From soil scientist to agronomist to agricultural systems researcher and SRI supporter
Willem A. Stoop
These memories were initially written down in Dutch at the request of the Dutch Soil Science Association when celebrating its 75th jubilee in 2009. They were translated and updated twice: in 2012 for the Indian PhD candidates mentioned below to provide them some insight on my background and to explain my motivations for taking an interest in their respective PhD projects; and again in 2018 at the request of Norman Uphoff for this book project.
The early years (1948- 1969)
Just after the end of the Second World War, my parents sent me – I was four years old at that time – to a farm in the Haarlemmermeer polder (near Nieuw Vennep, south of Amsterdam) to recover from the Dutch ‘hunger winter.’ We were living in an upstairs apartment in The Hague at that time; my father was a lawyer, my mother a historian. So spending time on this farm, not only as a four-year-old but then also during every summer holiday during my primary school years, had a tremendous influence on the rest of my life.
As an 8-year-old, I thus was determined to become a ‘farmer.’ I stuck with this idea until I found out, at the time I was in high school, that it was also possible to go to Wageningen University to get an agricultural degree first. I graduated from high school at the age of 17 and started in Wageningen in September 1960. Without hesitation I picked Soil Science from the list of more than twenty different majors and have never regretted it. The extensive lab and field courses instilled a very critical attitude towards the accuracy of many results from laboratory analyses or field experiments.
It was during my internship in Hawaii (1966/7) that I developed a real passion for my discipline. It was there and then that I first felt the ‘spark’ that according to Professor Edelman was to “jump at some point during one’s studies.” In many respects this internship has been crucial for the rest of my professional life.
I was fortunate to obtain a graduate assistantship at the College of Tropical Agriculture of the University of Hawaii with the – then very young – soil scientist Dr. Les Swindale from New Zealand as my supervisor . Swindale started me on a soil genesis laboratory study of four soils from a catena (a toposequence) on the island of Maui. The focus was on clay mineralogy, a subject not extensively covered by Wageningen. After completing this lab project there was still enough time left for some field work – to map the soils of the experiment station on the beautiful island of Kauai and to participate in a reconnaissance soil survey on the Big Island.
Upon returning to Wageningen, I decided to add colloid chemistry as a third minor to my study program, which already included soil fertility and horticultural science as minors, with regional soil science as the major. This program, I hoped, would provide future opportunities for a fundamental-research-oriented career combined with a field-oriented agronomic one. As it turned out, I have been able to exploit both opportunities.
From rubber agronomy to international Farming Systems Research (1969-1997)
Early 1969, a few weeks before graduation, I found a job through an advert in Nature as agronomist with the Firestone Rubber Plantations in Liberia (West Africa), to work on soil fertility/fertiliser requirements of rubber and weed control. It was a great first job (in spite of my Wageningen mentor considering it a “dead-end” start)! Imagine a rubber plantation of 460 km2 where you could set up any field trial of any size and design, and a brand new laboratory (designed by myself) for plant leaf analyses, to support field measurements and observations. This work taught me some important lessons: the dangers of uncritically transferring research results from one location in the world (rubber in Malaysia) to another like Liberia, and second, the harm inflicted by using chemical fertilisers unprofessionally that was causing decreases in latex yield and increases in damages (uprooting of trees) by tropical storms.
After two years in Liberia, the not so attractive prospect of a career as rubber expert made me apply for a Ph.D. study, again at the University of Hawaii. A doctoral degree, I figured, would open the doors to an international research career. In January 1972, I started my dissertation research in tropical soil fertility under the supervision of Dr. Robert L. Fox.
The research focused on the soil chemical properties of various Hawaiian red (volcanic) soils, and the effect of high phosphate applications for plant nutrition. My minor in colloid chemistry at Wageningen proved a strategic choice after all. Many tropical soils tend to be made up of mainly of iron and aluminium oxides as colloids that greatly affect how these soils respond to to various types of fertilizers, phosphate in particular. In July 1974, I completed my dissertation and graduated, and in subsequent years published three articles from the thesis in the peer-reviewed journal Geoderma.
As I had hoped for, my Ph.D. degree opened up various interesting international opportunities. In November 1974, my family and I moved to Mexico where I had landed a two-year postdoctoral position within the maize program of the Centro Internacional de Mejoramiento de Maíz y Trigo (CIMMYT). The CIMMYT institute was an exciting place to be. Together with IRRI, the International Rice Research Institute in the Philippines, it was known for its contribution to the Green Revolution in Asia. It was home to passionate researchers, including the Nobel Prize winner Norman Borlaug as director of the wheat program.
The institute had a constant stream of eminent visitors and activities in which all postdocs were expected to fully participate. Among other tasks I was put in charge of the maize agronomy training program and was sent on a three-week monitoring tour of the national maize programs of East Africa (Tanzania, Zambia, Malawi and Kenya). In early 1976, I was sent on a similar tour of six weeks to South and Southeast Asia, starting in Pakistan, then on to India, Nepal, Thailand, Indonesia, and the Philippines.
The deeper intention behind this last trip – as far as CIMMYT was concerned – was to entice me into accepting a position as regional maize agronomist for South and Southeast Asia, to be based at ICRISAT (International Crops Research Institute for the semi-arid Tropics) in Hyderabad, India. They failed to convince me -- I didn’t want to become a kind of sales representative for maize seeds, with no time left for agronomic field research.
Refusing this position left me in limbo until in mid-1976, Dr. Claude Charreau, regional ICRISAT representative for West Africa, on a visit to CIMMYT, suggested a position as cropping systems agronomist within the new ICRISAT outreach team stationed at the Kamboinsé experiment station near Ouagadougou, the capital of Upper Volta, now Burkina Faso.
In Janaury 1977 I started a two months “re-indoctrination” period at ICRISAT headquarters in India to familiarise myself with a more research-oriented approach than followed at CIMMYT and with the new colleagues and their activities. After all, I had no experience whatsoever with agriculture in the semi-arid tropics, nor with their major crops (sorghum, millet, peanut, cowpea, etc.) and the land and water management strategies applicable in these dry regions.
Then in April 1977, I took up my new post as agronomist in a blistering hot Upper Volta. Just prior to leaving India Les Swindale, who had just taken over Ralph Cummings as DG of ICRISAT, had given me the following (interesting) instructions: to set up an agronomic research program on the agricultural problems and opportunities of Upper Volta and the Sahel region, but by all means NOT to get involved in agricultural extension or collaborative projects with farmers. It was a license to set up my own research program, at my own discretion (see footnote 4)!
The Upper Volta team consisted of sorghum and millet breeders, a plant disease expert, and a Dutch associate expert/agronomist whose job was to restore and develop the dilapidated Kamboinsé experiment station. A year later, our team was joined by an energetic young Nigerian entomologist, Kanayo Nwanze. During the ‘boom’ of US aid to Africa in 1980, we were joined also by three Americans (two economists and a land and water management specialist) and a Canadian anthropologist.
During my first season in Upper Volta I recognised – somewhat by accident -- a crucial feature of the local agriculture: the adaptation of crops (and crop combinations) to the topography and soils within the landscape. Obviously, water was the driving factor: the lowest areas were flooded during the rainy season; the transition zones had good soil moisture most of the time; whereas the uplands were relatively dry and required soil and water conservation measures.
The wet lowlands were suitable for rice, the moist transition zones for sorghum and corn, and the drier upland soils for millet, cowpea and peanut, i.e., crops that are drought-tolerant yet sensitive to flooding. Local farmers applied these principles in ingenious ways: exploiting the relatively short rainy season (3 to 4 months) with its unpredictable drought periods by growing mixtures of crops (known as ‘intercropping’: corn with rice, or corn with sorghum or millet; or often one of these cereals with cowpea as a ground cover crop). Hence, ‘crop adaptation to toposequence land types’ and ‘intercropping systems’ became major research themes with the objective to help farmers to reduce / spread the risks of crop failure.
It was during the third season in Upper Volta (1979) that we were contacted by a village leader who was determined to find help for his famine-stricken home village of Nakomtenga on the Mossi plateau. He was hoping that ICRISAT’s agricultural innovations could help his village. Against Swindale’s original instructions we decided to pick up the challenge and set up an experiment program together with the farmers. Only later did I realize that our program was a precursor to the Farming Systems Research (FSR) approach that became a major development thrust in the 1980s. What evolved was a participatory approach in which farmers play a central role. This marked a fundamental turnaround from the top-down approaches which often tend to be guided primarily by academic insights.
In the early-1980s, when my children had reached high school age, I returned with my family to the Netherlands and obtained a position as tropical cereals specialist with the Royal Tropical Institute (KIT) in Amsterdam. ICRISAT and KIT had agreed that I would remain a consultant in the ICRISAT agronomy program in Burkina Faso, and in addition support various Dutch development projects in Mali and Ghana. One of these projects was the Mali Sud Sikasso project sur la recherche des systèmes de production (research program on farming systems).
During this period, the ICRISAT anthropologist and the KIT sociologist made me increasingly aware of the social and human dimensions of the local agricultural systems. In return, I was able to point out to them the various ingenious biological-technical features of the local practices. The KIT-ICRISAT arrangement has been very important as it permitted me to extend various field studies for three more years, thereby providing the data for several articles in peer-reviewed journals (Field Crops Research; Agriculture, Ecosystems and Environment).
Unfortunately, KIT entered a period of crisis, being forced by its funders (mainly the Ministry) towards a more commercial strategy which ended the ICRISAT collaboration. At about that time in 1982, a new international institute was founded in The Hague: ISNAR, the International Service for National Agricultural Research, which was part of the Consultative Group for International Agricultural Research (CGIAR). This latter is the network organization of international agricultural research centers that also included CIMMYT, IRRI and ICRISAT.
ISNAR was to strengthen agricultural research policy, organization and management within the national programs of developing countries. This was deemed necessary because the improved agricultural technologies developed by CGIAR centers often failed to have the anticipated effect on local agricultural practices which would be a justification for their work. This failure was generally attributed to the weak organization of national agricultural programs.
ISNAR’s first director was Dr. Bill Gamble, former director of the International Institute for Tropical Agriculture (IITA) in Nigeria. In the course of 1982, Bill invited me to apply for the position of senior officer responsible for the integration of Farming Systems Research into national research programs.
The focus of my work at ISNAR was evaluating the national agricultural research capacities of developing countries, in terms of the number of research personnel and their qualifications; their research programs and activities; their research facilities including field stations, laboratories and transportation; and their funding. The next step was to formulate reorganization and investment plans together with the responsible government departments, various multilateral and bilateral donor agencies, and the executive staff of national research institutes. This work brought me back to Burkina Faso, but also to several new countries: Ivory Coast, Niger, Guinea-Conakry, Somalia, Rwanda, Kenya, and Madagascar, besides Indonesia and Laos.
Predictably, the ISNAR work was often tangled with political sensitivities, not only of local executives but also of international funding agencies, all of which had different expectations and political agendas. Over the years I learned that this was not really the type of work that I enjoyed, and by 1989 I had hit a dead end, both professionally and emotionally, fearing that I had disqualified myself from the kind of work – field work! – that I found much more exciting.
If nothing else, working for ISNAR has certainly helped me to better understand the role of my discipline, soil science-agronomy, within a broad international and political/policy framework. Luckily, at this very moment, KIT invited me back as senior agronomist in support of their Farming Systems Research (FSR) program that covered a portfolio of long-term field projects in Mali-Sud (Sikasso), Indonesia (Malang), Tanzania (Lake Zone), Zambia (Western Province), Benin, and later, Kenya.
In October 1990, I started supporting these projects with the daunting objective to compile project field experiences gained from an agroecologically and socio-culturally diverse set of countries and bring these together as lessons learned (in terms of technology as well as management) for future (rural) development projects. High points of this period were my renewed involvement in the Sikasso Farming Systems project along with a broadened support for the FSR activities of the national IER institute (l’Institut d’Economie Rurale).
Between 1992 and 1994, the Red Soils project in China’s Hunan Province was a major experience. KIT was charged by the Asian Development Bank with a project to establish six demonstration sites of 10 to 15 ha each had to be established under a project of the Asian Developemnt Bank. For these sites we had to plan and implement low external input methods (such as agroforestry) for soil conservation and land reclamation on severely degraded and gullied lands/slopes. As teamleader of four KIT colleagues and a team of Chinese experts the sites had to established in collaboration with the local population. I could write a book on all the miscommunications, misconceptions, political maneuvers, misunderstandings, and the cultural differences between us and the Chinese colleagues.
New opportunities by becoming independent: STOOP Consult (1997- 2004)
Meanwhile at KIT headquarters in Amsterdam -- when finally we thought we were getting a successful international program off the ground -- it was our own KIT executive board that slashed the newfound confidence and enthusiasm. My disappointment was such that in July 1997, I decided to move on and start my own one-man business, Stoop Consult: R&D for tropical agriculture. It felt like ‘a leap into the dark’ because I had no previous entrepreneurial experience. However, everything turned out to be surprisingly positive.
Again it was Les Swindale (retired by then) who played a crucial role. He recommended me to Kanayo Nwanze, who had just been appointed Director-General of WARDA (now the Africa Rice Center) in Ivory Coast. In no time I found myself as interim Director of Research in Bouaké for nine months, with another six months in 2001. Once again this was a new experience with large challenges as the institute faced acute financial problems while in my position I had to deal with an arrogant/rebellious group of scientists.
In early 1998 and upon Kanayo’s advice, I got in touch with Cornell University (USA) about their rice work in Madagascar. It brought me into contact with Dr. Norman Uphoff and the remarkable as well as controversial System of Rice Intensification (SRI), which had been developed in the 1980s by Père de Laulanié, a French Jesuit. In vain I tried to interest WARDA researchers in this system, but their responses were negative, if not denigrating.
This was hardly surprising, given that De Laulanié’s ideas ran quite counter to conventional Green Revolution thinking. It was only due to my previous field experience with ICRISAT in Burkina Faso that I was able to recognize the relevance of his ideas. As none of the WARDA scientists showed any interest, I decided to established some experiments myself at the M’be farm to verify the SRI ideas. The mental support for this from Kanayo and from my successor as director of research, Amir Kassam, ultimately gave a new turn to my work and interests .
After returning to the Netherlands in June 1998, and at Uphoff’s request (himself a social scientist), I started a desk study on the agronomic and plant-physiological factors that might explain the often spectacular grain yields with SRI. The end result was the publication of a journal article, co-authored with Uphoff and Kassam in Agricultural Systems in 2002.
This publication in an internationally-recognized scientific journal was a breakthrough. The established order (researchers at IRRI, WARDA, Wageningen, Cornell, and other US universities) was up in arms with accusations that SRI was based on “measurement errors” or “UFOs” (unconfirmed field observations), also calling it “voodoo science.” There were lists of arguments presented (but with no valid field evidence!) to prove our claims wrong and to assert that SRI’s high yields were theoretically impossible.
As fascinating as this SRI research was, it didn’t provide me any direct income. The Dutch revenue service would only recognize Stoop Consult as a one-man business if it had at least three paying clients each year. So I took on some additional projects, among which were interesting missions on low external-input agriculture, farming systems participatory research, and linking research and extension (assignments in India, Zimbabwe and Guinée-Conakry).
A study in 2002 for the CGIAR’s Technical Advisory Committee (TAC) in West Africa on the question “why are so few results of agricultural research actually applied by farmers?” provided an appropriate end of my formal professional career. This interesting study took me back to two West African countries (Mali and Guinea-Conakry) where I had been actively involved over many years and to assess in the field the impact of past projects and research efforts. What might be the reasons (technical, political, institutional) that these results were often very different from those anticipated? Results of that study were published in a peer-reviewed journal in 2005.
Over these last few years, however, I had become increasingly fascinated by the SRI case and by the opposition against it from mainstream researchers. What to do next?
Coming full cicle: from Green Revolution to Agroecology: From SRI to SCI and ecological intensification.
Taking formal retirement in 2003 (at 60) by no means meant that I had lost interest in agricultural research and farming. On the contrary, it provided an opportunity to pursue SRI/SCI, and more generally the development of environment-friendly ways of farming, relatively independently from formal institutions.
Already at WARDA, I had arrived at the conclusion that SRI was a form of common-sense (rice) agronomy. This comprehensive agronomy challenged mainstream Green Revolution thinking that is largely based on introducing HYVs (high-yielding varieties) in combination with the use of agricultural chemicals (NPK fertilisers and crop protection). The latter essentially constitutes a simplistic, scientifically-naïve approach that will not provide long-term solutions for complex problems such as sustainability, food security and poverty alleviation.
I started off my independent research endeavor into SRI in early 2003 with a two-week visit to Madagascar, coordinated by Sebastian Rafaralahy and Justin Rabenandrasana from the NGO Association Tefy Saina and by Prof. Robert Randriamiharisoa from the University of Antananarivo. I wanted to see successful SRI in the field and to appreciate the conditions under which it had evolved. This was an eventful and revealing visit as only on day-four of our excursion did we see a truly impressive SRI field.
The independence and collaboration with Norman Uphoff also provided the opportunity to respond formally to various articles in peer-reviewed journals by renowned scientists (from IRRI, Cornell and Wageningen) that through questionable research and flawed arguments tried to undermine the scientific credibility of the SRI ideas and practices. Subsequently, this was referred to on the internet as ‘the Rice Wars.’ These exchanges in the peer-reviewed literature have attracted wider attention among donors and development agencies, particularly NGOs, while formal research and government (agricultural) ministries often remained reluctant to openly promote SRI.
During the period until 2010, I managed to visit Mali and Burkina Faso where several initiatives on SRI had been started. It was interesting to see SRI’s performance under diverse agroecological conditions and to hear the reactions by farmers. In 2008, a challenging visit was made to Senegal to support an American Ph.D. candidate who was doing his field research under the guidance of WARDA staff. Given WARDA’s reservations about SRI, this provided a complex situation of opposing institutional and personal interests. At least the student reached his objectives: to get his PhD and to land a position within the CGIAR network. At another level in Holland, I renewed my collaboration with ILEIA and its Farming Matters magazine with its March 2013 issue devoted to SRI.
By 2010, I decided to write one more ‘final’article about SRI to document the mostly agronomic insights gained since getting involved. It was around that time that Norman sparked a collaboration between Cornell, Wageningen and IRRI to finally settle the controversy with international rice researchers through a joint study funded by the Gates Foundation and to be conducted in various Asian countries. The financial crisis of 2008/9 interfered with these plans, but some ideas were picked up by Wageningen faculty and subsequently implemented in India with Dutch funding.
Interestingly, this research project was initiated by the Socio-Economics Department of Wageningen University which viewed SRI primarily as a ‘social movement’ with possible relevance for extension approaches. The project, funded by the Dutch government, brought to Holland four Indian PhD candidates (with NGO backgrounds) representing very different rice-growing regions (Uttarakhand, Odisha, Andhra Pradesh and Tamil Nadu).
Although I had been aware of the project and had even contributed informally to its formulation, I had no intention to get involved in it beyond occasionally hosting the PhD candidates at my home. This all changed, however, when they invited me to visit them in their respective field research locations and meet up with their local research supervisors, Drs. Thiyagarajan (TMT), Shambu Prasad, and Amod Thakur, the latter having conducted crucially important, on-station field experiments on SRI over the years.
All together I made some four visits to India in the period 2011-15 that allowed me to establish new contacts and expand my insights in both the biological and socio-cultural issues of introducing SRI practices with farmers. Not only that, the various SRI practices proved increasingly relevant also to other crops like wheat, millet, sorghum, maize, and sugarcane, and these methods were not only valid for smallholders in India. We also established contacts with and visited an advanced, large-scale biological farmer in Noord Beveland (The Netherlands) who had been practicing such methods for wheat already for many years.
The insights gained from the Indian project have been very valuable from both a scientific biological aspect in explaining alternatives leading to forms of environment-friendly ecological intensification, as well as the complex socio-political aspects involved in introducing changes in the prevailing conventional (modern) agriculture. This inspired me to write two more ‘final’ articles together with my Indian friends that were published in 2016 and 2017.
Looking back I consider myself privileged. Based on a childhood affinity with farming, I chose the profession of soil scientist/agronomist – a profession that touches upon essential and highly diverse aspects of our society: biological/technological as well as socio-economic, political and institutional. Soils, agriculture and high quality (food) products are crucial elements to any society; yet these will be readily affected by environmental diversity and variability.
This makes their sustainability a critical and exceedingly complex issue in the absence of proper appreciation and adequate knowledge about the (micro)biological and social processes involved. As such, the SRI/SCI insights gained should be valuable in developing ecological approaches towards intensification and hence limiting the harmful effects of intensive farming on the overall natural environment.
NOTES AND REFERENCES
 This elderly professor used to invite all new students, three at a time, for a meal at his home. He continued to do so even at very old age and even when he was seriously ill. During these dinners, he used to share some of his wisdom that has stayed with me, like the comment about “the spark,” but also his pronouncements: “There is no alternative to quality!” and “Most of us will not be such brilliant scientists, so we’d better be diplomatic.”
 Swindale and I crossed paths several times: at ICRISAT, where he was appointed as Director General in 1977 (until 1992), and in 1997 recommending me to Kanayo Nwanze.
 Most successful were ‘Ion adsorption mechanisms in oxidic soils; Implications for point of zero charge determinations,’ Geoderma 23, 303-314 (1980); and ‘Phosphate adsorption mechanisms in oxidic soils: implications for P-availability to plants,’ Geoderma 31, 57-69 (1983).
 In contrast to the general opinion in the Netherlands at the Ministry, the CIMMYT wheat and maize programs were quite practice-oriented, despite their heavy focus on plant breeding. Borlaug’s maxim “You have to talk to plants” has always stayed with me, and Ernie Sprague (Director Maize Program) taught me how to “look at plants”, i.e. how to search for plant characteristics within a maize population and distinguish ‘families’ for interbreeding. However, agronomic aspects were considered location-specific, and thus beyond what international research could and should handle. Moreover, general agronomy was held in rather low esteem internationally, being location-specific. A fellow Indian student at the University of Hawaii reacted once as we talked about our future ambitions: “Agronomist? You will be a mister-nobody, better aim for soil chemistry!”
 The experimental fields all sloped towards a river marshland (bas-fond) transecting the land of the experiment station, causing erosion and run-off problems and considerable micro-variability within the fields. Being used to CIMMYT’s homogeneous experimental plots, it seemed simply impossible to conduct proper field experiments here. What to do? We simply had to make the best of it.
 Kanayo Nwanze with whom I fought several battles at that time, would later become DG of WARDA, where I supported him twice as interim Director of Research; in 2009 he became president of IFAD, the International Fund for Agricultural Development in Rome.
 When Dr. David Norman, one of the ‘founding fathers’ of FSR, visited the agronomy plots at the Kamboinsé experiment station in 1978, his reaction was significant: “But, Willem, you are conducting FSR on-station!”
 H.I.D. Vierich and W.A. Stoop, ‘Changes in West African savanna agriculture in response to growing populations and continuing low rainfall. Agriculture, Ecosystems and Environment 31, 115-132 (1990).
 J. Th. Staveren and W.A. Stoop, ‘Adaptation to toposequence land types in West Africa of different sorghum genotypes in comparison with local cultivars of sorghum, millet and maize,’ Field Crops Research 11, 13-35 (1985); W.A. Stoop, ‘Adaptation of sorghum/maize and sorghum/pearl millet intercrop systems to the toposequence land types in the north sudanian zone of the West African savanna. Field Crops Research 16, 255-272 (1987).; and W.A. Stoop, ‘Variations in soil properties along three toposequences in Burkina Faso and implications for the development of improved cropping systems, ‘Agriculture, Ecosystems and Environment 19, 241-264 (1987).
 I had first met Bill already in 1975 when he visited CIMMYT and tried to recruit me as agronomist for IITA.
 The lands to be reclaimed turned out to be bare slopes dissected by deep gullies. We eventually realized that we were dealing with the heritage of massive deforestation brought on in the 1960s by Mao’s “Great Leap Forward.”
 The Chinese figured that “every Project” would bring in development funds, even if it was a low-input project. But at the same time, they reckoned: low input = low output = low PROFIT – sorry, this is not interesting! They considered labour to be a low-input factor. Their original proposals suggested to mobilize thousands of labourers for all sorts of digging work for terracing and trenching because this meant its total cost = zero.
 WARDA, now known as Africa Rice, had gained international recognition for cross-breeding high-yield Asian rice (O. sativa) with low-yield, drought-tolerant African rice (O. glaberima) characterized by profuse vegetative growth. This hybrid cultivar known as NERICA (NEw RIce for AfriCA) combines the positive characteristics of both parents and is particularly suited for rainfed (non-irrigated) rice production in large parts of West Africa. WARDA’s success with NERICA was key to attracting new sources of funding.
 Amir Kassam was my successor as Director of Research at WARDA, who, unlike the scientisits, was very interested in SRI and later on became a driving force of Conservation Agriculture.
 W.A. Stoop, N. Uphoff and A. Kassam, ‘A review of agricultural research issues raised by the system of rice intensification (SRI) from Madagascar: Opportunities for improving farming systems for resource-poor farmers,’ Agricultural Systems 71, 245-274 (2002).
W.A. Stoop and T. Hart, ‘Research and development towards sustainable agriculture by resource-poor farmers in Sub-Saharan Africa: Some strategic and organizational considerations in linking farmer practical needs with policies and scientific theories,’ International Journal of Agricultural Sustainability 3, 206-216 (2005).
 W.A. Stoop and A.H. Kassam, ‘The SRI controversy: A response,’ Field Crops Research, 91, 357-360 (2005); N. Uphoff, A. Kassam and W.A. Stoop, ‘A critical assessment of a desk study comparing crop production systems: The example of the ‘System of Rice Intensification’ vs. ‘Best Management Practice,’ Field Crops Research 108, 109-114 (2008); W.A. Stoop, A. Adam, and A. Kassam, ‘Comparing rice production systems: A challenge for agronomic research and for the dissemination of knowledge-intensive farming practices,’ Agricultural Water Management 6, 1491-1501 (2009).
 W.A. Stoop, ‘The scientific case for system of rice intensification and its relevance for sustainable crop intensification,’ International Journal of Agricultural Sustainability 9, 443-455 (2011).
 A.K.Thakur, N. Uphoff and W.A. Stoop, ‘Scientific underpinnings of the System of Rice Intensification (SRI): What is known so far?’ Advances in Agronomy 135:147-179 (2016); W.A. Stoop, Sabarmatee, P. Sivasubramanian, A. Ravindra, D. Sen, C. Shambu Prasad and A.K. Thakur, ‘Opportunities for ecological intensification: Lessons and insights from the System of Rice/Crop Intensification – their implications for agricultural research and development approaches,’ CAB Reviews 12, 036 (2017).