Seeing Jon's recent thread and fascinating picture of the nearly flattened split fig made me think about this and to see if there was anything written in any of the publications that I have reviewed.
The general consensus is that rain/moisture causes splits (for those of us growing figs in non-fig wasp areas), but this may not be the complete reason. I am fascinated by Rixford’s observations that trees growing near drainage ditches (having continuous moisture) split less in contrast to figs in the dry orchard when water was applied. I am wondering if keeping split prone figs evenly moist might reduce problems when rain hits. This might be easier to control in containers. Perhaps there is a way that a cover could be put over the soil. For those of us that want to grow split prone trees, this might be interesting to think about. I also included some other sources about splitting.
Smyrna Fig Culture by G.P. Rixford - USDA Bulletin #732, 1918 page 34. http://books.google.com/books?hl=en&lr=&id=paQUAAAAYAAJ&oi=fnd&pg=PA1&dq=syria+ficus+carica&ots=SLOoFbbyp_&sig=xarAq6HgAbYFcCNEs9EH9rtxk-Q
‘The Splitting of Figs’ - In certain seasons a few of the ripening figs split upon the tree. While this is an injury to some extent, it is not a very serious one. There seems to be a difference of opinion as to the cause. Some growers are firmly of the opinion that it is caused by too many Blastophagas, or, in other words, by over pollination; others think that it is due to too much irrigation. The writer, however, is convinced that these are not the principal causes, but that the cause is principally climatic. If damp weather, not necessarily rain, occurs during the ripening period, it seems to stimulate the circulation of the sap and gorges the fruit with juice until the pressure is such that the tender skin fails to resist and the fig splits open. If, however, this period of dampness is followed by warm, sunny weather, such figs dry without souring, the split closes up, and they are readily disposed of at 2 to 4 cents per pound, which pays for gathering and caring for them. The proportion of figs that split rarely exceeds 25 percent; nearly always the proportion is much less.
Trees have been observed standing on the banks of irrigating ditches where the supply of moisture was continuous and showing less split figs than trees in the same orchard that received only occasional irrigation. It appears that when the ground has become too dry and water is then applied, a stimulation in the circulation of the sap is caused and is almost invariably followed by more or less splitting, while if the supply of moisture has been continuous, few, if any splits occur. The splitting of oranges and prunes is attributed by many to the same cause.
The Fig: Botany, Horticulture and Breeding by Moshe A. Flaishman, Victor Rodov and Ed Stover p 136 http://agspace.nal.usda.gov:8080/dspace/bitstream/10113/15714/1/IND44035516.pdf
Splitting is the result of sudden changes in the internal fruit pressure brought on by cool temperatures and/or high humidity as the fruit matures. ... may also result from excessive pollination and the growth of too many developing seeds....
Ray Givans and Fred Born - The New Fig Booklet 2000, page 8
Heavy rains and excessive or sporadic watering may cause the fruit to split.
Figs in Coastal Southern California by Richard Watts from CRFG - The Dec 1991 issue of the Fruit Gardener http://www.kalron.com/kalstor/pub/crfg/fig-2.htm
Excessive watering during the ripening period can cause splitting.... This only applies to fig trees planted in the ground.
Ingevald