known for hundreds of years (George Washington burned oyster shells to obtain lime for his fields), however, their benefits were not always fully understood. Most farmers spread manure and some guano on their cropland, but correct chemical balances for specific crops were achieved only infrequently. Often the small landowner did not have spare fields to lie fallow for a year—the ideal situation for soil enrichment. "We spread some lime a time or two, but not nearly enough," admitted Wilson McNair. "We got burned lump lime and dumped it on the ground in piles of one bushel and when it had slaked we spread it with a shovel." The spreading itself could be a problem, especially when the earliest trucks began to be used in the mid-1920s. A truck hauling seven or eight tons of lime would bog down in a wet field: "The only way you could get out was to dump the lime, and if you dumped the lime you were in the hole you got stuck in." Thus, a lack of understanding of soil building techniques was coupled with the physical difficulty of fertilization, to inhibit the optimum efficiency of the land in the early 20th century.[23]

With the soil prepared, the crops could be sown. In the fall, generally between mid-October and Thanksgiving, winter wheat was planted. A "drill" or mechanical planter drawn by horses was used, which could be adapted for use with oats, barley or rye. The area had once been a principal wheat-growing region, but in the early 20th century dairymen cultivated wheat chiefly for the straw which was used for bedding. In the mid-1930s, however, the availability of certified seed (seed which was grown to be of a uniform and established varietal type, much as genetically pure livestock was bred) raised the quality of Fairfax wheat and slightly increased the grain's marketability.[24] Edith Rogers, a long-time Floris resident and for many years a member of the Fairfax County Board of Supervisors, grew wheat on her family's farm to use in chicken feed, and to have milled into flour for home use. It was ground at the Herndon Milling Company.[25] Like the use of certified seed, increased understanding of fertilization and crop rotation practices boosted production of wheat per acre, yet it never gained prominence as even a secondary crop. In large part this was due to the fact that wheat was a less desirable ingredient in cattle feed than was corn or even soybeans.[26]

Corn was planted in the spring, generally in late April. Again a drill was employed, which, planting two rows at a time, enabled the farmer to plant about ten acres in one day. The wide variety of uses for corn made it Fairfax County's most important grain crop and a 1926 report on the area's agriculture observed that "nearly every farm has more or less corn."[27] Not only was the grain a chief ingredient in the dairy cattle's "concentrate" or feed mixture, but it was used to feed horses, chickens and to fatten pigs near butchering time. The leaves and stalks were ground for ensilage or stored in the shock for dry fodder. During the 1920s, County Agent Derr promoted a continual campaign to improve the area's corn production and even introduced a new variety, dubbed "Fairfax County White Corn," because of its local success. He also worked to increase yields of other popular strains, notably Reid's Yellow Dent. In a report on his work in this field in 1925, Derr shows his methods to be not far removed from the early genetic experimentation of Gregor Mendel.

Soybeans began to be introduced into the area during this period and Fairfax County farmers also sowed various grasses for summer pasturage and to make hay for winter feeding. Timothy and clover predominated among pasture crops. Some farmers persisted in raising alfalfa, despite H. B. Derr's repeated protests that it was unprofitable on the county's lime-poor soil.[29] A few ambitious farmers even experimented with grasses attempting to find those which produced the highest milk yields and one went so far as to have a special ladino clover seed brought from Oregon because he felt it increased the richness of his milk.[30] As with wheat and corn, improved varietal types and stricter control over the uniformity of the seed greatly aided the cultivator.