The well-known Maghribi mathematician and astronomer Abū al-‘Abbās Aḥmad ibn Muḥammad ibn al-Bannā’ (‘son of the architect’), or Abū al-‘Abbās Aḥmad ibn Muḥammad ibn Uthmān al-Azdī al-Marrākushī, was born in Marrakech (although some authors, following Casiri, say he was a native of Granada) on the 3rd or 4th Dhū’l-ḥijja 654/29th or 30th December 1256 and died there on 26th Jumādá al-thānī 721/31st July 1321. He is known to have studied with a great many teachers, mainly in Marrakech and Fez, and he in turn taught arithmetic, algebra, geometry, and astronomy in the madrasa al-‘Aṭṭārīn in Fez (Vernet 2008, n.p.). He also, most probably, worked as astrologer to the Marīnid sultan Abū Sa‘īd, although in his later life he apparently wrote a work directed against its use, despite the fact that he had penned a number of astrological treatises in his earlier years. Ibn al-Bannā’ authored some 74 works, half of which are treatises on mathematics and astronomy, while the other half comprises works on Qur’anic commentary, Islamic law and theology, rhetoric and logic, but also medicine and magic. His mathematical works remained popular until the last century, when commentaries on them were still being composed (cf. Samsó, 2007).
The only work of Ibn al-Bannā’ of some agricultural interest is his Kitāb al-anwā’ (known also as Risālah fī al-anwā’), an astronomical calendar in the almanac tradition based on the heliacal rising of stars or constellations and the acronychal setting of their opposites and the meteorological conditions, especially rainfall, associated with them. In it he quotes mainly from ‘Arīb ibn Sa‘īd/Sa‘d (probably his 10th century ‘Calendar of Cordoba’) but refers also to other scholars and their works such as Al-Khaṭīb al-Umawī (11th century), ‘Abd Allāh ibn Ḥusayn ibn ‘Āṣim (12th century), Ibn al-‘Awwām’s Kitāb al-filāḥa and a Kitāb al-nabāṭ, possibly that of Abū Ḥanīfah al-Dīnawārī (Rénaud, 1948, p. 6f.). Despite the Moroccan origin of the author, it seems that some of the astronomical data (length of longest day, etc.) correspond to the coordinates of Cordoba and have been taken without modification from the ‘Calendar of Cordoba’. Instead of the Christian saints’ days and other Christian holidays listed in the ‘Calendar of Cordoba’ however, Ibn al-Bannā’s work notes the death dates of Muslim martyrs such as ‘Alī and Al-Ḥusayn, the death anniversaries of Hebrew prophets recognized by Islam, Nawrūz, the Coptic Easter festival, etc. On the other hand, references to astrology, occult meanings of letters, and natural magic seem to be related to the author’s own Moroccan cultural background (cf. Rénaud, 1948, pp. 8-19). In spite of the brevity and relative paucity of farming notes given by Ibn al-Bannā’, his Kitāb al-anwā’ is nevertheless one of the very few sources we have on medieval agriculture in the Maghreb and North Africa outside Egypt.
Ibn al-Bannā’s Kitāb al-anwā’ follows the format of the ‘Calendar of Cordoba’ and other previous Arabic almanacs. The text consists of a short introduction followed by twelve chapters, one for each month. Under each month, the author mentions the number of days, the zodiacal sign, the mansions and important planetary data as well as the Syrian name of the month and the approximate length of the day. This is followed by a list of important dates in the respective month, mentioning important meteorological and climatic data as well as giving advice on agricultural works that should be carried out on particular days, etc. At the end of each month is a summary of recommendations on farming, health, diet, etc. For example, for January, Ibn al-Bannā’ gives the following agricultural notices:
1st of January: festival of the Messiah’s circumcision, a fatal day, there is always much wind on that day.
4th of January: favourable naw’, but if it doesn’t rain, this will remain the same throughout the year and the harvest will be deficient; if rain falls during the naw’ of Jabha ... the year will be excellent. If there is thunder on that day, it is a sign of abundance and of an excellent year. The sap begins to flow in the wood.
9th January: one begins to prune the vines.
14th January: one begins to plant trees and vines.
15th January: the sap reaches its full force in the trees, the birds appear. This is the end of the 40 longs nights of cold in winter.
17th January: the naw’ of Nathra begins; if it thunders, it is a sign of an abundant year.
18th January: that which is planted on this day will not be successful.
28th January: the beginning of spring according to the system of the Nabataean agriculture...
It is beneficial to prune the vines this month in order to remove that which is without power, and to remove vine leaves and leaves from trees in general that appear to be faded and dry. One chooses for this the bright hours of the day, avoiding the beginning and the end of the day. ... in this month, the water of the rivers warms and steam rises from the earth...