SummaryThe roles of leaves, stems and reproductive parts in 14CO2 fixation and its subsequent movement in winter oil-seed rape, cultivar Jet Neuf, were investigated in two field experiments carried out on the Wye College Farm. The relative importance of these organs changed with time. At early flowering the leaves were the most important photosynthetic organs (66·8% 14CO2 activity). Midway between flowering and maturity the stems became the major supplier of photosynthates, a role eventually taken over by the developing siliquae (pods).These data stress the importance of keeping all photosynthetically active surfaces free from disease if efficient resource utilization and higher yields are to be achieved.
Relatively little information exists on the N and P needs of sunflower (Helianthus annuus L.) on infertile soils in non‐traditional production areas. The effects of four levels each of N (0 to 180 kg/ha) and P (0 to 60 kg/ha) applied to a thermic Typic Rhodustult were evaluated over three seasons. In all seasons there were highly significant seed yield responses to N and P a plied. The nature of the N ✕ P interactions indicated a greater response to N fertilization where P had been applied than in the absence of P fertilization. Maximum seed yields of up to 2,600 kg/ha were four to 13 fold higher than yields in the absence of applied N and P. Protein level in the seed was increased by N but decreased by P fertilization, the opposite effects being generally observed with respect to the oil. Nitrogen and P fertilization markedly increased the protein and oil yields, the N ✕ P interactions indicating that P fertilization was necessary for maximum response to applied N. The ratio of seed N to fertilizer N decreased with increased N fertilization but increased with increased P applied. The food energy yield and energy production efficiency of sunflower increased markedly with both N and P fertilization.
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