Soil changes in ley-arable experiments

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Abstract
The effects of four five-course and six four-course rotations on some physical and chemical properties of a sandy loam overlying London Clay are reported.Periods under ley increased the water stability of the air-dry soil aggregates, the resistance of moist soil aggregates to simulated raindrops, the rate of drainage under 60 cm. of water tension as measured in the laboratory, decreased the draw-bar pull during ploughing and the force required to crush air-dry aggregates. These effects increased with the number of years under grass.After 2 years of arable cultivation the effect of a 3-year ley on water-stable aggregation was still apparent whereas the effect of a 2-year ley had largely disappeared, and those of a 1-year ley had completely disappeared.A 2-year ley in a five-course ley-arable rotation was sufficient to maintain the total soil nitrogen at about 0·16%. With one year of ley in a four-course rotation a slow decline in nitrogen was found when the initial level was about 0·21%.The rate of CO2 formation in soils of the arable break was proportional to the number of years they had been under ley; the longer the period the greater the volume of CO2 produced.Evidence is presented that fertilizer nitrogen is used most efficiently by cereals growing in soil in good physical condition. This is usually best following a period under grass.

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