While the amount of water which a soil will hold is determined largely by texture, it is also considerably influenced by the amount and frequency of rainfall and the location of the soil as to whether it be upland or bottom land. The average percentage of water held by a soil during the growing season may be approximately determined in the following manner: Sample the soil in one of the following methods: Take to the field a spade, a box that will hold about half a bushel, and a pint or quart glass jar with a tight cover. If a cultivated field, select a place free from grass and weeds. Dig a hole one foot deep and about eighteen inches square. Trim one side of the hole square. Now from this side cut a slice about three inches thick and one foot deep, quickly place this in the box and thoroughly break lumps and mix together, then fill jar and cork tightly. Another method is to take a common half-inch or two-inch carpenter's auger and bore into the soil with it. Pull it out frequently and put the soil which comes up with it into the jar until you have a sample a foot deep. If one boring twelve inches deep does not give sufficient soil make another boring or two close by and put all into the jar. Take the sample, by whatever method obtained, weigh out ten or twenty ounces of the moist soil and dry it at a temperature just below 212 degrees. When it is thoroughly dry weigh again. The difference between the two weights will be the amount of water held by the sample. Now divide this by the weight of the dry sample and the result will be the per cent. of water held by the soil. Several samples taken from different parts of the field will give an average for the field. Repeat this every week or oftener through the season and an approximate estimate of the water-holding capacity of the soil will be obtained and consequently an indication of the crops to which the soil is best adapted. EXAMPLE. Weight of a soil sample, 20 ounces. When dried this sample weighs 173/4 ounces. 20 - 173/4 = 21/4, the water held by the soil. 2.25 / 17.75 = .12 plus. This soil held a little over twelve per cent. of water. If this soil continues to give about the same result for successive tests during the growing season, the results would indicate a soil adapted to cotton, late truck or corn. CHAPTER XVIII THE AFTER-CULTIVATION OF CROPS The term "after-cultivation" is here used in referring to those tillage operations which are performed after the crop is planted. Synonymous terms are "cultivation," "inter-tillage," "working the crop." After-cultivation influences the texture, ventilation, heat, plant food and moisture factors of fertility, but most particularly the moisture factor. Under ordinary circumstances the greatest benefit derived from after-cultivation when properly performed is the saving of soil water for the use of the crop. LOSS OF WATER BY EVAPORATION