b'SENSE, NONSENSE AND SCIENCEBY: JOE SCHWARCZBIRD POOP CAUSING OBESITYL ong before scientists providedrevolutionize agriculture had been dis- are obese and a third suffer from diabetes. detailed accounts of plant nutrition,covered. As chemists later learned, ChileExactly why saltpetre and guano ancient farmers learned throughsaltpetre was mostly sodium nitrate, andincreased yields interested the great experience that crop yields decreasedwas an excellent substance for intro- German chemist Justus von Liebig. He from year to year. Eventually they con- ducing soluble nitrogen into the soil.decided to solve the mystery by burn-cluded that just like humans and animals,Nitrogen is a component of all proteins,ing plant material and analysing the crops had to be fed. Over 2000 years ago,including the enzymes which are instru- residue. In 1840 he published his classic Chinese rice growers were applyingmental in every phase of plant growth.Organic Chemistry in its Applications to burnt animal bones to their fields andMany of the vitamins that plants pro- Agriculture and Physiology which clearly nobody really knows when native Northduce as well as the chemicals with whichestablished him as the father of modern Americans began burying dead fishthey protect themselves against insectssoil science. Liebigs analysis revealed in-between rows of corn. We certainlyand fungi contain nitrogen. But whatthat the major minerals present in plant do know that they taught the practice tocaused the irritating, purplish vapours?residue were nitrogen, phosphorus and the Plymouth settlers. We also know thatSaltpetre is commonly contaminatedpotassium and that the reason saltpetre George Washington fertilized more thanwith sodium iodate, which when heatedand guano enhanced plant growth was American minds. Americas first presi- releases a variety of iodine compoundsbecause they were rich sources of nitro-dent took great interest in farming andthat can cause a choking sensation. gen and phosphorus. Potassium, he said, concluded that the criteria for better cropBy the seventeenth century, Chileancould be supplied by potash. This was growth were loose earth and soil amend- saltpetre was widely imported into Europe,originally obtained by soaking the ashes ments. He experimented with manure,along with another South American com- of wood to dissolve the potassium salts creek mud, plaster of Paris, lime, greenmodity that had been found to increase soiland filtering the suspension and boiling manure (ploughing buckwheat, cloverfertility. This was guano, or bird excreta.off the water in a pot to leave a white ash, and peas into the soil) and fish heads!Like saltpetre, it was an excellent sourcepotash which was mostly potassium The President was certainly on the rightof nitrogen and furnished phosphorus tocarbonate.track, each of these amendments wasboot. Peru was the first recognized sourceLiebig also determined that plants capable of contributing some nutrition toof extensive deposits of bird poop, but byneeded different minerals in different the soil. the 1800s many South Pacific islands wereamounts and propounded his Law of The most significant advance in fer- also found to be overflowing with seabirdMinimum which states that if one of the tilizer development, however, came aboutguano. To this day, guano is an importantnutritive elements is deficient or lack-in an accidental fashion. And for this wesource of fertilizer, helping to feed theing, plant growth will be poor even if can thank a Spanish missionary to Chileworld. But it has also helped overfeed thethe other elements are abundant. If the whose name has been lost to history.natives of the guano producing islands.deficient element is supplied, growth will Some natives had extinguished a fireContrary to what many may think,be increased up to the point where that by throwing some hard, dry earth ontoAmericans are not the fattest people inelement is no longer the limiting factor. the hot coals and were staggered by thethe world. That dubious honour goes toIncreasing the supply beyond this point acrid purple vapours that suddenly werethe inhabitants of the Pacific island ofis not helpful. Liebig went on to clearly released. Some sort of evil spirits, theNauru who boast of having one of theexplain that adding manure to soil was an natives probably thought, and grabbed ahighest per capita incomes in the world.excellent way of recycling these minerals few chunks of the dry earth to show theAnd that thanks to bird droppings!but suggested that more efficient ferti-priest, whom they assumed would haveFertilizer companies pay high prices forlizers with an ideal balance of nutrients an explanation. He didnt and threw thethe chance to harvest the guano, allow- could be developed.samples into his garden. A few monthsing natives to trade in their ploughsharesLiebigs theories launched research later, the alert missionary noted thatfor easy chairs. As their level of activityinto the systematic development of min-there was an increased growth of veg- decreased, imports of beer, meat anderal fertilizers without which we could etation where the chunks had landed.chips increased. The result is that aboutnot possibly feed the population of the Chile saltpetre, the fertilizer that wouldseventy percent of the natives of Nauruworld. 48IEUROPEAN SEEDIEUROPEAN-SEED.COM'