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Humanity faces the grand challenge of feeding a growing, more affluent population in the coming decades while reducing the environmental burden of agriculture. Approaches that integrate food security and environmental goals offer promise for achieving a more sustainable global food system, yet little work has been done to link potential solutions with agricultural policies. Taking the case of cereal production in India, we use a process-based crop water model and government data on food production and nutrient content to assess the implications of various crop-shifting scenarios on consumptive water demand and nutrient production. We find that historical growth in wheat production during the rabi (non-monsoon) season has been the main driver of the country’s increased consumptive irrigation water demand and that rice is the least water-efficient cereal for the production of key nutrients, especially for iron, zinc, and fiber. By replacing rice areas in each district with the alternative cereal (maize, finger millet, pearl millet, or sorghum) with the lowest irrigation (blue) water footprint (WFP), we show that it is possible to reduce irrigation water demand by 33% and improve the production of protein (+1%), iron (+27%), and zinc (+13%) with only a modest reduction in calories. Replacing rice areas with the lowest total (rainfall + irrigation) WFP alternative cereal or the cereal with the highest nutritional yield (metric tons of protein per hectare or kilograms of iron per hectare) yielded similar benefits. By adopting a similar multidimensional framework, India and other nations can identify food security solutions that can achieve multiple sustainability goals simultaneously.
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Alternative cereals can improve water use and nutrient
supply in India
Kyle Frankel Davis
1,2
*, Davide Danilo Chiarelli
3
, Maria Cristina Rulli
3
, Ashwini Chhatre
4
,
Brian Richter
5
, Deepti Singh
6,7
, Ruth DeFries
8
Humanity faces the grand challenge of feeding a growing, more affluent population in the coming decades while
reducing the environmental burden of agriculture. Approaches that integrate food security and environmental goals
offer promise for achieving a more sustainable global food system, yet little work has been done to link potential
solutions with agricultural policies. Taking the case of cereal production in India, we use a process-based crop water
model and government data on food production and nutrient content to assess the implications of various crop-
shifting scenarios on consumptive water demand and nutrient production. We find that historical growth in wheat
production during the rabi (non-monsoon) season has been the main driver of the countrys increased consumptive
irrigation water demand and that rice is the least water-efficient cereal for the production of key nutrients, especially
for iron, zinc, and fiber. By replacing rice areas in each district with the alternative cereal (maize, finger millet, pearl
millet, or sorghum) with the lowest irrigation (blue) water footprint (WFP), we show that it is possible to reduce irri-
gation water demand by 33% and improve the production of protein (+1%), iron (+27%), and zinc (+13%) with only a
modest reduction in calories. Replacing rice areas with the lowest total (rainfall + irrigation) WFP alternative cereal or
the cereal with the highest nutritional yield (metric tons of protein per hectare or kilograms of iron per hectare) yielded
similar benefits. By adopting a similar multidimensional framework, India and other nations can identify food security
solutions that can achieve multiple sustainability goals simultaneously.
INTRODUCTION
Global crop production has more than tripled since the 1960s, leading
to increased food supply per capita, lower food prices, and reduced mal-
nutrition worldwide (1). This remarkable growth in global food supply
has been accompanied by the depletion of freshwater resources for ir-
rigation (24), nutrient pollution from injudicious fertilizer application
(5,6), and rising greenhouse gas emissions (7,8). There is therefore
widespread agreement that agricultures use of planetary systems is un-
sustainable (913) and that humanity will need to feed an additional
2 billion people by 2050 while also minimizing the environmental
consequences of the global food system (1,14). Numerous studies have
explored strategies to resolve this food-environment dilemma [for ex-
ample, (1,7,11,13,14)], but little work has been done to examine nu-
tritional and environmental outcomes together or to identify concrete
policy pathways by which these solutions may be put into action within
specific countries. Given the immediacy of food security and sustain-
ability challenges around the world, incorporating these solutions by
leveraging a nations existing agricultural policies offers promise to bet-
ter link science with real-world outcomes.
The need for improved compatibility between food security and
environmental stewardship is of considerable urgency in India. The
worlds second most populous country, India, has remained largely
self-sufficient in terms of cereal production over the past 50 years, with
rice (grown during the kharif/monsoon season) and wheat (grown during
the rabi/winter season) as the flagship crops driving substantial increases
in food supply (15). While the boom in rice-wheat systems has vitally
contributed to reducing hunger and malnutrition throughout India
(16), these trends in production have been supported by ever-increasing
agricultural inputs and extensive environmental consequences, particu-
larly for freshwater resources. Many parts of the country now experience
chronic water stress due to heavy-water extraction for irrigated agricul-
ture (1719) and a weakening monsoon (2022), while widespread nu-
trient deficiencies persist (23,24). Because Indian diets generally derive a
large fraction of nutrients from cereals (25), these mounting food security
and environmental challenges make it increasingly clear that the rice-
wheat status quo of the Indian food system requires critical examination
and that solutions that integrate nutrition and the environmental impacts
of food production can offer pathways toward healthier food baskets with
less environmental burden (26).
Because India relies mainly on domestic production, the country
presents an excellent opportunity for examining how alterations of pro-
duction within the country could potentially benefit nutrition and water
use. Recent work [for example, (27,28)] has demonstrated the large in-
efficiencies present in food systems in terms of water use, showing the
possibility of planting crops with lower water requirements while also
enhancing calorie and protein production. Other studies in central In-
dia have examined water stress, land use, nutrition, and climate sensi-
tivity associated with cereal production and demonstrated that certain
cereals can offer distinct benefits over rice along all of these dimensions
(19,29,30). However, a national analysis of the potential nutritional and
water use benefits of alternative cereals (that is, maize, millets, and sor-
ghum) is still lacking for India.
To do this, we first examine how Indian cereal production has
changed through time, what this has meant for historical water use
and nutrient production, and how these dimensions might benefit from
alternative mixes of cereal crops. We limit our analysis to consider four
key nutrientscalories, protein, iron, and zincforwhichcerealsserve
as the major source in Indian diets (25). For each district, we first quan-
tify the water requirements [equal to the evapotranspiration from a crop
over a growing season; units are in millimeters of H
2
Operyear
1
The Earth Institute, Columbia University, New York, NY 10025, USA.
2
The Nature Con-
servancy, New York, NY 10001, USA.
3
Department of Civil and Environment Engineer-
ing, Politecnico di Milano, Milan, Italy.
4
Indian School of Business, Hyderabad, India.
5
Sustainable Waters, Crozet, VA 22932, USA.
6
Lamont-Doherty Earth Observatory, Co-
lumbia University, Palisades, NY 10964, USA.
7
School of the Environment, Washington
State University, Vancouver, WA 99164, USA.
8
Department of Ecology, Evolution, and
Environmental Biology, Columbia University, New York, NY 10027, USA.
*Corresponding author. Email: kd2620@columbia.edu
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(hereinafter mm H
2
Oyear
1
)]foreachofthemajorcerealcropsgrownin
India [rice (Oryza sativa), maize (Zea mays), wheat (Triticum aestivum),
sorghum (jowar; Sorghum vulgare), pearl millet (bajra; Pennisetum
typhoideum), and finger millet (ragi; Eleusine coracana)], using average
climate data for 2000 through 2009 and categorizing based on growing
season (kharif/monsoon for rice, maize, finger millet, and pearl millet;
rabi/winter for wheat; and both seasons for sorghum). We then com-
bine this information with historical production data (31)toestimate
crop demandthe product of crop water requirement (CWR) and har-
vested areafor green water (that is, rainfall) and blue water (that is,
irrigation required to avoid crop water stress) from 1966 through
2009. We also assess patterns of reliance on irrigation and water stress
to examine how they have shifted with increasing cereal production.
We then use this information to evaluate several replacement scenar-
ios in which rice areas in each district are instead planted with alternative
kharif cereals and, in doing so, we seek to examine whether food security
goals and improvements in freshwater use can be achieved in tandem.
These scenarios are motivated by two key objectives of the Indian govern-
ment, namely, to alleviate undernourishment by increasing the supply of
nutritious foods (32) and to promote sustainable water resource manage-
ment in agriculture (33). Specifically, we consider four primary district-
level scenarios aligning with these objectives by replacing rice-harvested
areas with (i) the lowest total water footprint (WFP) crop, (ii) the lowest
blue WFP crop, (iii) the crop with the highest nutritional yield in
terms of protein, and (iv) the crop with the highest nutritional yield in
terms of iron and quantify what the changes in water use and nutrient
production would be. Finally, we examine an important potential policy
leverIndias Public Distribution System (PDS)by which these transi-
tions toward alternative cereal production and consumption could be
realized. In doing all of this, we can determine where and to what extent
efforts to promote alternative mixes of cerealsfor which there is local
knowledge regarding cultivation and consumptioncould simulta-
neously improve water use efficiency and nutrient availability in diets.
RESULTS
CWRs showed substantial variation both between crops and geograph-
ically (units are in mm H
2
Oyear
1
;Table1,figs.S1andS2,andtable
S1). As expected, we found that the highest total CWRs occurred for rice
and wheat and that demand for irrigation was more pronounced in arid
regions (for example, Rajasthan and Maharashtra; figs. S2 and S3). We
also observed high blue (irrigation) water requirements for all rabi
(non-monsoon, winter) crops as they must rely more heavily on irriga-
tion (Fig. 1).
Cereal production has grown by 230% from 1966 to 2009. Although
the combined production of alternative cereals (that is, those other than
rice and wheat) was larger than that of wheat in the 1960s, their relative
contribution to the cereal supply has steadily dwindled (fig. S4, A and
B). Yet, alternative cereals still disproportionately account for the supply
of protein, iron, and zinc among kharif crops (table S2 and fig. S5). At
the same time, total consumptive water demand for Indian cereal pro-
duction has increased from 482 to 632 km
3
H
2
Oyear
1
during the study
period; this increase has been driven almost entirely by a doubling of
consumptive blue water demand for wheat during the rabi season
(Fig. 1) and modest increases in cropping frequencies and cropland
extent (fig. S4, C and D). Not surprisingly, the largest increases in
consumptive water demand occurred in the states of Punjab and
Haryana, where irrigated rice and wheat production now occurs at com-
mercial scales. The continuing transition to rice- and wheat-dominated
croplands has also increased the proportion of crop water demand met
through irrigation, especially in the countrys northern states (Fig. 2, A
to D). When comparing consumptive water demand to long-term av-
erage renewable water availability (that is, water generated from annu-
al precipitation), we also observed that many districts were already
experiencing substantial water stress at the beginning of the time pe-
riod and that the burden of water stress has shifted away from south-
ern districts, some of which have experienced a decrease in crop water
demand, and toward districts located largely in Punjab and Haryana
(Fig. 2, E and F).
We also examined the water productivities [that is, WFP; cubic
meters of H
2
O consumed per ton of crop produced (hereinafter,
m
3
H
2
O ton
1
)] of the different cereals for the production of key nu-
trients. When using the conventional metric of WFP, we found that rice
(1490 m
3
H
2
Oton
1
) was by far the most inefficient blue water user
among the kharif (monsoon) crops and that the total WFP of sorghum
grown during the rabi season was nearly double that of wheat (Fig. 3).
In addition, rice was the least productive water user among monsoon
cereals when examining nutrient production, rivaling rabi (winter)
Table 1. National average CWRs weighted by district production.
CWRs (mm H
2
O year
1
) were calculated for each district using averaged
climate variables covering the years 2000 through 2009. Green CWRs for
rainfed crops are consistently higher than for irrigated crops because of
differences in the distribution of rainfed (R) and irrigated (I) cereal pro-
duction. Values in parentheses are the production-weighted SDs. Ellipses
indicate that the crop is not produced during a particular season.
Crop
Kharif Rabi
Green (R) Green (I) Blue (I) Green (R) Green (I) Blue (I)
Rice 641 (160) 570 (157) 307 (126) 263 (47) 189 (52) 622 (162)
Wheat ……321 (57) 272 (50) 517 (91)
Maize 439 (48) 415 (45) 49 (47) 259 (38) 181 (36) 237 (46)
Sorghum 425 (59) 400 (56) 44 (42) 220 (72) 146 (54) 179 (42)
Finger millet 424 (39) 400 (30) 59 (78) ……
Pearl millet 314 (129) 296 (119) 46 (60) ……
Fig. 1. Time series of consumptive water demand for Indian cereal production.
Consumption is disaggregated between precipitation on rainfed lands [Green wa-
ter (R)], precipitation on irrigated lands [Green water (I)], and irrigation water on
irrigated lands (Blue water).
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crops in the volume of blue water requiredper ton of calories, protein,
and zinc production and surpassing all crops for water requirements
for iron production. Maize consistently performed well across all nu-
trient metrics, particularly with regard to irrigation water productivity.
Together with the inefficiencies of rice, these results indicate that
greater incorporation of alternative cereals into the Indian food system
can offer considerable potential benefits in terms of nutrition and wa-
ter use, although it is important to note that, due to relatively low
yields, sorghum, pearl millet, and finger millet showed potential
trade-offs between water productivity and land use efficiency. Com-
bined with the differing geographies and climates that these cereals
currently occupy (fig. S1), these considerations necessitated compar-
isons at finer scales as the relative ranking of crops can vary widely
between districts (fig. S6).
With these potential trade-offs between water, land, and nutrition in
mind, we considered multiple district-level rice replacement scenarios
aimed at reducing consumptive water demand for kharif (monsoon)
cereal production, improving nutrient production from cereals, and
conserving the extent of cultivated land, all of which are goals of the
Indian government. We first replaced rice areas with the kharif cereal
having the lowest total WFP in each respective district, provided that
the replacing crop had a total WFP (m
3
H
2
Oton
1
) lower than rice
(Fig. 4, A and E), and found that, in doing so, it is possible for India
to substantially reduce consumptive water demand (21% for green
water and 32% for blue water; fig. S7); increase protein (+9%), iron
(+43%), and zinc (+28%) supply; and maintain calorie (+1%) pro-
duction (Fig. 4I). Much of these benefits for water and nutrition
came from relatively few districts, with half of total water savings
for this scenario coming from just 39 districts (table S3). The districts
that stood to benefit the most in terms of reduced water demand were
also those largely responsible for increases in nutrient production. This
additional nutritional supply from this scenario could serve to address
persistent deficiencies, particularly for iron (table S4) (23,25), and could
help to compensate for insufficient nutrient supply from other food
groups of the Indian diet. Performing replacements based on blue
WFPs yielded similar results, although with a modest reduction in
calorie supply (scenario 2; Fig. 5A and table S4). For both of these
scenarios, we found that nutrient production would be more evenly
distributed across the country (as opposed to being concentrated in
Punjab and Haryana) and that the largest increases in nutrient pro-
duction generally occurred in eastern India (fig. S8).
We also considered two scenarios in which rice was replaced by the
alternative kharif cereal with the highest nutrition yieldin terms of
either protein or ironwithin each district (Fig. 4 and table S4). Both
scenarios yielded similar results to the minimum WFP scenarios, with
substantial improvements in water use and in protein, iron, and zinc
production but with mixed outcomes for calorie supply (maximum
protein, +8.7%; maximum iron, 4.5%; Fig. 4I). Overall, the benefits
of rice replacement across all scenarios were more pronounced within
rainfed croplands and were largely attributable to relatively few dis-
tricts (Fig. 5 and table S3). The modest calorie reductions that occurred
in two of the four replacement scenarios were largely because the
yields of alternative cereals were on average lower than those for rice
(fig. S9 and table S7). However, it is important to note that, of the 296
districts where rice is cultivated, there are many instances where
alternative cereals achieve higher yields relative to rice (8 for finger mil-
let, 139 for maize, 36 for pearl millet, and 55 for sorghum). In all, there
are 149 districts where at least one of the alternative cereals considered
here attained a higher yield than rice (table S6). The high yields and low
CWRs of maize relative to the other alternative cereals made it the
Fig. 2. District-level changes in total consumptive water demand for cerea l production, blue water fraction, and water stress. Total consumptive water demand for cereal
production is compared for the beginning of the study p eriod [(A) 19661970] and the end of the study period [(D) 20052009]. (Band E) Blue water fractions for the beginning and end of
the study period are the ratio of consumptive blue water use to total consumptive water use for cereal production. Availabilityisthe long-term (19702000)average of available renewable
water, which originates from annual precipitation and contributes to stream flow and groundwater recharge. (Cand F) If the ratio of consumptive water demand to annual availability
exceeds unity, then the difference must be met through nonrenewable sources and can lead to the depletion of freshwater resources (for example, through groundwater pumping).
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dominant replacement crop in two of the four scenarios (scenario 1:
lowest total WFP; scenario 3: highest protein yield; Fig. 4 and table
S4). In many parts of the country, maize is not traditionally consumed
to the same extent as millets and sorghum, and cultural preferences will
strongly determine the realistic possibilities for alternative cereals, which
may differ in certain places from those selected by some of our scenarios.
In view of this, we also imposed additional constraints on the replacement
scenarios (that is, nutritional yield of replacing crop in terms of calories
must be higher than rice and/or maize could not be considered as a
replacement) and generally observed the same benefits of replacement,
though of a smaller magnitude. In a few cases, trade-offs began to
emerge between water savings and nutrient supply at the national level,
highlighting the need for selective, well-considered, and location-specific
strategies to promote alternative cereals (table S4).
As a final note, information on actual irrigation water withdrawals in
India beyond country-level estimates is not available (34). As such, our
study examines blue water demand and potential blue water savings, an
approach that is widely used to compare the water use intensities of dif-
ferent crops and to provide insights into less water-demanding cropping
choices (3,18,28,3538). Depending on pumping capacity and irriga-
tion source for an irrigated field, a farmers actual irrigation availability
may fall below a crops irrigation water requirement (that is, the volume
of irrigation water required to prevent crop water stress) and would
mean that a crop shift may in reality realize lower or no blue water sav-
ings. However, in many cases, a transition to a crop that requires less
irrigation water will not only result in real water savings but also leave a
farmers crops less exposed to potential water stress.
DISCUSSION
A substantial increase in rice-wheat cropping, a system that depends
heavily on irrigation, has contributed to chronic water stress in many
parts of India (Fig. 2). There is widespread consensus (17,3941)that
these current practices, in combination with weakening monsoonal
rains (20,22), offer little possibility of long-term sustainability for water
use if India intends to continue to meet its cereal demand domestically.
Even for countries expecting little population growth in the coming dec-
ades, policies of food self-sufficiency can present substantial food-water
trade-offs. For instance, a recent study of neighboring Sri Lanka showed
that the countrysfreshwaterresourceswillbeinsufficient to sustainably
supply the irrigation water required to continue maintaining rice pro-
duction above domestic demand (42). For a country such as India,
which will need to feed a projected 394 million more people by 2050
(43), the potential for undesirable trade-offs between food security
Fig. 3. Water productivity (m
3
H
2
O) of nutrient production for total, blue, and green WFPs. Values correspond to the years 2000 through 2009 and represent the ratio
of conventional WFPs on irrigated cropland [(A) that is, m
3
H
2
O ton
1
] to nutrient content (that is, amount of nutrient per ton of crop) for (B) calories, (C) protein, (D) iron, and
(E) zinc. Blue fraction (F) is the ratio of blue WFP to total WFP.
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and environmental sustainability is profound. Yet, our findings demon-
strate that India can alleviate these difficult decisions by exercising flex-
ibility in the types of cereals it produces and consumes.
Recent decades in India have shown that widespread changes in ce-
real mixes are possible within relatively short time periods. While there is
still considerable consumption of alternative cereals in certain regions of
the country (fig. S10), the continuing shift toward rice-wheat cropping
and consumption indicates a substantial influence from the countrys
PDS (44), a program that leverages the countrys tight linkages between
food production and diets to promote food security for low-income
households and livelihood support for smallholder farmers. By providing
a guaranteed Minimum Support Price to producers and placing heavy
subsidies on rice and wheat at the consumer end, this system has also
served to influence cropping and dietary choices away from more
nutrient-rich alternative cereals and is an important factor contributing
to the persistence of widespread nutrient deficiencies (25,44).
By using similar policy mechanisms to transition to a greater reliance
on other cereals, India can potentially realize important benefits in terms
of both reduced consumptive irrigation water demand and increased
production of key nutrients. Of course, there are multiple factors that
dictate a farmers crop choice and a households consumption basket,
and some of the reasons that producers and consumers may prefer rice
and wheat may be difficult to influence. These considerations are essen-
tial for identifying where efforts aimed at increasing alternative grains
may complement local priorities and preferences. With these very real
challenges in mind, certain states (for example, Karnataka and Odisha)
have initiated state-level pilot programs that will procure selected alternative
cereals from farmers under their PDS programs. The removal of these
Fig. 4. Outcomes of selected rice replacement scenarios. Maps show the districts in which rice-harvested areas were replaced by kharif crop with (Aand E) the lowest
total WFP in each district(scenario 1), (Band F) the lowestblue WFP in each district (scenario 2), (Cand G) the highestnutritional yield in termsof protein (metric tons of protein
per hectare), and (Dand H) the highestnutritional yield in terms of iron(kilograms of iron per hectare). (I)Solid columns correspond toirrigated areas, and patterned columns
correspond to rainfed areas. Values are reported as percent changes relative to current levels of water demand and nutrient supply. Changes in water demand are separate
between blue water (blue) andgreen water (green). Becausewe made no replacements in rainfed rice areas under the replacement scenariobased on blue WFPs (scenario 2),
there are no rainfed bars for this scenario. Current levels of water demand and nutrient production and the levels of minimum nutrient production required from cereals to
meet daily recommended intake (DRI) for the country (if there were no limitations on access and distribution and no losses or waste) (23) are reported in tables S2 and S3.
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economic barriers (by which government procurement is only offered for
rice and wheat) will therefore provide invaluable information on the will-
ingness of farmers and households to increase alternative cereals in their
production and consumption baskets.
It is clear that further work is needed to fully understand the suite of
factors influencing cropping and dietary choices and their economic,
nutritional, and environmental implications, and this study addresses
importantaspectsoftheseknowledgegaps.Wehaveshownthat
potential benefits of transitioning toward alternative cereals exist for
bothrainfedandirrigatedsystems,where substantial reductions in con-
sumptive water demand are complemented by increased nutrient pro-
duction (table S4). In addition, by improving water productivity for
cereal production during the kharif (monsoon) growing season, more
freshwater may be made available for rabi irrigation as well as for
environmental flows and domestic, municipal, and industrial uses. Fur-
ther, incorporation of alternative, less water-demanding cereals can help
to increase crop diversity in Indian cereal production and reduce vul-
nerability to dry spells in places where freshwater resources for supple-
mentary irrigation may be less readily accessible and can potentially
enhance the resilience of the food system against future uncertainties
associated with climate change [for example, (30)].
Our replacement scenarios also demonstrate that efforts at
improving alternative cereal production can help to more equally
distribute nutrient production across the country and thereby reduce
the impact of a single local climate shock to national grain production.
This decentralization of nutrient productionaway from Punjab and
Haryanathat these alternative cereals would afford would also repre-
sent a reversal of the trend in which cereal production (fig. S11) and
water consumption have shifted away from southern states and served
to enhance already existing water stress in the north (Fig. 2).
The potential food-water benefits demonstrated in this study were
all realized while maintaining the current extent of cropland (that is, no
agricultural expansion). Such a consideration is vital in a country with
high population density and intensive pressure on land resources. Al-
though we were able to constrain cultivated area, in certain cases, we
found that important trade-offs exist between efficient land and water
use for nutrient production (fig. S9) and that the magnitude of potential
benefits from rice replacement and the choice of alternative crop varied
widely between districts (fig. S6B and Fig. 4). While all replacement sce-
narios generally realized benefits for water use and nutrient supply, even
a slight reduction (as occurred in certain cases for calories) may not be
an acceptable outcome for a country in which nutrient supply is generally
Fig. 5. Cumulative water savings and changes in nutritional output. For each rice replacement scenario (Sc1, Sc2, Sc3, and Sc4), districts were ranked based on
volume of water savings from smallest to largest and plotted against their associated changes in the supply of (A) calories, (B) protein, (C) iron, and (D) zinc.
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inadequate. Thus, in a country such as India, where a high fraction
of people continue to be undernourished, policy-makers may seek to
selectively encourage the production and consumption of alternative
cereals only where these undesirable trade-offs will not occur. In the
near term, efforts at altering the mix of cereal production should focus
on those states in which farmers are already able to achieve relatively
high yields for alternative cereals, thereby avoiding any undesirable out-
comes for nutrient production, particularly for calories. Many of the
trade-offs between nutrient supply and water use efficiency can be
eliminated by focusing agricultural research on further improving yields
of these alternative cereals and would almost certainly ensure greater
improvements in nutrient production as well. Yet, even with these rel-
ativelylowyields,maize,sorghum,pearlmillet,andfingermilletgen-
erally contributed to reductions in consumptive water demand and
improvements in nutrient production under the rice replacement sce-
narios considered in this study (Fig. 5).
There are certainly a host of other considerations, beyond water and
land use and nutrient production, that factor into agricultural policy
and consumer choices, and the crops, environmental impacts, and nu-
trients included in such an analysis must be selected according to each
situation. For Indian cereals in particular, there are several aspects of
production and consumption that our analysis does not include but
which are important for fully understanding the nutritional, economic,
and environmental implications of shifting cropping patterns. As one
example, rice residues serve as an important source of animal fodder,
and animal products in turn provide key sources of protein and iron to
theIndianpopulation.Thereisalargebodyofliteratureshowingthat
alternative cereals (and their residues) can readily be used as feed and
fodder, that their nutritional qualities as feed and fodder exceed that of
rice and rice residues, and that their use to support animal production
already occurs across India [for example, (4552)].
Further studies on dimensions such as greenhouse gas emissions and
input costs, storage and transport costs, labor requirements, and dietary
preferences are also required before any policy recommendations can
responsibly be made. Studies that incorporate optimization approaches
to develop trade-off frontiers can also help to reconcile these multiple
objectives. While future work on these other factors is still needed, the
cereals considered here offer great promise for improving water use and
nutrient production while conserving agricultural extent. As such, the
holistic approach that we have presented, in which multiple dimensions
are considered in tandem, provides a mechanism for incorporating oth-
er economic and cultural dimensions into an integrated framework for
sustainable decision-making. The outcome of this study demonstrates
that nutrition and environmental outcomes need to be considered
together, that existing policies can be used to achieve food-environment
co-benefits in one of the worlds most populous countries, and, more
generally, that solutions for achieving sustainable intensification in
any country are most effectively achieved if based on analyses of
trade-offs and synergies across multiple dimensions.
CONCLUSION
Nations are increasingly facing challenges of increasing food production
while simultaneously minimizing resource use and environmental im-
pacts. This is certainly the case for India where historical trends in cereal
production have contributed to widespread water stress and nutrient
deficiency. Our study demonstrates that replacing rice with other cer-
eals, for which local knowledge on their production and consumption
already exists, can offer distinct benefits in terms of both reducing
freshwater use and enhancing nutrient production. This case study of
India provides an example of how a multidimensional approach can be
used in other places to assess sustainability goals at the interface of food
security and the environment, to understand and avoid undesirable
trade-offs, and to better link science with policy.
MATERIALS AND METHODS
Data
We examined the water use and nutrient content of rice (O. sativa),
maize (Z. mays), wheat (T. aestivum), sorghum (jowar; S. vulgare), pearl
millet (bajra; P. typhoideum), and finger millet (ragi; E. coracana), which
constitute nearly all of Indias cereal production (15). Data on district-
and crop-specific production, harvested area, and irrigated area were
taken from the International Crops Research Institute for the Semi-Arid
Tropics Village Dynamics in South Asia (VDSA) mesoscale data set
(31). These data are reported annually for the years 1966 through
2011 and use 1966 district boundaries. Data for the years 2010 and
2011 were incomplete and were not included in this study. While there
has been substantial modification to district boundaries since 1966, the
data provided in VDSA currently cover 593 of Indias 707 districts and
87% of the countrys land area. National values for nutrient content
were taken from the newly released Indian Food Composition Tables
(table S8) (53). Year 2011 district-level consumption data for each cereal
came from the Indian National Sample Survey (table S6) (24). National
DRI values for calories, protein, iron, and zinc came from IndiasNa-
tional Institute of Nutrition (23).
Information on actual water withdrawals or pumping rates is not
available for India, and estimations of CWRs provide the best alternative
in examining the water needs of farmers across the country. CWRs were
calculated for each district at monthly time steps for the years 2000
through 2009 and were split between blueand greenCWRs, where
green water is supplied through rainfall and blue water is supplied
through irrigation (2). Blue water represents a crops consumptive water
demand in excess of what is provided through precipitation and is only
used in calculations of consumptive water demand within irrigated
areas. In reality, farmers with access to irrigation may not be able to fully
meet the irrigation water demand of their crops, as limited by pumping
rates and irrigation source. This means that, if a farmer pumped at max-
imum capacity but was still unable to obtain sufficient irrigation water
to meet the blue water requirement of any of the crops considered here,
the actual water use for the field would not change. For those farms where
irrigation availability is only insufficient for the most water-intensive
cereals, a shift to crops with lower water requirements will result in an
actual reduction in irrigation water use. It is also clear that, if a farmer
transitions to a crop with a lower blue water requirement, regardless of
the irrigation water available to that field, this crop will be less exposed
toconditionsofwaterstressduringdryyearsordrought.
Precipitation data came from the Indian Meteorological Depart-
ments daily rainfall product (1.0° × 1.0°) (54). Mean daily temperatures
were taken from the University of East Anglias Climate Research Unit
Time Series version 3.24.01 data set (0.5° × 0.5°) (55). Monthly wind
speed and relative humidity data came from the National Oceanic and
Atmospheric Administration/Oceanic and Atmospheric Research/Earth
System Research Laboratory Physical Sciences Divisions National
Centers for Environmental Prediction Reanalysis product (2.5° × 2.5°)
(56). Soil information (sand, silt, and clay fractions) came from the In-
ternational Soil Reference and Information Centres30arc sec SoilGrids
database (57). Data for net radiation at the surface (which also accounts
SCIENCE ADVANCES |RESEARCH ARTICLE
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for soil heat flux density) were taken from NASAs Global Land Data
Assimilation System Noah Land Surface Model L4 monthly, Version 2.0
(0.25° × 0.25°) (58). Crop coefficients, climate zones, and growing stages
were adapted from Mekonnen and Hoekstra (35) and Kottek et al.(59)
(table S9 and fig. S12). State-level planting dates were determined by
combining information from the Indian Meteorological Department
(60), Portmann et al.(61), and Mekonnen and Hoekstra (35)(table
S10). Growing stages for each district were shifted to align with both
the crop coefficient values for the particular climate zone in which that
district was located and the estimated planting date of that districts
state. The same values for crop coefficients, growing stages, and planting
dates were used for both pearl millet (bajra) and finger millet (ragi).
Estimating atmospheric demands on crops
Reference evapotranspiration, ET
o
, was calculated for each district at
monthly time steps using the Food and Agriculture Organization of
the United NationsPenman-Monteith equation (36)
ETo¼0:408DðRnGÞþg900
Tþ273 u2ðeseaÞ
Dþgð1þ0:34u2Þð1Þ
where R
n
is the net radiation at the crop surface (MJ m
2
day
1
); Gis the
soil heat flux density (MJ m
2
day
1
); Tis the mean daily air tempera-
ture at 2 m (°C); u
2
is the wind speed at 2 m (m s
1
); e
s
and e
a
are the
saturation and deficit vapor pressures, respectively (kPa); Dis the slope
vapor pressure curve (kPa°C
1
); and gis the pyschrometric constant
(kPa°C
1
). The actual evapotranspiration (ET
a
)ofcropion day twas
then calculated as
ETa;i;t¼kc;i;tks;i;tETo;tð2Þ
where k
c,i,t
is the crop coefficient of crop icorresponding to the month
in which day toccurs (table S9) and k
s,i,t
is the water stress coefficient
calculated following Allen et al.(36) as a function of the soil water con-
tent in the root zone (S
i,t
), the maximum and actual water content in the
root zone. Rooting depths for irrigated and rainfed crops came from
Siebert and Döll (37)(tableS11).Forcropion day tunder water-stressed
conditions (that is, when only precipitation was provided), k
s,i,t
was
evaluated as
ks;i;t¼
Si;t
ð1piÞSmax;i
if Si;t<ð1piÞSmax;i
1ifSi;tð1piÞSmax;i
8
<
:
ð3Þ
where S
i,t
is the depth-average soil moisture (expressed as a length),
S
max,i
is the value of available soil moisture, and p
i
is the fraction of
S
max,i
that a crop can uptake from the rooting zone as calculated in
Allen et al.(36) and Siebert and Döll (37). For conditions of no water
stress (where supplementary irrigation is available), k
s,i,t
was as-
sumed to be 1 (35,37). For a given crop and grid cell, soil moisture
(S
i,t
) was calculated by solving a daily soil water balance
Si;t¼Si;t1þDtðPeff;tþIi;tETa;i;tDi;tÞð4Þ
where S
i,t1
is the soil moisture of the previous time step, Dtis equal
to 1 day, P
eff,t
is the effective precipitation (that is, the rainfall that is
actually absorbed in the soil and not directly evaporated from the
surface), I
i,t
is the additional irrigation water (used only in the case
of irrigated crops), and D
i,t
is deep percolation below the root zone
(which occurred when soil moisture exceeded field capacity, that is,
the volume of water that can be retained in the soil). Daily precipi-
tation was converted to P
eff,t
using the Soil Conservation Service
method [see, for example, (35,36,62)].
Thus, for each day, each crop, and each district, we were able to
calculate a stressed ET
a,i,t,s
(equal to the green consumptive water use)
and unstressed ET
a,i,t,u
(equal to the actual evapotranspiration under
no water stressed). Blue consumptive water use was calculated as the
difference between ET
a,i,t,s
and ET
a,i,t,u
and was only considered for
irrigated areas. We then took a summation of the daily green and blue
consumptive water use across a crops entire growing season to deter-
mine total green (for rainfed and irrigated crops) and blue (for irri-
gated crops only) consumptive CWR, averaged across the years 2000
through 2009 (table S1). These definitions of green and blue consump-
tive water use are consistent with standard methodologies of WFP
calculation [for example, (35)].
Estimating historical consumptive water demand and
water stress
Green consumptive water demand (CWD
green
) for cereal production
was estimated annually for each district jas
CWDgreen;j¼10ðCWRgreen;i;jai;jÞð5Þ
where CWR
green,i,j
is the green CWR (mm H
2
Oyear
1
)ofcropi,a
i,j
is
rainfed area (ha) in district j(calculated as the difference between har-
vested area and irrigated area), and the factor of 10 ensures that the
units are in cubic meters of H
2
O per year. This calculation was re-
peated using the blue CWR and crop-specific irrigated area to deter-
mine the consumptive (blue) irrigation water demand. The irrigated
area data from VDSA had some missing values, which we linearly in-
terpolated. If data were missing at the beginning or end of the time
period, then these values were linearly extrapolated based on the im-
mediately succeeding or preceding 10 years, respectively. Complete data
for crop-specific district-level irrigated area in West Bengal were only
available for the years 1966, 1967, 1983, 1985, and 1988 from VDSA.
To ensure that our estimates were conservative, we took the ratio of
irrigated area to harvested area for each of these years, averaged these
ratios across the 5 years of available data, and applied this constant
irrigated/harvested ratio to all years. Because the VDSA crop produc-
tion data set does not distinguish between kharif and rabi production
for rice, maize, pearl millet, and finger millet, we used the CWRs for
the kharif season for these crops to estimate total consumptive water
demand. This assumption is supported by crop production data re-
ported by season from the Directorate for Economics and Statistics
(63), which shows that millet production during rabi is negligible
and that only for selected states (for example, rice in Andhra Pradesh,
Odisha, Tamil Nadu, and West Bengal, and maize in Andhra Pradesh,
Bihar, Madhya Pradesh, and Tamil Nadu) is rabi production substan-
tial for rice or maize. Wheat is exclusively produced during the rabi
season with certain states producing small amounts of cereals outside
of the kharif and rabi growing seasons.
Water stress was calculated as the ratio of total consumptive water
demand for cereals to the long-term average renewable water availability
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for each district. Watershed-level data on renewable water availability
(surface + groundwater) cover the years 1970 through 2000 and came
from Brauman et al.(4) who used the WaterGAP3 integrated global
water resources model. These data do not account for interbasin
transfers or desalination. Brauman et al.(4)defineavailable
renewable water as water generated [from precipitation] within
the watershed and inflows from upstream that are stored or pass
through rivers or move from the land surface into aquifers (renewable
groundwater).Using long-term average renewable availability allows
for an examination of whether freshwater withdrawals and consump-
tion can be sustained by a watershed through time. If consumptive
water demand consistently exceeds the average renewable water avail-
able (and that is able to recharge annually), then the difference must
be met through nonrenewable sources (for example, groundwater
pumping) and can lead to the depletion of surface and groundwater
sources.
Replacing rice with alternative cereals
Rice replacement scenarios were based on the years 2000 through 2009
to align with the time period used for WFP calculations. Replacements
were carried out separately for rainfedandirrigatedcroplands.Under
all replacement scenarios, we assumed that the water resources available
to rice fields would then become available to the replacing crop. To
explore how increased production of alternative cereals may benefit
outcomes for water demand and nutrient production, we examined
four district-level scenarios by replacing rice in rainfed and irrigated
areas with (i) the alternative cereal with the lowest total WFP, (ii) the
alternative cereal with the lowest blue WFP, (iii) the alternative cereal
with the highest nutritional yield in terms of protein (metric tons of
protein per hectare), and (iv) the alternative cereal with the highest
nutritional yield in terms of iron (kilograms of iron per hectare). For
rainfed areas in scenario 1, green WFP was equal to total WFP. By
replacing rice-harvested areas (instead of rice production), we were
able to conserve agricultural extent and avoid any agricultural exten-
sification. For scenario 1, the alternative cereal with the lowest total
WFP in a given district replaced rainfed rice. If this crop had a total
WFP higher than that of rice, then no replacement occurred for
rainfed rice areas in that district. This scenario was applied separately
to irrigated rice areas. For scenario 2, the alternative cereal with the
lowest blue WFP in a given district replaced irrigated rice. If this crop
had a blue WFP higher than that of rice, then no replacement
occurred for irrigated rice areas in that district. This scenario was
not applied to rainfed rice areas. For scenario 3 and scenario 4, the
alternative cereal with the highest nutritional yield (in either protein
or iron, respectively) replaced rainfed rice, provided that the nutritional
yield of the replacing crop was higher than that of rice. Additional
supplementary constraints were also applied to all of the scenarios
described above (table S4). These constraints were that a rice repla-
cement could only occur if the replacing crop also had a nutritional
yield in terms of calories (kilocalories per hectare) that was higher
than that of rice and/or that only finger millet, pearl millet, or sorghum
could be considered as replacing crops. In all replacement scenarios,
we assume that the water resources available to rice are then made
available to the replacing crop.
Combining water use and nutrition
The conventional measure of WFP uses the units of cubic meters of
consumptive water demand per ton (for example, m
3
H
2
Oton
1
)
(58). To examine whether the relative ranking of crops changed in terms
of water productivity, we calculated the nutritional WFP values of crop i
in district jas
WFPi;j;n¼10CWRi;jai;j
pi;jci;n
ð6Þ
where p
i,j
is production (metric tons) and c
i,n
is the crop content of
nutrient n(nutrient per ton of crop). We used the nutrient content values
reported for the most consumed form of each crop (table S8). Under all
scenarios, the production of nutrient nin district jwas calculated as
pn;j¼ðci;nyi;jai;jÞð7Þ
where y
i,j
is the yield of crop iand a
i,j
is the intended (irrigated or
rainfed) area for crop i. Total minimum nutrient production required
to meet DRI for the country (if there were no limitations on access and
distribution and no losses or waste) was calculated by Rao et al.(25)
basedonIndianDRIs(23),whichdependonageandgender,andyear
2011 population statistics. Minimum required nutrient supply from
cereals was then calculated as the product of total minimum required
nutrient production for the entire Indian diet and the fraction of nutri-
ents provided by cereals under current consumption patterns (table S4)
(25). The minimum required nutrient supply used here assumes no lim-
itations on access and distribution and no losses or waste; actual nutri-
ent supply within the country would need to be above these values to
overcome these barriers. DRI values were not provided for dietary fiber.
SUPPLEMENTARY MATERIALS
Supplementary material for this article is available at http://advances.sciencemag.org/cgi/
content/full/4/7/eaao1108/DC1
Table S1. CWRs by district (mm H
2
O year
1
) for rainfed and irrigated crops.
Table S2. National production changes for kharif (monsoon) cereals under replacement scenarios.
Table S3. Cumulative water savings and changes in nutritional output from replacement scenarios.
Table S4. Outcomes and descriptions of rice replacement scenarios.
Table S5. Cereal consumption by crop and by district.
Table S6. State-level yields of kharif crops and outcomes of rice replacement scenarios.
Table S7. Crop-specific nutrient content reported in the National Institute of Nutritions Indian
Food Composition Tables.
Table S8. List of crop coefficient (k
c
) values disaggregated by crop, climate zone, and month.
Table S9. State-level planting dates (month) for each cereal crop and growing season.
Table S10. Rooting depths for rainfed and irrigated crops as reported by Siebert and Döll (37).
Fig. S1. Geographic distribution of total CWR (mm H
2
Oyear
1
) of Indian cereals in irrigated lands.
Fig. S2. Geographic distribution of the fraction of total CWR of Indian cereals in irrigated lands
met by blue water.
Fig. S3. Map of states based on 1966 boundaries.
Fig. S4. Time series of Indian cereal production and extent.
Fig. S5. Kharif production fractions by crop.
Fig. S6. Comparison of blue water use and nutrient yields of kharif (monsoon) cereals.
Fig. S7. District-level water savings of scenario 1 (rice replacement with the lowest total
WFP cereal).
Fig. S8. Changes in nutrient production under scenario 1 (lowest total WFP).
Fig. S9. Current rice yield and yield differences of replacing crop on irrigated croplands.
Fig. S10. Ratio of most consumed alternative kharif cereal to rice.
Fig. S11. Iron as an example of change in per-capita nutrient production.
Fig. S12. Map of climate zones.
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work was supported by The Nature Conservancys NatureNet Science Fellowship.
Author contributions: K.F.D., D.D.C., A.C., B.R., D.S., and R.D. gathered the data. K.F.D., D.D.C.,
and M.C.R. performed the CWR analysis. K.F.D., A.C., and R.D. analyzed the data. All authors
wrote the manuscript. Competing interests: The authors declare that they have no
competing interests. Data and materials availability: All data needed to evaluate the
conclusions in the paper are present in the paper and/or the Supplementary Materials.
Additional data related to this paper may be requested from the authors.
Submitted 14 June 2017
Accepted 29 May 2018
Published 4 July 2018
10.1126/sciadv.aao1108
Citation: K. F. Davis, D. D. Chiarelli, M. C. Rulli, A. Chhatre, B. Richter, D. Singh, R. DeFries,
Alternative cereals can improve water use and nutrient supply in India. Sci. Adv. 4,
eaao1108 (2018).
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Alternative cereals can improve water use and nutrient supply in India
DeFries
Kyle Frankel Davis, Davide Danilo Chiarelli, Maria Cristina Rulli, Ashwini Chhatre, Brian Richter, Deepti Singh and Ruth
DOI: 10.1126/sciadv.aao1108
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... A central question is whether a shift in grain procurement by the Government could economically achieve the national food security targets while addressing groundwater stress, the highly variable climate, and be economically feasible. Recently, Davis et al. 12,13 illustrated that India could improve water use and nutrition by shifting crops. This confirms our earlier results for purely rain-fed agriculture 14,15 . ...
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