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The effect of tilth on the emergence of spring oats

Published online by Cambridge University Press:  27 March 2009

R. F. Thow
R. F. Thow
Affiliation:
The Edinburgh School of Agriculture
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Extract

1. A survey of commercial crops of spring oats suggested tilth as a major factor affecting emergence.

2. In field experiments conducted on clay and sandy soils, the surface tilth was regarded as a population of aggregates characterized by size which was analysed by means of a five-point quadrat. A tilth index was calculated from the data thus obtained. Under the rough tilths on the clay soil emergence and tilth were directly related, but on the sandy soil there was an optimum degree of cultivation, the plots with the finest tilth had been over-cultivated and gave a low rate of emergence (Fig. 2).

3. A greenhouse pot experiment examined the effect of a cover above the seed of 21 tilths, of varying proportions of 0·03–0·25 in., 0·25–1·25 in., 1·25–2·25 in. diameter aggregates, the soil below the seed being uniform in all treatments. This confirmed that emergence rates were higher under fine surface tilths than under very rough tilths (Fig. 3). An increase in the proportion of 0·03–0·25 in. fraction increased emergence regularly whereas an increase in the proportion of the 1·25–2·25 in. fraction reduced emergence regularly. The presence of 0·25–1·25 in. aggregates reduced emergence compared with that where 0·03–0·25 in. only were present, but the effect of an increase in the proportion was not regular (Fig. 4).

4. A second greenhouse pot experiment compared the effect of 3 tilths above the seed and 2 irrigation treatments. The low emergence rate (58%) caused by a very rough tilth under restricted irrigation was raised to 86% by liberal irrigation.

5. From the evidence of both pot experiments it is postulated that a covering tilth above the seed of 25% or more by weight of fine soil (0·03–0·25 in.) and not more than 40% of coarse aggregates (1·25–2·25 in.) will permit a rate of emergence of at least 80%.

6. As the fine covering tilths in the pot experiment gave high rates of emergence as compared with rougher tilths, it is suggested that the low rate of emergence, on the sandy soil field experiments, was due to a lack of soil moisture induced by over-cultivation.

Type
Research Article
Information
The Journal of Agricultural Science , Volume 60 , Issue 3 , May 1963 , pp. 291 - 295
Copyright
Copyright © Cambridge University Press 1963

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References

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