Effects of lime and calcium on root development and nodulation of clovers

Acidic soils can reduce the nodulation of forage legumes. Studies with a Gilpin series silt loam (fine loamy, mixed mesic Typic Hapludult) from New, WV, were conducted to determine the effects of lime on root development, and to assess effects of soil Ca and pH on nodulation. Liming increased soil pH from 4.8 to 5.3, nodulation, and root growth of white clover (Trifolium repens L., cultivar Huia) 28 d after planting. Seedlings from unlimed soil formed fewer indeterminate and determinate roots. Next, soils were amended with either CaCO3 or a mixture of CaCO3 and CaSO4 to achieve a soil pH of 4.7 to 6.1 and soil Ca of 170 to 680 mg kg(-1) soil. There was a strong quadratic relationship between number of nodules per white clover seedling 28 d after planting and soil pH. Another experiment was conducted to determine if these trends were expressed under field conditions. In 1993, field plots were amended with lime or a coal combustion by-product that supplied Ca as CaSO4 and seeded in 1994 to cool-season grasses. In spring of 1998, plots were drilled with either red (Trifolium pratense, L.) or white clover. The nodules per primary root were determined in May (1998,1999) and August (1998). Number of nodules per primary root was more closely associated with soil pH than soil Ca. These results indicate that changes in nodulation were more closely, associated with changes in soil pH than soil Ca.