THE EFFECT OF NITROGEN TOP-DRESSING AND PLANT DENSITY ON THE YIELD AND LODGING OF POPPIES (PAPAVER SOMNIFERUM L.)

In the experiment described in this paper ammonium nitrate was top-dressed onto poppies (Papaver somniferum L.) at No = zero, N1 = 40 and N2 = 80 kg N/ha at the "hook" stage about two weeks before flowering in factorial combination with densities of D1 = 25, D2 = 50, D3 = 100 and D4 = 200 plants/m2. The experiment was irrigated until one month after full bloom.

The amount of lodging was strongly affected by density and varied with the basis of measurement. The numbers of plants lodged showed a marked interaction effect between nitrogen and density. At D1 and D2 the number of plants lodged was small (10%) and was not affected by nitrogen. At D3 the number lodged increased successively with N to 33% at N2 and at D4 the number lodged was about 60% for all levels of N. A large number of plants were thin stemmed and spindly with very small heads (capsule plus seed) and generally percentage lodging based on the weight of head lost was only about half or less than half of the lodging based on plant numbers.

The yield of machine harvestable poppy heads also followed an N x D interaction effect in which nitrogen had little effect at D1 and D2, a depressing effect at D3 and a positive effect at D4. Nitrogen increased the morphine concentration of capsules by a maximum of 7% and there was a general opposite trend for density to decrease capsule morphine concentration by up to 8% at D4. The yield of morphine followed the same N x D interaction pattern as head, seed and capsule yields.