Response of Lachenalia growing in soil to interactions between nitrogen and phosphorus fertilisation in the nursery phase

Abstract

The interactions between nutrients required by plants play an important role in sustainable crop production. Both nitrogen and phosphorus are involved in a number of important functions in the plant such as carbohydrate and protein formation. The need to investigate either the antagonistic or synergistic effects of nitrogen and phosphorus originated after studying the role of nitrogen fertilisation in Lachenalia bulb production. A pot trial with two Lachenalia cultivars (Ronina and Rupert), five nitrogen (0, 70, 180, 330 and 520 kg ha-~) and five phosphorus levels (0, 10, 30, 50 and 80 kg ha-~) was conducted in a glasshouse. The applications of both nitrogen and phosphoruswere split into a third at planting and two thirds 10 weeks after planting. Neither the interactions between nitrogen and phosphorus, nor the phosphorus level significantly influenced the leaf area of Lachenalia plants. Phosphorus significantly influenced bulb firmness. The firmness of Rupert bulbs increased and Ronina bulbs decreased with an increase in phosphorus. The interactions between nitrogen and phosphorus did not influence the fresh mass, circumference or firmness of Lachenalia bulbs. Neither the interactions between nitrogen and phosphorus, nor the phosphorus level significantly influenced the nutrient content of Lachenalia bulbs. The sucrose content of Lachenalia bulbs increased and the starch content decreased with an increase in phosphorus. Phosphorus had in comparison with nitrogen little influence on the growth and development of Lachenalia, probably due to sufficient residual soil phosphorus. A proper study to establish optimum soil phosphorus concentrations for Lachenalia is warranted.