Response of growth and yield components of linseed to the onset or relief of nitrogen stress at several stages of crop development

Abstract

The effects of the onset or relief of nitrogen (N) stress on growth and on yield components of linseed ( Linum usitatissimum L.) cv. Glenelg were studied in a glasshouse experiment. Nitrogen stress reduced the production of tillers (secondary basal stems) and fruiting branches, but did not affect the harvest index of the shoot. Flower production in all plants occurred in two cycles, and N stress affected the rate of flower production during a cycle more than the duration of each cycle. The onset of N stress at flower buds visible ( bv) reduced growth by 75% and flower production by 60%. Relief of N stress at or before bv gave a full recovery of dry-matter production, and restored the numbers of tillers and fruiting branches to those of unstressed plants. The dominant effect of N stress on yield components was a reduction in the number of capsules per plant. The number of seeds per capsule, single-seed weight and seed oil percentage were not altered by N stress or by changed N supply. The N supply after bv determined seed and oil yields. Nitrogen stress after the end of the first flowering cycle ( ef) reduced capsule number, and seed and oil yields, by 33%. Relief of N stress before bv resulted in a complete recovery of seed and oil yields, but there was a 23% yield penalty if N stress was not relieved until ef. The results suggest that N deficiency could be corrected by fertilizer application up to bv without a yield penalty, because the indeterminate growth habit of linseed enables it to respond rapidly to the relief of N stress. However, linseed should have an adequate N supply during seed-filling, as the plant appears to have limited reserves of N for redistribution to capsules and seeds.