Abstract
The growth of nine legume species on an acid, brown sandy clay loam Oxisol limed to different levels was investigated in a pot trial after adequate provision was made for all essential nutrients. Mitscherlich vegetation vessels of 14 kg capacity were used, with 12 plants poC 1, under controlled glasshouse conditions. Plants were harvested when necessary during the growing season and the material dried at 65°C. Total top growth was determined and the material pooled, milled and analysed for elements of nutritional importance.
The unlimed soil had an aver????e pH(H20) of 4.??5 at the end of the first year, while liming with the equivalent of 0.8, 3.2 and 6.0 t CaC03 ha -30 cm resulted m pH(H20) values of 4.8, 5.0 and 5.5, respectively. There were large differences between legume species in their ability to grow under the unlimed conditions. Caucasian clover and lucern were the poorest, whereas birdsfoot trefoil, white clover and especially greater lotus were the best. With progressive neutralization, however, growth improved considerably. The best yields at all levels of neutralization were obtained with those species that were the most acid tolerant, especially with white clover and greater lotus. Lespedeza yielded reasonably well in the unlimed soil and was virtually unaffected by liming. Foliar analysis was used to determine total nutrient uptake. From these data, poor growth could largely be attributed to problems with Ca and Mo uptake by some legumes. Liming would obviously have an extremely beneficial effect on both, as was in fact observed. It is clear that it is essential to give adequate attention to the nutritional background of acid soils before establishment of a legume crop. The data support the contention that acid soil infertility is a complex problem.
