Lucerne responses to lime and interactions with other nutrients on granitic soils

Abstract

Experiments were carried out in the field and glasshouse to determine the requirements for lime and nutrient elements by lucerne growing on moderately acid, weakly buffered granitic soils of the Northern Tablelands of New South Wales. The initial field experiment, which was an omission type at two sites with basal applications of phosphorus and sulfur, gave responses only to molybdenum, whilst on the 'complete' nutrient treatment (potassium, magnesium, molybdenum, manganese, boron, copper, zinc, cobalt and iron), there were large responses to lime. The subsequent glasshouse experiments gave large positive interactions between lime and the complete nutrient treatment and also between lime and phosphorus. The interactions between lime and complete nutrients involved mainly boron and to a lesser extent molybdenum, but at least one other nutrient, probably potassium, was also involved. However, the largest interaction was between lime and phosphorus. There was little indication that the lime effect was caused by increased nutrient availability in the soil or by improved root nodulation; it appeared to be associated with greatly improved root growth. White clover differed from lucerne in giving no interactions between lime and other nutrients and was much less sensitive to lime-induced boron deficiency. The results' of these experiments indicate that lucerne yields on these granitic soils cannot be maximized by the application of nutrient elements unless lime is also applied. Likewise lime has little effect unless deficient nutrients are also applied. Near-maximum yields were obtained with lime at 2.5 t/ha in the presence of adequate levels of deficient nutrients.