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2 from 18.21 inches in 1899 to 75.65 inches in 1957. Prevailing' winds are southerly to southeasterly during most months. In January and February northerly winds prodominate. The mean annual relative humidity is 83 percent at 6 A.M., 56 percent at noon, and 55 percent at 6 P.M. In winter, temperatures are mild. A low temperature of 32 degrees F or below occurs on about 2 nights out of 3. The daily high fails to exceed 32 degrees on an average of about 4 days per year. The area experiences frequent surges of cold continental air in winter. Cold fronts moving down from the north often are. accompa- nied by strong gusty winds and sudden drops in tem- perature; however, cold spells are short, rarely lasting longer than 48 hours before rapid warming occurs. Pre- cipitation may fall as rain, freezing rain, sleet, or snow. In summer, days are warm, particularly in July and August. There is little variation in the day -to -day weather during these months. Sunshine is about 75 percent of the total possible during summer. Refrigerated air condi- tioning provides the maximum comfort indoors. Spring and fall are characterized by warm days and cool nights. Cloudiness and showers are slightly more frequent in spring than in fall. Also, average windspeed is stronger in spring. The growing season (freeze -free period) averages 228 days. The average dates of the last freeze in the spring and the first in the fall are March 26 and November 9. About 50 thunderstorms occur each year. A few of these thunderstorms are accompanied by destructive wind, hail, or high intensity rain. Farming Farming is the leading industry in Lamar and Delta Counties. About 77 percent of Lamar County and 83 percent of Delta County is suited to cultivation. The aver- age farm size is 271 acres in Lamar County and 147 acres in Delta County. In recent years more people have been purchasing farms to supplement income from in- dustry. The main farm enterprises are crops, livestock, dairy- ing, and poultry. A few hardwood logs are harvested each year. The main cash crops are cotton, soybeans, grain sorghum, corn, wheat, peanuts, and alfalfa. A large acreage of bermudagrass is cut for hay. Livestock operations are primarily cow -calf. Supple- mental feeding is generally heavy from December to late February or March. There are few commercial feedlots in these counties. Natural resources r— Soil is the most important natural resource in Lamar and Delta Counties. Forage for livestock and food, fiber, and timber for market and home consumption produced 349 SOIL SURVEY from the soils of the counties are a major source of livelihood for many people. Water is an important natural resource. Several lakes provide high quality water for homes and industry. Scat -. tered aquifers throughout the area provide high quality water for home use. Wildlife produced on the farms, ranches, and game management areas provides recreation for many resi- dents. Gravel from high terrace deposits of the Red River and from the rectified North Sulphur River channel and chalk and limestone mined from bedrock provide materi- al for local road construction. Natural gas is produced by a few wells in the eastern part of Delta County. How .this survey was made Soil scientists made this survey to learn what kinds of soil are in the survey area, where they are, and how they. can be used. The soil scientists went into the area know- ing they likely would locate many soils they already knew something about and perhaps identify some they had never seen before. They observed the steepness, length, and shape of slopes; the size of streams and the general pattern of drainage; the kinds of native plants or crops; the kinds of rock; and many facts about the soils. They. dug many holes to expose soil profiles. A profile is the sequence of natural layers, or horizons, in a soil; it ex- tends from the surface down into the parent material, which has been changed very little by leaching or by the action of plant roots. The soil scientists recorded the characteristics of the profiles they studied, and they compared those profiles with others in counties nearby and in places more dis- taht. Thus, through correlation, they classified and named the soils according to nationwide, uniform proce- dures. After a guide for classifying and naming the soils was worked out, the soil scientists drew the boundaries of the individual soils on aerial photographs. These photo- graphs show woodlands, buildings, field borders, roads, and other details that help in drawing boundaries accu- rately. The soil map at the back of this publication was prepared from aerial photographs. The areas shown on a soil map are called soil map units. Some map units are made up of one kind of soil, others are made up of two or more kinds of soil, and a few have little or no soil material at all. Map units are discussed in the sections "General soil map for broad land use planning" and "Soil maps for detailed plan- ning." While a soil survey is in progress, samples of soils are taken as needed for laboratory measurements and for engineering tests. The soils are field tested, and interpre- tations of their behavior are modified as necessary