INFLUENCE OF LIME AND CALCIUM MAGNESIUM RATIO ON ALFALFA AND BIRDSFOOT-TREFOIL YIELDS/

A study was established in 1974 to examine the effects of lime and cal cium:magnesium (Ca:Mg) ratio in the limes on alfalfa (Medicago sativa) and birdsfoot trefoil (Lotus corniculatus L.) hay yields and botanica l composition of the hay. Lime was applied at rates of 0, 6.7, 13.4, 2 0.2, and 33.6 Mg/ha to an acid (pH 4.7) Mardin silt loam soil (coarse- loamy, mixed, mesic typic Fragiochrepts). Using four commercially avai lable lime sources and two mixtures of these lime sources, six Ca:Mg r atios were established for each lime rate. Calcium and/or magnesium su lfate were applied to plots that received no lime to obtain Ca:Mg rati os similar to those on the limed plots. The initial Morgan's solution extractable Ca was 450 mg/kg and Mg was 25 mg/kg. A 5 x 5 Latin Square design with five lime rates and five replications was used with the s ix Ca:Mg ratios as lime subplots. To improve mixing, portions of each lime treatment were applied before and after plowing in 1974 and after plowing in April of 1975. Alfalfa and birdsfoot trefoil were planted to one-half of each plot. The hay was harvested two or three times eac h year for five years. The alfalfa hay yield and legume component were significantly increased by the first two increments of lime (6.7 and 13.4 Mg/ha); however, the birdsfoot trefoil hay and legume component w ere significantly increased only by the first increment of lime. Maxim um yields for the legume component of both crops occurred at a soil pH of 6.5. The Ca:Mg ratios resulting from adding limes with different C a and Mg contents had no significant effects on the total dry matter h ay yields, percent legume in hay or alfalfa and birdsfoot trefoil yiel ds. Tt is difficult to justify the use of Ca and Mg base saturation ra tios for lime recommendations, or for determining the Mg concentration needed within the lime. Soil samples taken in fall of 1976 had mean s oil pH values of 4.6, 5.7, 6.1, 6.4, and 6.7 for the five lime rates.