Plant morphology and content of nitrogen, cell wall and lignin at different phenological stages of red clover and yellow sweetclover
1997
Wivstad, M. (SLU, Uppsala (Sweden). Inst. foer Vaextodlingslaera)
The plant morphology and chemical composition of red clover (Trifolium pratense L.) and yellow sweetclover (Melilotus officinalis Lam.) were the focus of this greenhouse experiment. Each species was sampled 8, 14, and 20 weeks after plant emergence. Samples of field-grown red clover and yellow sweetclover were included as references. The leaf proportion of the total plant dry matter (DM) of greenhouse-grown plants decreased with time, from 36 to 22% in red clover and from 46 to 29% in yellow sweetclover. The leaf proportion was smaller for field herbage than for greenhouse plants at similar a phenological stage, mainly owing to differences in stand structure. When all plant parts of both species were compared in the greenhouse, it was found that sweetclover leaves had the highest nitrogen (N) content, 3.5-4.9% of DM, while the sweetclover stems had the lowest, 1.5-1.9% of DM. The N contents of the roots were similar for the two species and increased slightly with time, on average from 2.3 to 2.9% of DM. For both species the root-N content was intermediate between the N contents of the leaves and stems. Cell wall (CW) and lignin contents were higher in sweetclover than in red clover stems. The CW content was lower in roots than in stems except in the first red clover sample. The leaf proportion of above-ground plant material was strongly related to the contents of N, CW and lignin. As these chemical characteristics influence soil N mineralization, it was concluded that determination of plant-part proportions can help to predict the effects of green manure crops.
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