"Yes, a chemical analysis to ascertain the absolute amount of plant food in the soil. I think of it as an invoice; but I see that you do not report any such analyses." "No, we do not," answered the Chief. "We have been investigating the mechanical composition of soils, the chemistry of the soil solution, and the adaptation of crop to soil. We find that farmers are not growing the crops they should grow; namely, the crops to which their soils are best adapted. For example, they try to grow corn on land that is not adapted to corn." "It seems to me," said Percy, "that our farmers are always trying to find a crop that is adapted to their soil. Down in 'Egypt,' which covers about one-third of Illinois, the farmers once raised so much corn that the people from the swampy prairie went down there to buy corn, and hence the name 'Egypt' became applied to Southern Illinois. But there came a time when the soil refused to grow such crops of corn; the farmers then found that wheat was adapted to the soil. Later the wheat yields decreased until the crop became unprofitable; and the farmers sought for another crop adapted to a still more depleted soil. Timothy was selected, and for many years it proved a profitable crop; but of late years timothy likewise has decreased in yield until there must be another change; and now whole sections of 'Egypt' are growing red top as the only profitable crop. After red top, then what? I don't know, but it looks as though it would be sprouts and scrub brush, and final land abandonment, a repetition of the history of these old lands of Virginia and Maryland." "Well, can't they grow corn after red top?" asked the Chief. "Many of them try it many times," replied Percy, "and the yield is about twenty bushels per acre, whereas the virgin soil easily produced sixty to eighty bushels." "And they can't grow wheat as they once did?" "No, wheat after timothy or red top now yields from five to twelve bushels per acre, while they once grew twenty to thirty bushels of wheat per acre year after year. "If they rotate their crops, they would probably yield as well as ever," said the Chief. "No, that, too, has been tried," replied Percy. "The Illinois Experiment Station has practiced a four-year rotation of corn, cowpeas, wheat, and clover on an experiment field on the common prairie soil down in 'Egypt,' and the average yield of wheat has been only twelve bushels per acre during the last four years, but when legume crops were plowed under and limestone and phosphorus applied, the average yield during the same four years was twenty-seven bushels per acre." "Probably the increase was all produced by the green manure," suggested the Chief. "Organic matter has a great influence on the control of the moisture supply."