The effect of fertilizers and plant density on productivity of pyrethrum clonal nurseries

Abstract

Two experiments one on plant population, the of her on NPK fertilizers were carried out to determine the influence of plant density and fertilizers on the vegetative growth and propagation of pyrethrum. Clone 0/64/219 was usad for both experiments. In the plant population experiment, five plant densities - 18.0, 21.0, 25.5, 33.0 and 48.0 plants

per m were tested. Plant competition was found to affect the tillering potential of the young pyrethrum plant. It was. however, tiller production per plant, rather than tiller prod0ction on unit area basis that was significantly affected by competition. It was suggested that high plant densities were able to compensate for the low tillering capacity of individual plants by the great number of plants per unit area. The vigour of tillers produced - with regards to dry matter production and root length - was also influenced by the plant density. In terms of tota tiller production and the vigour of the tillers, the plant density of 25.5 plants per m2 obtained at a spacing of 25cm between rows and 20cm within row gave th8 best results. Management of plots under dense populations also posed a problem, especially in planting and weed control. Three types of fertilizers - Calcium ammonium nitrate, Double superphosphate and Sulphate of potash, each at three rates were tested. The rates were 0,65 and 130 Kg Nlha for the nitrogen fertilizer, 0,29.7 and 59.3 Kg Plha for the phosphate fertilizer and 0, 8.3.and 16.6 Kg Klha for the potash fertilizer. Only nitrogen application promoted tiller production, with best results in the absence of both phosphorus and potassium. Both nitrogen and phosphorus increased dry matter production, but not in the presence of high levels of potash. There was notable negative interaction between nitrogen and phosphorus, with regards to dry matter production. The effect of nitrogen on root length was doubtful, mor,e so in the presence of either phosphorus or potassium or both. Phosphorus and potassium encouraged root elongation, but their interaction was generally negative. It

was therefore concluded that an early application of phosphate appears necessary for the initial root and shoot developw,3nt, but not after the onset of tillering when nitrogen should be more beneficial.