Greene, Juan Nassau (1918–79), farmer and medical doctor, was born 19 September 1918 in Argentina, third son and fifth child of John Nassau Greene (1890–1973), native of Kilkea, Castledermot, Co. Kildare, and Annie Kathleen Greene (née Jackson) (1888/9–1973), third daughter of Francis Robert Jackson, of Kilkea house, Castledermot. One of the wealthiest farming families in Ireland, the Greenes had been in the country since the mid seventeenth century, when a Capt. Godfrey Greene (d. 1682), a ‘'49 officer’, acquired Moorestown castle, Co. Tipperary, and lands at Old Abbey, Co. Limerick. Juan's father, John Greene, was in the third generation of the family resident at Kilkea lodge, and lived for a time in Argentina, where several of his paternal uncles had emigrated (c.1870). One of the biggest farmers in Co. Kildare, John Greene was a founding member (1926) and sometime chairman of the Beet Growers' Association (BGA); elected a senator in 1938, he championed the idea of an umbrella organisation to represent the common interests of all Irish farmers. Protestant in religion, Juan Greene was educated at Kilkea NS and St Columba's college, Rathfarnham, Co. Dublin, then studied medicine at TCD, and graduated BA (1940), MB, BAO, and B.Ch. (all 1941). After practising for six months in Harrogate, Yorkshire, he enlisted in the RAF, serving as a medical officer during the second world war in Britain, Burma, and India. Returning to civilian practice, he worked in Sir Patrick Dun's hospital, Dublin, but retired from medicine in 1948 to concentrate exclusively on farming. Resident for the rest of his life at Levitstown house, Maganey, Athy, Co. Kildare, where he worked a substantial holding of 950 acres, he was an innovative tillage farmer, noted for his husbandry and ready adoption of progressive methods.
Following his father into prominence within farming associations, Greene was president (and his father trustee) of the first club in Ireland, at Athy, of the young farmers' organisation, Macra na Feirme (‘Sons of the Farms’) (1944); he was also active in the BGA. Believing that the multiplicity of competing regional and commodity-based farming associations left Irish farmers without any effective voice, he played a critical role in the founding of the National Farmers' Association (NFA), the first over-all farming organisation in Ireland. He represented the BGA in the series of meetings, sponsored by Macra, which discussed the possibility of launching a comprehensive national organisation (October 1953–August 1954). With progress stymied by two outstanding issues – a ban on oireachtas members holding office in the proposed organisation, and the compliance of affiliated associations to decisions of the umbrella organisation – at a decisive eleventh-hour meeting in Thurles, Co. Tipperary (30 August 1954), Greene broke the deadlock by proposing the founding of a new organisation. This would not be a merger or federation of existing associations, but a separate body acting alongside them on matters of common interest, with individual farmers holding dual membership. At the mass meeting of 3,000 farmers in the Four Provinces Hall, Dublin, on 6 January 1955, he moved the formal resolution to launch the NFA. Elected by the meeting to the provisional executive, he chaired the organising committee that oversaw the formation, within three months, of some 450 local branches comprising 12,000 members. Elected by the branches to the NFA's first national council, he was unanimously elected by the council as the association's first president (1955–62).
Throughout his tenure, Greene worked to establish the NFA's credentials as the principal voice of Irish farming. He regarded the aims of unified representation as including not only the securing of better prices for farm produce, but also influencing formulation of national agricultural policy to address underlying problems of low production, outmoded practices, undercapitalisation, and ineffectual marketing. He strived to achieve concordance between the NFA and the Irish Creamery Milk Suppliers' Association (ICMSA), the major commodity organisation, which remained aloof from the umbrella body, advised its members not to join, and resisted NFA organisation efforts in dairying areas. In 1959 Greene attempted rapprochement by proposing dissolution of the NFA national council and fresh elections to a new council, on which dairy farmers, as the most numerous sector, would be assured strong representation. With the ICMSA failing to respond to the proposal, relations between the two bodies became even more fraught and acrimonious. While welcoming formation of the Agricultural Research Institute (An Foras Tolúntais) (1958), Greene criticised the departure from the initial conception of a single institute encompassing not only research, but also teaching and advisory services, and fought to establish the institute's autonomy from the Department of Agriculture. He was appointed by minister for agriculture Seán Moylan (qv) to chair the Advisory Committee on the Marketing of Agricultural Produce (1957–9). Coinciding with the central role assigned to agriculture in the first programme for economic expansion, the committee's reports constituted the first detailed review of the markets for Irish agricultural produce since the early 1920s. Recommending strong export agencies to replace the existing system of trade by a large number of exporters, the reports resulted in establishment of An Bord Bainne (1961) to develop exports in dairy produce, and reconstitution of the Pigs and Bacon Commission (1964) as the sole exporter of pigs and pigmeat. Commencing in March 1958, Greene led NFA deputations to successive annual meetings with the taoiseach and minister for agriculture to discuss the contribution of agriculture to economic growth. Prominent within the International Federation of Agricultural Producers (IFAP), to which the NFA was affiliated as a full member from 1958, Greene twice chaired the body's policy committee, the principal group at IFAP world congresses. At meetings of IFAP and the Organisation for European Economic Cooperation (OEEC) he pioneered the idea of using the growing agricultural surpluses to help alleviate hunger in developing countries; his proposal was sponsored at the UN in March 1961 by the US ambassador, Adlai Stephenson. Elected to the IFAP executive in 1962, Greene served as an IFAP vice-president (1964–6). With the NFA attracted by the prospect of a European common agricultural policy under the treaty of Rome (1957), Greene urged that Ireland reserve the option of an independent decision regarding membership in the European Economic Community (EEC) regardless of what Britain did. In subsequent interventions after Ireland's 1961 application for EEC membership, he repeatedly advised farmers that the Common Market represented not a ‘utopia’ but an opportunity.
The subsequent flourishing of the NFA, and its successor, the Irish Farmers' Association (IFA), as powerful representative organisations owed much to Greene's idealism, energy, and organising sagacity through the formative early years. Modest and unassuming, he pursued a low-key, self-effacing leadership style, preferring quiet behind-the-scenes negotiation to public posturing, and earned wide respect for reasonableness and integrity. His position being full time and unpaid, and involving considerable personal expense and extensive travel throughout the country, he worked tirelessly to the ultimate detriment of his health. With conciliatory instincts and skills, firmly believing in the natural goodness and rationality of humanity, he remained convinced that measured, reasoned argument could persuade others to the correctness of one's opinion. Under the leadership of his successor, Rickard Deasy (qv), and in the altered circumstances of the mid 1960s, the NFA adopted methods far more militant and confrontational.
With his reputation for impartiality, Greene was appointed to nine government commissions covering a range of issues, from workers' compensation to higher education, and served as farmers' representative on several newly established semi-state bodies. On his voluntary retirement as NFA president, he returned to managing his farm, and sat on the boards of several businesses. He was a director from 1963 of both Batchelors Ltd and Fitzwilton Ltd. During his directorship of the B and I Steampacket Co. his wife launched the Inisfallen, at the time Europe's largest passenger carrying vessel, added to the fleet in 1968. A director of Goulding fertilisers, he was president in 1971 of the Fertiliser Association of Ireland. He was a director of the Bank of Ireland (1965–73), and of the Central Bank (1968–79). A governor of Gurteen agricultural college, he served from 1968 on the executive of the RDS, and was a show judge on several occasions. In recognition both of his work on a syllabus for a proposed agricultural course, and his efforts on behalf of Irish farmers, he was awarded a unique degree of honorary master of agriculture by TCD (1959). His portrait by Muriel Brandt (qv) was commissioned by the NFA. He married (14 September 1948) Juliet Elizabeth Woodford Causer, daughter of Geoffrey and Olive Causer of Rathgar, Dublin; they had one daughter and two sons. He died in the Richmond hospital, Dublin, on 9 November 1979, and was buried in Kilkea cemetery.