A Wikiblog E-Book by Norman Uphoff with many others
Chapter 12: INCREASING CROP RESISTANCE TO CLIMATE AND OTHER STRESSES WHILE ABATING CLIMATE CHANGE
Farmers have always had to contend with many and diverse stresses, factors that can constrain or even destroy their crops. These stresses are commonly classified as either biotic, meaning they have biological origins such as insect pests or disease vectors, or as abiotic, constraints emanating from the climate, soils, or other inanimate sources. Coping with stresses is what farmers do.
Most stresses, if not exactly predictable, are anticipatable, and farmers prepare themselves to deal with these as best they can whenever they occur. Farmers in the 21st century have much better knowledge, resources and tools than their predecessors had for dealing with most stresses. However, set against this progress is a worsening situation where the stresses that stem from climate change are becoming more and more serious, and potentially devastating.
Much as modern technology has tried to make agriculture into an industrial enterprise, minimally affected by natural intrusions and vulnerabilities, agriculture remains an essentially biological undertaking. It depends on and capitalizes upon existing biological processes and potentials that have robustness and can be prolifically productive. But these processes and potentials have their limitations and are susceptible to deterioration, degradation, and demise.
Starting in the latter decades of the 20th century, scientists and then policy makers and the general public became aware of the dynamics of global warming and climate change. This is a large subject, and for the sake of our story-telling, we will not digress into a discussion of these trends. It is enough to note that the agricultural sector is terribly vulnerable to and affected by changes in temperature and rainfall, and by what are called euphemistically ‘extreme events,’ that is, droughts, floods, severe storms, cold snaps, and other such occurrences.
Unfortunately, changes in weather are also often accompanied by changes in the incidence of and damage from pests and diseases. These can become more common and more severe due to certain changes in temperature and precipitation. So, stresses of biotic and abiotic origins are likely to be correlated.[1]
Some of these changes can be difficult to measure and interpret. Trends are seldom simple and without contrary occurrences. Because farmers must live with and are affected by changes in climate – earlier or shorter growing seasons, greater variability of rainfall, increasing pest problems – these changes are more real for them than any statistics or charts.
There are also other stresses that farmers must contend with. Shifts in market forces can confront farmers with lower farmgate prices for their produce or with unexpected increases in their costs of production. There can suddenly be higher wages or labor shortages, or failures in the transportation system. But these are ubiquitous, and then on top of these, farmers are faced with the increasing stresses resulting from climate change.
While global warming is an adverse factor, it is relatively gradual, and it creates some winners as well as some losers. Climate variability is a more serious problem for farmers than is warming as such. Times for planting and harvesting are easier to adjust than taking steps to deal with the extremes of precipitation (drought or flooding) or temperature (hot spells and cold snaps). The effects of climate change have been increasing in both magnitude and frequency over the last several decades during which SRI has been gaining attention and acceptance.
In the contemporary situation, there has been growing interest in and policy support for what is called ‘climate-smart agriculture’: revising agricultural practices, investments, technology, institutions, and thinking to make food production less vulnerable to the exigencies of climate change. This has not been without some controversy.[2] But the basic ideas defining the concept of climate-smart agriculture (CSA) are unassailable, based on three straightforward objectives.
In the decades ahead, we must find ways to make our agricultural practices (a) more productive, achieving higher output per unit of input, while at the same time making agriculture better able to (b) adapt to climate change, succeeding in spite of the hazards and constraints that climate change imposes, and (c) mitigate the forces that are driving climate change.[3] This latter focus is primarily on reducing the greenhouse gas (GHG) emissions that emanate from agricultural activity.
Probably no other agricultural practice or strategy can meet all three of these objectives more broadly and directly than does SRI. It raises production while enabling farmers to adapt to the pressures of climate change while also countering the forces of climate change by reducing GHG emissions.[4] It also contributes to the sustainability of food production by reducing crop water requirements when climate change is making this resource scarcer and/or less reliable.[5] And it also reduces reliance on agrochemical inputs, upon which ‘modern’ agriculture depends, thereby improving soil health and water quality.[6]
These changes are made possible and productive by mobilizing inherent potentials that exist in crop plant genomes (Chapter 10). How and why this occurs is not yet fully understood, but we expect that the basic drivers include the greater growth of SRI plants’ root systems and the promotion of microbial abundance and activity in the soil, as this contributes to plants’ more efficient metabolism and systemic resistance to pests and pathogens (Chapters 4 and 5).
In this chapter there is no attempt to discuss all of the effects that SRI management induces. Rather, the major hazards associated with climate change are reviewed. These hazards have proved to be less deleterious to SRI-grown crops. Some of the same kinds of effects have been seen when applying SRI ideas and methods to other crops, reviewed in Chapter 14. But the evidence for other crops is still more anecdotal than it is for rice grown with SRI methods.[7] Rice under SRI management can show remarkable resistance to drought and water stress, to storm damage and lodging, to pest and disease damage,[8] and to cold temperatures. At the same time, SRI modifications in crop management also reduce the net emissions of greenhouse gases from paddy fields that are contributing to both global warming and to climate change.
DROUGHT TOLERANCE AND GREATER WATER PRODUCTIVITY
The most widespread effect of climate change is to make precipitation more variable and more unpredictable. Water supplies for growing irrigated rice are usually limited and scarce relative to demand. One of the first reports I had from farmers that their SRI-grown plants could resist water stress was from Sri Lanka. In 2003 I visited a farmer named Nimal and took the picture below of him standing between two adjacent rice fields, both planted at about the same time with the same variety of rice.
The supply of irrigation water had stopped, and there had been no rain (in the rainy season) for several weeks. The field on the left was started with seedlings transplanted when they were young, spaced singly and 25 cm apart, with supplementary irrigation provided intermittently to the field. Having received a good supply of organic matter, the soil was well-structured and better able to retain water than the soil on the right which had been supplied with chemical fertilizer. The organically-enriched soil on the left encouraged and supported more and deeper root growth, able to tap reserves of water at lower depths. Nirmal’s experience made a strong impression on me.
Several years later we got large-scale evidence from China at the provincial level, documenting SRI plants’ resistance to water stress, provided by Dr. Zheng Jiaguo from the Academy of Agricultural Science. After Zheng and other scientists in Sichuan province had evaluated and demonstrated SRI methods at the suggestion of Prof. Yuan Longping, they got the Provincial Department of Agriculture to begin promoting SRI use in that province in 2004.
In the first year, the Department recorded SRI use on just 1,133 hectares. Within six years, this area had spread to more than 300,000 hectares, with an overall yield increase during this period of 23%, on top Sichuan’s already-high average. The value of Sichuan farmers’ incremental yield from SRI methods, 1.66 million additional tonnes of paddy rice, was estimated to be worth more than US$ 300 million, produced with 25% less consumption of water.[9]
Of relevance here is that during this period, there were two drought years, 2006 and 2010. In these two years, the yield advantage of the SRI-managed rice fields was 12% greater than the average SRI yield advantage in the other five years. The average SRI yield in the climate-stressed years of 2006 and 2010 was just 1% less than the average SRI yield in the five normal-rainfall years. And in the two drought years, SRI yields were 20% higher than farmers’ average rice yield with usual methods and typical weather.[10]
At the field level, a relevant evaluation was done in Sri Lanka by a team from the International Water Management Institute (IWMI) in the 2003/04 maha (main) season. This followed up on the team’s research summarized in Chapter 7. The IWMI analysis showed how well an SRI rice crop could bear up under the stresses of drought. A larger evaluation had been planned for that season, but the team had to change its plans because of widespread crop failure due to drought in the study area that year (75 days of severe water stress). Instead of a large study, the team studied the experience of 12 farmers who had managed to grow a crop in that water-short season, 7 of them with SRI methods, and 5 with their usual practices.
It was found that 80% of the tillers on SRI-grown plants had formed panicles and produced grain, while only 70% of the tillers on plants raised with usual farmer methods had succeeded in this. In this drought-stressed season and even though the farmer-practice fields had 10 times more rice plants per m2, the number of panicle-bearing tillers per m2 was 30% higher in the SRI fields. Also, the SRI plants had more grains per panicle, 115 vs. 87. These differences contributed to an average SRI yield that was 33% higher in that season compared to the yield with conventional methods, 6.37 tonnes per hectare vs. 4.78 tonnes per hectare.[11]
At the plant level, we saw in Chapter 9 from research in India how rice plants grown with SRI methods are more water-efficient in their photosynthetic production of carbohydrates. Per millimol of water transpired, SRI plants fixed more carbon dioxide to produce more than twice as much photosynthate: 3.6 micromols compared to 1.6 micromols in the regular rice plants. This means that the water-use efficiency and drought-resistance associated with SRI management can be seen from the level of the plant up to the provincial level.
A study by the SRI Secretariat in Bhubaneswar, supported by the Tata Trust in India, did an evaluation of the impact of serious drought in the 2009 kharif season in northern India, when rainfall was 23% below normal. SRI yields across seven states were 45% higher on average than the yields from comparable rice fields managed with conventional practices.[12]
In 2012, a meta-analysis was done at Cornell of all the studies that could be found in the published literature on SRI which had enough detailed data on water productivity to conduct an in-depth, quantitative evaluation. On-line literature searches identified 29 studies from eight countries, with 251 comparison trials, that met the criteria for sufficient, analyzable data.[13]
All units of measurement were standardized to permit cross-study assessments of water use, water saving, and water productivity, comparing SRI results to the recommended practices in the respective countries.[14] For 17 of the studies, it was possible to disaggregate the total water used for rice production into its two components, respectively, total rainfall, and irrigation water.
Total water use in the SRI trials, which were more productive than the comparison plots, was 12.03 million liters per hectare, compared with 15.33 million liters. This difference of 3.3 million liters per hectare represented a total water saving of 22%. Considering just irrigation water consumption, as rainfall was the same for all of the paired trials, SRI use was 7.2 million liters per hectare vs. 11.1 million liters. This 3.9 million liter difference represented a 35% reduction in irrigation water consumption, supporting grain yield 11% higher on average.
Considering water requirements in terms of paddy production, total water productivity under SRI management was 52% higher. SRI methods (not necessarily their full use) produced 0.6 grams of paddy rice per liter of water, while researchers’ preferred methods yielded 0.39 grams per liter on average. The productivity of irrigation water was increased by even more, by 78%. SRI practices yielded 1.23 grams of paddy rice per liter of irrigation water while non-SRI methods gave 0.69 grams of rice on average.[15]
Further analysis of the data base showed that these advantages of water saving and water productivity under SRI management were manifested across widely-varying contexts for rice production. The meta-analysis considered differences in water use efficiency across variations in climate; in soil texture and soil pH; in cropping season (wet vs. dry); and in the rice variety planted (length of the crop cycle). Lower water requirements and greater water productivity with SRI were seen across all of the environmental and varietal differences. The measured improvements in water use efficiency associated with SRI management were also tested and confirmed by multivariate regression analysis.
It should not be surprising that rice or any other crop plants which have larger, healthier root systems are more drought-tolerant and even more drought-resistant. And if the soil in which the roots are growing is well-structured and well-endowed with organic matter, both living and dead, more water should be absorbed into and retained in the soil. Plants with larger, deeper root systems will have more access to this water, especially at lower depths. As noted in Chapter 4, when rice plants are kept always flooded, most of their roots remain within the top 10-20 cm, and soil dries out from the top layers first. So, SRI plants’ greater resilience under water stress is easy to understand as well as to see.
RESISTANCE TO STORM DAMAGE AND LODGING
This is something more easily seen than measured, but both visual and quantitative evidence of this benefit from SRI management are available. Storm damage is a significant hazard for any kind of rice production because when plants are blown over by wind or knocked down by rain, they are more difficult to harvest, and the harvest itself is reduced or lost.
When in China in 2002, I visited a rice seed-multiplication farm in Sichuan province where the farm manager happily pointed out how his SRI plots had withstood the wind and rain of a recent storm that had passed over, badly affecting his other rice fields.[16] In 2006, in Pakistan I saw fields in Punjab province where the plots of SRI basmati rice had withstood the force of a storm that lodged neighboring fields of conventionally-grown basmati.[17]
Pictures provided from various countries have shown this effect. The photograph below of trial plots at Tamil Nadu Agricultural University’s experiment station in India was shown by T.M. Thiyagarajan at the World Rice Research Congress held in Japan in November 2004, demonstrating SRI resistance to lodging on the TNAU experimental farm.[18]
The next year an iconic picture was sent from Vietnam which showed a woman farmer holding aloft two plants of the same variety -- one grown with SRI methods on the left and the other grown with usual farmer practices on the right -- in front of their respective fields after a tropical storm had passed over her village, located an hour’s drive north of Hanoi.[19]
SRI resistance to lodging was shown also in a GIZ-IFAD report on the introduction of SRI in the Mekong Delta.[20]
Here are rice fields in Taiwan and Colombia after storms, showing how the conventionally-grown rice plants became lodged, while the SRI rice plants resisted the stress of rain and wind. Similar pictures have been received from the Mwea irrigation scheme in Kenya, so this phenomenon has seen worldwide.[21]
The first published research on SRI resistance to lodging came from Japan.[22] This reported that 93% of the rice plants grown with conventional methods had lodged under wind stress compared to only 9% to 10% of those grown with SRI methods. Moreover, the SRI-managed plants that were blown over were only partially lodged, whereas nearly half of the conventionally-grown plants that lodged were pushed over all the way to the ground.
Various physical factors can explain such differentials. First, having stronger root systems obviously anchors the plants in the soil more effectively so they can better resist being blown over. We know that SRI plants develop better root systems. Also, when plants are more widely spaced, winds can pass between and past them more freely, not building up the force needed to topple them.
Several studies have made comparative measurements of the rice plants themselves that help to explain the observed differences in lodging resistance. The simplest measure is of tillers’ average thickness because having more biomass makes plants better able to resist the pressures of wind and rain. An evaluation in India, testing a number of varieties, found that the average circumference of tillers under SRI was 38% greater than that of rice plants of the same variety which had been grown conventionally.[23]
More sophisticated measurements can made of parameters that contribute to rice plants’ resistance or susceptibility to lodging. Measurements of ‘bending moment’ and ‘breaking resistance’ have been made by researchers first in Iran and then in China, as shown below. Internodes are the lengths (or sections) of a rice plant tiller (stalk) between its nodes (joints). Plants that have longer internodes are more vulnerable to lodging. Breaking under pressure is of course undesirable, but bending without breaking is beneficial.
The ‘bending moment’ is measured in grams per centimeter of internode length, and a low score reflects greater resistance to lodging. ‘Breaking resistance,’ on the other hand, is measured in grams per stem, and one wants a high score on this measurement. ‘Lodging index’ is calculated as a ratio between these two numbers, and a low score on this is desirable.
In the tables below, lower-case letters (superscripts) within each column show whether there was any statistically-significant difference between the numbers in that column, indicated by different letters. In both studies SRI plants had consistently and significantly more desirable scores than the plants grown with standard practices.
Lodging characteristics average for four Iranian rice varieties under different management[24]
Lodging vulnerability with different management and N applications (avg of two varieties) [25]
Such consistent effects of SRI practices on measurable phenotypical characteristics that confer greater resistance to lodging under the stresses of wind and rain make the stark differences seen in the pictures above more comprehensible.
PEST AND DISEASE RESISTANCE
The most systematic study of this was done in Vietnam by the Integrated Pest Management (IPM) program of its Ministry of Agriculture and Rural Development, which as noted in Chapter 9 took the lead in evaluating and introducing SRI in that country.
In the spring and summer seasons of the 2005-06 cropping year, the Ministry’s Plant Protection Division did on-farm comparison trials in 8 provinces, with side-by-side plots on which SRI or farmers’ usual methods were used to grow rice. Its staff monitored the incidence of the two most prevalent diseases and the two most common pests for rice crops.[26] As seen below, there were large differences in the prevalence of these scourges, which can become more severe under the temperature and precipitation effects of climate change.[27]
Similar reductions in rice plants’ susceptibility to insect pests had already been documented at Tamil Nadu Agricultural University in India (Chapter 7). But because this was thesis research it did not get the kind of attention that the above assessment received. The data above helped persuade the Vietnamese government to endorse the spread of SRI practices.
The TNAU research results shown below showed significant reductions in the incidence of pests both in an SRI nursery compared to a conventional nursery, and then in an SRI-managed field compared to regular rice management. The average reduction in nursery pests was 89%, while under field conditions after transplanting, the SRI reduction was 63%.[28]
There has been additional research documenting this effect,[29] but there are still systematic studies to be done that explain what are the mechanisms that make SRI rice plants less susceptible to the predation of pests and the debilitation of disease.[30] There is one theory, probably best considered as still a hypothesis because it is not widely accepted, that would explain at least in part how SRI management practices reduce rice plants’ attractiveness and vulnerability to pests and diseases, the latter often transmitted by insect or other biotic vectors.
This is the theory of trophobiosis, proposed by the French agronomist Frances Chaboussou, who spent most of his career working in France’s National Institute of Agricultural Research (INRA). His predictions are quite consistent with the facts and observations of SRI. His theory of trophobiosis proposes that plants’ susceptibility to infestation by pests and infection by disease is largely a consequence of the plants’ nutrition. Unbalanced or inappropriate nutrition, according to the theory, makes plants vulnerable, and indeed attractive, to predators and pathogens.
When plants are supplied with large amounts of inorganic nitrogen via synthetic fertilizer, they take up this N through their roots and will metabolically synthesize more amino acids, the simple molecules that are the building blocks for more complex protein molecules. The process of converting amino acids into proteins takes longer than the process of photosynthesis, and it depends on having a complementary supply of micronutrients, usually not provided by synthetic fertilizers. If sufficient necessary micronutrients are available, the plant can synthesize the enzymes needed for the process of synthesizing proteins can proceed effectively.
Plants that take up a lot of inorganic N, the theory states plausibly, will thus have an excess of amino acids in their sap which flows through their stems and other organs and in the cytoplasm that is within their cells. Such plants become a feast for insect pests and attract them. This has often been observed and commented on by agriculturalists who see the almost-magnetic effect of lush growth of inorganically-fertilized plants in general, not only rice. The insects that are attracted are often also vectors for disease.
Similarly and often concurrently, when farmers apply chemical pesticides, herbicides, etc. for the purpose of crop protection, they can get opposite results because these synthetic chemicals once within plants have an adverse effect on the plants’ metabolism. The plants continue producing simple sugars through photosynthesis, but metabolically they are not able to convert all of these sugars into the more complex carbohydrate molecules known as polysaccharides, long chains of monosaccharides that include starches for energy storage and cellulose and chitin for the construction of plant cell walls and of plants’ tissues and organs.
Plants that have an abundance of simple sugars in their sap and cytoplasm are attractive to and supportive of insect pests and disease vectors, according to Chaboussou, who cited a wealth of published literature to support this theory in his little-known book, Healthy Crops.[31]
The IPM program of the UN Food and Agriculture Organization has a well-known mantra: The best way to protect crops against pests and diseases is to grow healthy plants. This sounds like an oxymoron, but such a strategy strengthens and mobilizes plants’ natural defenses against pests and pathogens. These defenses are conversely weakened by the use of synthetic chemical protectants that disrupt or impede metabolic processes.
A statistic that supports Chaboussou’s theory is the observation that in the half-century after World War II, when chemical pesticide use in the United States increased by 14-fold, the percent of crop losses from pest damage rose from 7% to 13%, almost doubling rather than declining.[32] The management of crops with SRI or SCI methods (Chapter 14) helps farmers to get off the agrochemical treadmill.
Much more research is needed to understand the relationships between SRI practices and rice plants’ greater resistance to pest and disease losses, but this effect is widely reported and will become increasingly important as farmers around the world have to cope with climate change.
COLD-TEMPERATURE TOLERANCE
Short periods when ambient temperatures become unseasonably low for a few days or weeks may or may not be associated with global warming, but in any case they are one of the adverse conditions that farmers must contend with as our climate changes. Global warming creates more irregularity in weather patterns, so that higher temperatures in some regions get counterbalanced by colder temperature elsewhere.
There will of course be some limitation on how long even cold-tolerant crops can withstand the harmful effects of cold spells. But rice crops’ toleration of cold snaps is an advantage worth keeping in mind. Quite by chance, there are some experimental data that show SRI management helping to buffer rice crop yield against low temperatures.
At the 2nd all-India SRI symposium held in Agartala in 2007, researchers from the state agricultural university in Andhra Pradesh reported on their results from an IPM study of SRI that they had conducted in the previous monsoon season. They were testing to see what pest and disease resistance, if any, SRI management might elicit.[33]
Their trials plots in Hyderabad were hit by a short but severe cold period, with night-time air temperatures dropping below 10⁰C for 5 successive days, as seen in the table below. This chill caused the plots under standard rice crop management to produce little grain that season, while the adjacent SRI plots gave a yield over 4 tonnes per hectare.
This temperature drop was sudden and steep, and no other data have been collected on SRI resistance to cold-temperature stress, so we have only this one set of data from India to consider so far. However, these results are consistent with the generally more robust performance of SRI-grown plants.
High temperatures can also be a constraint, possibly debilitating, for rice crops. The effect of heat is felt mostly through water stress as high temperatures accelerate the evaporation of water from the soil and its transpiration into the atmosphere from the leaves. Since heat also causes wider opening of the plants’ stomata (tiny leaf openings), this will also contribute to plants’ loss of and greater need for water.
The growth and functioning of larger, longer-lived root systems (Chapter 4) contributes to drought-resistance and greater water productivity, as reviewed above in this chapter. This should enable rice plants to cope better with high temperatures. While such temperatures can be incapacitating for rice plants, like abnormally cold temperatures, they should be less damaging for SRI plants than for plants grown from more mature seedlings, with higher plant density and flooded soils that do not have enhanced organic matter. SRI practices by making root systems grow more deeply and by by making soil systems function better will give rice plants more resilience to abnormal temperatures.
LOWER GREENHOUSE GAS EMISSIONS FROM RICE PADDIES
The first evaluation of how SRI crop management can affect the emission of greenhouse gases (GHGs) from paddy fields was done in Indonesia by a Japanese researcher, Dorothy Kimura, working with SRI colleagues at Indonesia, as noted in Chapter 9. This was not only an important consideration, but it appeared to be a ‘bonus’ for SRI, and added benefit that had not been considered before. However, we proceeded cautiously, not making public claims on this effect, because it is a complicated and contentious subject.
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Measurements of GHGs are quite volatile, very changeable: Because emissions are largely driven by microbiological dynamics, they are affected by soil temperature, humidity and pH (acidity), and the composition and size of microbial communities, among other things. Instrument readings of emission levels vary considerably over days, weeks, months, and seasons.[34] GHG emission data need to be gathered and analyzed very systematically, and the results will be affected by both sampling and timing.
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The is an inverse relationship between methane (CH₄) and nitrous oxide (N₂O): Since methane is generated by anaerobic bacteria (methanogens) while nitrous oxide is a result of nitrification and denitrification processes that are mostly aerobic, these two GHGs are usually inversely related. Having less of one means that there will generally be more of the other, and vice versa.
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Nitrous oxide has much greater global warming potential (GWP) than methane, 10 to 12x more: Although CO₂ is the most significant GHG, constituting about 82% of GWP, it is not the most potent gas. By weight, methane has about 25x more GWP than does carbon dioxide, while nitrous oxide has about 300x more. Thus, even small increases in N₂O emissions can offset and wipe out the lowering of GWP from reductions in CH₄ emissions.
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We knew that any results were likely to be controversial, not only because of the above considerations, but because if carbon credits are claimed for SRI producers and can then be bought and sold, large amounts of money will become involved, and this will surely arouse contention. SRI already had enough controversy associated with it, so stirring up more disputation seemed inadvisable.
However, after the first report by Kimura and Iswandi Anas in 2008, a number of studies over the next decade showed that reductions in methane emissions were not cancelled out by increases in nitrous oxide. [35] These findings put the claim of GHG reduction through SRI crop management on firmer ground.
One of the best evaluations was done in the Mekong Delta of Vietnam under a project supported by the German agency GIZ (formerly GTZ).[36] This study documented with some 250 on-farm trials a substantial and statistically-significant decrease in methane emissions from SRI paddy fields, by 20% compared to adjacent fields cultivated with standard practices. Below are the data reported from the GTZ study, as well as a picture of technicians taking GHG measurements from SRI and control plots.
In some ways, the most interesting result from these trials in Vietnam, although not statistically significant, was the finding that the nitrous oxide emissions in these trials were slightly decreased with SRI, by 1.5%; soil scientists would have predicted an increase. This pointed out that N₂O emission is not a consequence only of soil conditions. Changing rice cultivation from flooded to unflooded soils need not lead to an increase in N₂O accompanying the reduction in CH₄.
N₂O emissions are driven also by having an abundance of inorganic nitrogen in the soil from which methanogenic microorganisms can produce N₂O as an undesired consequence. When SRI makes it no longer necessary for farmers to apply large amounts of inorganic N fertilizer to their rice paddies, the synthesis and emission of N₂O is no longer propelled by an excess supply of nitrogen in the soil as substrate for microbes to produce this potent greenhouse gas. That N₂O emissions need not increase significantly under SRI management was an important finding.
Trials studying this dynamic in Korea at Kangwon National University found larger reductions in methane emissions than seen in Vietnam, as well as some increase in nitrous oxide, which was expected. But the net effect was a 72% reduction in the global warming potential of the greenhouse gases emitted from SRI plots (CH₄ + N₂O) when these emissions were measured and compared in CO₂ equivalence with emissions from nearby rice plots under conventional management.[37] While there was a relatively greater increase in nitrous oxide, in absolute terms there was little effect.
Calculations of the SRI impact on global warming potential (GWP) based on research conducted at the Indian Agricultural Research Institute have also showed SRI methods reducing net greenhouse gas emissions by less than was reported from the Korean study, i.e., by 38% and 28%, respectively.[38] But an analysis done in Nepal, on the other hand, found large reductions in CH₄ under SRI management accompanied by a reduction almost as large in N₂O emissions, which was unexpected and unprecedented.[39]
A study in India of SRI effects on greenhouse gas emissions as well as other aspects of SRI use was done in Andhra Pradesh state by researchers from Oxford University and the National Institute of Rural Development in Hyderabad. They utilized what is called a ‘life-cycle assessment’ which tries to encompass all GHG emissions from all stages of production, from planting to consumption. There was also value-chain analysis so that transportation, manufacturing and other related activities were considered. Estimates were made also for the amounts of carbon dioxide (CO₂) generated during the total production process, with all of the GHGs converted into CO₂ equivalence.
The performance of 20 representative SRI farmers and 10 control (non-SRI) farmers was studied in detail to ascertain agronomic, economic, energy, labor and other relationships, constructing a comprehensive model of the whole production system, as reported in two published articles.[40]
Along with a 60% average increase in grain yield, the data showed reductions of 60% in groundwater use and of 74% in fossil fuel consumption. Net greenhouse gas emissions, denominated in CO₂ equivalence, were calculated to be reduced by 40% on an area basis. With SRI’s higher yield, the net GHG emissions per kg of paddy rice produced with SRI methods reduced by 77%.[41]
The benefits from SRI for lowering greenhouse gas emissions have been most systematically studied by a number of government researchers in Vietnam, where SRI has been made part of the government’s strategy to reduce the contributions of its agricultural sector to global warming.[42]
How much SRI can contribute to this reduction will vary according to many factors of climate, soil, etc. From what is now known, it appears that the utilization of SRI ideas and methods can reduce greenhouse gas emissions by at least 20-30% on an area basis – and irrigated rice production is one of the most widespread forms of agriculture as well as the biggest consumer of freshwater. In terms of food supply, because SRI also raises yields, it can reduce the amount of CO₂ emitted per kg of rice produced by 40-50% or more.
In 2017, an international initiative, Project Drawdown, undertook to identify and assess the most substantial presently-existing solutions to counter climate change, means available and proven.[43] The analysis included SRI as one of the 100 most effective means to reduce greenhouse gases in the atmosphere. In particular, SRI was appreciated because there is little or no additional cost required for implementing it. SRI offers farmers substantial economic reward as an incentive to adopt its climate-friendly agricultural practices.
The Project Drawdown staff calculated that expanding SRI use to 133 million hectares by 2050, considered a reasonable projection, would sequester carbon and reduce methane emissions equivalent to 3.1 gigatons of CO₂, at the same time that this would increase farmers’ incomes by at least US$ 678 billion.
The mitigation of climate change is a bonus on top of the benefits of increased food production and making food production more secure and sustainable, countering the stresses of drought, storm damage, pests and disease, and temperature extremes that are becoming more constraining. These advantages do not mean that the benefits will be necessarily or quickly realized. Reaching the spread of SRI that Project Drawdown analysts were willing to assume will be a major challenge. But it seems an achievable target, and this pertains only to the irrigated production of rice.
As mentioned already and as will be discussed in the next two chapters, SRI ideas and methods have over the past dozen years been adapted to and used with rainfed rice production and then a range of other crops. We would not expect that greenhouse gas emissions from unirrigated crops can be reduced by SCI practices as much as by the SRI management of paddy rice. However, there can be a significant reduction. A study done with hundreds of measurements in Cambodia, Laos, Thailand and Vietnam calculated that using SRI practices for unirrigated rice production in these countries reduced GHG emissions per hectare by 17%.[44]
In the overall effort to abate global warming and climate change, such reductions are worth pursuing since they will also bring farmers more production and more income. And consumers will have more supply of rice that is grown with less water and with less use of agrochemicals, which is good for them as well as for the environment. Growing other crops beyond rice with SCI methods, making these crops more resilient when subjected to the stresses of climate change, will also be important for helping to meet people’s food security and other needs in the decades ahead.
NOTES AND REFERENCES
[1] C. Deutsch, J.J. Tewksbury, N. Tigchelaar, D.S. Battisti, S.C. Merrill and B.H. Raymond, ‘Increasing crop losses to insect pests in a warming climate,’ Science 361: 916-919 (2018).
[2] The concept and objectives of ‘climate-smart agriculture’ were proposed by the UN Food and Agriculture Organization (FAO) in a straightforward way in its paper for a 2010 international conference in The Hague: ‘Climate-Smart’ Agriculture: Policies, Practices and Financing for Food Security, Adaptation and Mitigation, UN Food and Agriculture Organization, Rome (2010).
However, as various commercial interests became prominent endorsers and promoters of climate-smart agriculture, some objections were raised that they were seeking to coopt the concept and adjust it in ways that will perpetuate farmers’ dependence on purchased inputs, endorsing genetic modification and other biotechnology. See, for example, What’s Wrong with ‘Climate-Smart Agriculture’? (2015) from the Institute for Agriculture and Trade Policy. A perspective on these matters that represents the thinking of much of the SRI community has been articulated by Gina Castillo, ‘What’s the danger in climate-smart agriculture?’ Oxfam blog, Oct. 26, 2015.
[3] This is the formulation of CSA presented in the FAO paper (2010) cited in the preceding endnote.
[4] E. Styger and N. Uphoff, The System of Rice Intensification (SRI): Revisiting Agronomy for a Changing Climate, Practice Brief for Climate-Smart Agriculture, Global Coalition for Climate-Smart Agriculture, FAO and CGIAR, Rome (2016), and A.K. Thakur and N. Uphoff, ‘How the System of Rice Intensification contributes to climate-smart agriculture,’ Agronomy Journal, 109: 1163-1182 (2017).
[5] P. Jagannath, H. Pullabhotla and N. Uphoff, ‘Meta-analysis evaluating water use, water saving, and water productivity in irrigated production of rice with SRI vs. standard management methods,’ Taiwan Water Conservancy, 61: 14-49 (2013).
[6] N. Uphoff, ‘SRI: An agroecological strategy to meet multiple objectives with reduced reliance on inputs,’ Agroecology and Sustainable Food Systems, 41: 825-854 (2018).
[7] For a review of experience in India with SCI crops having resistance to adverse climate effects, with some data, see S. Ravandale, V. Niranjan and D. Sen, ‘Building climate resilience,’ LEISA-India, 22: 47-50.
[8] The pests considered here are invertebrates, insects, nematodes, etc. We have only anecdotal evidence that SRI management also limits vertebrate pests, in particular, rats. We take seriously the report by L. Narayana Reddy in Karnataka state, one of the leaders of organic agriculture in India, who described in a 2020 video his experience of seeing rat populations and their damage reduced in his SRI fields. This has been reported also by Premarathne in Sri Lanka (personal communication). Both Reddy and Prema attribute this effect to SRI’s wider spacing between plants, which makes rats feel less secure.
[9] J.G. Zheng, Z.Z. Chi, X.Y. Li and X.L. Jiang, ‘Agricultural water saving possible through SRI for water management in Sichuan, China,’ Taiwan Water Conservancy, 61: 50-62 (2013).
[10] Asterisked comparisons for SRI yield and profitability are with the average for Sichuan province.
[11] R. Namara, D. Bossio, P. Weligamage and I. Herath, ‘The practice and effects of the System of Rice Intensification (SRI) in Sri Lanka,’ Quarterly Journal of International Agriculture, 41: 5-23 (2008).
[12] See Drought Study Findings posted on the internet by Livolink Foundation in 2012. For this study, 241 farmers from the 7 states were selected randomly from among SRI farmers and farmers in the same community using their usual methods. Straw yield with SRI was also 43% higher. Pest incidence was 38% in SRI plots compared to 45% on farmers’ usual plots.
[13] See references in endnote 4 above.
[14] In almost all cases, the data were from on-station trials where precise measurements under controlled circumstances were possible. As noted below, measured yield increases with SRI methods were only 11%, 5.9 tonnes per hectare vs. 5.1 tonnes with researchers’ methods, but the use of SRI methods was incomplete and often less rigorous than recommended. Only 30% of the comparison trials used 80% or more of the recommended practices. So, there is reason to believe that if SRI methods had been used and evaluated more fully, according to our expectations, the yield increase would have been even greater, which would have made the water productivity even greater.
[15] Note that the average total water productivity in the meta-analysis data base for conventional paddy management -- 0.39 grams per liter of water -- is almost identical to the figure of 0.4 grams per liter that was calculated and reported by B. Bouman, R. Lampayan and T. Tuong, Water Management in Irrigated Rice: Coping with Water Scarcity, International Rice Research Institute, Los Baños, Philippines (2007).
[16] This manager’s SRI yield of 16 tonnes per hectare was reported by Prof. Yuan Longping at the Sanya conference (Chapter 8), and it was Liu who had devised the ‘triangular’ method of transplanting three SRI seedlings, 7-10 cm apart, in hills that were 30x45 cm apart; this preserved the SRI principle of wider spacing with 50% greater plant density, for higher yield. My visit to Liu Zhibin’s farm in 2004 was very memorable.
[17] This was in Okara district where the Punjab Department of Agriculture had a joint evaluation project with IRRI. The Department’s director-general for water management, Mushtaq Gil, who took me to see these fields and meet farmers, had visited Sri Lanka a year before, and there he learned about SRI methods from SRI colleagues to whom we had introduced him. He started SRI trials as soon as he returned to Lahore.
[18] This was our first picture showing this effect of lodging-resistance. The lodged plot in the foreground was grown with standard methods, while SRI practices had been used on the upright plot behind it.
[19] This picture was taken and sent by Elske van de Fliert, at the time with FAO’s IPM program in Hanoi. I met this farmer and some of her colleagues the following January during a visit to their village, Dông Trù (report, pp. 2-7).
[20] See reference in endnote 33 below.
[21] The pictures below were sent by Bancy Mati of Jomo Kenyatta University of Agriculture and Technology in November 2011 in an email with this Subject line: Natural calamity proves a plus for SRI in Mwea. “Dear Colleagues,” she wrote. “Last week, there was a freak storm in Mwea where some of our farmers have adopted SRI. The conventional planted rice fell all over the place (lodging) while SRI remained intact (see photos). Now you can tell which farmers were wise to adopt SRI by simply looking at the fields. The lodged rice may rot since it is lying on wet paddies. One more reason to promote SRI and to be heard. All the best, Bancy”
[22] This research was done by Tejendra Chapagain from Nepal under supervision of Prof. Eiji Yamaji at the University of Tokyo. T. Chapagain and E. Yamaji, ‘The effects of irrigation method, age of seedling and spacing on crop performance productivity and water-wise rice production in Japan,’ Paddy and Water Environment, 8:81-90 (2010), and T. Chapagain, A. Riseman, and E. Yamaji, ‘Assessment of System of Rice Intensification (SRI) and conventional practices under organic and inorganic management in Japan,’ Rice Science, 18: 311-320 (2011).
[23] A.K. Thakur, S. Rath and A. Kumar, ‘Performance evaluation of rice varieties under system of rice intensification (SRI) compared with conventional transplanting system,’ Archives of Agronomy and Soil Science, 57: 223-238 (2011).
[24] The Iranian results, shown first, came from research done completely independently of the international SRI community, so they were a windfall. The ‘improved’ management system was intermediate between SRI and conventional rice management, with SRI seedling age, water management, nutrient management, and weeding, but with 2x more plant density than with SRI (this was still half the plant density of the recommended practices). S. Dastan, G. Noormohamadi, H. Madani, H.R. Mobasser and M.S. Daliri, ‘Evaluation related to lodging characteristics and grain yield in Iranian rice genotypes under modified agronomic systems,’ Annals of Biological Research, 4: 267-275 (2013).
[25] From W. Wu, J.L. Huang, F. Shah, and N. Uphoff, ‘Evaluation of System of Rice Intensification Methods applied in the double rice-cropping system in central China,’ article published on-line in Advances in Agronomy, Vol. 132 (2015) after going through the journal’s regular peer-review process. Unfortunately, the article was withdrawn at the request of Huang because of what he said were “some misleading viewpoints that are not able to be resolved” (discussed in Chapter 28).
Huang made no effort to explain to his co-authors what these “misleading viewpoints” were, or to resolve any differences in “viewpoint.” This was rather strange and irregular. No question was raised about the validity of the data reported in the article, so they are cited here as transiently published. The lead author (Wu) who had conducted the research over four seasons had asked me to help write up the results in good English for international publication. The zero-N fertilizer treatment results are averages for the two varieties for the 2009 early season and 2009 late season; the with-fertilizer treatment results are averages for three seasons: 2008 late, 2009 early, and 2009 late.
[26] See report made by the Plant Protection Department to the Ministry in October 2007.
[27] The measured reduction in sheath blight matched the report of Dr. Zhu Defeng in China during a field visit to Bu Tou village in Tien Tai township in 2004. He said that farmers were reporting a 70% reduction in sheath blight on their SRI crops. In Chapter 1, readers saw a picture of SRI rice plants’ resistance to the brown planthopper in Indonesia.
Recent research in Malaysia has documented a significant reduction in sheath blight susceptibility for SRI plants, which is further reduced when SRI management is combined with inoculation of SRI seedlings with the beneficial fungus Trichoderma. F. Doni, C. Zain, A. Isahak, F. Fathurrahman, A. Anhar, W. Yusoff and N. Uphoff, ‘Synergistic effects of System of Rice Intensification (SRI) management and Trichoderma asperellum SL2 increase the resistance of rice plants (Oryza sativa L.) against sheath blight (Rhizoctonia solani) infection,’ manuscript under review.
[28] These data are from K. Ezhil Rani, Relative abundance of insects in SRI and conventional rice. M.Sc. thesis, Tamil Nadu Agricultural University, Coimbatore, TN, India (2004), as reported in N. Uphoff, ‘Developments in the System of Rice Intensification,’ in T. Sasaki, ed., Achieving Sustainable Cultivation of Rice, Vol. 2, 183-211, Burleigh-Dodds, Cambridge, UK (2017). Similar results were reported from research conducted at ANGRAU in Andhra Pradesh state during 2005-06.
[29] For example, K. Karthikeyan, S. Jacob and S.M. Purushotaman, ‘Incidence of insect pests and natural enemies under SRI method of cultivation,’ Oryza, 47: 154 –157 (2010), and V. Visalakshmi, P. Rama Mohana Rao and N. Hari Satyanarayana, “Impact of paddy cultivation systems on insect pest incidence,” Journal of Crop and Weed, 10: 139-142 (2014).
In a study for the EU-funded SRI-Lower Mekong Delta project, it was found that less disease was reported in farmers’ SRI plots when neck blast struck in Kampong Speu province of Cambodia in 2015 and when rice blast was experienced in Vietnam two years later. In conventionally-managed plots the average incidence reported by farmers was 77%, while in neighboring SRI fields, it was 30-35%. Understanding the Pattern of Change among Different Groups of Farmers due to System of Rice Intensification (SRI) Intervention: Results from the Monitoring, Evaluation and Learning Study, ACISAI, AIT, Bangkok, 2018.
Thesis research in Haiti in 2019-20, by Erdjani Joseph for her degree from the Université Quisqueya, evaluating disease resistance with four rice varieties showed SRI rice plants of all varieties being more resistant to blast, helminthosporiosis, and panicle leaf sheath rot, with incidence reduced incidence by half to three-quarters.
[30] The study cited at the end of endnote 26 above has charted out an interesting line of inquiry that focuses on beneficial symbiotic microbial endophytes, in this case Trichoderma. But this is only demonstrating a correlation, not explaining the path(s) of causation.
[31] Healthy Crops: A New Agricultural Revolution (Jon Anderson, Charnley, UK, 2004). Unfortunately for the world, Chaboussou died in 1985, shortly after he published this book in French. When I first learned about this theory from Andres Gonçalves, a Brazilian Fulbright student who came to Cornell in 2000, the theory seemed too radical even for me. But once the book was translated into English and published in 2004, I could read it for myself. I understood then how and why this single theory could encompass insect, bacterial, fungal and even viral infestation or infection.
Wanting to have a more expert opinion, I sent the book to Prof. Michael Hoffman, an entomologist who was director of Cornell’s IPM program at the time, asking him if he could find any scientific flaws in the argument. A week later, he gave the book a ‘thumbs-up’ and asked if he could keep the copy I had sent. A sympathetic summation of Chaboussou’s thinking is offered by John Paul, ‘Trophobiosis theory: A pest starves on a healthy plant,’ Elementals: Journal of Bio-Dynamics-Tasmania,’ 88: 24-28 (2007).
[32] David Pimentel, Techniques for Reducing Pesticides: Environmental and Economic Benefits, John Wiley, Chichester, UK (1997).
[33] See presentation by T. Ratna Sudhakar and P. Narasimha Reddy, ‘Influence of system of rice intensification (SRI) on the incidence of insect pests,’ 2nd National SRI Symposium, Agartala, India, October 3-5, 2007, slides 16 and 17.
[34] This is discussed by Indonesian and Japanese colleagues whose detailed measurements and sophisticated modeling confirmed CH4 and N2O emissions vary even within short periods, and not always inversely, since they are affected by differences in soil pH, moisture, and temperature as well as different regimes of water management. B.I. Setiawan, A. Irmansyah, C. Arif, T. Watanabe, M. Mizoguchi and H. Kato, ‘Effects of groundwater level on CH4 and N2O emissions under SRI paddy management in Indonesia,’ Taiwan Water Conservancy, 61: 135-146 (2013).
[35] Iswandi Anas, D.K. Kalsim, B.I. Setiawan, Yanuar and S. Herodian, ‘Some Highlights of SRI Research in Indonesia,’ and Dorothy Kimura, ‘Methane and Nitrous Oxide Emissions from Paddy Rice Fields in Indonesia,’ presentations to Ministry of Agriculture workshop, Jakarta, June 12, 2008.
[36] J. Dill, G. Deichert and Le T.N.T., eds., Promoting the System of Rice Intensification: Lessons Learned from Trà Vinh Province, Vietnam. GIZ and IFAD, Hanoi (2013). The economic analysis performed showed SRI methods increasing farmers’ net income from rice production by 155% per hectare.
[37] J.D. Choi, G.Y. Kim, W.J. Park, M.H. Shin, Y.H. Choi, S. Lee, S.J. Kim and D.K. Yun. ‘Effect of SRI water management on water quality and greenhouse gas emissions in Korea,’ Irrigation and Drainage, 63: 263-270 (2014).
[38] The studies, both done at the Indian Agricultural Research Institute in New Delhi, were, respectively, P. Suryavanshi, Y.V. Singh, R. Prasanna, A. Bhatia and Y.S. Shivay, ‘Pattern of methane emission and water productivity under different methods of rice crop establishment,’ Paddy and Water Environment, 11: 321-332 (2012); and N. Jain, R. Dubey, D.S. Dubey, J. Singh, M. Khanna, H. Pathak and A. Bhatia, ‘Mitigation of greenhouse gas emissions with system of rice intensification in the Indo-Gangetic plains,’ Paddy and Water Environment, 12: 355-363 (2014).
[39] This field study in Morang district of Nepal, measured 4-fold reduction in CH4 and an even greater, 5-fold reduction in N2O. Sudeep Karki, System of Rice Intensification: An Analysis of Adoption and Potential Environmental Benefits, Norwegian University of Life Sciences, Ås, Norway (2010).
The first reduction was consistent with the results reported from other studies, but the second reduction was hard for Sudeep’s thesis advisors to accept. They approved the thesis because the measurements had been properly done and reported, but they did not encourage publication of the thesis results because they considered it so unlikely that N2O would be reduced under aerobic soil conditions, and by so much. This thesis is available for inspection, however. Karki reported a 48% reduction in fertilizer use with a 99% reduction in expenditures on agrochemicals, and a 118% increase in yield.
[40] Alfred Gathorne-Hardy, with D. Narasimha Reddy, M. Venkatanarayana and Barbara Harriss-White, ‘A Life Cycle Assessment (LCA) of greenhouse gas emissions from SRI and flooded rice production in SE India,’ Taiwan Water Conservancy 61: 110-125 (2013); and Alfred Gathorne-Hardy, D. Narasimha Reddy, M. Venkatanarayana and Barbara Harriss-White, ‘System of Rice Intensification provides environmental and economic gains but at the expense of social sustainability: A multidisciplinary analysis in India,’ Agricultural Systems 143: 159-168 (2016).
[41] Along with a 30% reduction in N fertilizer applications, there was a doubling of nitrogen use efficiency by the crop, going from 16% to 33%. The only negative finding from this evaluation was that because labor requirements were reduced, wage payments to agricultural laborers, mostly women, were reduced by 50%. This was a boon to land-owning households, but a loss for the households of agricultural laborers. The authors proposed that the latter could and should be compensated through private or public payments so that the multiple benefits of SRI would be not be blocked but rather more equitably shared.
[42] Decision: On approving programme of Green House Gas (GHG) emissions reduction in the Agriculture and Rural Development sector up to 2020, 3119/QD-BNN-KHCN, Ministry of Agriculture and Rural Development, Hanoi, 16 December 2011.
[43] Paul Hawken, ed., Drawdown: The Most Comprehensive Plan Ever Proposed to Reverse Global Warming, Penguin Books, New York, pp. 48-49 (2017).
[44] Workshop Report on Sustaining and Enhancing the Momentum for Innovation and Learning for the System of Rice Intensification (SRI) in the Lower Mekong River Basin, Nov. 1-2, ACISAI, Bangkok (2018).
PICTURE CREDITS: Norman Uphoff (Cornell); T.M. Thiyagarajan (TNAU); Elske van de Fliert (FAO); GIZ/IFAD publication; Y.C. Chang (Taiwan); Gabriel Garces (FEDEARROZ/Colombia); GIZ/IFAD publication.