Abstract

Concentrations of the macronutrients (N, P, K, Ca and Mg) and micronutrients (Fe, Zn, Mn and Cu) in the fruit peel and pulp from grapefruit cv. Star Ruby fruits were estimated at monthly intervals during fruit development. The general order of abundance of the macronutrients was Ca > K > N > Mg > P in the fruit peel and K > N > Ca > P > Mg in the fruit pulp. Similarly, the abundance of the micronutrients followed the order Fe > Mn > Cu > Zn in the fruit peel and Fe > Zn > Cu > Mn in the fruit pulp. The concentrations of most elements in the fruit peel and pulp decreased during fruit development at 120–210 DAFS. Contents of N and P in the fruit peel decreased from fruit set to fruit maturity. However, both nutrients showed a small rise in concentration towards the end of sampling. Ca content in the fruit pulp decreased up to 180 DAFS and then increased towards maturity. Mn concentrations were relatively constant during fruit development, while there was decrease in concentrations of Zn and Cu in the fruit peel. Overall, the K, Ca, Mg, Fe and Mn level was higher in the fruit peel and the N, P, Zn and Cu level was higher in the fruit pulp. These results provide important data on macronutrient and micronutrient changes during fruit growth and development, emphasizing that grapefruit can be a good source of minerals.