The use of lime on land

Pot tests made with clover on soil from each of the 36 plats of Tier 1 showed a range in growth of clover from 2.60 grams on a very sour plat to 61.75 grams on a good sweet one. Of the 36 plats, 12 were found neutral or alkaline in reaction, and 24 showed varying degrees of sourness. The sourest plat required 2,086 pounds of CaO per acre-7-inches to neutralize the acidity as shown by the Veitch method. This amount, when applied, left a further requirement of 485 pounds at close of pot test. Pots from this plat without lime produced 3.85 grams green clover, and when limed at the rate of 2,000 pounds of limestone in excess of requirement produced 74.65 grams. The growth of clover on the unlimed pots correlates well with the yields of hay removed from the plats at the present date. The second crop from the pots was slightly better than the first. The total of the two crops was a great draft on the soil and for 16 plats giving best results was equal to 48,000 pounds of green clover to the acre-foot of soil. Soil from limed plats showed a reduction in growth of clover when more lime was applied. Plats with a low lime requirement gave only a small increase in growth when lime was applied. A marked increase in growth resulted from lime on all plats that were decidedly acid. The greater the sourness, the larger the response to lime. Clover is not depressed by sourness, requiring 500 pounds or less of CaO per acre. Above this amount, the depression increases with the sourness and growth practically ceases when the lime requirement reaches 1,500 pounds of CaO per acre-7-inches. Soil of plats to which land plaster was applied was slightly acid, but the additional lime further depressed growth of clover. The nitrate of soda plats were less sour than those receiving nitrogen as dried blood. Plats receiving manure were equally as sour as those having dried blood. The sourest plats were those receiving nitrogen as sulphate of ammonia. When the soil from these plats was made sweet with lime or limestone, it produced clover exceeding in amount that from any other plats. Plats receiving phosphorus as ground bone were less sour than those receiving equivalent amounts of dissolved bone black. Lime influenced the root growth in the same manner and to somewhat greater degree that the tops. The root growth was equal to 41 percent of the growth of the tops and roots combined. For 18 plats giving best results with limestone, the root growth in the pots was equal to 8,575 pounds of dry matter per acre-foot of soil. Of 48 soil samples treated with slaked lime and limestone in amounts sufficient to meet the lime requirement as indicated by the Veitch determination, only seven were satisfied when reexamined at the close of the pot test. Five of these were satisfied by virtue of probable error in the original determination. When a ton of limestone in excess of requirement was applied, only three remained acid at the close of the test. One of these was evidently contaminated, and the other two were only slightly acid. Slaked lime applied in amounts indicated by the method reduced the average requirement by 71 percent as based on the average amount applied. On the same basis limestone reduced the requirement by 72 percent. This indicates that the amount indicated by the method should be increased by about 50 percent in order to meet the real soil requirement. An important fact in this extensive test in that finely ground limestone has been fully as prompt and effective in reducing soil acidity and promoting the growth of clover as equivalent amounts of slaked or caustic lime.