may be the increasing prices of fertilizers says Ny Times:
"Prices at a terminal in Tampa, Fla., for one fertilizer, diammonium phosphate, jumped to $1,102 a ton from $393 a ton in the last year, according to JPMorgan Securities, which tracks the prices. Urea, a type of granular nitrogen fertilizer, jumped to $505 a ton from $273 a ton in the last year.
“This is a basic problem, to feed 6.6 billion people,” said Norman Borlaug, an American scientist who was awarded a Nobel Peace Prize in 1970 for his role in spreading intensive agricultural practices to poor countries. “Without chemical fertilizer, forget it. The game is over.”"
More news from Andrew Leonard and others here.
Two years ago, there was an announcement by Indian scientists Simi Sathyaseelan and Sumam George that latext sludgemay be a good substitute for the currently used phosphorus compounds:
"Four month soil incubation studies showed that based on the phosphorus release pattern, latex sludge is comparable or even superior to two other conventionally used commercial phosphatic fertilizers, Rock Phosphate (RP) and Super Phosphate (SP). For field confirmation of the laboratory results, two pot culture studies (1 main + 1 residual) in completely randomized design with chilli (Capsicum annuum L.), a crop with high phosphorus demand, were undertaken. The soil used was sandy loam (Vellayani Series–Typic Kandiustult), acidic in reaction (pH 5.63), high in organic carbon (0.63 %) and available phosphorus (91.28 kg ha-1), but low in available nitrogen (215.13 kg ha-1) and available potassium (91.84 kg ha-1). The treatments were fixed so as to compare the effect of phosphorus supply to the crop from latex sludge against that from SP and RP when each was used singly or when latex sludge was used in different combinations with the other two. Statistical analysis of the biometric characters of the crop namely growth (plant height, number of leaves and branches, leaf area and days to flowering), yield (number of fruits per plant, length, girth and weight of fruit and fresh yield per plant) and quality (ascorbic acid, capsaicin, oleoresin and protein contents) showed that all these traits were favourably disposed towards the treatment combination in which the crop's phosphorus requirement was met equally by latex sludge and RP (half-half). "
But I do not know of any later developments.
P.S. Two background articles.UN Outlook for 2011-12(not read yet).