Patterns of nitrogen mobilization in grain sorghum hybrids and the relationship to grain and dry matter production.
1992
Youngquist J.B. | Maranville J.W.
Results from previous studies on nitrogen uptake and mobilization in sorghum [Sorghum bicolor (L.) Moench] are incomplete and inconclusive. This study examined the influence of genotype and soil N level on plant N accumulation, N remobilization and their relation to dry matter and grain production in sorghum. Five sorghum hybrids were planted with two N fertility treatments at two locations in 1988. Total plant dry matter, leaf dry weight, stem dry weight, and N contents were measured throughout the growing season. Hybrid differences in N and yield parameters and plant N differences due to soil N treatment were detected at anthesis and after. By anthesis, up to 89% of final total plant N had been accumulated depending upon genotype and soil N level. At anthesis, 44-57% of plant N was in the stem and 43-56% was in the leaves. At maturity, 58-68% of total plant N was in the grain, with 14-17% remaining in the stems and 18-25% in leaves. During grain fill, stem and leaf fractions lost from 45-69% of their N content, with stems having a greater loss than leaves. The relative contribution of remobilized N to grain N was greater in the low soil N treatment, although absolute plant N contents were greater in the high soil N treatment. Greater accumulation of N during grain fill was not necessarily associated with higher grain yields. Maintaining production of total dry matter per unit plant N was not a mechanism for increasing yield in the high N treatment. Greater yields in the high N soil in this experiment were due to an increase in productive tillers.
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