Pre-anthesis stem reserve contribution to grain yield was assessed in two spring barley cultivars of contrasting height. It was greatest in the taller, but final grain yields were similar. Partitioning of total reserve capacity to various plant parts showed that the leaf and sheath below the peduncle were most important, followed by stem internodes which had increasing reserve capacity up to internode 4.It is suggested that stem reserves are valuable for yields commonly achieved in U.K. commercial practice.High grain yields were associated with large positive increases in stem dry weight after anthesis. This would indicate that the source capacity to boost yield is more than proportional to that required to fill the grain alone.

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1. A modified capacitance meter used to make rapid non-destructive measurements of growingpasture is briefly described.

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SUMMARYThree spring oil-seed rape cultivars were drilled on five dates during 1979 and 1980. Delayed drilling (1) reduced seed yield, (2) increased the main stem contribution to seed production, and (3) increased the percentage of damaged pods at harvest. The results indicated that cultivars similar to those used in this trial should be drilled between the 3rd week of March and mid-April.

In two experiments, ewes in weeks 1–20 of lactation received either pasture only or pasture plus ad libitum conserved forage. Herbage height was maintained at 3·3–3·4 cm on both treatments by manipulation of stocking rate in the 24 plots (twelve per treatment) used for the experiment with additional ewes and lambs. In experiment 1, silage, which was of lower metabolizable energy (ME) and crude protein (CP) contents than the grazed herbage, was consumed at an average of 375 g dry matter (DM) ewe−1 d−1. In experiment 2 a strawmix, containing (g kg −1 freshweight) 480 g barley straw, 300 g concentrate and 220 g molasses, again with a lower ME and CP content than the grazed herbage, was consumed at an average of 165 g DM ewe −1 d −1. In both experiments ewes not receiving forage lost weight whereas those with forage gained weight and tended to have increased body condition scores. Offering silage or strawmix did not affect lamb liveweight gain or stocking rate.

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S U M M A R YThree pot experiments were performed in unheated glasshouses at the University College of North Wales College Farm, Aber, Gwynedd in 1980-83. Two experiments tested the effects of sowing date and N supply, the third sowing density and nitrogen supply. Extension growth of main-stem leaves was measured by ruler and expressed in thermal time units to allow comparisons between sowing dates. Rate and duration of leaf extension were determined from linear regressions of leaf length against thermal time.Increasing N supply increased leaf extension rate but had no significant effects on leaf extension duration. Leaf extension rate increased with leaf position on the main shoot, but decreased slightly in leaves extending at the time of stem elongation. Leaf extension duration also increased with leaf position on the main shoot and was related to mean temperature during the leaf extension phase. Plants sown in September were able to compensate for lower radiation receipts by having a faster rate and longer duration of leaf extension, by producing larger leaves with a greater specific lamina area and by partitioning a greater proportion of extension growth into lamina and less into sheaths. In plants sown in June, the largest leaf occurred at a lower stem node and leaves emerging later showed a strong response to N. It is suggested that this is attributable to earlier onset of internal competition for assimilates. Variation in leaf extension rate was the main factor influencing variation in final leaf area. There was a strong positive relationship between leaf extension rate and leaf N content.Increasing sowing density increased the area of the first four leaves on the main shoot and decreased that of later leaves, changes mainly associated with changes in leaf extension duration. It is concluded that progress in the modelling of leaf area expansion, light interception and dry matter production requires more information about how sowing date, sowing density and N supply interact to influence crop development and leaf growth.