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Rothamsted

Alternate Wheat and Fallow

The Alternate Wheat and Fallow experiment was started by Lawes and Gilbert in 1856, on a 0.4 ha site on part of Hoosfield that had received no applications of fertilizers or manures since 1851. The experiment originally had two strips which alternated winter wheat and a bare fallow in successive years. Between 1932 and 1982, a modification was introduced to allow a yearly comparison of a one-year and a three-year fallow but the effects on the yield of the subsequent wheat crop were small and since 1983 the experiment has reverted to the original design.

Since autumn 2015, the whole experiment (both plots) has grown winter wheat, with a small amount of fertilizer N applied in the spring.

Background

No fertilizers or manures are applied but, like most of the other arable experiments, chalk is applied to maintain the soil at about pH 7. Pesticides are also applied when needed. All plots have been combine harvested since 1957. The plot area since 1983 is 0.2 ha, from 1932-1982 it was 0.05 ha.

The wheat cultivar grown has usually been the same as on Broadbalk, and the effects of fallowing on the yield of winter wheat can be roughly estimated by comparing yields from this experiment with continuous, unmanured wheat on Broadbalk (plot 03). In the first 10 years of the experiment the one-year fallow gave an extra 0.6 t ha-1, but over the next 60 years the difference was even smaller (0.14 t ha-1). Since its reversion to the original design in 1983, and with modern cultivars, average yields of the wheat after a one-year fallow have been 1.7 t ha-1. When expressed on the basis of the whole area (i.e. wheat plus fallow), the yield of 0.85 t ha-1 is slightly less than the 1.0 t ha-1 for continuous wheat on Broadbalk.

In 1957 the original plots were divided into half longitudinally, the centre two strips continued in the wheat fallow cycle as before, and the two outer strips were used to study Wheat Bulb Fly. From 1963 to 1966 the cropped plots were subdivided and two different varieties were grown (see Varieties and cropping 1856-present for details). From 1967 the experiment reverted to a single variety.

Since autumn 2015, the whole experiment (both plots) has been sown to winter wheat, the same variety as is grown on Broadbalk. A small amount of N fertilizer (50 kg N ha-1) is applied in spring (mid-April), but to maintain the low soil P and K status, no other fertilizers are applied. No yields or crop samples have been taken since harvest 2015.

It was in this experiment in 1935, that symptoms caused by the fungal pathogen Gibellina cerealis or 'white straw disease' were first recorded in the UK.

For more details, refer to the Key References listed below.

Plot Descriptions and treatments

Data Available

The following data can be extracted using the e-RA Data Extraction Tool:

Grain and straw yields were recorded each year, up to and including harvest 2015. Other data collected include the results of chemical analyses of crops and soils. Physical samples of crops and soils have been preserved in the Rothamsted Sample Archive. For more details please contact the e-RA Curators.

Between 1932 and 1982 each large plot was divided into four to test the effects of one and three year fallows. To allow comparison with previous years, a mean value is also given for each year 1932-1982, indicated as 'M'. Codes are used to indicate the different varieties tested between 1963 and 1967, see Varieties and cropping 1856-present (pdf) for full details.

Key References

2009

1991

1985

1957

1936

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