining crop yields, pest and disease
management, and market access and pricing. Our ultimate goal is to develop and implement
solutions that address these concerns, improve agricultural sustainability, and ensure the
long-term well-being of the farming community in the region. This paper takes the first step
towards our goal and investigates the factors contributing to the recent decrease in paddy
yields in Kollengode. We examine rainfall, temperature, and groundwater data, alongside
information gathered during our field visits to Kollengode.
The paper begins with a brief overview of the various stages involved in paddy
cultivation, followed by a detailed discussion of the factors that typically impact paddy
yield, such as weather patterns, water availability, and pest management practices. We then
describe our study area and the methods employed in this study. This is followed by a
presentation and analysis of the key findings related to the recent decline in paddy yields.
Finally, the paper concludes with recommendations for potential solutions to address the
identified challenges and suggestions for future research directions.

2 Stages in paddy cultivation

Paddy cultivation can be broadly divided into three key stages based on the plant’s
development:
1. Vegetative stage: This is the initial stage after germination, and is marked by growth
and development of the leaves and root system. The stage typically lasts for about 50–
60 days, depending on the rice variety and growing conditions.
2. Reproductive stage: This stage marks the shift from vegetative growth to grain
production. It consists of three substages:
• Heading stage: The panicle (flowering head) emerges from the uppermost leaf
sheath, signalling the start of flower development. This stage usually lasts for
around 7–10 days.
• Flowering stage: The flowers within the panicle open and pollination
occurs. This stage typically lasts for 5–7 days.
• Milking stage: The fertilised flowers begin to develop into grains, initially
appearing milky-white in colour. This stage lasts for about 20–30 days.
3. Maturity stage: This stage involves the grains ripening and turning golden in colour. It
typically lasts for 20–30 days, depending on the variety.
The timing and duration of each stage can vary depending on several factors, including
the specific rice variety, climatic conditions, and agricultural practices.

3 Factors affecting paddy yield

Numerous elements contribute to the final success of a paddy harvest, such as rainfall,
groundwater levels, soil characteristics, the chosen rice variety, implemented crop
management practices, prevailing temperature, and the presence of pests and diseases.

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3.1 Rainfall

Rainfall directly impacts paddy productivity, playing a critical role in determining crop
yield. Insufficient rainfall throughout the growing season, particularly during the vegetative
stage, can trigger drought conditions and negatively impact yield. Conversely, excessive
rainfall during the heading and flowering stages can be detrimental, potentially delaying
grain filling and harvest. Ideally, paddy thrives in regions receiving 1,000–1,500 mm of
annual rainfall [7, 8], ensuring abundant water throughout the vegetative stage while
avoiding detrimental flooding during later stages.

3.2 Groundwater
Groundwater plays a crucial role in paddy cultivation, directly impacting crop yield and
overall agricultural productivity. While the relationship is complex and influenced by
various factors, the availability and quality of groundwater can significantly affect rice
growth and development.

3.2.1 Positive impacts

• Reliable water source: When groundwater levels are adequate, they provide a
dependable source of irrigation water, especially during drier periods when rainfall
is insufficient. This ensures consistent moisture availability throughout the growing
season, crucial for optimal plant growth and yield potential.
• Nutrient availability: Groundwater often contains dissolved nutrients essential for
plant growth, such as nitrogen, phosphorus, and potassium. Access to these nutrients
through groundwater uptake can supplement fertilisers and enhance yield potential.

3.2.2 Negative impacts

• Drought stress: Depleted groundwater levels can lead to drought stress, impacting
plant growth and development. Inadequate water availability during critical stages
like tillering (shoot branching) and grain filling can significantly reduce yield.
• Salinity intrusion: In coastal regions, excessive groundwater extraction can cause
saltwater intrusion, increasing water salinity. This can adversely affect rice plants,
reducing yields and even leading to crop failure.
• Nutrient imbalance: Changes in groundwater quality due to factors like pollution
or natural variations can affect nutrient availability and uptake by plants. This can
lead to nutrient deficiencies or imbalances, hindering plant growth and impacting
yield.

3.3 Soil characteristics

Soil characteristics, such as texture, bulk density, and pore space, play a critical role in
influencing paddy yield. A balanced texture, ideally a loamy mix (a good proportion of
sand, silt, and clay particles), allows for optimal root penetration, air circulation, and water
retention. Conversely, heavy clay soils can hinder drainage, while sandy soils drain too
quickly. Bulk density, the weight of soil per unit volume, affects the available pore space.
Loose, well-aggregated soil with moderate bulk density ensures both adequate air for root
respiration and sufficient water holding capacity. Conversely, dense and compacted soils
restrict air and water availability, hindering plant health. Ultimately, texture and bulk
density influence the soil’s water retention capacity, the ability to hold water for plant

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use. Clay-rich soils hold more water, but excessive levels can be detrimental. Sandy soils
drain quickly, potentially leading to drought stress. A balance between these extremes is
crucial for optimal paddy growth.

3.4 Rice variety

Rice variety plays a significant role in paddy yield, with different varieties having different
inherent yield potentials based on genetic factors like tillering ability, grain size, and
disease resistance. Some varieties are better adapted to specific climates, soil types, and
water availability than others. Choosing varieties suited to local conditions can significantly
improve yield. Varieties with shorter growth durations can fit multiple cropping cycles
within a year, potentially increasing overall yield.

3.5 Crop management practices

Implementing crop management practices like proper tillage, optimal planting density,
judicious fertiliser use, efficient water management, intercropping, and crop rotation
fosters healthy soil, breaks disease cycles, manages pests, and promotes sustainable, high
yields. Tilling the soil loosens it, allowing for better root penetration, air and water
circulation, and drainage; however, it can also disrupt soil structure and accelerate the
breakdown of organic matter, leading to reduced soil fertility and water retention capacity.
Therefore, tillage should be done with care, minimising soil disturbance to maintain long-
term soil health. Optimal plant density ensures proper competition for resources like light
and nutrients while avoiding overcrowding that can hinder growth.
Intercropping, the practice of growing two or more crops together in close proximity,
offers numerous benefits. Different crops can occupy different niches within the same field,
potentially leading to higher overall yield from the combined crops. As different crops have
varying nutrient requirements and root depths, one crop can utilise nutrients that are less
accessible to the other, maximising nutrient uptake and minimising waste. Some
intercropping combinations can help manage water resources. For example, taller crops can
provide shade and reduce water evaporation from the soil, benefitting shorter companion
crops. Intercropping can also suppress weeds and lead to improved pest and disease control,
since a diverse selection of plants in the field can disrupt the life cycle of pests and diseases
adapted to a single crop. Intercropping, particularly with cover crops, can help protect the
soil from wind and water erosion, crucial for maintaining soil fertility and long-term
productivity. The root systems of different intercropped plants can create a more complex
and diverse soil structure, promoting aeration and drainage, which benefits overall soil
health.

3.6 Temperature

Rice plants thrive within a specific temperature range, ideally between 20 °C and 35 °C [9],
although this optimal range can vary slightly depending on rice variety and specific climatic
conditions. Deviations from this optimal zone, whether higher or lower, can significantly
impact plant development and ultimately, yield. The temperature fluctuations influence the
timing and pace of various growth stages, affecting growth rate and overall yield potential.
The severity of these impacts depends on both the intensity and duration of the temperature
shift.
Temperatures exceeding 35 °C stress the root and shoot system, hampering their growth
and impacting nutrient uptake. This, in turn, hinders vital reproductive processes like
pollination and pollen release, potentially leading to poor fertilisation and ultimately

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resulting in unfilled grains (spikelet sterility) [10]. Prolonged exposure to such heat further
amplifies these problems by directly disrupting pollen release, pollination, and germination.
Additionally, high temperatures shorten the critical grain filling period, further reducing
yields.
On the other hand, temperatures below 20 °C primarily impact earlier growth stages and
development. Cold temperatures slow down metabolic processes, delaying seed
germination and seedling establishment. This can later lead to uneven stands (crop fields
where the plants are unevenly distributed in terms of density, growth stage, or health) and
reduced tillering. Additionally, flowering may be disrupted, resulting in incomplete grain
development in the panicle [10]. Ultimately, these issues contribute to lower yields,
although through distinct mechanisms compared to high temperatures.

3.7 Pests

Numerous insects pose threats to rice plants, including planthoppers (e.g., brown
planthopper, white-backed planthopper) and leafhoppers (e.g., green rice leafhopper, black
leafhopper) [11]. These insects primarily harm rice through the transmission of viral
diseases, but they also damage plants by feeding on them and excreting honeydew. Other
damaging insects include stem borers (e.g., yellow stem borer, white stem borer) and gall
midges (e.g., Asian rice gall midge). Stem borers feed on the plant’s internal tissues,
disrupting their structure and function. Gall midges manipulate the plant’s growth
hormones, leading to abnormal gall formation and hindering functionality. However, it is
important to note that not all species within these groups are detrimental; some even play
beneficial roles. The presence of beneficial insects (decomposers, scavengers, etc.),
pollinators, and natural enemies of pests can in fact contribute to yield improvement.
In addition to the insects mentioned above, other potential threats depending on the
region and circumstances include weevils, armyworms, grasshoppers, and thrips. Root-
feeding nematodes, which are microscopic worms ranging from a few micrometres to
millimetres, can damage plant roots and hinder growth. Snails and slugs feed on young
seedlings and leaves, potentially affecting plant establishment. Vertebrates can also be
significant pests. Rats and mice can cause substantial yield losses by feeding on grains and
stems. Some bird species consume rice grains at various stages, impacting yields.

3.8 Diseases
In general, fungal diseases like rice blast, sheath blight, and brown spot are among the most
widespread and damaging globally for paddy plants. These diseases affect various plant
parts (leaves, stems, grains) and can result in significant yield loss. However, the relative
importance of fungal, bacterial, and viral diseases can vary depending on the specific
region, rice variety, and climate. Bacterial diseases like leaf blight, leaf streak, grain rot,
and panicle blight [12] can be significant in specific regions or under certain conditions.
Viral diseases transmitted by insect vectors, like rice tungro disease complex (transmitted
by leafhoppers) and rice ragged stunt virus (transmitted by white-backed planthoppers)
[11], can also cause widespread damage and stunted growth if vector populations are high.

3.9 Additional environmental influences

Apart from the previously mentioned factors, several other environmental elements can
impact paddy yields:
• Day length (photoperiod): The duration of sunlight during the growing season
influences various physiological processes in rice plants, including flowering

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time, tillering, and grain filling. Depending on the rice variety and its sensitivity to
photoperiod, shorter or longer days may lead to reduced yield potential.
• Extreme weather events: Strong winds, hailstorms, and floods associated with
extreme weather events can physically damage rice plants, causing lodging (falling
over), shattering of grains, and reduced yield.
• Air quality: Air pollution from industrial activities or agricultural practices can
negatively impact plant growth and development. Pollutants like ozone, sulphur
dioxide, and heavy metals can reduce photosynthesis, damage leaves, and hinder
grain filling, ultimately leading to yield losses.

4 Study area
Kollengode village is a major agricultural village located within the Palakkad district of
Kerala State in south India. Paddy cultivation is a cornerstone of Kollengode’s economy,
encompassing roughly 10,000 hectares of land and providing a livelihood for more than
6,000 families. Farms in the region are predominantly small-scale, with most farmers
cultivating 1–2 hectares. A small number of larger farms exceeding 5 hectares also exists.
This region experiences a humid climate with distinct seasons: a hot period (March–
May), followed by the southwest monsoon (June–September) characterised by heavy
rainfall, and the northeast monsoon (October–November) with moderate precipitation. The
remaining months (December–February) are relatively dry. The annual temperature ranges
from 20 °C to 45 °C.

5 Methods
Information regarding rice varieties grown in Kollengode, their yield per acre, crop
management practices, and prevalent pests and diseases was obtained from Krishi Bhavan
(the Kollengode agricultural department) and through detailed, semi-structured discussions
with local farmers on multiple occasions. To acquire rainfall data, we accessed records
from the Chulliyar dam (4 km from Kollengode), where a combination of Simons and
tipping bucket rain gauges provides daily measurements collected at 8:00 am. Groundwater
data was sourced from a government publication [13, p. 21], while the values of soil
properties were obtained from published studies [14, 15]. Temperature data was acquired
from Climate-Data.org [16], which uses data generated by the European Centre for Medium-
Range Weather Forecasts (ECMWF) [17]. This data was cross-verified with temperature
information obtained from other meteorological websites [18–20] to ensure accuracy.

6 Results
Uma Matta is the primary rice variety cultivated in Kollengode village; Table 1 provides
data on the average yield per acre for the period 2018–2023.

Table 1. Uma Matta rice yield per acre in Kollengode, 2018–2023.

Year 2018 2019 2020 2021 2022 2023

Yield per acre (kg) 2500 2300 1900 2000 2000 1900

Table 1 reveals a low paddy yield in Kollengode for 2023. This section delves into the
factors that might have contributed to the reduced yield during this specific year.

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6.1 Rainfall

Rice cultivation in Kollengode primarily relies on rainfed agriculture during the main
monsoon season (June–September). However, the crucial water source for these crops—
monsoon rainfall—has witnessed considerable fluctuations in recent years. Notably, 2018
experienced anomalously high rainfall (2,627 mm), coinciding with the Kerala floods.
Conversely, 2023 saw a marked deficit in precipitation (1,369 mm). This variability in
monsoon rainfall, particularly the marked deficit in 2023 (Table 2), likely contributed to the
lower crop yield during that year.
Table 2. Annual rainfall at Chulliyar dam, Kollengode village, Palakkad district, 2018–2023.

Year 2018 2019 2020 2021 2022 2023

Rainfall (mm) 2627 1602 1476 1895 1834 1369

Table 3 and Figure 1 present monthly rainfall data for 2021–2023, offering a closer look
at patterns within the crucial Kharif rice cultivation season (June–October). Although all
three years received peak rainfall in July, the distribution of rainfall across the season
differed significantly (Table 3, Figure 1). Specifically, June rainfall was significantly higher
in 2021 compared to 2022 and 2023, consistent with the typical monsoon onset around
1 June and reports of a two-week delay in monsoon onsets in 2022 and 2023.
Further, August 2023 saw a substantial rainfall deficit compared to 2021 and 2022.
Focusing on the Kharif season, 2021 and 2022 received moderate rainfall (1,347 mm and
1,278 mm, respectively), while 2023 witnessed a significant deficit (780 mm) (Table 3,
Figure 1). Notably, deficits were observed in June, August, and September of 2023, which
coincide with critical stages of rice development (e.g., germination and seedling
development, panicle development, and grain filling). Thus, rainfall deficit could have been
a major contributing factor to the yield decline observed in 2023 (Table 1).
Table 3. Monthly rainfall at Chulliyar dam, Kollengode village, Palakkad district, 2021–2023.
Rainfall (mm)
Month
2021 2022 2023
April 106 58 93

May 154 251 32

June 213 66 65

July 434 520 462

August 155 444 15

September 161 129 123

October 384 119 115

November 219 166 315

December 14 43 96

Kharif season 1347 1278 780

Total 1840 1796 1316

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Rainfall, April–December 2021–2023

600
2021 2022 2023
500
Rainfall (mm)

400

300

200

100

Fig. 1. Monthly rainfall at Chulliyar dam, Kollengode village, Palakkad district, 2021–2023.

Fig. 2. Groundwater status, Palakkad district, March 2017 [13].

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6.2 Groundwater

Paddy cultivation is water-intensive, requiring around 5,000 litres per kilogram of rice [21].
This high demand exceeds the region’s groundwater recharge capacity, leading to rapid
depletion throughout the region, including areas near the Chulliyar dam. Restricted canal
water supply during the cultivation season forces farmers in specific areas to rely solely on
groundwater, further accelerating depletion in those areas. If unchecked, this practice could
worsen the situation and lead to widespread overexploitation of groundwater. Prolonged
heat and erratic monsoons likely exacerbate the situation by increasing evaporation and
reducing natural recharge of groundwater. As depicted in Figure 2 [13] (preceding page), a
significant portion of the Palakkad district falls under the “critical” or “over-exploited”
categories, highlighting a severe water scarcity situation.

6.3 Soil characteristics

A recent study [14], in line with earlier investigations [15], identified the soil type at
Kollengode as sandy clay loam. The study further characterised the soil with an average
pore space of 45.4% and an average water retaining capacity of 40.2%, indicating desirable
properties for crop growth. Detailed soil properties, obtained from [14] and [15] are
presented in Table 4.

Table 4. Properties of Kollengode soil [14, 15]

Soil property Value

Sand fraction 63.8–70.1%

Silt fraction 9.14–13.5%

Clay fraction 20.2–24.2%

Bulk density 1.15–1.29 gcm⁻³

Particle density 2.44–2.53 gcm⁻³

Pore space 44.1–47.5%

Water retention capacity 1.15–1.29%

Based on our interactions with farmers, we learnt of no significant changes in soil

properties like nutrient content and pH. Therefore, it is highly unlikely that soil properties
are a major contributing factor to the observed decline in paddy yield.

6.4 Rice variety

Two coarse red rice varieties, Uma Matta and Jyoti Matta, are cultivated in Kollengode.
Uma Matta, an indigenous variety cultivated in Udupi, Dakshina Kannada, and Palakkad, is
renowned for its high nutritional content and resilience to challenging conditions. Jyoti
Matta, primarily grown in Kerala, shares similar characteristics, with a shorter growing
season and potentially higher yield compared to Uma Matta. However, since both varieties
have been historically cultivated in Kollengode, fluctuations in yield are unlikely to be
attributable to rice variety selection.

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6.5 Crop management practices

The two rice varieties, Uma Matta and Jyoti Matta, are cultivated in two distinct seasons:
Kharif (June–October, rainfed harvest in October) and Rabi (November–March, irrigated
harvest in March).
Land preparation in Kollengode begins with primary tillage, using a tractor equipped
with a disc plough to break and loosen compacted soil, facilitating better aeration, drainage,
and root development for the crop. The land is then smoothed to create a level surface for
uniform water distribution. Next, secondary tillage with tillers refines the soil, creating a
finer, looser seedbed (improved tilth) for optimal seed-to-soil contact and germination.
Bunds are constructed around the field perimeter, either manually or using tillers, to retain
water within the field and prevent flooding in surrounding areas.
Rice seeds are treated with beneficial bacteria, Pseudomonas, for disease protection
before being sown in a nursery. Nurseries offer controlled environments, optimising
seedling development by shielding against pests and disease while facilitating efficient
water use. After 14 days in the nursery, seedlings are transplanted to the field either
manually or mechanically. Manual transplanting requires 35 kg of seeds per acre due to
denser planting patterns (15 × 10 cm spacing, resulting in approximately 270,000 plants per
acre). In contrast, mechanical transplanting, applied in conjunction with the System of Rice
Intensification (SRI) method, results in wider spacing (25 × 25 cm) with fewer plants per
unit area (approximately 64,000 plants per acre). This wider spacing allows for better root
and canopy development, leading to efficient nutrient and sunlight utilisation.
Consequently, mechanical transplanting requires significantly less seed, typically ranging
from 5–7 kg per acre.
Following transplantation, weeding is performed at 10-day intervals. This frequent soil
disturbance improves the physical, chemical, and biological properties of the soil. Three
labourers typically weed one acre per day. A cono weeder (a manual tool with serrated blades)
is occasionally used, requiring supplemental hand weeding but reducing overall weeding
cost by 50%. The farmers also use pre-emergence herbicides containing pretilachlor alone
(e.g., Rifit) or pretilachlor with bensulfuron-methyl (e.g., Londax) for weed control.
Inorganic fertilisers like Factamfos (a complex synthetic fertiliser with nitrogen,
phosphorus, and sulphur), urea, and potash are used, alongside organic options like
Jeevamrutham (a liquid concoction made from cow dung, cow urine, jaggery, and chickpea
flour), manure, green leaf manure, lime, groundnut cakes, and neem cakes. Synthetic
pesticides (e.g., quinalphos-based Ekalux, fenvalerate-based Fenval), as well as naturally-
derived organic pesticides (e.g., a local five-leaf extract, chilli-garlic solution, neem leaf
extract) are utilised. Fertilisers, pesticides, and herbicides are all applied manually.
For crop rotation, farmers primarily use cowpea and Dhaincha (Sesbania aculeata).
Cowpea, sown 15 days after land preparation, fixes atmospheric nitrogen, benefitting the
succeeding crop. Dhaincha, typically sown 45 days before tillage, offers similar nitrogen
fixation benefits while also improving soil structure and organic matter content through its
biomass incorporation.
The primary source of water for irrigation in Kollengode comes from the Chulliyar dam
(4 km away) and the Meenkara dam (3 km away). Some farmers also utilise alternative
sources like bore wells, wells, ponds, and canals to supplement their irrigation needs.
Farmers primarily rely on alternate wetting and drying (AWD) for water management. This
water-saving strategy involves initial irrigation during the early crop stage, followed by
applying water to maintain a shallow water depth (2.5 cm) only when indicated necessary
by hairline cracks in the soil surface. This controlled irrigation approach ensures adequate
soil moisture for healthy plant growth while minimising water usage.
Our discussions with farmers revealed no changes in crop management practices,
suggesting a minimal contribution to the observed decrease in paddy yield.

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6.6 Temperature

Temperature data (Table 4, Figure 3) from Palakkad town, around 25 km from Kollengode,
suggests a potential link between increasing minimum temperatures (Table 5) and yield
reductions in Uma Matta rice in Kollengode (Table 1). Compared to 2022, the minimum
temperatures during February–October 2023 increased at a faster rate (at an average of
3.24%) than the corresponding maximum temperatures, which either decreased or increased
at a slower rate (at an average of −4.39%). (In July and August, minimum temperatures
decreased slower than maximum temperatures; in September and October, minimum
temperatures remained stable, while maximum temperatures decreased; Table 6.) This
phenomenon, known as “nighttime warming”, has been linked to higher respiration loss in
rice plants, potentially impacting yield potential [22].
Table 5. Minimum and maximum temperatures, Palakkad town, 2021–2023.
2021 temperatures (°C) 2022 temperatures (°C) 2023 temperatures (°C)
Minimum Maximum Minimum Maximum Minimum Maximum
January 19 29 19.44 30 21 33

February 20 30 19.44 32.77 22 34

March 21.11 36 22.22 37.55 24 38

April 23.8 36.5 23.88 36.88 25 36.5

May 24.4 35.4 23.88 36.44 25 33

June 22.7 30.5 23.33 30.55 24 29

July 22.7 30.5 22.22 30.55 22 28

August 22.2 30.5 22.22 31.55 21.5 29

September 21.2 31.11 21 32 21 30

October 22.2 31.11 21 32 21 30

November 21.66 29.44 22 30 21 31

December 21.11 28.88 21 30 21 32

Table 6. Increase in minimum and maximum temperatures, Palakkad town, 2021–2023.

2021–2022 2022–2023
Increase in min temp Increase in max temp Increase in min temp Increase in max temp
(°C) (%) (°C) (%) (°C) (%) (°C) (%)
Jan 0.44 2.32 1 3.45 1.56 8.02 3 10.00

Feb −0.56 −2.80 2.77 9.23 2.56 13.17 1.23 3.75

Mar 1.11 5.26 1.55 4.31 1.78 8.01 0.45 1.20

Apr 0.08 0.34 0.38 1.04 1.12 4.69 −0.38 −1.03

May −0.52 −2.13 1.04 2.94 1.12 4.69 −3.44 −9.44

Jun 0.63 2.78 0.05 0.16 0.67 2.87 −1.55 −5.07

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Jul −0.48 −2.11 0.05 0.16 −0.22 −0.99 −2.55 −8.35

Aug 0.02 0.09 1.05 3.44 −0.72 −3.24 −2.55 −8.08

Sep −0.2 −0.94 0.89 2.86 0 0 −2 −6.25

Oct −1.2 −5.41 0.89 2.86 0 0 −2 −6.25

Nov 0.34 1.57 0.56 1.90 −1 −4.55 1 3.33

Dec −0.11 −0.52 1.12 3.88 0 0 2 6.67

40
35
30
25
20
15
10
5
0

2021 minimum 2021 maximum 2022 minimum

2022 maximum 2023 minimum 2023 maximum

Fig. 3. Minimum and maximum temperatures, Palakkad town, 2021–2023.

6.7 Pests
Based on information gathered from farmers and agricultural officers, the insect pests
impacting paddy yields in Kollengode include green leafhoppers, which suck the plant sap
from leaves and leaf sheaths; yellow stem borers, whose larvae bore into the central shoot
of paddy seedlings and tillers, causing the drying of the shoot; and gall midges/gnats,
where the females lay eggs and the larvae feed within plant tissue, creating galls.
Additionally, during the planting and pre-tillering stages, leaf folder/rollers infest the
paddy plants. The larvae of the leaf folders/rollers fold the plant leaves longitudinally and
reside inside, scraping the green tissues of the leaves, leading to white and dry leaves.
However, given the absence of a recent pest outbreak, other factors are likely responsible
for the observed decline in paddy yield.

6.8 Diseases

The rice crops can also suffer from a fungal disease, rice blast, which gives a “blasted” or
burnt appearance to the entire paddy crop. Although rice blast can cause significant yield

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losses, the lack of a recent outbreak points towards other contributing factors for the
observed decline.

6.9 Additional environmental influences

Based on farmer reports, extreme weather events, increased air pollution, and changes in
sunlight duration over the past year, 2023, appear to have minimal influence on the
observed yield decline. Therefore, it is highly unlikely that these factors are major
contributing factors to the yield decline.

7 Discussion
Our investigation explored several potential causes for the observed paddy yield decline,
focusing on climatic factors (rainfall, temperature), agricultural practices (rice varieties,
crop management), and environmental influences (soil properties, pest and disease
incidence, air pollution, sunlight duration). Notably, significant reduction in rainfall during
the critical growing season is likely the primary contributor. However, data for factors like
soil properties, pest and disease incidence, air pollution, and sunlight duration were
primarily obtained through farmer reports and existing literature, while instrumental data
analysis for these factors, along with long-term weather data analysis and analysis of
groundwater levels, could provide a more comprehensive assessment of their contributions.
Decreased water availability can also make rice plants more susceptible to the effects of
nighttime warming, potentially leading to increased respiration rates and reduced yields
[22]. However, further research with data encompassing a longer period and physiological
studies on the specific rice variety grown in Kollengode are necessary to determine the
precise impact of temperature changes on yield in this specific context.
Kollengode farmers already employ several water-saving practices in their crop
management, as reported by the farmers themselves. These practices include alternate
wetting and drying (AWD), the System of Rice Intensification (SRI) method, and raising
seedlings in nurseries (section 6.5). AWD minimises water waste by tailoring irrigation
based on soil moisture. SRI, through wider plant spacing, promotes better root development
and reduces water requirements compared to traditional dense planting. Raising seedlings
in nurseries allows for controlled water application and efficient use compared to direct
seeding in the field. Additionally, organic supplements like Jeevamrutham and neem cake
can improve soil health, potentially leading to enhanced water retention capacity. Crop
rotation with cowpea and Dhaincha can contribute to nitrogen fixation in the soil,
potentially reducing the need for nitrogen-based fertilisers and indirectly promoting water
conservation.
Currently, most Kollengode farmers rely on flood irrigation for paddy cultivation, a
method known for high water usage. However, more efficient irrigation systems like drip
irrigation or sprinkler systems offer a promising solution. These systems deliver water
directly to plant roots, minimising water waste and maximising water uptake by the plants.
Additionally, smart sensor-based irrigation systems can be considered. These systems
automatically adjust water application based on real-time soil moisture data, further
optimising water use. Some of these systems can be solar-powered, minimising reliance on
the grid and reducing power consumption costs.
Given the absence of rainwater harvesting in Kollengode, implementing this approach
could also provide several benefits and complement existing water-saving practices like
AWD. Rainwater harvesting would provide another source of water, reduce dependence on
dams, and increase water security [23]. Kollengode has the potential to implement
rainwater harvesting systems on a significant scale. This could involve building large

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storage tanks or recharging groundwater through well systems. Reliable water access could
allow farmers to cultivate additional crops or extend the growing season, potentially
improving their income and diversifying their agricultural output.
However, implementing and maintaining irrigation systems and rainwater harvesting
infrastructure can be expensive, especially for small-scale farmers. Access to financial
support and subsidies might be necessary. Operating and maintaining irrigation systems
effectively requires technical knowledge and training. Farmers might need support and
capacity-building in this area. While improved irrigation systems can offer significant water
savings, it is important to acknowledge the potential consequence of reduced labour
demand, particularly for tasks like manual irrigation and weed control. This could
negatively impact the livelihoods of agricultural labourers in the community. Therefore,
alongside implementing these technologies, exploring opportunities for upskilling programs
for these workers might be crucial.
Beyond improved irrigation systems and rainwater harvesting, additional strategies can
be explored to enhance soil moisture retention and support crop resilience during dry
periods. These strategies include incorporating drought-resistant cover crops and applying
organic mulches or biochar to the soil. Cover crops, with their extensive root systems,
improve soil structure and organic matter content, leading to increased water holding
capacity. Organic mulches and biochar can further reduce evaporation and suppress weeds,
promoting soil moisture conservation [24, 25].
This study identified several potential responses to address reduced rainfall and water
availability in Kollengode, including advanced irrigation technologies, rainwater
harvesting, soil moisture management practices (mulching, cover cropping), and potentially
drought-resistant rice varieties. However, further research is crucial to prioritise and
optimise their implementation for local conditions. For instance, a deeper understanding of
existing rice varieties and market demands for drought-resistant options is necessary before
recommending a shift in cultivars. Additionally, research into the feasibility and economic
viability of advanced irrigation technologies tailored to Kollengode’s specific needs would
be valuable.

8 Conclusion
This study investigated the potential causes of declining paddy yield in Kollengode.
Analysis revealed that reduced rainfall during the critical growing season is a likely
contributor. While Kollengode farmers already employ water-saving practices, this research
identified improved irrigation systems, rainwater harvesting, and soil moisture management
strategies (cover cropping, mulching) as promising avenues for further water conservation
and yield improvement. The study highlights the importance of water management for
sustainable paddy cultivation in Kollengode. Implementing these solutions, along with
further research on the economic viability and local optimisation of irrigation options, can
help ensure water security and long-term agricultural productivity in the region.

Acknowledgements
We are deeply grateful to our Chancellor, Sri Mata Amritanandamayi Devi, for enabling
this work. Her vision of socially impactful research has shaped the endeavours of our
university.
We thank the local farmers for their invaluable help and contributions to this work:
Mrs. Bindu Anandakrishnan, Mr. Chandran V., Mr. Jayaprakash, Mr. Kuruppesh Kumar,
Mr. Radhakrishnan, Mr. Rajsundar P. R., Mrs. Saralakumari, Mr. Sahadevan, Mr. S.
Suresh, Mr. Vasudevan P. V., Mr. Vijayan C. (names in alphabetical order).

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We express our sincere appreciation to the following Government officials for their
assistance:
Department of Agriculture: Mr. Rahul Raj M. (Agricultural Officer, Krishi Bhavan, the
Kollengode agricultural department), Mr. Sreejith K. (Field Assistant, Krishi Bhavan).
Irrigation Department: Mr. Rajeev (Overseer, Chulliyar dam, Kollengode).
We gratefully acknowledge Ms. C. K. Aavanthi, Ms. Nandana, Mrs. Salini Kuruppesh,
and Mr. Kaushik Ramanathan for their unwavering support. Our gratitude extends to the
Kollengode villagers and the staff of Krishi Bhavan for their help throughout the study.

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